Printed circuit board has blind holes for conducting passages between middle and upper conducting layers to prevent solder protrusions from interfering with head of screw fastener

摘要

Substrate layers (2,3) are sandwiched between conducting layers (6,7,8) that stop short of the passage (15) for the fastening screw shank (16). Within the diameter of the screw head (18) is a number of blind holes (20) forming a circle concentric with the passage. Metallized walls (21) make electrical contact between the upper and inner conducting layers.