Actually we have had this problem since the temprature is increased about one month ago . and we had this problem last year .
The matter of fact is the surface of board is metalized well just the metalization in the holes are weak .
We check all of the process such as cleaning , micro-etch, pre - active and specially activation stage. In spite of those stages are correct analitically but some of the holes are weak.
Could you please help us ?
We can discribe more if nessesary.