I am sending this on behalf of a board manufacturer who has problems 
with a customer's strict cleanliness requirements. They manufacture 
double sided surface mount boards in a 12 up panel format.The solder 
used is SCM water soluble with 2% silver content. The boards 
are washed twice through a frequently drained autowash with DI water. 
The customer requires an ionic contamination of < 0.5ug/cm2. During
autowash, boards are measured in an ionagraph while 2/500 are also 
measured at final audit - any final audit fails requires the whole 
batch to be rewashed and retested. Typical ionagraph results vary 
between 0 and 0.5ug/cm2. The boards are then functionally tested, 
packed and shipped. The customer measures 5 boards at incoming 
inspection - if 1 fails the 0.5ug/cm2 spec, the entire batch is 
returned.
Does anyone have any experience of the amount of contamination that 
boards can pick up during shipping/packaging even with stringent 
handling measures?
Is it practical for the customer to insist on this limit particularly 
as the board is without any conformal coating?
One proposed solution has been the globtopping of the most critical 
area of the board though this involves extra time and capital cost. 
Has anyone any alternatives?
John Barton


_____________________________________________________________
John Barton AKA JohnnyB
NMRC, Lee Maltings,               Phone : +353-21-904082
Prospect Row,                     Fax   : +353-21-270271
Cork, Ireland.                    e-mail: [log in to unmask]
"Whenever I'm faced with a difficult problem, I always think to
myself 'How would MacGyver deal with this?'"
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