Non leadframe clamping for matrix leadless leadframe package...

Details Non leadframe clamping for matrix leadless leadframe package... Non leadframe clamping for matrix leadless leadframe package...

2003-02-27

2004-02-10

Hail, III, Joseph J. (Department: 3723)

Metal working

Method of mechanical manufacture

Electrical device making

C029S841000, C029S855000, C029S858000

Reexamination Certificate

active

06687983

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to integrated circuits. More specifically, the invention relates to packaging integrated circuits.
BACKGROUND OF THE INVENTION
An integrated circuit (IC) package encapsulates an IC chip (die) in a protective casing and may also provide power and signal distribution between the IC chip and an external printed circuit board (PCB). An IC package may use a metal lead frame to provide electrical paths for that distribution.
To facilitate discussion,
FIG. 1
is a top view of a lead frame panel
100
and attached dice that may be used in the prior art. The lead frame may comprise leads
108
, die attach pads
112
, ties
116
for supporting the die attach pads
112
, and a skirt
120
for supporting the plurality of leads
108
and ties
116
. The lead frame panel
100
may be etched or stamped from a thin sheet of metal. IC chips (dice)
124
may be mounted to the die attach pads
112
by an adhesive epoxy. Wire bonds
128
, typically of fine gold wire, may then be added to electrically connect the IC chips
124
to the leads
108
. Each IC chip
124
may then be encapsulated with part of the leads
108
and the die attach pad
112
in a protective casing, which may be produced by installing a preformed plastic or ceramic housing around each IC chip or by dispensing and molding a layer of encapsulation material over all IC chips
124
.
FIG. 2
is a cross-sectional view of part of the lead frame panel
100
and IC chips
124
. A tape
136
may be placed across the bottom of the lead frame panel
100
and a mold
132
,
133
,
134
may be placed around the lead frame panel
100
. In this example, the mold is clamped on to the tape
136
. In other examples, the mold may be clamped on to both the tape layer
136
and part of the lead frame panel
100
. An encapsulation material
140
is provided to fill the mold, encapsulating the IC chips
124
, the wire bonds
128
, and part of the lead frame panel
100
. The tape
136
and the clamping by the mold
132
,
133
,
134
prevents the encapsulation material
140
from passing through the lead frame panel
100
. Once the encapsulation material
140
is hardened, the mold
132
,
133
,
134
and tape
136
may be removed. The encapsulation material
140
may be cut to singulate the IC chips
124
and leads
108
.
The current heavy clamping of the tape or lead frame and tape to prevent leakage may tear the tape, which could cause leakage, or may result in uneven clamping, which may cause increased flashing. The tearing of the tape may also make removal of the tape more difficult.
It would be desirable to provide a method of preventing leakage, tearing of the tape, and flashing.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a variety of techniques is provided for providing encapsulated dice. Generally, a plurality of dice is connected to a first side of a frame. Tape is attached to a second side of the frame. The dice, frame, and tape are placed completely in a mold cavity. A cover is placed over the mold cavity.
Another embodiment of the invention provides a mold for encapsulating dice attached to a first side of a lead frame with a tape layer covering a second side of the lead frame to form a lead frame assembly. The mold comprises a bottom portion with a cavity large enough to contain the entire lead frame assembly and a cover for covering the mold cavity.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.


REFERENCES:
patent: 5866953 (1999-02-01), Akram et al.
patent: 6104089 (2000-08-01), Akram
patent: 6303981 (2001-10-01), Moden
patent: 6315936 (2001-11-01), Black et al.
patent: 6372526 (2002-04-01), Bailey et al.
patent: 6506625 (2003-01-01), Moden

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