THIS MONTH WE show soldering of 01005 chip resistors from an early project with lead-free assembly. The microsection image in FIGURE 1 shows a few issues, but it's the circles in both joints that caught my eye. Yes, they are voids before they are unmasked. During sectioning we stopped just before entering the void. Most would have continued a few more micros to remove the thin sliver of solder, which was the wall of the void, to show the void. But everyone has seen voids before! Now to the important part. The pad size is too large for this small passive device and contributed to the addition of too much paste during printing. The length of the pad was reduced in further trials. During soldering, solder reflowed and wet over the top of the resistor termination. This resulted in lifting of the wraparound termination on both sides.
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