ImSn, the adds are not known.
Inge
----- Original Message -----
From: "Wenger, George M." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, September 07, 2009 6:09 PM
Subject: Re: [TN] Need clever comments
What is the PCB surface finish that shows a Tin whicker
Ingemar,
What is the PCB surface finish that shows a Tin whicker on inside of the
PRH barrel of the non soldered board in Photo #1 that Steve posted?
Regards,
George
George M. Wenger
Andrew Solutions
Senior Principal FMA / Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [Office] (732) 309-8964 [Cell]
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Monday, September 07, 2009 7:22 AM
To: [log in to unmask]
Subject: [TN] Need clever comments
Hi all, need some professional backup regarding MIL quality boards.
Objects: FR-4 Class III double-sided multi-layer boards, populated with
SOICS, BGAs,and a lot of passive components.
Observation 1 : the non soldered board have lots of Tin whiskers on
inside of the PTH barrel. My thought is this: if whiskers can grow long
before the board is assembled, then ain't it likely that even CAF can be
generated? See photo 1.
Observation 2: Copper has somehow penetrated the solder mask. This can
be found everywhere along the conductor traces. You need a very good
light microscope and a SEM to see it. See photo 2.
Board data: Copper with 0.8 micrometer Immersion Tin. No nickel barrier.
Solder mask thickness not specified.
Application: Typical MIL-883 environment
Q1: What is your opinion about that thin Tin directly on copper? I
dislike the concept. Copper is very mobile at high temperatures, and
combined with humidity, there can be leakage currents and corrosion
issues. Even if the boards are CCd, there is a risk with copper .
Q2: I gave the advice to introduce a nickel barrier, but our customer
claimed, that they can't because of pressfit connectors and pressfit
test pins on the board. Furthermore, they had heard that one cannot have
nickel platings when pressfitting, because the nickel will crack and
oxidize and cause electrical disfunction. Is this your opinion too? Are
there any relevant testing behind such statements?
Thanks in advance
Inge
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