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TMS320VC5416: Using SnPb Package with Pb-Free Paste and Reflow Profile

Darren (FAE)
Expert 5483 points
Part Number: TMS320VC5416

It looks like the MSL Peak Reflow Temp rating is different between SnPb packages, and NIPDAU/SNAGCU.
Is this difference only related to the melting temp of the ball finish?
Or is it related to the moisture vaporization and pressure increase of a different package/mold material?

According to J-STD-020E, Pb-Free MSL Peak Temp is 260℃, while SnPb MSL Peak Temp is 220℃ (small changes based on package size)
The 5416's DS also shows this in the MSL section for different package (lead finish) types.

Can the 5416's SnPb package be used with the same reflow settings used for the Pb-Free versions?
What are the key concerns when doing this?

  • 0
    TI__Intellectual 1380 points

    TMS320VC5416 comes in two package types - LQFP and NFBGA. 

    For the LQFP, the finish is NiPdAu and can be soldered to whatever finish is selected by the customer. Either SnPb or SAC (SnAgCu) solder paste are compatible with the NiPdAu leads. SnPb has Liquidous temperature of ~183C vs SAC of ~217C hence the two different peak reflow profiles.

    The NFBGA has solder balls attached by TI where it has two versions - SnPb solder ball or SAC solder ball. That solder ball type determines the industry standard reflow profile. If you were to attempt to reflow the SAC version to the lower SnPB profile, you may not be truely melt the solder ball. For the reverse situation of SnPB solder ball version to leadfree profile, you may not damage the TMS320VC5416 itself since it can support 260C but it may cause unexpected issues on the solder joint quality.

    Note that you don't have to reflow it at 260C where that is only the max rating. Often customers may run peak reflow at lower temperatures based on recommendations by solder paste supplier not IC ratings.

    You did not ask about it but you should note that mixing SnPb with Pb-free paste needs special consideration. We know that some customers have run this but there could be complications on this with the complex intermetallics that will be created in this mixed process. This article from Circuitnet (I am an e-subscriber and I recommend it for those interested in SMT manufacturing) has some SMT experts discussing the pros+cons of this. Soldering Lead-free Components with Tin-lead Solder (circuitnet.com)