Thanks Mike, for your feedback. I look at the boards prior to mask apply and
I do see some delamination around the screw, so torque must be causing force
to separate the bond. I think if I use a washer under the screw head or not
even place the screw till after wave.
I tried some mask on a bare board and peeled it off with no delam evident.
Then I put another board with mask on in different locations and waved board
and peeled off with no problem.
Dave C.

-----Original Message-----
From: Barmuta, Mike [mailto:[log in to unmask]]
Sent: Friday, August 08, 2003 9:32 AM
To: [log in to unmask]
Subject: Re: [TN] The attack of the Peelable Mask


Dave: The obvious answer is that the soldermask is not properly bonded to
the board. The adhesive strength of the CM8 to the soldermask is nowhere
near the bond strength of the mask to board. My first guess would be there
is some type of surface contamination between to board and soldermask
causing this.

A couple of questions to better answer your question:
1. What type of soldermask is it?
2. Is it coming off the laminate, immersion silver or both?
3. If you apply the CM8, allow to cure and peel off without wavesolder does
the same thing happen?
4. Is it possible that screw/nut/heatsink are fracturing the mask in some
fashion causing it to lift?



Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett WA

425-446-6076





-----Original Message-----
From: Dave Chapman [mailto:[log in to unmask]]
Sent: Friday, August 08, 2003 6:59 AM
To: [log in to unmask]
Subject: Re: [TN] The attack of the Peelable Mask




-----Original Message-----
From:  Dave Chapman
To: [log in to unmask]
Subject: [TN]  Peelable Solder Mask


 I am putting Chemtronics Chemask CM8 on a screw and nut securing a heatsink
and when I peel it off after wave solder the board solder mask is coming off
as well. The boards are Immersion Silver Finished. We have used the Chemask
for hundreds of thousands of PCB's without this issue. What could be wrong?
Dave Chapman


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