JP2020098882A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device capable of ensuring sufficiently high electric insulation (breakdown voltage). A semiconductor device (1) includes a semiconductor module (10), a heat dissipation plate (20), and an electrical insulation sheet (30). The semiconductor module 10 has a semiconductor element 11 and a lead frame 12 each formed in a plate shape, and one side surface of the lead frame 12 is electrically connected so as to be superposed on one side surface of the semiconductor element 11. The semiconductor element 11 and the lead frame 12 are covered with the sealing portion 13 made of an electrically insulating material, except for the other side surface of the lead frame 12. The heat dissipation plate 20 is arranged facing the other side surface of the lead frame 12. The electrically insulating sheet 30 is sandwiched between the semiconductor module 10 and the heat dissipation plate 20. The heat dissipation plate 20 has a wall surface that surrounds the outer peripheral edge portion of the electric insulating sheet 30, restrains the outer peripheral edge portion of the electric insulating sheet 30, and deforms so that the outer peripheral edge portion of the electric insulating sheet 30 extends outward. The restraint part (frame part 22 or recessed part RP) is provided. [Selection diagram] Figure 2

Description

The present invention relates to a semiconductor device and its manufacturing method.

For example, as described in Patent Document 1 below, a semiconductor module including a plurality of semiconductor elements and a lead frame is known. The semiconductor element generates heat as it operates. Particularly, the amount of heat generated by a semiconductor device having a relatively large output power is large. Therefore, in order to prevent thermal destruction of the semiconductor element, a radiator (for example, a radiation fin) is attached to the semiconductor module to improve the cooling efficiency of the semiconductor module.

Generally, the conventional semiconductor device as described above is manufactured as follows. First, a semiconductor module is manufactured as follows. A lead frame (die pad) is bonded to a side surface (for example, a lower surface) of the thin plate semiconductor element. Next, in order to improve the impact resistance of the semiconductor element and the lead frame and to prevent the creeping discharge between the electrodes, a part of the semiconductor element and the lead frame is sealed with an electrically insulating material (synthetic resin material). It Specifically, a semiconductor element bonded to a lead frame is placed in a predetermined mold, a synthetic resin material (for example, a thermosetting resin material) is poured into the mold, and the synthetic resin material is Solidified. In this way, the semiconductor module is manufactured. As described above, of the components of the semiconductor module, the portion other than the lower surface of the lead frame is covered with the synthetic resin material.

Next, the electric insulating sheet is placed on the surface of the radiator, and the semiconductor module is placed on the electric insulating sheet. That is, the lower surface of the lead frame is brought into contact with the upper surface of the electrical insulating sheet. The electrically insulating sheet is made of an electrically insulating material (for example, a thermoplastic resin material) and electrically insulates between the lead frame and the radiator. Finally, the electric insulating sheet (or the entire apparatus) is heated to soften the surface of the electric insulating sheet, and the semiconductor module and the electric insulating sheet are brought into close contact with each other, and the radiator and the electric insulating sheet are brought into close contact with each other. Then, the electrically insulating sheet is cooled and solidified. Thus, the electrically insulating sheet not only electrically insulates the semiconductor module and the radiator, but also has a function of adhering the two.

JP, 2003-153554, A

In the process of assembling the semiconductor device, the semiconductor module and the electric insulating sheet are brought into close contact with each other, and the radiator and the electric insulating sheet are brought into close contact with each other. Therefore, it is preferable to soften the electric insulating sheet while pressing the semiconductor module toward the radiator. At this time, in order to prevent the semiconductor element in the semiconductor module from being pressed and destroyed, it is preferable to press a part of the semiconductor module that is slightly away from directly above the semiconductor element. For example, the outer peripheral edge of the semiconductor module may be partially pressed. However, in this case, as shown in FIG. 11, the outer peripheral edge portion of the electrical insulating sheet may be intensively pressed and the portion may be deformed (protruded) to extend outward. In particular, when the outer peripheral edge portion of the lower surface of the semiconductor module is warped so as to sink downward as compared with the central portion, the above-mentioned protrusion amount becomes large and the crushing amount of the outer peripheral edge portion of the electrical insulating sheet becomes relatively large. Therefore, the electrical insulation distance between the semiconductor module and the radiator becomes relatively small. That is, the electrical insulation (breakdown voltage) is reduced.

The present invention has been made to solve the above problems, and an object thereof is to provide a semiconductor device capable of ensuring a sufficiently high electrical insulation property (breakdown voltage) and a method for manufacturing the same. In the following description of each constituent feature of the present invention, in order to facilitate understanding of the present invention, reference numerals of corresponding portions of the embodiment are shown in parentheses, but each constituent feature of the present invention is It should not be construed as being limited to the configuration of corresponding portions indicated by the reference numerals of the embodiment.

In order to achieve the above object, a semiconductor device (1) according to the present invention has a semiconductor element (11) and a lead frame (12) each formed in a plate shape, and one side surface of the lead frame is A sealing portion that is electrically connected so as to be superposed on one side surface of the semiconductor element, and a portion of the semiconductor element and the lead frame other than the other side surface of the lead frame is made of an electrically insulating material ( 13) a semiconductor module (10) covered by the other side surface of the lead frame and a radiator (20) facing the other side surface of the lead frame, and heated to a viscosity. And an electric insulating sheet (30) sandwiched between the semiconductor module and the radiator, the radiator surrounding an outer peripheral edge portion of the electric insulating sheet. A restraint portion (22, RP) is provided. Further, the method for manufacturing a semiconductor device of the present invention includes the step of applying a temperature difference between the outer peripheral portion and the central portion of the electrical insulating sheet while pressing the outer peripheral portion of the semiconductor module toward the radiator. ..

In one aspect of the present invention, the frame portion (22) is a convex portion protruding from the surface of the radiator.

In another aspect of the present invention, the restraint portion is a recess (RP) provided on the surface of the radiator.

In the semiconductor device according to the present invention, the outer peripheral edge portion of the electrically insulating sheet is surrounded by the restraint portion. Therefore, even if the outer peripheral edge portion of the electrically insulating sheet is pressed downward, it cannot be deformed so as to extend outward (extend from the semiconductor module). Therefore, the outer peripheral edge portion of the electrically insulating sheet is unlikely to be crushed. Therefore, electric insulation (breakdown voltage) can be sufficiently high.

It is a perspective view of a semiconductor device (inverter device) concerning one embodiment of the present invention. FIG. 2 is an exploded perspective view of the semiconductor device shown in FIG. 1. 2 is a plan view of the semiconductor device shown in FIG. 1. FIG. FIG. 4 is a sectional view taken along line AA of FIG. 3. FIG. 5 is a cross-sectional view showing a state in which the semiconductor module is warped and a gap is formed between the semiconductor module and the electrically insulating sheet in the semiconductor device shown in FIG. 4. FIG. 6 is a cross-sectional view showing a state in which a part of an outer peripheral edge portion of the semiconductor device shown in FIG. 5 flows in a central portion of an electrically insulating sheet to fill the gap. FIG. 11 is a cross-sectional view perpendicular to the front-rear direction of a semiconductor device according to a modification of the present invention. FIG. 11 is a cross-sectional view of a semiconductor device according to another modification of the present invention, which is perpendicular to the front-rear direction. FIG. 9 is a cross-sectional view showing an example in which an inclined surface is provided on the peripheral end surface of the semiconductor module and the peripheral wall surface of the recess in the semiconductor device shown in FIG. 8. FIG. 10 is a cross-sectional view showing a state in which the semiconductor module is bonded to a heat dissipation plate in the semiconductor device shown in FIG. 9. It is sectional drawing which shows the outer peripheral part of the electrically insulating sheet of the conventional semiconductor device, and its peripheral part.

As shown in FIGS. 1 to 3, the semiconductor device 1 according to the embodiment of the present invention includes a semiconductor module 10, a heat dissipation plate 20, and an electrical insulating sheet 30. The semiconductor device 1 is an inverter device that drives an electric motor (three-phase AC motor) for running a hybrid vehicle. That is, the semiconductor device 1 is connected to the electric motor, the control device, and the DC power supply device, and converts the DC power supplied from the DC power supply device into three-phase AC power based on the drive signal supplied from the control device. And supply it to the electric motor. Note that the present embodiment is an example in which the present invention is applied to an inverter device, but the present invention is also applicable to other semiconductor devices.

The semiconductor module 10 is formed in a rectangular plate shape. In the following description, the direction parallel to the thickness direction of the semiconductor module 10 is called the vertical direction. Further, a direction parallel to the extending direction of the long side of the semiconductor module 10 is called a left-right direction. The direction parallel to the extending direction of the short side of the semiconductor module 10 is called the front-back direction.

As shown in FIG. 4, the semiconductor module 10 includes a plurality of semiconductor elements (transistors) 11 and a lead frame 12.

The semiconductor element 11 is formed in a thin plate shape. The semiconductor element 11 is arranged so that the plate thickness direction thereof coincides with the vertical direction. The semiconductor element 11 has a substantially square shape in plan view. One side of the semiconductor element 11 is parallel to the left-right direction, and the other side is parallel to the front-rear direction.

The lead frame 12 is a plate-shaped member made of metal (for example, aluminum or copper). The lead frame 12 is arranged so that the plate thickness direction thereof coincides with the vertical direction. A plurality of semiconductor elements 11 are electrically connected to the upper surface of the lead frame 12. The plurality of semiconductor elements 11 are arranged on the upper surface of the lead frame 12 at equal intervals in the left-right direction. Electronic parts, terminals, and the like (not shown) different from the semiconductor element 11 are arranged on the upper side of the lead frame 12, and are electrically connected to the semiconductor element 11 and the lead frame 12.

A plurality of components connected to each other as described above are arranged in a mold (not shown), and the thermosetting resin material is poured into the mold. Then, the thermosetting resin material is solidified to form the sealing portion 13. That is, the portion of the lead frame 12 located above when viewed from the lower surface is covered with the sealing portion 13 made of a thermosetting resin material. In other words, in the semiconductor module 10, only the lower surface of the lead frame 12 is exposed and the other portions are covered by the sealing portion 13.

The heat sink 20 is a plate-shaped member made of metal (for example, aluminum or copper). The heat sink 20 includes a main body portion 21 and a frame portion 22. The main body 21 and the frame 22 are integrally formed. The body portion 21 is a substantially rectangular plate-shaped portion. The heat radiating plate 20 is arranged so that the plate thickness direction of the main body portion 21 coincides with the vertical direction.

The frame portion 22 projects from the upper surface of the main body portion 21. The frame portion 22 is arranged in the central portion of the main body portion 21. The frame portion 22 has a rectangular shape extending in the left-right direction. That is, the frame portion 22 has a pair of front and rear convex portions 221 and 222 forming its long side and a pair of left and right convex portions 223 and 224 forming its short side. The cross sections perpendicular to the longitudinal direction of the convex portions 221, 222 and the convex portions 223, 224 have a substantially square shape (see FIG. 4 ). The left-right dimension and the front-rear dimension of the inner peripheral edge of the frame portion 22 are equal to the left-right dimension and the front-rear dimension of the outer peripheral edge of the semiconductor module 10. The frame portion 22 corresponds to the restraint portion of the present invention.

The electric insulating sheet 30 is a sheet-shaped member made of a thermoplastic resin. The shape and size of the electrically insulating sheet 30 are the same as the shape and size of the lower surface of the semiconductor module 10.

The semiconductor module 10 and the heat sink 20 are adhered to each other by the electric insulating sheet 30 as follows (adhesion step). First, the electrically insulating sheet 30 is sandwiched between the semiconductor module 10 and the heat sink 20. As shown in FIG. 4, the outer peripheral edge portion of the electrical insulating sheet 30 is located below the outer peripheral edge portion of the sealing portion 13. Next, the semiconductor module 10, the heat dissipation plate 20, and the electrical insulating sheet 30 are heated while the outer peripheral edge portion on the upper surface of the semiconductor module 10 is pressed downward, and the electrical insulating sheet 30 is softened. After that, the semiconductor module 10, the heat sink 20 and the electrical insulating sheet 30 are cooled. As a result, the electrically insulating sheet 30 is solidified, and the semiconductor module 10 and the heat sink 20 are bonded by the electrically insulating sheet 30.

As described above, in the step of bonding the semiconductor module 10 and the heat dissipation plate 20, the outer peripheral edge portion of the semiconductor module 10 is pressed downward. Therefore, the outer peripheral edge of the electrical insulating sheet 30 is pressed downward by the outer peripheral edge of the sealing portion 13. Here, the peripheral end surface of the electrically insulating sheet 30 is surrounded by the frame portion 22. That is, the peripheral end surface of the electrical insulating sheet 30 faces the inner peripheral surface (wall surface) of the frame portion 22. Therefore, the outer peripheral edge portion of the electrical insulating sheet 30 cannot be deformed so as to extend outward (extend from the semiconductor module 10) even if pressed downward. Therefore, the outer peripheral edge portion of the electrical insulating sheet 30 is unlikely to be crushed. Therefore, according to the present embodiment, it is possible to secure a sufficiently high electrical insulation property (electrical insulation distance).

By the way, in the conventional semiconductor module, when the outer peripheral edge portion is warped so as to sink downward as compared with the central portion, a gap (air layer) is formed between the lower surface of the semiconductor module and the electrical insulating sheet. To be done. In this case, the heat dissipation of the semiconductor module is reduced. Further, in this case, the bonding area is relatively small and the bonding strength between the semiconductor module and the radiator is low.

In the present embodiment, since the outer peripheral edge portion of the electrically insulating sheet 30 cannot be deformed so as to extend outward, even if the outer peripheral edge portion of the upper surface of the semiconductor module 10 is pressed downward, the outer peripheral portion of the semiconductor module 10 becomes the central portion. It is difficult to deform so that it sinks downward compared to. That is, the warp of the semiconductor module 10 can be suppressed.

Here, as shown in FIG. 5, a case will be described in which the semiconductor module 10 is slightly warped and a gap S is formed between the lower surface of the semiconductor module 10 and the electrical insulating sheet 30. In this case, the outer peripheral edge portion of the electrically insulating sheet 30 is restricted by the frame portion 22 from deforming so as to extend outward. However, a part of the outer peripheral edge portion of the electrical insulation sheet 30 can move (flow) to the central portion side of the electrical insulation sheet 30. As a result, as shown in FIG. 6, the thickness of the central portion of the electrically insulating sheet 30 is slightly increased, and the gap S is filled. That is, the electrical insulating sheet 30 is in close contact with the lower surface of the semiconductor module 10. Thereby, the heat dissipation of the semiconductor module 10 is maintained high. Furthermore, the joint strength between the semiconductor module 10 and the heat sink 20 is maintained high.

Further, the number of parts is smaller than that in the case where the outer peripheral edge portion of the semiconductor module 10 and the heat dissipation plate 20 are fixed using fastening members (bolts). Further, the semiconductor device 1 can be downsized.

The electrically insulating sheet 30 may include a filler (eg, hexagonal boron nitride). In this case, it is preferable that fillers are arranged in the sheet thickness direction of the electrical insulation sheet 30 so that the thermal conductivity of the electrical insulation sheet 30 in the sheet thickness direction is set high.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

For example, in the above embodiment, the main body 21 and the frame 22 of the heat dissipation plate 20 are integrally formed, but as shown in FIG. 7, the main body 21 and the frame 22 are formed as separate bodies. May be In this case, the frame member 22 may be made of synthetic resin. Further, in this case, it is preferable to provide the main body portion 21 with the groove portion G ₂₂ into which the frame portion 22 is fitted. In this case, the position of the frame portion 22 in the main body portion 21 can be easily fixed, and the displacement of the semiconductor module 10 and the electrical insulating sheet 30 can be prevented.

Further, instead of providing the frame portion 22 protruding from the upper surface of the main body portion 21, as shown in FIG. 8, a concave portion RP for accommodating the electrically insulating sheet 30 and the semiconductor module 10 is provided in the central portion of the main body portion 21. May be. That is, the bottom wall surface RPa of the recessed portion RP is perpendicular to the vertical direction, and the peripheral wall surface RPb of the recessed portion RP is perpendicular to the bottom wall surface RPa, so that the peripheral end surface of the electrical insulating sheet 30 faces the peripheral wall surface RPb. Good.

In this case, as shown in FIGS. 9 and 10, the lower half portion RPb1 of the peripheral wall surface RPb of the recess RP is perpendicular to the bottom wall surface RPa, and the upper half portion RPb2 of the peripheral wall surface RPb is lower than the lower half portion RPb1. May be inclined. Then, the peripheral end surface 13a of the sealing portion 13 may be inclined so as to match the upper half portion RPb2. According to this, when the outer peripheral edge portion of the upper surface of the semiconductor module 10 is pressed downward, a force for the semiconductor module 10 to spread the concave portion RP acts (wedge effect). That is, the semiconductor module 10 is pressed into the recess RP. Therefore, compared with the case where the semiconductor module 10 and the heat sink 20 are joined only by the adhesive force of the electrical insulating sheet 30, the joining force between the semiconductor module 10 and the heat sink 20 is large.

In addition, in the bonding step, the temperature of the outer peripheral edge portion may be lower than that of the central portion of the electrical insulating sheet 30 so that the viscosity of the outer peripheral edge portion is lower than that of the central portion. For example, first, the central portion of the electrically insulating sheet 30 may be heated, and then the entire electrically insulating sheet 30 may be heated. Further, for example, the semiconductor module 10 may be pressed against the electrical insulating sheet 30 in a state where the entire electrical insulating sheet 30 is heated and only the outer peripheral edge portion of the semiconductor module 10 is cooled. According to this, the outer peripheral edge portion of the electrically insulating sheet 30 is unlikely to be crushed, so that it is easy to secure sufficiently high electrical insulation.

The electrically insulating sheet 30 may be made of a thermoplastic resin material. Also in this case, in the bonding step, a temperature difference may be applied between the central portion and the outer peripheral edge portion of the electrical insulating sheet 30 so that the viscosity of the outer peripheral edge portion of the electrical insulating sheet 30 becomes lower than that of the central portion.

DESCRIPTION OF SYMBOLS 1... Semiconductor device, 10... Semiconductor module, 11... Semiconductor element, 12... Lead frame, 13... Sealing part, 20... Heat sink, 21... Main body part, 22... Frame part, 30... Electrical insulating sheet, RP... Recessed part , RPa... bottom wall surface, RPb... peripheral wall surface, RPb1... lower half portion, RPb2... upper half portion, S... gap

Claims (4)

A semiconductor device and a lead frame, each of which is formed in a plate shape, and one side surface of the lead frame is electrically connected so as to be superposed on one side surface of the semiconductor device. A semiconductor module in which a portion of the lead frame excluding the other side surface of the lead frame is covered with a sealing portion made of an electrically insulating material, and the other side surface of the lead frame is exposed,
A radiator arranged facing the other side surface of the lead frame,
An electrically insulating sheet, which is composed of an electrically insulating material whose viscosity is changed by being heated, and which is sandwiched between the semiconductor module and the radiator,
The semiconductor device, wherein the radiator includes a restraint portion that surrounds an outer peripheral edge portion of the electrically insulating sheet. The semiconductor device according to claim 1,
The semiconductor device, wherein the restraint portion is a frame portion including a convex portion protruding from a surface of the radiator. The semiconductor device according to claim 1,
The semiconductor device, wherein the restraint portion is a recess provided on the surface of the radiator. A semiconductor device and a lead frame, each of which is formed in a plate shape, and one side surface of the lead frame is electrically connected so as to be superposed on one side surface of the semiconductor device. A portion of the lead frame excluding the other side surface of the lead frame is covered with a sealing portion made of an electrically insulating material, and the other side surface of the lead frame is exposed; A heat radiator disposed opposite to the other side surface, and an electric insulating sheet composed of an electric insulating material that changes in viscosity when heated, and an electric insulating sheet sandwiched between the semiconductor module and the heat radiator. Is a method of manufacturing a semiconductor device, comprising: a restraint portion surrounding an outer peripheral edge portion of the electrical insulating sheet,
A method of manufacturing a semiconductor device, comprising the step of applying a temperature difference between the outer peripheral portion and the central portion of the electrical insulating sheet while pressing the outer peripheral portion of the semiconductor module toward the radiator.

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