We have been seeing the same thing since we switched to Metallic Resources WS-700 water soluble. We use a lot off commercial hardware and have always masked it. But since the switch we have also been masking S.S. I use a water soluble masking and have found the easiest way to mask H.W. and large areas on boards is to put some masking in a pan, thin very slightly with alcohol and use a paint brush. 

-----Original Message-----
From: Kane, Joseph E [mailto:[log in to unmask]]
Sent: Thursday, January 15, 2004 9:20 AM
To: [log in to unmask]
Subject: [TN] Solder Sticking To SS Screws


Because connector screws get Loctite, we use stainless steel temporary
hardware on bottom sides of some of our motherboards, and screw heads and
washers travel through the solder wave.  With the switch from RMA to OA
flux (Alpha 3355-HB), we find that solder now adheres to the hardware.
Here are some of our options:

1. Use latex temporary solder mask on hardware.  Of course, this will be
messy and labor-intensive.

2. Find some 2-56 x 1/2" screws in a material that Sn63 won't stick to.
Could they make a screw this small in nylon or diallyl pthalate?

3. Apply some kind of plating or Teflon coat.  Of coarse, with buildup on
the thread, they may not mate anymore.

4. What about a spray-on coating?  Would it be worth trying an anti-seize
like  molybdenum disulfide?

Joe Kane
BAE SYSTEMS Controls
Johnson City, NY


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