Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-11-26
2001-06-26
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S832000
Reexamination Certificate
active
06249963
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of electronic device fabrication, and more particularly to a system and method for coupling conductive pellets to a component of an integrated circuit.
BACKGROUND OF THE INVENTION
Integrated circuit components are electrically coupled to conductive features of electronic devices in which the components operate, for example, a circuit board or other conductive feature. Coupling of components to associated electronic devices often requires the formation of multiple bonds arranged according to the electrical designs of the components and the devices. For example, a ball grid array may have multiple solder or other conductive balls to interconnect the component to the device. The speed at which ball grid arrays can be properly formed and coupled to the associated devices significantly affects the speed, productivity, and overall efficiency of device fabrication.
As the electronics industry continues its intensive pursuit of reduced manufacturing costs and increased speed, precision, and productivity in device fabrication, forming ball grid arrays in an efficient and reliable manner has become increasingly important to replace conventional quad flat pack (QFP) and other packaging technology. In a known technique for forming a ball grid array, individual balls of solder are pre-formed in a separate process, arranged according to the design of an associated component, positioned relative to the component, and then transferred to the surface of the component, which may have been pre-coated with a low temperature solder paste or flux. Such ball attachment techniques are often complex and present difficult size uniformity, quality uniformity, and other quality control problems. For example, such techniques often do not adequately control ball height or cannot form balls of appropriate height for particular applications. Moreover, these techniques do not provide the combination of speed, reliability, flexibility, and productivity that is increasingly required. Furthermore, the deficiencies of such techniques are amplified as pin counts increase and pitches become finer in an effort to increase chip density without sacrificing performance. As a result, previous techniques for coupling components to electronic devices have been inadequate for many applications.
SUMMARY OF THE INVENTION
According to the present invention, the disadvantages and problems associated with coupling integrated circuit components to electronic devices have been substantially reduced or eliminated.
According to one embodiment of the present invention, a system for coupling conductive pellets to a component of an integrated circuit has a substantially planar ribbon that includes a conductive material. A punching apparatus penetrates the ribbon to form the conductive pellets. The punching apparatus also moves relative to the component to couple the conductive pellets to the component.
The system and method of the present invention provide a number of important technical advantages. As pin counts, chip densities, and performance requirements continue to increase in an intensive effort to increase productivity and reduce costs, an important technical advantage of the present invention includes providing a system and method that forms conductive pellets and couples the conductive pellets to a component in a single operation performed at a single location. The punching technique of the present invention increases speed, productivity, and efficiency to reduce manufacturing costs, without sacrificing precision and reliability. Another important technical advantage of the present invention is that the spatial arrangement of the conductive pellets on the component may be precisely specified and modified according to the arrangement of the punches on the punching apparatus, providing flexibility that is lacking in previous techniques.
Another important technical advantage of the present invention is that the ribbon may have any suitable shape and thickness, and may include any conductive material suitable for coupling a component to an electronic device, such that conductive pellets of any type may be formed from the ribbon according to particular needs. Furthermore, the conductive pellets may be coupled to the component whether or not any flux or solder paste has been previously applied to the surface of the component. Moreover, the system and method of the present invention are compatible with current equipment and processing flows. Other important technical advantages are apparent to one skilled in the art from the following figures, description and claims.
The basic process varies slightly depending upon the solder composition. Dependent upon the solder, the solder form may not be completely melted during reflow. A eutectic solder or flux may be placed on the substrate over the contact areas. If the solder plate is eutectic solder then a layer of flux is placed on each contact area to clean the oxidation of the contact areas. Viscosity of the flux is important when a flux is used. High viscosity flux will hold th solder form over a contact area during reflow. A solder flux with a 325-500 mesh size may be used.
After the solder forms are punched out onto the substrate contact areas, the substrate and forms are heated to cause the solder to reflow. The substrate and solder forms are heated in the range of about 150 degrees C. to about 225 degrees C. Time of reflow is between about 3½ minutes and 5½ minutes.
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patent: 4985107 (1991-01-01), Conroy et al.
patent: 5135817 (1992-08-01), Shimogori et al.
patent: 5767003 (1998-06-01), Noguchi
patent: 5824373 (1998-10-01), Biller et al.
patent: 5968589 (1999-10-01), Murakami
Cheng Johnny
Chou Jack
Hsu Joyce
Honeycutt Gary C.
Navarro Arthur I.
Smith Sean
Telecky Fred
Texas Instruments Incorporated
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