Problem with LGA bridging

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Any help is greatly appreciated, see attached picture, this ... - Apr 17, 2024 by sw1234

Is your stencil worn out? If your once flat stencil is now w... - Apr 18, 2024 by DWL

sw1234

#90883

Problem with LGA bridging | 17 April, 2024

Any help is greatly appreciated, see attached picture, this board used to run fine but in the last two batches have 5% of boards with bridging/voids. Stencil is 4 mil, aperature is 1:1, LGA package mounted on gold plated boards, SAC305, the same oven profile has been used for years without issues.

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DWL

#90891

Problem with LGA bridging | 18 April, 2024

Is your stencil worn out? If your once flat stencil is now wavey, you will be depositing more paste. Ideally, you'll have historic SPI data to compare known good volumes from past prints to the current.

Another possibility is moisture. Bake your boards and parts to be sure they are dry. Also check your paste. if the ambient humidity is higher, or the paste has sat out longer, it might be absorbing moisture. When it boils off during reflow, this can create voids and push solder off of the pad as it outgasses.

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