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Bigger particle size solder paste helps reduce via hole problem?

Views: 3647

#64393

Bigger particle size solder paste helps reduce via hole problem? | 1 June, 2011

I have one pcb which has via holes on both solder pads of 0402 chips.

Right now im using type 3 solder paste with 45 degree squeegee. and a lot of these chips are tombstoning.

Im guessing with larger particle size of solder paste, the solder will be more unlikely to go into the via holes...

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#64397

Bigger particle size solder paste helps reduce via hole problem? | 1 June, 2011

Try shifting the placement location slightly toward the pad that is not soldered. This is assuming it is always standing up on the same pad

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#64398

Bigger particle size solder paste helps reduce via hole problem? | 1 June, 2011

I don't believe that particle size of the solderpaste will offer you any relief from this issue. The solder flows into the via, leeching away from the desired solderpoint, after the solder has become liquious. The chemical make-up of the solder controls the temperature at which it becomes liquious, not the particle size. I think your best course of action would be to have the PCB artwork modified to include a soldermask dam that seperates the via from the intended solderpoint.

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#64403

Bigger particle size solder paste helps reduce via hole problem? | 2 June, 2011

1 chip has 2 solder pads....and both pads definitely has solder.... im not getting what you are trying to say.

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#64404

Bigger particle size solder paste helps reduce via hole problem? | 2 June, 2011

1 chip has 2 solder pads....and both pads definitely has solder.... im not getting what you are trying to say.

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#64406

Bigger particle size solder paste helps reduce via hole problem? | 2 June, 2011

You need to post a picture or describe your geometry better. Is this a through hole via in pad or is the via offset from the pad with no soldermask in between?

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#64407

Bigger particle size solder paste helps reduce via hole problem? | 2 June, 2011

Al: We agree with AVFOM. You have a different problem than solder paste mesh selection.

Most often, tombstoning occurs when the wetting forces on the two pads are unequal. Examples of things that can cause this are: * Pads are different * Board pad size and / or gap are too large * Amount of solder applied to the connections is different * Terminations on the component are different * Component is placed away from the center of the two pads * Heating of the component is uneven

Search the fine SMTnet Archives for more on this topic. Here's an example http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=58607

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