BGA Pads with Vias

Via eyeballs

No. This isn’t a closeup of an owl face.

There is still some debate on how best to create a land pattern for a 0.4mm pitch BGA. We recommend solder mask defined pads at that pitch. But that’s not really what this post is about. Although this land pattern uses non-solder mask defined pads which can encourage bridges. If you need to cross a river, encouraging bridges is good. If you’re trying to make a board work, they are not.

In the case of the two BGA pads shown, I really doubt you would have to worry about bridging. That’s because the solder ball would most likely be sucked off the BGA due to the capillary action of the via in the middle of the pad. You most likely wouldn’t get bridging. You most likely wouldn’t get any contact of any kind at all. This will not work.

Duane Benson
Hoot. Hoot.

http://blog.screamingcircuits.com/

About Duane

Duane is the Web Marketing Manager for Screaming Circuits, an EMS company based in Canby, Oregon. He blogs regularly on matters ranging from circuit board design and assembly to general industry observations.
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One Response to BGA Pads with Vias

  1. Mitch says:

    Doing .4mm for over a year now (China manufacturing too), and DO NOT do SMD pads. Learned long ago that that just wasn’t preferred by manufacturing, unless you’re using a ‘hard, better aligned’ solder mask. With liquid soldermask it’s nearly impossible to control your tolerances to give you proper solder mask coverage you’re trying to get. Nope. Would not recommend SMD pads. FYI – for .4mm pitch we’re doing .25mm pads and allow the pcb manufacturers to ‘open’ the solder mask per their process.
    Assembly with non-SMD pads on .4mm pitch? EXCELLENT