i would really try to use the photosensitive laquer which is developed with soda ash.
i think you can apply this without using the screen.
maybe spraying is an option.
then proceed it very like a normal pcb.
(someone sayd solder stop is simply the negative of the copper artwork - this is not true because you
want your tracks covered. but any pcb software should be able to produce it. if not make a layer with no
traces but (bigger) pads. invert and print.)
i don's see any advantage in using the screen print method where you have to make the screen first if
you can get laquer which already is photo sensitive. this would only add a unneccesary step?
or is there no photosensitive coating which doesn't need high power UV?
regards
stefan
23.05.2003 01:34:34, "twb8899" <
twb8899@...> wrote:
>I use a screen printed soldermask that is UV cured. There are many
>suppliers of this ink and mine is made by Taiyo. We make a silksceen
>using Autotype Five Star indirect film emulsion on a 180 mesh screen
>fabric. Aluminum frames should be used for best results since the
>wood types can't hold the required screen tension for very long.
>
>Taiyo also offers a liquid photo imageable mask. The circuit board
>is "flood coated" using a blank 110 mesh screen and then cured at 180
>degrees F until "tack free" but not fully cured. A film positive is
>then used to expose the required pattern. The exposed panel is
>developed in a 1% soda ash solution. After development the panel is
>baked at about 300 degrees F for 45 to 60 minutes.
>
>DuPont used to make a dry film solder mask. We used their 8140 series
>dry film solder mask but I don't think they make it any longer. The
>liquid photo imageable types have taken over the market. It's very
>difficult to apply these dry film masks without using a vacuum
>laminator. We never did care much for the results and this was after
>wasting $48,000 on a DuPont vacuum laminator. The liquid types work
>much better.
>
>The only time anyone really uses the dry film masks now days is when
>they need to "tent" or cover over drilled holes with the exposed mask
>which is rare. Dry film and liquid photo imageable solder mask both
>require a huge amount of UV power to expose them properly. We used an
>ORC 5 kW exposure unit for this purpose. It had water cooled lamps
>since the heat from the lamps could damage the panel being exposed.
>
>If the board gets too hot during exposure the film photo tool will
>stick to the panel and make a big mess. By water cooling the lamp
>only the UV light gets through and the films don't stick.
>
>I think the silk screen method would be the best way to go for the
>home shop. You can cure UV screen printed inks with a mercury vapor
>lamp or just print the two part epoxy solder mask that is cured in a
>regular oven.
>
>Tom
>
>--- In Homebrew_PCBs@yahoogroups.com, "Zoran A. Scepanovic"
><zasto@y...> wrote:
>> Hello Markus,
>>
>> 22. May 2003, 22:35:57, you wrote:
>>
>> MZ> Hi Marty & Steve
>>
>> MZ> Thanks for the pointers. I'm willing to take some effort to get
>a real
>> MZ> solder stop mask.
>>
>> MZ> @Marty - I would be especialy interested how the dry film
>solder mask
>> MZ> technique works. I'm ready to let some dollars roll. I usually
>don't
>> MZ> need a solder stop mask since I'm hand soldering my prototypes,
>but
>> MZ> there are ocasions where I must create a prototype in a short
>time
>> MZ> that should look like one made in a board house and where time
>does
>> MZ> not allow to have it made externally. Could you therefore
>elaborate a
>> MZ> bit on how this is done, what equipement is needed, what a
>simple one
>> MZ> would aproximately cost and possibly where to get it?
>>
>> MZ> @Steve - thanks for the pointers. I defniately will go through
>them.
>>
>> MZ> Markus
>>
>> www.thinktink.com
>>
>> This is the place where you can spend some of your $$
>>
>> A little bit more at:
>>
>> http://www.thinktink.com/stack/volumes/volvi/pholam.htm
>>
>>
>> --
>> Best Regards,
>> Zoran
>> mailto:zasto@y...
>
>
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