Page 77 - Wire Bonding in Microelectronics

56 Cha pte r T h ree

99.99% Gold + beryllium hard, as-drawn
21
ASTM F72
20
Breaking load
(g) 19
18
17
2
% Elongation 1
0
0 2 6 12 24 50 78 104
Weeks

99.99% Gold + beryllium. Stress-relieved,
1–3% elongation
11
Breaking load
(g) 10
9
2
% Elongation 1
0
0 2 6 12 24 50 78 104
Weeks
99.99% Gold + beryllium. Annealed,
4–7% elongation
8
Breaking load
7
(g)
6
7
% Elongation 6
5
0 2 6 12 24 50 78 104
Weeks

FIGURE 3-3 The shelf-life aging of bonding wire for 25 µm diameter, gold wire
with <10 ppm Be, in hard as-drawn, stress relieved, and annealed condition.
[From ASTM F 72-revised in (2006). Copyright ASTM. Reprinted with
permission.]

better neck and looping characteristics, etc.). In contrast, Al wire pri-
marily still uses the same 1% Si alloy, and thus has changed little,
improving primarily in uniformity and reproducibility.
No equivalent aging studies have been conducted on larger-
diameter bonding wire, (~100 µm, 4 mil) diameter and larger. How-
ever, most large-diameter aluminum wires currently used for power
devices are of 99.99% Al. These wires are generally used in the