Hi Denis,

I was rather hoping that the SAC balls might not reflow at all. Was considering putting the DDR2 devices on the bottom(light)
side of the board where they would be the highest heat capacity component. That way it might be possible to avoid melting the
SAC balls and just rely on a horrible joint comprising SAC-SnPB intermetallic on the DDR side and  SnPB-Cu intermetallic on the
board side.


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
______________________________

-----Original Message-----
From: Denis Ryskamp [mailto:[log in to unmask]]
Sent: 13 December 2005 14:47
To: '(Leadfree Electronics Assembly Forum)'; 'David Greig'
Subject: RE: [LF] Mixing SnPb and Pb free BGA's on an assembly

Good luck. We had much difficulty with reliability of the connections. The silver solder balls did not fully reflow using SnPb
process. Performed a manual operation to install the BGA after normal SnPB process.

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of David Greig
Sent: Tuesday, December 13, 2005 9:30 AM
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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