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Lead Frame Design for Molded Heat Spreader Plastic Flat Package

IP.com Disclosure Number: IPCOM000116537D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 62K

Publishing Venue

IBM

Related People

Hayashida, S: AUTHOR [+2]

Abstract

Disclosed is a lead frame design for thermally enhanced plastic package which has a heat slug inside the package. By devising a die pad design of a lead frame, a chip crack caused by molding pressure can be eliminated.

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Lead Frame Design for Molded Heat Spreader Plastic Flat Package

      Disclosed is a lead frame design for thermally enhanced plastic
package which has a heat slug inside the package.  By devising a die
pad design of a lead frame, a chip crack caused by molding pressure
can be eliminated.

      Fig. 1 shows the structure of Molded Heat Spreader Plastic Flat
Package.  The heat slug (1) touches a backside of a die paddle (2)
without any adhesive or glue.  The heat slug radiates a heat which is
generated in the semiconductor chip (3).  A mold resin (4)
encapsulates the whole structure, such as chip, lead frame (5) and
the heat slug in a same mold.

      Figs. 2 and 3 show the chip cracking mechanism in the Molded
Heat Spreader Plastic Package.  The mold resin (6) comes from a gate
(7) and fills a cavity (8).  After that, the resin gets pressed.
Since the mold resin has lower viscosity, the mold resin comes into a
interface between die paddle (9) and heat slug (10) during filling.
Then a chip (11) is bent by a transferring pressure.  When the resin
ingress (12) is higher or larger, the chip breaks (13) by the
transferring pressure.

      Fig. 4 shows a die pad design to eliminate the chip crack.  The
die paddle (14) has a half etched slit (15) which is placed to be
surrounding away from the edge of a chip.

      Fig. 5 shows how the slit works for preventing the chip crack.
First slit (16) works to stop the resin ingress.  The second slit
(17) a...