Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1997-05-20
2001-09-25
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S262000
Reexamination Certificate
active
06294745
ABSTRACT:
This application is related to commonly assigned and concurrently filed application Ser. No. 08/518,874, filed, entitled “Apparatus and Method for Vacuum Injection Molding.”
BACKGROUND OF THE INVENTION
The present invention relates generally to soldering of integrated circuits and substrates, and, more specifically, to an improved solder decal and method of forming and using.
Solder processing for standard electronic packaging applications such as integrated circuit chip interconnections routinely use evaporation or electroplating. Both of these processes are costly, and may involve many processing steps. For example, to produce a solder decal by electroplating, a metal seed layer must first be deposited on a decal substrate. Next, this seed layer is patterned to produce the desired layout, after which the plating process produces the solder structures. Finally, the patterning and unplated seed layers must be stripped away. For effective transfer, the seed layer remaining under each solder structure must not metallurgically bond to the solder during reflow. Both of these processes are also typically limited to smaller solder structures such as solder balls having a diameter of about 2-4 mils.
Other requirements such as chip rework, burn-in and test, thermally mismatched packages, and 3-D packaging usually cannot be met with solder interconnection schemes alone. For example, burn-in and test methods usually require sophisticated temporary connectors. Thermally mismatched packages require mechanically flexible connections such as copper or gold-plated pins. The cost of these temporary connectors for burn-in and test as well as substrates with tall gold-plated pins significantly increase the overall package costs.
SUMMARY OF THE INVENTION
A solder decal is produced by a method wherein a decal strip having a plurality of anchor holes is aligned with a mold having a plurality of cells. Liquid solder is injected into the anchor holes and mold cells, and is then allowed to cool to solidify therein. The mold may be separated from the decal strip to form the solder decal containing solder beads each having a stem mechanically joined to the strip at respective ones of the anchor holes. Various forms of the solder decal are used for transferring the solder beads to a substrate or chip, or effecting temporary connections for conducting burn-in and testing, or accommodating thermal mismatch for example.
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Conte Francis L.
International Business Machines - Corporation
Ngo Hung V
Reichard Dean A.
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