Method of making a semiconductor chip package

Details Method of making a semiconductor chip package Method of making a semiconductor chip package

1997-08-04

2001-05-15

Potter, Roy (Department: 2822)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S108000

Reexamination Certificate

active

06232213

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to semiconductor chip packages and, more particularly, to a molded semiconductor chip package having external electrode bumps connected to discrete conductive leads that are in electrical contact with the bond pads on the chip.
BACKGROUND OF THE INVENTION
In response to the demand for semiconductor chip packages having high lead counts and small footprints, ball grid array (BGA), “flip chip” and, more recently, “chip scale” packages have been developed. These packages are surface mounted to an external printed circuit board using an array of solder balls or similar electrode bumps, instead of metal leads. A BGA package utilizes a printed circuit board type substrate instead of a lead frame. In a typical BGA package, the semiconductor chip is mounted to the top surface of a substrate. The chip is wire bonded to electrical traces in the substrate. The chip is then overmolded with an encapsulating material. Solder balls are bonded to the electrical traces in the bottom surface of the substrate. The solder balls serve as the external electrodes for surface mounting on a printed circuit board.
Flip chip packages are similar to BGA packages, except that the solder balls are attached directly to the bond pads or electrical traces formed in the surface of the chip resulting in a more compact package. Due to the absence of an encapsulating material, flip chip packages are quite fragile and require careful assembly and handling techniques. Chip scale packages are being developed to combine the durability of the BGA packages and the small size of the flip chip packages. In a chip scale package, solder balls are attached to electrical traces in the surface of the chip or directly to the bond pads through openings in the encapsulating material. The electrical traces connect the solder balls, which form external electrodes bumps, to the bond pads in the chip. The chip scale package need only be slightly larger then the bare chip because the electrode bumps are formed on the surface of the chip.
It is desirable that the new smaller semiconductor chip packages be adapted for use in standard formats developed for larger chips. However, for both the flip chip and chip scale packages, in which the electrode bumps are attached directly to contacts on the surface of the chip, the electrode bump array must be reconfigured each time the chip is made smaller. Hence, the corresponding contacts on the printed circuit board to which the package is ultimately assembled (the chip “footprint”), must also be reconfigured. In addition, there remains a need for a semiconductor chip package that combines the small size of chip scale packages with the durability and economies of conventional lead frame assemblies and encapsulating techniques currently used to form molded plastic packages.
SUMMARY OF THE INVENTION
It is one object of the present invention to combine the small size of chip scale type packages with the durability and economies of conventional lead frame assemblies and encapsulating techniques.
It is another object of the invention to utilize an array of bump electrodes configured independent of the size of the semiconductor chip so that the package is compatible for use with standard formats developed for larger chips.
These and other objects and advantages are achieved by a semiconductor chip package that includes discrete conductive leads in electrical contact with bond pads on a semiconductor chip. This chip assembly is encapsulated within an encapsulating material such as a thermosetting epoxy resin. Electrode bumps are formed through openings in the encapsulating material to contact the conductive leads. The electrode bumps protrude from the encapsulating material for connection to an external circuit.
In one preferred embodiment of the invention, the package comprises a semiconductor chip having bond pads disposed thereon, the bond pads being accessible from an upper surface of the chip. Conductive leads, which extend over and are attached to the upper surface of the chip, are electrically connected to the bond pads. An encapsulating material covers at least a portion of the upper surface of the chip, the bond pads, and the leads. If desired, the entire assembly may be fully encapsulated. Alternatively, the conductive leads may extend out from the encapsulating material. Openings are formed in the encapsulating material to expose portions of the leads. Electrodes are formed through the openings in the encapsulating material and bonded to the exposed portions of the leads. These electrodes, typically solder balls, can then be surface mounted to a printed circuit board in the same way BGA and chip scale packages are mounted.
The conductive leads may be part of a conventional lead frame and the assembly encapsulated using equipment and techniques currently used to form molded plastic packages. The ends of the leads may extend out of the encapsulating material with or without forming to facilitate testing and burn-in. After testing, the leads may be severed flush with the encapsulating material or left extending from the package. Alternatively, the leads may be severed prior to encapsulation and the assembly fully encapsulated.
As noted, the semiconductor chip package of the present invention can be assembled using conventional molded plastic packaging techniques, equipment and materials. Further, because the electrode bumps are not connected directly to the bond pads or electrical traces in the semiconductor chip, the size of the package and the configuration of the electrode bump array can remain the same even as the chip is made smaller, thus allowing the package to be constructed to a standard format.


REFERENCES:
patent: 5136366 (1992-08-01), Worp et al.
patent: 5139969 (1992-08-01), Mori
patent: 5239198 (1993-08-01), Lin et al.
patent: 5289346 (1994-02-01), Carey et al.
patent: 5293072 (1994-03-01), Tsuji
patent: 5341564 (1994-08-01), Arhavain et al.
patent: 5355283 (1994-10-01), Marrs et al.
patent: 5362679 (1994-11-01), Wakefield
patent: 5397921 (1995-03-01), Karnezos
patent: 5420460 (1995-05-01), Massingill
patent: 5442231 (1995-08-01), Miyamoto et al.
patent: 5442233 (1995-08-01), Anjoh et al.
patent: 5519251 (1996-05-01), Sato et al.
patent: 5804468 (1998-09-01), Tsuji et al.
patent: 4-277636 (1992-10-01), None
“Moto gets ‘Slice’ with packaging”, Feb. 28, 1994, Electronic Engineering Times, pp. ?, 100.
“Mitsubishi Scales Down IC Packages”, Electronic Engineering Times, Aug. 22, 1994, p. 13.
TA 8.2: A 34 ns 256 Mb DRAM with Boosted Sense-Ground Scheme, 1994 IEEE International Solid-State Circuits Conference Digest of Technical Papers, pp. 140-141.
“Scandia Shrinks Size of BGA Packages”, May 16, 1994, Electronic Engineering Times, p. 57.
Shinko Technology Update, Dec. 12, 1994, p. 141.

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