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June 2005

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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Vladimir Igoshev <[log in to unmask]>
Date:
Thu, 9 Jun 2005 15:04:14 -0400
Content-Type:
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text/plain (167 lines)
That is what I thought. SO, you can not rely on the numbers, consequently, I wouldn't blame "Black Pad" right away. You'd need more detailed analysis to figure out what went wrong, at least that is what I'd do.

Vladimir



Vladimir Igoshev, Ph. D.
Senior Materials Researcher
Research in Motion
451 Phillip St.
Waterloo, ON, N2L 3X2

Voice: (+1) 519-888-7465, ext. 5283
Fax: (+1) 519-886-0863
E-mail: [log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Arbour, Michel
Sent: Thursday, June 09, 2005 2:52 PM
To: [log in to unmask]
Subject: Re: [TN] Solderability issues with ENIG finish


The equipment used to perform the analysys is an EDS type. EDAX DX Prime EDS
instrumentation with JEOL 5600 SEM.



-----Original Message-----
From: Ingemar Hernefjord (KC/EMW)
[mailto:[log in to unmask]]
Sent: Thursday, June 09, 2005 2:59 AM
To: TechNet E-Mail Forum; Arbour, Michel
Subject: RE: [TN] Solderability issues with ENIG finish


I recognise that too well, Arbour.

We passed  that scenery years ago. Not a fun situation, very frustrating for
the
operators.
Best tool for analysis was TOFSIMS. Gives you the whole story from surface
to deep into the pad. Layer by layer. Not like EDS, which gives you just a
bulk information. But, you need a very skilled person for interpretation of
the TOFSIMS results, and a even more skilled person who can tell you what to
do now.
Whole stacks of spectras and diagrams are useless if you can't give advice.

As you seem to need rapid advice, I'll skip the discussion about pad
metallurgy
and tell you what you can try. If you are desperate.
Use high speed rotating diamond tip, carefully remove the intermetallic
layer
that is 100% dewetting. Try not to remove all nickel. Use a drop of
Multicore
Hydrox 20 on the pad, solder the pad with a fine tip iron, and use a copper
braid
to remove excessive solder, and clean with acetone cotton tip. Now ready for

BGA repair. Could work, depending on the condition of your pads, which we
don't
know much about.

Finally, don't tell anyone that you used Hydrox...he-he, hope the IPC
inquisition
got no representative around here.

Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Arbour, Michel
Sent: den 8 juni 2005 15:48
To: [log in to unmask]
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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