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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Psi on November 18, 2015, 08:25:19 pm

Title: 0.4mm BGA vias
Post by: Psi on November 18, 2015, 08:25:19 pm

Hi,

Can anyone tell me if I need to use single layer microvia for 0.4mm BGA pad breakout?
Or can I use a normal laser drilled via through the entire PCB (0.8mm) done as a offset via?
I'm just not sure about a via through the entire board with regard to solder disappearing down the hole.

The other option is a via in pad which i assume must be a microvia so the solder can only go down 1 layer into the pcb

The BGA in question is only a small one, 2.5mm  and 25 ball

Any help appreciated

Title: Re: 0.4mm BGA vias
Post by: cat87 on November 19, 2015, 06:57:20 am

I don't know if this helps or not, but on all the  PCBs with BGAs I've seen (large or small BGA packages) I have never seen vias that go through the entire PCB stack. Instead, I've only seen blind vias, that go down to an internal layer of the PCB and those were micro-vias: 0.4mm or maybe smaller. The PCBs made are for the aerospace industry, so I can not be sure if in commercial products, this practice also stands  true or not.
At work, we have an X-Ray  machine that has a tilting table , so it's easy for me to see how far down the vias go. Unfortunately, I do not have any pictures available

Title: Re: 0.4mm BGA vias
Post by: Neilm on November 19, 2015, 07:04:56 pm

Quote from: cat87 on November 19, 2015, 06:57:20 am

I don't know if this helps or not, but on all the  PCBs with BGAs I've seen (large or small BGA packages) I have never seen vias that go through the entire PCB stack.

I have seen vias going through the whole board under a BGA. It was a small one that didn't run too fast and was in a metal box for shielding, but even so I was very surprised - the 0V plane was full of holes.  I have seen very small BGAs routed without many vias under them but I certainly wouldn't like to.

Title: Re: 0.4mm BGA vias
Post by: Psi on November 19, 2015, 07:56:11 pm

Quote from: blueskull on November 19, 2015, 07:18:07 am

You can use via in pad with plated plugged vias, so that it will have exactly the same solderability and surface condition like just all other parts of the board.

AFAIK this process is cheaper than micro vias or more aggressive HDI technologies. Blind vias is another option, probably cheaper, but definitely not flat.

If you can afford using 0.5mm pitch parts, it will be much easier to do.

Also, I'm curious what 0.4mm 25 pin 2.5mm*2.5mm part you are referring to, is it an ice40?

Cool, plugged and plated via in pad sounds like the way to go.

Chip is quite new, BQ25120.
Just a battery charge / management chip