Page 76 - Wire Bonding in Microelectronics

Bonding W ir e Metallur gy and Characteristics 55

1% Silicon aluminum. Hard, as-drawn.
21
ASTM F487
20
Breaking load 19
(g) 18
17
16
3
% Elongation
2
0 2 6 12 24 50 78 104
Weeks
1% Silicon aluminum. Stress-relieved, 12–16 g. B.L.
15
Breaking load 14
(g)
13
4
% Elongation 3
2
0 2 6 12 24 50 78 104
Weeks

1% Silicon aluminum annealed, 8–12 g. B.L.
11
Breaking load 10
(g)
9
2
% Elongation 1
0
0 2 6 12 24 50 78 104
Weeks

FIGURE 3-2 The shelf-life aging of bonding wire for 25-µm diameter, Al 1% Si,
wire in hard as-drawn, stress relieved, and annealed condition.
[From ASTM F 487-revised in (2006). Copyright ASTM. Reprinted with permission.]

Even after the ASTM tests, some occasional users prefer to dis-
pose of wire within 6 months or so. One rationale is that the ambient
as well as the general handling of the wire cannot always be assured
over a 2-year period. Another is that the micrometallurgy of modern
Au wire has changed since the ASTM data were taken and its aging
characteristics have not been studied. We note small-diameter Au-
wire has improved considerably in that time (more stable, stronger,