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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Tombstoning 0402

Alejandro Rodriguez Gallegos


Tombstoning 0402 | 21 December, 2000

Hi Sorry my poor english We have some problems with some componentes 0402 we recived by the manucterer oxide in the tape reells exactly in the bottom side to the reel I think the root cause is the oxide in the tapes rells

What do you think?

And other coment is the reel absorve humidity and the carton increase the sizes

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Re: Tombstoning 0402 | 26 December, 2000

If you have a known problem with the parts, then Reject them back to the Vendor. It appears that you have a solderability issue. As for Tombstoning on 0402 chips, this could trace back to the stencil design and/or machine placement. Define Tombstoning, chips on there sides(soldered at both ends), or one end of the component in pointing upward (only one end soldered). Is there a part to pad mis-match?

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Re: Tombstoning 0402 | 26 December, 2000

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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