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The (battery managing) IC I want to use has an exposed pad for thermal relief. I am designing the PCB and want to hand solder the chip on the board. I have read that you can drill VIAs to connect the exposed pad to a ground plane. I would solder the pins (easy enough) and then solder through the VIAs to the ground pad. Is this the best practice?
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    \$\begingroup\$ Been there, done that... and in retrospect, get yourself a hot air tool. They are so cheap now (paid $35 for my to-go version), and solve not only this problem, but many others as well, such as mistakenly soldering an SMT part down unaligned. \$\endgroup\$ – Chris Stratton Apr 2 '18 at 18:30
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For hand soldering chips like that with a metal pad I use a largish via. I solder the leads first after positioning the chip correctly, and then apply solder through the via with a large tip. The technique works very well.

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  • \$\begingroup\$ would you say 4D/w ratio for largish hole D to wire ,w diameter ? I think it also helps to spread the heat on a larger bottom side ground plane with 10cm^2/W with many heat pipe vias (+1) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 2 '18 at 18:34
  • \$\begingroup\$ @ Leon, that's exactly what I have done in the past for proto hand soldering operations only. If the default via array is 25/12 then I would use one of those thermal vias (of the via array) w/a ~25 mil drill to feed the solder thru. Don't forget to clear the soldermask on that opposite side via/pad to get good thermal contact w/the solder iron. \$\endgroup\$ – Steve Apr 2 '18 at 18:56
  • \$\begingroup\$ I haven't tried this (because I have a hot air rework station), but my instinct is saying to pre-tin the chip pad to aid in creating a good joint. Could also imagine that making it difficult to solder leads first. Any voice of experience have some input there? \$\endgroup\$ – Phil C Apr 3 '18 at 0:21
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In addition to what others said....

Do not overlook the area for dissipating 2.5W of heat during full charge current and expect worse than best case 20Vin efficiency.

This means you need heat pipes or vias under IC heat pad to all layers for at least 6.25 sq in according to eval. PCB design which is consistent with my design standards for open air use in thermal resistance using >2.5W/sq.in

Enclosed , needs much more thermal design effort.
MCPCB is better with Alum, and Cu MCPCB is best.

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Best practice would be a reflow process in a reflow oven. You could also achieve similar results with a electric iron or a hot air fan. I would not recommend soldering such a pad with a soldering Iron.

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    \$\begingroup\$ Or you could just put paste under the chip if there is no ground plane and let it reflow itself in operation.... ( just kidding) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 2 '18 at 19:04

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