Hi Michael,
My "wild" guess would be that the testing company used EDS for the elemental analysis. If I'm righht, then the technique DOES NOT allow one to get the quantative data. When I see the results similar to what you got (particularly including C), I become VERY suspicious.
You can contact me off line, if you want to.
Regards,
Vladimir
RIM
Sent from my Blackberry Wireless
Vladimir Igoshev, 519-888-7465 ext.5283
-----Original Message-----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Wed Jun 08 09:47:33 2005
Subject: [TN] Solderability issues with ENIG finish
> Hi ,
> We've been having some solderability problems with one of our supplier. A
> populated PCB was sent for elementary analysis and we got the results back
> from the lab.
> Before going further in the corrective action process i would like to know
> if some of you agree and support the conclusions of the report based on
> the following data.
>
> - The board sent to analysis was populated , one half of a smt pad did
> not wet with solder the other half wetted properly
> - The problem was noticeable on approx. 2% of the lot of PCB. 2-3 pads per
> board
> - The pad could not be soldered using an iron pen
> - Solder paste is standard Sn63, Pb37
>
> Two area on the pad were analyzed, one that was wetted , the other was
> not.
> Concentrations of element found were the following
> - On the wetted area of the pad ALIAS : "AREA B"
> 5.40% C
> 2.04% N
> 0.81% O
> 45.32% Sn
> 2.45% Ni
> 3.67% Cu
> 40.31% Pb
>
> On the unsolderable area of the pad ALIAS "AREA A"
> 6.08% C
> 9.08% P
> 9.55% Sn
> 66.62% Ni
> 3.47% Cu
> 5.20% Au
>
> The conclusion of the report states :
> Area A is a fracture surface at the intermetallic boundary while Area B is
> a fracture surface at or near the bulk solder. No mud cracking is seen at
> Area A which indicates that black nickel was most likely not present. The
> fact that there is a fairly large gold peak at area A indicates that there
> may not have been sufficient time to adequately form the solder joint as
> the gold may not have had time to diffuse into the bulk solder.
>
> I can post a picture of the pad if you can point me to a location
>
>
> Michel Arbour
> Kontron Canada Inc.
>
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