via failure

I've seen this happen a couple of times, and it was a problem with control of the plating process (IIRC) leading to cracking of the plated through hole plating at the interface with the pad. Nasty, and if you buy 100% tested boards you have no idea how many they threw away to get ones that test good (for now). There are a lot of board suppliers out there, suggest you move on.

Best regards, Spehro Pefhany

Yes, should be a thing of the past.... send the faulty ones back and ask them to microsection to see exactly the problem.Yes, you will have to strip off the components. As the next guy said, time to find a new supplier. If they can't get that right, what else (hidden) are they getting wrong?

We had a few instances of this, it turned out to be trapped air in between the FR4 layers, when the board is heated it forces the layers apart and breaks the via. Sometimes the air pocket is big enough to be seen. Basically poor process control at the bare-board manufacturer.

Our board stuffer buys their bare boards from some far eastern supplier, they changed suppliers and the problem went away.

There can be a problem with the drilling of vias. This tends to only show on the vias to internal layers.

Too small of a copper ring around the internal part of the via can cause increased troubles.

If the plating process insn't done right, the vias can have thing spots. These can sometimes lead to vias that blow out when you apply high currents to them but look good before that.

My supplier had such problem when they moved to ROHS, took them a while to figure it out and it is now a thing of the past.

M**** Circuits did this to us: bad inner-layer plating, 100% "tested" boards. They claimed that bare-board testing involves "some operator judgement."

I don't know if they are still in business.

ftp://jjlarkin.lmi.net/BadVia1.jpg

ftp://jjlarkin.lmi.net/BadVia2.jpg

ftp://jjlarkin.lmi.net/BadVia3.jpg

I wouldn't use that vendor again.

Some board houses make extra boards, stash the leftovers (and maybe rejects?) and later sell you small quantities out of the stash. One house used to send out an annual offer to sell the leftovers to pay for their Christmas party.

John