A Weak Inner-Layer Interface Can Open After Soldering Heat

What the evidence preview establishes

Inner-layer copper separated from electroless copper in plated-through component holes. As-fabricated comparisons already contained partial weakness, while soldering heat and drill breakout aggravated the failed connections.

Why this case matters

For an open near a plated-through joint, electrically bracket the fault, section the component hole, compare unassembled coupons, and separate pre-existing interface weakness from assembly damage.