Aluminum strip connecting structure for high-reliability power module

Abstract

The utility model discloses an aluminum strip connecting structure for a high-reliability power module, which belongs to the technical field of power module packaging, and comprises a DBC (Direct Bonding Copper) substrate, the DBC substrate comprises a ceramic layer and a copper layer, and the copper layer is positioned above the ceramic layer; the chip is arranged on the DBC substrate, is a core component of the power module and is used for realizing a specific electrical function; the chip sintering silver welding layer is positioned between the chip and the DBC substrate and is formed by sintering nano-silver soldering paste at a low temperature; one end of the aluminum strip is connected with the upper portion of the chip, the other end of the aluminum strip is connected with the copper layer of the DBC substrate, the aluminum strip sintered silver soldering layer is located between the aluminum strip and the copper layer of the DBC substrate, and the aluminum strip sintered silver soldering layer is formed through the nano-silver soldering paste low-temperature sintering technology and used for converting direct connection of the aluminum strip, the chip and the DBC substrate into connection of the aluminum strip and the sintered silver soldering layer. Therefore, the thermal mechanical stress at the connection point is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to power module packaging field, specifically, relate to a kind of aluminium tape connection structure for high-reliability power module. BACKGROUND

[0002] Power module is the module that power electronic components are formed with certain function integrated circuit by electrical interconnection and then filled.

[0003] Its structure as Figure 2 Shown, mainly includes: substrate 101, interconnection layer 102, chip 103 and bonding tape 104, chip 103 lower side is connected with substrate 101 by interconnection layer 102, the material of interconnection layer is silver sintered by nano silver solder paste, chip 103 upper side is connected with substrate 101 by bonding tape 104, and the connection of both ends of bonding tape is realized by wire bonding technology.

[0004] When power module works, its function mainly relies on semiconductor chip, while semiconductor chip runs given function, a large amount of heat loss is inevitably generated, and these heat makes chip and the material around chip be in high temperature state. At the same time, due to the difference of thermal expansion coefficient of different materials, high temperature state can make the interconnection interface of device produce thermal mechanical stress. With the continuous opening and closing of power module when working, power module will be subjected to long-term cyclic thermal mechanical stress, and damage is continuously generated and accumulated, which eventually leads to failure.

[0005] The more serious the thermal expansion coefficient mismatch of the key parts in the power module, the higher the chip temperature, and the larger the temperature fluctuation range, the faster the damage accumulation of the internal structure of the power module, and the shorter the service life of the power module. In recent years, with the continuous development of power semiconductor technology, the integration of power module is continuously rising, and the power density is also continuously rising. Especially in the new generation of semiconductor materials including silicon carbide (SiC), due to the wider band gap of SiC than Si material, it can withstand larger voltage. In order to fully utilize the performance of SiC material, the power density of SiC power module is significantly increased when designed, which means that the working temperature of SiC device is higher, and its service life will be seriously reduced by using the current packaging process.

[0006] However, due to the mismatch of thermal expansion coefficient between the aluminum tape and the chip and the DBC substrate, a large thermal mechanical stress will be generated during the working process of the power module, which may cause damage at the connection point, thereby affecting the reliability and service life of the power module. How to invent a high-reliability power module aluminum tape connection structure to improve these problems has become a problem to be solved by the technical personnel in the field. UTILITY MODEL CONTENTS

[0007] In order to make up for the above shortcomings, the utility model provides a kind of aluminium tape connecting structure for high-reliability power module, to improve the thermal mechanical stress generated at the connection point and the life of power module.

[0008] The utility model is such a realization: a kind of aluminium tape connecting structure for high-reliability power module, including

[0009] DBC substrate, the DBC substrate includes ceramic layer and copper layer, copper layer is located the top of ceramic layer;Chip, the chip is set on above-mentioned DBC substrate;Chip sintered silver solder layer, the chip sintered silver solder layer is located between the chip and the DBC substrate;Aluminium tape, one end of the aluminium tape is connected with the top of the chip, the other end of the aluminium tape is connected with the copper layer of the DBC substrate;Aluminium tape sintered silver solder layer, the aluminium tape sintered silver solder layer is located between the aluminium tape and DBC substrate copper layer.

[0010] In a preferred technical scheme of the utility model, the sintering temperature of the chip sintered silver solder layer and the aluminium tape sintered silver solder layer is 265 DEG C, the sintering time is 10 minutes, and the sintering pressure is 20 MPa.

[0011] In a preferred technical scheme of the utility model, the chip sintered silver solder layer converts the thermal expansion coefficient mismatch of the aluminium tape and the chip into the thermal expansion coefficient mismatch of the aluminium tape and sintered silver.

[0012] In a preferred technical scheme of the utility model, the aluminium tape sintered silver solder layer converts the thermal expansion coefficient mismatch of the aluminium tape and the DBC substrate copper layer into the thermal expansion coefficient mismatch of the aluminium tape and sintered silver.

[0013] In a preferred technical scheme of the utility model, the width and thickness of the aluminium tape are designed according to the current density and thermal stress requirements of the power module.

[0014] In a preferred technical scheme of the utility model, the copper layer of the DBC substrate is connected with the chip through the chip sintered silver solder layer, the copper layer of the DBC substrate is connected with the aluminium tape through the aluminium tape sintered silver solder layer, and the other end of the aluminium tape is connected to the top of the chip.

[0015] The utility model has the advantages that: the aluminium tape connecting structure for high-reliability power module is obtained by the above design, the electrical connection of the aluminium tape, the chip and the DBC substrate is realized by low-temperature sintering of nano-silver solder paste during use, the thermal mechanical stress at the connection point is significantly reduced, and the reliability and service life of the power module are improved. The aluminium tape sintered connecting structure is simple to operate, without the need to expand new power module packaging equipment, which is conducive to reducing production cost and improving production efficiency. By reasonably designing the width and thickness of the aluminium tape, the current density and thermal stress distribution of the connecting structure can be further optimized, and the performance and stability of the power module are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a structural diagram provided by an embodiment of the present utility model;

[0018] Figure 2 A schematic diagram of the original structure provided for an embodiment of the utility model;

[0019] Figure 3 A schematic diagram of the maximum shear stress structure at the connection point of a simulated aluminum ribbon bonding packaging structure provided by an embodiment of the present utility model;

[0020] Figure 4 This is a schematic diagram of the maximum shear stress structure at the connection point of the simulated aluminum strip sintering connection structure provided by the embodiment of the present utility model;

[0021] Figure 5 A schematic diagram of the maximum shear strain structure at the connection point of a simulated aluminum ribbon bonding packaging structure provided by an embodiment of the present utility model;

[0022] Figure 6 This is a schematic diagram of the maximum shear strain structure at the connection point of the simulated aluminum strip sintering connection structure provided by an embodiment of the present utility model.

[0023] In the figure: 101-DBC substrate; 102-chip sintered silver solder layer; 103-chip; 104-aluminum ribbon; 205-aluminum ribbon sintered silver solder layer. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] See also Figure 1 and Figure 2 The utility model provides a technical solution: a high-reliability aluminum strip connection structure for power modules, including

[0026] DBC substrate 101, the DBC substrate 101 includes a ceramic layer and a copper layer located above the ceramic layer for providing stable mechanical support and good thermal conductivity; chip 103, the chip 103 is disposed on the above-mentioned DBC substrate 101, and is a core component of the power module, for realizing a specific electrical function; chip sintered silver solder layer 102, the chip sintered silver solder layer 102 is located between the chip 103 and the DBC substrate 101, and is formed by low-temperature sintering of nano-silver solder paste, realizing electrical connection and heat conduction between the chip 102 and the DBC substrate 101, and at the same time providing mechanical support; aluminum strip 104, one end of the aluminum strip 104 is connected above the chip 103, and the other end of the aluminum strip 104 is connected with the copper layer of the DBC substrate 101, for realizing electrical interconnection between the chip 102 and the external circuit or other elements; aluminum strip sintered silver solder layer 205, the aluminum strip sintered silver solder layer 205 is located between the aluminum strip 104 and the copper layer of the DBC substrate 101, and is formed by low-temperature sintering technology of nano-silver solder paste, for converting the direct connection between the aluminum strip 104 and the chip 102 and the DBC substrate 101 into the connection between the aluminum strip 104 and the sintered silver solder layer, thereby reducing the thermal mechanical stress at the connection point.

[0027] The sintering temperature of the chip sintered silver solder layer 102 and the aluminum strip sintered silver solder layer 205 is 265℃, the sintering time is 10 minutes, and the sintering pressure is 20MPa. The sintering process is simple to operate, and does not need to expand new power module packaging equipment.

[0028] The chip sintered silver solder layer 102 converts the thermal expansion coefficient mismatch between the aluminum strip 104 and the chip 103 into the thermal expansion coefficient mismatch between the aluminum strip 104 and the sintered silver, (aluminum strip thermal expansion coefficient: 23.5×10-6 / ℃, SiC chip thermal expansion coefficient: 4.3×10-6 / ℃) into the thermal expansion coefficient mismatch between the aluminum strip and the sintered silver (aluminum strip 104 thermal expansion coefficient: 23.5×10-6 / ℃, sintered silver thermal expansion coefficient: 19.6×10-6 / ℃), which can significantly reduce the thermal mechanical stress at the connection point, improve the reliability of the power module, and prolong the service life of the power module. The aluminum strip sintered silver solder layer 205 converts the thermal expansion coefficient mismatch between the aluminum strip 104 and the copper layer of the DBC substrate 101 into the thermal expansion coefficient mismatch between the aluminum strip 104 and the sintered silver, (aluminum strip thermal expansion coefficient: 23.5×10-6 / ℃, copper layer thermal expansion coefficient: 16.5×10-6 / ℃) into the thermal expansion coefficient mismatch between the aluminum strip and the sintered silver (aluminum strip thermal expansion coefficient: 23.5×10-6 / ℃, sintered silver thermal expansion coefficient: 19.6×10-6 / ℃), which can significantly reduce the thermal mechanical stress at the connection point, improve the reliability of the power module, and prolong the service life of the power module.

[0029] According to the simulation of the experiment, it is obtained that the introduction of the sintering connection structure of the aluminum band makes the maximum shear stress at the connection point decrease from 113.32 MPa in the prior art to 33.915 MPa in the present application, and makes the maximum shear strain at the connection point decrease from 0.0044034 in the prior art to 0.0013178, which indicates that the connection structure of the present application can realize the purpose of reducing the thermal mechanical stress at the connection point, thereby prolonging the service life of the power module. Figure 3 Figure 4 Figure 5

[0030] The width and thickness of the aluminum band 104 are designed according to the current density and thermal stress requirements of the power module.

[0031] The copper layer of the DBC substrate 101 is connected with the chip 103 through the sintering silver solder layer 102, and the copper layer of the DBC substrate 101 is connected with the aluminum band 104 through the sintering silver solder layer 205, and the other end of the aluminum band 104 is connected to the upper side of the chip 103. This connection structure is particularly suitable for power modules using new generation semiconductor materials including silicon carbide (SiC), and can fully utilize the performance advantages of SiC materials, while ensuring long-term stable operation of the power module under high temperature and high power density conditions.

[0032] Working principle: low-temperature sintering of nano-silver solder paste: one end of the aluminum band 104 is connected with the chip 103 through nano-silver solder paste, and after low-temperature sintering, the connection between the aluminum band 104 and the chip 103 is converted into the connection between the aluminum band 104 and the sintering silver solder layer 205. Similarly, the other end of the aluminum band 104 is also connected with the copper layer of the DBC substrate 101 through nano-silver solder paste, and after low-temperature sintering, it is converted into the connection between the aluminum band 104 and the sintering silver solder layer 205. This connection mode utilizes the good conductivity and thermal conductivity of nano-silver solder paste, and at the same time realizes the firm connection between the aluminum band 104 and the chip 103 and the DBC substrate 101.

[0033] Thermal expansion coefficient matching: there is a difference in the thermal expansion coefficient between the aluminum band 104 and the chip 103 and the DBC substrate 101, which will cause the generation of thermal mechanical stress when the power module is working. Through low-temperature sintering of nano-silver solder paste, the connection between the aluminum band 104 and the chip 103 and the DBC substrate 101 is converted into the connection between the aluminum band 104 and the sintering silver solder layer 205, which can effectively reduce the thermal mechanical stress at the connection point. This is because the thermal expansion coefficient of the sintering silver solder layer 205 is between the aluminum band 104 and the chip 103 (or the copper layer), which plays a role in matching the thermal expansion coefficient, thereby reducing the generation of thermal mechanical stress.

[0034] ​​​Due to the significant reduction of thermal mechanical stress at the connection points, the damage accumulation rate of the internal structure of the power module is slowed down, thereby prolonging the service life of the power module.

[0035] In addition, the sintering process of the nano-silver solder paste is simple to operate, without the need to expand new power module packaging equipment, which is conducive to reducing production cost and improving production efficiency.

[0036] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can be variously changed and modified. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-reliability aluminum strip connection structure for power modules, characterized in that: include A DBC substrate, the DBC substrate comprising a ceramic layer and a copper layer, wherein the copper layer is located above the ceramic layer; A chip, wherein the chip is arranged on the DBC substrate; A chip sintered silver solder layer, the chip sintered silver solder layer being located between the chip and the DBC substrate; an aluminum ribbon, one end of the aluminum ribbon being connected to the top of the chip, and the other end of the aluminum ribbon being connected to the copper layer of the DBC substrate; The aluminum strip sintered silver solder layer is located between the aluminum strip and the DBC substrate copper layer.

2. The aluminum ribbon connection structure for a high-reliability power module according to claim 1, wherein: The copper layer of the DBC substrate is connected to a chip via a chip sintering silver solder layer, and the copper layer of the DBC substrate is connected to an aluminum ribbon via an aluminum ribbon sintering silver solder layer, and the other end of the aluminum ribbon is connected above the chip.

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