Homebrew PCBs

Hello,

Still hoping for some replies to my post about solder mask...

Thank you in advance,

Ballendo

On Thu, 25 Mar 2004 11:40:02 -0000, ballendo <ballendo@...> wrote:

> Hello,
>
> Still hoping for some replies to my post about solder mask...
>
> Thank you in advance,
>
> Ballendo
>

I have read about soldermask that is exposed and developed like
resist. sorry do not remember urls or names.
there was one german company making it also i think.

ST

you find results with
"l\ufffdtstoplack fotostrukturierbar" in german



ST

Stephan,

Thank you for the reply.

Yes, two types. LPI (Liquid Photo Imageable) and dry film.

LPI cannot "tent" (bridge) vias, which could mean you have solder 
under a SOIC--in the via. It's strength is that being liquid, 
it "fills" the entire "terrain" of the pcb very well.

Which is the downside of the dry film soldermask. Unless 
sophisticated techniques are used to bring it into full contact with 
the board, it can fail rather easily. It also may suffer during hot 
oil reflow operations, and wrinkle or rupture.

Both of these SM's are photoimageable, and process much like etch 
resist, with the added step of baking required for full soldermask 
standards compliance. 

As I said, we've got a couple of really decent ways to get the 
artwork image onto the board. And a couple decent ways to THP. And 
the toaster oven technique for part mounting works well, if care is 
used in the process.

Screen printing is cheap and easy to setup for component id, and bd 
legends... 

But lack of decent techniques/materials for soldermask is what 
separates our HB PCB's from the "real" ones, IMO... 

Ballendo

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:

> I have read about soldermask that is exposed and developed like
> resist. sorry do not remember urls or names.
> there was one german company making it also i think.
> 
> ST

On Thu, 25 Mar 2004 14:13:32 -0000, ballendo <ballendo@...> wrote:

> Stephan,
>
> Thank you for the reply.
>
> Yes, two types. LPI (Liquid Photo Imageable) and dry film.
>
> LPI cannot "tent" (bridge) vias, which could mean you have solder
> under a SOIC--in the via. It's strength is that being liquid,
> it "fills" the entire "terrain" of the pcb very well.
>

well, shouldn't it simply fill the via?
i would think if you paint the whole board the via gets filled,
and if you then expose/develop it is stays filled, or not?

i thought the areas getting the light will come off, is that wrong?

However this might be a problem with throughhole components, there is no 
way
getting light into the hole and then the paint out.. maybe
drilling them afterwards is a possibility.

I do not need soldermask right now (at least not with the effort of 
setting up
a photo process) so i don't know..

Just wanted to tell you what i know because you said nobody answers.
can't help you more with that, no experience with it.

ST

I now read you say screen printing is easy to do...

well, why don't you use a soldermask for screenprinting?
this german company also had this i think.

If the amount of paint is enough it will fill the via, if it is small
enough.

I do not like screenprinting... way too much steps..
(if you only make few boards which you mostly immediately populate manually
afterwards both things are not needed, component layout and soldermask).


good luck...

ST

for populating the board, its unnecessary.  But I like it even on one-
offs for labling connectors (particularly which wire goes where).  
Saves me looking up the schematic/layout.

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> 
> I now read you say screen printing is easy to do...
> 
> well, why don't you use a soldermask for screenprinting?
> this german company also had this i think.
> 
> If the amount of paint is enough it will fill the via, if it is 
small
> enough.
> 
> I do not like screenprinting... way too much steps..
> (if you only make few boards which you mostly immediately populate 
manually
> afterwards both things are not needed, component layout and 
soldermask).

> 
> 
> good luck...
> 
> ST

Hello,

My desire for it is less for me and more for my customers... (except 
for the real issues involved with semi-production smd's in the 
toaster oven when used without soldermask.)

Screen print and soldermask make the board look better, and can make 
it easier to charge more for the item. Expecially when the "item" is 
sold at a "board level"-- means no case or cover.

There are more than a few items which sell in a decent "yearly" 
volume, but at any given time only 1 or 2... So you either have to 
inventory a bunch of commercial pcb's--to get a decent price, OR you 
pay--and charge-- a higher price if you buy 'em as you go...

Ballendo

P.S. I actually kinda liked the green testors spray paint idea. But I 
don't think that's gonna work going through the oven process...

P.P.S. I saw a printer last night at a local electronics store that 
had a plastic carrier for printing directly onto cd's. That carrier 
could easily be made on a cnc machine, or modified to carry a board. 
Just gotta get the right goop(s) for the print head. Avecia has the 
goop, but they use the industrial style inkjet head. Been looking at 
the differences, and reading a lot of patents lately...

I'm thinking that a 500 buck pcb printer might be a hot seller... 
print resist,etch, print soldermask, print legends... DEFINITELY NEED 
TO make this happen... Combine that with the 500 buck drill and a 
whole lot of pcb protos get made<G>

--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
> for populating the board, its unnecessary.  But I like it even on 
one-
> offs for labling connectors (particularly which wire goes where).  
> Saves me looking up the schematic/layout.
> 
> --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
> <stefan_trethan@g...> wrote:
> > 
> > I now read you say screen printing is easy to do...
> > 
> > well, why don't you use a soldermask for screenprinting?
> > this german company also had this i think.
> > 
> > If the amount of paint is enough it will fill the via, if it is 
> small
> > enough.
> > 
> > I do not like screenprinting... way too much steps..
> > (if you only make few boards which you mostly immediately 
populate 

> manually
> > afterwards both things are not needed, component layout and 
> soldermask).
> > 
> > 
> > good luck...
> > 
> > ST

> I'm thinking that a 500 buck pcb printer might be a hot seller...
> print resist,etch, print soldermask, print legends... DEFINITELY NEED
> TO make this happen... Combine that with the 500 buck drill and a
> whole lot of pcb protos get made<G>

if you only print resist, nothing else it would find it's buyers for 500 
bucks..

look what professional mills (or even homebrew mills) cost and what 
quality they
produce... ok they can drill....

with some board houses 500 bucks are not many pcbs made..

ST