Severing by tearing or breaking – Methods – With preliminary weakening
Reexamination Certificate
2001-05-30
2002-10-22
Watts, Douglas D. (Department: 3724)
Severing by tearing or breaking
Methods
With preliminary weakening
Reexamination Certificate
active
06467666
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of producing a semiconductor package by breaking a multilayer wafer for leadless chip carrier packages on a package basis.
A multilayer wafer for the above application has customarily been formed with aligned V-shaped grooves in opposite major surfaces thereof. A cleaving force is exerted on the wafer in order to break it on a package basis. Specifically, when the cleaving force acts on the wafer, which has a crystal structure, the direction in which the wafer breaks is not constant. The grooves formed in the wafer serve to maintain the above direction constant.
However, the grooves are formed in the wafer by half-cutting instead of full-cutting. This brings about a problem that if the grooves are not accurately aligned, then breaking equipment is likely to fail to break the wafer along a line connecting the grooves. Specifically, it is likely that the wafer breaks from one groove, but misses the other groove. As a result, a burr appears on the resulting chip and prevents the chip from being accurately mounted.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 61-253830 and 11-224865, Japanese Patent Publication No. 6-11071, and Japanese Patents 2,748,355 and 2,780,618.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of producing a semiconductor device capable of braking a multilayer wafer for leadless chip carrier packages on a package basis with a minimum of burrs.
A method of producing a semiconductor device of the present invention is applicable to a multilayer wafer for leadless chip carrier packages and breaks it on a package basis. The method begins with a step of forming a generally V-shaped groove in one major surfaces of the wafer in the direction of thickness of the wafer. A weak, cleaving portion is formed in the other major surface of the wafer in alignment with the groove. A cleaving force is exerted on the wafer to thereby form a break in the cleaving portion, so that the wafer is caused to break from the groove toward the cleaving portion in the direction of thickness of the wafer. The cleaving portion may be replaced with a strong, non-cleaving portion, in which case the break is formed in the interface between the non-cleaving portion and the wafer due to a difference in cleaving force.
REFERENCES:
patent: 5609284 (1997-03-01), Kondratenko
patent: 5678744 (1997-10-01), Nakamura
patent: 5740953 (1998-04-01), Smith et al.
patent: 5786266 (1998-07-01), Boruta
patent: 61-253830 (1986-11-01), None
patent: 6-11071 (1994-02-01), None
patent: 2748355 (1998-02-01), None
patent: 2780618 (1998-05-01), None
patent: 11-224865 (1999-08-01), None
Ichikawa Seiji
Nagano Nobuo
Ogihara Fumie
Sato Taku
Tokue Tatsuo
Hayes & Soloway PC
NEC Corporation
Watts Douglas D.
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