Page 111 - Wire Bonding in Microelectronics

90 Cha pte r F o u r

0.12 3.0
A

0.10 10 mm (0.4 in) bond length 2.5

Loop height (in) 0.08 5 mm (0.2 in) bond length B 2.0 Loop height (mm, approximate)

1.5
0.06

0.04 2.5 mm (0.1 in) bond length C 1.0

0.02 0.5
0 4 8 12 16 20
Wire elongation (%)

FIGURE 4-7 The effect of wire elongation on the fi nal loop height at the point
of wire rupture during a bond pull test. All bonds had the same initial loop
height, 0.5 mm (20 mils), but three different bond-to-bond lengths were used
as indicated.

600
A

C
500 2.5 mm (100 mil) bond length B
Bond pull strength (gf) 400 5.0 mm (200 mil) bond length
10.2 mm (400 mil) bond length

300

200

100
0 4 8 12 16 20
Wire elongation (%)

FIGURE 4-8 Bond-pull force and wire breaking force versus wire elongation.
The solid curves are bond-pull forces based on the geometries of similar
lettered curves in Fig. 4-7.