Homebrew PCBs

I have recently used some positive resist boards from eBay and am expereinceing 
exposure times of up to twice as long as the times it is taking for the positive 
resist boards bought from Circuit Specialists.  


Is this because they are old or defective?  

I have a UV exposure box and the eBay boards take 150 seconds and the new 
Circuit Specialists boards only take 80 seconds?  


Please tell me what you think?

Thanks, Tom

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On 14-04-11 20:11, Tom Biery wrote:
> I have recently used some positive resist boards from eBay and am expereinceing 
> exposure times of up to twice as long as the times it is taking for the positive 
> resist boards bought from Circuit Specialists.  
> 
> 
> Is this because they are old or defective?  
> 
> I have a UV exposure box and the eBay boards take 150 seconds and the new 
> Circuit Specialists boards only take 80 seconds?  
> 
> 
> Please tell me what you think?
> 
> Thanks, Tom


Old boards.

I have some scraps that I bought 3 years ago and they need 2.5+ times
longer exposure. But, I always buy fresh boards localy so scraps are
just for fun :)

- -- 
Best Regards,
Zoran A. \u0160\u0107epanovi\u0107
zastos@...
http://zastos.com
+381 63 609-993

- -..-
You never find the article until you replace it.
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On 14/04/2011 19:11, Tom Biery wrote:
> I have recently used some positive resist boards from eBay and am expereinceing
> exposure times of up to twice as long as the times it is taking for the positive
> resist boards bought from Circuit Specialists.
>
>
> Is this because they are old or defective?
>
> I have a UV exposure box and the eBay boards take 150 seconds and the new
> Circuit Specialists boards only take 80 seconds?

I've found that resist-coated boards I've bought sometimes aren't much 
use when they are more than six months old.

Leon
-- 
Leon Heller
G1HSM

I have bought photo-resist-board at Reichelt.de  Its Bungard. and on the boards is a label with 16-2-2013 
witch I guess means, it is perfect nearly one year ahead. 
alex

--- In Homebrew_PCBs@yahoogroups.com, Leon Heller <leon355@...> wrote:

>
> On 14/04/2011 19:11, Tom Biery wrote:
> > I have recently used some positive resist boards from eBay and am expereinceing
> > exposure times of up to twice as long as the times it is taking for the positive
> > resist boards bought from Circuit Specialists.
> >
> >
> > Is this because they are old or defective?
> >
> > I have a UV exposure box and the eBay boards take 150 seconds and the new
> > Circuit Specialists boards only take 80 seconds?
> 
> I've found that resist-coated boards I've bought sometimes aren't much 
> use when they are more than six months old.
> 
> Leon
> -- 
> Leon Heller
> G1HSM
>

On 15/04/2011 18:14, alex4459jopiklal44 wrote:
> I have bought photo-resist-board at Reichelt.de  Its Bungard. and on the boards is a label with 16-2-2013
> witch I guess means, it is perfect nearly one year ahead.


The problem might be caused by light getting through the back of the 
board, if they are not stored in light-proof packaging.

Leon
-- 
Leon Heller
G1HSM

My guess is, the photo sensitive coating of one manufacturer will vary from 
that of another.
If two formulae are not identical, the net result is, one will require 
longer exposure than the other. The same thing occurred in photography with 
many the different formulae printing paper and film speeds available.

Peter
Shetland

I dont know if anybody belive me ,when I say ,I have used a board with succes, that was about 10 years old..it was stored in a cellar with same temp all year  .SO think Leon has a point about light.
alex

--- In Homebrew_PCBs@yahoogroups.com, Leon Heller <leon355@...> wrote:

>
> On 15/04/2011 18:14, alex4459jopiklal44 wrote:
> > I have bought photo-resist-board at Reichelt.de  Its Bungard. and on the boards is a label with 16-2-2013
> > witch I guess means, it is perfect nearly one year ahead.
> 
> 
> The problem might be caused by light getting through the back of the 
> board, if they are not stored in light-proof packaging.
> 
> Leon
> -- 
> Leon Heller
> G1HSM
>

> 
> The problem might be caused by light getting through the back of the 
> board, if they are not stored in light-proof packaging.
> 
> Leon
> -- 
> Leon Heller
> G1HSM
>
a second thought...hmm do you mean, through the copper ?? dont hope so :)
but I had a job where it was custom to store the boards in a refigerator
as the door was standing open in summer, there had come water on the boards..they did not work and they were new.. so from this, I think that moisture can get through the cover and maybe the humidity in air is the worst problem with storage.. not light-or temperatur differences ..but it was mainly the part had had water on the cover that was realy bad.
alex

On 16/04/2011 18:36, alex4459jopiklal44 wrote:
>
>
>>
>> The problem might be caused by light getting through the back of the
>> board, if they are not stored in light-proof packaging.
>>
>> Leon
>> --
>> Leon Heller
>> G1HSM
>>
> a second thought...hmm do you mean, through the copper ?? dont hope so :)
> but I had a job where it was custom to store the boards in a refigerator
> as the door was standing open in summer, there had come water on the boards..they did not work and they were new.. so from this, I think that moisture can get through the cover and maybe the humidity in air is the worst problem with storage.. not light-or temperatur differences ..but it was mainly the part had had water on the cover that was realy bad.

The copper is covered in black plastic. I meant light getting through 
the back of the board - FR4 is translucent.

Leon
-- 
Leon Heller
G1HSM