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I’ve got a large inductor that needs to be soldered to my board. The pads are hidden underneath the component so hand soldering is not an option. The data sheet says to reflow at 260c for 40 seconds max.

I did just that with a hot air gun and pre-heating underneath at 180c. I still couldn’t get any flow after a whole minute since the thermal mass is just so huge.

My super wide 2oz copper traces aren’t helping either. How do I solder this part?

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  • \$\begingroup\$ What sort of solder are you using? Have you applied flux? \$\endgroup\$ – JYelton Nov 6 '19 at 22:33
  • \$\begingroup\$ @JYelton I was using solder paste, which has flux in it. I think we use lead free at my work \$\endgroup\$ – Ryan Nov 6 '19 at 23:02
  • \$\begingroup\$ Just asking to clarify for any potential answers. \$\endgroup\$ – JYelton Nov 6 '19 at 23:04
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I've had this problem before, the only way I've solved it is to heat the whole underside of the board with an IR reflow station for BGA's or using a hot plate.

The underside of the board needs to be substantially warm because most of the heat is wicking out through the internal planes and to the air. 2oz copper doesn't help, it's 4x better at transferring heat than 0.5oz.

The PCB doesn't need to be very hot, maybe in the 100C to 150C range.

You can then use two soldering irons to heat the pads or a hot air gun to get the part on.

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  • \$\begingroup\$ If you're extremely desperate, you can also heat the board by putting it on an upside-down electric clothes iron. I've done it before. \$\endgroup\$ – Hearth Nov 7 '19 at 0:57
  • \$\begingroup\$ Or use a skillet, I've never done it but I've seen it done \$\endgroup\$ – Voltage Spike Nov 7 '19 at 2:26
  • \$\begingroup\$ @VoltageSpike Just make sure to never use the skillet for cooking again! \$\endgroup\$ – DoxyLover Nov 7 '19 at 7:57
  • \$\begingroup\$ I used an IR heat bed from my work. I might instead buy a solder paste that melts at a lower temperature or extend the pads out beyond the footprint so I can get to it with a soldering iron \$\endgroup\$ – Ryan Nov 7 '19 at 21:00

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