Your English is fine.
Your assessment that corrosion on a portion of the metalization on the end of a component is causing the tombstoning is reasonable. We've seen that before.
Corroded components received from a supplier is not acceptable as an earlier poster correctly stated. But after applying many of these components to each board, seeing many component faults, and doing far more rework than you would like to be doing; I assume you know that, have either scrapped these parts or have changed your solder paste, and are now trying to recover the situation.
Possible causes of this corrosion are: * Poor storage environmental conditions by anyone in the supply chain. For instance, the paper can absorb moisture from humidity in the air and this moisture can cause the corrosion where the component touched the paper. * Poor process control of the paper during its manfacture or processing, allowing basic materials in the paper to react with the metalization of the component terminations. For instance, sulphur in some paper formulations will corrode solder terminations. * Poor component fabricator assembly process. For instance, using corroded materials into their process or allowing corrosion formation during fabrication.
Good luck, this doesn't sound like fun for the Holidays.
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