Performance module

Abstract

Power module comprising: • a relay substrate (4) with a first conduction layer (4a) present on a front side and a second conduction layer (4c) present on a rear side; • copper blocks (6) present in holes penetrating the relay substrate (4) in a thickness direction and connecting the first conduction layer (4a) to the second conduction layer (4c); • semiconductor devices (1a, 1b), each semiconductor device (1a, 1b) having a main electrode (11) present at a position opposite an end face of the associated copper block (6), and only one copper block (6) being electrically connected to a main electrode (11); • an insulating substrate (3) connected to the rear sides of the semiconductor devices (1a, 1b) via a connecting material (2); and• a sealing agent (9) that seals the relay substrate (4), the copper blocks (6) and the semiconductor elements (1a, 1b);wherein• an external connection (7b, 7c) of the power module is directly connected to one of the copper blocks (6) instead of to the first conductor layer (4a) of the relay substrate (4); and wherein• part of the external connection (7b, 7c) is covered with the sealing compound (9).;

Description

Background of the invention Area The present invention relates to a structure of a power module. background In recent years, there has been a demand for small power modules in the fields of vehicles, industrial machinery, and consumer devices. A technique has been proposed that enables miniaturization using a relay substrate in which the conduction layers have a multilayer structure instead of a single-layer structure. For example, patent literature 1 (JP 2013-21371A) discloses a structure for causing current to flow using a relay substrate, making it possible to provide a power module that is smaller than one with a single-layer structure. From DE 10 2016 203 581 A1, a semiconductor device is known which comprises: a plurality of semiconductor units, each comprising a laminated substrate formed by laminating an insulating plate and a circuit board, and a semiconductor element joined to the circuit board by using an adhesive material that undergoes an irreversible phase transition to a solid-state state. The semiconductor device also comprises a base plate to which each of the plurality of semiconductor units is joined by using solder, and a connection unit that electrically connects the plurality of semiconductor units in parallel. From DE 11 2013 001 425 T5, a conductive pin is known which is contacted with a contacting target element, such as a semiconductor chip or an insulating substrate with conductive patterns, using metal nanoparticles. A lower surface of the distal end of the conductive pin is formed in a concave shape. Another semiconductor device is known from JP 2015 - 198 216 A. Summary However, in a semiconductor arrangement disclosed in patent literature 1, semiconductor elements are each connected to a plurality of conductive pins, and the plurality of conductive pins is each connected to through-holes. If a shared flux ratio varies due to fluctuations in the contact resistance between the semiconductor elements and the plurality of conductive pins, and between the plurality of conductive pins and the through-holes, a fluctuation occurs in the magnitude of the current flowing through the conductive pins, and the current-carrying capacity of the conductive pins through which a maximum current flows becomes insufficient, causing a problem in which the magnitude of the overall current is limited. The present invention was made to solve the above-mentioned problem, and one object of the present invention is to provide a power module that prevents the occurrence of fluctuations in the strength of a current flowing through each conductive pin due to a deviation in a shared flux ratio. This problem is solved by the features of the independent claims. The dependent claims disclose preferred embodiments of the invention. According to aspects of the present invention, a power module comprises: a relay substrate with a first conduction layer present on a front side and a second conduction layer present on a rear side; copper blocks present in holes penetrating the relay substrate in a thickness direction and connecting the first conduction layer to the second conduction layer; semiconductor elements, each semiconductor element having a main electrode present at a position opposite an end face of the associated copper block, and only one copper block being electrically connected to a main electrode; an insulating substrate connected to the rear sides of the semiconductor elements via connecting materials; and a filler or sealant, hereinafter referred to as a sealant, which seals the relay substrate, the copper blocks, and the semiconductor elements. The power module according to aspects of the present invention has a structure in which each semiconductor element and the relay substrate are connected via a single copper block. This structure offers the advantageous effect of preventing fluctuations in the current flowing through each copper block due to variations in the shared flux ratio. Other and further tasks, features and advantages of the invention will become clearer from the following description. Brief description of drawings Fig. 1 is a sectional view showing the power module according to a first example. Fig. 2 is a sectional view showing the power module, wherein each copper block is soldered to the relay substrate. Fig. 3 is a sectional view showing the power module, wherein the external terminals are connected to the copper blocks according to the invention. Fig. 4 is a sectional view showing the power module according to a second example. Fig. 5 is a sectional view showing the power module, wherein the semiconductor elements have different thicknesses. Fig. 6 is a sectional view showing the power module according to a third example. Fig. 7 is a sectional view showing the power module, wherein each copper block is exposed to the outside of the sealing medium. Fig. 8 is a sectional view showing the power module, wherein the exposed part of each copper block has a terminal form.Figure 9 is a cross-sectional view showing the power module according to a fourth example. Description of examples First example A power module according to a first example is described. Fig. 1 is a sectional view showing the power module according to the first example. It should be noted that in the figures different from Fig. 1, the same reference numerals denote the same or corresponding parts. A power module 100 has a structure in which semiconductor elements 1 (1a, 1b) are connected to the front of an insulating substrate 3 via a solder 2, and a relay substrate 4 is arranged above the front of the insulating substrate 3 and electrically connected to the semiconductor elements 1 via copper blocks 6. In the power module shown in Fig. 1, the semiconductor elements 1 are IGBTs, each serving as a switching element, and are connected via solder 2 to the front face of a circuit structure 3c. MOSFETs, diodes, or the like, other than IGBTs, can be used as the semiconductor elements. The insulating substrate 3 comprises a base plate 3a, an insulating layer 3b, and a circuit structure 3c. The base plate 3a and the circuit structure 3c are each made of, for example, copper. The insulating layer 3b can be made of, for example, an inorganic ceramic material or a material in which a ceramic powder is dispersed in a thermosetting plastic, such as an epoxy resin. A back electrode of each semiconductor element 1, which is a collector electrode if the semiconductor element is an IGBT, is connected to the insulating substrate 3 via solder, thus ensuring electrical insulation on the outside of the power module 100. The relay substrate 4 comprises an insulating plate 4b, a front-side conduction layer 4a, which is a first conduction layer formed on the front of the insulating plate 4b, and a back-side conduction layer 4c, which is a second conduction layer formed on the back of the insulating plate 4b. For example, both surfaces of the insulating plate, which are formed from a glass-epoxy substrate, are provided with a conductive element having a thickness of 0.2 mm or greater. It should be noted that the relay substrate 4 can be modified in various ways, as long as three-dimensional wiring is implemented. For example, the degrees of freedom of the wiring can be increased by using conductors in the relay substrate that have three or more layers.In this case, two or more insulating plates are manufactured, and each of the insulating plates is placed between conductors, forming the relay substrate, which consists of conductors having three or more layers. The relay substrate 4 has a hole that penetrates the substrate in its thickness direction. A connecting element 20, which connects the conduction layers formed on the two surfaces of the insulating plate 4b, is formed in the hole. The connecting element 20 is not particularly restricted as long as it electrically connects the conduction layers formed on the two surfaces of the insulating plate 4b. For example, the connecting element 20 is a copper cladding layer. Each copper block 6 is connected to the connecting element 20 by pressure welding, thus ensuring a conduction area between the semiconductor elements 1 and the relay substrate 4. A main electrode 11 of each semiconductor element 1 is located opposite an end face of the associated copper block 6.The main electrode 11 of each semiconductor element 1 and the back side of the associated copper block 6 are electrically connected via solder. In this case, only one copper block 6 is electrically connected to the main electrode 11. That is, the copper blocks and the main electrodes are connected in a one-to-one correspondence. It should be noted that, as shown in Fig. 2, the part to which each copper block 6 is connected by pressure welding and the connecting part 20 are soldered to firmly connect each copper block 6 to the relay substrate 4, thereby improving the current-carrying effect. An external connection 7a is electrically connected to the circuit structure 3c and is used to exchange an electrical signal with an external device. It should be noted that the external connection 7a may be molded into a housing 8. Furthermore, the external connection 7a may be configured to penetrate the relay substrate. In this case, at least one through-hole, through which an external electrode passes, may be provided at a predetermined position on the relay substrate. External terminals 7b and 7c are electrically connected to the front-side conduction layer 4a of the relay substrate 4 and are used to exchange an electrical signal with an external device. Fig. 1 shows that the external terminals 7b and 7c have an L-shape; however, the external terminals 7b and 7c can also have a cylindrical shape. As shown in Fig. 3, according to the invention, the external terminals 7b and 7c can be connected to the copper block 6 instead of being connected to the front-side conduction layer 4a of the relay substrate 4. The insulating substrate 3, the semiconductor elements 1, and the relay substrate 4 are enclosed within the housing 8. The housing 8 is made of a plastic or similar material. A sealant 9 is filled into the housing 8. The sealant 9 is not particularly restricted as long as it is a material with insulating properties. For example, an epoxy resin is used. The copper blocks, the relay substrate 4, and the semiconductor elements 1 are surrounded by the sealant 9. Part of the external connection is covered by the sealant 9, while part of the connection extends to the outside of the sealant 9 to exchange signals with an external device. Furthermore, the back of the insulating substrate 3 is exposed by the sealant 9 and is cooled by a heat sink (not shown). With reference to Fig. 1, a circuit configuration is described in which the semiconductor elements are IGBTs. Semiconductor element 1a and semiconductor element 1b are connected in series, and diodes (not shown) are connected in parallel to each semiconductor element, forming an inverter circuit. The external terminal 7a serves as a P-terminal, which is a main terminal of the power module, and is electrically connected to the collector electrode, which is a back-side electrode of semiconductor element 1a. An emitter electrode, which is a front-side electrode (main electrode 11) of semiconductor element 1a, is connected to the external terminal 7b via a single copper block. The external terminal 7b serves as an output terminal. The external terminal 7b is electrically connected to the collector electrode of semiconductor element 1b.The emitter electrode of semiconductor element 1b is connected to the external terminal 7c via a single copper block. External terminal 7c serves as an N-terminal, which is a main terminal of the power module. Naturally, circuit configurations other than the one described above can be used. The power module according to the first example has a structure in which each semiconductor element and the relay substrate are connected to a single main electrode via a single copper block. This structure offers the advantage of preventing fluctuations in the current flowing through each copper block due to variations in the shared flux ratio. When using multiple copper blocks instead of a single one, a fixed spacing between them becomes necessary. However, using a single copper block eliminates this need and offers the advantage of miniaturizing the power module.Furthermore, each semiconductor element and the relay substrate are connected to a single main electrode via a single copper block, thus eliminating the need to specify a distance between copper blocks, unlike when using multiple copper blocks. This design offers the advantage of allowing elements with high heat capacity to be connected and improving heat dissipation within a transition period. Second example A power module according to a second example is described. Fig. 4 is a sectional view showing the power module according to the second example. In the power module according to the second example, the back side of each copper block 6 is arranged to extend beneath the back side of the relay substrate 4. The power module according to the second example has a design in which the back of each copper block 6 is positioned so that it extends beneath the back of the relay substrate 4. This design offers the advantage of allowing adjustment of the solder thickness used to connect the copper block 6 and the semiconductor elements 1. As shown in Fig. 5, even if the semiconductor elements 1 have different thicknesses, the solder thickness can be optimized while preventing the relay substrate from tilting by adjusting the height of each copper block 6. Third example A power module according to a third example is described. Fig. 6 is a sectional view showing the power module according to the third example. In the power module according to the third example, the front face of each copper block 6 is arranged such that it projects beyond the front face of the relay substrate 4, and the front face of each copper block 6 is exposed by the sealing medium 9 according to the invention. In the power module according to the third example, the front face of each copper block 6 is arranged such that it projects beyond the front face of the relay substrate 4, and the front face of each copper block 6 is exposed by the sealing medium 9, thus making it possible to heat each copper block 6 from the exposed portion. This design offers the advantage of enabling soldering between the copper blocks 6 and the semiconductor elements 1 from the outside of the power module. As shown in the comparative example in Fig. 7, each copper block 6 exposed to the outside of the sealing medium 9 can be used as an external electrode. As shown in Fig. 8, the exposed portion of each copper block also has a terminal shape, which allows each copper block to be connected to an external component. Fourth example A power module according to a fourth example is described. Fig. 9 is a sectional view showing the power module according to the fourth example. The power module according to the fourth example has a recess formed on the back side of each copper block 6. In the power module according to the fourth example, the back of each copper block 6 has a recess, which has the advantageous effect of allowing the solder used to connect the copper blocks 6 and the semiconductor elements 1 to protrude. Fig. 9 shows that the recess is trapezoidal. However, the recess can be rectangular, square, triangular, or semicircular. A variety of recesses can be formed. Furthermore, the means for joining the components is not limited to solder, and any conductive joining material can be used. Preferably, the conductive joining material is a metal with low electrical resistance, such as solder, a metallic paste using a metal filler, or a sintered metal that has been metallized by heat.

Claims

Power module comprising: • a relay substrate (4) with a first conduction layer (4a) present on a front side and a second conduction layer (4c) present on a rear side; • copper blocks (6) present in holes penetrating the relay substrate (4) in a thickness direction and connecting the first conduction layer (4a) to the second conduction layer (4c); • semiconductor devices (1a, 1b), each semiconductor device (1a, 1b) having a main electrode (11) present at a position opposite an end face of the associated copper block (6), and only one copper block (6) being electrically connected to a main electrode (11); • an insulating substrate (3) connected to the rear sides of the semiconductor devices (1a, 1b) via a connecting material (2); and• a sealing agent (9) that seals the relay substrate (4), the copper blocks (6) and the semiconductor elements (1a, 1b);wherein• an external connection (7b, 7c) of the power module is directly connected to one of the copper blocks (6) instead of to the first conductor layer (4a) of the relay substrate (4); and wherein• part of the external connection (7b, 7c) is covered with the sealing material (9).; Power module comprising: • a relay substrate (4) with a first conduction layer (4a) present on a front side and a second conduction layer (4c) present on a rear side; • copper blocks (6) present in holes penetrating the relay substrate (4) in a thickness direction and connecting the first conduction layer (4a) to the second conduction layer (4c); • semiconductor devices (1a, 1b), each semiconductor device (1a, 1b) having a main electrode (11) present at a position opposite an end face of the associated copper block (6), and only one copper block (6) being electrically connected to a main electrode (11); • an insulating substrate (3) connected to the rear sides of the semiconductor devices (1a, 1b) via a connecting material (2); • a sealing material (9) connecting the relay substrate (4), the copper blocks (6), and the semiconductor devices (1a, 1b) 1b) seals;and• in addition to the copper blocks (6), a first external connection (7b), which serves as an output connection of the power module, and a second external connection (7c), which serves as a main connection of the power module; wherein• an end part of the copper block (6) is exposed by the sealing medium (9); and• the first external connection (7b) and the second external connection (7c) are connected to the first conductor layer (4a) of the relay substrate (4).; Power module according to claim 1 or according to claim 2, wherein the second conduction layer (4c) is opposite the semiconductor element (1a, 1b), and the end face of the copper block (6) opposite the main electrode (11) projects from the second conduction layer (4c). Power module according to one of the preceding claims, wherein the end surface of the copper block (6) opposite the main electrode (11) has a recess.

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