Nancy: Removable or temporary soldermask is nothing new to the U.S. Some of
the liquid style has been around since at least the late 1970's, the tapes
longer than that.
I will try and give you a brief outline of the various styles and families.

Their are two primary groups, soluble and non-soluble or peelable.

SOLUBLE: This family is made up of materials that are either water soluble
or solvent soluble.
They are designed to withstand the flow soldering process but come off in
the subsequent wash/clean operation.
There are two groups within each of these soluble families. Liquids which
can be dispensed or printed on the board then dried or cured. The other is
tapes/films which are applied directly to the board in strips or die cut.

The advantage of the soluble materials is that they do not require laborious
hand removal after soldering, they come off in the wash. Some disadvantages
are that you have to have a wash process after solder, also there must be
chemical compatibility between the board/flux/solder/wash and equipment. The
goal being to survive the flux/solder operation but come off early in the
cleaning process.

NON-SOLUBLE: This family is made up of materials that require physical
removal after soldering. This family also has two major groups. Liquids that
are based on latex, vinyl, silicone and urethane materials. These can be
dispensed or printed on the board and dried. The other is tapes/films which
are also applied in the same manner are the soluble ones. The tapes are
typically kapton and high temp acrylics or silicones.

The advantage of the non-soluble resists is that they are not as susceptible
to chemistry compatibility problems as the soluble resists during
flux/solder/wash. Because of this in some cases they will standup better to
your flux/solder operation. The disadvantage is that they must be removed by
hand after soldering. These materials especially the liquids can be
difficult to remove and  become very time consuming and labor intensive.



The trick is to match the temporary sodermask to a particular style of
assembly processes and the masking requirements of the board. You may even
end up with more than one type of masking technique on the same board. The
objective is to prevent solder from desired areas but not leave behind any
deleterious material to effect board performance. We have used a variety of
these products from the U.S.,Asia and Europe. Some work, some aren't worth a
damn but it's usually because they are not being used for the proper
application they were designed for. You have to do the testing to qualify
the correct product.



Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett Wa.

425-356-6076
-----Original Message-----
From: Nancy Trumbull [mailto:[log in to unmask]]
Sent: Thursday, October 07, 1999 5:12 AM
To: [log in to unmask]
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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