Peter,
I am not an expert on solder mask, but I will tell you what I do
know. If this is for a high frequency application solder mask thickness
effects the dielectric of the board. If one was to use a liquid, you run the
risk of having uneven coverage of the board. I personal prefer the
photo-imageable dry thin film, you get even coverage and I believe it
adheres to the boards surface better then the spray on applications.
Class 1 consumer noncritical industrial and consumer control devices
and entertainment electronics
Class 2 general industrial computers telecommunications equipment
business machines instruments and cretin noncritical
military applications.
Class 3 high reliability equipment where continued performance is
critical military electronics equipment.
According to Clyde Coombs Jr. Printed Circuit Handbook fourth edition p24.5
Screen Print Dry Film
thermal UV Aqueous
solvent liquid photoresist
soldering performance 1 1 1
1 1
ease of application 1 1 2
2 2
operator skill level 2 2 2
2 2
turnaround time 2-3 2-3 2
2 2
feature resolution 3 3 3
3 3
adhesion to SnPb 1 3 1-2
1-2 1
adhesion to laminate 1 1-2 1 1
1
thickness over conductor 3-4 3-4 1-2
1-2 2
bleed or residues on pads 3-4 3 1
1 1
tenting or plugging of holes 4 4 1
1 4
handling of large panels 3 3 1
1 1
meeting of IPC
SM-840 class 3 3-4 3-4 1-2
1 1
two sided application 4 4 1
1 3-4
capital coast equipment 4 4 1-2
1-2 1
1=good or high;2=moderate;3=fair;4=poor
If I am wrong and there is a better application out there I hope
someone will correct me. I hope this helps you out.
Ted Tontis
-----Original Message-----
From: <Peter George Duncan> [mailto:[log in to unmask]]
Sent: Tuesday, May 29, 2001 3:49 AM
To: [log in to unmask]
Subject: Re: [TN] Which Solder Mask
Photo-imageable seems to be the most common, but there are the other types
around as well, and what I'm trying to find out is why would a designer
choose one type over another - are there any guidelines on which type to
select for particular sorts of applications or particular sorts of
substrate materials, and having chosen one, how does said designer
determine how thick it should be?
It's not left to the PCB fabricator, is it? I've heard enough to know that
too thick a resist layer can affect solderability among other things, while
too thin a layer reduces its effectiveness.
Put it another way - if I don't specify a resist and resist thickness, how
do I gain confidence that my PCB fabricator has chosen to put the right
thickness of the right resist on my boards? Any ideas?
Best regards
Pete
Paul Klasek
<PaulK@ResMed To: "[log in to unmask]"
<[log in to unmask]>
.com.au> cc:
Subject: RE: [TN] Which Solder
Mask
05/29/01
01:33 PM
Thought it was bit fuzzy .
Photo-I is the way, watch for undercure (too fast process) on UV,
BLISTERS THAN . Common enough when fab's are stressed .
paul
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, May 29, 2001 3:05 PM
To: Paul Klasek
Subject: RE: [TN] Which Solder Mask
Thanks, Paul, but maybe I need to clarify what I'm after a bit - I'm
talking about the actual caoting that PCB fabricators put on boards to
cover external tracking, etc., the photo-imageable, dry film, UV cureable
type resist layer.
Pete Duncan
Paul Klasek
<PaulK@ResMed To: "'TechNet E-Mail Forum.'"
<[log in to unmask]>,
.com.au> "[log in to unmask]"
<[log in to unmask]>
cc:
05/29/01 Subject: RE: [TN] Which Solder
Mask
06:17 AM
Multicore's "Spot Stik" latex used to behave well, easy peel afterwards,
not the usual dentistry . That is, for the resist. paul
-----Original Message-----
From: <Peter George Duncan> [mailto:[log in to unmask]]
Sent: Monday, May 28, 2001 3:39 PM
To: [log in to unmask]
Subject: [TN] Which Solder Mask
'Afternoon, All,
Today I need your help to find a good guide on how to select solder
mask/resist materials and how to determine what thickness should be
specified for particular applications. Immediately I need to know
recommendations for 0.063" thick, 10 layer FR4 HASL finished VME
conduction-cooled boards of 15 mil track spacing for military application.
Boards will be Convection Reflow Soldered with Kester 63/37 solder and 331
flux. Anything else you need to know?
I'm from a manufacturing background and have never needed to know this
level of detail before. However, I am now involved with helping a bunch of
design engineers who have even less idea than I do about this sort of thing
than I have. I have had a go at the Web trying various terms and key words,
but get absolutely nothing useful back at all, so I'm hoping our TechNet
Goldmine/Delphi Oracle can succeed where the WWW has failed me.
TIA,
Pete Duncan
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