Would like to propose a way of looking at this issue....

Insoluble/partially soluble salts form during fabrication, and assembly.
Some of these salts are "stand alone", for example Lead Chloride, others are
salts formed with the substrate/soldermask.  For example, a Copper salt with
an acid group on the laminate.

Key thing to remember, there is no such thing as a COMPLETELY insoluble salt,
and when compounds form with the substrate, the metals can be released slowly.
So, if you "cook", or boil, or otherwise wash a test board long enough, at a
high enough temperature with the right solvents you are ultimately going to
get "something" off.  Indeed, it is probable that if the test is severe
enough, you could be FORMING some of the "contaminants" during the test.  Key
things to ask are how relevant is what you are getting off the board and
measuring...

In other words, if a compound/contaminant is truly innocuous, and does
nothing to the performance of the board, does its presence matter?

Somebody before me brought out the fact that simply using conductivity to
measure cleanliness is pretty simplistic, and a thorough job would be to run
ion chromatography ....if you can afford it.

So, the perspective I am trying to show is that if you work at it hard enough
at it, you can almost always find SOMETHING wrong....a fact which is
currently being used by a VERY large PCB consumer to attempt to return many
millions of dollars of PCB which have become "surplus to their requirements"
as defective goods...

Rudy Sedlak
RD Chemical Company

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------