Metal fusion bonding – Means to apply vibratory solid-state bonding energy to work
Reexamination Certificate
1999-11-08
2001-01-23
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Means to apply vibratory solid-state bonding energy to work
C228S004500, C228S006200
Reexamination Certificate
active
06176414
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a tool for use in the bonding of wire to semiconductor devices and, more particularly to a linkage guided bond head for bonding a fine wire to semiconductor devices.
DESCRIPTION OF THE RELATED ART
Modern electronic equipment relies heavily on printed circuit boards on which semiconductor chips, or integrated circuits (ICs), are mounted. The mechanical and electrical connections between the chip and the substrate have posed challenges for chip designers. Three well known techniques for interconnecting the IC to the substrate are: wire bonding, tape automated bonding (TAB) and flip-chip.
The most common of these processes is wire bonding. In wire bonding, a plurality of bonding pads are located in a pattern on the top surface of the substrate, with the chip mounted in the center of the pattern of bonding pads, and the top surface of the chip facing away from the top surface of the substrate. Fine wires (which may be aluminum or gold wires) are connected between the contacts on the top surface of the chip and the contacts on the top surface of the substrate.
A wire bonding apparatus electrically connects a semiconductor chip to a substrate, using metal wires which are widely used in the manufacturing process of electronic components. A typical wire bonding machine consists of a bond head, an X-Y table, a workholder and optics.
The bond head is a mechanism which holds the bonding tool and welder (usually an ultrasonic transducer) and moves it perpendicular to the device to be bonded so that it can touch down on the spot where welding is to occur. The bond head also has wire clamps which grip the wire at the appropriate point in the bonding cycle so that the wire can be broken when the interconnection between the device and the lead frame is complete. The X-Y table is a mechanism for moving the bond head in the plane of the device so that the head can move from one bond location to another. The workholder is a mechanism that holds the work rigidly, and may also heat the device to make welding easier. The optics aim the bond head at the appropriate bond pads.
Early bond heads were aimed and moved by the machine operator. Today, conventional machines are moved by electric motors, controlled and aimed by an onboard computer, and bond up to 12 wires per second on devices that may contain in the order of 1000 bond pads.
Due to the small scale of today's integrated circuits, the bond head must be guided in its descent to the device by a mechanism which prevents any unwanted sideways motion in order to prevent the mechanism from missing a bond pad.
In conventional bonding machines two types of mechanisms are currently employed. The first mechanism is a pre-loaded linear slide mounted perpendicular to the work. The second mechanism is a ball bearing or other rotary bearing mounted in the middle of the head, allowing the bond head to pivot like a seesaw. The bonding tool is mounted at one end of the bond head and a linear electric motor is mounted at the other end of the bond head.
Linear bond heads have a disadvantage in that linear bond heads have high inertia and friction resulting in a slower mechanism as compared to a pivoting bond head. The Pivoting bond head also has a disadvantage, however, because the pivot centerline needs to be at the same height as the plane of the device to be bonded. As a result, a pivoting head cannot bond very large devices because the pivot bearing will hit the edge of a large device if it reaches out too far. This is analogous to the limit that the vertical member of a “C” clamp imposes on how far the clamp can reach, or how deep its throat is.
In
FIG. 1
, a conventional pivoting bonding machine
100
is shown. In
FIG. 1
, bonding machine
100
includes bond tool
102
attached to bond head
104
. Bond tool
102
comprises ultrasonic transducer
122
and capillary
128
.
As explained above, the bond head
104
pivots about bearing
106
. The distance between the tip
108
of bonding tool
102
and the front portion
110
of bearing
106
is shown as distance dl. Distance d
1
is finite due to the design constraints of the bonding machine
100
and has a direct effect on the size of device that can be bonded by bonding machine
100
. The center
112
of bearing
106
and the tip
108
of bonding tool
102
forms a pivot centerline
114
that lies in the bond plane of the device to be bonded (not shown) when the bond head
104
is in the head down (bonding) position.
FIG. 2
is a simplified side view of the conventional pivoting bond head.
SUMMARY OF THE INVENTION
To solve the aforementioned disadvantages of conventional bond heads, the present invention relates to a linkage guided bond head for use with a bonding machine.
The bond head comprises an arm assembly, and a linkage coupled between the arm assembly and the frame of the bonding machine. The linkage forms a virtual pivot point below a lower surface of the arm assembly.
The present invention further relates to an apparatus comprising a bond head disposed over a bond plane, a first linkage coupled between the bond head and the frame of a bonding machine and a second linkage coupled between the bond head and the frame the bonding machine, where the longitudinal axis of the first and second linkage intersect at a virtual point below the lower surface of the bond head.
The present invention also relates to an apparatus for bonding wires to a semiconductor device for use with a translation table. The apparatus comprises a fixed link; a coupler link; a first pivot member detachably coupled to the fixed link and the coupler link at a anterior portion of the coupler link, the first pivot member having a first longitudinal axis; a second pivot member detachably coupled to the frame member and the coupler link at a posterior portion of the coupler link, the second pivot member having a second longitudinal axis. The intersection of the first longitudinal axis and the second longitudinal axis forms a virtual pivot point below a lower surface of the coupler link.
These and other aspects of the invention are set forth below with reference to the drawings and the description of exemplary embodiments of the invention.
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patent: 5897048 (1999-04-01), Cheng et al.
Johnson Jonathan
Kulicke & Soffa Investments Inc.
Ratner & Prestia
Ryan Patrick
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