Hi Inge,
I got your pictures, although I had to get them from my RD Circuits email
account while I was home. I'm off today because of the holiday here. I
figured that they would be there because you had posted referencing the
photos. Anyways, they are here:
http://stevezeva. homestead.com/Photo1.jpg
http://stevezeva.homestead.com/Photo2.jpg
http://stevezeva.homestead.com/Photo3.jpg
Steve
----- Original Message -----
From: "Hernefjord Ingemar" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, September 07, 2009 7:21 AM
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
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
