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Hello fellow engineers

I have decided to solder busbars to a high current pcb , but i have 2 concerns :

  1. Does soldering a flat busbar (shown in left image) could cause thermal stress and deformation of the PCB , since i donot have the height to use busbar that work as pcb stiffeners also shown in second image.

busbars

  1. Can i use a high temperature (ex. 350 degree C) paste or solder for the busbars , since after finishing this step the boards have to be sent to a small assembly shop for soldering the rest of the "small" components using standard re-flow process and I don't want the busbars to "fall off".

Additional info : board size is 140 x 100 mm , busbars are 90 x 30 x 1 mm. The current rating of the trace is 100A DC at 12v-24v . Using saturn calculator for 100A outer trace at 4oz copper you need a 60mm wide trace at 20 degree temperature rise , which consumes too much of board space.

any additional advice or ideas are more than welcome :)

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  • \$\begingroup\$ The temperature depends on the PCB, most epoxys that hold on the copper I have seen don't like more than maybe 280-300C \$\endgroup\$ – PlasmaHH Aug 24 '18 at 14:06
  • \$\begingroup\$ So you mean the idea is correct but i have to choose a solder than melts at about 280 to 300 degree . will that be affected by the reflow process ? \$\endgroup\$ – ElectronS Aug 24 '18 at 14:10
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    \$\begingroup\$ you would have to contact your pcb manufacturer. You could also glue them down at certain points (like they do it for wave soldering smd parts). also note that this will most definetly change the necessary thermal profile for that board \$\endgroup\$ – PlasmaHH Aug 24 '18 at 14:15
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    \$\begingroup\$ A lot of these issues that you identified are why bus bars are bolted on instead of soldered. Thermal cycling will wreak havoc with this design, as the CTE of the FR4 and copper are so different and they are rigidly attached over a large area. \$\endgroup\$ – W5VO Aug 24 '18 at 14:19
  • \$\begingroup\$ why would it change the thermal profile of the board ? does the thermal mass change too much ?? sure this is pcb will be approximately like a 10oz pcb however it is still fr4 not IMS ( metal clad pcbs) \$\endgroup\$ – ElectronS Aug 24 '18 at 14:19

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