The design of wedges over the last ten years
has changed very little with the exception of the introduction of deep
access wedge bonding. Most bonder manufacturers now offer a wedge bonder
that enables the wire to travel through the center or down
the back of the wedge vertically. The tip
configurations on these deep access wedges are generally the same as those
offered for conventional bonding. The two tip configurations of wedges Gaiser offers are the V-notch and Maxiguide style.
Cross-sectional view of a V-notch wedge identifying the standard dimensions.
view of a Maxiguide wedge, identifying the standard dimensions.
There are several advantages to wedge
bonding. One advantage is the ability of wedges to accommodate the increasing demand for
bond-pitch applications below 0.004in./102µ. Another advantage is that the wire has
minimal bond deformation width so the wire can be placed on a very narrow pad. In many
cases, these two are related. Likely the greatest advantage is the wedge bonding allows
the bonding of aluminum wire. Another advantage of wedge bonding over ball
bonding is the ability to bond down into deep cavities and packages.
Standard wedge tool
lengths are available up to 1.078in./27mm as compared to 0.750in./19mm tool lengths
for ceramic capillaries. The problem with conventional wedge bonding down into these deep
geometry's has been that, even with a 60° wire feed angle, the wire can interfere with
the package wall or another device. Deep access wedge bonding differs from conventional
wedge bonding by feeding the wire down through the center of the wedge. Deep access wedge
bonding allows accessibility similar to a capillary.
wedge bonding has limited accessibility due to the wire and clamp being located behind the
access wedge bonding utilizes a through-the-wedge design. The wire feeds down through the
center of the wedge, exits the wedge and then re-enters the wedge at the tip. This design
allows for accessibility similar to a capillary.
A principle disadvantage of wedge bonding is
the wire is fed at a 30°, 45° or 60° horizontal angle rather than
perpendicular as in ball bonding. Also, wedge bonding is unidirectional.
This is slower than ball bonding which is
multi-directional. Wedge bonding requires the circuit workpiece or the bonding
head to rotate to allow for the wire to bond in the appropriate direction.
A typical integrated circuit wedge bonded with aluminum wire on an automatic bonder.