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Problems with Component Tombstone on Flex Circuit

  Question: Can you tell me if there are other reasons that components tombstone? We have looked at the pad size and the amount of paste on the pads. If this helps, the laminate is flex kapton.

 

Question: Can you tell me if there are other reasons that components tombstone? We have looked at the pad size and the amount of paste on the pads. If this helps, the laminate is flex kapton.

Answer: Some of the reasons for tombstoning are related to solder paste quantity, land area sizes, solder mask between pads, thermal gradient between the two pads as some pads have a larger heat sinking capability than the other pads and last but not least, allowing the solder to reflow first on one side before the other side reflows, which can cause the component to tombstone.

From a process perspective, the issue is vibration with flex type of materials. The component could be more in contact with one pad than the other and the wetting of the unreflowed solder paste could pull up the component and cause it to tombstone.

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