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I have design a PCB size about 100x60mm it reflow very nice on the hot plate but If I convert my PCB to a panelization 2x3 quantities size became 200x180, the edges began to lift up due to expansion during soldering. I think it is called as "PCB warping" maybe this expansion was happening when the PCB was in single form, but it was not noticed because it was not that much. But now it's starting to cause problems. How can I solve this problem?

At the moment, after I put the PCB on the hot plate, I press both sides with the help of pliers. I'm waiting for 10 seconds, when the expansion is corrected, I leave it with normal solder. But I think I can solve this problem by adding miling in some places on PCB design and adding features like V-cut to the panel.

Result is:

enter image description here

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My hot plate is this: enter image description here

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2 Answers 2

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Most of the time PCB warping is due to unbalanced copper placement in the design of the board.

Maybe you can mitigate the issue with some milling here and there. But the root of the problem is likely your board design.

If the board initially warps, then starts to flatten out while still heating (like in a "soak" reflow stage), then uneven heating may be the main issue. I'd be especially concerned when the PCB is approaching the size of the hot plate (like maybe it is...).

However, I'd suggest that you take a critical look at the overall copper placement, and amount, on each layer. Try to balance the amount of copper on each layer, mirror large copper pours on adjacent layers, and the like, so the board expands evenly when heated.

Buy a used benchtop reflow convection oven. You will get better results.

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  • \$\begingroup\$ Well thanks for your answer. But if the problem is about copper balance issue, the warpage could be seen while one pcb. The problem became bigger after i make panelization. 6 pcb together. Maybe i should add v cut \$\endgroup\$
    – mehmet
    Commented Jul 19, 2023 at 15:53
  • \$\begingroup\$ "The problem became bigger after i make panelization." That's to be expected with unbalanced copper layers. It's likely that it's not the fiberglass that's warping, its expansion miss-match between copper and fiberglass. \$\endgroup\$
    – Chris Knudsen
    Commented Jul 19, 2023 at 17:19
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The main reason for board warping is asymmetric distribution of the circuit patterns on both sides. The best way is to place relatively balanced with copper at two sides when you design. Don't place copper on one side but base materialon the other side.

Linda

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