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Hotbar Soldering Troubleshooting

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#87948

Hotbar Soldering Troubleshooting | 11 May, 2022

I have a few questions about hotbar soldering. What factors in hotbar soldering would lead to increased solder balls in an application where an FPC is soldered to a rigid PCBA? The FPC is an open window type, with unsupported leads. We have the same P/N being provided by 2 suppliers and are experiencing more solder balls on parts from one supplier than the other. These manifest only during the hotbar process. The only difference I can see so far is that the ones experiencing the issue have less solder deposited on them, but the solder volume is consistent from lot to lot, where the incidence of solder balls is not. Thoughts on how to address? Are there hotbar process troubleshooting guides to address this kind of topic? I could not locate any. Thanks.

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#87950

Hotbar Soldering Troubleshooting | 11 May, 2022

Could the plating be oxidized, and repelling the solder instead of adhering?

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#87952

Hotbar Soldering Troubleshooting | 11 May, 2022

I have only hot barred with reflowed solder and no clean flux. And it works well for us.

Can you try tinning some of the Leads ahead of hotbarring? Or maybe try cleaning some with flux.

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#87954

Hotbar Soldering Troubleshooting | 11 May, 2022

The leads on the FPC are pre-tinned on both sides with SAC305. The receiving leads are AU. We do not experience any wetting issues that would suggest oxidation.

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#87955

Hotbar Soldering Troubleshooting | 11 May, 2022

The leads on the FPC are pre-tinned on both sides with SAC305. The receiving leads are AU. We coat all surfaces with Kester 979 no-clean flux dispensed via pen prior to initiating the hotbar cycle.

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#87956

Hotbar Soldering Troubleshooting | 11 May, 2022

The leads on the FPC are pre-tinned on both sides with SAC305. The receiving leads are AU. We do not experience any wetting issues that would suggest oxidation.

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