Backward compatibility in LF solder pot

Dear all,

As we know there is a high risk of reliability issue due to lead contamination during mixture of NLF component at LF wave soldering process.

But we have the following feed back from one of our customer as follow:

Concerning the risk of mixing LF solder process with NLF components, it has to emphasized that the volume of lead on the terminals of NLF components is very small compared to the volume of LF alloy in the solder joint.

Yes, it is true that the durability is reduced by mixing LF process with NLF components, but tests conducted by us show that the reduction of durability does not in any way reach a critical level.

During 3 weeks of test production 1000 PCBS�s were wave soldered. All PCB was NLF HAL, and 75% of the components were NLF. The lead contamination was measured to be 0.04%. Our limit of contamination is 0.20%

The problem with lead contamination in LF process is some what exaggerated. If you are close to the contamination level, the solder pot can be "thinned" by adding a few kg�s new LF solder.

Based on the above finding from our customer, is it true that small amount (e.g. few NLF components)of NLF components have no significant impact to the lead contamination at LF wave solder pot ?

Thanks for you time and your valuable input is much appreciated.

Best regards,

Joseph

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