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#40980

| 14 April, 2006

Hi, I am in the process of developing a "hybrid" reflow profile to solder a board that has LF BGAs and leaded solder. Has anyone encountered a similar situation before? if so what was the "safe" top side temp for the leaded components that was set in your profile?. I am aiming for a joint temp of little over 220 deg C for about 45-60 sec.

any pointers?

Thanks in advance

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#40985

Hybrid [Leaded/ Leadfree] BGA Profile | 14 April, 2006

As from previous discussions on this topic here on SMTnet, we are perfectly comfotable using leadfree component solderability protection on components with leaded solder, except BGA. Consider balling your BGA to be leaded.

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#40990

Hybrid Profile | 15 April, 2006

Amol,

We pulled off this "hybrid profile" with a leaded solder paste. We recently got our tensile test report results, and our Pb-Free BGA / Pb Paste sample broke off during tensile tests at the pad/substrate interface, and not the joint. This indicates that our profile was kick ass!

The hybrid profile is simple. Ensure a TAL where liquidus is 217*C of at least 30 seconds and a peak around 230-235-ish. It helped that we used a "transitional" lead paste containing flux similar to their Lead-Free formula. Several paste manufacturers now offer this. Your time above 183*C will be a little on the high side. Be mindful of your low mass chip components. The one negative result we had on this hybrid profile was "charred looking" burned-off flux on the 0805 components.

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Slaine

#41017

Hybrid Profile | 18 April, 2006

Did you try tensile testing after thermal cycling? If there are any intermetalic problems between the two alloys this should show it.

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