Homebrew PCBs

I wonder why would anybody go that route? Paints use solvent and 
solvents call for ventillation unless someone doesn't believe in it.

Bottom line is, there is a perfect method of TT and I don't 
understand why someone says that it is not fast enough-- are we 
talking about  a contest of some kind??

Then for people who need/want/must have more resolution, there is a 
UV method, slightly more complex.

But silk screen? I was around silk screen lab for a while and unless 
you want to make PCBs on glass (for touch screens) or on ceramics 
(have no idea why) then silk screen is not a good method for home use 
unless someone enjoys an excercise in... futility.  Mike

Silk screen for legend print is superior to TT on double sided boards.
 I'd also think it would be good way to make front panels.  I'm not
sure about for resist patterns since the resolution will be lower than
TT but if some one has that equipment available, no need to invest in
other stuff - make do with what you have.  Not a bad philosophy.

I think you'd want ventilation no matter what.  I do.

Again, we disagree on the perfection point but no need to rehash that.

Phil

--- In Homebrew_PCBs@yahoogroups.com, "mikezcnc" <eemikez@c...> wrote:

> 
> I wonder why would anybody go that route? Paints use solvent and 
> solvents call for ventillation unless someone doesn't believe in it.
> 
> Bottom line is, there is a perfect method of TT and I don't 
> understand why someone says that it is not fast enough-- are we 
> talking about  a contest of some kind??
> 
> Then for people who need/want/must have more resolution, there is a 
> UV method, slightly more complex.
> 
> But silk screen? I was around silk screen lab for a while and unless 
> you want to make PCBs on glass (for touch screens) or on ceramics 
> (have no idea why) then silk screen is not a good method for home use 
> unless someone enjoys an excercise in... futility.  Mike

I like the concept of toner transfer, but the paper is still a problem.  Unfortunately, most paper manufacturers put a lot of development effort into making their paper more resistant to water.

We are finding that using the Staples photo paper it takes about an hour of soaking and scrupbbing to get the bits of paper out from between the circuit tracks.  I thought .020" spacing would be sufficient to minimize this problem but it looks like I was wrong.  The scrubbing damages some traces thus requiring 30 minutes to an hour of inspection and touchup.  For a prototype this is fine, but we're looking at up to 50 4" x 6" boards per design.  Not one off, yet not enough for sending to a commercial shop.  Of course a small shop would be happy to run 2 or 3 panels but at prototyping rates.  So we're looking for a more reliable process.  

Ventilation is not a problem as we all have paint spraying facilities.  We found several silk screen material suppliers that had water based emulsions that are intended for home craft use.  So we're looking at as a potential alternative.

  ----- Original Message ----- 
  From: mikezcnc 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Wednesday, January 19, 2005 11:55 AM
  Subject: [Homebrew_PCBs] Silk screen methods at home?



  I wonder why would anybody go that route? Paints use solvent and 
  solvents call for ventillation unless someone doesn't believe in it.

  Bottom line is, there is a perfect method of TT and I don't 
  understand why someone says that it is not fast enough-- are we 
  talking about  a contest of some kind??

  Then for people who need/want/must have more resolution, there is a 
  UV method, slightly more complex.

  But silk screen? I was around silk screen lab for a while and unless 
  you want to make PCBs on glass (for touch screens) or on ceramics 
  (have no idea why) then silk screen is not a good method for home use 
  unless someone enjoys an excercise in... futility.  Mike





  Be sure to visit the group home and check for new Bookmarks and files:
  http://groups.yahoo.com/group/Homebrew_PCBs 



------------------------------------------------------------------------------
  Yahoo! Groups Links

    a.. To visit your group on the web, go to:
    http://groups.yahoo.com/group/Homebrew_PCBs/
      
    b.. To unsubscribe from this group, send an email to:
    Homebrew_PCBs-unsubscribe@yahoogroups.com
      
    c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



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

I am one of the people looking at silk screening for resist
application.  
When I get toner transfer to work, inclulding getting the paper to come
off, given my limitation of having to use commercial copiers, some of
whose operators are reluctant to put inkjet paper in their very
expensive laser machines, I will be happy to stay with TT.  So far the
mechanics of resist application and paper removal have been unsuccessful
enough that I have not even got around to etching yet.  That includes
using some of the recommended papers.  I have not yet tried Pulsar's
paper.

More specifically, what copier/printer, toner, and paper are you using?

Thank you,

Steve Bartlett

mikezcnc wrote:
> ...
> Bottom line is, there is a perfect method of TT and I don't
> understand why someone says that it is not fast enough-- are we
> talking about  a contest of some kind??
> 
...  Mike
>

On Wed, 19 Jan 2005 15:11:44 -0500, Stephen Bartlett  
<tower.op@...> wrote:

> I am one of the people looking at silk screening for resist
> application.
> When I get toner transfer to work, inclulding getting the paper to come
> off, given my limitation of having to use commercial copiers, some of
> whose operators are reluctant to put inkjet paper in their very
> expensive laser machines, I will be happy to stay with TT.  So far the
> mechanics of resist application and paper removal have been unsuccessful
> enough that I have not even got around to etching yet.  That includes
> using some of the recommended papers.  I have not yet tried Pulsar's
> paper.
> More specifically, what copier/printer, toner, and paper are you using?
> Thank you,
> Steve Bartlett


look in the database section of the group page for working printers and  
papers.
I am not so sure silkscreening equipment is cheaper than a laser printer.  
Also, i don't think
it is cheaper than UV photo process by much.

If you can live with 300dpi a laser jet 3 can be had for less than 10$,  
and works well.

ST

Stefan,

Thank you for your suggestions.  I have looked at almost all, if not all
of the files section, and a number of related links to sites.

I have tried a number of papers and copiers - may just have not hit on
the right combination.  FWIW, I have had very different results from the
same make and model copier at two different locations.

Where does one find a Laser Jet 3 for $10.00?

Stefan Trethan wrote:

> look in the database section of the group page for working printers and
> papers.
> ...
> If you can live with 300dpi a laser jet 3 can be had for less than 10$,
> and works well.
> 
> ST

On Wed, 19 Jan 2005 19:51:06 -0500, Stephen Bartlett  
<tower.op@...> wrote:

>
> Stefan,
>
> Thank you for your suggestions.  I have looked at almost all, if not all
> of the files section, and a number of related links to sites.
>
> I have tried a number of papers and copiers - may just have not hit on
> the right combination.  FWIW, I have had very different results from the
> same make and model copier at two different locations.
>
> Where does one find a Laser Jet 3 for $10.00?
>

I'm not sure if you also checked the Database section.

The right hardware is important, but even with the same hardware one may  
have good results and one bad.

I've seen several LJ III for that money at ebay.
It is a really old printer and just meant as a example, i'd pay more for a  
newer unit.

ST

Thank you; I just took a look.  (This is the first time on many
Yahoo-lists that I have ever seen anything in the Database section).  I
now have a bit more informatioan to work with.

Steve Bartlett

Stefan Trethan wrote:
> 

> I'm not sure if you also checked the Database section.
> 
...
> ST

I'd like to build a UV box to do positive resist exposure. The 
presensitized boards are 5 by 7 inches, so the box and lamps need not 
be too large. Also not too hot as this box is only open on the bottom. 
LED's are under consideration but so far a pre-made PC board to hold 
400 or so is too expensive. The board is nothing more than etched 
parallel lines with drilled holes every .1 inch. UV lamps are a second 
choice but they tend to fade and burn out over time.
What are your recommendations?
Terry M

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

From: "Terry Mickelson" <tmdslca@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, January 20, 2005 9:33 PM
Subject: [Homebrew_PCBs] UV lamps?


>
> I'd like to build a UV box to do positive resist exposure. The
> presensitized boards are 5 by 7 inches, so the box and lamps need not
> be too large. Also not too hot as this box is only open on the bottom.
> LED's are under consideration but so far a pre-made PC board to hold
> 400 or so is too expensive. The board is nothing more than etched
> parallel lines with drilled holes every .1 inch. UV lamps are a second
> choice but they tend to fade and burn out over time.
> What are your recommendations?

UV LEDs are the wrong wavelength and don't generate enough power. I've been 
using the same UV tubes for about three years and am still using the same 
exposure time. They do deteriorate, but is is quite slow, especially as the 
usage tends to be very intermittent.

Leon 



-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.7.1 - Release Date: 19/01/2005

I hope you don't mean mercury arc lamps.  They have the right wavelength (365 nm) for fast exposure, but they can cause serious eye damage.  Try some of those 'black light' tubes.  The exposure is longer, but they last a long time and they won't produce any eye damage.

  ----- Original Message ----- 
  From: Terry Mickelson 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Thursday, January 20, 2005 4:33 PM
  Subject: [Homebrew_PCBs] UV lamps?


  I'd like to build a UV box to do positive resist exposure. The 
  presensitized boards are 5 by 7 inches, so the box and lamps need not 
  be too large. Also not too hot as this box is only open on the bottom. 
  LED's are under consideration but so far a pre-made PC board to hold 
  400 or so is too expensive. The board is nothing more than etched 
  parallel lines with drilled holes every .1 inch. UV lamps are a second 
  choice but they tend to fade and burn out over time.
  What are your recommendations?
  Terry M



  Be sure to visit the group home and check for new Bookmarks and files:
  http://groups.yahoo.com/group/Homebrew_PCBs 



------------------------------------------------------------------------------
  Yahoo! Groups Links

    a.. To visit your group on the web, go to:
    http://groups.yahoo.com/group/Homebrew_PCBs/
      
    b.. To unsubscribe from this group, send an email to:
    Homebrew_PCBs-unsubscribe@yahoogroups.com
      
    c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



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

I built one years ago, using a high intensity industrial 
hi-bay lamp and suitable ballast/transformer.  The glass 
envelope containing the fluorescent material around the 
quartz uv source must be broken off (carefully!) leaving 
only the quartz tube.  This gives a high intensity UV lamp 
that is very long lived.  Mine was built in the mid 1960's 
and the original tube is still going strong. The lamps are 
designed to run 24/7 for several years at a time. The only 
drawback is that it requires a relatively long 
turn-on/warmup time - like about 5 minutes for full 
brightness.  You need a mechanical shutter - a sheet of 
plywood, aluminum, etc., to block the light between 
exposures.  And VERY good eye protection.

Norm

Terry Mickelson wrote:
> I'd like to build a UV box to do positive resist exposure. The 
> presensitized boards are 5 by 7 inches, so the box and lamps need not 
> be too large. Also not too hot as this box is only open on the bottom. 
> LED's are under consideration but so far a pre-made PC board to hold 
> 400 or so is too expensive. The board is nothing more than etched 
> parallel lines with drilled holes every .1 inch. UV lamps are a second 
> choice but they tend to fade and burn out over time.
> What are your recommendations?
> Terry M
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 
> 


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.6.13 - Release Date: 1/16/2005

Check out the following for a homemade UV exposure source:
http://www.thinktink.com/stack/volumes/voliii/equipment/uvlamp/uvlamp.
htm

If you don't need that much power, then look at the low-power UV 
offerings found at:
http://www.goldmine-elec.com/default.htm
Do a search for "UV".  Perhaps a stack of these small lamps will do 
the trick.

Lyman

It looks like I'll be buying some lamps. What should I look for or look 
out for in florescent types?
Terry M

There are two basic types of home-use UV tubes, which look like
fluorescent tubes, but are varying shades of dark blue.  It has been
years since I looked at a lamp catalog, but as I remember, the types
with designation ending in  "/BLB" are "black light blue," have a clear
tube, produce reduced visible light, and cost much more than the "BL"
type, which have an internal fluorescent coating and emit more visible
light.  Assuming the BL type will work for you, they should save you
money in initial cost.

Steve Bartlett

Terry Mickelson wrote:

It looks like I'll be buying some lamps. What should I look for or look 
out for in florescent types?
Terry M

I made a box using a 125W HID globe like the one on the right:

   http://www.specialtyoptical.com/catalog/160wsb_e24-bl_2712682.htm

The blue glass is "woods glass" and blocks all the bad short-wave UV
and longer wave white light.

I have it in a cylindrical parabolic reflector and is 60cm from the
glass. It exposes negative resist in 30secs, but i do 90secs to make
sure. Because of the distance, i get sharp traces regardless of which
side of the printout film i place against the pcb.

It take 2mins to warm up. If you switch it off, it won't switch on
for another few minutes.

There's a ton of blacklights:

http://unblinkingeye.com/Articles/Light/light.html
http://www.specialtyoptical.com/catalog/blacklights_264645_products.htm
http://www.lightbulbsdirect.com/page/001/CTGY/Blacklights
http://www.thelightbulbcompany.co.uk/product/prod161.html
http://www.topbulb.com/find/prod_list.asp?intSubCategory=557

http://www.google.com.au/search?hl=en&q=%22blacklight+blue%22+uv+hid&btnG=Search&meta=

Norman Stewart wrote:

> I built one years ago, using a high intensity industrial 
> hi-bay lamp and suitable ballast/transformer.  The glass 
> envelope containing the fluorescent material around the 
> quartz uv source must be broken off (carefully!) leaving 
> only the quartz tube.  This gives a high intensity UV lamp 
> that is very long lived.  Mine was built in the mid 1960's 
> and the original tube is still going strong. The lamps are 
> designed to run 24/7 for several years at a time. The only 
> drawback is that it requires a relatively long 
> turn-on/warmup time - like about 5 minutes for full 
> brightness.  You need a mechanical shutter - a sheet of 
> plywood, aluminum, etc., to block the light between 
> exposures.  And VERY good eye protection.
> 
> Norm
> 
> Terry Mickelson wrote:
> 
>>I'd like to build a UV box to do positive resist exposure. The 
>>presensitized boards are 5 by 7 inches, so the box and lamps need not 
>>be too large. Also not too hot as this box is only open on the bottom. 
>>LED's are under consideration but so far a pre-made PC board to hold 
>>400 or so is too expensive. The board is nothing more than etched 
>>parallel lines with drilled holes every .1 inch. UV lamps are a second 
>>choice but they tend to fade and burn out over time.
>>What are your recommendations?
>>Terry M

Stephen Bartlett wrote:
> There are two basic types of home-use UV tubes, which look like
> fluorescent tubes, but are varying shades of dark blue.  It has been
> years since I looked at a lamp catalog, but as I remember, the types
> with designation ending in  "/BLB" are "black light blue," have a clear
> tube,

BLB are dark blue "woods glass".

White tubes are just BL.

The clear tubes are actinic unfiltered and shouldn't be used because
of the more harmful shortwave uv which causes cataracts. Good for
erasing eproms tho.

> produce reduced visible light, and cost much more than the "BL"
> type, which have an internal fluorescent coating and emit more visible
> light.  Assuming the BL type will work for you, they should save you
> money in initial cost.
> 
> Steve Bartlett
> 
> Terry Mickelson wrote:
> 
> It looks like I'll be buying some lamps. What should I look for or look 
> out for in florescent types?
> Terry M
>

I don't know if this qualifies as home brew, but I've used for exposing
all my boards.  For $30, you can't go wrong:

http://www.web-tronics.com/exposuresystem.html

Exposure time is 5-6 minutes and I've had very good luck.

On Thu, 20 Jan 2005, Earl T. Hackett, Jr. wrote:

> 
> I hope you don't mean mercury arc lamps.  They have the right wavelength (365 nm) for fast exposure, but they can cause serious eye damage.  Try some of those 'black light' tubes.  The exposure is longer, but they last a long time and they won't produce any eye damage.
>   ----- Original Message ----- 
>   From: Terry Mickelson 
>   To: Homebrew_PCBs@yahoogroups.com 
>   Sent: Thursday, January 20, 2005 4:33 PM
>   Subject: [Homebrew_PCBs] UV lamps?
> 
> 
>   I'd like to build a UV box to do positive resist exposure. The 
>   presensitized boards are 5 by 7 inches, so the box and lamps need not 
>   be too large. Also not too hot as this box is only open on the bottom. 
>   LED's are under consideration but so far a pre-made PC board to hold 
>   400 or so is too expensive. The board is nothing more than etched 
>   parallel lines with drilled holes every .1 inch. UV lamps are a second 
>   choice but they tend to fade and burn out over time.
>   What are your recommendations?
>   Terry M
> 
> 
> 
>   Be sure to visit the group home and check for new Bookmarks and files:
>   http://groups.yahoo.com/group/Homebrew_PCBs 
> 
> 
> 
> ------------------------------------------------------------------------------
>   Yahoo! Groups Links
> 
>     a.. To visit your group on the web, go to:
>     http://groups.yahoo.com/group/Homebrew_PCBs/
>       
>     b.. To unsubscribe from this group, send an email to:
>     Homebrew_PCBs-unsubscribe@yahoogroups.com
>       
>     c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Somewhere around 10,000 hours half-life as best I recall!  Simply means
extending exposure times accordingly.  

Regards/Roger, in Bangkok

-----Original Message----- From: Terry Mickelson
[mailto:tmdslca@...] 
...

... UV lamps are a second choice but they tend to fade and burn out over
time.

...


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.7.1 - Release Date: 19-Jan-05

Stephen Bartlett wrote:
> There are two basic types of home-use UV tubes, which look like
> fluorescent tubes, but are varying shades of dark blue.  It has been
> years since I looked at a lamp catalog, but as I remember, the types
> with designation ending in  "/BLB" are "black light blue," have a clear
> tube, produce reduced visible light, and cost much more than the "BL"
> type, which have an internal fluorescent coating and emit more visible
> light.  Assuming the BL type will work for you, they should save you
> money in initial cost.
> 
> Steve Bartlett
> 

Yep, I used the "BL" type for my original light box, and they worked 
great. You buy them as lamps for "insect zappers". Lot cheaper than BLB, 
and I believe they emit same level of 365nm, which is what you need for 
photoresists. The "BLB" lamps are mainly for special effects but 5 X the 
cost. Both lamps are safe for skin, but I'm not sure about staring 
continuously at them. visit Sam's F-Lamp FAQ

http://members.misty.com/don/f-lamp.html

I'd recommend a single bulb fixture - the smallest you can get a lamp for - and back it up with a parabolic reflector.  You will be trading light columination for intensity while trying to maintain uniformity over the exposure area.  Good columnation and high intensity are good for resolution.  Unfortunately if you stick the bulb smack against the artwork, you get lots of intensity but lousy columnation.  Back the bulb across the room and you get columnation and no intensity.  Somewhere in between (probably 16" to 30" depending on the quality of the reflector) is what you want, but you'll have to experiment a bit to find it.

  ----- Original Message ----- 
  From: Terry Mickelson 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Thursday, January 20, 2005 9:50 PM
  Subject: Re: [Homebrew_PCBs] UV lamps?


  It looks like I'll be buying some lamps. What should I look for or look 
  out for in florescent types?
  Terry M



  Be sure to visit the group home and check for new Bookmarks and files:
  http://groups.yahoo.com/group/Homebrew_PCBs 



------------------------------------------------------------------------------
  Yahoo! Groups Links

    a.. To visit your group on the web, go to:
    http://groups.yahoo.com/group/Homebrew_PCBs/
      
    b.. To unsubscribe from this group, send an email to:
    Homebrew_PCBs-unsubscribe@yahoogroups.com
      
    c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



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

At work, for exposing printing plates we have a professional vacuum UV 
exposure table.  This uses a few dozen bulbs very close to the work. 
Isn't this the ideal situation for PCB too?

Earl T. Hackett, Jr. wrote:
> I'd recommend a single bulb fixture - the smallest you can get a lamp for - and

G'day Jason,
My understanding of it is that you need to have collimated light, i.e. all
light rays are coming vertical to the artwork so that it does not go under
the edges of the artwork.
This is the reason that a negative should be placed with the emulsion on the
PCB to reduce any chances of the light going under the edges.

I saw somewhere where they used an egg-crate diffuser (from a flourescent
light fitting) painted matt black, to collimate the light. This meant a
reduction in effective light output but a cleaner image.

Cheers
Brian

-------Original Message-------
 
From: Homebrew_PCBs@yahoogroups.com
Date: 01/24/05 12:20:04
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] UV lamps?
 

At work, for exposing printing plates we have a professional vacuum UV 
exposure table.  This uses a few dozen bulbs very close to the work. 
Isn't this the ideal situation for PCB too?

Earl T. Hackett, Jr. wrote:
> I'd recommend a single bulb fixture - the smallest you can get a lamp for
- and 





Be sure to visit the group home and check for new Bookmarks and files:
http://groups.yahoo.com/group/Homebrew_PCBs 




Yahoo! Groups Links

To visit your group on the web, go to:
http://groups.yahoo.com/group/Homebrew_PCBs/
  
To unsubscribe from this group, send an email to:
Homebrew_PCBs-unsubscribe@yahoogroups.com
  
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 


 

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

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

From: "Brian Clancy" <bclancy1@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, January 24, 2005 5:26 AM
Subject: Re: [Homebrew_PCBs] UV lamps?


>
>
> G'day Jason,
> My understanding of it is that you need to have collimated light, i.e. all
> light rays are coming vertical to the artwork so that it does not go under
> the edges of the artwork.
> This is the reason that a negative should be placed with the emulsion on 
> the
> PCB to reduce any chances of the light going under the edges.
>
> I saw somewhere where they used an egg-crate diffuser (from a flourescent
> light fitting) painted matt black, to collimate the light. This meant a
> reduction in effective light output but a cleaner image.

For home use, collimated light isn't really necessary, as most of us can't 
create high-resolution artwork that can make use of it. In fact, none of the 
low-cost UV exposure boxes that one can buy use it, they just have two or 
four tubes quite close to the PCB/artwork. I get quite good results with a 
couple of tubes about 15 cm from the PCB. Exposure is quite long at 13 
minutes, I keep meaning to add another two tubes.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller 



-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.7.1 - Release Date: 19/01/2005

I had a very unpleasant surprise with a commercial uv box ($600) that 
was unable to create SMD images on PCB. It turned out the collimation 
was teh issue. When I tried the same film ina collimated UV exposure 
box, the result was stunning. Later I tried to make SMD PCBs with a 
regular GE sunlight and it was almsot insanity. Times were allover 
the map due to heatup, images were fuzzy. Then I switched to Nuarc 
26, a comemrcial exposure unit. Voila, quality is beautiful. 
Few things matter:
1. Like you said, collimation
2. Source of light fluorescent or Hg
3. Timing
4. Repeatability (if Hg)

thinker tinker shows some detailed isntructions how to build it.

Mike


--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon.heller@d...> wrote:
> ----- Original Message ----- 
> From: "Brian Clancy" <bclancy1@b...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, January 24, 2005 5:26 AM
> Subject: Re: [Homebrew_PCBs] UV lamps?
> 
> 
> >
> >
> > G'day Jason,
> > My understanding of it is that you need to have collimated light, 
i.e. all
> > light rays are coming vertical to the artwork so that it does not 
go under
> > the edges of the artwork.
> > This is the reason that a negative should be placed with the 
emulsion on 
> > the
> > PCB to reduce any chances of the light going under the edges.
> >
> > I saw somewhere where they used an egg-crate diffuser (from a 
flourescent
> > light fitting) painted matt black, to collimate the light. This 
meant a
> > reduction in effective light output but a cleaner image.
> 
> For home use, collimated light isn't really necessary, as most of 
us can't 
> create high-resolution artwork that can make use of it. In fact, 
none of the 
> low-cost UV exposure boxes that one can buy use it, they just have 
two or 
> four tubes quite close to the PCB/artwork. I get quite good results 
with a 
> couple of tubes about 15 cm from the PCB. Exposure is quite long at 
13 
> minutes, I keep meaning to add another two tubes.
> 
> Leon
> --
> Leon Heller, G1HSM
> http://www.geocities.com/leon_heller 
> 
> 
> 
> -- 
> No virus found in this outgoing message.
> Checked by AVG Anti-Virus.
> Version: 7.0.300 / Virus Database: 265.7.1 - Release Date: 
19/01/2005

Leon Heller wrote:
> 
> 
> For home use, collimated light isn't really necessary, as most of us can't 
> create high-resolution artwork that can make use of it. In fact, none of the 
> low-cost UV exposure boxes that one can buy use it, they just have two or 
> four tubes quite close to the PCB/artwork. I get quite good results with a 
> couple of tubes about 15 cm from the PCB. Exposure is quite long at 13 
> minutes, I keep meaning to add another two tubes.
> 


I agree, the level of collimation depends on the resolution required. 
However I found the artwork produced by inkjet printers has sufficient 
high resolution to require a collimated light source to get the most out 
of the printer. For standard 0.35mm (1.3mills) dry film photoresists and 
traces/spaces <= 0.3mm (12mils) then a collimated light source should be 
used. At times I've needed to put a 0.18mm (7mil) trace between a two 
pads on a 1.27mm pitch SOP package. At this detail, the developing and 
etching steps can just as easily cause problems.

In general the smaller the features on the PCB the more attention must 
be paid to each step of the PCB processs. They all come into play when 
the detail goes up.

The need for collumination depends upon the spaces you are trying to maintain.  If you are shooting for less than 5 or 6 mils it's important.  If your exposure time is longer that 1 minute (I didn't like to see it longer than 30 seconds) don't worry about collumination, get more lamps.  You can overcome poor columination with intensity.  The old Scanex's had crappy columination, but the effective exposure time was around 5 seconds and they worked pretty well.
  ----- Original Message ----- 
  For home use, collimated light isn't really necessary, as most of us can't create high-resolution artwork that can make use of it. In fact, none of the low-cost UV exposure boxes that one can buy use it, they just have two or four tubes quite close to the PCB/artwork. I get quite good results with a couple of tubes about 15 cm from the PCB. Exposure is quite long at 13 minutes, I keep meaning to add another two tubes.




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

Earl T. Hackett, Jr. wrote:

> The need for collumination depends upon the spaces you are trying to maintain.  If you are shooting for less than 5 or 6 mils it's important.  If your exposure time is longer that 1 minute (I didn't like to see it longer than 30 seconds) don't worry about collumination, get more lamps.  You can overcome poor columination with intensity.  The old Scanex's had crappy columination, but the effective exposure time was around 5 seconds and they worked pretty well.
>   ----- Original Message ----- 


Overall light energy and collumination are completely separate 
parameters with respect to photoresists. More photons simply means a 
faster photochemical reaction. Point blank range fluorescent tubes can 
expose in seconds, however light undercutting is terrible.

Adam

This is getting a bit off topic.

The comments below are close and when I started working with photoresists that was my opinion as well.  However, when we examined the results of resolution testing, the data showed there was something other than just columination and exposure at work.  Tests at DuPont showed that oxygen migration within the photo resist from under the opaque areas of the phototool had a major effect on resolution of the spaces.  Oxygen inhibits free radical polymerization.  High intensity light generates so many free radicals in the clear area of the phototool that dissolved oxygen is consumed almost instantly and polymerization proceeds quickly.  As oxygen migrates from under the opaque areas of the photo tool those areas loose the only thing that prevents polymerization.  Stray light from poor columination or reflection from the copper surface would initiate polymerization in what should have been shadowed areas.  If you get the clear areas polymerized quickly the dissolved oxygen doesn't have time to migrate and it prevents polymerization in areas of lower light intensity.  In other words, high intensity will overcome the effects of poor columinization.  The reverse is not necessairly ture because of scattered reflection from the copper surface.  This effect was demonstrated in dozens of production shops.  

However, this is really getting down into the weeds as most home brew folks don't have (or shouldn't have) the high intensity mercury arc lamps that are needed for fast exposure times.  Even though I have one in my shop I'm yet to turn it on because I have not yet installed sufficient protection from the radiation it will produce.  I'd rather develop a solid documented toner transfer process which will do everything I need than fuss around with high resolution photoresists.

  ----- Original Message ----- 
  From: Adam Seychell 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Tuesday, January 25, 2005 10:09 PM
  Subject: Re: [Homebrew_PCBs] UV lamps?


  >   ----- Original Message ----- 


  Overall light energy and collumination are completely separate 
  parameters with respect to photoresists. More photons simply means a 
  faster photochemical reaction. Point blank range fluorescent tubes can 
  expose in seconds, however light undercutting is terrible.

  Adam

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

I could have agreed with you before I tried the same inkjet printed 
film with fluorescent exposure box and Hg arc with nice collimation. 
When I saw a dramatic difference side by side between PCBs produced 
by both methods, the answer was obvious to me. Another aspect to 
watchfor is wavelength. Some arists use 420nm for their UV process 
(platinum) while Revlon is about 350nm if I remember correctly. Mike

Earl T. Hackett, Jr. wrote:
> This is getting a bit off topic.
> 
> The comments below are close and when I started working with photoresists that was my opinion as well.  However, when we examined the results of resolution testing, the data showed there was something other than just columination and exposure at work.  Tests at DuPont showed that oxygen migration within the photo resist from under the opaque areas of the phototool had a major effect on resolution of the spaces.  Oxygen inhibits free radical polymerization.  High intensity light generates so many free radicals in the clear area of the phototool that dissolved oxygen is consumed almost instantly and polymerization proceeds quickly.  As oxygen migrates from under the opaque areas of the photo tool those areas loose the only thing that prevents polymerization.  Stray light from poor columination or reflection from the copper surface would initiate polymerization in what should have been shadowed areas.  If you get the clear areas polymerized quickly the dissolved oxygen doesn't
 h
>  ave time to migrate and it prevents polymerization in areas of lower light intensity.  In other words, high intensity will overcome the effects of poor columinization.  The reverse is not necessairly ture because of scattered reflection from the copper surface.  This effect was demonstrated in dozens of production shops.  
> 
> However, this is really getting down into the weeds as most home brew folks don't have (or shouldn't have) the high intensity mercury arc lamps that are needed for fast exposure times.  Even though I have one in my shop I'm yet to turn it on because I have not yet installed sufficient protection from the radiation it will produce.  I'd rather develop a solid documented toner transfer process which will do everything I need than fuss around with high resolution photoresists.

The black-light blue mercury HID lamps (125W, 250W, and 400W) are sold for stage
lighting effects and don't put out the shorter wave UV. With columation in a decent
lightbox, fine traces and spacing are easy. I just made a 15cm x 15cm pcb with 12mil
tracks running along the length of it with no problem at all. And unlike toner
transfer, it was easy to get perfect registration for both sides. I'm using a
125 watt HID mercury blacklight in a cylindrical reflector, 60cm globe-pcb
spacing, and 90sec exposure time.

Earl T. Hackett, Jr. wrote:
> This is getting a bit off topic.
> 
> The comments below are close and when I started working with photoresists that was my opinion as well.  However, when we examined the results of resolution testing, the data showed there was something other than just columination and exposure at work.  Tests at DuPont showed that oxygen migration within the photo resist from under the opaque areas of the phototool had a major effect on resolution of the spaces.  Oxygen inhibits free radical polymerization.  High intensity light generates so many free radicals in the clear area of the phototool that dissolved oxygen is consumed almost instantly and polymerization proceeds quickly.  As oxygen migrates from under the opaque areas of the photo tool those areas loose the only thing that prevents polymerization.  Stray light from poor columination or reflection from the copper surface would initiate polymerization in what should have been shadowed areas.  If you get the clear areas polymerized quickly the dissolved oxygen doesn'
t have time to migrate and it prevents polymerization in areas of lower light intensity.  In other words, high intensity will overcome the effects of poor columinization.  The reverse is not necessairly ture because of scattered reflection from the copper surface.  This effect was demonstrated in dozens of production shops.  
> 

This is the first time I've heard of this effect on dryfilm resists. The 
question now remains, what is the speed the oxygen diffuses near the 
boundaries between the exposed and unexposed areas of resist. Obviously 
with perfect collimated light, then the limiting factor of resolution 
would be due to oxygen migration effect. But as you mention this can be 
reduced by faster exposures.  Without any numbers its impossible to know 
the amount of photoresists that gets polymerized beyond the opaque mask.
Are you saying that the oxygen migration is so significant that 
fluorescent tubes place at 5 cm distance with an exposure time of 20 
seconds will produce the similar light undercut to a 5 minute exposure 
of collimated light ?
My own experience does not show this to be true at all. The oxygen 
migration effect would appear to be insignificant when producing images 
with 8 mil tracks/spaces or larger. At 2 or 1 mils then it could be a 
different story.
In any event, the only situation a collimated light source would not 
provide noticeable improvement over non-collimated light source is when 
the oxygen migration effect becomes very appreciable.

G'day
I am starting to regret having mentioned collimated light. I have no
practical experience  of this except that by spacing the light source a
further 40mm from the artwork/PCB you get  less furriness of the image. 
The reference I saw (I don't recall where) used a flourescent fitting
eggcrate diffuser (which were quite common in earlier times) about 1.5 to
2cm spacing and painted these matt black to prevent reflections. This gives
an almost collimated light source (separation from the surface of intent is
still mandatory) and supposedly perfect (if longer exposure) reproduction.
Cheers
Brian

-------Original Message-------
 
From: Homebrew_PCBs@yahoogroups.com
Date: 01/26/05 18:29:20
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] UV lamps?
 
Earl T. Hackett, Jr. wrote:
> This is getting a bit off topic.
> 
> The comments below are close and when I started working with photoresists
that was my opinion as well.  However, when we examined the results of
resolution testing, the data showed there was something other than just
columination and exposure at work.  Tests at DuPont showed that oxygen
migration within the photo resist from under the opaque areas of the
phototool had a major effect on resolution of the spaces.
snip> 

This is the first time I've heard of this effect on dryfilm resists. The
question now remains, what is the speed the oxygen diffuses near the
boundaries between the exposed and unexposed areas of resist. 
snip
Be sure to visit the group home and check for new Bookmarks and files:
http://groups.yahoo.com/group/Homebrew_PCBs 






Yahoo! Groups Links

To visit your group on the web, go to:
http://groups.yahoo.com/group/Homebrew_PCBs/
  
To unsubscribe from this group, send an email to:
Homebrew_PCBs-unsubscribe@yahoogroups.com
  
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 


 

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

Earl T. Hackett, Jr. wrote:
> This is getting a bit off topic.
> 
> The comments below are close and when I started working with photoresists that was my opinion as well.  However, when we examined the results of resolution testing, the data showed there was something other than just columination and exposure at work.  Tests at DuPont showed that oxygen migration within the photo resist from under the opaque areas of the phototool had a major effect on resolution of the spaces.  Oxygen inhibits free radical polymerization.  High intensity light generates so many free radicals in the clear area of the phototool that dissolved oxygen is consumed almost instantly and polymerization proceeds quickly.  As oxygen migrates from under the opaque areas of the photo tool those areas loose the only thing that prevents polymerization.  Stray light from poor columination or reflection from the copper surface would initiate polymerization in what should have been shadowed areas.  If you get the clear areas polymerized quickly the dissolved oxygen doesn't

h
>  ave time to migrate and it prevents polymerization in areas of lower light intensity.  In other words, high intensity will overcome the effects of poor columinization.  The reverse is not necessairly ture because of scattered reflection from the copper surface.  This effect was demonstrated in dozens of production shops.  
> 
> However, this is really getting down into the weeds as most home brew folks don't have (or shouldn't have) the high intensity mercury arc lamps that are needed for fast exposure times.  Even though I have one in my shop I'm yet to turn it on because I have not yet installed sufficient protection from the radiation it will produce.  I'd rather develop a solid documented toner transfer process which will do everything I need than fuss around with high resolution photoresists.

The black-light blue mercury HID lamps (125W, 250W, and 400W) are sold for stage
lighting effects and don't put out the shorter wave UV. With columation in a decent
lightbox, fine traces and spacing are easy. I'm using a 125 watt HID mercury blacklight
in a cylindrical reflector, 60cm globe-pcb spacing, and 90sec exposure time.

The commonest HID blacklight seems to be HPW125 (i got a GE one).

http://www.lamptech.co.uk/Spec%20Sheets/Philips%20HPW125.htm
http://www.lamptech.co.uk/Spec%20Sheets/Philips%20HPR125.htm

They need a ballast choke and PFC capacitor.

Russell,

Since you have mentioned teh word 'columination' so many times, I did 
some checking and yes, there is a word 'columination' but the the 
effect that matters to nice UV exposures is called 'collimation'. 
Just to set the record straight and yes it is a full moon.  Mike



--- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@n...> 
wrote:
> Earl T. Hackett, Jr. wrote:
> > This is getting a bit off topic.
> > 
> > The comments below are close and when I started working with 
photoresists that was my opinion as well.  However, when we examined 
the results of resolution testing, the data showed there was 
something other than just columination and exposure at work.  Tests 
at DuPont showed that oxygen migration within the photo resist from 
under the opaque areas of the phototool had a major effect on 
resolution of the spaces.  Oxygen inhibits free radical 
polymerization.  High intensity light generates so many free radicals 
in the clear area of the phototool that dissolved oxygen is consumed 
almost instantly and polymerization proceeds quickly.  As oxygen 
migrates from under the opaque areas of the photo tool those areas 
loose the only thing that prevents polymerization.  Stray light from 
poor columination or reflection from the copper surface would 
initiate polymerization in what should have been shadowed areas.  If 
you get the clear areas polymerized quickly the dissolved oxygen 
doesn't
> 
> h
> >  ave time to migrate and it prevents polymerization in areas of 
lower light intensity.  In other words, high intensity will overcome 
the effects of poor columinization.  The reverse is not necessairly 
ture because of scattered reflection from the copper surface.  This 
effect was demonstrated in dozens of production shops.  
> > 
> > However, this is really getting down into the weeds as most home 
brew folks don't have (or shouldn't have) the high intensity mercury 
arc lamps that are needed for fast exposure times.  Even though I 
have one in my shop I'm yet to turn it on because I have not yet 
installed sufficient protection from the radiation it will produce.  
I'd rather develop a solid documented toner transfer process which 
will do everything I need than fuss around with high resolution 
photoresists.
> 
> The black-light blue mercury HID lamps (125W, 250W, and 400W) are 
sold for stage
> lighting effects and don't put out the shorter wave UV. With 
columation in a decent
> lightbox, fine traces and spacing are easy. I'm using a 125 watt 
HID mercury blacklight
> in a cylindrical reflector, 60cm globe-pcb spacing, and 90sec 
exposure time.

> 
> The commonest HID blacklight seems to be HPW125 (i got a GE one).
> 
> http://www.lamptech.co.uk/Spec%20Sheets/Philips%20HPW125.htm
> http://www.lamptech.co.uk/Spec%20Sheets/Philips%20HPR125.htm
> 
> They need a ballast choke and PFC capacitor.

Firstly, thanks to everyone who replied and a special thanks to those 
that also supplied URLs.
I'm basically screwed. My toner transfer isn't working a hundred 
percent and several papers were tried along with times and temperatures 
in a press and each had their own peculiar problem. The number 1 
problem is board cleaning followed by toner line edges that "wobble". 
It'll work, eventually. (See "Three Foot Rule", below.)
The UV lamp question was sort of answered but I still don't know 
whether to get a bulb or a tube. Around here, there's a where question 
as well.
The hp-1300 printout on tracing paper amounts to a dirty gray instead 
of an opaque black and I'm willing to bet the light will go right on 
through.
A copier tech said I needed a printer that used toner and developer for 
a true opaque black.
Let me take a moment here to introduce you to the "Three Foot Rule".
Go right up to your broken down car or crappy printer or whatever you 
have that doesn't work. Back off exactly three feet. No more, no less. 
Now take out your wallet and throw money at it until it works.
Lamps, printers. TT papers or films. Opaque artwork. It ain't happening 
yet.
Terry M

Terry Mickelson wrote:
> Firstly, thanks to everyone who replied and a special thanks to those 
> that also supplied URLs.
> I'm basically screwed. My toner transfer isn't working a hundred 
> percent and several papers were tried along with times and temperatures 
> in a press and each had their own peculiar problem. The number 1 
> problem is board cleaning followed by toner line edges that "wobble". 
> It'll work, eventually. (See "Three Foot Rule", below.)
> The UV lamp question was sort of answered but I still don't know 
> whether to get a bulb or a tube...

As long as the ink on the film is tight against the resist, close
tubes are ok. The celophane plastic on dry film resist is about 0.4mil
thick, so undercutting due to light coming in at 45degrees still
doesn't affect an 8mil track much.

The effect of this undercutting light is that where edges end up
after etching is highly variable on the various degrees of exposure,
developing, and etching used.

With a collimated light source and decent film printout, you could
expose for 30secs or 5mins and still get tracks with little width
variation.

HID lamps need 2-3mins to warm up, and once switched off, won't
switch on again until after cooling for 5mins. Tubes are instant.
HID lamps are higher power in a small space, so they're more like
a point source and are much easier to use with a decent large
reflector. You can use one tube and a large reflector, but a
24" tube is only 20 watts. So: close tubes and consistant
timing to get good results, or a distant and focused HID globe
to get good consistent results with non critical timing.

I can also use films with the ink away from the copper (a film
printed without mirroring by mistake) and still get sharp traces.
Close tubes give very blurry traces.

My 125W HID box doesn't have enough power to do spray-on PRP
resist in 10-15mins, so i need to use the 4-tube fluoro box
for that. I haven't used prp for a while.

Go to the kids toys section of your favorite store and try to find 
miniature plastic cloths-pins. These are about 1.25 inches long and 
come in many colors. Drill from the clip end lengthwise through the 
cloths-pin so the edge of this newly made hole just shows up in the 
notch that's a quarter inch from the clip end. Do the same for the 
other side. Push a length of reasonably stiff wire into each of these 
holes so that a bit of the wire's edge shows up in the notch on each 
side. Use a pair of tweezers to put the smt part in the notch that's 
edged with these two wires while holding the cloths-pin open. Let the 
cloths-pin close and the smt part is tightly held in place while the 
wires allow a connection to the measurement set. This system works well 
on the 1206 size but not much smaller.
Terry M