A method for preparing interlocking structure metal-imc joint for high temperature packaging

Abstract

The application provides a preparation method of an interlocking structure metal-metal intermetallic compound composite joint for high-temperature packaging, and belongs to the technical field of high-temperature packaging of power chips. The method etches a micron-level pattern on a metal substrate, stacks the etched substrate and a tin-based filler material, and performs hot pressure welding, so that the in-situ generated intermetallic compound and the protruding metal structure of the substrate form mechanical interlocking. The structure significantly improves the mechanical properties of the welding point. The protruding part of the substrate provides a rapid conduction channel for the current and heat flow, enhances the electrical conductivity and thermal conductivity, and at the same time, the enlarged contact area accelerates the metal diffusion, so that a high-performance composite welding point can be quickly formed. The method is suitable for high-temperature reliable packaging of third-generation semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature packaging technology for power chips, and specifically relates to a method for preparing an interlocking structure metal-IMC connector for high-temperature packaging. Background Technology

[0002] Third-generation semiconductors, represented by GaN and SiC, have a wide range of applications due to their advantages such as wider bandgap and higher breakdown voltage. However, because third-generation semiconductors require frequent high-power charging and discharging during operation, higher requirements are placed on the electrical and thermal conductivity of the packaging materials. Furthermore, the frequent start-stop cycles subject the bonding materials to continuous thermal shocks, thus demanding higher mechanical properties and reliability from the packaging materials. Current conventional solders and packaging methods cannot fully meet these requirements, which to some extent limits the application and development of third-generation semiconductors. Transient liquid phase bonding (TLP) technology utilizes the reaction between a melted low-melting-point metal and a high-melting-point metal to form a high-melting-point bonding layer, thereby achieving low-temperature connection and high-temperature operation of power devices. A common TLP structure is a sandwich structure, with the upper and lower substrates being high-melting-point metals Cu or Ni, and the middle being a low-melting-point metal Sn or a Sn alloy. Common Cu-Sn intermetallic compounds include Cu6Sn5 and Cu3Sn, while common Ni-Sn intermetallic compounds include Ni3Sn4 and Ni3Sn. However, high temperatures and long welding times are required to form a sufficiently thick intermetallic compound, and the electrical conductivity, thermal conductivity, and mechanical properties of these compounds are inferior to those of traditional high-temperature solders, limiting their engineering applications. This invention uses surface etching technology to etch morphology on the surfaces of upper and lower substrates. Through thermo-pressure welding, using tin-based alloy as filler material, and based on the principle of instantaneous liquid phase bonding, the intermetallic compound generated in situ combines with the copper structure remaining after the reaction to quickly form a composite solder joint of intermetallic compound and metal structure. In this solder joint, the intermetallic compound and metal structure form an interlocking structure, which can improve the mechanical properties of the intermetallic compound. At the same time, the metal structure in the interlocking structure can improve the overall electrical and thermal conductivity of the solder joint. Summary of the Invention

[0003] In view of the technical problems mentioned in the background art, the purpose of this invention is to provide a method for preparing an interlocking structure metal-metal compound composite connector for high-temperature packaging. The present invention adopts the following technical solution: The present invention includes upper and lower substrates and an intermediate intermetallic compound. The upper and lower substrates are made of copper, copper alloy, nickel, or nickel alloy. The upper and lower substrates are etched before welding, to form micron-scale patterns on the substrate surface. The intermediate intermetallic compound is one or a combination of several of Cu6Sn5, Cu3Sn, Ni3Sn4, Ni3Sn, (Cu,Ni)6Sn5, and (Cu,Ni)3Sn. Under the synergistic effect of temperature and pressure in thermocompression bonding, the upper and lower substrates form a mechanical interlocking structure with the generated intermetallic compound. The addition of pure metal or alloy can improve the mechanical properties of the intermetallic compound. Meanwhile, the interlocking protruding structures of the upper and lower substrates can increase the contact area so as to increase the diffusion rate of the high-melting-point metal. The protruding parts of the interlocking structures on the substrates can provide faster conduction paths for current and heat flow, thereby also improving the electrical and thermal conductivity of the solder joint. The present invention also discloses the above method for laser etching of upper and lower substrates. The adopted technical solution includes the following steps: Step 1: degreasing, impurity removal, cleaning, and pickling the upper and lower metal substrates to improve the cleanliness of the base material surface; Step 2: performing laser etching on the upper and lower metal substrates to obtain an etched morphology; Step 3: cleaning the etched upper and lower metal substrates to remove metal oxides and residual metal scraps generated during the etching process; As a preferred technical solution of the present invention, in Step 1, the upper and lower metal substrates are first immersed in an acetone solution and ultrasonically cleaned for 5 minutes to remove oil stains on the surfaces of the upper and lower metal substrates; then the upper and lower metal substrates are placed in a dilute hydrochloric acid alcohol solution with a mass concentration of 0.5% and ultrasonically cleaned for 5 minutes to remove surface oxides; after that, the upper and lower metal substrates are placed in a nitric acid alcohol solution with a mass concentration of 0.5% and ultrasonically cleaned for 5 minutes to remove insoluble chlorides on the surfaces; finally, the upper and lower metal substrates are placed in alcohol and ultrasonically cleaned for 5 minutes, and then air-dried for later use. As a preferred technical solution of the present invention, in Step 2, the power of the selected laser is 20 W, the etched pattern is a shape of Chinese character "tian" (field), and the spacing between each laser track is 30 μm. As a preferred technical solution of the present invention, in Step 3, the etched upper and lower metal substrates are placed in a dilute hydrochloric acid alcohol solution with a mass concentration of 0.5% and ultrasonically cleaned for 5 minutes to remove oxides and residual metal scraps generated during the etching process; the upper and lower metal substrates are placed in alcohol and ultrasonically cleaned for 5 minutes, and then air-dried for later use. The present invention also discloses the above preparation method of the interlocking structure intermetallic compound. The adopted technical solution includes the following steps: Step 1: Place the etched metal substrate in the order of metal plate / tin-based solder / metal plate, wherein the etched surfaces of the upper and lower substrates must be in contact with the tin-based solder. Step 2: Place the metal plate / tin-based solder / metal plate on a hot press and perform hot press welding. In a preferred embodiment of the present invention, in step 2, the thermocompression welding temperature is 260°C, the welding time is 5 min, and the welding pressure is 20 MPa. During the heating process, tin becomes liquid, and under pressure, the protruding and recessed portions of the upper and lower substrates interlock with each other, and an intermetallic compound is generated between the upper and lower substrates, ultimately forming an interlocking structure of the intermetallic compound and the copper structure. Compared with the prior art, the beneficial effects of this invention are as follows: the upper and lower substrates and the intermetallic compound can form an interlocking structure under pressure. The addition of pure metals or alloys can improve the mechanical properties of the intermetallic compound. A joint with a shear strength of 85 MPa can be obtained under the conditions of 270°C, 20 min, and 20 MPa. Under the same conditions, the joint strength of the untreated substrate is 35 MPa. Simultaneously, the interlocking protruding structure of the upper and lower substrates can increase the contact area, thereby improving the diffusion rate of high-melting-point metals. The protruding parts of the interlocking structure on the substrate can provide a faster channel for current and heat flow, thus improving the electrical and thermal conductivity of the solder joint. The resistivity measured using a four-probe resistance meter under the conditions of 270°C, 20 min, and 20 MPa is 10.32 ± 0.2 μΩ·cm. The resistivity of the entire Cu6Sn5 is 17.5 μΩ·cm, an improvement of approximately 40%. The overall thermal conductivity of the joint at 120°C is 291.38 W / (m·K) measured under the conditions of 270°C, 20 min, and 20 MPa. Attached Figure Description Figure 1 shows the surface morphology of the copper plate after laser etching; Figure 2 shows the cross-sectional morphology of the weld point after hot-press welding.

Claims

1. A method for preparing an interlocking structure metal-metal compound composite connector for high-temperature packaging, comprising upper and lower substrates and an intermediate metal compound, wherein the upper and lower substrates are made of pure metal or alloy material, micron-level patterns are etched on the surface of the substrates, and an interlocking structure between the metal compound and the substrate metal is formed under thermo-pressure welding.

2. The upper and lower substrates according to claim 1, characterized in that: The substrate material is a metal commonly used in electronic packaging, such as copper, copper alloys, nickel, and nickel alloys.

3. The method of etching micron-scale patterns onto the substrate surface according to claim 1, characterized in that, Includes the following steps: Step 1: Degrease, remove impurities, clean, and acid-wash the upper and lower metal substrates; Improve the cleanliness of the substrate surface; Step 2: Etch the upper and lower metal substrates to obtain the etched morphology; Step 3: Clean the etched metal upper and lower substrates to remove metal oxides and residual metal shavings generated during the etching process.

4. The substrate surface etched with micron-level patterns according to claim 3, characterized in that: The etching methods include laser etching, chemical etching, and mechanical processing. The etching depth is 1-100 μm, the etching width is 1-100 μm, the etching interval is 1-100 μm, and the etching pattern is a standard geometric shape, such as a circle, square, or triangle.

5. The interlocking structure formed by the intermetallic compound and the substrate metal under thermocompression welding according to claim 1, characterized in that, Includes the following steps: Step 1: Place the etched metal substrate in the order of metal plate / tin-based solder / metal plate, wherein the etched surfaces of the upper and lower substrates must be in contact with the tin-based solder. Step 2: Place the metal plate / tin-based solder / metal plate on a hot press and perform hot press welding.

6. The interlocking structure formed by the intermetallic compound and the substrate metal under thermocompression welding according to claim 5, characterized in that, In step 2, the hot-press welding temperature is 240-400℃, the welding time is 30-600 s, the welding pressure is 0-100 MPa, and the tin-based brazing filler metal is pure tin, SAC-based brazing filler metal, tin-copper brazing filler metal, tin-bismuth brazing filler metal, tin-antimony brazing filler metal, tin-lead brazing filler metal, or tin-gold brazing filler metal.

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