Using A PCB To Reflow PCBs

It's not too hard to make your electronics project get warm. Design your traces too small, accidentally short the battery inputs together, maybe reverse the voltage going to your MCU. We’ve all cooked a part or two over the years. But what about making a PCB that gets hot on purpose? That's exactly what [Carl Bugeja] did in his second revision of a PCB hot plate, designed to reflow other PCBs.

[Carl's] first attempt at making a hot plate yielded lukewarm results. The board, which was a single snaking trace on the top of an aluminum substrate, did heat up as it was supposed to. However, the thin substrate led to the hot plate massively warping as it heated up, reducing the contact against the boards being soldered. On top of that, the resistance was much greater than expected, resulting in much lower heat output.

The new revision of the board is on a thicker substrate with much thicker traces, reducing the resistance from 36 ohms on the previous design to just 1 ohm. The thicker substrate, paired with a newer design with fewer slots, made for a much sturdier surface that did not bend as it was heated.

We especially like the wiring solution [Paul] came up with for his new hot plate. Soldering to a resistive heater can be a massive annoyance since the board will act as a heatsink. While Alligator clips do work for testing, there is always the chance of them slipping and shorting against each other. [Paul] decided to make a custom flexible PCB that would connect with nylon screws to the hot plate, and fit directly onto the connection points of his power supply.

Unfortunately, this new revision of the board did have some issues as well. The biggest of these was that there was a miscommunication with the board manufacturer, and the solder mask used begins to degrade after a few hours at the operating temperature. But for light-duty work and intermittent use, it is the perfect tool.

You can read more about [Paul's] first PCB hot plate in our previous coverage of it here.