Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Via in pad

Scott B

#29051

Via in pad | 11 June, 2004

We currently have an issue with via's in pads which we have been living with for some time. The problem has now escalated with the need to increase the via hole size to achieve PCB fabricators aspect ratio's. We are now not only experiencing solder drain from the joint but due to the increased via size we are also finding that the solder runs straight through the via forming solder balls on the underside of the land.

Via plugging is being investigated but is unlikely to be qualified.

Any ideas?

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#29052

Via in pad | 11 June, 2004

Have your designer place the via on the edge of the pad, centered and cover it with soldermask. If this is a leadless capacitor or resistor-style component, the corresponding pads will need to partially covered with solder mask to match the via in pad.

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Scott B

#29054

Via in pad | 11 June, 2004

Forgot to say that redesign has been argued and rejected for over 3 years.

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#29055

Via in pad | 11 June, 2004

We figured you were going to say that. Pay me now, or pay me later, you call it.

As an alternative: * Cover the backside of the via with masking tape that will take soldering temperature, like Kapon, or a temporary solder mask * Enlarge the aperture of the viaed pad to compensate for filling the via with solder * Print paste on the topside of the via, reflow, etc as you normally do * Remove tape, TSM, whatever

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