Steve:

        Good guess that moisture , or a process  chemistry was left along
the edges of the circuits. Some other possible causes are:
        Excessive undercut causing entrained air along circuits.
        Improper mixing of mask components ( entraining air)
        Excessive squeegee speed
        Improper drying ( heating to fast causing solvent to Boil)

        Coating technique would have a major impact in the root cause.
         NO matter what the cause , there can't be much in the way of
inspection and process controls at the supplier.

Russ Smith

Bicycle Mechanic  :)
 ----------
From: Stephen R. Gregory
To: [log in to unmask]
Subject: [TN] "Bubbly Soldermask..."
Date: Wednesday, July 26, 2000 3:11PM

Hi all!

We just got some boards in at receiving inspection that have thousands of
little "bubbles" in the soldermask all over the boards...they seem to
concentrate all along the edges of the features of the board. You can see
pictures of it at:

http://www.driveway.com/share?sid=e25a88c4.8e904&name=Pictures

One picture is bubblemask.jpg, the other is bubblemask2.jpg...what would
cause that? It's a LPI...don't know the brand name. I'm thinking that either
the boards weren't dry or cleaned well prior to soldermasking them. I'm
rejecting the boards of course...

My freedrive is filling up fast with all the pictures of the "pretty boards"
that we get from our vendors!!!

 -Steve Gregory-

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