It is critical to use a high Temperature Lead Free Soldering profile so
both the leaded solder and the lead-free solders will melt completely
and mix evenly.  My company has done that when we have had no other
option, with great care to ensure the Lead free balls fully reached
liqudus.  This required cross sections of the balls to ensure this for
each product.
Mark Woolley

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Tuesday, September 25, 2012 7:10 PM
To: [log in to unmask]
Subject: Re: [TN] Leaded Paste and Lead Free BGAs - Do they mix?

Robert,

There are a number of papers on the subject I can share with you.
I'll send them to you directly. As Vladimir says, it's a really bad
idea.

Bob Landman
President
H&L Instruments, LLC
LDF Coatings, LLC
PO Box 580
34 Post Road
North Hampton, NH 03862
tel (603) 964-1818
fax (603) 964-8881
www.hlinstruments.com
www.ldfcoatings.com 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Tuesday, September 25, 2012 8:36 PM
To: [log in to unmask]
Subject: Re: [TN] Leaded Paste and Lead Free BGAs - Do they mix?

The balls HAVE TO have enough heat delivered to distribute Pb evenly
throughout the joints. As a results they will collapse.
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: Robert Kondner <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Tue, 25 Sep 2012 20:26:28
To: <[log in to unmask]>
Reply-To: <[log in to unmask]>
Subject: [TN] Leaded Paste and Lead Free BGAs - Do they mix?

Hi,

 

I have a customer using leaded paste with lead free BGAs. I think they
want to have the balls NOT collapse for better optical inspection.

 

Sounds like a really bad idea to me but I have no explanation where I
can say as why.

 

Can anyone make suggestions either way?

 

Thanks,

Bob K.



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