Recently I have sent out number of no-clean assemblies at different stages to an outside lab for a contamination evaluation. ( not analysis)  The numbers came back, and I was surprise to see how much more bromide and chloride had been collected during the assembly process.  The result is shown below:

At the bare PCB level, bromide level is 6.2 , while chloride is 1.2    ( all units are in ug/in sq.)
At the post reflow stage, bromide drops to 3.0, and the chloride goes up to  16.8
After wave soldering, bromide stays at 3.5, and the chloride drops to 8.1
At the final assembly level( no manual rework), bromide level soars to 30.8, and chloride is 9.6

I have called my paste, flux and alloy bar suppliers and confirmed that non of these material contain any bromide and chloride in them.

The original 6.2 ug/in sq bromide at the PCB level is most likely from the fire retardant material used on the FR-4.  But can someone help me to explain where did the additional 25 ug/in sq of bromide come from after the wave soldering process? what about the chloride level? Do these numbers look normal to you?

One of my customers has a cleanliness spec' calls for an assembled board with no more than 7.0 ug/sq in of bromide and 2.5 ug/sq in of chloride when they receive the board.

Do you think this requirement is reasonable for an assembled board built with a no-clean process?

Any kind of inputs and comments are greatly appreciated. Thank You.

Rudolph Yu