The general design rule for the hole diameter
(H) is: H = 2 x Wire Diameter (WD). For gold wire, the H can be smaller than
2 x WD so as to improve the
wire guiding capabilities. For aluminum wire,
reducing the H to WD ratio can lead to excessive build-up in the hole area
and possible wire scratching.
This scratched wire can be due to:
being directed to the hole of the wedge at an incorrect angle
edge in the hole
being too small for WD
coming off the spool already scratched
clamp not being adjusted correctly
If the wire is intentionally being fed to the
wedge at a different angle than the wire feed angle of the wedge, wire
scratching may occur. It can be minimized by special polishing of the
countersink area (see Wedge Finish below.) In many cases, the H dimension
be maintained to the H = 2 x WD ratio and wire
guiding can be improved by using a maxiguide wedge. Also, all Gaiser wedges
are manufactured with a polished hole. This enhances wire feeding and
reduces the chance of wire scratching.
This photo shows a side view of a V-notch wedge. Note the relief notch between the bond
foot and the wire feed hole.
This photo shows the bottom view of the tool in Figure 27. The bond foot is in focus with
the FR to the left. The dark circle in the center of the wedge is the hole.
Pictured here is a side view of a maxiguide wedge. Note the lack of the relief notch from
This photo shows the bottom view of the maxiguide wedge. The side walls guide the wire
beneath the bond foot.
Figure 31 & 32.
A comparison of wire guiding between a V-notch wedge and a maxiguide wedge is shown above.
The V-notch wedge provides less wire control. Quite often, the wire exhibits memory
retention from being wrapped on a spool. This causes the wire to want to feed to one side
after exiting the hole. The maxiguide wedge helps align the wire under the center of the
A design that provides
enhanced wire guiding and looping characteristics is the oval hole.
Pictured above is an oval hold wedge. The oval hole design has a hole width that is
narrower than the hole height. This hole design provides optimum wire placement control
while still providing good looping.