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SMD hot plate reflow. With a PCB heated bed? (the ones used in 3D printers) — Parallax Forums

SMD hot plate reflow. With a PCB heated bed? (the ones used in 3D printers)

Alex.StanfieldAlex.Stanfield Posts: 198
edited 2014-06-05 02:38 in General Discussion
I'm dreaming about a DIY hot-plate based reflow soldering system (like these below) when a friend of mine suggested to use a PCB heated bed for doing the reflow.
http://reprap.org/wiki/HotplateReflowTechnique
https://www.sparkfun.com/tutorials/59#1Hot%20Plate%20Reflowing
http://www.instructables.com/id/Extreme-Surface-Mount-Soldering/?ALLSTEPS

I didn't search deep enough but didn't find success cases for this. (and did found one failure http://hannahnapier.co.uk/tag/mendel/ )

Has anyone done something like that? Similar DIY project?

Thanks for sharing.

Alex

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-04 11:19
    I am not sure why anyone would try to use a PCB Heatbed for SMD soldering.

    There are so many home appliances that can output the right temperature and it seems that the PCB Heatbed would struggle to reach the temperature required. Plus they don't seem as safe or stable for such use. It seems that they are intended for 50-60 degree C use (with an absolute max of 110 degrees C), while SMD soldering is much higher temperature ... at least 188 degrees C.

    There is also a big advantage with a skillet or hot plate having a big thermal mass to stabilize temperature control, whereas a thin copper layer on a PCB has very little thermal mass.

    http://reprap.org/wiki/PCB_Heatbed
  • Alex.StanfieldAlex.Stanfield Posts: 198
    edited 2014-06-04 11:32
    Loopy Byteloose wrote: »
    I am not sure why anyone would try to use a PCB Heatbed for SMD soldering.

    There are so many home appliances that can output the right temperature and it seems that the PCB Heatbed would struggle to reach the temperature required. Plus they don't seem as safe or stable for such use. It seems that they are intended for 110 degree C use, while SMD soldering is much higher temperature ... at least 188 degrees C.

    There is also a big advantage with a skillet or hot plate having a big thermal mass to stabilize temperature control, whereas a thin copper layer on a PCB has very little thermal mass.

    http://reprap.org/wiki/PCB_Heatbed

    Loopy, although I agree with you it was exactly the lack of thermal mass that I found interesting. The typical temperature envelope has a sharp decrease at the last leg. You are even required not to exceed around 10 secs above 200°C (depending on device to be soldered). Heating is relatively easy, cooling on the other hand depends only on how much energy you have (bigger mass->more energy) and the thermal conductivity to the medium where you dissipate that energy. That is assuming no forced cooling.
    I was wondering you well you can follow the thermal envelope with typical hot-plate.

    Alex
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-04 22:54
    Well, PCB was never designed to be a heating element. At some point the epoxy layer delaminates and it all falls apart.

    If you need rapid cooling, the toaster oven approach might be best.

    I simply feel that the appliance industry has heating elements pretty well-engineered. The use of a PCB is an oddity that Rep-rap came up with.
  • LeonLeon Posts: 7,620
    edited 2014-06-05 02:38
    The best place to find out about making and assembling PCBs is the Homebrew PCB Yahoo group:

    https://groups.yahoo.com/neo/groups/Homebrew_PCBs/info

    Some people there seem to be using hotplates successfully, although I don't think it is an ideal solution because of the thermal inertia.
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