Page 137 - Wire Bonding in Microelectronics

W ir e Bond Testing 115

Shear testing has been used for years to test the integrity of TAB
bumps at the wafer level. It was also used to measure the strength of
the bonding between the TAB lead and the bump as well as the lead
buckling force [4-46]. Typically, such tests were performed with a wire-
bond ball-shear tester. The shear test is universally used to determine
the strength of solder balls on chips for flip-chip attachment.

4.3.11 Ball-Shear Test Standardization
The ball-shear test is used in essentially all major semiconductor
assembly facilities around the world to control ball-bond production
for all but the finest pitch. There are two published standards on its
usage, as well as many internal company manufacturing specifica-
tions. The first standard specification was published by ASTM in 1990.
It is ASTM F 1269, and was updated in 2006. It is test methods for
shear testing of ball bonds. This test was originally documented by a
round robin involving six cooperating laboratories [4-47]. The EIA
JEDEC committee JC-14.1 has issued a shear test standard which is
available on the Internet as a JEDEC (commercial) standard (www.
jedec.org/download/search/22b116.pdf): Wire Bond Shear Test
Method, EIA/JESD22-B116. This test contains recommended shear
test values, see Fig. 4-23. It is now called out in MIL-STD. 883G/H.

Minimum shear values
50 75 100 125 µm
110
100 Minimum shear values for
90 Au-Al (top) and monometallic
bonds (bottom)
80 Preferred min individual
Shear strength (gf) 60 shear [5.5 g/mil (84 MPa)]
70
2
for Au-Al bond reliability
50
40
30
20
10
0
1.75 2.0 2.25 2.5 2.75 3.0 3.25 3.5 3.75 4.0 4.25 4.5 4.75 5.0 5.25
Ball bond diameter (mils)
FIGURE 4-23 Modifi ed minimum recommended ball-shear test values given in the
EIA/JESD22-B116 document. The recommendation would be improved if the top
curve at 84 MPa (5.5 g/mil ) was the minimum shear reading for Au-Al bonds.
2
However, monometallic bonds should be reliable on the lower line. (This Document
is on the Web. It may be subject to revision.)