Blow Holes voids in solder fillet on caps

blow holes and via holes are almost always caused by moisture and in PTH they could be moisture and improper drilled holes. If you are seeing solder balls next to the parts than I would say you have a reflow profile problem. Are you using any kind of thermal prifiling device to verify? like KIC or mole?

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Here’s what we seem to know: * There’s a problem with voiding in the solder connections of SMT capacitors * A void is an open area caused by air or process fluid that is trapped within a solder connection * Voids are an allowable condition as long as the solder connection meets all of the other dimensional requirements * Voids are process indicators * John expects to see solder balls here instead of voids. Solder balls are the first cousins of voids.

Here’s what we don’t understand: * What’s the source of the air or process fluid that’s trapped within the solder joint? * Howcum this is only happening with SMT capacitors?

Things that I’d like to understand better are: * Could the capacitors be outgassing something or other? Does component baking, better moisture sensitivity handling of the capacitors help? * Are there buried vias below the pads of the components that have entrapped stuff that is outgassing during solder processing? * Is the thermal recipe for reflow soldering causing the solder paste to skin-over and entrap flux? [If so, why is this only happening with capacitors?]

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