Peter,

The rules are still the same: Pb has to be evenly distributed throughout the balls.
Regards,

Vladimir

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

-----Original Message-----
From: Peter Barton <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Wed, 26 Sep 2012 15:45:00 
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
        Peter Barton
	<[log in to unmask]>
Subject: [TN] Using Tin/Lead balled BGA in a Lead-Free process

Hi Technetters,

Interesting that this question has arisen for me when there has been a question posed here on the reverse scenario in the last couple of days. Firstly, I agree with other posters that full reflow and alloy mixing must be achieved when using Lead free BGA's in a Tin Lead process. There is quite a lot of data out there supporting this.

My problem is finding research data on using a Tin/Lead BGA on an otherwise fully Lead free assembly. This appears to be much more limited. So far I have only found one paper that refers to this particular scenario and some of it's conclusions are carefully qualified. 

Assuming that all the other the packaging materials for the Tin/Lead BGA part in question are capable of surviving a suitable reflow process to successfully solder the lead free parts whilst minimising thermal input, can anyone out there comment on potential reliability issues. For information the BGA balls are 63/37 Sn/Pb and the solder paste alloy is SAC305.

Many thanks in advance,

Peter Barton






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