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Ag/Pd termination, reflow soldering issues

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Ag/Pd termination, reflow soldering issues | 4 April, 2007

Good morning,

Problem definition Poor soldering of thermistors with Ag/Pd termination

Background Process: lead free reflow soldering Paste type: Multicore LF300, SAC305 Component type: 0805 chip thermistor, Ag/Pd termination PWB finish: immersion Ag Reflow profile: fits LF300 process window

Defect photo

This problem has appeared at PWB populated mostly with simple chips and a few IC�s. PWB is thin (0.8mm) and evenly populated so there are no any temperature gradients across the PWB during heating. During soldering stage all solder flows to component�s lead leaving soldering evidence on PWB�s pad (please refer to the picture). Solder melts and flows. But flows mainly to component�s lead. Resulting joint appearance is cold one. The rest of PWB is absolutely fine. No any soldering anomalies.

According to component manufacturer requirements components have to be soldered within one year after shipment. Reels I checked were out of date. Could it cause such soldering anomalies? Is it possible to sort this issue out with process adjustment (profile tweaking etc.)?

By the way, manual rework of this defect after reflow is extremely hard. What could it be?

BR, Pavel

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Ag/Pd termination, reflow soldering issues | 4 April, 2007


We had exactly the same kind of problem with exactly the same type of component. Our components were well within their best before -date so it is not question of that. As we could not get it to work we changed to nickel barrier finish on the components and the problem went away. Heard though that component manufacturers have great difficulty in supplying components with nickel barrier finish.

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Ag/Pd termination, reflow soldering issues | 5 April, 2007

Good afternoon,

Thanks for input AR. Fortunately, supplier can offer us nickel barrier alternative. I will do exactly as you did.

BR, Pavel

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