0.4mm Pitch BGA is Awesome

I recently had a conversation with a friend about 0.4mm pitch BGAs. The specific part is the Freescale FreescaleKL03KL03 ARM Coretex-M0+ microcontroller in a 1.6mm x 2mm, 04.mm pitch package. That's a 20 ball wafer scale BGA form factor.

I don't have an actual part to photograph next to a grain of sand, but trust me (or don't), it's really small.

Ti 0.44 pitch dimensionsThe challenge, and the reason I suggested a QFN form factor instead, is the costs
involved. If you have the extra budget money for more expensive PC boards, then go ahead and use this form factor. You probably won't be able to use this package in cost constrained situations.

The simple reason is that you can't escape route the inner six pins without using super small vias between pads, or in pads and filled and plated over. The page on the left is from a Ti doc, but any variations in geometry will be minor.

You can see that you can't put a trace between the pads. Maybe a 2 mil trace, but maybe not. There just isn't much room. The recommended method is to put micro vias in the pads and have them filled and plated over at the board fab house. Never put a via in a micro BGA pad unless it's filled, plated over, and flat.

Duane Benson
There are more things in heaven and earth, Horatio, 
Than are dreamt of in your philosophy.
But open vias in pads aren't one of them

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Comments

I have used SMD type pad for 0.4mm BGA but some guidelines Recommended NSMD.now, i confused which type of the pad is best for 0.4mm bga. please share your knowledge.

I agree that for small volumes, in most cases a larger package like a QFN would be better. But when volumes increase, there can be some really good savings. The reduced form factor can reduce the size of the board, which can offset the costs laser drilling and filled vias.

In small volume settings, laser and filled vias can be very expensive. But at high volumes, they are just another process. Filled laser vias - and components like these - can definitely save a lot of money and design hassle for the right project.

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