Reinforced sealing technique for an integrated circuit package

Details Reinforced sealing technique for an integrated circuit package Reinforced sealing technique for an integrated circuit package

1994-07-29

2001-07-24

Ball, Michael W. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S092000, C156S291000, C156S292000, C156S293000, C174S050510

Reexamination Certificate

active

06264778

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates to packaging techniques for integrated circuits and, more particularly, to techniques for sealing an integrated-circuit package.
2. Prior Art
A hermetically-sealed package, or package assembly for an integrated circuit typically includes a base in which is formed a cavity for the integrated-circuit die. The base of the package is formed of a ceramic or a metallic material. A lid of ceramic or metallic material is sealed to the base with an appropriate layer of sealing material, such as glass, solder, or epoxy. Sometimes an intermediate, thin sealing ring is positioned between the base and the lid so that two layers of sealing material are used, one on each side of the sealing ring. Currently, all of the sealing techniques used in packaging of integrated circuits rely upon the adhesion strength of the layer of sealing material. Because of the differences in the temperature coefficients of expansion (TCE) of the various materials used in a package, the adhesion of the sealing material fails and the lids of the packages peel away from their bases. This occurs particularly when a package is subjected to pressure-pot testing or to thermal-cycle testing, where the shear forces cause the sealing materials to fail at the margins between the sealing materials and the package elements.
With variations in temperature, the various components of a package, as well as the sealing layers, expand or contract at different rates so that shear forces are generated at the interfaces between the different elements and the sealing materials. The shear strengths of the sealing materials, such as glass, solder, or epoxy are relatively weak so that failures occur at the margin of the sealing material near the package elements. Typically, an epoxy material fails with a shear pressure of 1 to 5 kpsi. The materials of the package elements such as the base or lid are much stronger under shear loads. For example a metal has a failure shear strength of 10-30 kpsi.
One solution to the problem of lids peeling from packages is to attempt to match the TCE's of the various materials of the package assembly. This is difficult to accomplish and has the disadvantage that more expensive materials often must be used.
The need has arisen for an improved integrated circuit packaging technique which enhances and reinforces currently-used packaging technique by increasing the adhesion strength of adhesive or bonding material between the lid and the base of an integrated-circuit package.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved packaging technique for integrated circuits, which techniques increases the performance of the adhesion or bonding layer between the lid and the base of an integrated package.
In accordance with this and other objects of the invention, the invention provides for inserting one or more reinforcement pins between the lid and base of an integrated-circuit package. This invention is applicable to a number of different package types, such as pin-grid-array (PGA), side-brazed, and epoxy-sealed packages of various types. The reinforcement pins are used to reinforce a sealing layer between the lid and the base, particularly when shear forces are exerted on the boundaries between the sealing layer and the lid or base of the package. The length of the reinforcement pins are optional. Shorter pins do not extend through the lid or base. Longer pins can extend through the lid or base and their ends are mechanically secured to the lid or base and sealed with solder, glass, or epoxy material.
The invention provides a package structure and a method of packaging an integrated circuit. An integrated-circuit die is mounted within a cavity formed in a base of a package. A lid is positioned over the integrated-circuit die and the base and lid are sealed with a sealing layer positioned between the base and the lid.
The invention contemplates using at least one reinforcement pin, which extends through the sealing layer and at least partially through the base and at least partially through the lid. The reinforcement pin provides reinforcement for the sealing layer between the base and the lid so that the package can resist shear forces tending to rupture the sealing layer between the lid and the base of the package. The invention is useful with packages which use an intermediate sealing ring between the lid and the base. The reinforcement pin extends through this type of ring and through sealing layers formed adjacent to the top and bottom surfaces of this ring.
A pin extends at least partially through an undersize aperture in the base and at least partially through an undersize aperture in the lid to secure the reinforcement pin to the base and the lid. The pin can extend through either or both of the lid and the base of a package. The extending end or ends of a reinforcement pin are fixed to a lid or base, for example by being stamped, pressed, or punched and sealed with a number of materials, such as solder, glass, or epoxy.


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The McGraw-Hill Dictionary of Scientific and Technical Terms, 3rd. Ed., McGraw-Hill Book Company, New York, (1984) p. 1563.

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