In microelectronic packaging technology wire bonding is a common interconnect technique. The quality and reliability of wire bonds are generally evaluated by ball shear and stitch pull testing. From the load versus time and load versus tool tip displacement plots of the shear test, three regions can be observed. Region I primarily exhibits elastic-plastic deformation occur, while crack nucleate in region II which propagates in region III which finally ends in a catastrophic failure. Fractographs reveal in the case of gold ball bonds shows fracture occurs in Al bond pad metallization close to Au-Al intermetallics. In Cu ball bonds of 1, 2, and $4ml$ wire sizes also Al bond pad metallization cracks but penetrate deeper into the pad which indirectly shows that the bonding layer is stronger than that of gold ball bonds. Optical microscopic observation of the sheared copper bond surfaces reveal sticking of Al which provides qualitative information of the area of the bond between the ball bond and the bond pad. In thermally aged gold ball bonds, the gold above the intermetallic layer fractures. The energy required to fracture a gold or copper ball bond of $1ml$ wire size is around $370J∕m2$, while an aged gold ball bond consumes about $520J∕m2$. Void nucleation and coalescence mechanism of ductile fracture takes place in the ball and stitch bonds, however, silicon particles may be the preferential void nucleation sites in bond pad aluminum metallization failures. To understand the second bond strength, a stitch pull test was conducted and the results showed the neck of the stitched wire cracks thus leaving behind a tail bond on the lead finger.

1.
Harman
,
G. G.
, 1989,
Wire Bonding in Microelectronics
,
2nd ed.
,
McGraw-Hill
,
New York
.
2.
Shell
,
M.
,
Guzman
,
D.
, and
Mahaney
,
M.
, 1992, “
The Bond Shear Test: An Application for the Reduction of Common Causes of Gold Ball Bond Process Variation
,”
IEEE Proceedings of International Reliability Physics Symposium
, pp.
251
257
.
3.
Maiocco
,
L.
,
Smyers
,
D.
,
Munroe
,
P. R.
, and
Baker
,
I.
, 1990, “
Correlation Between Electrical Resistance and Microstructure in Gold Wire Bonds on Aluminum Films
,”
IEEE Trans. Compon., Hybrids, Manuf. Technol.
0148-6411,
13
(
3
), pp.
592
595
.
4.
Atsumi
,
K.
,
Ando
,
T.
,
Kobayashi
,
M.
, and
Usuda
,
O.
, 1986, “
Ball Bonding Technique for Copper Wire
,”
Proc. IEEE Elec. Comp. 36th Conf.
,
Seattle
, WA, pp.
312
317
.
5.
Mahaney
,
M.
,
Shell
,
M.
, and
Strode
,
R.
, 1991, “
Use of the In-Process Bond Shear Test for Predicting Gold Wire Bond Failure Modes in Plastic Packages
,”
IEEE Reliability Physics Symposium
, pp.
44
51
.
6.
Murali
,
S.
,
Srikanth
,
N.
, and
Vath
,
C.
, III
, 2003, “
An Analysis of Intermetallics Formation of Gold and Copper Ball Bonding on Thermal Aging
,”
Mater. Res. Bull.
0025-5408,
38
(
4
), pp.
637
646
.
7.
Dodd
,
B.
, and
Bai
,
Y.
, 1987,
Ductile Fracture And Ductility With Applications To Metalworking
,
,
London
.
8.
Enander
,
E. P.
, and
Sjoberg
,
A.
, 1999,
The Matlab™ Handbook, Version 5
,