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BGA - Unmasked Vias

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BGA - Unmasked Vias | 12 July, 2007

I've got a proto build (3 boards) that has a Xilinx FG456 fine-pitch BGA on it. Every BGA pad on the PCB has an unmasked via attached. Between the via and the pad is a thin soldermask strip, maybe .005" wide at best. I am very confident it will bridge. As usual we have time constraints and must use these PCB's. My initial idea is to use a "permanent" kapton stencil beneath the BGA to act as soldermask but maybe there is another way. I do not think we can apply soldermask by hand as the pitch is so tight. Does anyone have advice on how to make this work?

(Pitch is 1 mm, ball dia. is 0.6 mm).

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BGA - Unmasked Vias | 12 July, 2007

Hi Swag,

We do this all the time. If your print is spot on, you should not see any shorting.

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BGA - Unmasked Vias | 19 July, 2007

Thanks - We ended up using a kapton stencil mainly due to the fact that we couldn't get time on the SMT lines. It worked great, protected the vias and the BGA functions fine.

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