Homebrew PCBs

> > > Andrewm wrote:
 
> Fuji Xerox Docucentre C4xx.
 
> I can hold a print out up to the window that
> faces kangaroo point if you have a good pair
> of binoculars.
>
Andrew,
Sorry, left the Zeiss's down on the boat!
Docucentre!! you must be a lawyer!! Only lawyers can afford things like that!!

Tell us more about the UV box.
Board size handling?
Is it necessary to worry about colimation?
Timer?
Exposure time?
Tube make and model?
General dimensions?
Home built or commercial?
Regards
John C

> > > > Andrewm wrote:
> > > > Fuji Xerox Docucentre C4xx.

> > Andrewm wrote:
> > I can hold a print out up to the window that
> > faces kangaroo point if you have a good pair
> > of binoculars.
> >

> John Craddock wrote:
> Sorry, left the Zeiss's down on the boat!
> Docucentre!! you must be a lawyer!! Only
> lawyers can afford things like that!!

Not a lawyer but almost as bad :P
 
> Tell us more about the UV box.

Kalex thing.

> Board size handling?

Um - about a big as a large briefcase.

Larger than A4.

> Is it necessary to worry about colimation?

Some people say no.  I am going to throw
away the Kalex box and make my own.  I don't
beleive collimation is critical - but I do
think that uniformity IS.  The kalex box
has light and dark patches.  When using the
little HP4000 at home for photo tools the
difference in exposure on the dark and light
areas is enough to cause some concern.

Using the car priced fuji/xerox thing at
work here there is not problem at all.

The laser plotter shoudl improve this as
well.  But no harm in making a new UV box
with better uniformity.

> Timer?

Built in thing.  I will make an atmel thing
with an LCD for the new one.

> Exposure time?

About 100 seconds.  The tubes are getting old.

I use Kinsten.  Dupont or roll your owns
woudl of course be different.

> Tube make and model?

Generic Black Blues.  I have priced new tubes
from Cetnal over on compton road (near Ikea
on the southside)

> General dimensions?
> Home built or commercial?

As stated above.  Kalex thing you can find on
the web.

The new one will be loosly based on the thing
from think'n'tink dot com.

I can make you up one as well while I am at
it if you shell up for the invoice price of
the tubes and ballasts.   I will dig out
the price I got from the place at Compton Rd
Kigston if you like.

>The kalex box has light and dark patches. 

Tubes are probably spaced too far apart. I started with this;

http://www.pbase.com/eldata/image/52324065

Then went to this to ensure that would never be a problem;

http://www.pbase.com/eldata/image/52321530

I'm not a fan of UV tubes as you can see. In fact the only UV tube 
here is in a 28 year old EPROM eraser.

--- In Homebrew_PCBs@yahoogroups.com, "Andrew" <andrewm1973@...> wrote:
>

> > Me wrote:
> >The kalex box has light and dark patches. 

> Tubes are probably spaced too far apart.

My guess too.
 
> I started with this;
> http://www.pbase.com/eldata/image/52324065
> Then went to this to ensure that would never
> be a problem;
> http://www.pbase.com/eldata/image/52321530

Now that would have to be pretty even
illumination
 
> I'm not a fan of UV tubes as you can see.
> In fact the only UV tube here is in a 28
> year old EPROM eraser.

AFAIK there are 3 common types of UV tube.

The generic part numbers for these start
GT, BL and BB.  That is for

GT - Germicidal  = Nasty UV
BL - Black light = Bug zappers
BB - Black blue  = Disco lights

The two second sort (BL and BB) are abouts
the peak sensitivity of UV resist (at least
kinsten brand)

With some playing I did with them the
exposure times with normal white fluros
was significantly longer.  Theory I have
read says that a shorter exposure leads
to better line deffinition.  This may be
bunk - I don't know.  The white tubes
doubling as a light box is a good idea
if you do go that way.

I woudl imagine the number of tubes
Derek has would lead to pretty short
exposures anyways.

BTW - the GT tubes are no good for PCB
exposure either.  They are too short a
wavelength. They are only good for
EPROMS, killing bacteria, making ozone
and going blind.

BL and BB tubes can obviously be looked
at with no ill effects apart from those
you would get from drinking to much while
sitting on the patio or at the disco.

> -----Original Message-----
> From: derekhawkins [mailto:eldata@...]
> Sent: 15 September 2006 12:37
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: UV exposure boxes
> 
> Then went to this to ensure that would never be a problem;
> 
> http://www.pbase.com/eldata/image/52321530
> 
> I'm not a fan of UV tubes as you can see. In fact the only UV tube 
> here is in a 28 year old EPROM eraser.

Thanks for sharing that information Derek.
A couple of questions if I may.
Can you tell me the distance from the top of the tubes to the top of the exposure glass  pane?
Are the tubes 18" of 2'?
Are the tubes 1" or 1.5" diameter?
What is the tube centre to centre spacing?
TIA
John C

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

From: "derekhawkins" <eldata@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, September 15, 2006 3:37 AM
Subject: [Homebrew_PCBs] Re: UV exposure boxes


> >The kalex box has light and dark patches.
>
> Tubes are probably spaced too far apart. I started with this;
>
> http://www.pbase.com/eldata/image/52324065
>
> Then went to this to ensure that would never be a problem;
>
> http://www.pbase.com/eldata/image/52321530

I just use two tubes quite far apart, but the distance from the PCB is quite 
large giving uniform illumination.

Leon

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

From: "Leon Heller" <leon.heller@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, September 15, 2006 7:40 AM
Subject: Re: [Homebrew_PCBs] Re: UV exposure boxes


> ----- Original Message ----- 
> From: "Andrew" <andrewm1973@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Friday, September 15, 2006 4:22 AM
> Subject: [Homebrew_PCBs] Re: UV exposure boxes
>
>
>>> > Me wrote:
>>> >The kalex box has light and dark patches.
>>
>>> Tubes are probably spaced too far apart.
>>
>> My guess too.
>>
>>> I started with this;
>>> http://www.pbase.com/eldata/image/52324065
>>> Then went to this to ensure that would never
>>> be a problem;
>>> http://www.pbase.com/eldata/image/52321530
>>
>> Now that would have to be pretty even
>> illumination
>>
>>> I'm not a fan of UV tubes as you can see.
>>> In fact the only UV tube here is in a 28
>>> year old EPROM eraser.
>>
>> AFAIK there are 3 common types of UV tube.
>>
>> The generic part numbers for these start
>> GT, BL and BB.  That is for
>>
>> GT - Germicidal  = Nasty UV
>> BL - Black light = Bug zappers
>> BB - Black blue  = Disco lights
>>
>> The two second sort (BL and BB) are abouts
>> the peak sensitivity of UV resist (at least
>> kinsten brand)
>>
>> With some playing I did with them the
>> exposure times with normal white fluros
>> was significantly longer.  Theory I have
>> read says that a shorter exposure leads
>> to better line deffinition.  This may be
>> bunk - I don't know.  The white tubes
>> doubling as a light box is a good idea
>> if you do go that way.
>>
>> I woudl imagine the number of tubes
>> Derek has would lead to pretty short
>> exposures anyways.
>>
>> BTW - the GT tubes are no good for PCB
>> exposure either.  They are too short a
>> wavelength. They are only good for
>> EPROMS, killing bacteria, making ozone
>> and going blind.
>>
>> BL and BB tubes can obviously be looked
>> at with no ill effects apart from those
>> you would get from drinking to much while
>> sitting on the patio or at the disco.
>
> The germicidal tubes work fine for me.

Sorry, they are not GT (I used to use them for EPROMs) - they look like 
white fluorescent tubes.

Leon

--- derekhawkins <eldata@...> wrote:

> >The kalex box has light and dark patches. 
> 
> Tubes are probably spaced too far apart. I started with this;
> 
> http://www.pbase.com/eldata/image/52324065
> 

did you try to place a piece of that wobbly glass (bathroom window) on top of
the tubes to scramble the light?


__________________________________________________
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> >> Me wrote:
> >> BTW - the GT tubes are no good for PCB
> >> exposure either.  They are too short a
> >> wavelength. They are only good for
> >> EPROMS, killing bacteria, making ozone
> >> and going blind.
> >>
> >> BL and BB tubes can obviously be looked
> >> at with no ill effects apart from those
> >> you would get from drinking to much while
> >> sitting on the patio or at the disco.

> > Leon wrote:
> > The germicidal tubes work fine for me.

> Then Leon wrote:
> Sorry, they are not GT (I used to use them
> for EPROMs) - they look like white
> fluorescent tubes.

The ones that look white when they are turned
off are the BL (Black Light).

The ones that look purple when they are off
are BB (Black Light Blue).

The GT ones are clear when they are off.  I
think that the GTs are also not made from
normal glass as it blocks too much short UV.

GTs are also far too expensive.  I think I
priced replacement tubes for my eraser and
they where in the $70 area.  Hooray for flash
I say :D

I was told by someone that for PCBs BLs and
BBs are as good as each other.  BBs just
seem easier to find in AUS as straight tubes.

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

From: "Andrew" <andrewm1973@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, September 15, 2006 10:03 AM
Subject: [Homebrew_PCBs] Re: UV exposure boxes


>> >> Me wrote:
>> >> BTW - the GT tubes are no good for PCB
>> >> exposure either.  They are too short a
>> >> wavelength. They are only good for
>> >> EPROMS, killing bacteria, making ozone
>> >> and going blind.
>> >>
>> >> BL and BB tubes can obviously be looked
>> >> at with no ill effects apart from those
>> >> you would get from drinking to much while
>> >> sitting on the patio or at the disco.
>
>> > Leon wrote:
>> > The germicidal tubes work fine for me.
>
>> Then Leon wrote:
>> Sorry, they are not GT (I used to use them
>> for EPROMs) - they look like white
>> fluorescent tubes.
>
> The ones that look white when they are turned
> off are the BL (Black Light).
>
> The ones that look purple when they are off
> are BB (Black Light Blue).
>
> The GT ones are clear when they are off.  I
> think that the GTs are also not made from
> normal glass as it blocks too much short UV.

I think that is the case. That's why ordinary glass is OK for UV exposure 
boxes, it doesn't absorb the longer wavelength UV. I used Perspex at first, 
thinking it mattered.

Leon

On Fri, 15 Sep 2006 13:51:20 +0200, Leon Heller  
<leon.heller@...> wrote:

>
> I think that is the case. That's why ordinary glass is OK for UV exposure
> boxes, it doesn't absorb the longer wavelength UV. I used Perspex at  
> first,
> thinking it mattered.
> Leon


isn't perspex much less transparent to uv than window glass?
I'm not sure at which wavelengths though.

ST

I've used 1/2" thick acrylic with a regular gas discharge desk lamp, the 
type with a magnifying glass in the middle. I don't recall the exact 
exposure times but it was only a few minutes. I wasn't in a hurry so it 
didn't matter much to me how long it took.

As an aside, I had been experimenting with toner transfer but that was 
just taking too much time to be worthwhile. I reverted to UV based 
etching and that worked much better for me. Of course the board material 
is much more expensive and UV exposure isn't trivial either but at least 
I got that to work :)

   Sander

Stefan Trethan wrote:

> On Fri, 15 Sep 2006 13:51:20 +0200, Leon Heller  
> <leon.heller@...> wrote:
>
>   
>> I think that is the case. That's why ordinary glass is OK for UV exposure
>> boxes, it doesn't absorb the longer wavelength UV. I used Perspex at  
>> first,
>> thinking it mattered.
>> Leon
>>     
>
>
> isn't perspex much less transparent to uv than window glass?
> I'm not sure at which wavelengths though.
>
> ST
>
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> If Files or Photos are running short of space, post them here:
> http://groups.yahoo.com/group/Homebrew_PCBs_Archives/ 
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
>

>I woudl imagine the number of tubes
>Derek has would lead to pretty short
>exposures anyways.

2.5 minutes per side for double sided boards when they're new. But I 
overexpose them to 3.5 minutes to remove the inkjet ragged edges. 
Don't try that with laser artwork, you shouldn't have to anyway.   
Single sided boards only take 90 seconds, seems to be a different 
resist formulation.

--- In Homebrew_PCBs@yahoogroups.com, "Andrew" <andrewm1973@...> wrote:
>

>Can you tell me the distance from the top of the tubes to the top 
>of the exposure glass pane?

1.5". It's not glass BTW, it's non-UV blocking plexiglass.

> Are the tubes 18" of 2'?

They are 18" 15W tubes.

> Are the tubes 1" or 1.5" diameter?

1"

> What is the tube centre to centre spacing?

1.5"

Some notes:

1. Use a contact frame instead of weights especially when using 
something like plexiglass instead of real glass and especially in 
the absence of collimation.

2. If using plexiglass, make sure it's the type that doesn't block 
UV rays. 


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

>did you try to place a piece of that wobbly glass (bathroom window) 
>on top of the tubes to scramble the light?

That's not a good idea for an exposure box. Just the opposite 
(collimation) is recommended.


--- In Homebrew_PCBs@yahoogroups.com, "Herbert E. Plett" 
<cachureos@...> wrote:
>

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

From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, September 15, 2006 1:29 PM
Subject: Re: [Homebrew_PCBs] Re: UV exposure boxes


> On Fri, 15 Sep 2006 13:51:20 +0200, Leon Heller
> <leon.heller@...> wrote:
>
>>
>> I think that is the case. That's why ordinary glass is OK for UV exposure
>> boxes, it doesn't absorb the longer wavelength UV. I used Perspex at
>> first,
>> thinking it mattered.
>> Leon
>
>
> isn't perspex much less transparent to uv than window glass?
> I'm not sure at which wavelengths though.

It worked about the same for PCBs, I found.

Leon

>It worked about the same for PCBs, I found.

Don't know about perspex but on this side of the pond there can be at 
least two types of plexiglass from the same manufacturer. One 
states "Transparent to light" and the other states "Blocks UV rays" or 
something similar. Hardware stores (eg. Home Depot) normally have them 
displayed next to each other, so one should be careful in choosing the 
right one for an exposure box.

--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" <leon.heller@...> 
wrote:
>

On Fri, 15 Sep 2006 18:06:34 +0200, derekhawkins <eldata@...> wrote:

>
> Don't know about perspex but on this side of the pond there can be at
> least two types of plexiglass from the same manufacturer. One
> states "Transparent to light" and the other states "Blocks UV rays" or
> something similar. Hardware stores (eg. Home Depot) normally have them
> displayed next to each other, so one should be careful in choosing the
> right one for an exposure box.


You are probably talking about PC (polycarbonate, lexan) and PMMA (acrylic  
glass, plexiglass).

 From what i read polycarbonate is filtering out UV and PMMA is passing  
everything straight through.
I may be misinformed though.


ST

>From what i read polycarbonate is filtering out UV and PMMA is 
>passing everything straight through. I may be misinformed though.

Either can be formulated to block UV. 

====================================================================
Tuffak® XL Weatherable Polycarbonate Sheet

Tuffak® XL has a "built-in" UV barrier and is 100% polycarbonate.
================================================================snip


====================================================================
Plexiglas® UF-3, UF-4 and UF-5 Acrylic
Some applications, such as document and fine art preservation, call 
for a material that absorbs more ultraviolet (UV) energy than 
ordinary glass without absorbing visible light.

Plexiglas® G UF-3 and Plexiglas® MC UF-5 standard and non-glare 
acrylic sheet finishes filter out up to 99% of all UV rays, as well 
as some visible light
================================================================snip 



--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
>

On Fri, 15 Sep 2006 21:15:59 +0200, derekhawkins <eldata@...> wrote:

> Either can be formulated to block UV.

I think it is more like PMMA can be made to block UV (for example with  
special coatings).
I don't think polycarbonate can be made to allow UV to pass.
Again, not 100% sure.

ST

Stefan Trethan wrote:

> On Fri, 15 Sep 2006 21:15:59 +0200, derekhawkins <eldata@...> wrote:
> 
> 
>>Either can be formulated to block UV.
> 
> 
> I think it is more like PMMA can be made to block UV (for example with  
> special coatings).
> I don't think polycarbonate can be made to allow UV to pass.
> Again, not 100% sure.
> 
> ST
> 
> 

Not sure about polycarbonate, but when I used 2mm PMMA sheeting ("non UV 
blocking" type) for my first light box it took about twice as long to 
expose photoresist than it did after changing to standard 3mm window 
glass. There is nothing wrong with common window soda glass.
I know that the coated 0.20mm polyster films used for inkjet 
transparencies, also contribute significant UV absorbtion. It was a 
while since I did the test, but from memory the film almost doubled the 
exposure time.  Of course there is no way to get around this problem.

Conclusion: avoid PMMA if possible.

Adam