SEMICONDUCTOR MODULE AND MANUFACTURING METHOD THEREFOR

A method includes electrically connecting first and second semiconductor elements to conductive plates, respectively, on the front surface of one or more insulating substrates disposed on a metal base; disposing, on the base, a case including a chassis, a first lead frame having a first wiring part extending in a wired direction parallel to the front surface, and a second lead frame having a second wiring part in the wiring direction to overlap the first wiring part with gap that are integrally molded together; and attaching one or more insulating members that include a clamping part sandwiching the first and second wiring parts from the rear surface of the first wiring part and the front surface of the second wiring part in an attachment area thereof and a wiring gap part filling the gap in the attachment area, before joining the lead frames to circuit patterns, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2023-034194, filed on Mar. 7, 2023, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The embodiments discussed herein relate to a semiconductor module and manufacturing method therefor.

2. Background of the Related Art

Some known semiconductor modules are provided with insulating blocks in order to maintain a certain distance or more between two plate-like terminal conductors that overlap in plan view (see, for example, International Publication Pamphlet No. WO 2014/073311). Other known semiconductor modules are equipped with a wiring holding part, which includes a portion filling a gap in where two lead frames overlap each other in plan view, in order to prevent a short circuit between the two lead frames even when the gap is insufficiently filled with a sealing member (see, for example, International Publication Pamphlet No. WO 2021/029150).

SUMMARY OF THE INVENTION

According to an aspect, there is provided a method for manufacturing a semiconductor module, the method including: disposing, on a metal base, one or more insulating substrates each having, on a front surface thereof, a first semiconductor element, a second semiconductor element, a first conductive plate, and a second conductive plate; connecting electrically the first semiconductor element and the second semiconductor element to the first conductive plate and the second conductive plate, respectively; disposing, on the metal base, a case including a first lead frame, a second lead frame, and a frame-like chassis that are integrally molded together, the first lead frame including a first wiring part that extends in parallel to the front surface of the one or more insulating substrates, and the second lead frame including a second wiring part that extends in a wiring direction of the first wiring part in such a manner as to overlap the first wiring part with a gap from a front surface of the first wiring part; joining the first lead frame and the second lead frame to a first circuit pattern and a second circuit pattern, respectively, on the metal base; and attaching, before the joining of the first lead frame and the second lead frame to the first circuit pattern and the second circuit pattern, respectively, one or more insulating members, each including a clamping part and a wiring gap part, to an attachment area provided in part of where the first wiring part and the second wiring part overlap each other, the clamping part sandwiching the first and second wiring parts at the attachment area from a rear surface of the first wiring part and a front surface of the second wiring part, and the wiring gap part filling the gap between the first and second wiring parts in the attachment area.

DETAILED DESCRIPTION OF THE INVENTION

Several embodiments will be described below with reference to the accompanying drawings.

Note that in the following the terms “front surface” and “top face” refer to the X-Y plane facing upward (the +Z direction) in a semiconductor module10and the like ofFIGS.1and2. Similarly, the term “upper” refers to the upward direction (the +Z direction) of the illustrated semiconductor module10and the like ofFIGS.1and2. On the other hand, the terms “rear surface” and “bottom face” refer to the X-Y plane facing downward (the −Z direction) in the illustrated semiconductor module10and the like ofFIGS.1and2. Similarly, the term “lower” refers to the downward direction (the −Z direction) of the illustrated semiconductor module10and the like ofFIGS.1and2. These terms have the same orientational relationships in other drawings if needed. The terms “front surface”, “top face”, “upper”, “rear surface”, “bottom face”, “lower”, and “lateral face” are simply expedient expressions used to specify relative positional relationships, and are not intended to limit the technical ideas of the embodiments described herein. For example, the terms “upper” and “lower” do not necessarily imply the vertical direction to the ground surface. That is, the “upper” and “lower” directions are not defined in relation to the direction of the gravitational force.

(a) First Embodiment

Next described are a semiconductor module and a manufacturing method therefor according to a first embodiment, with reference toFIGS.1to9.

FIG.1is a perspective view of the semiconductor module according to the first embodiment.FIG.2is a plan view of the semiconductor module according to the first embodiment.

The example ofFIGS.1and2depicts the semiconductor module10including functions of a three-phase inverter circuit. The semiconductor module10includes a metal base11, a first insulating substrate21a, a second insulating substrate21b, a case30, a first insulating member40, and a second insulating member50.

The metal base11is used for heat dissipation of the semiconductor module10, and mainly formed of a metal with excellent thermal conductivity. Examples of such a metal are copper, aluminum, and an alloy containing at least one of these metals. Plating may be applied to the metal base11in order to provide improved corrosion resistance. In this case, a material used for plating is nickel, a nickel-phosphorus alloy, or a nickel-boron alloy, for example.

The first insulating substrate21aand the second insulating substrate21bare disposed on the metal base11. The first insulating substrate21aand the second insulating substrate21bare fixed to the metal base11by, for example, soldering. The first insulating substrate21aand the second insulating substrate21bare made of ceramics with excellent thermal conductivity. Example of such ceramics are high-temperature conductive aluminum oxide, aluminum nitride, and silicon nitride.

On the front surface of the first insulating substrate21a, a first semiconductor element22aand a first conductive plate23aelectrically connected to the first semiconductor element22aare provided, as illustrated inFIG.2. Similarly, on the front surface of the second insulating substrate21b, a second semiconductor element22band a second conductive plate23belectrically connected to the second semiconductor element22bare provided.

Each of the first semiconductor element22aand the second semiconductor element22bdepicted inFIG.2includes a switching element, such as a power metal oxide semiconductor field effect transistor (power MOSFET) and an insulated gate bipolar transistor (IGBT). The first semiconductor element22afunctions as a switching element of the upper arm while the second semiconductor element22bfunctions as a switching element of the lower arm. When such switching elements are power MOSFETs, each has, on its rear surface, a drain electrode (an input electrode) as a main electrode, and also has, on its front surface, a gate electrode (a control electrode) as a main electrode and a source electrode (an output electrode). When the switching elements are IGBTs, each has, on its rear surface, a collector electrode (an input electrode) as a main electrode, and also has, on the front surface, a gate electrode (a control electrode) as a main electrode and an emitter electrode (an output electrode).

Note that the first semiconductor element22aand the second semiconductor element22bmay be reverse-conducting IGBTs (RC-IGBTs). Each RC-IGBT has integrated functions of both an IGBT and a free-wheeling diode (FWD), which is a diode element. Alternatively, the first semiconductor element22aand the second semiconductor element22bmay be power MOSFETs made of silicon carbide. Further, the body diode of each power MOSFET (including those made of silicon carbide) may perform similar functions as an FWD of an RC-IGBT.

The first conductive plate23ais included in a circuit pattern provided on the front surface of the first insulating substrate21a. The second conductive plate23bis included in a circuit pattern provided on the front surface of the second insulating substrate21b. These circuit patterns are made of a metal with excellent electrical conductivity. The metal is, for example, copper or a copper alloy. Appropriate choices may be made for the number of circuit patterns and their shapes according to the specifications of the semiconductor module10and the like. As the first insulating substrate21aand the second insulating substrate21bwith such circuit patterns formed thereon, for example, direct copper bonding (DCB) substrates or active metal brazed (AMB) substrates may be used.

The rear surface of the first semiconductor element22aand the front surface of the first conductive plate23aare joined by, for example, soldering, and thereby the first semiconductor element22aand the first conductive plate23aare electrically connected. Note that the output electrode of the first semiconductor element22ais electrically connected to a third conductive plate23cincluded in the circuit pattern provided on the front surface of the first insulating substrate21a. The gate electrode of the first semiconductor element22ais electrically connected to control terminals35aprovided in the case30. Although not illustrated in the figures, wiring members such as bonding wires are used for electrical connection.

The output electrode of the second semiconductor element22bis electrically connected to the second conductive plate23bby, for example, a wiring member (not illustrated) such as a bonding wire. The gate electrode of the second semiconductor element22bis also electrically connected to control terminals35bprovided in the case30by, for example, a wiring member (not illustrated) such as a bonding wire. Note that the rear surface of the second semiconductor element22bis joined to the front surface of a fourth conductive plate23dincluded in the circuit pattern on the front surface of the second insulating substrate21bby, for example, soldering.

Other semiconductor elements may be provided on the first insulating substrate21aand the second insulating substrate21b. In the example ofFIGS.1and2, a semiconductor element24bincluding a diode is disposed on the second insulating substrate21b. The diode is, for example, a Schottky barrier diode (SBD) or a P-intrinsic-N (PiN) diode, and is connected in inverse parallel to the switching element as an FWD. The semiconductor element24bhas an output electrode (cathode electrode) as a main electrode on the rear surface, and an input electrode (anode electrode) as a main electrode on the front surface. The rear surface of the semiconductor element24bis joined to the front surface of the fourth conductive plate23dby soldering. The input electrode on the front surface of the semiconductor element24bis electrically connected to the second conductive plate23bby, for example, a wiring member (not illustrated) such as a bonding wire.

Although hidden below a second lead frame32(in the −Z direction) inFIGS.1and2, a semiconductor element including a similar diode is also provided on the first insulating substrate21a.

Although a detailed explanation is omitted, three pairs of the first insulating substrate21aand the second insulating substrate21bon which the individual semiconductor elements and conductive plates described above are provided are disposed in the X direction on the metal base11. In addition, an insulting substrate with a brake circuit and the like formed thereon may be placed on the metal base11.

The case30is obtained by integrally molding a first lead frame31, the second lead frame32, and a third lead frame33as well as various terminals, including the aforementioned control terminals35aand35b, together with a frame-like chassis34.

The first lead frame31, the second lead frame32, and the third lead frame33are external connection terminals for a main current.

The first lead frame31includes a first wiring part (a first wiring part31aofFIG.3to be described later) that is wired parallel to the front surfaces of the first insulating substrate21aand the second insulating substrate21b, and is joined to the first conductive plate23a. Soldering, ultrasonic bonding, or the like is used to join the first lead frame31and the first conductive plate23a. Both ends of the first lead frame31function as terminal parts31band31c. The terminal parts31band31care exposed at the top of the chassis34and at the front surface of a lid (not illustrated) of the semiconductor module10.

The second lead frame32includes a second wiring part (a second wiring part32aofFIG.3to be described later) which runs along the wiring direction (the X direction) of the first wiring part in such a manner as to overlap the first wiring part with a gap from the front surface of the first wiring part. The second lead frame32is joined to the second conductive plate23b. Soldering, ultrasonic bonding, or the like is used to join the second lead frame32and the second conductive plate23b. Both ends of the second lead frame32function as terminal parts32band32c. The terminal parts32band32care exposed at the top of the chassis34and at the front surface of the aforementioned lid (not illustrated) of the semiconductor module10.

The third lead frame33is joined to the third conductive plate23cand the fourth conductive plate23d. Soldering, ultrasonic bonding, or the like is used to join the third lead frame33to the third conductive plate23cand the fourth conductive plate23d. One end of the third lead frame33functions as a terminal part33a. The terminal part33ais exposed at the top of the chassis34, and serves as one of output terminals (a U-terminal, V-terminal, and W-terminal) of the semiconductor module10.

The first lead frame31, the second lead frame32, and the third lead frame33are made of a material with excellent electrical conductivity. The material is, for example, aluminum, iron, silver, copper, or an alloy containing at least one of these.

The first insulating member40has, for example, the following configuration.

FIG.3is a cross-sectional view illustrating an attachment example of the first insulating member.FIG.3depicts the first insulating member40, the first wiring part31aof the first lead frame31, and the second wiring part32aof the second lead frame32in a cross section taken along dashed-dotted line III-III ofFIG.2.

The first insulating member40includes a clamping part40awhich is installed in an attachment area provided in part of where the first wiring part31aand the second wiring part32aoverlap each other. The clamping part40asandwiches the first wiring part31aand the second wiring part32aby holding the rear surface of the first wiring part31aand the front surface of the second wiring part32a. The first insulating member40also includes a wiring gap part40bthat fills a gap between the first wiring part31aand the second wiring part32ain the aforementioned attachment area.

The clamping part40aincludes a first portion40a1in contact with the front surface of the second wiring part32a, and a second portion40a2in contact with the rear surface of the first wiring part31a. Further, in the example of the first insulating member40depicted inFIG.3, the clamping part40aincludes a third portion40cthat connects lateral sides40a3and40a4of the first portion40a1and the second portion40a2, respectively. The lateral sides40a3and40a4run parallel to the foregoing wiring direction and both lie in the same plane.

In the above, the first insulating member40is described separately into the clamping part40aand the wiring gap part40bin order to explain the shape of the first insulating member40; however, the clamping part40aand the wiring gap part40bmay be manufactured in one piece. Regarding the size of the first insulating member40, there are no particular restrictions; however, it is preferable to have a size that does not interfere with structures below, such as bonding wires. The first insulating member40may be produced by, for example, a three-dimensional printer, molding, resin cutting, or the like.

The above-described first insulating member40is attached in a process performed before a joining process in which the first lead frame31and the second lead frame32are joined to the first conductive plate23aand the second conductive plate23b, respectively, as described later.

The second insulating member50has the following configuration, for example.

FIG.4is a cross-sectional view of a second insulating member.FIG.4depicts the second insulating member50, the first wiring part31aof the first lead frame31, and the second wiring part32aof the second lead frame32in a cross section taken along dashed-dotted line IV-IV ofFIG.2.

The second insulating member50is formed to cover the front and rear surfaces of the second wiring part32aas well as two lateral faces thereof opposing perpendicularly to the wiring direction (i.e., in the +Y direction). In addition, the second insulating member50may be formed to further cover the rear surface of the first wiring part31aas well as two lateral faces thereof opposing perpendicularly to the wiring direction (i.e., in the #Y direction). The foregoing second insulating member50is formed before a process of manufacturing the case30by integral molding, as described later.

The first insulating member40and the second insulating member50are made of, for example, a thermoplastic resin. As such a thermoplastic resin, any of the following may be used: poly phenylene sulfide (PPS); polypropylene terephthalate (PPT); polybutylene terephthalate (PBT); polybutylene succinate (PBS); polyamide (PA); and acrylonitrile butadiene styrene (ABS).

Note that the first insulating member40and the second insulating member50each may be provided in plurality. The first insulating member40is removable during the process of manufacturing the semiconductor module10. The effects of installing the first insulating member40and the second insulating member50are described later.

Although not illustrated, the semiconductor module10further includes a printed circuit board that is electrically connected to various terminals, such as the control terminals35aand35bof the case30; a sealing member filled in a housing area surrounded by the chassis34; and a lid for sealing the case30.

(Method for Manufacturing Semiconductor Module10)

FIG.5is a flowchart illustrating an example of a method for manufacturing the semiconductor module according to the first embodiment.(Step S1) A preparing process is performed for preparing each component of the semiconductor module10. Parts and other materials are prepared for making the metal base11; the first insulating substrate21aand the second insulating substrate21bwith circuit patterns including, for example, the first conductive plate23aand the second conductive plate23b, respectively; the first semiconductor element22a; the second semiconductor element22b; and the case30. Parts for manufacturing the case30include, for example, the first lead frame31, the second lead frame32, the third lead frame33, the chassis34, the control terminals35aand35b, and the first insulating member40. The first insulating member40is produced in advance by, for example, a three-dimensional printer, metal molding, or resin cutting.(Step S2) A coupled part forming process is performed to form a coupled part in which the first lead frame31, the second lead frame32, and the second insulating member50are integrated into one piece. Such a coupled part may be formed by integral molding using a mold. The second insulating member50is formed such as to cover the front and rear surfaces of the second wiring part32aof the second lead frame32as well as the two lateral faces thereof opposing perpendicularly to the wiring direction, as illustrated inFIG.4. The lower surface of the second insulating member50covers the front surface of the first wiring part31aof the first lead frame31. Note that the second insulating member50may be configured to further cover the rear surface of the first wiring part31aas well as the two lateral faces thereof opposing perpendicularly to the wiring direction.(Step S3) A first disposing process is performed. In the first disposing process, the first insulating substrate21aand the second insulating substrate21bare placed on the metal base11. The first insulating substrate21aand the second insulating substrate21bare fixed to the metal base11by, for example, soldering. Further in the first disposing process, individual semiconductor elements are placed on the circuit patterns on the front surfaces of the first insulating substrate21aand the second insulating substrate21b. For example, the first semiconductor element22ais placed on the first conductive plate23aincluded in the circuit pattern of the first insulating substrate21a, and the second semiconductor element22bis placed on the fourth conductive plate23dincluded in the circuit pattern of the second insulating substrate21b, as illustrated inFIG.2.(Step S4) A first wiring process is performed. In the first wiring process, each semiconductor element is electrically connected to a predetermined circuit pattern (conductive plate). In the example ofFIG.2, the first semiconductor element22ais electrically connected to the first conductive plate23aby, for example, soldering the input electrode on the rear surface of the first semiconductor element22aand the front surface of the first conductive plate23a. The second semiconductor element22bis electrically connected to the second conductive plate23bby connecting the output electrode on the front surface of the second semiconductor element22bto the second conductive plate23bwith, for example, a wiring member such as a bonding wire.

Note that the output electrode of the first semiconductor element22ais electrically connected to the third conductive plate23cby, for example, a wiring member such as a bonding wire. The input electrode on the rear surface of the second semiconductor element22bis joined to the front surface of the fourth conductive plate23dby, for example, soldering.(Step S5) A case fabricating process is performed. The case30is fabricated by integrally molding the first lead frame31, the second lead frame32, the third lead frame33, and the foregoing various terminals, such as the control terminals35aand35b, together with the frame-like chassis34. In the case fabricating process, the first lead frame31, the second lead frame32, and the second insulating member50are set in a mold as an integrally coupled part. This prevents the proper positional relationship between the chassis34, the first lead frame31, and the second lead frame32from being impaired due to heat history during the integral molding in the case fabricating process. However, the second insulating member50does not need to be provided if such positional displacement need not be taken into account. In that case, the process of step S2may be omitted.(Step S6) An attaching process is performed. In the attaching process, the first insulating member40is installed in an attachment area provided in part of the first wiring part31aof the first lead frame31and the second wiring part32aof the second lead frame32, as explained with reference toFIG.3. The attachment area where the first insulating member40is installed is, for example, an area not interfering with structures below, such as bonding wires. Note that in the examples ofFIGS.1and2, a single first insulating member40is installed; however, multiple first insulating members40may be installed instead. Appropriate choices may be made to the number of first insulating members40and their attachment positions according to the situation of the structures located below.

The first insulating member40as illustrated inFIG.3is movable in the wiring direction (the X direction) of the first lead frame31and the second lead frame32. Therefore, even after being once installed, the first insulating member40may be adjusted to a position in the X direction. In the example ofFIG.3, the first insulating member40is E-shaped when viewed in the +X direction, and is removable from the first wiring part31aand the second wiring part32ain the +Y direction. Therefore, even after being once installed, the first insulating member40may be removed and reinstalled at a more appropriate position. This also offers improved flexibility in the installation of wiring members, such as bonding wires. Note that the attaching process may be performed manually or by an automatic machine.(Step S7) A second disposing process is performed. In the second disposing process, the case30produced in the process of step S5is placed on the metal base11. The case30is placed on the top face of the outer periphery of the metal base11and then fixed thereto using an adhesive, for example.(Step S8) A joining process is performed. In the joining process, the first lead frame31is joined to the first conductive plate23awhile the second lead frame32is joined to the second conductive plate23b.(Step S9) A second wiring process is performed. Wiring connection is made between the first and second semiconductor elements22aand22band the case30. For example, the gate electrode of the first semiconductor element22ais electrically connected to the control terminals35aof the case30by wiring members, such as bonding wires. Similarly, the gate electrode of the second semiconductor element22bis electrically connected to the control terminals35bof the case30.(Step S10) A removing process is performed. In this process, the first insulating member40is removed from the aforementioned attachment area. In the removing process, the first insulating member40is pulled out in the +Y direction in the example ofFIG.3. Note that the first insulating member40need not be removed unless it has a negative impact on other structures (such as bonding wires and a printed circuit board to be disposed later).(Step S11) A third disposing process is performed. A printed circuit board for controlling switching elements is disposed above the second lead frame32in the case30and then electrically connected to various terminals of the case30, such as the control terminals35aand35b.(Step S12) A sealing process is performed. A sealing member (an insulating resin material) is filled into the housing area surrounded by the chassis34and then hardened. By gluing a lid to the top face of the chassis34, the housing area is sealed. Herewith, the semiconductor module10is completed.

The order of the above-described processes is just an example. For example, the process of step S2may take place after the process of step S3or step S4, and the process of step S6may take place after the process of step S7. Further, the process of step S10may come between the processes of step S8and step S9, or between the processes of step S11and step S12.

As described above, in the method for manufacturing the semiconductor module10of the first embodiment, the attaching process of the first insulating member40precedes the process of joining the first lead frame31and the second lead frame32to the first conductive plate23aand the second conductive plate23b, respectively.

In the joining process, the first insulating member40is being attached to the first lead frame31and the second lead frame32, which prevents the first lead frame31from warping into a convex shape due to heat generated during joining and then coming into contact with the second lead frame32. Furthermore, the first insulating member40prevents the second lead frame32from warping into a concave shape and then coming into contact with the first lead frame31. Similar effects may be achieved by the second insulating member50ofFIG.4.

The second insulating member50seals a part of the second wiring part32aof the second lead frame32, as illustrated inFIG.4. Herewith, the second insulating member50is not removed from the second lead frame32and maintains the distance in the +Z direction between the second wiring part32aof the second lead frame32and the first wiring part31aof the first lead frame31, thus allowing insulation to be secured. However, the second insulating member50alone fails to sufficiently prevent the first lead frame31from warping into a concave shape. If such a deformation occurs, the first lead frame31strongly abuts against structures (such as bonding wires) on the first insulating substrate21aand the second insulating substrate21b, which may result in problems with the installation of the case30onto the metal base11, the installation of terminals, and the like. This may lead to reduced reliability of the semiconductor module10.

On the other hand, attachment of the first insulating member40to the first lead frame31and the second lead frame32, as depicted inFIG.3, prevents the first lead frame31from warping into a concave shape. This avoids the above problems from occurring, thereby reducing the loss of reliability of the semiconductor module10.

Note that, in the case of removing the first insulating member40in the process of step S10, the removed first insulating member40may also be used when manufacturing another semiconductor module. That is, the first insulating member40is reusable, and there is, therefore, no need to make a new first insulating member40each time a semiconductor module is manufactured.

In the above example, the semiconductor module10includes multiple insulating substrates, including the first insulating substrate21aand the second insulating substrate21b; however, the semiconductor module10may have only one insulating substrate.

Also, in the above example, the first lead frame31and the second lead frame32are joined to the first conductive plate23aand the second conductive plate23b, respectively; however, the applicable scope of the technology according to the first embodiment is not limited to this example. The first lead frame31is joined to the first circuit pattern on the metal base11while the second lead frame32is joined to the second circuit pattern on the metal base11. Different potentials are applied to the first lead frame31and the second lead frame32and, therefore, different potentials are applied to the first circuit pattern and the second circuit pattern. The first conductive plate23ais an example of the first circuit pattern, and the second conductive plate23bis an example of the second circuit pattern.

Furthermore, the first circuit pattern may be the main electrode on the front surface of the first semiconductor element22a, and the second circuit pattern may be the main electrode on the front surface of the second semiconductor element22b. In that case, each of these main electrodes is joined to the first lead frame31or the second lead frame32using, for example, a silver sintered material.

Note that the first circuit pattern (including the first conductive plate23a) or the main electrode on the front surface of the first semiconductor element22ais a specific example of a first conductive part. In addition, the second circuit pattern (including the second conductive plate23b) or the main electrode on the front surface of the second semiconductor element22bis a specific example of a second conductive part.

(Modifications of First Insulating Member)

FIG.6is a cross-sectional view illustrating a first modification of the first insulating member. InFIG.6, like reference numerals refer to identical components depicted inFIG.3.

The clamping part40aof a first insulating member41of the modification has barbs41d1and41d2at the tips of the lateral edges of the surfaces thereof which are respectively in contact with the front surface of the second wiring part32aand the rear surface of the first wiring part31a. The lateral edges run parallel to the wiring direction. The barbs41d1and41d2face the second wiring part32aand the first wiring part31a, respectively, from the tips. The foregoing first insulating member41may be installed in the attaching process of step S6ofFIG.5, in the same manner as the first insulating member40depicted inFIG.3.

Provision of the barbs41d1and41d2prevents the first insulating member41from coming off from the first lead frame31and the second lead frame32in the +Y direction. Note that when the first insulating member41of the first modification is used, the first insulating member41is not removed in the removing process of step S10described above.

FIG.7is a plan view of a semiconductor module, illustrating a second modification of the first insulating member.FIG.8is a cross-sectional view illustrating the second modification of the first insulating member.FIG.8depicts a first insulating member42, the first wiring part31aof the first lead frame31, the second wiring part32aof the second lead frame32, and a third wiring part32din a cross section taken along dashed-dotted line VIII-VIII ofFIG.7. InFIGS.7and8, like reference numerals refer to identical components depicted inFIGS.2and3. Note thatFIG.7omits illustration of the second insulating member50depicted inFIG.2.

In a semiconductor module10aofFIG.7, the second lead frame32has the third wiring part32d, which projects parallel to the front surface of the second wiring part32afrom the second wiring part32a.

In the first insulating member42, the first portion40a1of the clamping part40aand the wiring gap part40binclude extension portions42aand42b, respectively, to sandwich the third wiring part32dtherebetween. The use of the first insulating member42prevents the third wiring part32d, which projects parallel to the front surface of the second wiring part32afrom the second wiring part32a, from becoming deformed in the joining process of step S8ofFIG.5described above.

Note that the first insulating member42may be removed in the removing process of step S10described above. In the removing process, the first insulating member42is pulled out in the +Y direction in the example ofFIG.8.

Although no illustration is given here, also when the first lead frame31has a third wiring part which projects parallel to the front surface of the first wiring part31afrom the first wiring part31a, similar effects may be achieved by providing a similar extension portion to the first insulating member42. In that case, the second portion40a2of the clamping part40aand the wiring gap part40bare configured to include extension portions to sandwich the third wiring part therebetween.

FIG.9is a plan view of a semiconductor module, illustrating a third modification of the first insulating member. InFIG.9, like reference numerals refer to identical components depicted inFIGS.2and7. Note thatFIG.9omits illustration of the second insulating member50depicted inFIG.2.

In a semiconductor module10bofFIG.9, an extension portion43aof a first insulating member43corresponds to the extension portion42aof the first insulating member42ofFIG.7. Note however that the extension portion43ais longer than the extension portion42aalong the third wiring part32d. Although no illustration is given here, the extension portion of the wiring gap part of the first insulating member43is also formed longer than the extension portion42bofFIG.8along the third wiring part32d, similarly to the extension portion42a.

Thus, appropriate choices may be made to the shapes of the first insulating members42and43according to the shape and the like of the third wiring part32d.

Note that the above-described first insulating members40to43may be used in combination with each other.

(b) Second Embodiment

Next described are a semiconductor module and a manufacturing method therefor according to a second embodiment, with reference toFIGS.10to13.

FIG.10is a plan view of a semiconductor module according to the second embodiment. InFIG.10, like reference numerals refer to identical components depicted inFIG.2.

In a semiconductor module60of the second embodiment, a first insulating member61has the following configuration, for example.

FIG.11is a cross-sectional view illustrating an example of the first insulating member of the second embodiment.FIG.11depicts the first insulating member61, the first wiring part31aof the first lead frame31, and the second wiring part32aof the second lead frame32in a cross-section taken along dashed-dotted line XI-XI ofFIG.10.

The first insulating member61includes the clamping part40asandwiching a part of an overlap region, in which the first wiring part31aand the second wiring part32aoverlap each other, from the rear surface of the first wiring part31aand the front surface of the second wiring part32a. The first insulating member61also includes the wiring gap part40bthat fills the gap between the first wiring part31aand the second wiring part32ain the part of the overlap region.

The clamping part40aincludes the first portion40a1in contact with the front surface of the second wiring part32aand the second portion40a2in contact with the rear surface of the first wiring part31a. The first insulating member61also includes a third portion61aconnecting the first portion40a1and a first end of the wiring gap part40band a fourth portion61bconnecting the second portion40a2and a second end of the wiring gap part40b, opposing the first end thereof.

In the above, the first insulating member61is described separately into multiple parts in order to explain the shape of the first insulating member61; however, the multiple parts may be manufactured in one piece. Regarding the size of the first insulating member61, there are no particular restrictions; however, it is preferable to have a size that does not interfere with structures below, such as bonding wires.

The above-described first insulating member61is formed before a process of manufacturing the case30by integral molding, as described later.

The first insulating member61is made of, for example, a thermoplastic resin. Examples of the thermoplastic resin include PPS, PPT, PBT, PBS, PA, and ABS.

Note that the first insulating member61may be provided in plurality.

(Method for Manufacturing Semiconductor Module60)

FIG.12is a flowchart illustrating an example of a method for manufacturing the semiconductor module according to the second embodiment.(Step S20) A preparing process is performed for preparing each component of the semiconductor module60. Parts and other materials are prepared for making the metal base11; the first insulating substrate21aand the second insulating substrate21bwith circuit patterns including, for example, the first conductive plate23aand the second conductive plate23b, respectively; the first semiconductor element22a; the second semiconductor element22b; and the case30. Parts for manufacturing the case30include, for example, the first lead frame31, the second lead frame32, the third lead frame33, the chassis34, and the control terminals35aand35b.(Step S21) A coupled part forming process is performed to form a coupled part in which the first lead frame31, the second lead frame32, the first insulating member61, and the second insulating member50are integrated into one piece. Such a coupled part may be formed by integral molding using a mold. According to the method for manufacturing the semiconductor module60of the second embodiment, the first insulating member61is attached to the first lead frame31and the second lead frame32in this process, unlike the method for manufacturing the semiconductor module10of the first embodiment. Therefore, the process of step S21may also be called attaching process.

The processes of steps S22and S23are the same as those of steps S3and S4ofFIG.5.(Step S24) A case fabricating process is performed. In the process of step S24, the case30is fabricated by integrally molding the first lead frame31, the second lead frame32, the third lead frame33, and the foregoing various terminals, such as the control terminals35aand35b, together with the frame-like chassis34. In the case fabricating process, the first lead frame31, the second lead frame32, the first insulating member61, and the second insulating member50are set in a mold as an integrally coupled part. This prevents the proper positional relationship between the chassis34, the first lead frame31, and the second lead frame32from being impaired due to heat history during the integral molding in the case fabricating process. Note that such an effect is achieved not only by the second insulating member50but also by the first insulating member61depicted inFIG.11, and the second insulating member50, therefore, does not need to be provided. Nevertheless, the use of the second insulating member50enhances the effect. Furthermore, the use of the second insulating member50allows the insulation distance to be increased.

The processes of steps S25to S27are the same as those of steps S7to S9ofFIG.5.

In the method for manufacturing the semiconductor module60according to the second embodiment, the first insulating member61is attached to the first lead frame31and the second lead frame32, not after, but before the case fabricating process, as described above. Note however that the first insulating member61depicted inFIG.11is movable in the wiring direction (the X direction) of the first lead frame31and the second lead frame32. Therefore, the position of the first insulating member61is adjustable in the X direction. This also offers improved flexibility in the installation of wiring members, such as bonding wires.

In the method for manufacturing the semiconductor module60according to the second embodiment, the first insulating member61having an S-shape when viewed in the +X direction in the example ofFIG.11fails to be removed from the first wiring part31aand the second wiring part32a. Therefore, the removing process of step S10depicted inFIG.5does not take place.

The processes of steps S28and S29are the same as those of steps S11and S12ofFIG.5.

The order of the steps above is just an example. For example, the process of step S21may come after that of step S22or S23.

In the method for manufacturing the semiconductor module60according to the second embodiment, the attaching process for the first insulating member61is performed before the joining process in which the first lead frame31and the second lead frame32are joined to the first conductive plate23aand the second conductive plate23b, respectively, as described above.

In the joining process, the first insulating member61is being attached to the first lead frame31and the second lead frame32, which prevents the first lead frame31from warping into a convex shape due to heat generated during joining and then coming into contact with the second lead frame32. The first insulating member61also prevents the second lead frame32from warping into a concave shape and then coming into contact with the first lead frame31. Furthermore, the first insulating member61being attached to the first lead frame31and the second lead frame32prevents the first lead frame31from warping into a concave shape. Herewith, it is possible to prevent the first lead frame31from strongly abutting against structures on the first insulating substrate21aand the second insulating substrate21b, which may result in problems with the installation of the case30onto the metal base11, the installation of terminals, and the like. This may reduce the loss of reliability of the semiconductor module60.

Also, in the semiconductor module60of the second embodiment, the first insulating members40to43depicted inFIGS.3and6to9may be attached to the first lead frame31and the second lead frame32. In that case, the first insulating members40to43may be attached to the first lead frame31and the second lead frame32between the processes of steps S24and S26.

When the first insulating members40,42, and43are used, these may be removed, for example, after the joining process of step S26.

The semiconductor module60of the second embodiment includes multiple insulating substrates, including the first insulating substrate21aand the second insulating substrate21b, similarly to the semiconductor module10of the first embodiment; however, the semiconductor module60may have only one insulting substrate.

Also, in the above example, the first lead frame31and the second lead frame32are joined to the first conductive plate23aand the second conductive plate23b, respectively; however, the applicable scope of the technology according to the second embodiment is not limited to this example. The first lead frame31is joined to the first circuit pattern on the metal base11while the second lead frame32is joined to the second circuit pattern on the metal base11. Different potentials are applied to the first lead frame31and the second lead frame32and, therefore, different potentials are applied to the first circuit pattern and the second circuit pattern. The first conductive plate23ais an example of the first circuit pattern, and the second conductive plate23bis an example of the second circuit pattern.

Furthermore, the first circuit pattern may be the main electrode on the front surface of the first semiconductor element22a, and the second circuit pattern may be the main electrode on the front surface of the second semiconductor element22b. In that case, each of these main electrodes is joined to the first lead frame31or the second lead frame32using, for example, a silver sintered material.

(Modification of First Insulating Member)

FIG.13is a cross-sectional view illustrating a modification of the first insulating member. InFIG.13, like reference numerals refer to identical components depicted inFIG.11.

The clamping part40aof a first insulating member62of the modification has barbs62aand62bat the tips of the lateral edges of the surfaces thereof which are respectively in contact with the front surface of the second wiring part32aand the rear surface of the first wiring part31a. The lateral edges run parallel to the wiring direction. The barbs62aand62bface the second wiring part32aand the first wiring part31a, respectively, from the tips. The foregoing first insulating member62may be installed in the attaching process of step S21ofFIG.12, in the same manner as the first insulating member61depicted inFIG.11.

Provision of the barbs62aand62bprevents the first insulating member62from shifting from the appropriate attachment area.

Having described aspects of the semiconductor module and manufacturing method therefor based on the embodiments above, they are merely examples and the particular details of these illustrative examples shall not be construed as limitations on the appended claims.

According to an aspect, it is possible to reduce the loss of reliability of a semiconductor module due to deformation of lead frames thereof.