Synth-DIY Yahoo! Groups Archives

Thread

Solder mask

2006-02-04 by rmustakos

Does anyone have experience with, or know of, think sheet solder mask
that has adhesive on one side? I recall seeing a company that sold
rework equipment that sold small pieces made up for surface mount,
plccs, if I remember correctly. You put it over the pcb, squeegie
solder paste into the holes, wipe the excess off, put the ic into the
grooves and heat it. With something like this, even _I_ might be able
to reliably solder through-hole components!
Do any of you have any experience with this type of product for bga use?
Here is a page that does the same effect:
<http://www.midwestpcb.com/sales/kehoe/sipage1.html>
Thanks
Richard

Re: Solder mask

2006-02-04 by jcarlosmor

I think that the method you recall are far most complicated and prone
to failure than to apply a real soldermask. As you stated you have to
be very precise with the alignment and the squeguee. If you use a real
dry-film soldermask you only have to create your soldermask artwork and
align it over your bare copper pads. Once you are ok with the alignment
you only fix it with scoth tape and that is all. You only then expose,
develop, cure, and you can have any pitch that you want, even LQFP or
smaller.

Re: Solder mask

2006-02-05 by rmustakos

--- In Homebrew_PCBs@yahoogroups.com, "jcarlosmor" <jcarlosmor@...> wrote:

Show quoted textHide quoted text

>
> I think that the method you recall are far most complicated and prone
> to failure than to apply a real soldermask. As you stated you have to
> be very precise with the alignment and the squeguee. If you use a real
> dry-film soldermask you only have to create your soldermask artwork and
> align it over your bare copper pads. Once you are ok with the alignment
> you only fix it with scoth tape and that is all. You only then expose,
> develop, cure, and you can have any pitch that you want, even LQFP or
> smaller.
>

jcarlosmor,
When you say "real dry-film soldermask", you mean photo sensitive,
right? Where can it be had?
Thanks
Richard

Re: [Homebrew_PCBs] Re: Solder mask

2006-02-05 by Mike Young

----- Original Message -----
From: "rmustakos" <rmustakos@...>
> When you say "real dry-film soldermask", you mean photo sensitive,
> right? Where can it be had?

http://www.thinktink.com/stack/volumes/voli/store/specs/8130spec.htm, about
$3 to $5/sq.ft, depending on quantity ($240/80', or $200/40' x 12" rolls). A
group purchase makes sense. Do you think we can find 12 US list members to
split an 80' roll, for $30 each (to cover repackaging and shipping)?

Also, BGA is a bit more problematic because traces are usually run out
through micro-vias in 4- or 7-layer boards. Soldermask is needed there to
prevent wicking away solder in the micro-vias. I don't expect our manual
processes can hold the required tolerances even if we were able to route
them on just 2 layers.

Re: Solder mask

2006-02-05 by jcarlosmor

http://www.thinktink.com/cgi-bin/cart.pl?db|photopolymers.dat|Soldermask

The price is very competitive, although the disavantage is that you
must buy a roll. I believe that this company makes a great service of
selling that medium size rolls, since the original roll from DuPont is
only available at 400 ft. and it only sells in a B2B service, not even
to individuals or homebrew makers.

Does anybody has purchased from thinktink in the past soldermask or
photoresist and laminate their own boards? If so, could you explain
your experiences?

Re: Solder mask

2006-02-06 by roel_cnc

--- In Homebrew_PCBs@yahoogroups.com, "jcarlosmor" <jcarlosmor@...> wrote:

Show quoted textHide quoted text

>
> http://www.thinktink.com/cgi-bin/cart.pl?db|photopolymers.dat|Soldermask
>
> The price is very competitive, although the disavantage is that you
> must buy a roll. I believe that this company makes a great service of
> selling that medium size rolls, since the original roll from DuPont is
> only available at 400 ft. and it only sells in a B2B service, not even
> to individuals or homebrew makers.
>
> Does anybody has purchased from thinktink in the past soldermask or
> photoresist and laminate their own boards? If so, could you explain
> your experiences?
>

as we speak about dry film soldermask and buying those,!
first of all it has a limmited time of use - shelf life is six months
from date of manufacture.
on this moment my film's are about one year old, and stil works fine
-brand is Dynachem®
Dynachem dm (soldermask) neet a strong vacuum unit for fine result
and 5000 (photopolymer)

My 2 cents

Roel