[tinwhiskers] Re: - RoHS & BGAs!!!

  • From: "AL-Yousef, Hani E" <Hani.AL-Yousef@xxxxxxxxxxxxxxxxxxxx>
  • To: <tinwhiskers@xxxxxxxxxxxxx>
  • Date: Mon, 23 Feb 2009 13:53:57 -0500

Ed,

I understand what you are trying to say. 
  
We have run into issues with board anchoring and SMT capacitors before,
where KEMET caps would break due to the moment arm created by the
distance away from the mounting screw. 

Thanks,
Hani

-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Parnagian, Edward
Sent: Monday, February 23, 2009 11:53 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: - RoHS & BGAs!!! 

Hani,

When Bob said "middle of the board is the worst" what he meant was that
midway between supports is worst.  If you're only anchoring at the
corners of the board, then the middle of the board is worst.  If you
have a support in the middle board, then half way between the middle
support and the surrounding supports is going to have the problems.

Best regards,
Ed

-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Landman
Sent: 2009 Feb 22 4:51 PM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: - RoHS & BGAs!!!

Hani,

Regarding underfill, if you do have to use SAC then underfill does seem
to help (depending on where on the board the BGA will be located (in the
middle of the board is the worst place - where mechanical stress is
greatest).  This article is a good one on the subject

http://ap.pennnet.com/Articles/Article_Display.cfm?Section=Articles&Subs
ection=Display&ARTICLE_ID=220942

Bob Landman
H&L Instruments, LLC




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