We are a PCB mfr and we had recently fabricated a 6 layer PCB with 1mm thickness with blind vias. The design has the blind vias right underneath the BGA area of the PCB and the ENIG plated board undergoes multiple reflows during the leadfree assy. We use Isola 370HR for this, which is leadfree. We had observed a few delamination in this area after assy. 

Is it recommended practice to have a blind via right underneath the BGA area which undergoes multiple reflow cycles. Can you share your views

rgds

Pradeep

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Micropack Ltd, Bangalore, India

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