Homebrew PCBs

I had this idea about seven years ago. But at that time the Laser Diodes
of 405nm were impossible to obtain (USD$4000).  Since last year, I have
taken this idea again, because now one can buy those laser diodes around
USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys
experimenting with this, but I have not see the results. Also I read
about a french engineer who made some experiments with UV LEDs coupled
with a fibre optic. I have a Polish paper which expose the use of this
idea to get 50um (2 mils) clear cut beatiful traces, but they use very
expensive optics ( telecentric lenses, glavos and others things which
are too costly for the DIYer ).

Now I struggling with optics.  When I get some control of the LASER beam
waist, I gonna put my laser module in a CNC engraver.

There are anyone working on that in this group?

I think you need a 3W UV laser to ablate copper.

I saw a UV laser at Fabtech with galvos in an enclosed case.  No moving
parts.  It was sweet.  They guy put a pen in and typed up my name and it
engraved it in about 3 seconds.  Super clean not like CO2 cuts.  I can't
remember if the machine was $30,000 or if that was just the diode without
the galvos.

http://www.lpkfusa.com/microline/pl_u.htm
uses 3W UV laser does 1mil traces/1mil spacing
Costs $220,000


http://www.lpkfusa.com/microline/pl_s.htm
uses 10W YAG laser
costs $120,000

If you can get the UV to fire safely, I sell you a XY overhead complete
gantry for ~$1200 with motors and control card.  This gantry is currently
used on my 50W CO2 laser (which copper doesn't absorb).






On Thu, Nov 12, 2009 at 8:38 AM, lmri2071 <lmri2071@...> wrote:

>
>
>
> I had this idea about seven years ago. But at that time the Laser Diodes
> of 405nm were impossible to obtain (USD$4000). Since last year, I have
> taken this idea again, because now one can buy those laser diodes around
> USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys
> experimenting with this, but I have not see the results. Also I read
> about a french engineer who made some experiments with UV LEDs coupled
> with a fibre optic. I have a Polish paper which expose the use of this
> idea to get 50um (2 mils) clear cut beatiful traces, but they use very
> expensive optics ( telecentric lenses, glavos and others things which
> are too costly for the DIYer ).
>
> Now I struggling with optics. When I get some control of the LASER beam
> waist, I gonna put my laser module in a CNC engraver.
>
> There are anyone working on that in this group?
>
> 
>


[Non-text portions of this message have been removed]

I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 
Volkan

--- On Thu, 11/12/09, lmri2071 <lmri2071@...> wrote:

From: lmri2071 <lmri2071@...>
Subject: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Thursday, November 12, 2009, 8:38 AM







 



  


    
      
      
      

I had this idea about seven years ago. But at that time the Laser Diodes

of 405nm were impossible to obtain (USD$4000).  Since last year, I have

taken this idea again, because now one can buy those laser diodes around

USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys

experimenting with this, but I have not see the results. Also I read

about a french engineer who made some experiments with UV LEDs coupled

with a fibre optic. I have a Polish paper which expose the use of this

idea to get 50um (2 mils) clear cut beatiful traces, but they use very

expensive optics ( telecentric lenses, glavos and others things which

are too costly for the DIYer ).



Now I struggling with optics.  When I get some control of the LASER beam

waist, I gonna put my laser module in a CNC engraver.



There are anyone working on that in this group?





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

Can your laser ablate the copper or just hardens the resist?

If the former, I need to buy some blue lasers to try.
On Thu, Nov 12, 2009 at 2:46 PM, Volkan Sahin <v_sahin@...> wrote:

>
>
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode.
> Without complicated optics I can get ~3 mil trace width/space. Currently,
> I'm using  Dichromated PVA  based homemade photoresist.  The problem is
> without  polygon mirror scanner, it is very slow but result is impressive.
> The exposure time required for  1.5 mil spot is ~20 microseconds.
> Volkan
>
> --- On Thu, 11/12/09, lmri2071 <lmri2071@... <lmri2071%40yahoo.com>>
> wrote:
>
> From: lmri2071 <lmri2071@... <lmri2071%40yahoo.com>>
> Subject: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
> To: Homebrew_PCBs@yahoogroups.com <Homebrew_PCBs%40yahoogroups.com>
> Date: Thursday, November 12, 2009, 8:38 AM
>
>
>
>
> I had this idea about seven years ago. But at that time the Laser Diodes
>
> of 405nm were impossible to obtain (USD$4000). Since last year, I have
>
> taken this idea again, because now one can buy those laser diodes around
>
> USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys
>
> experimenting with this, but I have not see the results. Also I read
>
> about a french engineer who made some experiments with UV LEDs coupled
>
> with a fibre optic. I have a Polish paper which expose the use of this
>
> idea to get 50um (2 mils) clear cut beatiful traces, but they use very
>
> expensive optics ( telecentric lenses, glavos and others things which
>
> are too costly for the DIYer ).
>
> Now I struggling with optics. When I get some control of the LASER beam
>
> waist, I gonna put my laser module in a CNC engraver.
>
> There are anyone working on that in this group?
>
> [Non-text portions of this message have been removed]
>
>  
>


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, Volkan Sahin <v_sahin@...> wrote:
>
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 
> Volkan
> 

I assume that you are doing UV exposure as opposed to ablation as mentioned in the earlier post.

It's used for UV exposure. 

--- On Thu, 11/12/09, javaguy11111 <javaguy11111@...> wrote:

From: javaguy11111 <javaguy11111@...>
Subject: [Homebrew_PCBs] Re: Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Thursday, November 12, 2009, 3:17 PM







 



  


    
      
      
      --- In Homebrew_PCBs@ yahoogroups. com, Volkan Sahin <v_sahin@... > wrote:

>

> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 

> Volkan

> 



I assume that you are doing UV exposure as opposed to ablation as mentioned in the earlier post. 





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

Henry Liu wrote: 
> I sell you a XY overhead complete gantry for ~$1200 

Isn't there some rule which limits selling/marketing messages to one per
month?



Volkan Sahin wrote:
> I'm using  Dichromated PVA  based homemade photoresist.  

http://www.htp.ch/lib/pdf/Liquid%20resist%20for%20PCM.pdf
Once i found this, useful for who like me don't know really much about
photoresists (most interesting after page 4).

Hello, Volkan.

Looks like you have your fingers in several pots (homebrew pcbs, direct print resist, homemade photo resist).  I love it.

Are you willing to tell us more about your formula and processing for the homemade dichromated PVA resist?  A friend (30 years ago) did some silkscreen work using (IIRC) Elmer's glue, which is a PVA product.  What else is involved?  Or a pointer to where you have already told everyone and I wasn't watching. :)

Thanks much,
Donald.

----- Original Message -----
From: "Volkan Sahin" <v_sahin@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, November 12, 2009 5:46:45 PM GMT -05:00 US/Canada Eastern
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes

I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 
Volkan

--- On Thu, 11/12/09, lmri2071 <lmri2071@...> wrote:

From: lmri2071 <lmri2071@...>
Subject: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Thursday, November 12, 2009, 8:38 AM







 



  


    
      
      
      

I had this idea about seven years ago. But at that time the Laser Diodes

of 405nm were impossible to obtain (USD$4000).  Since last year, I have

taken this idea again, because now one can buy those laser diodes around

USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys

experimenting with this, but I have not see the results. Also I read

about a french engineer who made some experiments with UV LEDs coupled

with a fibre optic. I have a Polish paper which expose the use of this

idea to get 50um (2 mils) clear cut beatiful traces, but they use very

expensive optics ( telecentric lenses, glavos and others things which

are too costly for the DIYer ).



Now I struggling with optics.  When I get some control of the LASER beam

waist, I gonna put my laser module in a CNC engraver.



There are anyone working on that in this group?





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]



------------------------------------

Be sure to visit the group home and check for new Links, Files, and Photos:
http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links

Excellent news, I thought that Bichromate photoresist needs a high energy density. I gonna try with dry films for etch resist and solder mask with a LASER diode of 65 mW to 85 mW. They are  sensitive between 350nm to 420nm wavelength and have an energy density between 25 to 60 mJ/cm2 (Think & Tinker Ltd.). At the begining I though to modify an old LASER printer (replace the IR diode) and try. Is good to know that you get 3 mils with your own implementation.

Lucho

--- In Homebrew_PCBs@yahoogroups.com, Volkan Sahin <v_sahin@...> wrote:

>
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 
> Volkan
> 
> --- On Thu, 11/12/09, lmri2071 <lmri2071@...> wrote:
> 
> From: lmri2071 <lmri2071@...>
> Subject: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
> To: Homebrew_PCBs@yahoogroups.com
> Date: Thursday, November 12, 2009, 8:38 AM
> 
> 
> 
> 
> 
> 
> 
> Â 
> 
> 
> 
>   
> 
> 
>     
>       
>       
>       
> 
> I had this idea about seven years ago. But at that time the Laser Diodes
> 
> of 405nm were impossible to obtain (USD$4000).  Since last year, I have
> 
> taken this idea again, because now one can buy those laser diodes around
> 
> USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys
> 
> experimenting with this, but I have not see the results. Also I read
> 
> about a french engineer who made some experiments with UV LEDs coupled
> 
> with a fibre optic. I have a Polish paper which expose the use of this
> 
> idea to get 50um (2 mils) clear cut beatiful traces, but they use very
> 
> expensive optics ( telecentric lenses, glavos and others things which
> 
> are too costly for the DIYer ).
> 
> 
> 
> Now I struggling with optics.  When I get some control of the LASER beam
> 
> waist, I gonna put my laser module in a CNC engraver.
> 
> 
> 
> There are anyone working on that in this group?
> 
> 
> 
> 
> 
>     
>      
> 
>     
>     
> 
> 
>  
> 
> 
> 
>   
> 
> 
> 
> 
> 
> 
>       
> 
> [Non-text portions of this message have been removed]
>

The intention is to polimerize/depolimerize the etchresist and solder mask.  In the industrie is know as LDI (Laser Direct Imaging). Before the blue-violet LASER diodes the industrie use Argon and Kripton LASERS.  But being gas LASERs, the method of modulation was very complex and costly.  Working with a 405nm LASER diode is far simpler.

Lucho

--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:

>
> I think you need a 3W UV laser to ablate copper.
> 
> I saw a UV laser at Fabtech with galvos in an enclosed case.  No moving
> parts.  It was sweet.  They guy put a pen in and typed up my name and it
> engraved it in about 3 seconds.  Super clean not like CO2 cuts.  I can't
> remember if the machine was $30,000 or if that was just the diode without
> the galvos.
> 
> http://www.lpkfusa.com/microline/pl_u.htm
> uses 3W UV laser does 1mil traces/1mil spacing
> Costs $220,000
> 
> 
> http://www.lpkfusa.com/microline/pl_s.htm
> uses 10W YAG laser
> costs $120,000
> 
> If you can get the UV to fire safely, I sell you a XY overhead complete
> gantry for ~$1200 with motors and control card.  This gantry is currently
> used on my 50W CO2 laser (which copper doesn't absorb).
> 
> 
> 
> 
> 
> 
> On Thu, Nov 12, 2009 at 8:38 AM, lmri2071 <lmri2071@...> wrote:
> 
> >
> >
> >
> > I had this idea about seven years ago. But at that time the Laser Diodes
> > of 405nm were impossible to obtain (USD$4000). Since last year, I have
> > taken this idea again, because now one can buy those laser diodes around
> > USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys
> > experimenting with this, but I have not see the results. Also I read
> > about a french engineer who made some experiments with UV LEDs coupled
> > with a fibre optic. I have a Polish paper which expose the use of this
> > idea to get 50um (2 mils) clear cut beatiful traces, but they use very
> > expensive optics ( telecentric lenses, glavos and others things which
> > are too costly for the DIYer ).
> >
> > Now I struggling with optics. When I get some control of the LASER beam
> > waist, I gonna put my laser module in a CNC engraver.
> >
> > There are anyone working on that in this group?
> >
> > 
> >
> 
> 
> [Non-text portions of this message have been removed]
>

Hello Donald,

There is no magic for the formula check http://www.holowiki.com/index.php/Dichromated_Gelatin_Chemistry they have detailed information on it. I'm using PVA instead of gelatin. The problem is you need to be careful using dichromate, it is not environmentally safe disposing requires care. I'm always keeping water used for development in separate container for  recycling/disposal center.
I've decided to switch another photoresist which is environmentally safe, they're also selling it on e-bay  AQ 3000 Waterborne Photoresist,  it is easier and much more sensitive than DCG.

Volkan


--- On Thu, 11/12/09, Donald H Locker <dhlocker@...t> wrote:

From: Donald H Locker <dhlocker@...>
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Date: Thursday, November 12, 2009, 6:09 PM







 



  


    
      
      
      Hello, Volkan.



Looks like you have your fingers in several pots (homebrew pcbs, direct print resist, homemade photo resist).  I love it.



Are you willing to tell us more about your formula and processing for the homemade dichromated PVA resist?  A friend (30 years ago) did some silkscreen work using (IIRC) Elmer's glue, which is a PVA product.  What else is involved?  Or a pointer to where you have already told everyone and I wasn't watching. :)



Thanks much,

Donald.



----- Original Message -----

From: "Volkan Sahin" <v_sahin@yahoo. com>

To: "Homebrew PCBs" <Homebrew_PCBs@ yahoogroups. com>

Sent: Thursday, November 12, 2009 5:46:45 PM GMT -05:00 US/Canada Eastern

Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes



I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 

Volkan



--- On Thu, 11/12/09, lmri2071 <lmri2071@yahoo. com> wrote:



From: lmri2071 <lmri2071@yahoo. com>

Subject: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes

To: Homebrew_PCBs@ yahoogroups. com

Date: Thursday, November 12, 2009, 8:38 AM



 



I had this idea about seven years ago. But at that time the Laser Diodes



of 405nm were impossible to obtain (USD$4000).  Since last year, I have



taken this idea again, because now one can buy those laser diodes around



USD$40 (85mW) in eBay. I saw in web (youtube) some germans guys



experimenting with this, but I have not see the results. Also I read



about a french engineer who made some experiments with UV LEDs coupled



with a fibre optic. I have a Polish paper which expose the use of this



idea to get 50um (2 mils) clear cut beatiful traces, but they use very



expensive optics ( telecentric lenses, glavos and others things which



are too costly for the DIYer ).



Now I struggling with optics.  When I get some control of the LASER beam



waist, I gonna put my laser module in a CNC engraver.



There are anyone working on that in this group?



[Non-text portions of this message have been removed]



------------ --------- --------- ------



Be sure to visit the group home and check for new Links, Files, and Photos:

http://groups. yahoo.com/ group/Homebrew_ PCBsYahoo! Groups Links





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

Volkan Sahin wrote:
>  
> 
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. 
> Without complicated optics I can get ~3 mil trace width/space. 
> Currently, I'm using  Dichromated PVA  based homemade photoresist.  The 
> problem is without  polygon mirror scanner, it is very slow but result 
> is impressive. The exposure time required for  1.5 mil spot is ~20 
> microseconds.
> Volkan
> 

What's wrong with using dry film photoresist ?
Its relatively cheap (under 10% cost of FR4 PCB material per unit area) 
easy to apply, fairly sensitive to 405nm, highly uniform and the ability 
to tent holes for the PTH panel plating method.

How are you positioning the laser ?
Would it be difficult to use parts off an laser printer to make a 
polygon mirror scanner. In that case only 1 axis movement is needed for 
the PCB.  My inkjet printer is currently the limiting factor for 
line/space widths, although 0.2mm (8mil) are quite reliable and adequate.

Thank you for the link, Volkan.

In my occasional searches over the last few years (mostly for terms like "homemade photoresist") I hadn't found that.  Excellent information.  I'll also check on the AQ 3000; I've heard it mentioned (probably on this group) recently.

Donald.

----- Original Message -----
From: "Volkan Sahin" <v_sahin@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, November 13, 2009 1:10:19 AM GMT -05:00 US/Canada Eastern
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes

Hello Donald,

There is no magic for the formula check http://www.holowiki.com/index.php/Dichromated_Gelatin_Chemistry they have detailed information on it. I'm using PVA instead of gelatin. The problem is you need to be careful using dichromate, it is not environmentally safe disposing requires care. I'm always keeping water used for development in separate container for  recycling/disposal center.
I've decided to switch another photoresist which is environmentally safe, they're also selling it on e-bay  AQ 3000 Waterborne Photoresist,  it is easier and much more sensitive than DCG.

Volkan


--- On Thu, 11/12/09, Donald H Locker <dhlocker@...> wrote:

From: Donald H Locker <dhlocker@...>
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Date: Thursday, November 12, 2009, 6:09 PM

Hello, Volkan.

Looks like you have your fingers in several pots (homebrew pcbs, direct print resist, homemade photo resist).  I love it.

Are you willing to tell us more about your formula and processing for the homemade dichromated PVA resist?  A friend (30 years ago) did some silkscreen work using (IIRC) Elmer's glue, which is a PVA product.  What else is involved?  Or a pointer to where you have already told everyone and I wasn't watching. :)

Thanks much,
Donald.

----- Original Message -----

From: "Volkan Sahin" <v_sahin@yahoo. com>

To: "Homebrew PCBs" <Homebrew_PCBs@ yahoogroups. com>

Sent: Thursday, November 12, 2009 5:46:45 PM GMT -05:00 US/Canada Eastern

Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes

I've a working prototype. I'm using 150mw 405nm blue ray laser diode. Without complicated optics I can get ~3 mil trace width/space. Currently, I'm using  Dichromated PVA  based homemade photoresist.  The problem is without  polygon mirror scanner, it is very slow but result is impressive. The exposure time required for  1.5 mil spot is ~20 microseconds. 

Volkan


[snip]

There is nothing wrong with dryfilm. Only side effect can be its thickness. 
It is thicker than liquid photoresist. I've used dichromated PVA in order to avoid shelf life limitation. Whenever you need photoresist you can mix PVA with dichromate and it is ready, the problem is dichromate is not an environmentally safe chemical. Now I'll try AQ 3000. 
I used dryfilm before and faced a lot of problems to protect PTH holes but it was ~8 years before may be new ones are better.
I added laser to the side of inkjet head and I'm using raster scanning method to expose photoresist. 
I've the same idea to use polygon mirrors of a old laser printer. I've one Brother printer which has an aluminum mirror (most of them have a copper or gold plated mirror on  aluminum because of IR laser) and plastic lenses it seems it is possible to use with blue laser. I did some rough measurements and I saw that on optical path I'm loosing ~30% of the power most of it is because of diagonal mirrors because of that I left it for a future project.    

Volkan

--- On Fri, 11/13/09, Adam Seychell <a_seychell@...> wrote:

From: Adam Seychell <a_seychell@...>
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Friday, November 13, 2009, 2:26 AM







 



  


    
      
      
      Volkan Sahin wrote:

>  

> 

> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. 

> Without complicated optics I can get ~3 mil trace width/space. 

> Currently, I'm using  Dichromated PVA  based homemade photoresist.  The 

> problem is without  polygon mirror scanner, it is very slow but result 

> is impressive. The exposure time required for  1.5 mil spot is ~20 

> microseconds.

> Volkan

> 



What's wrong with using dry film photoresist ?

Its relatively cheap (under 10% cost of FR4 PCB material per unit area) 

easy to apply, fairly sensitive to 405nm, highly uniform and the ability 

to tent holes for the PTH panel plating method.



How are you positioning the laser ?

Would it be difficult to use parts off an laser printer to make a 

polygon mirror scanner. In that case only 1 axis movement is needed for 

the PCB.  My inkjet printer is currently the limiting factor for 

line/space widths, although 0.2mm (8mil) are quite reliable and adequate.





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

I had the same idea last spring and purchased a 405nm laser diode with holder/lense and some Riston film off ebay.  I added a heat sink to the holder and have driven it up to 110ma.  At that power level it will burn through paper, so I have no doubts that it should harden the photo resist. I did some initial crude calculations based on the Riston data and estimated diode power that led me to believe it would be possible to write a .001" dia spot at 80"/sec.

My initial plan is not to raster scan the board but to vector draw the pattern using my Bridgeport mill that is currently being converted to CNC. I will need to write some code to convert the Gerber photo plot file to a G-Code file to drive the mill.  These files are very similar, the Gerber format being an offshoot of the G-code format. Since I plann on using a fixed spot size, wide traces will need multiple passes as will donuts etc. This all has to be coded in the conversion program.  

Currently I am working on the mill's CNC conversion and have not done any testing on the direct exposure part of the project. It will be a couple of months before the mill is ready for PCB testing.

Issues to be resolved:
1.Is the exposure of photo resist linear ie. is high power UV for a short time the same as low power UV for a longer time.

2.Code to make multiple passes for trace and shape widths from the point gerber data.

3.How to get a .001" dia round spot.  The laser diode output is not round. How to measure the spot dia.

4.How long will it take to expose a 3'x5" board?

Craig

For your problem to convert to Gcode from gerber, there are three ways:
-pcb-gcode (works ok but in Eagle)
-export to DXF then into Cam package like LazyCAM with Mach3
-some commerical package made to CNC mill out pcbs from gerbers (forget the
name, was on pcb-gcode group)

On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@...> wrote:

>
>
> I had the same idea last spring and purchased a 405nm laser diode with
> holder/lense and some Riston film off ebay. I added a heat sink to the
> holder and have driven it up to 110ma. At that power level it will burn
> through paper, so I have no doubts that it should harden the photo resist. I
> did some initial crude calculations based on the Riston data and estimated
> diode power that led me to believe it would be possible to write a .001" dia
> spot at 80"/sec.
>
> My initial plan is not to raster scan the board but to vector draw the
> pattern using my Bridgeport mill that is currently being converted to CNC. I
> will need to write some code to convert the Gerber photo plot file to a
> G-Code file to drive the mill. These files are very similar, the Gerber
> format being an offshoot of the G-code format. Since I plann on using a
> fixed spot size, wide traces will need multiple passes as will donuts etc.
> This all has to be coded in the conversion program.
>
> Currently I am working on the mill's CNC conversion and have not done any
> testing on the direct exposure part of the project. It will be a couple of
> months before the mill is ready for PCB testing.
>
> Issues to be resolved:
> 1.Is the exposure of photo resist linear ie. is high power UV for a short
> time the same as low power UV for a longer time.
>
> 2.Code to make multiple passes for trace and shape widths from the point
> gerber data.
>
> 3.How to get a .001" dia round spot. The laser diode output is not round.
> How to measure the spot dia.
>
> 4.How long will it take to expose a 3'x5" board?
>
> Craig
>
>
>  
>


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, "lmri2071" <lmri2071@...> wrote:
>
> 
> I had this idea about seven years ago. But at that time the Laser Diodes
> of 405nm were impossible to obtain (USD$4000).  

...

I have been experimenting with ammonium di-(or bi- same thing) chromate and gelatin emulsions off and on for about a year and a half.  Though I don't know the chemistry very well, it seems that potassium, sodium or ammonium dichromate all have the ability to crosslink (harden) any number of organic materials when exposed to light.  

I use fish-gelatin (aka fish-glue) which was once used to make the masks in TV picture tubes and other chemical milling processes.  It is a kind of gelatin made from fish from Northern oceans. Due to its amino acid composition remains liquid at room temperature.  I have no special reason to think that it is necessary.  It wasn't terribly expensive, but then neither is Knorr's at the grocer's.

The Dichromates are indeed hazardous, as is any form of hexavalent chromium.  Much of the negative experience with it comes from the plating industry, I believe.  

That said, I worked with it a lot during my squandered youth, experimenting with gum-bichromate printing of photos.  I gave that up one day when I inhaled enough of the powder to give me a headache and make me nauseous.  I'm much more careful now.

The induction period for most chemical carcinogens is hopefully less than twenty years.  Now forty years on I believe that something else will probably get me first.

-- Dave

I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.

Its the aperture definitions that cause the problem. The origional photo plotters used an aperture wheel to project the correct spot size for the trace width and donut pads. But with the laser I will need to write macros to draw these from a single .001" dia spot. I took a look at Diptrace's Gerber output and currently they don't do anything exotic just x-y moves and apeture settings. For me to write and 8mill wide trace I will have to do the xy move 8 times with .001 offsets between writes. If this works out to be too slow I may have to increase the spot size somewhat. Would be nice to figure out how to have several different spot sizes.  I guess one could use multiple laser diodes and just select the best one for the task at hand. It would be no problem selecting the correct diode in the G-code.


Craig 

--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:

>
> For your problem to convert to Gcode from gerber, there are three ways:
> -pcb-gcode (works ok but in Eagle)
> -export to DXF then into Cam package like LazyCAM with Mach3
> -some commerical package made to CNC mill out pcbs from gerbers (forget the
> name, was on pcb-gcode group)
> 
> On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@...> wrote:
> 
> >
> >
> > I had the same idea last spring and purchased a 405nm laser diode with
> > holder/lense and some Riston film off ebay. I added a heat sink to the
> > holder and have driven it up to 110ma. At that power level it will burn
> > through paper, so I have no doubts that it should harden the photo resist. I
> > did some initial crude calculations based on the Riston data and estimated
> > diode power that led me to believe it would be possible to write a .001" dia
> > spot at 80"/sec.
> >
> > My initial plan is not to raster scan the board but to vector draw the
> > pattern using my Bridgeport mill that is currently being converted to CNC. I
> > will need to write some code to convert the Gerber photo plot file to a
> > G-Code file to drive the mill. These files are very similar, the Gerber
> > format being an offshoot of the G-code format. Since I plann on using a
> > fixed spot size, wide traces will need multiple passes as will donuts etc.
> > This all has to be coded in the conversion program.
> >
> > Currently I am working on the mill's CNC conversion and have not done any
> > testing on the direct exposure part of the project. It will be a couple of
> > months before the mill is ready for PCB testing.
> >
> > Issues to be resolved:
> > 1.Is the exposure of photo resist linear ie. is high power UV for a short
> > time the same as low power UV for a longer time.
> >
> > 2.Code to make multiple passes for trace and shape widths from the point
> > gerber data.
> >
> > 3.How to get a .001" dia round spot. The laser diode output is not round.
> > How to measure the spot dia.
> >
> > 4.How long will it take to expose a 3'x5" board?
> >
> > Craig
> >
> >
> >  
> >
> 
> 
> [Non-text portions of this message have been removed]
>

designer_craig wrote:
> 
> Issues to be resolved:
> 1.Is the exposure of photo resist linear ie. is high power UV for a 
> short time the same as low power UV for a longer time.

No, but I think if the intensity causes polymerisation under 30 seconds 
or so then it is linear. (i.e exposure time = 1/intensity).
I discovered this when experimenting with UV LEDs, and noticed that if 
the intensity was below a certain level then no amount of exposure time 
(exampled > 1 day) would polymerise. It seemed photo polymerisation 
needed to be under 3~5 minutes or it just didn't happen. My guess is a 
slow side reaction happening during exposure that mitigates photo 
sensitivity. Maybe oxygen diffusion through the mylar film.


> 2.Code to make multiple passes for trace and shape widths from the point 
> gerber data.
> 
> 3.How to get a .001" dia round spot. The laser diode output is not 
> round. How to measure the spot dia.

microscope slide and a microscope. Or better is expose point on 
photoresist and develop, then view photoresist under microscope.

> 
> 4.How long will it take to expose a 3'x5" board?
> 

Assuming a 60mj/cm^2 exposure requirement, and 85 mW source then your 
7.5*12.5cm = 93cm^2 PCB will take  60/85*93 = 65 seconds.

I think it'd be way less work to just export gerber as BMP and raster scan.

Mach3 has raster scan capability from a bmp.

Easy solution.
On Fri, Nov 13, 2009 at 12:21 PM, designer_craig <cs6061@...> wrote:

>
>
> I looked into a couple of these but I believe they are for island milling.
> Converting the xy moves from the gerber to the G-code is the easy part the
> files are almost exactly the same syntax.
>
> Its the aperture definitions that cause the problem. The origional photo
> plotters used an aperture wheel to project the correct spot size for the
> trace width and donut pads. But with the laser I will need to write macros
> to draw these from a single .001" dia spot. I took a look at Diptrace's
> Gerber output and currently they don't do anything exotic just x-y moves and
> apeture settings. For me to write and 8mill wide trace I will have to do the
> xy move 8 times with .001 offsets between writes. If this works out to be
> too slow I may have to increase the spot size somewhat. Would be nice to
> figure out how to have several different spot sizes. I guess one could use
> multiple laser diodes and just select the best one for the task at hand. It
> would be no problem selecting the correct diode in the G-code.
>
> Craig
>
> --- In Homebrew_PCBs@yahoogroups.com <Homebrew_PCBs%40yahoogroups.com>,
> Henry Liu <henryjliu@...> wrote:
> >
> > For your problem to convert to Gcode from gerber, there are three ways:
> > -pcb-gcode (works ok but in Eagle)
> > -export to DXF then into Cam package like LazyCAM with Mach3
> > -some commerical package made to CNC mill out pcbs from gerbers (forget
> the
> > name, was on pcb-gcode group)
> >
>  > On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@...> wrote:
> >
> > >
> > >
> > > I had the same idea last spring and purchased a 405nm laser diode with
> > > holder/lense and some Riston film off ebay. I added a heat sink to the
> > > holder and have driven it up to 110ma. At that power level it will burn
> > > through paper, so I have no doubts that it should harden the photo
> resist. I
> > > did some initial crude calculations based on the Riston data and
> estimated
> > > diode power that led me to believe it would be possible to write a
> .001" dia
> > > spot at 80"/sec.
> > >
> > > My initial plan is not to raster scan the board but to vector draw the
> > > pattern using my Bridgeport mill that is currently being converted to
> CNC. I
> > > will need to write some code to convert the Gerber photo plot file to a
> > > G-Code file to drive the mill. These files are very similar, the Gerber
> > > format being an offshoot of the G-code format. Since I plann on using a
> > > fixed spot size, wide traces will need multiple passes as will donuts
> etc.
> > > This all has to be coded in the conversion program.
> > >
> > > Currently I am working on the mill's CNC conversion and have not done
> any
> > > testing on the direct exposure part of the project. It will be a couple
> of
> > > months before the mill is ready for PCB testing.
> > >
> > > Issues to be resolved:
> > > 1.Is the exposure of photo resist linear ie. is high power UV for a
> short
> > > time the same as low power UV for a longer time.
> > >
> > > 2.Code to make multiple passes for trace and shape widths from the
> point
> > > gerber data.
> > >
> > > 3.How to get a .001" dia round spot. The laser diode output is not
> round.
> > > How to measure the spot dia.
> > >
> > > 4.How long will it take to expose a 3'x5" board?
> > >
> > > Craig
> > >
> > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>  
>


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, Volkan Sahin <v_sahin@...> wrote:
>
> There is nothing wrong with dryfilm. Only side effect can be its thickness. 
> It is thicker than liquid photoresist. I've used dichromated PVA in order to avoid shelf life limitation. Whenever you need photoresist you can mix PVA with dichromate and it is ready, the problem is dichromate is not an environmentally safe chemical. Now I'll try AQ 3000. 
> I used dryfilm before and faced a lot of problems to protect PTH holes but it was ~8 years before may be new ones are better.
> I added laser to the side of inkjet head and I'm using raster scanning method to expose photoresist. 
> I've the same idea to use polygon mirrors of a old laser printer. I've one Brother printer which has an aluminum mirror (most of them have a copper or gold plated mirror on  aluminum because of IR laser) and plastic lenses it seems it is possible to use with blue laser. I did some rough measurements and I saw that on optical path I'm loosing ~30% of the power most of it is because of diagonal mirrors because of that I left it for a future project. 

...

One difficulty that I have worried about using diode lasers is focusing and power measurement.  I don't have any tools that are specifically useful for this.  Besides not wanting to stare at a focused UV laser spot while doing adjustments, at 405 nm a lot of materials (including the laser potting) begin to fluoresce and emit visible wavelengths in random directions.

What do you use?

-- Dave

--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
>
> I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
> 

I wonder if instead of trying to do cartesian scans, put the board on some sort of a spinning disk and run the laser in a radial direction or a polar scan. Basically what is done on a DVD writer. You could keep the .001 spot size and just spiral in. 
That way you are not wasting time with a bunch of stop and start motion. May be easier to construct as well.

Henry,
I will have to look at the bmp to raster path.  I haven't played with Mach all that much so I don't know how it imports a raster.  Do you run the raster throuhg LazyCam to generate the G-Code for Mach or does Mach import a raster file directly?

What I can't do is have the mill write a raster that would be way too slow and hard on the mill. 

Craig

--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:

>
> I think it'd be way less work to just export gerber as BMP and raster scan.
> 
> Mach3 has raster scan capability from a bmp.
> 
> Easy solution.
> On Fri, Nov 13, 2009 at 12:21 PM, designer_craig <cs6061@...> wrote:
> 
> >
> >

The tricky bit is keeping the exposure times reasonably equal. The disk 
would have to speed up as the laser approaches the center line. Nice 
idea though...

Les

javaguy11111 wrote:

> 
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:
>> I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
>>
> 
> I wonder if instead of trying to do cartesian scans, put the board on some sort of a spinning disk and run the laser in a radial direction or a polar scan. Basically what is done on a DVD writer. You could keep the .001 spot size and just spiral in. 
> That way you are not wasting time with a bunch of stop and start motion. May be easier to construct as well.

Volkan Sahin wrote:
>  

> I added laser to the side of inkjet head and I'm using raster scanning 
> method to expose photoresist.
> I've the same idea to use polygon mirrors of a old laser printer. I've 
> one Brother printer which has an aluminum mirror (most of them have a 
> copper or gold plated mirror on  aluminum because of IR laser) and 
> plastic lenses it seems it is possible to use with blue laser. I did 
> some rough measurements and I saw that on optical path I'm loosing ~30% 
> of the power most of it is because of diagonal mirrors because of that I 
> left it for a future project.   
> 

The polygon mirror concept sounds more difficult to implement.
How about a large diameter disc with a laser diode mounted on the 
perimeter. The PCB moves linear to the disc. Software would compensate 
for uniform exposure energy.

Assume that:

Resolution	= 0.005cm (50um)
Disc diameter 	= 15cm
Energy 		= 60mj/cm^2
Laser power 	= 85mW

Then

maximum disc RPM
	= 60 * 1cm/0.005cm / (60/85 * 15*1)
	= 1133

1000 RPM sounds reasonable.

Hello Dave,
There are  some  poor man's method for the power measurement check Sam's Laser, so many information exist. I'm always using goggles during tests. Here is the trick for the focus adjustment, print on  thermal fax paper and check it under microscope.
 
Volkan
 

--- On Fri, 11/13/09, pork_u_pine2000 <wittend@...> wrote:

From: pork_u_pine2000 <wittend@...>
Subject: [Homebrew_PCBs] Re: Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Friday, November 13, 2009, 12:31 PM







 



  


    
      
      
      



--- In Homebrew_PCBs@ yahoogroups. com, Volkan Sahin <v_sahin@... > wrote:

>

> There is nothing wrong with dryfilm. Only side effect can be its thickness. 

> It is thicker than liquid photoresist. I've used dichromated PVA in order to avoid shelf life limitation. Whenever you need photoresist you can mix PVA with dichromate and it is ready, the problem is dichromate is not an environmentally safe chemical. Now I'll try AQ 3000. 

> I used dryfilm before and faced a lot of problems to protect PTH holes but it was ~8 years before may be new ones are better.

> I added laser to the side of inkjet head and I'm using raster scanning method to expose photoresist. 

> I've the same idea to use polygon mirrors of a old laser printer. I've one Brother printer which has an aluminum mirror (most of them have a copper or gold plated mirror on  aluminum because of IR laser) and plastic lenses it seems it is possible to use with blue laser. I did some rough measurements and I saw that on optical path I'm loosing ~30% of the power most of it is because of diagonal mirrors because of that I left it for a future project. 



...



One difficulty that I have worried about using diode lasers is focusing and power measurement.  I don't have any tools that are specifically useful for this.  Besides not wanting to stare at a focused UV laser spot while doing adjustments, at 405 nm a lot of materials (including the laser potting) begin to fluoresce and emit visible wavelengths in random directions.



What do you use?



-- Dave





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

That's a great idea.  For small boards possilby a CD drive hack would do. Would take some code to convert the cartesian data to polar data.

One could possible mount several diodes on the radial lead screw to write multiple sections at once to speed up the process.

Another one I though of a while back was to use something like a DLP projector with a UV source. But that gets complex.

Craig

--- In Homebrew_PCBs@yahoogroups.com, "javaguy11111" <javaguy11111@...> wrote:

>
> 
> 
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@> wrote:
> >
> > I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
> > 
> 
> I wonder if instead of trying to do cartesian scans, put the board on some sort of a spinning disk and run the laser in a radial direction or a polar scan. Basically what is done on a DVD writer. You could keep the .001 spot size and just spiral in. 
> That way you are not wasting time with a bunch of stop and start motion. May be easier to construct as well.
>

Good idea. How to make reliable electrical power  and video connection to the laser?

--- On Fri, 11/13/09, Adam Seychell <a_seychell@....au> wrote:

From: Adam Seychell <a_seychell@...>
Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER Diodes
To: Homebrew_PCBs@yahoogroups.com
Date: Friday, November 13, 2009, 12:47 PM







 



  


    
      
      
      Volkan Sahin wrote:

>  



> I added laser to the side of inkjet head and I'm using raster scanning 

> method to expose photoresist.

> I've the same idea to use polygon mirrors of a old laser printer. I've 

> one Brother printer which has an aluminum mirror (most of them have a 

> copper or gold plated mirror on  aluminum because of IR laser) and 

> plastic lenses it seems it is possible to use with blue laser. I did 

> some rough measurements and I saw that on optical path I'm loosing ~30% 

> of the power most of it is because of diagonal mirrors because of that I 

> left it for a future project.   

> 



The polygon mirror concept sounds more difficult to implement.

How about a large diameter disc with a laser diode mounted on the 

perimeter. The PCB moves linear to the disc. Software would compensate 

for uniform exposure energy.



Assume that:



Resolution	= 0.005cm (50um)

Disc diameter 	= 15cm

Energy 		= 60mj/cm^2

Laser power 	= 85mW



Then



maximum disc RPM

	= 60 * 1cm/0.005cm / (60/85 * 15*1)

	= 1133



1000 RPM sounds reasonable.





    
     

    
    


 



  






      

[Non-text portions of this message have been removed]

The main problem I see is exposing the centre area of the spiral. You 
would need to align the disk axis so aligns within 50um of linear axis 
of the laser. I'm sure exposure intensity can easily be compensated in 
software for constant disk RPM.

Adam

Leslie Newell wrote:

>  
> 
> The tricky bit is keeping the exposure times reasonably equal. The disk
> would have to speed up as the laser approaches the center line. Nice
> idea though...
> 
> Les
> 
> javaguy11111 wrote:
>  >
>  > --- In Homebrew_PCBs@ yahoogroups. com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "designer_craig" <cs6061@...> 
> wrote:
>  >> I looked into a couple of these but I believe they are for island 
> milling. Converting the xy moves from the gerber to the G-code is the 
> easy part the files are almost exactly the same syntax.
>  >>
>  >
>  > I wonder if instead of trying to do cartesian scans, put the board on 
> some sort of a spinning disk and run the laser in a radial direction or 
> a polar scan. Basically what is done on a DVD writer. You could keep the 
> .001 spot size and just spiral in.
>  > That way you are not wasting time with a bunch of stop and start 
> motion. May be easier to construct as well.
> 
>

You can control the spot size of the laser beam by moving the Z-axe of your mill.  Focusing the beam produce a cone of light which is truncated when the laser hit the surface.  The focal length of your optics and the distance from your output lens surface will permit you calculate or estimate the spot diameter.  I think that maybe this is a good way to "simulate" the aperture.   

Lucho

--- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@...> wrote:

>
> I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
> 
> Its the aperture definitions that cause the problem. The origional photo plotters used an aperture wheel to project the correct spot size for the trace width and donut pads. But with the laser I will need to write macros to draw these from a single .001" dia spot. I took a look at Diptrace's Gerber output and currently they don't do anything exotic just x-y moves and apeture settings. For me to write and 8mill wide trace I will have to do the xy move 8 times with .001 offsets between writes. If this works out to be too slow I may have to increase the spot size somewhat. Would be nice to figure out how to have several different spot sizes.  I guess one could use multiple laser diodes and just select the best one for the task at hand. It would be no problem selecting the correct diode in the G-code.
> 
> 
> Craig 
> 
> --- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@> wrote:
> >
> > For your problem to convert to Gcode from gerber, there are three ways:
> > -pcb-gcode (works ok but in Eagle)
> > -export to DXF then into Cam package like LazyCAM with Mach3
> > -some commerical package made to CNC mill out pcbs from gerbers (forget the
> > name, was on pcb-gcode group)
> > 
> > On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@> wrote:
> > 
> > >
> > >
> > > I had the same idea last spring and purchased a 405nm laser diode with
> > > holder/lense and some Riston film off ebay. I added a heat sink to the
> > > holder and have driven it up to 110ma. At that power level it will burn
> > > through paper, so I have no doubts that it should harden the photo resist. I
> > > did some initial crude calculations based on the Riston data and estimated
> > > diode power that led me to believe it would be possible to write a .001" dia
> > > spot at 80"/sec.
> > >
> > > My initial plan is not to raster scan the board but to vector draw the
> > > pattern using my Bridgeport mill that is currently being converted to CNC. I
> > > will need to write some code to convert the Gerber photo plot file to a
> > > G-Code file to drive the mill. These files are very similar, the Gerber
> > > format being an offshoot of the G-code format. Since I plann on using a
> > > fixed spot size, wide traces will need multiple passes as will donuts etc.
> > > This all has to be coded in the conversion program.
> > >
> > > Currently I am working on the mill's CNC conversion and have not done any
> > > testing on the direct exposure part of the project. It will be a couple of
> > > months before the mill is ready for PCB testing.
> > >
> > > Issues to be resolved:
> > > 1.Is the exposure of photo resist linear ie. is high power UV for a short
> > > time the same as low power UV for a longer time.
> > >
> > > 2.Code to make multiple passes for trace and shape widths from the point
> > > gerber data.
> > >
> > > 3.How to get a .001" dia round spot. The laser diode output is not round.
> > > How to measure the spot dia.
> > >
> > > 4.How long will it take to expose a 3'x5" board?
> > >
> > > Craig
> > >
> > >
> > >  
> > >
> > 
> > 
> > [Non-text portions of this message have been removed]
> >
>

Volkan Sahin wrote:
>   
> Good idea. How to make reliable electrical power  and video connection
> to the laser?


You could use a circular pcb with 2 big circles made off copper tracks
and some electric motor brushes to connect power. The signal must be
made with a two parts optocoupler on center. Once I saw the pcb with 3
brushes to implement one 2seconds per turn malfunction sensor.

But isn't this sensitive to distance from the laser and photoresist? 

Comercial machines like this print small portions off the artwork each
time, needing 2 linear axis, and (i guess) mirrors on the rotative axis.

> 
> --- On Fri, 11/13/09, Adam Seychell <a_seychell@...> wrote:
> 
> From: Adam Seychell <a_seychell@...>
> Subject: Re: [Homebrew_PCBs] Making PCB using these new 405nm LASER
> Diodes
> To: Homebrew_PCBs@yahoogroups.com
> Date: Friday, November 13, 2009, 12:47 PM
> 
>  
> 
> Volkan Sahin wrote:
> 
> > 
> 
> > I added laser to the side of inkjet head and I'm using raster
> scanning 
> 
> > method to expose photoresist.
> 
> > I've the same idea to use polygon mirrors of a old laser printer.
> I've 
> 
> > one Brother printer which has an aluminum mirror (most of them have
> a 
> 
> > copper or gold plated mirror on aluminum because of IR laser) and 
> 
> > plastic lenses it seems it is possible to use with blue laser. I
> did 
> 
> > some rough measurements and I saw that on optical path I'm loosing
> ~30% 
> 
> > of the power most of it is because of diagonal mirrors because of
> that I 
> 
> > left it for a future project. 
> 
> > 
> 
> The polygon mirror concept sounds more difficult to implement.
> 
> How about a large diameter disc with a laser diode mounted on the 
> 
> perimeter. The PCB moves linear to the disc. Software would
> compensate 
> 
> for uniform exposure energy.
> 
> Assume that:
> 
> Resolution = 0.005cm (50um)
> 
> Disc diameter = 15cm
> 
> Energy = 60mj/cm^2
> 
> Laser power = 85mW
> 
> Then
> 
> maximum disc RPM
> 
> = 60 * 1cm/0.005cm / (60/85 * 15*1)
> 
> = 1133
> 
> 1000 RPM sounds reasonable.
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 
>

Hi, Craig.

The vector plotting reminds me of pen plotters - pen-down would be laser-on; pen-up would be laser-off.  I don't think that's part of the G-code or Gerber instruction set, though.

The round spot may take some non-spherical optics.  Think astigmatism.

As for the rest - very cool.
Donald

----- Original Message -----
From: "designer_craig" <cs6061@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, November 13, 2009 2:21:00 PM GMT -05:00 US/Canada Eastern
Subject: [Homebrew_PCBs] Re: Making PCB using these new 405nm LASER Diodes

I had the same idea last spring and purchased a 405nm laser diode with holder/lense and some Riston film off ebay.  I added a heat sink to the holder and have driven it up to 110ma.  At that power level it will burn through paper, so I have no doubts that it should harden the photo resist. I did some initial crude calculations based on the Riston data and estimated diode power that led me to believe it would be possible to write a .001" dia spot at 80"/sec.

My initial plan is not to raster scan the board but to vector draw the pattern using my Bridgeport mill that is currently being converted to CNC. I will need to write some code to convert the Gerber photo plot file to a G-Code file to drive the mill.  These files are very similar, the Gerber format being an offshoot of the G-code format. Since I plann on using a fixed spot size, wide traces will need multiple passes as will donuts etc. This all has to be coded in the conversion program.  

Currently I am working on the mill's CNC conversion and have not done any testing on the direct exposure part of the project. It will be a couple of months before the mill is ready for PCB testing.

Issues to be resolved:
1.Is the exposure of photo resist linear ie. is high power UV for a short time the same as low power UV for a longer time.

2.Code to make multiple passes for trace and shape widths from the point gerber data.

3.How to get a .001" dia round spot.  The laser diode output is not round. How to measure the spot dia.

4.How long will it take to expose a 3'x5" board?

Craig

I will have to play with that when I get the mill put back together. I am in the process of rebuilding the head I just have a few more things take apart, clean and paint.

The LD beam shap is not round more like an oval.  Through some Google research it would appear that I need to expand the raw beam and pass it through a known round aperture of say .010 -.020" then focus it using a lense.  The natural beam angle may be enough to to expand it to cover the aperture. You do loose some power by cutting off some of the beam to round it up with the aperture. Then its just a focus lense issue.  I have to read up on lense ray tracing.  I would like to experiment with a microscope objective for a lense, lots of them on ebay.

--- In Homebrew_PCBs@yahoogroups.com, "lmri2071" <lmri2071@...> wrote:

>
> You can control the spot size of the laser beam by moving the Z-axe of your mill.  Focusing the beam produce a cone of light which is truncated when the laser hit the surface.  The focal length of your optics and the distance from your output lens surface will permit you calculate or estimate the spot diameter.  I think that maybe this is a good way to "simulate" the aperture.   
> 
> Lucho
> 
> --- In Homebrew_PCBs@yahoogroups.com, "designer_craig" <cs6061@> wrote:
> >
> > I looked into a couple of these but I believe they are for island milling.  Converting the xy moves from the gerber to the G-code is the easy part the files are almost exactly the same syntax.
> > 
> > Its the aperture definitions that cause the problem. The origional photo plotters used an aperture wheel to project the correct spot size for the trace width and donut pads. But with the laser I will need to write macros to draw these from a single .001" dia spot. I took a look at Diptrace's Gerber output and currently they don't do anything exotic just x-y moves and apeture settings. For me to write and 8mill wide trace I will have to do the xy move 8 times with .001 offsets between writes. If this works out to be too slow I may have to increase the spot size somewhat. Would be nice to figure out how to have several different spot sizes.  I guess one could use multiple laser diodes and just select the best one for the task at hand. It would be no problem selecting the correct diode in the G-code.
> > 
> > 
> > Craig 
> > 
> > --- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@> wrote:
> > >
> > > For your problem to convert to Gcode from gerber, there are three ways:
> > > -pcb-gcode (works ok but in Eagle)
> > > -export to DXF then into Cam package like LazyCAM with Mach3
> > > -some commerical package made to CNC mill out pcbs from gerbers (forget the
> > > name, was on pcb-gcode group)
> > > 
> > > On Fri, Nov 13, 2009 at 11:21 AM, designer_craig <cs6061@> wrote:
> > > 
> > > >
> > > >
> > > > I had the same idea last spring and purchased a 405nm laser diode with
> > > > holder/lense and some Riston film off ebay. I added a heat sink to the
> > > > holder and have driven it up to 110ma. At that power level it will burn
> > > > through paper, so I have no doubts that it should harden the photo resist. I
> > > > did some initial crude calculations based on the Riston data and estimated
> > > > diode power that led me to believe it would be possible to write a .001" dia
> > > > spot at 80"/sec.
> > > >
> > > > My initial plan is not to raster scan the board but to vector draw the
> > > > pattern using my Bridgeport mill that is currently being converted to CNC. I
> > > > will need to write some code to convert the Gerber photo plot file to a
> > > > G-Code file to drive the mill. These files are very similar, the Gerber
> > > > format being an offshoot of the G-code format. Since I plann on using a
> > > > fixed spot size, wide traces will need multiple passes as will donuts etc.
> > > > This all has to be coded in the conversion program.
> > > >
> > > > Currently I am working on the mill's CNC conversion and have not done any
> > > > testing on the direct exposure part of the project. It will be a couple of
> > > > months before the mill is ready for PCB testing.
> > > >
> > > > Issues to be resolved:
> > > > 1.Is the exposure of photo resist linear ie. is high power UV for a short
> > > > time the same as low power UV for a longer time.
> > > >
> > > > 2.Code to make multiple passes for trace and shape widths from the point
> > > > gerber data.
> > > >
> > > > 3.How to get a .001" dia round spot. The laser diode output is not round.
> > > > How to measure the spot dia.
> > > >
> > > > 4.How long will it take to expose a 3'x5" board?
> > > >
> > > > Craig
> > > >
> > > >
> > > >  
> > > >
> > > 
> > > 
> > > [Non-text portions of this message have been removed]
> > >
> >
>

Volkan Sahin wrote:
>  
> 
> Good idea. How to make reliable electrical power  and video connection 
> to the laser?
> 

Ok, maybe not such a good idea. Are laser scanners assemblies expensive ?

Some searching revels:

http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+MT+2+AHA1002+0+4+WW
http://pdf1.alldatasheet.com/datasheet-pdf/view/40569/SANYO/LB1872.html
http://projects.uniprecision.com/sc_upload/images/C060_DATASHEET_RAW.pdf


Still, cannot find a supplier of these "laser mirror scanner motors".
This looks like the way to go.

Adam

Is it not possible to either reduce/control the power output to a safe level or to substitute a normal laser pointer just for setting up? (I am a total newbie with lasers, I am just trying to learn at the same time....!)
Greetings from

Andy Mathison

[Non-text portions of this message have been removed]

The Polygon mirror, with its motor and the special comb to provide for the signals of the position of the mirror, can be found in early, non LED Laser printers from IBM, Unisys, Univac and Siemens (and some others that I have forgotten the names of!).....ones from around 15 to 35 years ago. You need to find a breakers yard that specializes in such items......it simplifies the scanning dramatically.......
  Its actually quite an easy system to work with......modern electronics being what they are.....
  As someone else also pointed out, laser safety glasses are a must at ALL times.....
  The only other way I can think of using the laser is an X-Y system using fine stepper motors and angled mirrors on the shafts, on for the x and one for the y. Disco's use a similar (but not accurate enough for this work) system to write on walls with laser light. Then I am sure that software could be easily written to control the laser on and off and also to scan. In fact you really only need to drive one motor at a time, so software could be very easy, connected via a parallel printer port card to the stepper drivers. Stepper motors are around that have 400 steps per revolution, which may or may not be fine enough, but using say T5 toothed belts and pulleys, it would be quite easy to multiply that by 10:1 gearing. There is also microstepping, which can chop the steps of the motor up by quite large amounts, 16 microsteps per revolution is quite normal for 200 step motors, which are very common.
  If you go in this direction, do buy the best motors that you can find so that the steps are as accurate as possible....
  Furthermore, it may be a good idea (if this direction is chosen to open up a new blog just to construct such a system......just a thought or two......
  Also, instead of scanning, one could use vector graphics to cut out the PCB. Both systems could be tried out using the same hardware!!!
  That my multiple 2 cents worth, have fun!
  Greetings from
Andy Mathison

[Non-text portions of this message have been removed]

Dear lmri2071 

  You wrote:-
  You can control the spot size of the laser beam by moving the Z-axe of your mill. Focusing the beam produce a cone of light which is truncated when the laser hit the surface. The focal length of your optics and the distance from your output lens surface will permit you calculate or estimate the spot diameter. I think that maybe this is a good way to "simulate" the aperture. 
  Lucho

  Simply brilliant!!! Why did we not think of that before!!!!!
Greetings from

Andy Mathison

[Non-text portions of this message have been removed]

Adam Seychell wrote:
> Volkan Sahin wrote:
>>  
>>
>> Good idea. How to make reliable electrical power  and video connection 
>> to the laser?
>>
> 
> Ok, maybe not such a good idea. Are laser scanners assemblies expensive ?
> 
> Some searching revels:
> 
> http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+MT+2+AHA1002+0+4+WW
> http://pdf1.alldatasheet.com/datasheet-pdf/view/40569/SANYO/LB1872.html
> http://projects.uniprecision.com/sc_upload/images/C060_DATASHEET_RAW.pdf
> 
> 
> Still, cannot find a supplier of these "laser mirror scanner motors".
> This looks like the way to go.

You can drive the motor in any laser printer scanner head. It's only a problem
getting motors if you want to build your own head and optics.

You could pull apart an old hard-disk and mount a mirror on the platter.
Drive the 3-phase motor yourself. At 30k rpm, you'll need to be very good
at balancing/centralizing the mirror, and have it *firmly* stuck down or
it might launch off in to outer space.

If you want an /easy/ way to do this, just buy something like a Roland DXY
type plotter off ebay.

I bought two, a roland DXY880 and another a roland  dxy1280 I think.

Both do at 11x17 or bigger I think.

Anyway, I was planning on using these as a gantry for another project but
it's pretty flismy.  The construction is cheap cheap plastic.  The drive
mechanism is two wire piano wires hooked up to a stepper motor.

The nice thing about these things is there is a pen solenoid inside that is
12V.  In the best case, you only need to desolder the solenoid and solder
the laser power leads from the driver onto the board.  In the worst case,
there's a 5V ttl signal that goes on whenever the pen down function is
activated which can be used to drive a mosfet or other MCU+mosfet.

The Roland DXY even has a modern print driver.  Just print from any
application, say Eagle PCB or Altium.  No additional software needed.

Would make a cheap laser cutter/stencil maker if the laser is powerful
enough.

You could probably swap a far infrared laser diode for cutting organics (far
infrared seems to absorb into clear plastic very well from my CO2 laser
experience) like mylar or kapton film to make stencils also.

Since I have two that are sitting in my garage, I'd sell them for whatever I
paid for them which was somewhere between $80-150 (need to check my
receipt).  Excellent condition and works great.

I can just use my CO2 laser gantry which I designed a controller for and
also already rasterscan engraves so no need for me.  Too many projects too
little time.

Henry



On Sat, Nov 14, 2009 at 5:39 AM, Russell Shaw <rjshaw@...>wrote:

>
>
> Adam Seychell wrote:
> > Volkan Sahin wrote:
> >>
> >>
> >> Good idea. How to make reliable electrical power and video connection
> >> to the laser?
> >>
> >
> > Ok, maybe not such a good idea. Are laser scanners assemblies expensive ?
> >
> > Some searching revels:
> >
> >
> http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+MT+2+AHA1002+0+4+WW
> > http://pdf1.alldatasheet.com/datasheet-pdf/view/40569/SANYO/LB1872.html
> > http://projects.uniprecision.com/sc_upload/images/C060_DATASHEET_RAW.pdf
> >
> >
> > Still, cannot find a supplier of these "laser mirror scanner motors".
> > This looks like the way to go.
>
> You can drive the motor in any laser printer scanner head. It's only a
> problem
> getting motors if you want to build your own head and optics.
>
> You could pull apart an old hard-disk and mount a mirror on the platter.
> Drive the 3-phase motor yourself. At 30k rpm, you'll need to be very good
> at balancing/centralizing the mirror, and have it *firmly* stuck down or
> it might launch off in to outer space.
>
> 
>


[Non-text portions of this message have been removed]

The laser diodes don't start to lase until the current reaches a threshold value.  Even at the threshold the power output is significant in relation to eye damage. One need to be very careful working with UV lasers it only takes a fraction of a second to cause retina damage.  Even be carful of a reflected spot on paper.

The best suggestion I have seen so far is to use thermal fax paper to image the spot size and shape.  I will give that a try as soon as I find some paper.  My diode will burn through paper very easly at less than 100ma drive.

Craig

--- In Homebrew_PCBs@yahoogroups.com, "Andrew Mathison" <andrewdavid.mathison@...> wrote:

>
>   Is it not possible to either reduce/control the power output to a safe level or to substitute a normal laser pointer just for setting up? (I am a total newbie with lasers, I am just trying to learn at the same time....!)
> Greetings from
> 
> Andy Mathison
> 
> [Non-text portions of this message have been removed]
>

Donald,
In the Gerber code D1 is "expose on", D2 is "expose off" and D3 is "flash".  For the Gcode one could convert these to M codes like spindle on/off.  Another way is to convert D1/D1 to S codes "spindle speed"  Then in the laser diode electronics one could modulate the power ie.  S0 = off  S100 = full power  S50 = 50% power etc. Its just some code for the file conversion program.

I am not sure how much trouble the mill's X and Y acceleration ramp will be to the exposure profile.  Would like not to have to compensate the power during movement ramp up. I think in Mach3 one would treat it like a plasma cutter and use CV mode.

Craig

--- In Homebrew_PCBs@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:

>
> Hi, Craig.
> 
> The vector plotting reminds me of pen plotters - pen-down would be laser-on; pen-up would be laser-off.  I don't think that's part of the G-code or Gerber instruction set, though.
> 
> The round spot may take some non-spherical optics.  Think astigmatism.
> 
> As for the rest - very cool.
> Donald
> 
> ----- Original Message -----
> From: "designer_craig" <cs6061@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Friday, November 13, 2009 2:21:00 PM GMT -05:00 US/Canada Eastern
> Subject: [Homebrew_PCBs] Re: Making PCB using these new 405nm LASER Diodes
> 
> I had the same idea last spring and purchased a 405nm laser diode with holder/lense and some Riston film off ebay.  I added a heat sink to the holder and have driven it up to 110ma.  At that power level it will burn through paper, so I have no doubts that it should harden the photo resist. I did some initial crude calculations based on the Riston data and estimated diode power that led me to believe it would be possible to write a .001" dia spot at 80"/sec.
> 
> My initial plan is not to raster scan the board but to vector draw the pattern using my Bridgeport mill that is currently being converted to CNC. I will need to write some code to convert the Gerber photo plot file to a G-Code file to drive the mill.  These files are very similar, the Gerber format being an offshoot of the G-code format. Since I plann on using a fixed spot size, wide traces will need multiple passes as will donuts etc. This all has to be coded in the conversion program.  
> 
> Currently I am working on the mill's CNC conversion and have not done any testing on the direct exposure part of the project. It will be a couple of months before the mill is ready for PCB testing.
> 
> Issues to be resolved:
> 1.Is the exposure of photo resist linear ie. is high power UV for a short time the same as low power UV for a longer time.
> 
> 2.Code to make multiple passes for trace and shape widths from the point gerber data.
> 
> 3.How to get a .001" dia round spot.  The laser diode output is not round. How to measure the spot dia.
> 
> 4.How long will it take to expose a 3'x5" board?
> 
> Craig
>

Adam Seychell wrote:

> 
> Ok, maybe not such a good idea. Are laser scanners assemblies
> expensive ?
> Still, cannot find a supplier of these "laser mirror scanner motors".
> This looks like the way to go.

It's free (as free beer), or at least i can send you one for free. Is
just like those, a little bigger with a 2 levels 6 faces mirror, more
precise with 3 hall effect sensors and LB1876 driver. Or you could
remove it from a copier machine.

A year ago i had the idea to exchange the IR led in a laser printer by a
UV led. Since laser printers have all the optics assemble in a removable
'box' inside wasn't that problematic doing it. So i asked someone who
works with laser printers, about the optics efficiency on UV and he give
me all the mirrors lenses sensors etc from a fast color copier with
manuals and schematics and said to try it myself! The thing has also
very small stepper motors for mirrors adjustment between colors.

But using it need assembling all this correctly aligned. If i got the
parts in the assembly will be much easier, and the led's  i known about
wont work.

The person is an ebay seller from who i got nice stepper motor and
microstepping controllers and he offered lots more stuff which i ended
using nothing...

BUT there is a much simpler way ( i think ). 
With rotation you will need one 'zeroing' light sensor like on laser
printers ( yes i can offer you one too) and precise timing electronics
say a fast fpga with memory.
My view is to use the laser in a pendulum, moved by a eccentric
connection to a wheel with a motor (like vapor train but opposite). The
motor could me a stepper motor running at 500rpm and you print on both
movements. For 'zeroing' you could use one light sensor on the wheel.
The good thing is if you print only a small line (say 2cm or less) not
only the led power could be constant but if under the 256 count off
'dots' you could do all inside a common microcontroller with low
bandwidth to a computer. It drives a microstepper controller at constant
speed and with a counter turns on and off the laser. The 'commands' need
to be 'print from xx to yy' turning on the laser from position xx and
off on yy, making a trace not a dot. For efficiency the command should
allow multiple traces on same line. The computer needs to calculate the
precise position since each step on the motor is a angle with non linear
relation on the pcb.

Ok writing were is easy, you already get the picture, i will stop now.

Russell Shaw wrote:
> You can drive the motor in any laser printer scanner head. It's only a 
> problem
> getting motors if you want to build your own head and optics.
> 
> You could pull apart an old hard-disk and mount a mirror on the platter.
> Drive the 3-phase motor yourself. At 30k rpm, you'll need to be very good
> at balancing/centraliz ing the mirror, and have it *firmly* stuck down or
> it might launch off in to outer space.
> 


Those links to data sheets are of complete polygon mirror motor 
assemblies. You supply 24V and then point a laser on them. I don't think 
I can fabricate anything close to such precision. The mirrors flatness 
and symmetry are absolutely critical.  They look like mass produced 
items so I don't think they should be expensive. But where ?

This mob specialises in polygon mirror motor assemblies. They have lots 
of technical application notes too.
http://www.lincolnlaser.com/index.cfm

Adam

There it's no need to spin the laser diode. On the motor just put 2 mirrors like in periscope and that's all.
It just needs a sync mechanism.

Where in the world can I buy positive photoresist?

I might be interested in one of those.  Can you contact me with the specifics?

Dave Witten


--- In Homebrew_PCBs@yahoogroups.com, Henry Liu <henryjliu@...> wrote:
>
> If you want an /easy/ way to do this, just buy something like a Roland DXY
> type plotter off ebay.
> 
> I bought two, a roland DXY880 and another a roland  dxy1280 I think.
> 
> Both do at 11x17 or bigger I think.
> 
> Anyway, I was planning on using these as a gantry for another project but
> it's pretty flismy.  The construction is cheap cheap plastic.  The drive
> mechanism is two wire piano wires hooked up to a stepper motor.
> 

...

> Since I have two that are sitting in my garage, I'd sell them for whatever I
> paid for them which was somewhere between $80-150 (need to check my
> receipt).  Excellent condition and works great.
> 
> Too many projects too little time.
> 
> Henry
> 
> 
> 
> On Sat, Nov 14, 2009 at 5:39 AM, Russell Shaw <rjshaw@...>wrote:
> 
> >
> >
> > Adam Seychell wrote:
> > > Volkan Sahin wrote:
> > >>
> > >>

...

--- In Homebrew_PCBs@yahoogroups.com, Terry Mickelson <tmlist@...> wrote:
>
> Where in the world can I buy positive photoresist?
>

Myself I use M G Chemicals  600 Series boards, they come with positive resist on them.  I normally buy thru Mouser   www.mouser.com.

You may can get them also @
www.alliedelec.com
www.circuitspecialists.com

Oh FYI looks like maybe you just changed the Subject instead of starting a new thread as this seems to be attached with the Laser Diode Thread.

Ben