Toughening method of modified Zn-based intermediate layer in aluminum alloy welding

Abstract

The invention discloses a toughening method of a modified Zn-based intermediate layer in aluminum alloy welding, and belongs to the technical field of welding. The method is used for solving the technical problems that in the prior art, when aluminum alloy and copper are welded, a connector is large in brittleness and insufficient in toughness, and comprises the steps that a modified Zn-based middle layer is arranged in a lap joint area of the aluminum alloy and the copper and completely covers a lap joint face, and a to-be-welded assembly is obtained; the welding assembly is placed on a machining platform of ultrasonic welding equipment, pressure is longitudinally applied to the to-be-welded assembly and kept unchanged, ultrasonic auxiliary welding is conducted through the ultrasonic welding equipment, and a lap joint area is welded; according to the welding toughening method for the aluminum alloy containing the modified Zn-based middle layer, the toughness and the mechanical property of a welding joint can be remarkably improved, and the high requirements of a semiconductor packaging heat dissipation system for material reliability and stability can be met through the low thermal cycle cracking rate in the welding joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of welding technology, in particular to a toughening method containing a modified Zn-based interlayer in aluminum alloy welding. BACKGROUND

[0002] With the rapid iteration of information technology, electronic products are accelerating towards "lightweight and high reliability". From microchips in consumer electronics to IGBT modules in the industrial field, the integration of electronic devices is constantly breaking through limits, and the semiconductor packaging, IGBT product packaging and other industries are growing rapidly, directly driving chip-related packaging technology to break through in the direction of lighter and thinner. In this process, the heat dissipation reliability of electronic packaging systems is crucial. Electronic packaging not only carries electronic components, fixes interconnection lines, and protects chips from external environmental interference. With the continuous rise of electronic device density and power, the heat generation rate per unit area of the chip has increased significantly. If the heat cannot be dissipated in time, it may cause chip performance fluctuations, shorten the service life, or even cause thermal runaway, directly causing product failure. Currently, high-performance electronic packaging materials and related processing technologies must meet two core needs: first, excellent thermal conductivity to ensure rapid heat conduction to the heat dissipation structure; second, a thermal expansion coefficient matching the chip to avoid excessive thermal deformation differences between the "package-chip" in the cold-hot cycle, which may cause thermal stress and lead to chip cracking or package interface separation. In ceramic packaging, building an efficient heat path "chip→substrate→copper layer→aluminum alloy→heat sink" to ensure rapid heat dissipation has become the key to solving the problem of electronic packaging heat dissipation. By optimizing the thermal conductivity and interface bonding quality of each layer of material, the thermal resistance can be effectively reduced, and the overall heat dissipation efficiency can be improved. In practical applications, selecting high-thermal-conductivity substrate materials and copper layer designs, combined with the lightweight characteristics of aluminum alloys, not only enables efficient heat transfer, but also ensures structural stability and durability. At the same time, to ensure the reliability of the heat path in long-term use, the welding process needs to be fine-tuned to reduce interface defects and voids, thereby further improving the consistency and stability of heat conduction.

[0003] The traditional welding process of aluminum alloy and copper can easily cause the joint to have brittle phases, welding defects such as pores and cracks, which not only greatly weaken the mechanical strength of the joint, but also damage the continuity of the heat conduction path, either causing the heat dissipation efficiency to decrease and failing to meet the heat dissipation demand of the chip, or causing the joint to crack due to the stress concentration in the long-term thermal cycle, directly affecting the reliability of the heat dissipation system, and seriously deviating from the demand of high reliability and high thermal conductivity of semiconductor packaging. Moreover, the semiconductor packaging heat dissipation system will experience extreme temperature cycles during service, and the welded joint is required to have low resistance and high thermal conductivity to ensure efficient heat transfer. The welding structure of the prior art is prone to cracking during thermal cycling due to problems such as thick IMC layer and non-uniform structure, and the resistance increases significantly with the number of cycles, which is difficult to meet the long-term use demand.

[0004] Chinese patent CN114833492B discloses a welding material for copper-aluminum welding and a copper-aluminum welding method. The welding material for copper-aluminum welding includes a welding flux and a solder. The welding flux includes the following components by mass percentage: ammonium bromide 5%-45%, stannous chloride 13%-35%, sodium fluoride 0.7%-10%, and the balance of zinc chloride. The solder includes the following components by mass percentage: zinc 2.5%-15%, tin 15%-55%, cadmium 1.5%-25%, and the balance of aluminum. The welding flux and the solder are used together to realize the welding of copper-aluminum dissimilar metals, eliminate the heterogeneous interface, and avoid welding hot cracks, but the halide residue of the welding flux is prone to corrosion. The welding temperature of 400-700℃ may damage sensitive components, which is not conducive to the field of semiconductor packaging. Chinese patent CN119870711B discloses an aluminum-copper dissimilar metal composite laser welding method and an aluminum-copper welded joint. The porosity in the weld of the aluminum-copper welded joint prepared by the invention is <0.5 vol.%, and the shear strength is 80-110 MPa, but the atomic radius and crystal structure of aluminum and copper are greatly different, and brittle intermetallic compounds are easily formed during welding, which will become a "weak link" in the joint. The quality of the welded joint needs to be improved. SUMMARY

[0005] The purpose of the present application is to provide a toughening method for aluminum alloy welding containing a modified Zn-based interlayer, which solves the technical problem of large joint brittleness and insufficient toughness when aluminum alloy and copper are welded in the prior art. This method effectively alleviates the stress concentration problem caused by material differences by introducing a modified Zn-based interlayer between the aluminum alloy and the copper. The welded joint obtained by this method has significantly improved tensile strength and fracture toughness, and the low thermal cycle cracking rate of the welded joint can meet the high requirements of semiconductor packaging heat dissipation systems for material reliability and stability.

[0006] To achieve the above objectives, the present invention provides a method for toughening aluminum alloy welding with a modified Zn-based interlayer, comprising the following steps:

[0007] S1: Polish the aluminum alloy and copper surfaces separately, perform ultrasonic cleaning, and dry them;

[0008] S2: A modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded;

[0009] S3: The welding components are placed on the processing platform of the ultrasonic welding equipment, longitudinal pressure is applied to the components to be welded and kept constant, and ultrasonic-assisted welding is performed using the ultrasonic welding equipment to weld the overlapping area.

[0010] The process parameters for ultrasonic-assisted welding are: welding power of 200-500W, amplitude of 25-30μm, frequency of 20-30kHz, and welding time of 10-15s.

[0011] S4: Keeping the pressure in S3 constant, allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0012] Preferably, the thickness of the modified Zn-based intermediate layer is 45-75 μm.

[0013] Preferably, the modified Zn-based intermediate layer component comprises, by weight percentage: Al 4-6%, Mg 2-4%, Mg2Si 1-3%, rare earth elements 0.2-0.6%, with the balance being Zn; the rare earth elements are selected from at least one of Sc, Y, La, and Ce.

[0014] Preferably, the pressure in S3 is 0.8-1.2 MPa.

[0015] Preferably, the particle size of the Mg2Si is 10-20 μm.

[0016] Preferably, the processing platform in S3 is preheated to a temperature of 200-220°C.

[0017] Preferably, the rare earth element is a combination of Sc and Y, with Sc accounting for 0.3-0.4% by weight of the modified Zn-based intermediate layer component and Y accounting for 0.2-0.3% by weight of the modified Zn-based intermediate layer component.

[0018] Preferably, the aluminum alloy is either 6061-T6 or 5083-H32 aluminum alloy.

[0019] Preferably, in S3, the welding components are placed on the processing platform of the ultrasonic welding equipment, and the order from bottom to top is: lower substrate → aluminum alloy → modified Zn-based intermediate layer → copper → upper substrate.

[0020] Preferably, the aluminum alloy has dimensions of 20mm×20mm×3mm and the copper has dimensions of 16mm×16mm×3mm.

[0021] Preferably, an aluminum alloy-copper welded structure is prepared by the toughening method of the modified Zn-based intermediate layer in aluminum alloy welding.

[0022] Preferably, a semiconductor packaging heat dissipation system includes the aforementioned aluminum alloy-copper welded structure.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The toughening method for aluminum alloy welding provided by this invention, which incorporates a modified Zn-based interlayer, optimizes the formation mechanism of intermetallic compounds during welding by introducing a modified Zn-based interlayer between the aluminum alloy and copper, effectively suppressing the excessive growth of brittle intermetallic compounds. Furthermore, the modified Zn-based interlayer possesses good plasticity and ductility, capable of absorbing some of the stress generated during welding, further improving the toughness of the joint. By controlling the composition ratio of the modified Zn-based interlayer, the tensile strength and thermal cycling resistance of the welded joint can be significantly improved, while maintaining a low welding temperature to avoid damage to heat-sensitive materials. This method is not only applicable to semiconductor heat dissipation systems but also provides a new solution for applications in electronic packaging and conventional industrial fields with high welding quality requirements.

[0025] 2. In this invention, Sc is a rare earth element with a much larger atomic radius than Zn, making it prone to segregation at the grain boundaries of the Zn-based interlayer, refining the Zn matrix grains and suppressing the coarsening of Al-Zn IMC. Meanwhile, Y, another rare earth element, can form a stable Y-Cu compound with Cu, adsorbing at the Cu-Zn interface and hindering the diffusion of Cu atoms into the Zn-based interlayer, thus reducing the amount of Cu-Zn formed. This synergistic effect directly optimizes the interface microstructure, resulting in a more uniform and dense interfacial IMC layer and enhancing the long-term thermal cycling stability of the weld joint. Furthermore, the thermal conductivity of Mg2Si is well-matched with Zn, reducing thermal resistance and further improving thermal conductivity. Introducing a modified Zn-based interlayer during welding effectively alleviates the difference in thermal expansion coefficients between aluminum alloys and copper. The modified Zn-based interlayer exhibits good wettability and diffusion properties, contributing to the formation of a uniform and dense weld interface, thereby enhancing the continuity of the thermal conductivity pathway. This method provides a new approach to addressing the defects in traditional welding processes and lays a technical foundation for the high reliability requirements of semiconductor packaging.

[0026] 3. This invention deeply couples the component characteristics of the modified Zn-based interlayer with the ultrasonic-assisted welding process, significantly reducing the weld defect rate and improving the consistency and reliability of the joint. The processing temperature in this invention is lower than the melting point of Zn, reducing bubbles generated by metal melting. Simultaneously, rare earth elements Sc and Y have strong gas adsorption capabilities, capturing H2 and O2 during the welding process, preventing porosity formation, and further reducing porosity. Furthermore, during welding, constant longitudinal pressure promotes the plastic flow of the modified Zn-based interlayer, allowing it to fully fill the tiny gaps at the lap interface while expelling residual air and impurities. The addition of Al and Mg elements in the modified Zn-based interlayer improves the plasticity of the Zn matrix, making it more prone to deformation under pressure, further reducing the formation of unbonded areas and porosity at the interface, and significantly improving the weld density. The welded joint has a low porosity, reducing gas inclusions in the weld and lowering thermal resistance and electrical resistance. Meanwhile, the good metallurgical bonding between the intermediate layer and the Al and Cu substrates reduces the unbonded area at the interface and avoids an increase in contact resistance.

[0027] 4. In this invention, the Al element in the modified Zn-based interlayer inhibits the diffusion of Zn into the Al matrix, Mg2Si particles slow down the diffusion of Al atoms into the Zn-based interlayer, and rare earth elements Sc and Y respectively inhibit the coarsening of Al-Zn IMC and the formation of Cu-Zn. The synergistic effect of these three elements results in a uniform and dense interfacial IMC layer. The rare earth element Sc refines the Zn matrix grains, increasing the number of grain boundaries and resulting in more uniform dispersion of thermal stress at the grain boundaries, thus avoiding cracking caused by localized stress concentration. Simultaneously, the Mg2Si dispersed strengthening phase is less prone to coarsening during thermal cycling, maintaining the mechanical properties of the modified Zn-based interlayer for a long time and further improving the crack resistance of the joint. Specifically, the addition of the modified Zn-based interlayer effectively alleviates the problem of excessive growth or reaction imbalance of the interfacial intermetallic compound (IMC), while simultaneously enhancing the tensile strength and deformation resistance of the joint through a dispersion strengthening mechanism. Furthermore, this method significantly improves the stability of the weld interface, reduces the risk of cracking during thermal cycling, and minimizes the fluctuation range of thermal conductivity. The aluminum alloy-copper welded structure prepared by this invention can better meet the stringent requirements for mechanical properties and thermal reliability in the semiconductor packaging field. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0031] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 10 minutes, and dry.

[0032] S2: A 45μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0033] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 4%, Mg 2%, Mg2Si 1%, rare earth element Sc 0.2%, with the balance being Zn;

[0034] The particle size of Mg2Si is 10 μm.

[0035] S3: The welding components are placed on a 200℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 0.8MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0036] The process parameters for ultrasonic-assisted welding are: welding power of 200W, amplitude of 25μm, frequency of 20kHz, and welding time of 10s.

[0037] S4: Keep the pressure constant at 0.8MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0038] Example 2

[0039] This embodiment provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0040] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 12 minutes, and dry.

[0041] S2: A 60μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded;

[0042] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 5%, Mg 3%, Mg2Si 2%, rare earth element Sc 0.4%, with the balance being Zn;

[0043] The particle size of Mg2Si is 15 μm.

[0044] S3: The welding components are placed on a 210℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 1MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0045] The process parameters for ultrasonic-assisted welding are: welding power of 350W, amplitude of 25μm, frequency of 25kHz, and welding time of 13s.

[0046] S4: Keep the pressure constant at 1MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0047] Example 3

[0048] This embodiment provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0049] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 15 minutes, and dry.

[0050] S2: A 75μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0051] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 6%, Mg 4%, Mg2Si 3%, rare earth element Sc 0.6%, with the balance being Zn;

[0052] The particle size of Mg2Si is 20 μm.

[0053] S3: The welding components are placed on a 220℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 1.2MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0054] The process parameters for ultrasonic-assisted welding are: welding power of 500W, amplitude of 30μm, frequency of 30kHz, and welding time of 15s.

[0055] S4: Keep the pressure constant at 1.2MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0056] Example 4

[0057] This embodiment provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0058] S1: Polish the aluminum alloy 5083-H32 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 10 minutes, and dry.

[0059] S2: A 45μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0060] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 4%, Mg 2%, Mg2Si 1%, rare earth element Sc 0.2%, with the balance being Zn;

[0061] The particle size of Mg2Si is 10 μm.

[0062] S3: The welding components are placed on a 200℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 0.8MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0063] The process parameters for ultrasonic-assisted welding are: welding power of 200W, amplitude of 25μm, frequency of 20kHz, and welding time of 10s.

[0064] S4: Keep the pressure constant at 0.8MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0065] Example 5

[0066] This embodiment provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0067] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 15 minutes, and dry.

[0068] S2: A 75μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0069] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 6%, Mg 4%, Mg2Si 3%, rare earth element Sc 0.3%, rare earth element Y 0.3%, with the balance being Zn;

[0070] The particle size of Mg2Si is 20 μm.

[0071] S3: The welding components are placed on a 220℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 1.2MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0072] The process parameters for ultrasonic-assisted welding are: welding power of 500W, amplitude of 30μm, frequency of 30kHz, and welding time of 15s.

[0073] S4: Keep the pressure constant at 1.2MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the modified Zn-based intermediate layer does not contain rare earth elements, while other conditions remain unchanged.

[0076] This comparative example provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0077] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 10 minutes, and dry.

[0078] S2: A 45μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0079] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 4%, Mg 2%, Mg2Si 1%, with the balance being Zn;

[0080] The particle size of Mg2Si is 10 μm.

[0081] S3: The welding components are placed on a 200℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 0.8MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0082] The process parameters for ultrasonic-assisted welding are: welding power of 200W, amplitude of 25μm, frequency of 20kHz, and welding time of 10s.

[0083] S4: Keep the pressure constant at 0.8MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is that the modified Zn-based intermediate layer does not contain Mg2Si, while other conditions remain the same.

[0086] This comparative example provides a toughening method for aluminum alloy welding with a modified Zn-based interlayer, including the following steps:

[0087] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 10 minutes, and dry.

[0088] S2: A 45μm thick modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded.

[0089] The components containing the modified Zn-based intermediate layer are, by weight percentage: Al 4%, Mg 2%, rare earth element Sc 0.2%, with the balance being Zn;

[0090] S3: The welding components are placed on a 200℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 0.8MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0091] The process parameters for ultrasonic-assisted welding are: welding power of 200W, amplitude of 25μm, frequency of 20kHz, and welding time of 10s.

[0092] S4: Keep the pressure constant at 0.8MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0093] Comparative Example 3

[0094] The difference between this comparative example and Example 1 is that pure zinc is used to replace the modified Zn-based intermediate layer, while other conditions remain unchanged.

[0095] This comparative example provides a method for toughening aluminum alloy welding with a pure Zn-based interlayer, including the following steps:

[0096] S1: Polish the aluminum alloy 6061-T6 with a size of 20mm×20mm×3mm and the copper surface with a size of 16mm×16mm×3mm with 400 grit, 600 grit, 1000 grit and 1500 grit sandpaper for 10 minutes respectively, clean with acetone ultrasonically for 10 minutes, and dry.

[0097] S2: A 45μm thick pure Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded;

[0098] S3: The welding components are placed on a 200℃ processing platform. The aluminum alloy is close to the lower base plate of the processing platform. The welding components are placed from bottom to top as follows: lower base plate → aluminum alloy → modified Zn-based intermediate layer → copper → upper base plate. A longitudinal pressure of 0.8MPa is applied to the components to be welded and kept constant. Ultrasonic welding equipment is used for ultrasonic-assisted welding to weld the overlapping area.

[0099] The process parameters for ultrasonic-assisted welding are: welding power of 200W, amplitude of 25μm, frequency of 20kHz, and welding time of 10s.

[0100] S4: Keep the pressure constant at 0.8MPa and allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

[0101] Performance testing:

[0102] The connectors prepared in Examples 1-5 and Comparative Examples 1-3 were tested and recorded as Samples 1-5 and Samples 6-8, respectively. The specific tests are shown below.

[0103] (1) Tensile property test: Referring to the national standard GB / T 2654-2008 "Tension test method for weld and cladding metal", a TH-8110S servo electronic universal testing machine was used with a speed of 0.1m / min and a maximum load of 100kN. The test was repeated 3 times and the average value was recorded. The results are shown in Table 1.

[0104] (2) Weld porosity test: The MLKX2000 X-ray non-destructive testing instrument was used to detect the porosity of the weld. The working voltage was 43kV and the working current was 40μA. After obtaining the X-ray non-destructive testing results of the weld, the X-ray non-destructive testing images were binarized using MATLAB software, and the porosity of the weld was statistically analyzed using Image-ProPlus 6.0 software. The specific results are shown in Table 1.

[0105] (3) Thermal cycling cracking rate test: Samples 1-8 were placed in a thermal cycling test chamber and tested according to the set thermal cycling parameters. The thermal cycling parameters were: temperature range -55℃ to 150℃, temperature change of 15℃ per minute, cycle time of 30 minutes, and 500 cycles. The cracking rate was calculated and the average value was recorded. The specific test results are shown in Table 1.

[0106] (4) Resistance change rate test: The resistivity of samples 1-8 was tested and the initial resistance was recorded. The resistance of samples 1-8 after the thermal cycling cracking rate test was completed was tested to obtain the final resistance. The test was repeated 3 times and the average resistance change rate was recorded. The specific test results are shown in Table 1.

[0107] Table 1

[0108]

[0109] Data Analysis:

[0110] As shown in Table 1, the welds in Examples 1-5 exhibit excellent overall performance, particularly in joint tensile strength and thermal cycling cracking rate, meeting the high requirements for material reliability and stability in semiconductor packaging heat dissipation systems. Furthermore, the low rate of change of resistivity further demonstrates its superior electrical conductivity, which is especially important for semiconductor devices requiring efficient thermal management. The application of a modified Zn-based interlayer not only improves the overall toughness of the welded structure but also significantly reduces the porosity issue in the weld area, thus providing strong support for the long-term operation of semiconductor packaging heat dissipation systems. This design and optimization of the aluminum alloy-copper welded structure ensures excellent mechanical and thermal conductivity even under complex operating conditions, laying a solid foundation for technological development in related fields.

[0111] As can be seen from the test results in Table 1, the type of aluminum alloy used in Example 4 is different from that in Example 1. The main alloying elements of the aluminum alloy, such as Mg, Si, and Cu, directly participate in the metallurgical reaction that modifies the Zn-based interlayer, changing the type and thickness of the interface and affecting the performance of the welded joint. Example 1 uses 6061-T6, which is an Al-Mg-Si system, while Example 4 uses aluminum alloy 5083-H32, which is an Al-Mg system with a higher Mg content. A higher Mg content will accelerate the formation of the Zn-Mg phase. Although this phase can improve the strength of the interlayer, excessive amounts can easily accumulate at the interface to form a brittle IMC layer, which is detrimental to the toughness of the joint.

[0112] Compared to Example 3, Example 5 uses Sc and Y as rare earth elements, with a total content of 0.6% of the weight of the modified Zn-based interlayer, the same as in Example 1. The atomic radii of Sc and Y are much larger than those of Zn, making them prone to segregation at the grain boundaries and interfaces of the Zn-based interlayer, forming obstacles. Sc can refine the grains of the Zn-based interlayer and suppress the coarsening of Al-Zn IMC; Y forms a stable Y-Cu compound with Cu, adsorbing at the Cu-Zn interface and hindering the diffusion of Cu atoms into the Zn-based interlayer, thereby reducing the formation of Cu-Zn IMC. The synergistic effect of both reduces the amount and thickness of the brittle phase, benefiting the joint performance. Therefore, the interfacial IMC thickness in Sample 5 is more uniform and denser than in Sample 3, avoiding the strength reduction caused by IMC embrittlement. Sample 5 also has a lower thermal cycling cracking rate, far below the 1% threshold required for semiconductor packaging, significantly improving long-term reliability.

[0113] Compared to Example 1, Comparative Example 1 lacks rare earth elements, thus losing the grain refinement and brittle phase suppression effects of rare earth elements. Furthermore, the H2 generated during welding cannot be adsorbed by rare earth elements, leading to porosity. The absence of rare earth elements increases porosity, and the unbonded areas at the interface significantly increase thermal resistance and electrical resistance, reducing the weld's thermal conductivity and hindering heat dissipation for semiconductor devices. As shown in Table 1, the resistance change rate of Sample 6 is significantly greater than that of Sample 1. The lack of rare earth elements increases the zinc content, reducing wettability with Al and Cu. Excessive Zn prevents Al from fully dissolving, and pure Zn has poor room temperature creep properties, making it prone to deformation under stress, which is detrimental to joint quality.

[0114] Compared to Example 1, Comparative Example 2 lacks Mg2Si particles. These smaller Mg2Si particles are the dispersed reinforcing phase in the modified Zn-based interlayer. Their absence leads to a reduction in the reinforcing phase and a significant decrease in tensile strength. The Mg and Si elements contained in the Mg2Si particles can react with the Al matrix to form an Al-Mg-Si phase, slowing down the diffusion rate of Al atoms into the Zn-based interlayer and thus inhibiting the excessive growth of Al-ZnIMC. Without these particles, Al atom diffusion accelerates, increasing the IMC thickness. An excessively thick IMC layer leads to increased interfacial brittleness, reducing the reliability and impact resistance of the welded joint. Simultaneously, the uneven growth of the IMC layer creates stress concentration points in localized areas, further exacerbating the risk of cracking during thermal cycling. This phenomenon not only affects the mechanical strength of the welded structure but also significantly reduces its thermal conductivity, making it difficult to meet the high-efficiency heat dissipation requirements of semiconductor packaging.

[0115] Compared to Example 1, Comparative Example 3 used pure Zn to replace the modified Zn-based intermediate layer, but pure Zn could not balance strength and plasticity, resulting in a decrease in the reliability and stability of the joint.

[0116] In summary, the aluminum alloy-copper welded structure prepared using the toughening method for aluminum alloy welding with a modified Zn-based interlayer provided by this invention exhibits excellent comprehensive performance, demonstrating significant advantages in strength and thermal conductivity. By optimizing the composition and process parameters of the interlayer, the welded joint maintains a stable interface structure even after multiple thermal cycles, avoiding performance degradation caused by excessive growth of brittle phases. Furthermore, its uniformly distributed metallurgical bonding region effectively reduces local stress concentration, thereby improving overall crack resistance. This superior performance combination enables the welded structure to not only meet high strength requirements but also maintain a low resistivity change rate under complex thermal environments, providing a reliable heat dissipation solution for the semiconductor packaging field.

[0117] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0118] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for toughening aluminum alloy welding with a modified Zn-based interlayer, characterized in that, Includes the following steps: S1: Polish the aluminum alloy and copper surfaces separately, perform ultrasonic cleaning, and dry them; S2: A modified Zn-based intermediate layer is placed in the overlap area between the aluminum alloy and copper, and completely covers the overlap surface to obtain the component to be welded; S3: The welding components are placed on the processing platform of the ultrasonic welding equipment, longitudinal pressure is applied to the components to be welded and kept constant, and ultrasonic-assisted welding is performed using the ultrasonic welding equipment to weld the overlapping area. The process parameters for ultrasonic-assisted welding are: welding power of 200-500W, amplitude of 25-30μm, frequency of 20-30kHz, and welding time of 10-15s. S4: Keeping the pressure in S3 constant, allow it to cool naturally to room temperature in an atmospheric environment to obtain an aluminum alloy-copper welded structure.

2. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, The thickness of the modified Zn-based intermediate layer is 45-75 μm.

3. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, The aluminum alloy is either 6061-T6 or 5083-H32 aluminum alloy.

4. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, The pressure in S3 is 0.8-1.2 MPa.

5. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, The modified Zn-based intermediate layer component, by weight percentage, is: Al 4-6%, Mg 2-4%, Mg2Si 1-3%, rare earth elements 0.2-0.6%, with the balance being Zn; the rare earth elements are selected from at least one of Sc, Y, La, and Ce.

6. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 5, characterized in that, The Mg2Si particles have a size of 10-20 μm.

7. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, The processing platform in S3 is preheated to a temperature of 200-220℃.

8. The method for toughening aluminum alloy welding with a modified Zn-based interlayer according to claim 1, characterized in that, In S3, the welding components are placed on the processing platform of the ultrasonic welding equipment. From bottom to top, the order is: lower substrate → aluminum alloy → modified Zn-based intermediate layer → copper → upper substrate.

9. An aluminum alloy-copper welded structure, characterized in that, It was prepared by the toughening method of the modified Zn-based intermediate layer in aluminum alloy welding as described in any one of claims 1-8.

10. A semiconductor package heat dissipation system, characterized in that, Includes the aluminum alloy-copper welded structure as described in claim 9.

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