I'm struggling with issues prototyping PCBs having ICs with a thermal pad. I assembled a new 100-volt buck converter powering a 12V fan, see schematic:
The circuit uses the elegant NSC LM5163, a 100V 0.5A 1MHz converter in an SO-8 PowerPad package. On the pcb layout, I had extended the thermal pad beyond the IC to allow access for a soldering-iron tip.
After soldering the chip's 8 pins, I used a large flat tip to wick solder under the IC onto its thermal pad. At test, the circuit malfunctioned. Did I damage the IC while soldering? Removal was a pain. Using a talon tip failed to heat the pad, ditto for my hot-air system, only a giant flat tip applied to an exposed ground plane above the chip (see image) got everything hot enough to release the IC. I think I'll forgo soldering the pad, as the converter only dissipates 70mW with a 300mA load.
But the experience makes me wonder, what's the best way to do prototype assembly of pcbs having thermal-pad ICs?