Homebrew PCBs

Tom,

Thanks for the info.

Do you know if it is possible to do the liguid photo imaged soldermask on a hobbiest scale? Could it be developed without using a spray tank, or is the spray tank necessary to get the right reaction speed for exposed vs unexposed mask. (IE, so the unwanted area is totally stripped before the remaining area is adversely affected.)

Paul 

----- Original Message ----
From: twb8899 <twb8899@...>
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, January 29, 2007 1:07:50 AM
Subject: [Homebrew_PCBs] Re: someone with dry film processing experience?









  


    
            --- In Homebrew_PCBs@ yahoogroups. com, Paul Atkinson <pma32904@.. .> wrote:

>

> I've used some of the Kepro pcb materials in the past. I still have

one of their hobbyist kits, but I expect it's exceeded it's shelf

life. I wouldn't mind having some more of their presensitized PCB

stock if it's available and reasonable.

> 

> Concerning the dry film processing, you mentioned stripping the

material after etching. Isn't dry film also used for "solder mask" ,

in which case it remains on the PCB?

> 

> I'd expect that the etching of copper is completed, rinsed, then

dry-film for solder mask is laminated on, then some type of light

(UV?) exposure is performed through artwork for the solder mask, then

the exposed portions of the mask are washed off. Perhaps this last

"wash off" is actually called stripping?

> 

> I'd like to learn how to do solder mask and silk screens via dry

film at home. Especially if it can be done little to no chemical solvents.

> 

> Paul

> 



Paul,



Soldermask material is screen printed on the board after all the

etching and drilling is done. Curing of the soldermask coating is by 

heat or UV light depending on what masking material is used. In my

shop we use UV soldermask and screen printing inks. 



Most boards made today use photo imaged soldermask. The board is

coated with solder masking liquid, cured, UV exposed and the final

image is developed out in a spray tank. It's similar to processing dry

film etch resist. Primary etching resist would not hold up as a

soldermask because it gets brittle with age (like all of us... lol ).

It can't take the soldering temperatures either and would begin to

melt or delaminate.



Tom





    
  

    
    




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