Ron Amundson wrote:
> Its a dry film negative acting materal. Please see
> http://www.kepro.com/cprecut.htm for details.
>
thanks, yep the "DF" sounds similar to what I and most PCB
manufactures use.
> How do you apply your own dryfilm, do you have a laminator, and if so how
> big.. I can only buy it in huge rolls, and I'm worried about its shelf life
> expiring. Or are you indicating that the shelf life starts once its applied?
>
No, the shelf life I was talking about was only after being applied to
the board. I don't know the shelf life of the dryfilm at room temp. It
releases a smell so my guess something is evaporating and will
eventually cause problems. I store the roll in the fridge and haven't
notices any degradation of the 1 year I've had it.
I bought some from a guy who manufactured PCBs and he sold be the last
20 metres off two old rolls. Try contacting any PCB fabricators near
your area.
Applying the film is a problem in itself. I spent lots of time
experimenting before I gould even get usable result. I build a device
that has two rubber rollers (old ink printing rollers) and I roll the
film on the cleaned PCB while wet with distilled water. I then heat
the board in the oven at 80C° for 5 min and that fixes the film.
There are other techniques that have been posted on the group before.
Do a search in yahoo groups web site for past posts.
> I like the idea of your concept of appying the film one day and processing
> the boards the same day. It would alleviate lots of problems.
>
> Thanks
> Ron
> ----- Original Message -----
> From: "Adam Seychell" <adam_seychell@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, January 21, 2003 7:29 PM
> Subject: Re: [Homebrew_PCBs] Ferric Chloride
>
>
>
>>I once tried to built a bubble agitated developer but found the
>>bubbles could not reliably remove the dry-film from the board. In the
>>end I found best results using something similar to what Tom described
>> with the brush.
>>I also agree with Tom that you could be suffering dry-film residue,
>>which is an invisible scum left behind after developing and is
>>impermeable to the etchant. I am only familiar with negative dryfilm,
>>are you sure the boards are this film or is it positive pre coated PCB
>>material often sold at hobby shops ?
>>The way to check if you have a residue problem is after about 1 minute
>>in the etchant you should see the copper turn matte pink. If it still
>>shows shinny scrubbing marks then its dry-film scum. This happens when
>>the dry film has been on the board longer than a few weeks. I have
>>some stuff that's over a year old and is a problem to develop. The way
>>to develop these boards is to extend the developing time (brushing
>>over the board for upto 3 minutes). I put it in the etcher and if the
>>copper doesn't become matte pink over the entire board then I take it
>>back to the developer and brush over it for another minute. The second
>>pass usually gets it all. I apply my own dry-film these days and
>>develop the board the same day so I never have residue problems.
>>
>>Ron Amundson wrote:
>>
>>>I'll give the brush solution a try tomorrow. As I purchase my boards pre
>>>laminated with dry film, I'm sure cleanliness is not the issue, but
>>>underdeveloped dry film resist probably is.
>>>
>>>I do my developing in a tray with agitation too, looks like I'll need to
>>
> set
>
>>>up a simple to do spraying.
>>>
>>>Thanks
>>>Ron
>>>----- Original Message -----
>>>From: <twb8899@...>
>>>To: <Homebrew_PCBs@yahoogroups.com>
>>>Sent: Tuesday, January 21, 2003 10:09 AM
>>>Subject: [Homebrew_PCBs] Ferric Chloride
>>>
>>>
>>>
>>>
>>>>Ron mentioned in a previous post that he was getting uneven etching
>>>>with ferric chloride. When this happens it's usually due to under
>>>>development of the photoresist. I am assuming that dry film resist is
>>>>being used. The best way to develop dry film is with a spray tank set
>>>>up with a 1% sodium carbonate (soda ash)solution. Find out how long
>>>>it takes to "break through" to bare copper and then go about that
>>>>same time again for final developing. For example if the bare copper
>>>>shows up in 1 minute then continue the process for an additional 1
>>>>minute and then you can etch.
>>>>
>>>>Another good idea is to make up a tray of weak etchant from a couple
>>>>of ounces of ferric chloride in one gallon of water. If a developed
>>>>board is put into this solution for a minute or so the areas that are
>>>>fully developed will turn a dark color and the under developed spots
>>>>will show bright copper. This will amaze you the first time you see
>>>>it because the panel still has some dry film "scum" on the surface
>>>>when the board looked like it was fully developed. If the board has
>>>>scum, just put back in the developer for a bit longer and try again.
>>>>When a uniform dark color appears across the entire surface you will
>>>>be ready for final etching and obtain excellent results.
>>>>
>>>>If developemnt is being done in a tray, try using a very soft
>>>>bristled brush to gently work the solution across the board surface.
>>>>This will help to break through any scum on the board. The bottom
>>>>line is that this scum must be removed or you will never obtain
>>>>uniform etching. Hope this idea helps out.
>>>>
>>>>Tom
>>>>
>>>>
>>>>
>>>>
>>>>Be sure to visit the group home and check for new Bookmarks and files:
>>>>http://groups.yahoo.com/group/Homebrew_PCBs
>>>>
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>>>>
>>>>
>>>>
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>>>
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>>>
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>>
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>>>
>>
>>
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