Semiconductor Packaging:  Wirebonding Process

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See Also: Wirebonding Bonding Theory Semicon Manufacturing Assembly Equipment Bonding Wires Bonding Tools Bond Strength Tests Bond Lifting

Common Wirebond-related Failure Mechanisms:

Ball Bond Lifting - detachment of the ball bond from the silicon chip; also refers to non-sticking of the ball bond to the bond pad.

Common Causes: contamination on the bond pad, incorrect wirebond parameter settings, instability of the die during bonding, bond pad corrosion, excessive bond pad probing, Kirkendall voiding, intermetallic spiking due to the Devaney mechanism, excessive thermal stress resulting in excessive intermetallic formation, bond pad metallization/barrier metallization lifting, cratering.

See separate article on ball lifting.

Wedge Bond Lifting - detachment of the wedge bond from the silicon chip, bonding post, or leadfinger; non-sticking of the wedge bond to the bond pad, post, or leadfinger.

Common Causes: contamination on the bond pad or leadfinger, incorrect parameter settings, instability of the die or leadframe during bonding, bond pad or leadfinger corrosion, excessive bond pad probing

See separate article on wedge lifting.

Ball Bond Neck Break - breakage of the wire at the neck of the Au ball bond.

Common Causes: incorrect wirebond parameter settings, incorrect wire looping, die-to-package delamination, excessive wiresweeping during mold, excessive die overcoat, 'bamboo' grain structure due to excessive thermal treatment

Wedge Bond Heel Break - breakage of the wire at the heel of the Al wedge bond.

Common Causes: incorrect wirebond parameter settings, incorrect wire looping, leadfinger-to-package delamination, excessive wiresweeping during mold

Midspan Wire Break - breakage along the span of the wire.

Common Causes: wire nicks or damage, wire corrosion, tight wire looping, excessive wiresweeping, electrical overstress

Bond-to-Metal Shorting - electrical shorting between the bond and a metal line on the die.

Common Causes: incorrect wirebond parameter settings, incorrect bond placement, insufficient bond pad-to-metal distance

Bond-to-Bond Shorting - electrical shorting between two bonds.

Common Causes: incorrect wirebond parameter settings, incorrect bond placement, insufficient bond pad-to-bond pad distance

Wire-to-Wire Shorting - electrical shorting between two wires.

Common Causes: incorrect wire looping, excessive wiresweeping, insufficient wire-to-wire distance

Cratering - silicon damage under the bond pad, the worst of which is when a chunk of silicon is completely detached from the active circuit. 

Common Causes:  incorrect wirebond parameter settings, excessive bond pad probing

See also:  Common Causes of Wirebonding Failures