JPH07176664A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PURPOSE:To enhance the heat dissipation properties by mounting a semiconductor element on a metal pattern formed on one main surface of a board having high thermal conductivity, fixing a heat plate onto a metal layer formed on the other main surface, and molding them such that the outer terminals are exposed. CONSTITUTION:The semiconductor device comprises a board 11 made of an electrical insulating material having relatively high thermal conductivity, a metal pattern body 12 disposed on one main surface of the board 11 with outer terminal part 12B extending from the board 11, and a semiconductor element 16 mounted on the metal pattern body 12. The semiconductor device further comprises a metal layer 14 formed on the other main surface of the substrate 11, a heat plate 20 fixed thereon, and a molding body 19 covering the board 11 mounting the semiconductor element 16 and the heat plate 20 while exposing the outer terminal part 12B. For example, a copper circuit pattern body 12 is disposed on the mounting face of a ceramic board 11 and a copper layer 14 is disposed on the surface opposite to the mounting surface. The power element pellet 16 is then mounted on the head 12a of the copper circuit pattern body 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a power power transistor, a power IC, etc., and a method of manufacturing the same.

[0002]

2. Description of the Related Art A resin-sealed semiconductor device equipped with a so-called power element such as a power transistor or a power IC prevents an electrical short circuit between power elements or between a power element and an external heat sink. For this reason, the power device has a configuration in which the envelope (a peripheral member outside the semiconductor device) other than the external electrode terminals (leads) and the power element are electrically insulated.
A conventional semiconductor device of such an insulation type is shown in FIG.
(A), FIG. 4 (B), and FIG. 5 (A) to FIG. 5 (C).

FIG. 4A is a plan view showing an example of a conventional semiconductor device with its interior seen through.
4B is a sectional view taken along the line 4B-4B in FIG. Reference numeral 41 in the figure indicates a lead. The lead 41 has a bed 41a that is a large area, and the semiconductor element 42 is mounted on the bed 41a. The semiconductor element 42 is fixed on the bed 41 a with solder 413 and is electrically connected to the leads 41. The lead 41 is formed of a lead frame. An electrode pad (not shown) is provided on the upper surface of the semiconductor element 42, and the electrode pad is electrically connected to the lead 41 by a bonding wire 44.

The lead 41 on which the semiconductor element 42 is mounted is
In order to electrically insulate the semiconductor element 42 from the outside, it is covered with an insulating material such as an epoxy resin. In this case, part of the lead is the mold body 4 made of an insulating material.
It is exposed from No. 5, and this exposed portion is used as an outer lead. Further, on the lead 41 on the surface opposite to the surface on which the semiconductor element 42 is mounted, a heat dissipation plate 46 made of a metal such as Al or Cu is arranged via an insulating material. The mold body 45 can be formed by placing the leads 41 on which the semiconductor elements 42 are mounted and the heat radiating plate 46 in a molding die at regular intervals and performing transfer molding using the insulating material.

FIG. 5 (A) is a plan view showing another example of a conventional semiconductor device, FIG. 5 (B) is a side view thereof, and FIG. 5 (C) is 5C- of FIG. 5 (A). It is sectional drawing which follows the 5C line. In the semiconductor device shown in FIG. 5, the same members as those of the semiconductor device shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In the figure, 51 indicates a ceramic substrate. A circuit pattern 52 made of copper is formed on the mounting surface of the ceramic substrate 51, and on the surface opposite to the mounting surface,
A copper layer 60 is formed. This is the so-called DBC
(Direct Bonding Copper) substrate. The circuit pattern 52 has a bed 52a which is a large area, and the semiconductor element 42 is mounted on the bed 52a.

A heat dissipation plate 46 is provided on the copper layer 60 via solder 53. A resin case 54 is adhered to the peripheral edge of the heat dissipation plate 46 via an adhesive layer 55. In the resin case 54, a gel agent 5 such as silicone resin
6 is filled, and the semiconductor element 42 and the DBC substrate are respectively covered with the gel agent 56. A casting layer 57 made of a thermosetting resin is formed on the surface of the gel agent 56. Further, on the casting layer 57,
A terminal holder 58 is installed. A pin-shaped electrode terminal 59 is attached to the terminal holder 58. One end of the terminal electrode 59 is electrically connected to the circuit pattern 52 so as to penetrate the casting layer 57 and the gel agent 56. The other end of the terminal electrode 59 projects from the terminal holder 58 and is used as an outer lead.

In such a resin-encapsulated semiconductor device equipped with a power element, it is important to quickly dissipate the heat generated from the power element to the outside of the device, that is, to improve heat dissipation. This makes it possible to take advantage of the characteristics of the power element and also ensure the reliability after long-term use. Therefore, in the envelope of this device, it is very important to reduce the thermal resistance value from the power element to the surface of the envelope and improve the heat dissipation.

[0008]

However, in the conventional example shown in FIG. 4, the thermal resistance value is relatively large. This is because the thermal conductivity K of the insulating material used for the molded body is much smaller than that of ceramic or the like.

Further, the thickness A of the insulating material between the lead 41 and the heat dissipation plate 46 cannot be made thin to the extent that it exhibits a thermal conductivity equivalent to that of ceramics due to the restriction of the manufacturing technique. For example, using the encapsulating resin (K = 0.04 W / cm · ° C.) that has the best heat conduction property on the market at present, FIG.
In the case of manufacturing the semiconductor device shown in Fig. 5, in order to obtain the heat conduction characteristics equivalent to those of the alumina ceramic (K = 0.2 W / cm · ° C) having a thickness of 0.6 mm used in the semiconductor device shown in Fig. 5. Must have a thickness A of 0.12 mm or less.

However, the manufacturing limit of the thickness A is 0.5 mm, and it is impossible at present to reduce the thickness A to 0.12 mm or less. Moreover, since the average particle size of the resin used for sealing is about 0.3 mm, if the thickness A is set to be smaller than 0.5 mm, voids will inevitably occur, and the quality and reliability of the equipment will be improved. Is reduced.
As described above, the conventional semiconductor device shown in FIG. 4 is inferior in heat dissipation.

The other conventional example shown in FIG. 5 is superior to the conventional example shown in FIG. 4 in terms of heat dissipation, but the number of main constituent members and the number of steps required for assembling them are large.
As a result, the device is complicated and expensive. For example, the number of constituent members of the semiconductor device shown in FIG. 4 is five (lead frame, semiconductor element, heat sink, bonding wire, sealing resin), while the main constituent members of the semiconductor device shown in FIG. Is 9 (DBC substrate, semiconductor element, heat sink, bonding wire, adhesive for case adhesion, resin case, gel agent, casting agent, terminal holder (including terminal electrode)). Further, the number of assembling steps of the semiconductor device shown in FIG. 4 is three, that is, die bonding, wire bonding, and transfer molding, whereas the number of assembling steps of the semiconductor device shown in FIG. Die bonding, wire bonding, heat sink and terminal holder installation (reflo
w), resin case mounting (joining), resin filling A (p
oting) and resin filling B (casting).

The present invention has been made in view of the above points, and provides a semiconductor device which is excellent in heat dissipation, lightweight and simple, and a manufacturing method capable of efficiently obtaining such a semiconductor device. The purpose is to do.

[0013]

The present invention is directed to a substrate made of an electrically insulating material having a relatively high thermal conductivity, and an external terminal portion provided on one main surface of the substrate and extending from the substrate. A metal pattern body having: a semiconductor element mounted on the metal pattern body; a metal layer provided on the other main surface of the substrate; a heat dissipation plate attached to the metal layer; There is provided a semiconductor device comprising: the substrate on which the semiconductor element is mounted and a mold body covering the heat dissipation plate so that the terminal portion is exposed.

Further, according to the present invention, a metal pattern body having an external terminal portion is formed on one main surface and a metal layer is formed on the other main surface, which is made of an electrically insulating material having a relatively high thermal conductivity. A step of mounting a semiconductor element on the metal pattern body of a board; a step of attaching a heat dissipation plate on the metal layer; and a step of mounting the semiconductor element on the board and the heat dissipation so that the external terminal portions are exposed. And a step of coating the plate with an insulating material.

Here, as an electrically insulating material having a relatively high thermal conductivity which constitutes the substrate, alumina (Al ₂ O
₃ ) and ceramics such as aluminum nitride (AlN _x ) can be used. Further, as the material of the metal pattern body, copper, copper alloy or the like can be used. Also,
Copper, a copper alloy, etc. can be used as a material of a metal layer. A DBC substrate can be used as the substrate having the metal pattern body and the metal layer. Further, as the material of the heat sink, aluminum, copper, iron or the like can be used. Further, as the material of the mold body, epoxy resin, silicone resin or the like can be used.

As a method of mounting the semiconductor element on the metal pattern body of the substrate, ordinary die bonding and wire bonding can be mentioned. As a method of attaching the heat sink to the metal layer, reflow using a brazing material such as solder can be used. As a method of coating the substrate and the heat sink with an insulating material, a transfer molding method using a thermosetting resin such as an epoxy resin or a silicone resin can be used. When the substrate and the heat sink are covered with an insulating material, the whole heat sink may be covered, or a part of the heat sink may be exposed to the outside. This is appropriately selected depending on the application of the semiconductor device.

[0017]

In the semiconductor device of the present invention, the heat generated by the semiconductor element is transmitted to the substrate made of a material having a relatively high thermal conductivity through the metal pattern body, and further to the heat sink through the metal layer. , Released from the heat sink to the outside world. Therefore, the heat dissipation of the semiconductor element is improved. Further, since the external terminal portion of the metal pattern body can be used as the external terminal of the semiconductor element, the number of constituent members of the semiconductor device can be reduced. As a result, the weight of the semiconductor device can be reduced.

In the method of manufacturing a semiconductor device of the present invention, the number of constituent members of the semiconductor device is small, so that the manufacturing process is simplified. Therefore, a semiconductor device having excellent heat dissipation can be efficiently manufactured at low cost.

[0019]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a semiconductor device of the present invention, FIG. 1 (A) is a plan view showing the inside as seen from above, and FIG. 1 (B) is FIG. 1 (A). 1B-
It is sectional drawing which follows the 1B line. In the figure, 11 indicates an electrically insulating ceramic substrate having a relatively high thermal conductivity. A copper circuit pattern body 12 is provided on the mounting surface of the ceramic substrate 11. The copper circuit pattern body 12 has a bed 12 a, which is a large area, and an external terminal portion 12 b extending from the ceramic substrate 11. An alloy layer 13 made of an alloy of ceramic and copper is formed between the ceramic substrate 11 and the copper circuit pattern body 12. The alloy layer 13 fixes the copper circuit pattern body 12 to the ceramic substrate 11. Has been done. Furthermore, the ceramic substrate 1
A copper layer 14 is fixed by the alloy layer 13 on the surface opposite to the mounting surface of No. 1 (hereinafter, abbreviated as back surface). This ceramic substrate 11, copper circuit pattern body 12,
And DBC (Direct Bonding Copper)
The substrate 15 is constructed.

On the bed 12a, a power element pellet 1 containing a power transistor, a power IC, etc.
6 has been implemented. Specifically, the pellet 16 is fixed on the bed 12 a by the solder 17 and electrically connected to the copper circuit pattern body 12. As the solder 17, it is preferable to use a high melting point solder such as Pb—Sn—Ag solder. In this embodiment, high melting point solder having a melting point of about 310 ° C. is used. Also, on the surface of the pellet 16,
Electrode pads (not shown) are provided, and the electrode pads and the copper circuit pattern body 12 are electrically connected by a bonding wire 18 such as gold (Au) or aluminum (Al).

A heat radiating plate 20 is attached on the copper layer 14 with solder 21 such as Pb-Sn solder. The heat radiating plate 20 is exposed to the outside and plays a role of releasing the heat generated by the pellets 16 to the outside of the device.

Around the DBC substrate 15, the DBC substrate 15 and the heat sink 20 on which the pellets 16 are mounted so that the external terminal portions 12b of the copper circuit pattern body 12 are exposed.
Is provided with a substantially rectangular parallelepiped mold body 19. The mold body 19 electrically insulates the pellet 16 from the outside world. The external terminal portion 12b exposed from the mold body 19 to the outside is used as an outer lead. In this way, the semiconductor device of the present invention is constructed.

This semiconductor device is assumed to be an inverter circuit device for driving a motor. Six pellets 16 are incorporated in this inverter circuit device. This circuit diagram is shown in FIG. As shown in FIG. 2, one pellet 16 has a base terminal, a collector terminal, and an emitter terminal, and functions as one power element (here, functions as a bipolar transistor).
Inside the pellet 16, two Darlington-connected power transistors (bipolar type), a diode, a resistor, and the like are incorporated, and integrated into a circuit capable of driving a large current, that is, a kind of It is a power IC.

The motor driving inverter circuit shown in FIG. 2 is constructed by using six pellets 16 containing the above-mentioned power element or power IC. The six pellets 16 are mounted in one envelope to form one resin-sealed semiconductor device. Therefore, the outer leads exposed from the mold body 19 are
There are a total of 11 positive power supply terminals (+), negative power supply terminals (-), 6 input terminals BU, BV, BW, BX, BY and BZ, and 3 output terminals U, V and W.
Note that in FIG. 1A, common reference numerals are given in the vicinity of the outer leads in correspondence with the circuit shown in FIG.

Next, a method of manufacturing the semiconductor device shown in FIG. 1 will be described. 3A and 3B are views showing a DBC substrate 15 included in an embodiment of the semiconductor device of the present invention, FIG. 3A is a plan view, and FIG. 3B is a line 3B-3B in FIG. 3A. FIG. As shown in FIG. 3, the DBC substrate 1
5, a tie bar 22 for connecting the external terminal portion 12b is provided near the end of the copper circuit pattern body 12,
It is in the form of a lead frame. By thus forming the copper circuit pattern body 12 in the form of a lead frame, continuous assembly is possible.

First, a DBC substrate 15 provided with a lead frame-shaped copper circuit pattern body 12 as shown in FIG. 3 is prepared. Next, the pellet 16 is fixed onto the bed 12a provided on the copper circuit pattern body 12 using the high melting point solder 17 (die bonding). Then, gold (A
u) or an aluminum (Al) bonding wire 18 is used to electrically connect an electrode pad (not shown) provided on the pellet 16 to the copper circuit pattern body 12 (wire bonding). Next, the metal heat sink 20 is fixed to the back surface of the DBC substrate 15, that is, the copper layer 14 using the high melting point solder 21 (heat sink attachment by reflow). Next, the DBC substrate 15 with the heat dissipation plate 20 attached is set in a molding die (not shown), and resin is poured into the molding die to perform transfer molding, whereby the DBC is formed.
A rectangular parallelepiped mold body 19 is formed around the substrate 15 (molding). Finally, the tie bar 22 connecting the external terminal portions 12b of the copper circuit pattern body 12 is cut and removed. After this cutting, the external terminal portion 12b is molded into a desired shape (outer lead forming). In this way, the semiconductor device of the present invention is manufactured.

According to the above semiconductor device, since the copper circuit pattern body 12 is almost in direct contact with the ceramic substrate 11, the pellet 16 is substantially the copper circuit pattern body 12.
It will be connected to the ceramic substrate 11 only through. Therefore, the heat generated by the pellet 16 is
It is transmitted to the ceramic substrate 11 made of a material having a relatively high thermal conductivity through the copper circuit pattern body 12, further transmitted to the heat dissipation plate 20 via the copper layer 14, and is emitted from the heat dissipation plate 20 to the outside. Therefore, the heat dissipation of the pellet 16 can be improved more than that of the conventional semiconductor device (see FIG. 4) in which the resin is filled under the bed for mounting the pellet. Specifically, the thermal resistance value in the envelope of the conventional semiconductor device is about 4 ° C./W per one power element pellet of 5 mm ² , whereas the thermal resistance value in the envelope of the semiconductor device is Is about 1.5 ° C./W per 5 mm ² power element pellet, which is reduced to less than half.

Further, according to the semiconductor device having the above structure, since the copper circuit pattern body, which is the metal pattern body, is supported by the ceramic substrate, the DBC substrate is stably covered when the molded body is formed by transfer molding. can do. In addition, since the copper circuit pattern body is reliably supported in this way, the thickness of the copper circuit pattern body can be reduced.

Further, in the above semiconductor device, the external terminal portion 12b of the copper circuit pattern body 12 is extended from the ceramic substrate 11, and this external terminal portion 12b is used as the external terminal of the pellet 16. As described above, by using the copper circuit pattern body 12 as the external electrode terminal, the number of constituent members of the semiconductor device can be reduced, and thus the cost of parts can be reduced. further,
Since the number of constituent members of the semiconductor device can be reduced, the number of manufacturing steps of the semiconductor device can be reduced, and thus the manufacturing cost can be reduced. For example, in the conventional semiconductor device shown in FIG. 5, the number of constituent members is large and the cost tends to be high. However, in the above semiconductor device, the number of main constituent members is five.
Individual, namely DBC substrate, pellet, heat sink, wire,
Also, resin may be used, and the number of constituent members can be reduced by four compared with the conventional semiconductor device shown in FIG. Also,
In this embodiment, the number of manufacturing steps is five, that is, die bonding, wire bonding, attachment of a heat sink by reflow, molding, and outer lead forming are sufficient, and one step can be reduced. Therefore, the manufacturing cost can be reduced.

Further, in the above semiconductor device, by forming the copper circuit pattern body 12 in the form of a lead frame, resin molding such as transfer molding can be continuously and collectively performed. Particularly, in the conventional semiconductor device shown in FIG. 5, since it is necessary to perform resin sealing for each product, there is a problem in terms of mass productivity and workability as well. Very effective in terms of sex.

The present invention is not limited to the above embodiment. For example, as the material of the ceramic substrate 11, aluminum nitride (AlN _x ) is used instead of alumina.
Can also be used. Aluminum nitride is currently more expensive than alumina and it is difficult to use a direct bonding method such as the DBC method, but since it has higher thermal conductivity than alumina, it is a preferable material for improving heat dissipation. Is. Further, when using this aluminum nitride, a brazing material containing a Group IV element of the periodic table such as Ti may be used when fixing to the copper circuit pattern body 12. The joining method using this brazing filler metal is a joining method generally called active metal joining.

[0032]

As described above, the semiconductor device of the present invention is provided on a substrate made of an electrically insulating material having a relatively high thermal conductivity and one main surface of the substrate, and extends from the substrate. A metal pattern body having an external terminal portion, a semiconductor element mounted on the metal pattern body, a metal layer provided on the other main surface of the substrate, a heat dissipation plate mounted on the metal layer, and an external terminal Since the semiconductor device is provided with the substrate on which the semiconductor element is mounted and the mold body covering the heat dissipation plate so as to expose the portion, it is possible to provide a lightweight and simple semiconductor device having excellent heat dissipation.

In the semiconductor device of the present invention, a metal pattern having an external terminal portion is formed on one main surface, and a metal layer is formed on the other main surface. Insulate the board on which the semiconductor element is mounted and the heat sink by exposing the external terminals to the step of mounting the semiconductor element on the metal pattern of the board made of material, the step of mounting the heat sink on the metal layer. And the step of coating with a conductive material, the semiconductor device having the above structure can be efficiently obtained.

[Brief description of drawings]

FIG. 1A is a plan view showing an embodiment of a semiconductor device of the present invention, and FIG. 1B is a sectional view taken along line 1B-1B of FIG.

FIG. 2 is a circuit diagram for explaining a circuit of one embodiment of a semiconductor device of the present invention.

3A is a plan view showing a DBC substrate provided with a semiconductor device of the present invention, and FIG. 3B is a sectional view taken along line 2B-2B of FIG.

FIG. 4A is a plan view showing a conventional semiconductor device,
(B) is sectional drawing which follows the 4B-4B line of (A).

FIG. 5A is a plan view showing a conventional semiconductor device,
(B) is a side view of the semiconductor device shown in (A), and (C) is a cross-sectional view taken along line 5C-5C of (A).

[Explanation of symbols]

11 ... Ceramic substrate, 12 ... Copper circuit pattern body, 12
a ... bed, 12b ... external terminal portion, 13 ... alloy layer, 14
... copper layer, 15 ... DBC substrate, 16 ... power element pellet, 17, 21 ... solder, 18 ... bonding wire, 1
9 ... Mold body, 20 ... Heat sink, 22 ... Tie bar.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 23/28 K 8617-4M 23/50 F

Claims (2)

[Claims] 1. A substrate made of an electrically insulating material having a relatively high thermal conductivity, a metal pattern body provided on one main surface of the substrate and having external terminal portions extending from the substrate, A semiconductor element mounted on the metal pattern body, a metal layer provided on the other main surface of the substrate, a heat sink attached on the metal layer, and the external terminal portion exposed. A mold body that covers the substrate on which the semiconductor element is mounted and the heat dissipation plate. 2. A metal of a substrate made of an electrically insulating material having a relatively high thermal conductivity, wherein a metal pattern body having an external terminal portion is formed on one main surface and a metal layer is formed on the other main surface. A step of mounting a semiconductor element on the pattern body, a step of attaching a heat sink to the metal layer, and an insulating property between the board on which the semiconductor element is mounted and the heat sink so that the external terminal portion is exposed. And a step of covering with a material.