Method of manufacturing a semiconductor device with a pair of radiating terminals and a plurality of lead terminals formed from a single lead frame

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device wherein a pair of radiating terminals and a plurality of lead terminals are formed from a single lead frame.

2. Description of the Related Art

Conventionally, semiconductor devices such as an LSI (Large Scale Integrated Circuit) and a transistor are utilized in various electronic apparatus.

In such apparatus as just mentioned, a pellet comprising a semiconductor circuit is encapsulated in a resin member, and a plurality of lead terminals each formed from an elongated conductive plate are provided on the opposite sides of the resin member. Since those lead terminals are connected to connection pads of the pellet in the inside of the resin member, if the semiconductor device is mounted on a circuit board and the lead terminals are connected to signal lines, then various signals can be inputted to and outputted from the pellet.

While such semiconductor devices are utilized to various applications, for example, a semiconductor device for use with a portable telephone set consumes a large amount of power, and consequently, a pellet of the semiconductor device generates a large amount of heat. Therefore, the generated heat of the pellet must be radiated efficiently.

A conventional example of a semiconductor device which solves the subject just described is described below with reference to FIG.

1

.

In integrated circuit device

1

which is a semiconductor device shown as an example here, a pellet of an integrated circuit formed from a semiconductor circuit is mounted on a radiating plate in the form of an island (not shown), and a pair of radiating terminals

2

having a comparatively large width are provided on the opposite left and right sides of the radiating plate.

A plurality of lead terminals

3

having a comparatively small width are arranged at positions forwardly and rearwardly of and adjacent to radiating terminals

2

. Lead terminals

3

are connected to connection pads of the pellet by bonding wires (not shown).

Since the pellet, the radiating plate, the bonding wires, inner portions of radiating terminals

2

and inner portions of lead terminals

3

are encapsulated in resin member

4

, outer portions

5

and

6

of terminals

2

and

3

are provided projectingly on the left and right side faces of resin member

4

.

Outer portions

5

and

6

of terminals

2

and

3

are bent downwardly, and each of radiating terminals

2

has a hole

7

in the form of a slit formed at the bent portion thereof.

When integrated circuit device

1

having such a construction as described above is to be mounted onto an upper surface of a circuit board, the plurality of lead terminals

3

of integrated circuit device

1

are connected to a plurality of signal lines of the circuit board by solder, and the pair of radiating terminals

2

are connected to conductor patterns such as grounding lines of the circuit board.

Thus, the pellet can input and output various information signals to and from the signal lines of the circuit board, and when the pellet generates heat, the heat is radiated from radiating terminals

2

.

A method of manufacturing integrated circuit device

1

having such a construction as described above is described briefly below with reference to

FIGS. 2 and 3

.

First, lead frame

11

is formed by etching a thin metal plate as seen in FIG.

2

. On this lead frame

11

, a plurality of frame patterns

12

of integrated circuit devices

1

are arranged in rows and columns, and radiating plate

13

is positioned at the center of one frame pattern

12

.

A pair of radiating terminals

2

having a comparatively large width are provided on the opposite left and right sides of radiating plate

13

. A plurality of lead terminals

3

having a comparatively small width are arranged on the opposite front and rear sides, which are upper and lower sides in

FIG. 2

, of radiating terminals

2

.

Intermediate portions of terminals

2

and

3

are connected to each other by a plurality of tie bars

14

. Outer end portions of terminals

2

and

3

are connected to outer frame portion

16

of frame pattern

12

by suspending pins

15

.

Inner portions

17

of lead terminals

3

are formed such that they are directed radially toward the center of radiating plate

13

. Inner portions

18

of radiating terminals

2

are formed integrally with radiating plate

13

.

Holes

7

each in the form of a slit are formed at portions of outer portions

5

of radiating terminals

2

at which radiating terminals

2

are to be bent later.

A pellet comprising a semiconductor circuit is placed onto an upper face of radiating plate

13

of lead frame

11

formed in such a manner as described above, and a plurality of connection pads of the pellet and the plurality of lead terminals

3

are individually connected to each other with bonding wires (not shown).

Lead frame

11

on which the pellet and the bonding wires are mounted integrally in this manner is placed into a cavity of a set of mutually removable metal molds such that it is held at outer portions

5

and

6

of radiating terminals

2

and

3

thereof by and between the metal molds, and in this state, molten resin is filled into the cavity of the metal molds and is then left so as to be solidified to form resin member

4

.

Then, as shown in

FIG. 3

, tie bars

14

and suspending pins

15

of lead frame

11

which are exposed to the outside from resin member

4

are cut away by punches

19

to

21

so that outer portions

5

and

6

of radiating terminals

2

and lead terminals

3

are separated from each other, and outer portions

5

and

6

are bent downwardly, thereby completing integrated circuit device

1

.

When outer portions

5

and

6

of terminals

2

and

3

are bent in this manner, although radiating terminals

2

generally have a comparatively large width, since holes

7

are formed at the bent portions of radiating terminals

2

, radiating terminals

2

can be bent readily similarly to lead terminals

3

having a comparatively small width.

However, since radiating terminals

2

and lead terminals

3

have different widths, punches

19

to

20

for cutting away tie bars

14

and suspending pins

15

cannot be arranged in an equal pitch.

Where punches

19

and

20

cannot be arranged in an equal pitch, operations for setting punches

19

and

20

to a press machine (not shown) are cumbersome, and also the universality of thus set punches

19

and

20

is low.

Further, in order to cut away suspending pins

15

of lead terminals

3

having a comparatively small width and suspending pins

15

of radiating terminals

2

having a comparatively large width, punches

20

having a comparatively small width and punches

21

having a comparatively large width are required. In other words, since a plurality of kinds of punches

20

and

21

having different widths are required, the productivity of integrated circuit device

1

is deteriorated thereby.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of manufacturing a semiconductor device which is high in productivity and a lead frame which contributes to improvement in productivity of a semiconductor device.

In a conventional method of manufacturing a semiconductor device to which the present invention is applied, a lead frame is formed first.

In the lead frame, a single radiating plate and a plurality of lead terminals of a comparatively small width are connected integrally to each other by tie bars and suspending pins. The single radiating plate has a pair of radiating terminals of a comparatively large width formed projectingly on the opposite sides thereof, and the plurality of lead terminals of a comparatively small width are arranged at positions adjacent to the radiating terminals.

A pellet comprising a semiconductor circuit having a plurality of connection pads provided on an upper surface thereof is placed onto an upper surface of the radiating plate of the lead frame formed in such a configuration as described above. The plurality of connection pads of the pellet and the plurality of lead terminals of the lead frame are connected individually to each other with bonding wires.

The lead frame on which the pellet and the bonding wires are mounted integrally is placed into a cavity of a set of mutually removable metal molds, and the metal molds are closed integrally such that outer portions of the radiating terminals and the lead terminals are held by the metal molds.

Molten resin is filled into the cavity of the metal molds. The filled resin is left so as to be solidified to form a resin member in which the pellet, the radiating plate, the bonding wires, inner portions of the radiating terminals and inner portions of the lead terminals are encapsulated.

The tie bars and the suspending pins of the lead frame exposed to the outside from the resin member are cut away to separate the outer portions of the radiating terminals and the lead terminals individually from each other. The outer portions of the lead terminals and the lead terminals extending outwardly from the resin member are bent downwardly.

According to the present invention in such a method of manufacturing a semiconductor device as described above, when the lead frame is formed, the radiating terminals and the plurality of lead terminals are connected to each other at portions thereof to be bent later at the tie bars and at least one hole which has an equal inner width and an equal arrangement pitch as those of gaps between the plurality of lead terminals and whose opposite sides are connected to each other by one of the tie bars is formed at the portion of each of the radiating terminals that is to be bent.

When the tie bars of the lead frame exposed to the outside from the resin member are cut away, the plurality of tie bars positioned at the gaps between the lead terminals and the holes of the radiating terminals are cut away with an equal width and at an equal pitch.

Then, when the outer portions of the radiating terminals and the plurality of lead terminals are bent, the radiating terminals are bent at the positions of the holes.

Accordingly, with the method of manufacturing a semiconductor device of the present invention, the holes are formed in the radiating terminals having a comparatively large width of lead frame at the portion to be bent, and the opposite sides of each of the holes are connected to each other by one of the tie bars. Since the radiating terminals and the plurality of lead terminals are connected to each other by the tie bars and the plurality of tie bars having an equal inner width and an equal arrangement pitch to those of the tie bars, the tie bars are cut away by a plurality of punches arranged in an equal pitch and having an equal width.

Since the plurality of punches for cutting away the plurality of tie bars can be formed with an equal width and can be arranged at an equal pitch, operations for setting the punches in position into a press machine are simple, and also the universality of the punches thus set is good.

It is to be noted that, in the present invention, the direction in which the pellet is mounted with respect to the radiating plate is referred to as upward direction while a direction perpendicular to the direction is referred to as sideward direction. However, such directions are used conveniently in order to simplify description and do not restrict any direction when the device is manufactured or used actually.

Further, the radiating plate in the present invention signifies a member on which a pellet is mounted and which contributes to radiation of heat from the pellet, and allows an island made of a metal.

In the method of manufacturing a semiconductor device of the present invention, when the lead frame is formed, outer end portions of the radiating terminals and the plurality of lead terminals may be connected to an outer frame portion of the lead frame by a plurality of suspending pins having an equal inner width and an equal arrangement pitch, and, when the tie bars and the suspending pins of the lead frame exposed to the outside from the resin member are cut away, the plurality of suspending pins which interconnect the outer end portions of the radiating terminals and the plurality of lead terminals and the outer frame portion may be cut away with equal width and in equal pitch.

In this instance, since radiating terminals having a comparatively large width and the lead terminals of a comparatively small width of lead frame are connected to the outer frame portion of the lead frame by a plurality of suspending pins having an equal inner width and an equal arrangement pitch, the suspending pins are cut away by a plurality of punches arranged in an equal pitch and having an equal width.

Since the plurality of punches for cutting away the plurality of suspending pins can be formed with an equal width and can be arranged in an equal pitch, operations for setting the punches in position into a press machine are simple and also the universality of the punches thus set is good.

A conventional lead frame to which the resent invention is applied includes a substantially rectangular radiating plate, a pair of radiating terminals of a comparatively large width provided projectingly on the opposite sides of the radiating plate, a plurality of lead terminals of a comparatively small width arranged at positions adjacent to the radiating terminals, an outer frame portion positioned on the outer side of outer end portions of the radiating terminals and the plurality of lead terminals, a plurality of suspending pins for connecting the outer end portions of the radiating terminals and the plurality of lead terminals individually to the outer frame portion, and a plurality of tie bars for interconnecting intermediate portions of the radiating terminals and the plurality of lead terminals.

In the present invention in such a lead frame as described above,

each of the radiating terminals has at least one hole formed therein such that the hole has an equal width and an equal arrangement pitch as those of gaps between the plurality of lead terminals and the opposite sides of the hole are connected to each other by one of the tie bars, and the plurality of tie bars which interconnect the intermediate portions of the radiating terminals and the plurality of lead terminals have an equal overall length and an equal arrangement pitch to those of the tie bars of the holes of the radiating terminals.

Accordingly, with the lead frame of the present invention, the holes are formed in the radiating terminals having a comparatively large width at the portions to be bent of, and the opposite sides of each of the holes are connected to each other by one of the tie bars. Since the radiating terminals and the plurality of lead terminals are connected to each other by the tie bars and the plurality of tie bars having an equal inner width and an equal arrangement pitch to those of the tie bars, the tie bars are cut away by a plurality of punches arranged in an equal pitch and having an equal width.

Since the plurality of punches for cutting away the plurality of tie bars can be formed with an equal width and can be arranged at an equal pitch, operations for setting the punches in position into a press machine are simple, and also the universality of the punches thus set is good.

The lead frame of the present invention may be constructed such that the outer end portions of the radiating terminals and the plurality of lead terminals are connected to the outer frame portion of the lead frame by a plurality of suspending pins which have an equal inner width and an equal arrangement pitch.

In this instance, since radiating terminals having a comparatively large width and the lead terminals of a comparatively small width of lead frame are connected to the outer frame portion of the lead frame by a plurality of suspending pins having an equal inner width and an equal arrangement pitch, the suspending pins are cut away by a plurality of punches arranged in an equal pitch and having an equal width.

Since the plurality of punches for cutting away the plurality of suspending pins can be formed with an equal width and can be arranged in an equal pitch, operations for setting the punches in position into a press machine are simple and also the universality of the punches thus set is good.

The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view showing an appearance of a semiconductor device of a conventional example;

FIG. 2

is a plan view showing a lead frame of a conventional example;

FIG. 3

is a plan view showing a condition wherein tie bars and suspending pins of a lead frame are cut away;

FIG. 4

is a plan view showing a lead frame of an embodiment of the present invention;

FIG. 5

is a plan view showing a condition wherein tie bars and suspending pins of the lead frame are cut away;

FIG. 6

is a plan view showing a condition after the tie bars and the suspending pins of the lead frame are cut away; and

FIG. 7

is a perspective view showing an appearance of a completed semiconductor device.

FIG. 8

is a flowchart showing a method of manufacturing a semiconductor device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is described with reference to

FIGS. 4

to

7

. It is to be noted that those elements of the present embodiment which are common to those of the conventional example described hereinabove are denoted by same terms and detailed description of them is omitted here.

First, also in integrated circuit device

31

which is a semiconductor device of the present embodiment, a pair of radiating terminals

32

having a comparatively large width are provided projectingly on the opposite left and right sides of a radiating plate on which a pellet is mounted as shown in

FIG. 7

similarly as in integrated circuit device

1

described hereinabove.

A plurality of lead terminals

33

having a comparatively small width are disposed at positions forwardly and rearwardly of and adjacent to radiating terminals

32

, and outer portions

35

and

36

of terminals

32

and

33

provided in and projecting from resin member

34

are bent downwardly.

However, in integrated circuit device

31

of the present embodiment, different from integrated circuit device

1

described hereinabove, two holes

37

having a comparatively small width are formed at a bent portion of each of radiating terminals

32

. Holes

37

of radiating terminals

32

have an inner width equal to that of the gaps between the plurality of lead terminals

33

and have an arrangement pitch equal to that of the gaps.

Also when integrated circuit device

31

of the present embodiment having such a construction as described above is mounted onto an upper surface of a circuit board, the plurality of lead terminals

33

of integrated circuit device

31

are connected to a plurality of signal lines of the circuit board by solder and the pair of radiating terminals

32

are connected to conductor patterns such as grounding lines or like lines of the circuit board.

Consequently, the pellet can input and output various information signals to and from the signal lines of the circuit board, and heat generated by the pellet can be radiated from radiating terminals

32

.

Here, a method of manufacturing such integrated circuit device

31

as described above is described briefly below with reference to the drawings.

First, lead frame

41

is formed by etching a thin metal plate as seen in FIG.

4

.

Also with this lead frame

41

, a plurality of frame patterns

42

of integrated circuit devices

31

are provided in rows and columns, and radiating plate

43

is positioned at the center of each one frame pattern

42

.

A pair of radiating terminals

32

having a comparatively large width are provided projectingly on the opposite left and right sides of radiating plate

43

. A plurality of lead terminals

33

having a comparatively small width are arranged on the opposite front and rear sides of radiating terminals

32

, which are upper and lower sides in FIG.

4

.

Portions of terminals

32

and

33

to be bent are connected to each other by a plurality of tie bars

44

. Outer end portions of terminals

32

and

33

are connected to outer frame portion

46

of frame pattern

42

by suspending pins

45

.

Inner portions

47

of lead terminals

33

are formed such that they are directed radially toward the center of radiating plate

43

. Inner portions

48

of radiating terminals

32

are formed integrally with radiating plate

43

.

Two holes

37

are formed at a portion of outer portion

35

of each of radiating terminals

32

at which radiating terminal

32

is to be bent. However, since the opposite front and rear sides of each of holes

37

which are the upper and lower sides in

FIG. 4

are connected by one of tie bars

44

, the two holes

37

at present point of time are formed as four holes.

Since holes

37

of radiating terminals

32

have an equal inner width and have an equal arrangement pitch as those of the gaps between the plurality of lead terminals

33

as described above, those tie bars

44

which interconnect the opposite sides of holes

37

have an equal overall length and an equal arrangement pitch as those of tie bars

44

which interconnect terminals

32

and

33

.

Further, while the plurality of lead terminals

33

having a comparatively small width are individually connected to outer frame portion

46

of frame pattern

42

by a plurality of suspending pins

45

having a comparatively small width, each of radiating terminals

32

having a comparatively large width is connected to three suspending pins

45

having a comparatively small width. Those suspending pins

45

have an equal inner width and have an equal arrangement pitch.

A pellet comprising a semiconductor circuit is placed onto an upper surface of radiating plate

43

of lead frame

41

formed in such a manner as described above, and a plurality of connection pads of the pellet and the plurality of lead terminals

33

are individually connected to each other with bonding wires (not shown).

Lead frame

41

on which the pellet and the bonding wires are mounted integrally in this manner is placed into a cavity of a set of mutually removable metal molds such that it is held at outer portions

35

and

36

of terminals

32

and

33

by the between the metal molds, and in this condition, molten resin is filled into the cavity of the metal molds and is then left so as to be solidified to form resin member

34

.

Then, as seen in

FIGS. 5 and 6

, tie bars

44

and suspending pins

45

of lead frame

41

which are exposed outwardly from resin member

34

are cut away and outer portions

35

and

36

of terminals

32

and

33

are separated from each other. Then, outer portions

35

and

36

are bent downwardly as seen in

FIG. 7

, thereby completing integrated circuit device

31

.

With integrated circuit device

31

of the present embodiment, when outer portions

35

and

36

of terminals

32

and

33

are bent, although radiating terminals

32

have a generally large width, since they have holes

37

at portions to be bent thereof, they can be bent readily similarly to lead terminals

33

having a comparatively small width.

Besides, even if radiating terminals

32

and lead terminals

33

have different widths from each other, since tie bars

44

and suspending pins

45

have an equal width and are arranged in an equal pitch, punches

51

and

52

for cutting away them can be arranged in an equal pitch.

Consequently, an operation of setting punches

51

and

52

in position into a press machine (not shown) is simple, and also the universality of punches

51

and

52

thus set is high.

Further, lead terminals

33

having a comparatively small width and radiating terminals

32

having a comparatively large width are connected to outer frame portion

46

of lead frame

41

by suspending pins

45

having an equal comparatively small width. Accordingly, for punches

52

for cutting away suspending pins

45

, a single kind of punches can be used, and integrated circuit device

31

can be manufactured in a high productivity.

While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

Number	Name	Date
5231375	Sanders et al.	Jul 1993
5406260	Cummings et al.	Apr 1995
5675321	McBride	Oct 1997
5703752	Woo	Dec 1997
5877937	Shibata et al.	Mar 1999

Number	Date	Country
62-198144	Sep 1987	JP
63-207161	Aug 1988	JP
9401843	Jan 1994	WO
9626510	Aug 1996	WO
9629638	Sep 1996	WO

Method of manufacturing a semiconductor device with a pair of radiating terminals and a plurality of lead terminals formed from a single lead frame

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

Parent Case Info

US Referenced Citations (5)

Foreign Referenced Citations (5)