JP2002110867A - Semiconductor device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power semiconductor device having excellent insulation and heat dissipation properties and suitable for thinning, and its manufacturing method. SOLUTION: The semiconductor device comprises a semiconductor element comprising a plurality of power semiconductor elements 102 and control semiconductor elements 103, a lead frame 101 comprising a part mounted with the semiconductor elements and lead parts 101A for taking out electric signals from the semiconductor elements and connected electrically with the semiconductor elements, a mold resin seal 106 covering the semiconductor elements and the mounting face of the lead frame, heat dissipation fins 107, and an insulating layer 108 of thermosetting resin formed on the surface of the heat dissipation fins for mounting the lead frame. The insulating layer extends over the part of the lead frame for mounting the semiconductor element and has thermal conductivity higher than that of the mold resin seal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a power semiconductor device used for a resin-sealed type intelligent power module such as an inverter.

[0002]

2. Description of the Related Art Conventionally, a power semiconductor device such as an inverter generates a lot of heat and is usually used with a heat radiating device such as a heat radiating fin. FIG. 4 is a sectional view and a plan view of a conventional power semiconductor device. A power semiconductor device such as an inverter includes, for example, a semiconductor element including a plurality of power semiconductor elements 2 and a control semiconductor element 3 formed on a silicon semiconductor substrate. The lead frame 1 made of a metal such as copper or an alloy thereof is
A mounting part on which a semiconductor element is mounted and a plurality of external terminals 1A
And a lead portion composed of A plurality of power semiconductor elements 2 and control semiconductor elements 3
Has been implemented. Each power semiconductor element 2 is bonded to the lead frame 1 by an Al wire 4 via a connection electrode (not shown) formed on the surface. The control semiconductor element 3 is bonded to the lead frame 1 by an Au wire 5 via a connection electrode (not shown) formed on the surface. Lead frame 1
Mounting part, power semiconductor element 2, control semiconductor element 3,
The Al wire 4 and the Au wire 5 are resin-sealed with a mold resin sealing body 6 made of a material such as epoxy resin or silicone resin. In order to perform resin sealing, the power semiconductor element 2 and the control semiconductor element 3 are mounted, and the lead frame 1 in which these electrical connections are made with the wires 4 and 5 is inserted into a resin mold. Resin sealing is performed by, for example, The resin sealing body 6 has a thermal conductivity of 2 W / m ·
The lead portion of the lead frame 1 is exposed from the resin sealing body 6. The external terminal 1A constituting the lead portion is bent upward at a right angle to be mounted on a circuit board after being led out of the resin sealing body 6.

[0003]

In this type of power semiconductor device, since it is necessary to suppress a rise in temperature due to heat generated during operation of the semiconductor device, a radiation fin is attached to the bottom surface thereof. In this conventional example, silicon grease 9 is applied to the surface of the radiation fin 7 on which the lead frame is mounted, and the lead frame 1 is fixed thereon by screwing.
Screws (not shown) fix the lead frame 1 through mounting holes 6A formed in the resin sealing body 6. External terminal 1A formed on the lead portion of lead frame 1
Are radiating fins 7 in order to secure the insulation characteristics of the semiconductor device.
Are separated by about 2.5 to 3 mm. Therefore, the lead frame 1 is formed before the semiconductor element is mounted, and is configured such that the external terminal 1 </ b> A is led out from substantially the center of the side surface of the resin sealing body 6. The distance D between the external terminal 1A and the radiation fin 7 (about 2.5 to 3 mm in this example) is
The creepage distance of the resin sealing body between them is almost equal to the creepage distance, and this distance is set according to safety conditions such as an electric handling method depending on use conditions. As described above, there is a factor that hinders the thinning of a semiconductor device in terms of safety standards. Also,
The silicon grease 8 is interposed for stably arranging the lead frame 1 on the heat radiation fins 7. However, since the silicon grease 8 has lower thermal conductivity together with the resin sealing body 6 than metal,
Its presence is a factor that hinders the heat dissipation of the semiconductor device. The present invention has been made under such circumstances, and provides a power semiconductor device having high insulation properties, excellent heat dissipation properties, and suitable for thinning, and a method for manufacturing the same.

[0004]

According to the present invention, there is provided a power semiconductor device having a semiconductor element mounted thereon and a resin-sealed lead frame mounted on a heat radiation fin. Extends over the portion of the lead frame on which the semiconductor element is mounted, and has an insulating layer having a higher thermal conductivity than the resin sealing body. That is, the semiconductor device of the present invention has a semiconductor element having a plurality of power semiconductor elements and a control semiconductor element, a mounting part on which the semiconductor element is mounted, and a lead part for extracting an electric signal from the semiconductor element, And a lead frame electrically connected to the semiconductor element, a molded resin sealing body covering a surface of the semiconductor element and the lead frame on which the semiconductor element is mounted, a radiation fin, and the lead of the radiation fin An insulating layer made of a thermosetting resin formed on a surface on which the frame is mounted, wherein the insulating layer extends beyond a mounting portion on which the semiconductor element of the lead frame formed thereon is mounted. It is characterized in that it is large in size and has higher thermal conductivity than the molded resin sealing body.

[0005] A heat radiating plate may be interposed between the insulating layer and the heat radiating fins. Silicon grease may be interposed between the heat radiating plate and the heat radiating fins. When the withstand voltage of the semiconductor device is 600 V or less, the distance from the end of the mounting portion of the lead frame where the semiconductor element is mounted to the outer periphery of the insulating layer may be at least 3.5 mm. . The thermal conductivity of the insulating layer may be 3 W / m · K or more. The thickness of the insulating layer is 0.15 to 0.30.
mm. A method of manufacturing a semiconductor device according to the present invention includes a step of mounting a semiconductor element having a plurality of power semiconductor elements and a control semiconductor element on the mounting part of a lead frame having a mounting part and a lead part; Forming a molding resin sealing body so as to cover the surface of the frame on which the semiconductor element is mounted; and forming a heat-radiating fin on the surface on which the lead frame is mounted, made of a thermosetting resin, and having heat conductivity of the molding resin sealing. Forming an insulating layer having a size larger than the stopper and extending beyond the mounting portion of the lead frame;
A step of pressing a lead frame having the molded resin sealing body formed on the insulating layer, followed by heating to bond the lead frame to the insulating layer.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view and a plan view of a power semiconductor device. A power semiconductor device such as an inverter used in this embodiment includes, for example, a semiconductor element including a plurality of power semiconductor elements 102 and a control semiconductor element 103 formed on a silicon semiconductor substrate. Further, a lead frame 1 made of a metal such as copper or an alloy thereof is used.
Reference numeral 01 denotes a mounting portion on which a semiconductor element is mounted and a lead portion including a plurality of external terminals 101A.
A plurality of power semiconductor elements 102 and control semiconductor elements 103 are mounted on this mounting portion. Each power semiconductor element 102 is bonded to the lead frame 101 by an Al wire 104 via a connection electrode (not shown) formed on the surface thereof. Control semiconductor element 1
03 is a connection electrode (not shown) formed on the surface
Lead wire 101 by Au wire 105 through
Bonding.

Each connection electrode is electrically connected to an internal circuit of the semiconductor device. A mounting portion of a lead frame 101, a power semiconductor element 102, a control semiconductor element 103,
The Al wire 104 and the Au wire 105 are resin-sealed with a mold resin sealing body 106 made of a material such as epoxy resin or silicone resin. To perform resin sealing, the power semiconductor element 102 and the control semiconductor element 103 are mounted, and the lead frame 101 in which these electrical connections are made by wires 104 and 105 is inserted into a resin mold.
Resin sealing is performed by a transfer molding method or the like. The resin sealing body 106 has a thickness of about 2.5 to 3 mm,
The lead portion of the lead frame 101 is a resin sealing body 106
It is exposed from the bottom surface. The external terminal 101A constituting the lead portion is bent upward at a right angle so as to be mounted on a circuit board after being led out of the resin sealing body 106, while keeping a little horizontal.

FIG. 3 shows an example of a resin mold for forming the resin sealing body. A sealing resin such as an epoxy resin previously formed into a tablet is heated and melted with a jar. The melted resin is filled into a cavity formed by combining an upper mold and a lower mold through a runner and a gate. Semiconductor elements 102 and 103 electrically connected to the cavities by Al wires 104 and Au wires 105
Is mounted. After the cavity is filled with the resin, the resin is cured for a certain period of time, and then the mold is opened to obtain a resin-sealed semiconductor device. Since it is necessary to suppress a rise in temperature due to heat generated during operation of the semiconductor device, the power semiconductor device is used with a radiation fin attached to a bottom surface thereof. In this embodiment, the insulating layer 108 is formed on the surface of the heat radiation fin 107 such as Al on which the lead frame is mounted, and the lead frame 101 is fixed thereon by crimping.

As shown in FIG. 4, the external terminals 1A formed on the lead portions of the conventional lead frame 1 are 2.5 to 2.5 inches apart from the heat radiation fins 7 in order to secure the insulation characteristics of the semiconductor device.
They are separated by about 3 mm. Therefore, the lead frame 1 is formed before the semiconductor element is mounted, and is configured such that the external terminal 1 </ b> A is led out from substantially the center of the side surface of the resin sealing body 6. The distance D (about 2.5 to 3 mm in this conventional example) between the external terminal 1A and the radiation fins 7 is substantially equal to the creepage distance of the resin sealing body therebetween. It conforms to the ones stipulated by safety standards such as laws. Such safety standards must be sufficiently satisfied in this embodiment.

Therefore, in the present invention, an insulating layer 108 which is larger than the contact portion (mounting portion) of the lead frame 101 excluding the external terminal 101A is formed on the mounting surface of the heat radiation fin,
The lead frame 101 is disposed thereon such that the insulating layer 108 extends at the end of the contact portion of the lead frame. Then, the lead frame 101
Is a distance for securing insulation between the external terminal 101A and the radiation fin 107, and is a distance D of the conventional example.
Must be greater than or equal to. Therefore, the distance d from the end of this joint portion of the lead frame 101 to the outer periphery of the insulating layer 108 is at least 2.5 mm,
Preferably at least 3.5 mm is required. At that time, the thickness of the insulating layer needs to be about 0.15 to 0.30 mm. If it is too thin, insulation cannot be maintained, and if it is too thick, thinning cannot be achieved as expected.

As described above, although the insulation is conventionally secured in the vertical direction, in the present embodiment, the insulation is secured in the horizontal direction. Can be made thinner nearby. The insulating layer 108 is made of a thermosetting resin, printed on the mounting surface of the radiating fins 107, mounted with the lead frame 101, and then heat-pressed to attach and insulate the lead frame to the radiating fins. The formation of the layers can be performed simultaneously. Since there is no need for screwing, mounting holes for the semiconductor device become unnecessary, and as a result, downsizing becomes possible. The insulating layer uses a material having a thermal conductivity of 3 W / m · K or more.
Therefore, the molded resin sealing body is 0.3 W / m · K
A material having a low thermal conductivity can be used, and it is not necessary to add a large amount of filler such as alumina. Although the insulating layer uses an epoxy resin or the like, it is not necessary to use the same material as the resin sealing body.

Next, a second embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view and a plan view of the power semiconductor device. A power semiconductor device such as an inverter used in this embodiment includes, for example, a plurality of power semiconductor elements 202 and a control semiconductor element 203 formed on a silicon semiconductor substrate.
And a semiconductor element comprising: Further, a lead frame 201 made of a metal such as copper or an alloy thereof is used.
Is composed of a mounting portion on which a semiconductor element is mounted and a lead portion including a plurality of external terminals 201A. A plurality of power semiconductor elements 202 and control semiconductor elements 203 are mounted on this mounting portion. Each power semiconductor element 202 is connected to a lead frame 2 by an Al wire 204 via a connection electrode (not shown) formed on the surface thereof.
01 is bonded. Control semiconductor element 203
Is bonded to the lead frame 201 by an Au wire 205 via a connection electrode (not shown) formed on the surface thereof.

Each connection electrode is electrically connected to an internal circuit of the semiconductor element. A mounting portion of a lead frame 201, a power semiconductor element 202, a control semiconductor element 203,
The Al wire 204 and the Au wire 205 are resin-sealed with a mold resin sealing body 206 made of epoxy resin, silicone resin, or the like. In order to perform resin sealing, a power semiconductor element 202 and a control semiconductor element 203 are mounted, and a lead frame 201 in which these electrical connections are made by wires 204 and 205 is inserted into a resin mold.
Resin sealing is performed by a transfer molding method or the like. The resin sealing body 206 has a thickness of about 2.5 to 3 mm,
The lead portion of the lead frame 201 is
It is exposed from the bottom surface. The external terminal 201A constituting the lead portion is bent upward at a right angle so as to be mounted on a circuit board after being led out from the resin sealing body 206, while maintaining a little horizontal state.

Since it is necessary to suppress a rise in temperature due to heat generated during operation of the semiconductor device, the power semiconductor device is used with a radiation fin attached to the bottom thereof. In this embodiment, a heat radiating plate 210 made of Al or the like is formed on a heat radiating fin 207 made of Al or the like, an insulating layer 208 is formed on a surface of the heat radiating fin 207 on which a lead frame is mounted, and the lead frame 201 is crimped thereon. It is fixed. As described above, the external terminal 1A formed at the lead portion of the conventional lead frame 1 shown in FIG. 4 is separated from the heat radiation fin 7 by about 2.5 to 3.5 mm in order to secure the insulation characteristics of the semiconductor device. Have been. Therefore, the lead frame 1 is formed before the semiconductor element is mounted, and is configured such that the external terminal 1 </ b> A is led out from substantially the center of the side surface of the resin sealing body 6. Distance D between external terminal 1A and radiation fin 7
Is approximately equal to the creepage distance of the resin sealing body therebetween, and this distance is set according to the safety conditions such as the electric handling method depending on the use conditions. Such safety standards are
This embodiment must also be fully satisfied.

Therefore, in this embodiment, an insulating layer 208 is formed on the mounting surface of the heat radiating plate 210, which is larger than the contact portion (mounting portion) except for the external terminals 201A of the lead frame 201, and the lead frame 201 is formed thereon. It is characterized in that the insulating layer 208 is arranged so as to extend the end of the contact portion of the lead frame. And lead frame 2
The distance d from the end of this section to the outer periphery of the insulating layer 208 is a distance for securing insulation between the external terminal 201A and the heat sink 210, and is the distance D of the conventional example.
Must be greater than or equal to. Therefore, the distance d from the end of this joint portion of the lead frame 201 to the outer periphery of the insulating layer 208 is at least 2.5 mm,
Preferably at least 3.5 mm is required. At that time, the thickness of the insulating layer needs to be about 0.15 to 0.30 mm. If it is too thin, insulation cannot be maintained, and if it is too thick, thinning cannot be achieved as expected.

As described above, although the insulation is conventionally secured in the vertical direction, in the present embodiment, the insulation in the horizontal direction is secured, and as a result, the thickness of the resin sealing body 206 is reduced by half compared to the conventional case. Can be made thinner nearby. The insulating layer 208 is made of a thermosetting resin, printed on the mounting surface of the heat radiating plate 210, mounted with the lead frame 201, and then heat-pressed to attach the lead frame to the heat radiating plate and insulate it. The formation of the layers can be performed simultaneously. The insulating layer uses a material having a thermal conductivity of 3 W / m · K or more. Therefore, a material having a low thermal conductivity of about 0.3 W / m · K can be used for the molded resin sealing body, and it is not necessary to insert a large amount of filler such as alumina. Although the insulating layer uses an epoxy resin or the like, it is not necessary to use the same material as the resin sealing body.

The heat radiating plate 210 is made of silicon grease 209.
Is mounted on the radiation fin 207 via the
A mounting hole 210 </ b> A for screwing into the heat radiating plate 210 is formed on the heat radiating plate 210, and this is mounted on the heat radiating fin 207. In this embodiment, since the configuration is made as described above, in addition to the same effects as those of the first embodiment, the shape of the heat radiation fins can be freely selected, and the user can arrange the semiconductor device at the time of assembly. The degree of freedom is improved.

[0018]

As described above, according to the present invention, it is possible to obtain a thin semiconductor device which secures an insulating distance between an external terminal and a heat radiating fin and has excellent heat radiating properties as compared with the prior art. In addition, since a mounting hole for the radiation fin can be eliminated, the size of the semiconductor device can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view and a plan view of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a sectional view and a plan view of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a resin mold for performing resin sealing performed in the present invention.

FIG. 4 is a cross-sectional view and a plan view of a conventional semiconductor device.

[Explanation of symbols]

1, 101, 201 ... lead frame, 1A, 10
1A, 201A ... external terminal, 2, 102, 202
..Power semiconductor elements, 3, 103, 203 ... control semiconductor elements, 4, 104, 201 ... Al wires,
5, 105, 205 ... Au wire, 6, 106, 2
06: resin sealing body, 6A, 210A: mounting hole, 7, 107, 207: radiation fin, 9, 20
9 ... silicon grease, 108, 208 ...
Insulating layer, 210: heat sink.

Claims (7)

[Claims] A semiconductor element having a plurality of power semiconductor elements and a control semiconductor element; a mounting part on which the semiconductor element is mounted; and a lead part for extracting an electric signal from the semiconductor element, and the semiconductor element. A lead frame electrically connected to the semiconductor chip, a molded resin sealing body for covering the semiconductor element and a surface of the lead frame on which the semiconductor element is mounted, a radiator fin, and the lead frame of the radiator fin. And an insulating layer formed of a thermosetting resin, the insulating layer having a size extending beyond a mounting portion on which the semiconductor element of the lead frame formed thereon is mounted. A semiconductor device having thermal conductivity higher than that of the molded resin sealing body. 2. The semiconductor device according to claim 1, wherein a heat radiating plate is interposed between said insulating layer and said heat radiating fin. 3. The semiconductor device according to claim 2, wherein silicon grease is interposed between said heat radiating plate and said heat radiating fins. 4. When the withstand voltage of the semiconductor device is 600 V or less, a distance from an end of a mounting portion of the lead frame on which the semiconductor element is mounted to an outer periphery of the insulating layer is at least 3.5 mm. 4. The semiconductor device according to claim 1, wherein: 5. The thermal conductivity of the insulating layer is 3 W / m · K.
The semiconductor device according to claim 1, wherein: 6. The insulating layer has a thickness of 0.15 to 0.3.
The semiconductor device according to claim 1, wherein the distance is 0 mm. 7. A step of mounting a semiconductor element having a plurality of power semiconductor elements and a control semiconductor element on the mounting part of a lead frame having a mounting part and a lead part, and the semiconductor element and the semiconductor element of the lead frame. A step of forming a molded resin sealing body so as to cover the surface on which is to be mounted, and a heat-radiating fin made of a thermosetting resin on the surface on which the lead frame is mounted, and having higher thermal conductivity than the molding resin sealed body, And a step of forming an insulating layer having a size extending beyond the mounting portion of the lead frame; and crimping the lead frame on which the molded resin sealing body is formed on the insulating layer, and then heating the lead frame. Bonding the lead frame to the insulating layer.