JP3142322B2 - Resin-sealed semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device having a built-in transistor, diode and thyristor, and more particularly to a device for high power requiring good thermal characteristics.

[0002]

2. Description of the Related Art A resin-sealed semiconductor device used for high-power switching or motor drive will be described with reference to the cross-sectional view of FIG.
That is, both surfaces of the insulating substrate 3 on which the semiconductor element 2 is mounted are covered with a conductive metal pattern (not shown), and the semiconductor element 1 is mounted on one of the two in a conventional manner.

Further, the heat sink 1 and the insulating substrate 3 are fixed to each other with a solder layer 4 interposed therebetween, and external terminals 5 electrically connected to respective electrodes of the semiconductor element 2 are provided. The stopper layer 6 is covered as shown in FIG. 2 to complete the resin-sealed semiconductor device. When forming this resin sealing layer 6, the heat sink 1
One side is exposed so that its function can be exhibited. The heat radiating plate 1 is a metal plate having a thickness of 3 to 5 mm mainly made of Cu, Al, or the like.
A conductive metal layer is provided on both sides of a ceramic plate such as alumina or aluminum nitride having a thickness of about 0.1 mm.

[0004] The reason why ceramic is used is that it has a relatively good thermal conductivity as an insulator, and the heat sink 1 is soldered and integrated therewith to improve the heat transfer to the heat sink 1. In addition, the semiconductor element 2 is of a conductivity modulation type.
MOSFETs are often used. Such a resin-encapsulated semiconductor device generates a large amount of heat, and the heat radiation plate 1 alone is insufficient in heat radiation.

A silicone resin or the like is usually applied between the heat sink and the resin-sealed semiconductor device in order to maintain good heat conduction.

In such a method of manufacturing a resin-encapsulated semiconductor device, the semiconductor element 2 is mounted on the insulating substrate 3 by soldering or the like, and a thin metal wire (not shown) is provided between the semiconductor element electrode and the insulating substrate 3. For example, a predetermined bondability is maintained and fixed by a thermocompression bonding method.

Normally, the insulating substrate 3 and the heat radiating plate 1 and the insulating substrate 3 and the external terminals 5 are soldered by a reflow method using sheet solder or cream solder 4. In the subsequent resin sealing step, after adhering the resin case to the heat sink 1, a gel resin made of a silicon polymer or the like is injected and thermoset, and then a thermosetting epoxy resin is injected and thermoset. And resin sealing.

As described above, a resin-encapsulated semiconductor device is manufactured through a number of heat treatment steps. However, in a soldering step, the eutectic temperature of a general tin / lead solder is around 180 ° C. Even when the eutectic solder 4 is used, usually 2
A heat treatment step at a temperature of 00 ° C. or higher is required.

Further, while the semiconductor element 2 and the insulating substrate 3 are usually soldered with a melting point of about 250 ° C. or higher, the soldering of the insulating substrate 3 and the heat radiating plate 1 is not performed.
A solder having a eutectic temperature around 180 ° C. is used.

Here, the reason why the solders having different melting points are used is to prevent the semiconductor element from separating or moving from the insulating substrate 3 when the insulating substrate 3 and the heat sink 1 are soldered.

[0011]

In a resin-sealed semiconductor device manufactured by the above soldering process,
When cooled to room temperature after the assembly process, stress remains due to the difference in the coefficient of thermal expansion possessed by each part, and as a result, each part is deformed. The degree depends on the thermal expansion coefficient, hardness, shape, and melting point of the solder used.

In a resin-sealed semiconductor device, the insulating substrate 3
When ceramic is used, the coefficient of thermal expansion is small and it is difficult to deform. Further, the heat radiating plate made of Cu or AL used as the heat radiating plate 1 has a larger coefficient of thermal expansion than the insulating substrate 3 and is easily deformed. Therefore, the heat radiating plate is deformed in the soldering process as shown in FIG.

That is, there is a problem that the central portion of the resin-sealed semiconductor device is lower than both ends and the flatness is deteriorated. For this reason, the flatness of the heat radiating plate 1 is deteriorated, and the contact heat resistance is deteriorated when the heat radiating plate 1 is attached to the heat sink.

In order to improve the contact thermal resistance, a method is conceivable in which the heat sink is warped in advance (see FIG. 3A) in consideration of the amount of warpage in the heat treatment step (soldering of the heat sink and the insulating substrate). . However, in this case, although the contact thermal resistance is improved, the deformation of the insulating substrate 3 still occurs due to the heat treatment process (see FIG. 3B), and the insulating substrate 3 is in a state where the stress remains. When such a resin-encapsulated semiconductor device is attached to a heat sink, when the heat sink (see FIG. 3C) is warped in a mountain shape (see FIGS. 3B and 3A),
The stress applied to the insulating substrate 3 in the screwing step, which is a general means of attachment, increases, causing a defect that the insulating substrate 3 is broken (see FIG. 3D). a) Regarding the warp of the heat sink, a warp of 400 μm or less is allowed for a length of 10 cm according to JIS. Also, in order to reduce the stress due to the difference in thermal expansion coefficient, the use of a solder having a lower melting point than the Pb-Sn solder-based eutectic solder may be considered for the purpose of lowering the temperature of the heat treatment process. It is not preferable in view of easiness and improvement in the amount of warpage associated with the use of solder having a low melting point.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a resin-sealed semiconductor device with less deformation after a heating step.

[0016]

SUMMARY OF THE INVENTION The resin-sealed semiconductor of the present invention.
Body device is a ceramic substrate having conductive metal layers on both sides
And a semiconductor element fixed to one surface of the ceramic substrate
Is electrically connected to the semiconductor element, and the ceramic
External terminals installed on a ceramic substrate, and the ceramic substrate
Exposed one side of the heat sink and the heat sink fixed to the other side
Consisting of a sealing resin layer covering the ceramic substrate
In the semiconductor device, the other surface of the ceramic substrate and
Interposed between the heat sinks, both sides of the ceramic substrate
On the other side and one side of the heat sink via a solder layer respectively
Characterized by having a fixed metal plate.
You. Further, in the resin-sealed semiconductor device of the present invention,
The ceramic substrate is alumina, vaginalized aluminum
Or beryllia.
is there.

Further, an insulating substrate made of one kind selected from the group consisting of alumina, aluminum nitride and beryllia also has the feature of the resin-sealed semiconductor device according to the present invention.

[0018]

In the resin-sealed semiconductor device according to the present invention, a conductive metal layer is provided on both surfaces of an insulating substrate, and a semiconductor element is fixed to one surface thereof. The conductive metal layer on the other surface is made to correspond to the heat sink, and a metal plate is inserted in the middle to fix the three members using a solder layer.

In addition, by sealing the resin layer so that one surface of the heat sink is exposed, and by inserting a metal plate, the characteristics of the resin-encapsulated semiconductor device can be exhibited for a long time to improve reliability. Is what you do.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to FIGS. In the resin-encapsulated semiconductor device clarified in the cross-sectional view of FIG. 4, a conductivity modulation type MOS FET, that is, a semiconductor element 10 and a high-speed freewheeling diode, that is, a semiconductor element 11 are mounted and fixed on an insulating substrate 12.

The insulative substrate 12 is made of a ceramic selected from the group consisting of alumina, aluminum nitride and beryllia, and has a conductive metal layer (not shown) provided on both surfaces thereof. In preparation for soldering with the metal plate 11 and a metal plate 13 described later. The insulating substrate 12 on which the conductive metal layer is formed is a so-called DBC (Direct).
Bond Copper) substrate, that is, a substrate in which cuprous oxide is formed on an insulating substrate can also be used.

A thin metal wire (not shown) is fixed to electrodes formed near the surfaces of the semiconductor elements 10 and 11 mounted and fixed on the insulating substrate 12 by a thermocompression bonding method, for example, an ultrasonic bonding method. The tip is similarly fixed to a metal layer formed on the insulating substrate 12 by, for example, an ultrasonic bonding method.

The metal plate 13 has a thickness of 0.3 mm or more.
1.5 mm, which is equal to the thickness of the insulating substrate 12 and heat sink 1
4 is fixed by a solder layer 15, and the heat sink 14 has a thickness of 2
The main material is Cu of 5 mm to 5 mm. Further, external terminals 16 are mounted on the insulating substrate 12 electrically connected to the electrodes formed on the semiconductor elements 10 and 11 by the thin metal wires.
Various electronic circuits are formed by such electrical connections. The connection states of the semiconductor elements are clarified with reference to FIGS. 10A, 10B, and 10C. In the figure, C represents a collector, E represents an emitter, G represents a gate, and U, V, and W represent terminals.

As is clear from this connection diagram, the semiconductor elements 10 and 11 form various electronic circuits, and are used, for example, for high-power switching or motor driving, and are easy to handle, and are easy to handle. Degree modulation type
Apply MOSFET and fast freewheeling diode.

After the assembly process is completed, the assembly is housed in a resin container (not shown), and then the sealing resin layer 17 is poured into the assembly to form a resin-sealed semiconductor shown in the sectional view of FIG. Device 17 is obtained. At this time, a resin sealing step is performed so that the back surface of the heat sink 14 is exposed, and a small warp is shown in FIG. 5 as x.

The resin-sealed semiconductor device 1 having such a structure
8 is for cooling to room temperature after assembling the semiconductor element.
Since the stress caused by the difference in the coefficient of thermal expansion between the insulating substrate 12 and the radiator plate 14 can be reduced, the warp of the radiator plate 14 can be reduced.

Therefore, when the resin-sealed semiconductor device 18 is mounted on a heat sink (not shown), the contact thermal resistance can be improved and the heat can be radiated well. FIG. 6 shows a change in the amount of warpage of the heat sink 14 of the resin-encapsulated semiconductor device 18. FIG.
The vertical axis represents the amount of warpage x (unit: μm), and the horizontal axis represents the thickness (unit: mm) of the metal plate 13. X shown in FIG.
Is also the amount of warpage. That is, although the degree of improvement in the amount of warpage differs depending on the thickness of the metal plate 13 used, it is apparent that the amount of warpage has been improved as compared with the conventional product.

Further, the resin-encapsulated semiconductor device 18 according to the present invention can disperse the stress applied to the insulating substrate 12 from the outside. The breakdown strength of the insulating substrate 12 with respect to the tightening torque is improved. This state is shown in FIG. In other words, the ordinate shows the insulation breakdown rate and the abscissa shows the thickness (unit: mm) of the metal plate, and it is clear that the improvement is remarkably improved as compared with the conventional structure.

The results are obtained by the experiment shown in FIG. 7. The details are described in detail below. The resin-sealed semiconductor device according to the present invention is mounted on a stainless steel plate 19 through a Piano wire 20 having a diameter of 350 μm. It is installed and fixed at four locations with screws (see FIG. 8). Furthermore, tightening torque is 30kg ・
cm, tighten the screw a on the left side of the paper, and then tighten the screw b on the right side.
Then, AC5Kv was applied for 10 seconds, and the withstand voltage failure rate was measured for each of ten pieces.

The resin-sealed semiconductor device according to the present invention comprises:
As is apparent from the top view of FIG. 9, screws are installed at four locations and fixed to a heat sink (not shown) on which the screws are mounted.

[0031]

As described above, according to the present invention, the heat radiation plate of the resin-encapsulated semiconductor device has less warpage, so that the contact heat resistance when mounting the device on a heat sink or the like can be improved and the heat can be radiated well. Can be.

Further, since the stress applied to the insulating substrate from the outside of the resin-sealed semiconductor device can be dispersed, even if the heat sink is screwed to the heat sink or the like, the insulating substrate can withstand the screw tightening torque even if the heat sink has poor flatness. Can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional resin-encapsulated semiconductor device.

FIG. 2 is an external view of a conventional resin-encapsulated semiconductor device.

FIG. 3 is a diagram showing a problem of a conventional resin-encapsulated semiconductor device. FIG. 3A is a cross-sectional view of a state in which the heat sink is warped in consideration of the amount of warpage in advance. FIG. 3B is a cross-sectional view after the heat sink and the insulating substrate are soldered. FIG. 3c is a cross-sectional view of the heat sink warped in a chevron. FIG. 3D is a cross-sectional view showing a state where a stress is applied to the insulating substrate and the insulating substrate is broken.

FIG. 4 is a sectional view of a resin-sealed semiconductor device according to the present invention.

FIG. 5 is a diagram showing a state in which the amount of warpage of the resin-encapsulated semiconductor device according to the present invention is improved.

FIG. 6 is a graph showing the result of improvement in the amount of warpage of the resin-sealed semiconductor device according to the present invention.

FIG. 7 is a diagram showing a state of measuring a withstand amount of an insulating substrate with respect to a screw tightening torque in mounting the resin-sealed semiconductor device according to the present invention.

FIG. 8 is a diagram showing the result of the measurement clarified in FIG. 7;

FIG. 9 is a top view of the resin-sealed semiconductor device according to the present invention.

FIG. 10 is a connection diagram of a semiconductor element incorporated in the resin-sealed semiconductor device according to the present invention. FIG. 10A is a connection diagram using a single semiconductor device. FIG. 10B is a connection diagram using two semiconductor elements. FIG. 10c is a connection diagram of six semiconductor elements.

[Explanation of symbols]

 1, 14: heat sink, 2, 10, 11: semiconductor element, 3, 12: insulating substrate, 4, 15: solder layer, 5, 16: external terminal, 13: metal plate, 6, 17: sealing resin Layer 18: Resin-sealed semiconductor device 19: Stainless steel plate 20: Piano wire

Claims (2)

(57) [Claims] 1. A ceramic having a conductive metal layer on both sides.
Substrate and semiconductor fixed to one side of this ceramic substrate
A device, and the device is electrically connected to the semiconductor device.
An external terminal installed on the
A heat sink fixed to the other surface of the board and one surface of this heat sink
From the exposed sealing resin layer covering the ceramic substrate
Semiconductor device, the other surface of the ceramic substrate and
And between the heat sinks, both sides of the ceramic base
A solder layer is interposed on the other surface of the plate and one surface of the heat sink, respectively.
Characterized by having a metal plate fixed and fixed
Stop type semiconductor device. 2. The ceramic substrate according to claim 1, wherein said ceramic substrate is alumina,
Characterized as either luminium or beryllia
The resin-encapsulated semiconductor device according to claim 1.