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Solder balling under passives

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#76363

Solder balling under passives | 19 September, 2016

Hi guys,

Problem: Mid chip solder balling.

Component affected: 0603 caps only

Defect is PCB specific (Meaning only one PCB is affected as the aperture is standard for that component).

As a containment I'll give a home plate design for the component but by standard we don't use home plate designs for 0603.

I'm seeing mid chip solder ball only at the location where there is a trace beneath the mask.

Any advice or suggestion for this peculiar case?

Thanks

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#76364

Solder balling under passives | 19 September, 2016

Hi Shriram, Are you saying that there is a trace running between the pads for this 0603 capacitor? If so, this design may be causing a gasketing issue between the stencil and the PCB. The uneven height prevents the stencil from sitting flat on the PCB. This unevenness will cause a little more paste to leech out between the stencil and the PCB with the end result being mid-chip solder balls. You are correct to try a home plate aperture as a prevention. It's a cheaper alternative to redesigning the PCB.

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#76366

Solder balling under passives | 19 September, 2016

Whatever the cause is, will be fixed by applying less paste. So Homeplate it is.

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#76369

Solder balling under passives | 19 September, 2016

Appreciate your suggestion.

NSMD pads are used for this design, the anomalies we found are

1. the trace running between pads has a lesser solder mask height compared the other area of the pads.

2. the NSMD pads doesnot have a trench close to pad edge in the pitch area for the affected locations.

Thanks guys.

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