Hi Carol! Just adding my vote to the other good LeadNet responses - I would
concentrate your investigative efforts on the analysis methodology. If
would be unusual for a  SAC solder pot contaminated with Pb or SAC
solderpaste contaminated with Pb to create a uniform contamination of Pb
segregated in a the top layer of the completed solder joints. There is a
fair amount of data which shows that the Pb would be distributed, somewhat
haphazardly, throughout the solder joint microstructure. I recommend you
conduct an AA or ICP chemical analysis of several solder joints - as long
as you extract your solder material carefully you will get a better
elemental fingerprint of the solder joint composition (AA and ICP are more
accurate methodologies but are also more costly and slower). Do you have
traceable XRF standards for your equipment? Have you characterized the XRF
active sample region footprint  (both depth and surface area)? And yes,
characterizing your solder pot composition at an increased sample frequency
(in comparison to what you do for a SnPb wave solder pot) is an excellent
idea. Good luck on your investigation.

Dave Hillman
Rockwell Collins
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             Carol Spiers
             <cspiers@INTERALI
             A.CA>                                                      To
             Sent by: Leadfree         [log in to unmask]
             <[log in to unmask]                                          cc
             >
                                                                   Subject
                                       [LF]
             01/27/2006 12:19
             PM


             Please respond to
                "(Leadfree
                Electronics
             Assembly Forum)"
             <[log in to unmask]
             >; Please respond
                    to
               Carol Spiers
             <cspiers@INTERALI
                   A.CA>






I have just had an analysis completed on a first batch run of leadfree
boards.  Results indicate we have  uniform contamination of 0.14-0.19
layer of lead across the board.  The testing and measurements were obtained
using  xray flouresence and indicate the lead is on the top layer of the
melded solder.  We confirmed that all parts were documented as being Lead
Free (but not tested by us for compliance).  Boards were double sided
silver immersion smt and thru hole combinations.  Solder paste used was
SAC, wave solder bar used was SAC.  The wave solder machine is brand new
(never used in a leaded process).  SMT oven is used for both leaded and
unleaded processes.
Because the contamination appears to be uniformly spread across the board I
tend to think this isn't a problem related to a couple of components not
actually being lead free and contiminating the huge pot of solder in the
wave.  One suggestion was that there might have been a thin layer of lead
over top of the silver immersion on the bare boards.

Is there anyone out there that would care to offer some suggestions as to
where we should focus our investigation or if any alternative testing
should be used.
So far we are going to:
1) do comparison testing of two batches of bare boards of the same product
coming from different suppliers and undergoing identical processing.
2) have a sample of the wave solder evaluated for contaminates and to
establish the bench for future sample evaluations.

Once again, your input and help will be much appreciated.

Carol
C. M. Spiers
Director of Operations
Interalia Inc.


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