Capillary Design Rule

One of the basic principles to achieve an optimized wire bonding process is through a proper capillary design selection. The synergy of different process variables coming from wire, substrate, bond pad metallization, and wire bonder is influential to final geometrical design of the capillary.

Abbreviation used for Capillary & Wire Bonding:

Bond Pad Pitch (BPP) – is defined as the center distance between two adjacent bond pads.

Bond Pad Opening (BPO) – is defined as the unpassivated area of the bond pad where the actual ball bonds are ultrasonically welded.

Critical Loop Height (CLH) – is defined as the height of the loop that is in-line with the centerline of the capillary when viewed from the side or parallel to the adjacent wire. Once the wire passed the centerline, the capillary has already cleared and no adjacent loop disturbance is observed.