Homebrew PCBs

The SEM images are great.  I'm left wondering what the time frame is
regarding the oxygen exposure to resist.  Minutes, hours?  I suppose the
oxygen contamination issue is large enough where it is better to leave the
cover sheet on and accept the more diffused and less collimated light?

Jeff


-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of Todd F. Carney
Sent: Sunday, January 13, 2013 8:38 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] photoresist application

On Sun, Jan 13, 2013 at 5:19 PM, Todd F. Carney <k7tfc@...> wrote:

> The cover sheet protects the resist from oxygen and from oxidizing the
> "free radicals" on which the photo-polymers depend. Here is an excellent
> document from DuPont on this:


Sorry, Folks. Wrong URL for the DuPont document. Here's the right one:

http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT1
207.pdf

73,

Todd
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K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
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QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design



>
>
http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/techtalk/TT1
007.pdf
>
> You will note that from an optical standpoint, leaving the cover sheet on
> is not optimum as it inevitably degrades the sharpness of the image. This
> is one reason why commercial or professional exposure units use arc light
> or a similar "point source" instead of diffused light like we home brewers
> use almost exclusively. Actually, for the stuff we typically do, the
> difference would probably never be noticed.
>
> 73,
>
> Todd
>
>
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> K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
>
>
----------------------------------------------------------------------------
--------
> QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
>
>
> On Sun, Jan 13, 2013 at 3:58 PM, Jeff <jeff.heiss@...> wrote:
>
>> **
>>
>>
>> Photoresist is shipped with a clear protective covering film on the top
>> and bottom. The covering film is removed by the user before the
photoresist
>> is applied. A comment by a poster in a forum says the top covering should
>> be kept on during exposure and removed before developing. Is that true?
Why
>> is that?
>>
>> "Note that the dry film resist should be exposed with the cover sheets
>> on, and then held in a dark place for 15 minutes before removing the
cover
>> sheets and developing."
>>
>>
http://www.electro-tech-online.com/general-electronics-chat/14427-photoresis
t-pcb-etching-process.html
>>
>> Jeff
>>
>>  
>>
>
>


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



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