Spin coating works well. I used a commercial spin coater for small boards.
On Wed Dec 29th, 2010 9:49 PM EST Donald H Locker wrote:
>How about an isolation process, but etch the unwanted copper away instead of mechanically milling it? The laser would only need to remove sufficient resist to form the isolation channels in that case. A very small amount.
>
>Donald.
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>----- Original Message -----
>
>> From: kabowers@...
>> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
>> Sent: Wednesday, December 29, 2010 9:28:09 PM
>> Subject: Re: [Homebrew_PCBs] Re: Alternate Masking Materials (CO2 Laser)
>>
>> On Wed, 29 Dec 2010 21:12:46 -0600, you wrote:
>>
>> >
>> > I ran an epilog 100 watt machine in the late 90's, basically had
>> it
>> >dropped in my lap at my job. During initial testing I even engraved
>> 1/8"
>> >lettering into a fig newton. This is exactly the sort of project I'd
>> have
>> >been given then.
>> >
>> > The answers to your question may be approaching this from the
>> wrong
>> >direction.
>> >
>> >> Question is: What could easily be used to coat a copper clad board
>> that
>> >> will be resistant to the etchant (pick your flavor).
>> >
>> > I didn't send anything to be etched, but guys (& gals?), just
>> take
>> >the question straight:
>> >
>> > What's the easiest etching resist to apply?
>> >
>> > It doesn't have to be a photo-resist, just something that will
>> live
>> >through the etching process - an etch-block. Laquer? Auto primer?
>> Asphalt?
>> >
>> > Once John applies it, then he can see what power and speed is
>> >required to reliably remove it. Even if it's a spray-on that tends to
>>
>> >run, as long as it's not fused glass the laser should be able to
>> remove
>> >it. He just seems to be looking for the easiest one to apply to the
>> board.
>> >
>> >>There also seems to be a widespread want of something better, but I
>> >>haven't seen any solutions yet (still digging).
>> >
>> > Something better/easier than spraying or brushing it on? Of
>> course
>> >there's dipping, but that's no better. Some sort of tape maybe? Is
>> there
>> >a tape that will survive a trip through an etching bath? Of course,
>> then
>> >there's the difference between cleanly ashing the tape (raster
>> cut...)
>> >and having to edge cut it all and hand-strip it. If any remaining
>> >particles are small enough the etchant will undercut them, so there's
>> a
>> >point where they'll be negligible.
>> >
>> > yeah, my kinda problem... Oh, and feeding the machine CorelDraw
>>
>> >files worked much better than AutoCad files, I finally ended up just
>>
>> >redrawing everything in CorelDraw (true single lines).
>> >
>> >
>> >
>> >------------------------------------
>> >
>> Could you maybe do an addictive process?
>>
>> I wonder what would happen if you spread a film of loose toner over
>> the board and then used the laser to melt it where you wanted traces.
>>
>> Then dust the board off and etch. Might want a second heating with a
>> high
>> intensity lamp or some such to more firmly fuse the toner to the
>> copper.
>>
>> I suspect this type of process would require a lot less energy than
>> vaporizing
>> something. It would also get away from possible problems of the copper
>> reflecting
>> the laser beam back into the laser and damaging it. IIRC copper is a
>> really
>> great reflector of infrared energy.
>> Keith Bowers WB4LSJ- Thomasville, NC
>>
>>
>>
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