We have lots of experience with the peelable masks. They are pretty
inert and leave no detectable residue provided they peel off cleanly.
There are two significant problems:
1. In order to peel off cleanly, they need to be put on pretty
thick--like 0.5mm thick. At this thickness, your resolution is not so
good, and it interferes with the solder stencil, so you need a stencil
cutout over that area and need to work at it to get decent
printing--maybe even hand squeegee the paste in.
2. If you get them hot for too long, they embrittle. Then you are in
for some serious problems getting them off cleanly. The thinner you put
them on, the less temperature/time they need to get this way.
We've also used water soluble. These work pretty good unless you are
trying to protect gold wirebond pads: The flux chemistry goes through
them pretty easily, but the solder won't wet the area. I don't have
data for contamination levels after removal, but we didn't have a
problem during the time we used them. Of course, these won't survive a
cleaning process.
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Wednesday, January 09, 2008 5:41 PM
To: [log in to unmask]
Subject: Re: [TN] Coating
Yannick,
We don't do that here, but when I was at Nortel we did quite bit. You
need to make sure the temporary solder mask is not going to cause
corrosion, especially if it is hard to remove and will be leaving bits
and pieces on your boards!
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Yannick Brisson
Sent: Wednesday, January 09, 2008 4:57 PM
To: [log in to unmask]
Subject: [TN] Coating
Hi,
I'm wondering what you guys do for coating a PCB with area to mask?
do you use something special, Do you do your jigg yourself, or do you
send it to some other specialize in it?
Thank you
Yannick
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