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Little Chippy Challenges

Wed, 11/10/2010 - 4:23am
Screaming Circuits

And in terms of "Chippy", in this context, I'm referring th chip-caps and any other tiny little two-connector components. When considering surface mount, most people think of the many-connector parts, like BGAs and QFNs as the challenging components. That's mostly true. However, the little passives can be big bears too if not treated properly.

Two part tombstone You can have tombstoning problems. This can be cause by unequal sized pads, unequal sized traces going to the pads or inequality in copper plane in a different layer. A big part on one side can cause tombstoning too - the big part's thermal mass may slow the solder paste melt on one side of the part, leading to  tombstoning.H Skewed passive via in pad

Via-in-pad is still a problem too. Open vias can lead to unreliable connections, tombstoning or crooked  parts.

Soldermask tombstoning for blog Solder mask can cause problems too. Too thick a solder mask can prevent the part from reaching the solder and can cause tombstoning. Too think a solder mask can also interfere with out-gassing in the reflow oven which can cause solder ball splatter. (A = okay, B = not okay).

Duane Benson

It just goes to show you...

It's always something.

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