阅读说明：本技术 具有激光焊接的引线框的功率半导体模块 (Power semiconductor module with laser-welded lead frame ) 是由 N·帕利克 F.莫恩 M·图特 S·柯尼格 于 2020-03-12 设计创作，主要内容包括：一种功率半导体模块(10)包括具有结构化金属化层(22)的衬底(12)；利用第一功率电极(38)结合到金属化层(22)的半导体芯片(14)；引线框(16,18),该引线框被激光焊接到所述半导体芯片(14)的组(36a,36b)的第二电极(40),用于电互连半导体芯片(14)；控制导体(52),该控制导体(52)附接到与半导体芯片(14)相对的引线框(16,18)并且与引线框(16,18)电隔离。控制导体(52)电连接到组(36a,36b)中的半导体芯片(14)的控制电极(58)。(A power semiconductor module (10) includes a substrate (12) having a structured metallization layer (22); a semiconductor chip (14) bonded to the metallization layer (22) with a first power electrode (38); a lead frame (16, 18) laser welded to the second electrodes (40) of the groups (36a, 36b) of semiconductor chips (14) for electrically interconnecting the semiconductor chips (14); a control conductor (52), the control conductor (52) being attached to the lead frame (16, 18) opposite the semiconductor chip (14) and being electrically isolated from the lead frame (16, 18). The control conductors (52) are electrically connected to the control electrodes (58) of the semiconductor chips (14) in the groups (36a, 36 b).)

1. A power semiconductor module (10) comprising:

a substrate (12) having a structured metallization layer (22);

a semiconductor chip (14) bonded to the metallization layer (22) with a first power electrode (38);

a lead frame (16, 18), the lead frame (16, 18) being laser welded to the second electrodes (40) of the groups (36a, 36b) of semiconductor chips (14) for electrically interconnecting the semiconductor chips (14);

a control conductor (52), the control conductor (52) being attached to the lead frame (16, 18) opposite the semiconductor chip (14) and being electrically isolated from the lead frame (16, 18);

wherein the control conductor (52) is electrically connected to control electrodes (58) of the semiconductor chips (14) in the group (36a, 36b), and the control conductor (52) is laser welded to at least one of the control electrodes (58).

2. The power semiconductor module (10) of claim 1, further comprising:

a flexible circuit board (44, 46), the flexible circuit board (44, 46) attached to the lead frame (16, 18);

wherein the control conductor (52) is at least partially provided by a metal layer (50) of the flexible circuit board (44, 46).

3. The power semiconductor module (10) according to claim 1 or 2, further comprising:

an electrically insulated lead (94), the electrically insulated lead (94) attached to the leadframe (16, 18);

wherein the control conductor (52) is at least partially provided by a metal core of the electrically insulated lead (94).

4. The power semiconductor module (10) according to any one of the preceding claims, further comprising:

a control substrate (90), the control substrate (90) having an electrically insulating layer (50) attached to the lead frame (16, 18);

wherein the control conductor (52) is at least partially provided by a metallization layer (50) of the control substrate (90).

5. Power semiconductor module (10) according to one of the preceding claims,

wherein the control conductor (52) is connected with at least one of the control electrodes (58) via a wire bond (56).

6. Power semiconductor module (10) according to one of the preceding claims,

wherein the control conductor (52) is part of a control substrate (90) or a flexible circuit board (44, 46), the control conductor (52) protruding from the lead frame (16, 18) at the control electrode (58).

7. The power semiconductor module (10) of claim 6 wherein the control conductor (52) is electrically connected to at least one of the control electrodes (58) by a via.

8. Power semiconductor module (10) according to one of the preceding claims,

wherein a gate conductor (52) and an auxiliary conductor (54) are attached to the lead frames (16, 18) opposite the group of semiconductor chips (14) and electrically isolated from the lead frames (16, 18);

wherein two strips of said auxiliary conductor (54) are provided on both sides of the gate conductor (52).

9. Power semiconductor module (10) according to one of the preceding claims,

wherein a second power electrode (40) of the semiconductor chip (10) to which the lead frames (16, 18) are laser welded comprises a metal buffer plate (42) bonded to the semiconductor chip (14);

wherein the lead frames (16, 18) are laser welded to the buffer plate (42).

10. Power semiconductor module (10) according to one of the preceding claims,

wherein the lead frame (16, 18) provides power terminals (68, 68 ') of the power semiconductor module (10), the power terminals (68, 68') protruding from a housing (88) of the power semiconductor module (10).

11. The power semiconductor module (10) according to claim 10,

wherein a control terminal (30 ') protrudes from the housing (88) at the same level as the lead frames (16, 18), the control terminal (30') being made of the same material as the lead frames (16, 18) and in the same thickness as the lead frames (16, 18);

wherein the control terminal (30') is electrically interconnected with the control conductor (52) inside the housing (88).

12. Power semiconductor module (10) according to one of the preceding claims,

wherein the semiconductor chips (14) are arranged in at least one row (34a-34 d);

wherein the leadframe (16, 18) comprises a central portion (66) running along the row and branch portions (70), the branch portions (70) protruding from the central portion (66) over the rows (34a-34d) of the semiconductor chips (14).

13. The power semiconductor module (10) according to claim 12,

wherein the branch portion (70) is bent toward the semiconductor chip (14).

14. Power semiconductor module (10) according to one of the preceding claims,

wherein the power semiconductor module (10) forms a half bridge and a first group (36a) of the semiconductor chips (14) are electrically connected in parallel with their power electrodes (38, 40) to form a low-side switch and a second group (36b) of the semiconductor switches (14) are electrically connected in parallel with their power electrodes (38, 40) to form a high-side switch;

wherein the first lead frame (16) is laser welded to the second electrodes (40) of the first group (36a) of semiconductor chips (14);

wherein a second lead frame (18) is laser welded to a second electrode (40) of the second group (36b) of semiconductor chips (14).

15. The power semiconductor module (10) of claim 14,

wherein the first group (36a) of semiconductor chips (14) is arranged in a row (34a, 34b) along a centre line of the power semiconductor module (10);

wherein the second group (36b) of semiconductor chips (14) is arranged in two rows (34c, 34d) outside the first group (36a) at both sides of the first group (36 a);

wherein the first lead frame (16) is arranged between a substrate (12) of the power semiconductor module (10) and the second lead frame (18).

Technical Field

The present invention relates to a power semiconductor module.

Background

Semiconductor chips (such as IGBTs, MOSFETs, diodes, etc.) commonly used in power semiconductor modules are vertical devices. Current flows vertically from the top side source/emitter contact to the bottom side drain/collector contact. The entire area of the bottom side of the chip is bonded (e.g., soldered or sintered) to a metal layer (e.g., the top metallization layer of the ceramic substrate). Topside connections are typically made by a large number of thick wire bonds.

Recent developments have focused on replacing Si devices with wide bandgap devices made of SiC or GaN, because of the beneficial properties in minimizing switching losses and/or increasing switching frequency. In addition, current density is increased and less chip area is available to accommodate the number of wire bonds required for a given current.

Wire bonding techniques may reach their limits in terms of current capability. This has triggered a transition from Al to Cu leads to ensure reliable bonding. Nevertheless, the ever increasing current density of new power semiconductor switches may require superior topside connections.

In addition, the large number of thick bonding wires may limit the manufacturing yield of each wire bonding machine equipment and may cause significant wear of the wire bonding tool. Furthermore, the reliability of power semiconductor modules with a large number of wire bonds may be limited, since wire bond failures (such as delamination, heel-off, etc.) belong to the main failure mechanisms.

US 2018090338 a1 describes a power semiconductor module having a leadframe soldered to a stress buffer layer bonded to a chip.

US 2014/217600 a1 relates to the manufacture of semiconductor modules having several semiconductor chips bonded to a heating body.

DE 102012222791 a1 shows a semiconductor module with a contact element which is laser welded to a power semiconductor chip by means of a sintering layer.

JP 2013105789 a shows a semiconductor module having electrical contact elements bonded to two semiconductor chips, and a flexible circuit board attached to the electrical contact elements.

Disclosure of Invention

It is an object of the present invention to provide a power semiconductor module with a high current density which is reliably and easily and quickly manufactured.

This object is achieved by the subject matter of the independent claims. Further exemplary embodiments are apparent from the dependent claims and the following description.

The present invention relates to a power semiconductor module. The power semiconductor module may be an assembly including power semiconductor chips, their electrical interconnects, terminals and mechanical structures supporting all of these components. The power semiconductor module may include a housing and a terminal protruding from the housing. For example, the above-mentioned parts may be enclosed in a housing made of a polymer material.

The term "power" herein and hereinafter may refer to modules, chips and/or devices adapted to handle voltages greater than 100V (e.g., greater than 100V), and/or greater than 1A (e.g., greater than 10A).

The power semiconductor chip may be and/or may provide one or more semiconductor devices, such as transistors, thyristors and/or diodes, in particular IGBTs, IGCTs and/or MOSFETs. Some or all of the power semiconductor chips may be power semiconductor switches. The power semiconductor chip may be made of Si and/or of a wide bandgap material, such as SiC, GaN, etc.

According to an embodiment of the invention, a power semiconductor module includes a substrate having a structured metallization layer and a plurality of semiconductor chips bonded to the metallization layer with a first power electrode. The substrate may comprise an isolation layer, for example made of ceramic, and a metallization layer, which may be made of a metal such as Cu. The metallization layer may be structured, i.e. divided into regions that are electrically disconnected (but may be electrically connected by further conductors) on the isolation layer.

The semiconductor chip may be sintered and/or soldered to the metallization layer. A first power electrode (such as a drain, source, collector or emitter) may cover the entire side of the semiconductor chip facing the metallization layer.

According to an embodiment of the invention, the power semiconductor module comprises a lead frame which is laser-welded to the second electrode of the semiconductor chip group for electrically interconnecting the semiconductor chips. The lead frame may be a metal plate, for example made of Al, Cu, etc. and/or made of sheet metal. A second power electrode (such as a drain, source, collector or emitter) and a control electrode (such as a gate) may cover the entire side of the semiconductor chip opposite the metallization layer. The lead frame may cover only the second power electrode. It can be laser-welded to the second power electrode with a laser beam directed at the side of the lead frame facing away from the power semiconductor chip. The laser welds may be circular, linear and/or spot shaped and/or combinations thereof.

The group of semiconductor chips may be parallel to their power electrodes via the metallization layers of the substrate and the lead frame.

It has to be noted that the power semiconductor module may comprise more than one laser welded lead frame. One or more leadframes may be used as top side source and/or emitter connections. A single leadframe may connect all parallel semiconductor chips.

According to an embodiment of the invention, the power semiconductor module comprises a control conductor attached to the lead frame opposite the semiconductor chip and electrically isolated from the lead frame, wherein the control conductor is electrically connected to the control electrodes in the group of semiconductor chips and the control conductor is laser welded to at least one of the control electrodes. The control conductor may direct a control signal, such as a gate signal, to the power semiconductor chip. The control conductors may include one or more metallization layers and/or one or more leads that are electrically insulated from the leadframe. For example, an electrically insulating material is provided between the control conductors and the lead frame.

When the control conductor, for example in the form of a metal layer or substrate of a flexible circuit board, is guided over the control electrode, it can be laser welded to the control electrode.

It has to be noted that the control conductor may also be used for routing other auxiliary signals, such as auxiliary source connections, and/or signals from the sensor. Signal connections in the form of one or more control conductors may be routed in additional layers on top of the leadframe.

One or more lead frames may enable a power module with high reliability and low cost. One or more lead frames may be precisely placed on a semiconductor chip on a power module substrate and soldered by a focused laser beam. Lead frame based top side connections can replace a large number of thick wire bonds. Such a lead frame may also serve directly as a power terminal.

In addition, since the substrate area can be reduced, the footprint of a fully assembled power semiconductor module (including a molded package or housing) can be reduced by about half its size. Additionally, this may result in cost savings for molding the plastic or housing.

The number of manufacturing steps may be reduced, since, for example, the bonding of the top substrate to the main substrate, subsequent cleaning steps and at least some terminal bonding may be omitted. The reliability of the power semiconductor module can be increased because the main failure source of the wire bonding can be mitigated. Finally, there may be additional design freedom and/or improved electrical characteristics achieved by multiple layers of coplanar current routing (e.g., by stacking lead frames).

According to an embodiment of the invention, the power semiconductor module further comprises a flexible circuit board attached to the lead frame, wherein the control conductors are at least partly provided by a metal layer of the flexible circuit board. The flexible circuit board may include a flexible isolation layer and a metal layer. The flexible circuit and/or the pre-fabricated circuit may be bonded (such as laminated, glued, soldered, etc.) to the lead frame. It may be fully bonded or bonded at discrete points on the lead frame. The at least one metal layer may provide a conductive track, which may serve as one or more control conductors.

According to an embodiment of the invention, the power semiconductor module further comprises an electrically insulated lead attached to the leadframe, wherein the control conductor is at least partially provided by a metal core of the electrically insulated lead. In addition to or as an alternative to a flexible circuit board, one or more insulated leads may be attached (such as glued) to the lead frame. One or more of the insulated leads may have a coaxial design, that is, a conductive hose may be provided within the spacer for shielding the center lead for routing control signals.

According to an embodiment of the invention, the power semiconductor module further comprises a control substrate having an electrically insulating layer attached to the leadframe, wherein the control conductor is at least partially provided by a metallization layer of the control substrate. In addition to or instead of the flexible circuit board and/or one or more insulated leads, the control substrate may be bonded (such as glued, soldered, etc.) to the lead frame. The control substrate may be a ceramic substrate (such as a direct copper clad DBC and/or an active metal support AMB) and/or an insulated metal substrate IMS.

According to an embodiment of the invention, the control conductor is connected to at least one of the control electrodes via a wire bond. One or more wire bonds may be used. Wire bonding can compensate for different levels of control conductors on the top side of the gate electrode and over the lead frame.

According to an embodiment of the invention, the control conductor is part of a control substrate or flexible circuit board, which protrudes from the lead frame at the at least one control electrode. It is possible that the control conductor may be guided over the control electrode such that it may be directly connected to the control electrode.

According to an embodiment of the present invention, the control conductor may be electrically connected with at least one of the control electrodes using a via hole. The control conductor may be bonded (such as soldered or sintered) to the control electrode.

According to an embodiment of the present invention, the gate conductor and the auxiliary conductor are attached to the lead frame opposite to the semiconductor chip and are electrically isolated from the lead frame. Two control conductors in the form of a gate conductor and an auxiliary conductor may be provided on the lead frame. The auxiliary conductor may be an auxiliary source connection.

According to an embodiment of the invention, two strips of auxiliary conductors are provided on both sides of the gate conductor. In this way, a coaxial arrangement of the gate conductor and the auxiliary conductor can be achieved to minimize the gate loop inductance.

According to an embodiment of the present invention, the second power electrode of the semiconductor chip to which the lead frame laser is soldered includes a metal buffer plate bonded to the semiconductor chip. The buffer plate may be made of Cu or other weldable metal. The buffer plate may be bonded (such as soldered or sintered) to the active area of the semiconductor chip. The lead frame may be laser welded to the buffer plate.

The buffer plate may facilitate laser welding without damaging the active area of the semiconductor chip, since the active area metallization of the semiconductor chip may be too thin to accommodate stable laser welding. Generally, one or more conductive buffer plates may be bonded to the top surface of the chip to enable laser welding on the source pad or the emitter pad.

The control electrode may also comprise such a metal buffer plate. Wire bonds may be attached to the buffer plate. The control conductor may be laser welded to the buffer plate.

According to an embodiment of the present invention, the metal buffer plate includes two layers of different metal materials, such as Mo and Cu. A stack of multiple buffer plates of different materials may be used (such as a Mo plate on a semiconductor chip and a Cu plate on top of the Mo plate) to provide a solderable surface.

According to an embodiment of the invention, the lead frame provides a power terminal of the power semiconductor module, which protrudes from a housing of the power semiconductor module. It is possible that parts of the lead frame may be used as external terminals. The housing may be a molded package, and a portion of the lead frame may protrude from the molded package.

According to an embodiment of the present invention, the control terminal protrudes from the housing at the same level as the lead frame. The control terminal is made of the same material and with the same thickness as the lead frame. The control terminals may be made from the same leadframe preform as the leadframe interconnecting the semiconductor chips. The control terminals and the lead frame may be interconnected outside the housing during manufacturing, wherein the interconnection is removed after the housing is provided.

According to an embodiment of the invention, the control terminal is electrically interconnected with a control conductor inside the housing. This may be done by wire bonding and/or via laser welding the control conductors to the control terminals.

In general, one or more additional terminals may be linked to the leadframe, with the links removed (such as cut and/or trimmed) in subsequent production steps.

According to an embodiment of the present invention, the semiconductor chips are arranged in at least one row, wherein the lead frame comprises a central portion running along the row and branch portions protruding from the central portion on the semiconductor chips of the row. The parallel-connected semiconductor chips, which may form individual switches of the power semiconductor module, may be arranged in one or more rows. The leadframe may include a longitudinal central portion that may run between rows of semiconductor chips to be connected. Each branch portion may travel from the central portion to a location on a respective semiconductor chip. In general, the lead frame may be tree-shaped.

The control conductors may be arranged on the central part and the branch parts and/or may also be tree-shaped.

According to the embodiment of the present invention, the branch portion is bent toward the semiconductor chip. The central portion of the lead frame may be at a higher level than the ends of the branch portions. The central portion may be further from the substrate than the ends of the branch portions.

According to an embodiment of the invention, the lead frame comprises a peripheral portion attached to the ends of the branch portions and running parallel to the central portion. Such a leadframe may interconnect rows of semiconductor chips, which are further away from each other than in the case of a tree-shaped leadframe. It can be seen that such a lead frame has a grid-like form. The peripheral portion may direct current coaxial with the central portion toward the terminal. In this case, the control conductor may be provided on the peripheral portion. The central portion may be further from the substrate than the peripheral portion.

According to an embodiment of the invention, the power semiconductor modules form a half-bridge, and the first group of semiconductor chips are electrically connected in parallel with their power electrodes to form a low-side switch, and the second group of semiconductor switches are electrically connected in parallel with their power electrodes to form a high-side switch. Each of the first and second groups may be arranged in two rows of semiconductor chips, which may be interconnected using a tree-shaped lead frame and/or a grid-shaped lead frame.

The first lead frame may be laser-welded to the second electrodes of the first group of semiconductor chips, and the second lead frame may be laser-welded to the second electrodes of the second group of semiconductor chips.

According to an embodiment of the present invention, the semiconductor chips of the first group are arranged in a row along a center line of the power semiconductor module, and the semiconductor chips of the second group are arranged in two rows outside the first group at both sides of the first group. The first lead frame, which may be tree-shaped, may be arranged between the substrate of the power semiconductor module and the second lead frame, which may be grid-shaped.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

Drawings

The subject matter of the invention will be explained in more detail below with reference to exemplary embodiments shown in the drawings.

Fig. 1 shows a perspective view of a power semiconductor module.

Fig. 2 shows a side view of the power semiconductor module of fig. 1.

Fig. 3 shows a cross-sectional view of the power semiconductor module of fig. 1.

Fig. 4 shows a tree-shaped lead frame of the power semiconductor module of fig. 1.

Fig. 5 shows a grid-shaped lead frame of the power semiconductor module of fig. 1.

Fig. 6 shows a partial cross-section of a power semiconductor module according to an embodiment of the invention.

Fig. 7 shows a partial top view of the power semiconductor module.

The reference symbols used in the drawings and their meanings are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference numerals in the figures.

Detailed Description

Fig. 1 shows a perspective view of a power semiconductor module 10, which includes a substrate 12, a semiconductor chip 14 bonded to the substrate 12, and two lead frames 16, 18 electrically interconnecting the semiconductor chip 14 on a top side of the semiconductor chip 14.

The semiconductor module is also shown in fig. 2 and 3 in a side view and a sectional view. It can be seen that the substrate 12 includes an insulating layer 20 and two metallization layers 22, 24 on either side of the insulating layer 20. The insulating layer 20 may be made of ceramic. The metallization layers 22, 24 may be made of Cu.

As shown in fig. 1, the metallization layer 22 on the top side (i.e. the side facing the semiconductor chip 14) is structured, i.e. divided into several disconnected regions 26, 28, 30. The region 26 is a DC + region, and the region 28 is an AC region. The regions 30a, 30b, 30c, 30d may serve as an auxiliary source, a low side gate, a high side auxiliary source, and a high side gate. Portion 32 of region 26 may serve as a high-side auxiliary drain. The region 30e may serve as a terminal for a temperature sensor.

The semiconductor chip 14 is bonded to respective regions 26, 28 of the metallization layer 22 and connected by the lead frames 16, 18 to form a half bridge. The semiconductor chips 14 are arranged in four parallel rows 34a, 34b, 34c, 34 d. The rows 34a, 34b form a first group 36a of parallel-connected semiconductor chips 14, which provides the low-side switches of the half-bridge. The rows 34c, 34d form a first group 36a of parallel-connected semiconductor chips 14, which provides the high-side switches of the half-bridge.

Semiconductor chip 14 is provided with a first power electrode 38 on its bottom side and a second power electrode 40 on its top side.

The bottom side power electrodes 38 of the chips 14 of the rows 34c, 34d are connected to the DC + region 26, which is at a DC + potential during operation of the module 10. The top side power electrodes 40 of the chips 14 of the rows 34c, 34d are connected to the lead frame 18, which is also connected to the AC area 28. During operation of the module 10, the lead frame 18 and the AC region 28 are at an AC potential. The bottom side power electrodes 38 of the chips 14 of the rows 34a, 34b are connected to the AC region 28. The top side power electrodes 40 of the chips 14 of the rows 34a, 34a are connected to the lead frame 16, which is at a DC-potential during operation of the module 10.

The lead frames 16, 18, which may be made of sheet metal and/or Cu, are laser welded to the top side electrode 40. As shown in fig. 3, the top side electrode 40 may include a buffer plate 42 bonded to the active area of the semiconductor chip 14. The lead frames 16, 18 may then be soldered to a buffer plate 42, which may be made of metal (such as CU and/or Mo).

As shown in fig. 1, a flexible circuit board 44, 46 is attached to the top side of each of the leadframes 16, 18. Each of the flexible circuit boards 44, 46 includes an insulating base layer 48 attached to the respective lead frame 16, 18 and a conductive layer 50 on top of the base layer 48 (see fig. 3). The base layer 48 may be made of a flexible plastic material and/or foil. The conductive layer 50, which may be made of Cu, is divided into disconnected regions, each of which provides a control conductor 52, 54 for the module 10.

As also shown in fig. 4 and 5, an inner region 52 of layer 50 provides a gate conductor 52. The inner region/gate conductor 52 is used for gate signal distribution. An outer region 54 surrounding the inner region 52 provides a conductor 54 for an auxiliary source potential. To minimize gate loop inductance, inner region 52 is guided between two traces and/or strips of outer region 52. It is also possible that only one area, such as area 52 or area 54, is used for conducting the control signal.

Returning to fig. 1, the gate conductors 52 may be connected via wire bonds 56 with respective control electrodes 58 of respective power semiconductor chips 14. Additional wire bonds 60 may be used to connect the gate conductor 52 to the terminal regions 30c, 30b, respectively.

The auxiliary conductor 54 may be connected to the power electrode 40 of the respective power semiconductor chip 14 via a wire bond 62. Additional wire bonds 64 may be used to connect the auxiliary conductors 54 to the terminal areas 30d, 30a, respectively.

The size of the gate conductor 52 and/or the auxiliary conductor 54 may be adjusted as desired (e.g., whether a per-chip gate resistor is desired). The areas of the lead frames 16, 18 to be laser welded to the power semiconductor chip 14 may be free of the flexible circuit boards 44, 46.

Fig. 4 shows the tree leadframe 16 in more detail. The leadframe 16 has a longitudinal central portion 66 that runs along the center of the module 10 between the two inner rows 34a, 34b of semiconductor chips 14. At one end, a power terminal 68 is connected to the central portion 66, which is also made of the material of the lead frame 16. At the other end, the central portion 66 is kinked so that the flexible circuit board 44 at the top thereof is directed toward the terminal area 30b (see fig. 1). The semiconductor module 10 may have a molded package, and only a portion of the terminals 68 may protrude from the package.

The lead frame 16 also includes a branch portion 70 that branches substantially orthogonally from the central portion 66. The ends of the branch portions 70 are aligned over the power semiconductor chips 14 of the inner row 34. In addition, the branch portions 70 are bent toward the semiconductor chip 14 such that the central portion 66 is at a higher level than the ends of the branch portions 70.

The flexible circuit board 44 on the lead frame 16 travels along the center portion and the branch portions 70, and is also tree-shaped.

Fig. 5 shows the grid-shaped lead frame 18 in more detail. Like lead frame 16, lead frame 18 has a central portion 66, power terminals 68' and branch portions 70. When the lead frame 18 is in the module 10, the power terminals 68' are disposed on an opposite side of the module 10 relative to the power terminals 68 of the lead frame 16.

The lead frame 18 also provides an AC area connection 72, which AC area connection 72 is connected to the branch portion 70 and bends downward toward the AC area 28. The lead frame 18 may be laser welded to the AC area 28 via an AC area connection 72.

The lead frame 18 additionally has two longitudinal peripheral portions 74 running parallel to the central portion 66 and connected to the branch portions 70. The peripheral portion 74 is at a lower level than the central portion 66. The peripheral portion 74 is positioned on top of the outer rows 34c, 34d of semiconductor chips 14. The lead frame 18 is soldered with the power semiconductor chip 14 via the peripheral portion 74.

The flexible circuit board 46 on the lead frame 16 also travels along the peripheral portion 74 and the branch portion 70 in addition to the power terminals 68'. The flexible circuit board 46 is U-shaped.

The power semiconductor module 10 can be manufactured as follows.

In a first step, the semiconductor chip 14 may be bonded to the substrate 12. In this step, the buffer plate 42 may also be bonded to the semiconductor chip 14.

In a second step, the first lead frame 16 may be laser welded to a first group 36a of semiconductor chips in the rows 34a, 34 b. Thereafter, the gate conductors 52 may be wire bonded to respective gate/control electrodes 58. Also, the auxiliary source conductors 54 may be wire-bonded to the respective second electrodes 40.

In a third step, the second lead frame 16 may be laser welded to the second group 36b of semiconductor chips in the rows 34c, 34 d. The first lead frame 16 is then sandwiched between the substrate 12 and the second lead frame 18. The gate conductor 52 of the second leadframe 18 may be wire bonded to a respective gate/control electrode 58. Also, the auxiliary source conductor 54 of the second lead frame 18 may be wire-bonded to the corresponding second electrode 40.

Alternative manufacturing sequences are possible depending on the specific layout of the lead frames 16, 18. For example, it is possible that two laser welding steps and two wire bonding steps may be combined separately when the second leadframe 18 is designed such that the top sides of the first group 36a of semiconductor chips 14 remain accessible.

Fig. 6 shows a partial cross section of the power semiconductor module 10, wherein the buffer plate 42 has more than one layer 76, 78. The layers 76, 78 may be metal layers of different materials, such as Mo and Cu.

The power semiconductor chip 14 may include an active electrode region 80 on a semiconductor substrate, to which active electrode region 80 a first layer 76, such as a Mo layer, is bonded (e.g., brazed or sintered). A second layer 78, such as a Cu layer, is bonded to the first layer 76 and/or the leadframes 16, 18 are laser welded to the second layer 78. Fig. 6 shows a laser weld 82 that travels through the leadframes 16, 18 and the second layer 78. It is possible that the laser welding 82 stops before the first layer 76.

Fig. 6 shows a further embodiment of how the flexible circuit boards 44, 46 may be electrically connected to the semiconductor chip 14. The flexible circuit boards 44, 46 protrude and/or extend from the edges of the lead frames 16, 16. The flexible circuit boards 44, 46 may be positioned on the gate/control electrodes 58 and the gate/control conductors 52 may be bonded directly to the gate/control electrodes 58, such as by welding, laser welding, soldering, or the like. It is possible that the flexible circuit boards 44, 46 have vias between the gate/control conductors 52 and the gate/control electrodes 58.

It must be noted that the electrical connection of the auxiliary conductor 54 to the electrode 40 can also be made in this way.

It is possible to bond a further buffer plate 42 ' to the active region 80 ' of the gate/control electrode 58, which buffer plate 42 ' may also have two layers 76 ', 78 ', which may be made as layers of the buffer plate 42.

Fig. 7 shows a partial top view of the power semiconductor module 10, wherein several terminals 68 ', 30' are made from the same leadframe preform 84. The lead frame 18 may be connected via a bridge 86 to a terminal 30 ', which terminal 30' may be a gate terminal. After attachment to the module 10, the lead frame 18 and the terminals 30' may be disconnected by removing the bridge 86. In particular, the module 10 may include a molded housing 88 indicated by dashed lines. The lead frame 18 and the terminals 30' may be partially molded into a housing 88, which may be a molded package.

The same concept can be applied to other types of terminals, to lead frames 16 combined with other types of terminals, and/or to both lead frames 16, 18, that is, the lead frames 16, 18 can be combined in one preform 84, can be attached together to the module 10, and can be broken by removing the bridge 86 after molding the housing.

Fig. 7 also shows that the control conductors 52 may be provided by a control substrate 90 having an electrically insulating layer 92 attached to the lead frame 18. The control conductor 52 may be provided by a metallization layer 50 on a control substrate 90, which may be a DBC, AMD or IMS substrate.

The control conductors 52 may also be provided by isolated wires or leads 94, which wires or leads 94 may be attached over the lead frame 18 and/or may run thereover. This cable or lead 94 may be a coaxial cable.

It has to be noted that the control conductor 54 may also be provided as such an isolating cable or lead 94, and/or the control conductor 54 may be provided as a metallization layer 50 on the control substrate 90.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

List of reference numerals

10 power semiconductor module

12 substrate

14 semiconductor chip

16 first lead frame

18 second lead frame

20 insulating layer

22 metallization layer

24 metallization layer

26DC + region

28AC region

30, 30' terminal region

30a low side auxiliary source region

30b low side gate region

30c high side auxiliary source region

30d high side gate region

30e temperature sensor area

32 high side auxiliary drain portion

34a first row

34b second row

34c third row

34d fourth line

36a first group

36b second group

38 first power electrode

40 second power electrode

42, 42' buffer plate

44 first flexible circuit board

46 second flexible circuit board

48 insulating base layer

50 conductive layer

52 gate/control conductor

54 auxiliary/source/control conductor

56 wire bonding

58 control electrode

60 wire bonding

62 wire bonding

64 wire bonding

66 center portion

68, 68' power terminal

70 center part

72 AC area connection

74 peripheral portion

76, 76' first layer

78, 78' second layer

80 active electrode area

82 laser welding

84 leadframe preform

86 bridge

88 casing

90 control substrate

92 electrically insulating layer

94 isolated cables or leads