Hi Neil,
        I personally would not use a water soluble flux and not clean it
afterwards,
no matter where the boards end up (high humidity or not).
To leave this type of flux on the board especially in a high humidity
climate is asking for trouble. What you are probably seeing is tin/lead
corrosion?



Regards,
        Roger Deakin
         PEC Producibilty Engineer

Address abcd
         Newport Road
         Cowes
         Isle of Wight
         PO31 8PF
& Tel    +44 (0) 1983 202629
& G-Net 7 605 2629
% Fax    +44 (0) 1983 202106
)  EMAIL [log in to unmask]


> We are seeing PCBs returned from our customer which have a black substance
> around solder joints and within the solder resist window.
>
> It does not appear to be flux but our customer has suggested that it could
> be a fungus.  The boards are shipped to China so are seeing high humidity
> etc.
>
> Has anyone ever seen anything like this and what is the solution?
>
> We are using Multicore MF300 flux (water soluble) and are not cleaning the
> boards after assembly.
>
> Thanks,
>
> Neil
>
> Neil Atkinson - Quality Manager
> Stadium Electronic Controls Division
> Stephen House, Brenda Road, Hartlepool TS25 2BQ
>



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