Nichrome wire as the heating element

[skotekar]

Hi, I was wondering if the same control circuitry can be used with a nichrome wire as the heating element. With a good power supply I have seen that nichrome wire can be heat up even @ 5v. Any thoughts?

Nichrome is supposed to have better heat resistance and corrosion resistance.

[brettski74]

That depends. This particular design doesn't really do much in the way of control, so it doesn't really care what the heating element is made of. There are other designs that people - myself included - are playing with that do care what the heating element is made of, since we determine the temperature of the hotplate by measuring the resistance of the heating element, so those kinds of designs would need to know the correct thermal coefficient of resistance to correctly determine temperature. That said, I think the much bigger issue here is that you don't just need some wire to get hot. You need a complete assembly that contains the heating element, ensures that it is flat and will stay flat across multiple heat/cool cycles, that ensures that heat is spread over the entire board being reflowed, provides some protection from mechanical damage and corrosion and provides reliable means of electrical connection. While there's no reason you couldn't build such an assembly using Nichrome or Kanthal or any other appropriate material, I think that for the vast majority of home hobbyists doing this well is probably beyond most people's capabilities. An FR4 board may not be the absolute best performing solution, but it works pretty well and is relatively for anyone to design and have manufactured for very low cost.

Corrosion isn't really an issue for PCB hotplates. The copper is entirely encased within solder mask and/or your surface finish (eg. HASL, ENIG, etc) So while it is true that copper can corrode in air and this process is accelerated at elevated temperatures, the copper traces aren't exposed to the air. If you've abused the hotplate to the extent that the solder mask has broken down or delaminated, it's probably time to replace that board. If you don't abuse them, they last surprisingly well.