Power module capable of prolonging cycle life

Abstract

The utility model belongs to the technical field of semiconductor bonding wire connection, and provides a power module capable of prolonging the cycle life, which mainly comprises a plastic shell and a copper-clad ceramic substrate, the copper-clad ceramic substrate is arranged in the plastic shell and comprises an upper copper layer, a ceramic layer and a lower copper layer, and the ceramic layer is provided with a first mounting surface and a second mounting surface which are arranged from top to bottom. The upper copper layer is arranged on the first mounting surface, the lower copper layer is arranged on the second mounting surface, and a chip is arranged on the upper copper layer; the metal bonding wire is fixedly arranged in the plastic shell, one end of the metal bonding wire is electrically connected with the chip and is provided with a first bonding point, the other end of the metal bonding wire is electrically connected with the adjacent upper copper layer and is provided with a second bonding point, and at the first bonding point, a first included angle is formed between the axis where the metal bonding wire is located and the horizontal plane where the chip is located. By setting the first included angle, the component force of the axial thermal stress of the metal bonding wire in the horizontal direction is small, and splitting or mutual separation of the metal bonding wire and the chip is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of semiconductor components, in particular to a power module with improved cycle life. Background Art

[0002] As a core component, power modules are widely used in industrial automation, new energy, electric vehicles and other fields. In vehicles, their main function is to achieve the conversion between DC and AC and complete the motor drive of electric vehicles. Among them, power cycle is an important life test item for power modules, and the number of times represents the service life of components. Therefore, improving the power cycle life of power modules will help extend the service life of electric vehicles.

[0003] During the test module power cycle (seconds), the chip will repeatedly switch on and off, generating high temperatures while constantly undergoing tiny deformations. The surface temperature will remain at 150-200°C. Therefore, the junction between the metal bonding wire and the metal area on the chip surface will be repeatedly stressed. The test often ends with the metal bonding wire and the bonding point on the chip surface falling off, or the root of the metal bonding wire breaking, resulting in the power module being unable to meet the high-intensity load requirements of current electric vehicles. Utility Model Content

[0004] The utility model provides a power module with improved cycle life, which solves the problem that the bonding points of metal bonding wires are repeatedly stressed and separated from the chip surface or broken due to repeated switching actions of the chip in the above background and continuous micro deformation while generating high temperature.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A power module with improved cycle life, comprising:

[0007] The plastic shell is provided with a first cavity;

[0008] A copper-clad ceramic substrate is arranged in the first cavity of the plastic shell, comprising an upper copper layer, a ceramic layer and a lower copper layer, wherein the ceramic layer is provided with a first mounting surface and a second mounting surface arranged from top to bottom, the upper copper layer is arranged on the first mounting surface, and the lower copper layer is arranged on the second mounting surface, wherein a chip is arranged on the upper copper layer;

[0009] A connecting terminal, one end of which is electrically connected to the upper copper layer, and the other end of which extends out of the first cavity of the plastic shell;

[0010] A metal bonding wire, one end of which is electrically connected to the chip and has a first bonding point, and the other end of which is electrically connected to the adjacent upper copper layer and has a second bonding point, wherein at the first bonding point, a first angle is provided between the axis of the metal bonding wire and the horizontal plane where the chip is located.

[0011] In some embodiments, the first angle ranges from 40° to 60°.

[0012] In some embodiments, the metal bonding wire is provided with a preset length so that a portion of the metal bonding wire away from the chip can form a transition section.

[0013] In some embodiments, at the second bonding point, a second angle is provided between the axis where the metal bonding wire is located and the plane where the upper copper layer is located.

[0014] In some embodiments, the second angle ranges from 40° to 60°.

[0015] In some embodiments, when the axis of the metal bonding wire forms a first angle with the plane where the chip is located and the axis of the metal bonding wire forms a second angle with the plane where the upper copper layer is located, the distance between the first bonding point and the second bonding point remains unchanged.

[0016] In some embodiments, a gel layer is further included in the first cavity, and the gel layer covers and fixes the metal bonding wire.

[0017] In some embodiments, a heat sink is further included, wherein a heat sink of the heat sink is connected to the plastic shell to form a first cavity, and the copper-clad ceramic substrate is disposed on the heat sink, wherein a plurality of heat sink columns are disposed on a side of the heat sink away from the copper-clad ceramic substrate, and preset gaps are disposed between the plurality of heat sink columns.

[0018] Compared with the prior art, the beneficial effects brought by the utility model are:

[0019] The present application sets a first angle between the axis of the metal bonding wire and the plane of the chip at the first bonding point, thereby reducing the horizontal component of the tension generated by the metal bonding wire when the chip is slightly deformed by heat, effectively preventing the metal bonding wire from detaching from the chip from the first bonding point or breaking between the chip, thereby improving the operating stability of the power module.

[0020] Additional aspects and advantages of the present application will be partially given in the following description, which will become apparent from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is a schematic diagram of a first state of a metal bonding wire of a power module for improving cycle life according to the utility model;

[0022] Figure 2 for Figure 1 The enlarged view of point A in the middle;

[0023] Figure 3 This is a schematic diagram of a second state of a metal bonding wire of a power module with improved cycle life according to the utility model;

[0024] Figure 4 Figure 3 The enlarged view of point B in the middle;

[0025] Figure 5 for Figure 3 Enlarged view of point C in the middle. DETAILED DESCRIPTION

[0026] The present application is further described in detail below in conjunction with specific drawings. In the description of this embodiment, unless otherwise specified, the terms "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the present application must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present application.

[0027] like Figure 1 and Figure 2 As shown, a power module with improved cycle life provided by the utility model mainly includes a plastic shell 1, which is provided with a first cavity; a copper-clad ceramic substrate 4, which is arranged in the first cavity of the plastic shell 1, and the copper-clad ceramic substrate 4 includes an upper copper layer 41, a ceramic layer 42, and a lower copper layer 43, and a first mounting surface and a second mounting surface are provided on the ceramic layer 42, and the first mounting surface and the second mounting surface are as shown in FIG. Figure 1The direction shown is arranged from top to bottom. In this embodiment, the ceramic layer 42 is a thin plate structure and has only two oppositely arranged first mounting surfaces and second mounting surfaces. The upper copper layer 41 is on the first mounting surface of the ceramic layer 42, and the lower copper layer 43 is arranged on the second mounting surface of the ceramic layer 42. A chip 411 is arranged on one of the upper copper layers 41. Specifically, the chip 411 is connected and fixed to the upper copper layer 41 by setting a lower connecting layer 412; a connecting terminal 3, one end of which is connected and fixed to the upper copper layer 41 and electrically connected, and the other end of which extends out of the first cavity of the plastic shell 1 to realize the transmission of electrical signals inside and outside the plastic shell 1; a metal bonding wire 7 is fixedly arranged in the first cavity of the plastic shell 1, one end of the metal bonding wire 7 is connected and fixed to the chip 411, and forms a first bonding point 71 with the chip 411, and the other end of the metal bonding wire 7 is connected and fixed to the adjacent upper copper layer 41, and forms a second bonding point 72 with the upper copper layer 41, and the chip 411 realizes internal electrical signal transmission through the metal bonding wire 7, wherein, at the first bonding point 71, the metal bonding wire 7 is provided with a first angle 8 between the axis and the horizontal plane where the chip 411 is located, as shown Figure 2 Specifically, the metal bonding wire 7 is installed and fixed extending upward from the first bonding point 71 to the side away from the chip 411. Since the thermal stress F generated by the micro-deformation of the chip 411 due to heat is in the axial direction of the metal bonding wire 7, the thermal stress F will generate a horizontal component force Fx and a vertical component force Fy. Among them, the horizontal component force Fx will have a greater impact on the cracking and life of the first bonding point 71, and is a more important factor than the vertical component force Fy. It can be seen from the test results that the horizontal component force Fx is more likely to generate transverse cracks along the first bonding point 71, and the vertical component force Fy is more difficult to generate cracks in the first bonding point 71. Therefore, when the first angle 8 is larger, as shown in FIG. Figure 2 As shown in FIG. 1 , the smaller the horizontal force component Fx is, the smaller the horizontal pulling force received by the first bonding point 71 is, so the connection strength between the metal bonding wire 7 and the chip 411 at the first bonding point 71 can be improved, and the metal bonding wire 7 and the first bonding point 71 of the chip 411 are prevented from being broken or separated. Figure 4 As shown, when the first angle 8 is smaller, the horizontal component force Fx is larger, that is, the first bonding point 71 receives a larger horizontal pulling force. Therefore, the metal bonding wire 71 is easy to separate from the chip 411 or the first bonding point 71 is easy to break.

[0028] Furthermore, the range of the first angle 8 is 40°-60°. For power modules with different arc heights, PC second-level life tests were carried out (same product, same test conditions). When the first angle 8 is 20°, 15,000 cycles can be tested. When the first angle 8 is 35 degrees, 20,000 cycles can be tested. When the first angle 8 is 40 degrees, 30,000 cycles can be tested. When the first angle 8 is 60 degrees, 30,000 cycles can be tested. When the first angle 8 is greater than 60 degrees, the bonding process is more difficult, which is not conducive to the bonding of the first bonding point 71. Therefore, in summary, the preferred range of the first angle 8 is 40-60°, at which time the bonding process is less difficult and the number of cycle tests is the largest.

[0029] In one embodiment, in order to meet the requirement of the first angle 8 of the metal bonding wire 7, the metal bonding wire 7 is set with a preset length so that the portion of the metal bonding wire 7 away from the chip 411 can form a transition section, thereby realizing that the metal bonding wire 7 can form a first angle 8 with a larger angle at the first bonding point 71. Specifically, a transition section is set at the portion of the metal bonding wire 7 away from the chip 411, such as Figure 1 As shown, it is an arc portion, which on the one hand meets the requirement of the first angle 8, and on the other hand realizes the connection between the metal bonding wire 7 and the adjacent upper copper layer 41.

[0030] In one embodiment, at the second bonding point 72, as Figure 3 and Figure 5 As shown, a second angle 9 is provided between the axis of the metal bonding wire 7 and the plane of the upper copper layer 41. The force condition at the second bonding point 72 is the same as the force condition at the first bonding point 71, so no further elaboration is made here. Further, the second angle 9 is in the range of 40° to 60°, which can effectively increase the connection strength of the metal bonding wire 7 at the second bonding point 72. It is the same as the principle of the aforementioned measurement data, so no further elaboration is made here.

[0031] In one embodiment, in order to facilitate the formation of the first angle 8 and the second angle 9 and fix these angles, when the axis of the metal bonding wire 7 forms the first angle 8 with the plane where the chip 411 is located and the axis of the metal bonding wire 7 forms the second angle 9 with the plane where the upper copper layer 41 is located, the distance between the first bonding point 71 and the second bonding point 72 remains unchanged, thereby avoiding positional offset of the first bonding point 71 and the second bonding point 72, resulting in the first angle 8 and the second angle 9 not reaching the preset angle.

[0032] Furthermore, in order to facilitate electrical insulation inside the power module and further fix the metal bonding wire 7 at a preset angle, a gel layer 2 is provided in the first cavity of the plastic shell 1, wherein the gel layer 2 covers and insulates the metal bonding wire 1 and fixes it. At the same time, the gel layer 2 also insulates and covers other components of the power module, such as the chip 411 or the upper copper layer 41. The gel layer 2 completely fills the first cavity. In this embodiment, the gel layer 2 is silicone gel, and its material can also be epoxy resin or other materials.

[0033] In one embodiment, in order to facilitate timely discharge of the heat of the chip 411, so as to reduce the temperature environment of the chip 411, thereby further reducing the generation of thermal stress, a heat sink is further included, and the heat sink is fixedly connected to the plastic shell 1, wherein the heat sink is connected to the plastic shell 1 through a heat sink 5 to form a first cavity, a first connection layer 431 is arranged on the lower copper layer 43 of the copper-clad ceramic substrate 4, and the copper-clad ceramic substrate 43 is arranged on the heat sink 5 through the first connection layer 431, and a plurality of heat dissipation columns 6 are arranged on the side of the heat sink 5 away from the copper-clad ceramic substrate 4, and gaps are arranged between the plurality of heat dissipation columns 6 for the flow of cooling material, and by arranging the heat dissipation columns 6, the contact area between the cooling material and the heat sink 5 is increased, thereby effectively improving the heat dissipation efficiency. The cooling material can be a coolant or water at a relatively low temperature.

[0034] The above is only a preferred embodiment of the present invention. It should be noted that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A power module with improved cycle life, characterized in that: include: The plastic shell is provided with a first cavity; A copper-clad ceramic substrate is arranged in the first cavity of the plastic shell, comprising an upper copper layer, a ceramic layer and a lower copper layer, wherein the ceramic layer is provided with a first mounting surface and a second mounting surface arranged from top to bottom, the upper copper layer is arranged on the first mounting surface, and the lower copper layer is arranged on the second mounting surface, wherein a chip is arranged on the upper copper layer; A connecting terminal, one end of which is electrically connected to the upper copper layer, and the other end of which extends out of the first cavity of the plastic shell; A metal bonding wire is fixedly disposed in the first cavity, one end of the metal bonding wire is electrically connected to the chip and is provided with a first bonding point, the other end of the metal bonding wire is electrically connected to the adjacent upper copper layer and is provided with a second bonding point, wherein at the first bonding point, a first angle is provided between the axis of the metal bonding wire and the horizontal plane where the chip is located.

2. A power module with improved cycle life according to claim 1, characterized in that: The first angle ranges from 40° to 60°.

3. A power module with improved cycle life according to claim 1, characterized in that: The metal bonding wire is provided with a preset length so that a portion of the metal bonding wire away from the chip can form a transition section.

4. A power module with improved cycle life according to claim 3, characterized in that: At the second bonding point, a second angle is provided between the axis where the metal bonding wire is located and the plane where the upper copper layer is located.

5. A power module with improved cycle life according to claim 4, characterized in that: The second angle ranges from 40° to 60°.

6. A power module with improved cycle life according to claim 4, characterized in that: When the axis of the metal bonding wire forms a first angle with the plane where the chip is located and the axis of the metal bonding wire forms a second angle with the plane where the upper copper layer is located, the distance between the first bonding point and the second bonding point remains unchanged.

7. A power module with improved cycle life according to any one of claims 1 to 6, characterized in that: It also includes a gel layer disposed in the first cavity, and the gel layer covers and fixes the metal bonding wire.

8. A power module with improved cycle life according to claim 7, characterized in that: It also includes a radiator, a heat sink of which is connected to the plastic shell to form a first cavity, and the copper-clad ceramic substrate is arranged on the heat sink, wherein a side of the heat sink away from the copper-clad ceramic substrate is provided with a plurality of heat sink columns, and preset gaps are provided between the plurality of heat sink columns.

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