Novel power module packaging structure

Abstract

The utility model belongs to the field of semiconductor chip packaging modules, and provides a novel power module packaging structure, which comprises a plastic shell, a copper-clad ceramic substrate, a chip, an upper copper layer, a ceramic layer and a lower copper layer, and the chip is arranged on the ceramic layer. One end of the power terminal is arranged on the upper copper layer, the other end of the power terminal extends out of the plastic shell, the metal bonding wire is arranged in the plastic shell, one end of the metal bonding wire and the chip are provided with a first connecting point, the other end of the metal bonding wire and the upper copper layer are provided with a second connecting point, a first packaging layer is arranged at the first connecting point and the second connecting point, and a second packaging layer wrapping the first packaging layer is arranged in the plastic shell. The thermal expansion coefficient of the first packaging layer is smaller than that of the second packaging layer. The two ends of the metal bonding wire are secondarily packaged and fixed by setting the first packaging layer and the second packaging layer with different thermal expansion coefficients and elastic moduli, so that the phenomenon that metal at the first connecting point and the second connecting point jumps up and is separated from contact or metal fatigue fracture failure occurs is avoided.

Description

Technical Field

[0001] The utility model belongs to the field of semiconductor chip packaging modules, in particular to a new power module packaging structure. Background Art

[0002] With the widespread popularity of semiconductor power devices, the requirements for the reliability and stability of power devices are gradually increasing. Among them, ensuring that the chip is in a suitable operating temperature range is the key to ensuring the normal operation of power devices.

[0003] The power module is tested for power cycling according to the requirements of AQG 324. As the voltage and power levels of the power module increase, the chip junction temperature of the power module increases from 150°C to 200°C, or even higher. The connection between the metal bonding wire and the source metal area on the chip becomes the bottleneck for improving the overall fatigue life of the power module;

[0004] The common power module packaging types on the market, such as EP, HPD, and HPI, have a small elastic modulus of potting glue, usually less than 1MPa, which makes it difficult to protect the metal near the bonding point. In power cycle tests, since the metal bonding wires are repeatedly pulled by thermal stress, the bonding points often jump out of contact or metal fatigue fractures, causing abnormal electrical connections of the power module, thereby reducing the reliability of the power module. Utility Model Content

[0005] The utility model provides a novel power module packaging structure, which solves the problem that the metal near the bonding position may jump out of contact or metal fatigue fracture during the power cycle test or normal operation of the module in the above background, resulting in abnormal electrical connection of the power module, thereby improving the reliability of the power module.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A new power module packaging structure, comprising:

[0008] The plastic shell has a first cavity,

[0009] A copper-clad ceramic substrate is disposed in the first cavity of the plastic shell, the copper-clad ceramic substrate comprises an upper copper layer, a ceramic layer and a lower copper layer, the ceramic layer is provided with a first mounting surface and a second mounting surface, the upper copper layer is disposed on the first mounting surface of the ceramic layer, and the lower copper layer is disposed on the second mounting surface of the ceramic layer;

[0010] A chip is provided with a lower connection layer, and the chip is arranged on the first mounting surface of the ceramic layer through the lower connection layer;

[0011] A power terminal, one end of which is disposed on the upper copper layer, and the other end of which extends out of the plastic shell to the outside, and the power terminal is electrically connected to the upper copper layer;

[0012] A metal bonding wire is arranged in the first cavity of the plastic shell, one end of the metal bonding wire and the chip are provided with a first connection point, and the metal bonding wire and the upper copper layer are provided with a second connection point, wherein a first packaging layer is provided at the first connection point and the second connection point, the first packaging layer covers and fixes the first connection point and the second connection point, a second packaging layer is provided in the first cavity of the plastic shell, the second packaging layer covers the first packaging layer, the thermal expansion coefficient of the first packaging layer is smaller than the thermal expansion coefficient of the second packaging layer, and the elastic modulus of the first packaging layer is greater than that of the second packaging layer.

[0013] In some embodiments, the first encapsulation layer is formed by solidifying liquid epoxy resin, and the second encapsulation layer is formed by solidifying liquid silicone.

[0014] In some embodiments, the second packaging layer is adapted to the shape of the first cavity, and the second packaging layer abuts against the inner wall of the first cavity of the plastic shell.

[0015] In some embodiments, the first packaging layer encapsulates and fixes the chip.

[0016] In some embodiments, a first thickness is provided between the chip and a side of the first packaging layer disposed at the first connection point away from the upper copper layer, and a second thickness is provided between the upper copper layer and a side of the first packaging layer disposed at the upper copper layer away from the upper copper layer.

[0017] In some embodiments, a heat sink is disposed on one side of the lower copper layer, and a first connection layer is disposed between the heat sink and the lower copper layer, and the first connection layer fixes the heat sink to the lower copper layer.

[0018] In some embodiments, a plurality of heat dissipation columns are disposed on a side of the heat sink away from the lower copper layer, and preset gaps are provided between the plurality of heat dissipation columns.

[0019] In some embodiments, the heat sink is connected to the plastic shell to form a first cavity of the plastic shell.

[0020] Compared with the prior art, the beneficial effects brought by the utility model are as follows:

[0021] The present application performs two times of glue filling to set up a first packaging layer and a second packaging layer, and the thermal expansion coefficient of the first packaging layer is much smaller than that of the second packaging layer, and the elastic modulus of the first packaging layer is greater than that of the second packaging layer. Therefore, when performing a cycle test on the power module, the first packaging layer can apply a downward pressure to the first connection point and the second connection point of the metal bonding wire to reduce the equivalent stress of the metal. At the same time, combined with the set second packaging layer, the first packaging layer is coated to reduce the influence of the first packaging layer on the edge of the ceramic layer, thereby improving its fatigue life and avoiding delamination of the first packaging layer from other components and fracture of the ceramic layer.

[0022] 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

[0023] Figure 1 This is a cross-sectional view of the internal structure of a novel power module packaging structure of the utility model;

[0024] Figure 2 A top view of the first state of the internal connection structure of a novel power module packaging structure of the utility model;

[0025] Figure 3 A top view of the first state of the internal connection structure of a novel power module packaging structure of the utility model;

[0026] Figure 4 The utility model is a schematic diagram of a packaging process of a novel power module packaging structure. DETAILED DESCRIPTION

[0027] 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.

[0028] like Figure 1As shown, a new type of power module packaging structure provided by the utility model mainly includes a plastic shell 400, which is provided with a first cavity; a copper-clad ceramic substrate, which is arranged in the first cavity of the plastic shell 400, and the copper-clad ceramic substrate includes an upper copper layer 101, a ceramic layer 102 and a lower copper layer 103, and the ceramic layer 102 is provided with a first mounting surface and a second mounting surface, the upper copper layer 101 is arranged on the first mounting surface of the ceramic layer 102, and the lower copper layer 103 is arranged on the second mounting surface of the ceramic layer 102; a chip 200, which is provided with a lower connecting layer 201, and the chip 200 is arranged on the first mounting surface of the ceramic layer 102 through the lower connecting layer 201; a power terminal 1011, one end of which is fixedly arranged on the upper copper layer 101, and is electrically connected to the upper copper layer 101, and the other end of which extends out of the plastic shell 400 to electrically connect the inside and outside of the plastic shell 400; a metal The bonding wire 104 is arranged in the first cavity of the plastic shell 400. One end of the metal bonding wire 104 is fixedly connected to the chip 200 and is provided with a first connection point 1013. The other end of the metal bonding wire 104 is fixedly connected to the upper copper layer 101, and a second connection point 1014 is provided therebetween. It should be particularly noted that a first packaging layer 1012 is provided at the first connection point 1013 and the second connection point 1014, respectively, and the first packaging layer 1012 covers and fixes the first connection point 1013 and the second connection point 1014. Furthermore, a second packaging layer 1015 is provided in the first cavity of the plastic shell 400, and the second packaging layer 1015 covers the first packaging layer 1012, and the thermal expansion coefficient of the first packaging layer 1012 is smaller than the thermal expansion coefficient of the second packaging layer 1015.

[0029] In the present application, a first packaging layer 1012 and a second packaging layer 1015 with different thermal expansion coefficients are used for sealing and fixing, and the thermal expansion coefficient of the first packaging layer 1012 is much smaller than that of the second packaging layer 1015. Therefore, when the power module is cycle tested or working, the harder liquid first packaging layer 1012 can provide a compressive stress to the metal bonding wire 104 at the first connection point 1013 and the second connection point 1014 to reduce the equivalent stress of the metal, thereby improving its fatigue life. Structural simulation experiments have found that the maximum equivalent stress of the metal bonding wire 104 at the first connection point 1013 and the second connection point 1014 can be reduced by 15%, and after evaluation by the corresponding life model, its fatigue life can be improved by more than 60%.

[0030] Optionally, in this embodiment, the first packaging layer 1012 with greater strength may be selected as the material of the second packaging layer 1015 for packaging, which may also improve its fatigue life.

[0031] Further, the first encapsulation layer 1012 is formed by solidifying liquid epoxy resin, and the second encapsulation layer 1015 is formed by solidifying liquid silicone. In this embodiment, the first encapsulation layer 1012 is formed by using epoxy resin. After the liquid epoxy resin encapsulation material is solidified, its elastic modulus is 0.1-20.0GPa, and its thermal expansion coefficient is 5.0-20.0ppm. The thermal expansion coefficient is usually between the chip 200 and the metal bonding wire 104, and is much smaller than the conventional silicone gel, thereby providing downward compressive stress to the metal bonding wire 104 at the first connection point 1013 and the second connection point 1014. By using silicone gel to make the second encapsulation layer 1015, it is not easy to have a risk of delamination between the silicone gel and the copper-clad ceramic substrate and the plastic shell 400, and the range of the ceramic layer 102 of the copper-clad ceramic substrate generally exceeds the upper copper layer 101 and the lower copper layer 103. The modulus of silicone gel is relatively small, and the difference in thermal expansion coefficient with the ceramic layer 102 is small, so it is not easy to cause the edge of the ceramic layer 102 to break. In addition, since epoxy resin packaging is expensive, using a gel material for the second packaging layer 1015 can also save costs.

[0032] In one embodiment, the second packaging layer 1015 is adapted to the shape of the first cavity. The second packaging layer 1015 not only seals and fixes the first packaging layer 1012, but also fills the entire first cavity, that is, the second packaging layer 1015 abuts against the inner wall of the first cavity of the plastic shell 400, further improving the sealing stability of the first packaging layer 1012.

[0033] In one embodiment, the first packaging layer 1012 encapsulates the chip 200. Figure 2 As shown, the first packaging layer 1012 covers and fixes the metal bonding wire 104 at the first connection point 1013 and the second connection point 1014. Further, in this embodiment, as shown in FIG. Figure 3 As shown, the first packaging layer 1012 covers and fixes the chip 200. While sealing and fixing one end of the metal bonding wire 104, it can also further seal and protect the chip 200 to protect the chip 200 from external mechanical damage. The combination of the first packaging layer 1012 and the second packaging layer 1015 can provide a pressure on the chip 200 to prevent the connection points of the chip 200 from being broken due to heat.

[0034] In one embodiment, in order to ensure the fixing effect of the first encapsulation layer 1012 on the two ends of the metal bonding wire 104, the first encapsulation layer 1012 is set with a first thickness between the side away from the upper copper layer 101 and the chip 200 at the first connection point 1013, and the first encapsulation layer 1012 is set with a second thickness between the side away from the upper copper layer 101 and the upper copper layer 101 at the second connection point 1014. By setting the first thickness and the second thickness, it is ensured that the two ends of the metal bonding wire 104 are fully covered and fixed by the first encapsulation layer 1012, and the fixing strength of the first encapsulation layer 1012 is strengthened, so as to ensure that the metal bonding wire 104 is not cracked at the first connection point 1013 and the second connection point 1014 due to the high temperature of the chip 200, thereby causing the failure of the electrical signal transmission of the chip 200. In this embodiment, the first thickness and the second thickness can be the same or different, depending on the actual connection conditions of the first connection point 1013 and the second connection point 1014.

[0035] In one embodiment, in order to ensure that the heat generated by the chip 200 during operation is discharged to prevent the high temperature from affecting the first connection point 1013 and the second connection point 1014, refer again to Figure 1 , a heat sink 300 is arranged on one side of the lower copper layer 103, and a first connection layer 1031 is arranged between the heat sink 300 and the lower copper layer 103 to fix and support the heat sink 300 and the lower copper layer 103. Furthermore, a plurality of heat dissipation columns 301 are arranged on the side of the heat sink 300 away from the lower copper layer 103, and a preset gap is arranged between the plurality of heat dissipation columns 301. By setting the preset gap, liquid cooling water can pass through, while increasing the contact area between the heat sink 300 and the cooling water flow and improving the heat dissipation efficiency, the cooling water flow can take away the heat generated by the chip 200 in time through the heat dissipation columns 301, so as to prevent the chip 200 from generating excessively high temperature and affecting the first connection point 1013 and the second connection point 1014.

[0036] In one embodiment, the heat sink 300 is fixedly connected to the plastic shell 400, and in this embodiment, the heat sink 300 is fixedly connected to the plastic shell 400 by means of clamping and bolts, so as to form a sealed first cavity with the plastic shell 400. When the second packaging layer 1015 is formed, no external tools are required.

[0037] In one embodiment, Figure 4As shown, it is a schematic diagram of the packaging process of a power module provided by the utility model, firstly, the chip 200 is sintered / welded, then the copper-clad ceramic substrate is sintered, the plastic shell 400 is assembled, and then the power terminal 1011 is ultrasonically bonded and fixed, and then the metal bonding wire 104 is bonded, and then the first packaging layer 1012 is potted, and after the first packaging layer 1012 is strengthened and cured, the second packaging layer 1015 is potted, and after the second packaging layer 1015 is cured, the cover plate is assembled, and finally the factory test is performed.

[0038] 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 new power module packaging structure, characterized in that: include: The plastic shell has a first cavity; A copper-clad ceramic substrate is disposed in the first cavity of the plastic shell, the copper-clad ceramic substrate comprises an upper copper layer, a ceramic layer and a lower copper layer, the ceramic layer is provided with a first mounting surface and a second mounting surface, the upper copper layer is disposed on the first mounting surface of the ceramic layer, and the lower copper layer is disposed on the second mounting surface of the ceramic layer; A chip is provided with a lower connection layer, and the chip is arranged on the first mounting surface of the ceramic layer through the lower connection layer; A power terminal, one end of which is disposed on the upper copper layer, and the other end of which extends out of the plastic shell to the outside, and the power terminal is electrically connected to the upper copper layer; A metal bonding wire is arranged in the first cavity of the plastic shell, one end of the metal bonding wire and the chip are provided with a first connection point, and the metal bonding wire and the upper copper layer are provided with a second connection point, wherein a first packaging layer is provided at the first connection point and the second connection point, the first packaging layer covers and fixes the first connection point and the second connection point, a second packaging layer is provided in the first cavity of the plastic shell, the second packaging layer covers the first packaging layer, the thermal expansion coefficient of the first packaging layer is smaller than that of the second packaging layer, and the elastic modulus of the first packaging layer is greater than that of the second packaging layer.

2. A novel power module packaging structure according to claim 1, characterized in that: The first encapsulation layer is formed by solidifying liquid epoxy resin, and the second encapsulation layer is formed by solidifying liquid silicone gel.

3. The novel power module packaging structure according to claim 1, characterized in that: The second packaging layer is adapted to the shape of the first cavity, and the second packaging layer abuts against the inner wall of the first cavity of the plastic shell.

4. A new power module packaging structure according to claim 3, characterized in that: The first packaging layer covers and fixes the chip.

5. The novel power module packaging structure according to claim 1, characterized in that: A first thickness is provided between the chip and the side of the first packaging layer disposed at the first connection point away from the upper copper layer, and a second thickness is provided between the side of the first packaging layer disposed at the upper copper layer away from the upper copper layer.

6. A novel power module packaging structure according to any one of claims 1 to 5, characterized in that: A heat sink is provided on one side of the lower copper layer, and a first connection layer is provided between the heat sink and the lower copper layer. The first connection layer fixes the heat sink on the lower copper layer.

7. A novel power module packaging structure according to claim 6, characterized in that: A plurality of heat dissipation columns are arranged on a side of the heat sink away from the lower copper layer, and preset gaps are arranged between the plurality of heat dissipation columns.

8. The novel power module packaging structure according to claim 6, characterized in that: The heat sink is connected to the plastic shell to form a first cavity of the plastic shell.

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