Cutting – Particular nature of work or product – Contact pin of electrical component
Reexamination Certificate
1998-11-06
2002-01-29
Rachuba, M. (Department: 3724)
Cutting
Particular nature of work or product
Contact pin of electrical component
C083S098000, C083S100000, C029S827000
Reexamination Certificate
active
06341549
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an apparatus for manufacturing semiconductor device packages, and more particularly to an apparatus having trim punches with an air inflow route for trimming gate scrap from a lead frame on which encapsulated package bodies are formed.
2. Description of the Related Arts
In a manufacturing process of semiconductor device packages, a semiconductor chip is attached and electrically connected to a lead frame and sealed in an encapsulant such as an EMC (Epoxy Molding Compound). Encapsulation protects the chip from external environmental stresses and improves the reliability of the chip's electrical operation. During an encapsulation process, the lead frame having multiple semiconductor chips mounted thereon is engaged between upper and lower molds which form cavities in the shape of package bodies, and the encapsulant is injected through gates into the cavities to fill the cavities. The encapsulant is cured, and the lead frame with attached package bodies is separated from the molds. After removal from the molds, scraps of the encapsulant still remain on the package bodies at gates which provide an injection route for the encapsulant. The scraps of encapsulant at the gate of the package body, that is, the gate scraps, are trimmed or removed together with the dambars. This step is referred to as a “trimming step.” Usually, trimming of the gate scrap is just prior to trimming of the dambar.
A typical apparatus for trimming the gate scraps comprises an upper die having multiple trim punches and a lower die having multiple outlets for discharging trimmed scraps. The lead frame including multiple packages is engaged between and secured to the upper and the lower die so that the gate scraps are aligned with the outlets in the lower die. Lowering the trim punches of the upper die trims off the gate scraps and discharges the trimmed gate scrap through the outlets of the lower die. A vacuum suction device removes the trimmed gate scrap from under the outlets.
However, during trimming, the trim punches trim block air flow through the outlets. Accordingly, the vacuum suction device may be unable to remove the trimmed gate scrap from the outlet. Further, the numerous successive trimming steps produce friction and static electricity so that electrostatic forces attract the gate scraps to the dies. Accordingly, the trimmed gate scrap may remain attached to the trim punch or the lower die. The attached gate scrap residues can obstruct the trimming of the next lead frame, clog the trimming apparatus, and/or the crack of the semiconductor device package.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to effectively discharge or remove the trimmed gate scrap by blowing the air into the outlet during the trimming process.
Another object of the present invention is to prevent clogging of the trimming apparatus and/or cracking of semiconductor device packages due to the gate scrap residues.
The foregoing and other objects are achieved by an apparatus having trim punches with air flow routes. In order to trim and remove the gate scrap from an encapsulated package body, the trimming apparatus of the present invention includes a scrap trim die disposed at a lower surface of a lead frame on which the package bodies are formed, and a scrap punch die disposed at an upper surface of the lead frame.
The scrap trim die includes an outlet which corresponds to the gate scrap and serves as a route for discharging the gate scrap after trimming, and first projections which hold the lead frame during trimming of the gate scrap. The scrap punch die includes a trim punch which corresponds to and trims the gate scrap, and second projections which hold the lead frame during trimming of the gate scrap.
The trimming apparatus according to the present invention has an air inflow route on the inside of the trim punch. Since the air successively flows through the air inflow route of the trim punch to the outlet during trimming, the trimmed gate scrap is easily discharged and removed from the outlet. Preferably, the air inflow route may be a through hole formed in and on the trim punch.
The trimming apparatus of the invention preferably includes the scrap trim die having a plurality of the outlets and the scrap punch die having a plurality of the trim punches so that the gate scraps of a plurality of the packages are simultaneously trimmed and removed.
The scrap trim and a transfer rail for transferring the lead frame are on a lower die and the scrap punch die is on an upper die of the trimming apparatus. The lower die further comprises a dambar trim die for trimming dambars of the lead frame and the upper die further comprises a dambar punch die which corresponds to the dambar trim die.
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Heid David W.
Rachuba M.
Samsung Electronic Co. Ltd.
Skjerven Morrill & MacPherson LLP
Tran Kim Ngoc
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