Hi Phil,
I am just wondering how today`s PCB can be processed with DFSM ( dry film
solder mask ) for several reasons:
- DFSM is at least 2 mill thick , it means you might expect SM to be much
more higher than the pads
- It seems to me that ENIG and Immersion Tin chemistry will attack the DFSM
and probably will contaminate quickly the chemistry.
- what about resolution of DFSM which is usually far below lines/spaces
present today ???
Best regards
Edward

Edward Szpruch
Eltek Ltd
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: DUTTON Phil [SMTP:[log in to unmask]]
> Sent: å éðåàø 23 2004 2:54
> To:   [log in to unmask]
> Subject:      Re: [TN] Why Dry film Solder Masks?
> 
> I've recently specified dry film solder mask on a production board.
> I normally ask for LPI.
> The only reason being that I couldn't rely on LPI to reliably tent every
> via.
> The badly tented vias could not pick up solder and fill adequately to
> comform to the Class 2 requirements, creating reliability concerns.
> Ideally, I would like the vias filled and then tented with LPI, but our
> fab shops here in Australia don't do the via filling.
> 
> regards,
> 
> Phil Dutton.
> 
> -----Original Message-----
> From: Steve Gregory [mailto:[log in to unmask]]
> Sent: Thursday, 22 January 2004 11:47 AM
> To: [log in to unmask]
> Subject: [TN] Why Dry film Solder Masks?
> 
> 
> Can anybody tell me why dry film solder masks are still specified?
> 
> I don't want to hear; "Because they've always worked good..."
> 
> But some clear, concise, reasons for specifying them...
> 
> Vacuum at ICT is a dead deal, there are ways to deal with open via's
> with
> LPI's...Solder fill for via's is a dead deal...either you fill them, or
> you don't.
> 
> So why dry-films?
> 
> So many complications come up with dry film solder masks...
> 
> Not only for the bare board manufacturer...but also for the assembler.
> 
> Just a question...(for the DoD guys, especially)
> 
> -Steve Gregory-
> 
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