Metal fusion bonding – Means to apply vibratory solid-state bonding energy to work
Reexamination Certificate
2000-05-12
2002-05-07
Dunn, Tom (Department: 1725)
Metal fusion bonding
Means to apply vibratory solid-state bonding energy to work
C228S004500, C228S110100
Reexamination Certificate
active
06382494
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to machines and apparatus for forming ultrasonic wire bonds on miniature workpieces such as microcircuits and read/write heads of the type used to read and write data from and to disk memories. More particularly, the invention relates to an automatic ultrasonic bonding machine having an ultrasonic bonding tool which protrudes downwardly from a vertically tiered stack of orthogonally translatable tool support platforms, each having a separate motor drive, which when driven by computer generated command signals, automatically translates the tool in three dimensional space to thus position a wire end protruding from the tool tip at precisely pre-determined locations on a workpiece and form ultrasonic bonds at those locations by energizing an ultrasonic transducer rigidly coupled to the upper end of the tool.
B. Description of Background Art
A large variety of scientific procedures, medical procedures and industrial processes require the use of a type of apparatus referred to generally as a micro-manipulator for the precise positioning of a tip of a tool or instrument relative to a small workpiece or other such object. For example, the manufacture of electronic components such as integrated or hybrid microcircuits requires the use of a micro-manipulator-type apparatus, for the following reasons.
Integrated circuits are fabricated from thin slices of a semi-conducting material such as silicon, germanion, or from gallium arsenide or other III-V compounds, i.e., compounds of elements from columns three and five of the periodic table. The slices are cut into small squares or rectangles referred to as chips or dice, ranging in size from squares about 100 mil (0.100 inch) on a side to several hundred mils. Transistors, diodes, resistors and interconnecting circuit paths are formed on each chip or die by diffusing impurities into selected regions of the die to produce a desired electrical conductivity. Various conducting paths and insulated layers are then deposited on the chip.
After a semi-conductor chip or die has been fabricated as described above, it must be attached to a base or carrier. A lid is then sealed to the base to form a package or container which protects the delicate die from damage. Prior to attaching the lid to the carrier which supports the die, conductive pads which provide input and output conductive paths to the die must be electrically interconnected to more robust leads or terminals which extend outward from the carrier. These interconnections are customarily made using fine aluminum or gold wires. The wires are ultrasonically or thermo-sonically welded to the pads and external leads by a bonding tool that applies ultrasonic energy, or a combination of heat and ultrasonic energy, to a bonding site. Since the connection pads of a microcircuit are extremely tiny and closely spaced, great precision is required in positioning the tip of a bonding tool relative to the microcircuit.
Responsive to the need for an apparatus capable of precisely positioning the tip of an ultrasonic transducer to form wire bonds on microcircuit chips, the present inventor invented a micro-positioner apparatus which employs a novel pantograph-type manipulator input mechanism. That apparatus, which was disclosed in the present inventor's U.S. Pat. No. 3,474,685 and issued on Oct. 28, 1969, has proven to be highly effective in performing its intended functions, and wire bonding machines employing the novel design concepts including the pantograph mechanism disclosed in that patent are widely used throughout the electronics industry. However, the present inventor found that certain aspects of the micro-positioner disclosed in the 3,474,685 patent might be improved upon. For example, the allowable working or throat depth of the ultrasonic tool tip would preferably be larger for certain bonding applications. Also, the use of offset pivotable mountings for the transducer tool support plate would desirably be minimized, thereby minimizing the requirement for springs to counter balance unbalanced forces exerted in supporting the tool support plate by offset mountings. Moreover, it would be desirable to have a micro-positioner apparatus in which various ultrasonic transducers and other bonding tool accessories such as wire spooling mechanisms, some of which might be substantially heavier than conveniently supportable by prior art micro-positioners, could be used. Such a need arises, for example, in bonding tie heavier wires required for connection to certain electronic components such as wound coils and disk drive components. In response to those considerations, the present inventor disclosed a Micro-positioner For Ultrasonic Bonding, U.S. patent application Ser. No. 08/773,637 filed Dec. 24, 1996, now U.S. Pat. No. 5,871,136. In that patent the present inventor disclosed a micro-positioner apparatus having a pantograph-like input manipulator mechanism, and a follower mechanism coupled to the input manipulator mechanism by a ball joint and supporting an ultrasonic transducer housing and bonding tool on a tool support plate. The tool support plate is longitudinally slidably mounted on a tool support guide plate, allowing fore and aft motion of the tool tip. The tool support guide plate is in turn pivotably supported by a yoke having a yaw pivot bearing which allows lateral motion of the tool tip. The yoke is in turn supported by a pitch pivot bearing having a horizontally disposed pivot axis, thereby permitting pivotal motion in a vertical plane of the yoke, tool support plate, and tool tip. By a suitable choice of spacings between the pivot axes of the pantograph input manipulator mechanism, support bearings and ball joint, the tip of the bonding tool is caused to move in coordinate directions of a second coordinate system containing the tool tip in precisely scaled ratios of corresponding motions in a first coordinate system of an input control knob on the input manipulator mechanism. The combination of a longitudinally slidable tool support plate with two pivot bearings orthogonal to each other and to the platform axis, provides a micropositioner apparatus which has both a rugged construction capable of supporting heavy loads on the tool support plate, and a substantial throat depth. In a preferred embodiment of the disclosed apparatus, the longitudinal platform axis of the tool tip, and the pivot axes of the pitch and yaw pivot bearings all intersect at a common point, thereby assuring completely orthogonal motions of the tool tip in three orthogonal coordinate directions that are precisely scaled fractions of corresponding input control knob motions.
In U.S. patent application Ser. No. 09/153,206, filed Sep. 15, 1998, now U.S. Pat. No. 6,164,514, the present inventor disclosed a micro-manipulator for ultrasonic bonding applications having a manipulator input mechanism and tool holder follower mechanism which are both pendent from an overlying support structure, thereby affording a work space of potentially unlimited lateral extent below the apparatus. Among other advantages, the large work space can accommodate workpieces located on a conveyor belt disposed below the apparatus.
The micro-manipulator apparatus disclosed in the pending application identified above provides means for dynamically positioning an implement relative to a workpiece, particularly an ultrasonic bonding tool tip relative to a miniature electronic component, moving the tool tip into contact with a selected bonding site to permit formation of a bond by application of ultrasonic energy to the bonding site, and withdrawing the tip upon completion of the bond. A preferred embodiment of a micro-manipulator apparatus according to the prior invention disclosed in the pending application includes a manually operable manipulator input mechanism coupled by means of a ball joint to a follower mechanism which includes a tool support structure for holding an ultrasonic bonding tool or similar implement. Position commands input to the manipulator in
Chapin William L.
Cooke Colleen P.
Dunn Tom
West Bond Inc.
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