Hi Nancy -

I'm not sure I fully understand your application or your suppliers process
in this case, but let me give you a few thoughts.  I am not aware of any
U.S. or overseas specifications dealing with the properties of removable
masks.  I would expect this to be because these materials are not normally
end item identifiable or deliverable materials.  Here goes with the
thoughts:

If the circuit trace has even the slightest amount of a fusible alloy (such
as tin/lead plating or solder coating) in the area that the removable solder
mask is applied over, then that material will melt when you reach its reflow
temperature.  Melting will in turn cause it to lose its bond to the
removable solder mask, and allow seepage to occur;

If the removable solder mask is exposed to process temperatures higher, or
for a period longer than its formulator/manufacturer rates it for, then its
bond to the circuit trace may fail and allow seepage.  The answers for this
should be available in the formulator/manufacturers data sheet.  Improper
cure or processing of the mask duriing application could produce similar
faults;

If the board surface was not properly prepared/cleaned, or the surface was
not compatible with the removable mask, it could account for these
conditions.

Let me know if any of these items start to strike a familiar chord with this
problem, and we'll trry to take it a step further.

Regards - Kelly



-----Original Message-----
From: Nancy Trumbull <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Thursday, October 07, 1999 7:15 AM
Subject: [TN] Removeable Solder Mask


HI Technetters,

Every one did so good for me on the electrical migration
that I'm back.


Problem: Solder is seeping under the removable solder mask during wave
solder. Key word :REMOVABLE

Investigation: Indicates Poor process at the supplier
Supplier states "that this problem is typical of removable solder mask
made in the states".
Key words :made in the States.
  Because they can not use the same type of material
as over sea.

   I have IPC-SM-840C
Qualification and Performance of Permanent Solder Mask
This does me no good.


Our Supplier will remove some of the ID landing.  Which should stop the
seepage during wave solder.

But I would like more information on Removable Solder Mask
Standards in the States.

I have ask for information on removable solder mask before and
got no reply .  Could this be something fairly new for the states?
My pass experience has always been with over sea suppliers
for this type of product.

Thanks to all that reply in Advance
Nancy

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