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Lead-free BGA in Tin/Lead Process

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#62841

Lead-free BGA in Tin/Lead Process | 4 October, 2010

I am trying to assess current industry thinking on the question of whether or not lead-free BGAs (SAC or other) can or should be soldered in a tin/lead process. It seems there are differing opinions on this and I'm wondering what some of you are doing or your thoughts on the subject.

Rick Thompson

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#62848

Lead-free BGA in Tin/Lead Process | 5 October, 2010

> I am trying to assess current industry thinking > on the question of whether or not lead-free BGAs > (SAC or other) can or should be soldered in a > tin/lead process. It seems there are differing > opinions on this and I'm wondering what some of > you are doing or your thoughts on the > subject. > > Rick Thompson

Most components purchased today are ROHS compliant, or lead free to some people. There is nothing wrong with using ROHS components in a leaded process.

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#62849

Lead-free BGA in Tin/Lead Process | 5 October, 2010

I agree that in consumer electronics there may be nothing wrong with using a lead free BGA in a SnPb process, but that blanket statement can't be made for the high reliability market.

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#62850

Lead-free BGA in Tin/Lead Process | 5 October, 2010

Nothing wrong with using RoHS BGAs except that the spheres won't melt/collapse at normal leaded reflow temps. Reliability will questionable. Some people use a hybrid profile with a slightly higher temp (~230C)and a slightly longer TAL (60 -90 sec). Depends on the application. YMMV.

Regards, Mike

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#62861

Lead-free BGA in Tin/Lead Process | 6 October, 2010

I've seen studies were Pb-free BGAs in a leaded process have no reliability issues when a lead free profile is used. Pb-free profile ensure proper ball collapse and solder joint formation.

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#62864

Lead-free BGA in Tin/Lead Process | 6 October, 2010

IBM Intel motorola did exhaustive studies on this and found that the best thing to do is (as others pointed out) the PBfree BGA reaches 217 minimum and the time above 217 must be extended to allow mixing of the 2 alloys. See attached a little diddy by Intel on this subject.

Good luck and Regards,

Attachments:

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#62870

Lead-free BGA in Tin/Lead Process | 7 October, 2010

The problem is there are also studies showing reduced reliability. Early thoughts were that if you got complete reflow of both solder materials then you'd be fine, but several studies have shown that there's something going on that's not well understood and just getting good mixing isn't sufficient. I've thermal cycled Pb free BGAs in SnPb paste and sometimes the reliability actually improved slightly over SnPb/SnPb or SAC/SAC, but with other BGAs the reliability was significantly reduced. The bottom line is that it's not well enough understood to take the risk for high reliability products (automotive, aerospace, etc).

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