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December 2005

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Subject:
From:
Gerhard Haubner <[log in to unmask]>
Reply To:
(Leadfree Electronics Assembly Forum)
Date:
Wed, 14 Dec 2005 16:41:55 +0100
Content-Type:
text/plain
Parts/Attachments:
text/plain (78 lines)
Hello,

Except from questions about reliability you should also think about
other problems you get without melting of the solder spheres.

Two effects are used during reflow of BGA type packages: self-centering
and collapsing of the balls

With the self-centering effect, you can place the BGA with sligth
deviations on the solder paste and although it will pulled right above
the solder pads of the board

With the collapsing of the balls, you can balance height differences
between board and BGA

Think also what happens, if there is a warpage during reflow and the
balls are not melting.

Best Regards
Gerhard Haubner 

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of David Greig
Sent: Tuesday, December 13, 2005 3:30 PM
To: [log in to unmask]
Subject: [LF] Mixing SnPb and Pb free BGA's on an assembly

Is it possible to get an acceptable solder joint if a Pb free BGA is put
onto a board using SnPb solder paste and normal SnPb profiles?
The lead free solder balls are SnAgCu 96.5/3/0.5.

Seems nigh impossible to get DDR2 packages with SnPb balls.

I'm designing a high end DSP into an industrial instrument. The DSP is
not available lead free, nor does the application call for lead free
(thankfully).
There is no option to use a different memory type with the DSP. Nor is
there any possibility of using a different DSP or FPGA due to
time/cost/sanity.
Don't want to explore going lead free on this one (for obvious reasons),
and certainly do not welcome the expense of reballing 0.8mm DDR2 chips.


Best Regards

David Greig
______________________________
GigaDyne Ltd
Buchan House
Carnegie Campus
Dunfermline KY11 8PL
United Kingdom
t: +44 (0)1383 624 975
www.gigadyne.co.uk <http://www.gigadyne.co.uk/>
______________________________


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