Page 47 - Wire Bonding in Microelectronics

26 Cha pte r T w o

Ball Thin, brittle film
(Au, Cu) (Al 2 O 3 , SiO 2 , SiN, etc.)

Metal deforms,
shattering thin brittle film

Deforming ball pushes
shattered film aside into
debris zones. Clean metals
plus ultrasonic energy form
a bond.

FIGURE 2-13 The bonding force and US energy breaks through thin surface-
oxide-fi lms, pushes them aside, and US energy forms the weld.

FIGURE 2-14 An ultrasonic wedge bond made with normal parameters for a
manual wedge bonder using 25 µm diameter Al, 1% Si wire. The bond (on the
left) has been partially lifted up so that the weld pattern may be seen. The
center remained unwelded. On the right, is a bond pad with a similar bond
completely removed.