Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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Mosfet stencil design

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Mosfet stencil design | 18 July, 2005

I have a SO-8 mosfet part from Vishay SI7846DP-T1. Am having a lot of solder ball that coming underneath the part. Am currently using a 5 mils with a window design for my stencil. Those anyone have experience or have any suggestion for an aperture that will eliminate solderball.



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Mosfet stencil design | 19 July, 2005

You may want to try reducing the large center aperture on your stencil to 50-70% of the area of the pad. This is what we do with QFNs and it may be applicable in this case also.

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Mosfet stencil design | 21 July, 2005

We agree with Russ. The solderballs are probably the result of printing too much paste on the board.

In designing your 5 thou thick stencil: * Aperatures for the pads should be identical to a IPC-7351 - SO8 [or worst case ] * Aperatures for the heat slug should be the same is as the pads, but only cover 50% of the heat slug area.

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