Slurry and preparation method thereof and packaging method of chip heat dissipation structure

Abstract

The present application relates to the field of electronic packaging interconnection technology, and provides a slurry, including a first welding slurry and a second welding slurry, the first welding slurry and the second welding slurry are respectively measured in independent weight parts, the first welding slurry includes: 1 to 95 parts of a first metal powder, and the melting point of the first metal powder is ≤200°C, 2 to 5 parts of a first organic solvent, 0.5 to 1 part of a first activator, 0.3 to 1 part of a corrosion inhibitor, and 0.1 to 1 part of a first thickener; the second welding slurry includes: 10 to 80 parts of micron metal powder, 10 to 70 parts of nano metal powder, 2 to 5 parts of a second organic solvent, 0.5 to 1 part of a second activator, and 0.1 to 1 part of a second thickener. The slurry provided in the present application can fill the pores formed by sintering the nano metal powder due to the good low-temperature melting fluidity and wettability of the first metal powder in the first welding slurry, and can form an interface material with low porosity, good thermal conductivity, good remelting properties and high reliability.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic packaging and interconnection, and in particular relates to a slurry and a preparation method thereof, and a packaging method for a chip heat dissipation structure. Background Art

[0002] At present, the maximum operating temperature of common packaging materials (such as tin-based solder) is lower than 200°C. Therefore, in order to cope with high-temperature service environments, the industry has proposed transient liquid phase diffusion connection (TLP) and low-temperature nano-sintering interconnection technology, which are used for the formation of full metal compounds and nano-sintering solder joints respectively. However, full metal compounds are brittle, have low thermal conductivity (no more than 70W / mK) and poor reliability; low-temperature nano-sintering has poor wettability, high porosity, and the joints cannot withstand stress caused by different material expansion coefficients when the temperature is increased or decreased, resulting in interface parameter cracks and other problems.

[0003] For example, patent CN104741821A discloses a Sn-based solder paste filled with micro-nano copper particles for high-temperature packaging of electronic modules and a preparation method thereof, which first uses a direct liquid phase multi-element sequential controllable reduction method to sequentially reduce micro-nano copper and micro-nano tin to obtain micro-nano copper-tin particles, and then mixes the micro-nano copper-tin particles with a dispersant, a flux, a thixotropic agent, etc., and makes a solder paste through a mixed dispersion process. However, the solder paste of this scheme has poor oxidation resistance, and the addition of flux brings complex processes to the later solder joint cleaning, etc., and also causes certain environmental pollution. In addition, the solder joint tissue prepared using the solder paste is a full intermetallic compound (IMC) structure, which has large brittleness and a large gap in thermal and electrical conductivity compared to sintered silver. Patent CN114429829A discloses a composite paste for power device encapsulation and a preparation method thereof. The composite paste for power device encapsulation is prepared from silver-copper filler and organic carrier. The silver-copper filler and organic carrier are first stirred until they are evenly mixed to obtain a mixed paste; then the mixed paste is subjected to three-stage dispersion grinding to obtain a composite paste for power device encapsulation, and finally the chip and the substrate are interconnected through the composite paste. However, the composite paste of this scheme has poor interface wettability, is prone to generate holes, has a high welding temperature, and a high pressure may cause mechanical damage to the chip, limiting its application in the field of high-temperature interconnection.

[0004] Therefore, it is necessary to develop a solder paste with good interface wettability, low porosity, good thermal conductivity and high reliability. Summary of the invention

[0005] The purpose of the present application is to provide a slurry and a preparation method thereof and a packaging method for a chip heat dissipation structure, aiming to solve the problems of poor interface wettability, high porosity and poor thermal conductivity of existing welding slurries.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present application provides a slurry, including a first welding slurry and a second welding slurry, wherein the first welding slurry and the second welding slurry are measured in independent parts by weight,

[0008] The first solder paste includes the following components in parts by weight:

[0009]

[0010] The second solder paste includes the following components in parts by weight:

[0011]

[0012] In a second aspect, the present application provides a method for preparing a slurry, comprising the following steps:

[0013] Providing various raw material components in the slurry;

[0014] Performing a first mixing process on a first organic solvent, a first activator, a corrosion inhibitor, a first thickener and a first metal powder to obtain a first welding slurry;

[0015] The second organic solvent, the second activator, the second thickener, the micron metal powder and the nano metal powder are subjected to a second mixing process to obtain a second welding paste.

[0016] In a third aspect, the present application provides a packaging method for a chip heat dissipation structure, comprising the following steps:

[0017] Providing the slurry of the present application or the slurry prepared by the preparation method of the present application, as well as a chip and a heat sink;

[0018] The first solder paste in the slurry is applied on the surface of the chip and subjected to a first pre-curing treatment to form a first solder film, and the second solder paste in the slurry is applied on the surface of the heat sink and subjected to a second pre-curing treatment to form a second solder film; or, the first solder paste in the slurry is applied on the surface of the heat sink and subjected to a first pre-curing treatment to form a first solder film, and the second solder paste in the slurry is applied on the surface of the chip and subjected to a second pre-curing treatment to form a second solder film;

[0019] The chip and the heat sink are bonded relative to each other, and the first welding film is positioned above the second welding film for bonding relative to each other, so as to obtain a chip heat dissipation structure.

[0020] Compared with the prior art, this application has the following beneficial effects:

[0021] The slurry provided in the first aspect of the present application comprises a first welding slurry and a second welding slurry, wherein the first welding slurry contains a first metal powder with a melting point of ≤200°C in a specific weight portion, and the second welding slurry contains a micron metal powder and a nano metal powder in a specific weight portion. By coating the first welding slurry and the second welding slurry on the surface of the chip and the heat sink respectively, the chip and the heat sink can be relatively bonded. Since the first metal powder in the first welding slurry has low-temperature melting fluidity and good wettability, it can effectively fill the pores formed by the nano metal powder during the sintering process, thereby greatly reducing the porosity and improving the thermal conductivity. In addition, the first metal powder has a low melting point and can also form an alloy with the micron metal powder and the nano metal powder, so that it will not remelt at a temperature of up to 500°C, meeting the high-temperature service requirements. In addition, the micron metal powder serves as the skeleton of the network structure, and the nano metal powder serves as a filler to increase the initial packing density and bond the micron metal powder and provide low-temperature sintering properties, thereby reducing the volume shrinkage of the welding slurry, further reducing the porosity, and further improving the stability of the sintered structure. Therefore, the slurry of the present application can form an interface interconnection material with low porosity, good thermal conductivity, good remelting property and high reliability.

[0022] The second aspect of the present application provides a method for preparing a slurry, which comprises the following steps: subjecting a certain weight portion of a first organic solvent, a first activator, a corrosion inhibitor, a first thickener and a first metal powder to a first mixing treatment to obtain a first welding slurry; and subjecting a certain weight portion of a second organic solvent, a second activator, a second thickener, a micron metal powder and a nano metal powder to a second mixing treatment to obtain a second welding slurry. The preparation method is not only simple in process and easy to operate, but also the first welding slurry contains a specific weight portion of the first metal powder, and the second welding slurry contains a specific weight portion of the micron metal powder and the nano metal powder. The good low-temperature melting fluidity and wettability of the first metal powder can effectively fill the pores formed by the nano metal powder during the sintering process, thereby greatly reducing the porosity and improving the thermal conductivity. Therefore, the slurry prepared in the present application can form an interface interconnection material with low porosity, good thermal conductivity, good remelting performance and high reliability, which is suitable for use in the field of power chip packaging.

[0023] The third aspect of the present application provides a packaging method for a chip heat dissipation structure, which comprises first coating a first welding paste in the slurry on the surface of a chip or a heat sink for a first pre-curing treatment to form a first welding film, then coating a second welding paste in the slurry on the surface of a chip or a heat sink without a welding film for a second pre-curing treatment to form a second welding film, and finally performing a relative bonding treatment on the chip and the heat sink, and making the first welding film located above the second welding film for relative bonding to obtain a chip heat dissipation structure. Therefore, the first metal powder in the first welding film located in the upper layer can effectively fill the pores formed by sintering the nano-metal powder in the second welding film located in the lower layer due to its good low-temperature melting fluidity and wettability, and the first metal powder with a low melting point can also form an alloy with the micro-nano metal powder, so that the formed interface interconnection material (welding layer) has the advantages of low porosity, good thermal conductivity, good remelting performance and high reliability, so that the chip heat dissipation structure of the present application has good heat dissipation performance and can meet high-temperature service requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 is a process flow chart of a method for preparing a welding slurry provided in an embodiment of the present application;

[0026] Figure 2 is a process flow chart of a packaging method for a chip heat dissipation structure provided in an embodiment of the present application;

[0027] Figure 3 is a structural diagram of a chip heat dissipation structure provided by an embodiment of the present application;

[0028] Figure 4 is a structural diagram of a chip heat dissipation structure provided by another embodiment of the present application;

[0029] Figure 5 is a SEM image of the sintering interface of the chip heat dissipation structure prepared in Example 1 of the present application;

[0030] Figure 6 This is an optically magnified image of the sintering interface of the chip heat dissipation structure prepared in Comparative Example 1 of the present application;

[0031] Figure 7 This is a SEM cross-sectional view of the indium copper sintering interface of the chip heat dissipation structure prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0034] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0035] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0036] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0037] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0038] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0039] In a first aspect of an embodiment of the present application, a slurry is provided, including a first welding slurry and a second welding slurry, wherein the first welding slurry and the second welding slurry are measured in independent parts by weight,

[0040] The first solder paste includes the following components in parts by weight:

[0041]

[0042] The second solder paste includes the following components in parts by weight:

[0043]

[0044] The slurry provided in the embodiment of the present application includes a first welding slurry and a second welding slurry, wherein the first welding slurry contains a first metal powder with a melting point of ≤200°C in a specific weight portion, and the second welding slurry contains a micron metal powder and a nano metal powder in a specific weight portion. By applying the first welding slurry and the second welding slurry to the surface of the chip and the heat sink respectively, the chip and the heat sink can be relatively bonded. Since the first metal powder in the first welding slurry has low-temperature melting fluidity and good wettability, it can effectively fill the pores formed by the nano metal powder during the sintering process, thereby greatly reducing the porosity and improving the thermal conductivity. In addition, the first metal powder has a low melting point and can also form an alloy with the micron metal powder and the nano metal powder, so that it will not remelt at a temperature of up to 500°C, meeting the high-temperature service requirements. In addition, the micron metal powder serves as the skeleton of the network structure, and the nano metal powder serves as a filler to increase the initial packing density and bond the micron metal powder and provide low-temperature sintering properties, so that the volume shrinkage of the welding slurry can be reduced, the porosity can be further reduced, and the stability of the sintered structure can be further improved. Therefore, the slurry of the present application can form an interface interconnection material with low porosity, good thermal conductivity, good remelting property and high reliability.

[0045] In the embodiment, the first welding slurry and the second welding slurry are each independently measured; the first welding slurry is independently measured by weight, including: 1 to 95 parts of a first metal powder with a melting point ≤ 200°C, 2 to 5 parts of a first organic solvent, 0.5 to 1 part of a first activator, 0.3 to 1 part of a corrosion inhibitor, and 0.1 to 1 part of a first thickener; the second welding slurry is independently measured by weight, including: 10 to 80 parts of micron metal powder, 10 to 70 parts of nano metal powder, 2 to 5 parts of a second organic solvent, 0.5 to 1 part of a second activator, and 0.1 to 1 part of a second thickener; when used, the first welding slurry and the second welding slurry can be selected according to the thickness ratio of the first welding film and the second welding film ((0.3 to 0.5):1) to select how much weight ratio to use, for example, the weight ratio of the first welding slurry and the second welding slurry can be 0.3:1, 0.4:1 or 0.5:1, etc.

[0046] In an embodiment, adding a first metal powder with a melting point within 200°C can reduce surface tension and viscosity, increase the fluidity and wettability of the first welding slurry, thereby effectively filling the pores formed by sintering the micro-nano metal powder, and can greatly reduce the porosity, so that the thermal conductivity performance is good, the welding strength after cold and hot shock changes little, and it can also form an alloy with the micro-nano metal powder, and will not remelt at a temperature of up to 500°C, meeting the high temperature service requirements. The specific first metal powder can be selected from at least one or more of indium powder, tin-bismuth alloy powder, tin-bismuth-silver-copper alloy powder, tin-bismuth-silver alloy powder, tin-indium alloy powder, silver-indium alloy powder and silver-zinc-indium alloy powder. Preferably, the first metal powder is selected from indium powder and tin-bismuth-silver-copper alloy powder. The particle size of the first metal powder is 0.5-10μm, preferably 3-8μm, for example, the average particle size of the first metal powder can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, etc. The weight proportion of the first metal powder may be 50 to 80 parts, for example, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, etc.

[0047] In an embodiment, the first organic solvent is an ether solvent, and specifically can be selected from a mixture of at least one or more of ethylene glycol butyl ether, propylene glycol methyl ether, diethylene glycol butyl ether and propylene glycol ethyl ether, and the weight portion of the first organic solvent can be 2 to 5 parts, such as 2 parts, 3 parts, 4 parts, 5 parts, etc. Adding the first activator can remove oxides on the surface of the chip, heat sink and solder paste at the welding temperature, thereby improving the wettability between the chip, heat sink and solder paste, and the first activator can be selected from a mixture of at least one or more of L-malic acid, glutaric acid, adipic acid and itaconic acid, and the weight portion of the first activator can be 0.5 to 1 part, such as 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, etc. Adding a corrosion inhibitor can protect the substrate and the device-free leads, has moisture-proof, mildew-proof, and corrosion-resistant properties, and can maintain excellent solderability. The corrosion inhibitor can be selected from any one of benzotriazole and tolyltriazole, and the weight portion of the corrosion inhibitor can be 0.5 to 1 part, such as 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc. The first thickener can be selected from any one of polyethylene glycol, polyvinyl butyral, and polyvinyl pyrrolidone, and the weight portion of the first thickener can be 0.1 to 1 part, such as 0.1 part, 0.3 part, 0.5 part, 0.7 part, 0.9 part, 1 part, etc.

[0048] Micron metal powder can be understood as metal powder of micron-level size, and the micron-level size includes a size of 1 μm to 1000 μm. Micron metal powder is mainly used as the skeleton of the network structure, which can reduce the volume shrinkage of the welding slurry and reduce the porosity, thereby improving the stability of the sintered structure and improving the thermal conductivity. In an embodiment, the particle size of the micron metal powder is 1-10 μm, preferably 5 to 8 μm, such as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, etc. The weight of the micron metal powder can be 30-50 parts, such as 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc. The micron metal powder can be selected from a mixture of at least one or more of micron silver powder, micron copper powder, micron silver-copper alloy powder, micron aluminum powder and micron silver-copper powder. Preferably, the micron metal powder is selected from micron silver powder.

[0049] Nano metal powder can be understood as metal powder of nanometer size, and nanometer size includes size of 1nm~1000nm. Nano metal powder is used as filler to improve initial packing density and bond micron metal powder, and provide low temperature sintering property. In an embodiment, the particle size of nano metal powder is 20~200nm, for example, 20nm, 50nm, 100nm, 150nm, 200nm, etc. The weight parts of nano metal powder can be 30-50 parts, for example, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc. Nano metal powder can be selected from a mixture of at least one or more of nano copper powder, nano silver powder and nano silver copper alloy powder. Preferably, nano metal powder is selected from nano silver powder and nano copper powder. Adding nano metal powder and micron metal powder to form a metal composite with good comprehensive performance can further improve the comprehensive performance of welding slurry.

[0050] In an embodiment, the second organic solvent is an ether solvent, and specifically can be selected from a mixture of at least one or more of ethylene glycol butyl ether, propylene glycol methyl ether, diethylene glycol butyl ether and propylene glycol ethyl ether, and the weight portion of the second organic solvent can be 2 to 5 parts, such as 2 parts, 3 parts, 4 parts, 5 parts, etc. Adding a second activator can remove oxides on the surface of the chip, heat sink and solder paste at the welding temperature, thereby improving the wettability between the chip, heat sink and solder paste, and the second activator can be selected from a mixture of at least one or more of L-malic acid, glutaric acid, adipic acid and citric acid, and the weight portion of the second activator can be 0.5 to 1 part, such as 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, etc. The second thickener can be selected from any one of polyethylene glycol, polyvinyl butyral and polyvinyl pyrrolidone, and the weight portion of the second thickener can be 0.1 to 1 part, for example, 0.1 part, 0.3 part, 0.5 part, 0.7 part, 0.9 part, 1 part, etc.

[0051] The second aspect of the present application provides a method for preparing a slurry, such as Figure 1 As shown, the following steps are included:

[0052] S01: providing various raw material components in the slurry;

[0053] S02: performing a first mixing process on a first organic solvent, a first activator, a corrosion inhibitor, a first thickener and a first metal powder to obtain a first welding slurry;

[0054] S03: performing a second mixing process on the second organic solvent, the second activator, the second thickener, the micron metal powder and the nano metal powder to obtain a second welding slurry.

[0055] The preparation method of the slurry provided in the embodiment of the present application is to obtain a first welding slurry by subjecting a certain weight portion of a first organic solvent, a first activator, a corrosion inhibitor, a first thickener and a first metal powder to a first mixing treatment, and obtain a second welding slurry by subjecting a certain weight portion of a second organic solvent, a second activator, a second thickener, a micron metal powder and a nano metal powder to a second mixing treatment. The preparation method is not only simple in process and easy to operate, but also the first welding slurry contains a specific weight portion of the first metal powder, and the second welding slurry contains a specific weight portion of the micron metal powder and the nano metal powder. The good low-temperature melting fluidity and wettability of the first metal powder can effectively fill the pores formed by the nano metal powder during the sintering process, thereby greatly reducing the porosity and improving the thermal conductivity. Therefore, the slurry prepared in the present application can form an interface interconnection material with low porosity, good thermal conductivity, good remelting property and high reliability, which is suitable for use in the field of power chip packaging.

[0056] In the above step S01, the raw material components and contents in the first welding paste and the second welding paste have been described in detail above and will not be repeated here.

[0057] In the above step S02, the step of subjecting the first organic solvent, the first activator, the corrosion inhibitor, the first thickener and the first metal powder to a first mixing treatment includes: firstly mixing, stirring and heating the first organic solvent, the first activator, the corrosion inhibitor and the first thickener to obtain a first mixed material; and then stirring the first metal powder and the first mixed material to be uniform. In this way, the first metal powder can be better dispersed in the first welding slurry to obtain a fully dispersed and uniform first welding slurry.

[0058] In the above step S03, the step of subjecting the second organic solvent, the second activator, the second thickener, the micron metal powder and the nano metal powder to a second mixing treatment includes: firstly mixing, stirring and heating the second organic solvent, the second activator and the second thickener to obtain a second mixed material; mixing (5-15) wt% of the second mixed material with the micron metal powder and then successively performing stirring treatment and grinding treatment to obtain a third mixed material; dispersing the nano metal powder in the remaining second mixed material to obtain a fourth mixed material; mixing the third mixed material and the fourth mixed material and stirring them uniformly. In this way, the micron metal powder and the nano metal powder can be better dispersed in the welding slurry to obtain a fully dispersed and uniform second welding slurry.

[0059] A third aspect of the present application provides a packaging method for a chip heat dissipation structure, such as Figure 2 As shown, the following steps are included:

[0060] S11: providing the slurry of the present application or the slurry prepared by the preparation method of the present application, as well as a chip and a heat sink;

[0061] S12: applying the first solder paste in the slurry on the surface of the chip and performing a first pre-curing treatment to form a first solder film, and applying the second solder paste in the slurry on the surface of the heat sink and performing a second pre-curing treatment to form a second solder film; or, applying the first solder paste in the slurry on the surface of the heat sink and performing a first pre-curing treatment to form a first solder film, and applying the second solder paste in the slurry on the surface of the chip and performing a second pre-curing treatment to form a second solder film;

[0062] S13: The chip and the heat sink are bonded relative to each other, and the first welding film is positioned above the second welding film for relative bonding to obtain a chip heat dissipation structure.

[0063] The packaging method of the chip heat dissipation structure provided in the embodiment of the present application is to first apply the first welding paste in the slurry on the surface of the chip or the heat sink to perform a first pre-curing treatment to form a first welding film, and then apply the second welding paste in the slurry on the surface of the chip or the heat sink without forming a welding film to perform a second pre-curing treatment to form a second welding film, and finally the chip and the heat sink are relatively bonded, and the first welding film is located above the second welding film for relative bonding to obtain a chip heat dissipation structure. Therefore, the first metal powder in the first welding film located in the upper layer can effectively fill the pores formed by sintering the nano metal powder in the second welding film located in the lower layer due to its good low-temperature melting fluidity and wettability, and the first metal powder with a low melting point can also form an alloy with the micro-nano metal powder, so that the formed interface interconnection material (welding layer) has the advantages of low porosity, good thermal conductivity, good remelting property and high reliability, so that the chip heat dissipation structure of the present application has good heat dissipation performance and can meet high-temperature service requirements.

[0064] In the above step S11, the raw material components and contents in the first solder paste and the second solder paste have been described in detail above and will not be repeated here. In an embodiment, the chip is selected from any one of a silicon carbide chip, a silicon-based chip, and an insulated gate bipolar transistor. The heat sink is selected from any one of a substrate containing a metallization layer, a metal substrate, an aluminum oxide substrate, and an aluminum nitride substrate.

[0065] In the above step S12, the temperature of the first pre-curing treatment is 90-120°C. The first solder paste is pre-cured within this temperature range, which is conducive to the complete volatilization of the solvent in the first solder paste, thereby starting to initially set the shape and forming the first solder film. The temperature of the second pre-curing treatment is 90-120°C. The second solder paste is pre-cured within this temperature range, which is conducive to the complete volatilization of the solvent in the second solder paste, thereby starting to initially set the shape and forming the second solder film.

[0066] In the embodiment, the thickness ratio of the first welding film to the second welding film is (0.3-0.5):1, such as 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, etc. Within the thickness ratio range, not only the first welding slurry is prevented from overflowing, but also the formed welding layer has the advantages of low porosity, high welding strength, high thermal conductivity and good remelting property, so that the chip heat dissipation structure of the present application has good heat dissipation performance. Specifically, when the thickness of the first welding film is 20 μm, the thickness of the second welding film can be 40 μm.

[0067] In the above step S13, the step of relatively bonding the chip and the heat sink comprises: stacking the chip and the heat sink and placing them in a hot press at a pressure of 2 to 5 MPa and a temperature of 180 to 250° C. for baking for 2 to 2.5 hours.

[0068] In a specific embodiment, Figure 3 As shown, a first solder paste is coated on the surface of the chip by screen printing, and pre-cured at 90-120°C to form a first solder film; a second solder paste is coated on the surface of the heat sink by screen printing, and a second pre-curing is performed at 90-120°C to form a second solder film; the chip and the heat sink are bonded relative to each other, and the first solder film is located directly above the second solder film (that is, the first solder film is located in the upper layer and the second solder film is located in the lower layer), and the chips are placed in a hot press and baked at a pressure of 2-5 MPa and a temperature of 180-250°C for 2-2.5 hours.

[0069] In a specific embodiment, Figure 4 As shown, a first solder paste is coated on the surface of the heat sink by screen printing, and pre-cured at 90-120°C to form a first solder film; a second solder paste is coated on the surface of the chip by screen printing, and a second pre-curing is performed at 90-120°C to form a second solder film; the chip and the heat sink are bonded relative to each other, and the first solder film is located directly above the second solder film (that is, the first solder film is located in the upper layer and the second solder film is located in the lower layer), and the chip and the heat sink are relatively bonded, and placed in a hot press, and baked for 2-2.5 hours at a pressure of 2-5 MPa and a temperature of 180-250°C.

[0070] The following describes the invention in conjunction with specific embodiments.

[0071] Example 1

[0072] This embodiment provides a slurry and a preparation method thereof and a packaging method of a chip heat dissipation structure. The slurry includes a first welding slurry and a second welding slurry, and the first welding slurry and the second welding slurry are each independently measured;

[0073] The first solder paste includes the following components in parts by weight:

[0074]

[0075]

[0076] The second solder paste includes the following components in parts by weight:

[0077]

[0078] The method for preparing the slurry in this embodiment comprises the following steps:

[0079] S001: Measure each raw material component in the slurry of this embodiment;

[0080] S002: Prepare the first welding slurry:

[0081] Mixing butyl diglycol, glutaric acid, benzotriazole and polyethylene glycol uniformly, and heating until completely dissolved to obtain a first mixed material;

[0082] Adding indium powder with an average particle size of 8 μm and the first mixed material into a planetary mixer and stirring them evenly to obtain a first welding slurry;

[0083] S003: Prepare the second welding slurry:

[0084] Mixing butyl diglycol, glutaric acid and polyethylene glycol uniformly, and heating until they are completely dissolved to obtain a second mixed material;

[0085] 10 wt % of the second mixed material and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and ground and dispersed using a three-roll mill to obtain a third mixed material;

[0086] The remaining (90 wt%) of the second mixed material is mixed with nano silver powder having an average particle size of 80 nm, and ultrasonically dispersed to obtain a fourth mixed material;

[0087] The third mixed material and the fourth mixed material are mixed and stirred evenly to obtain a second welding slurry.

[0088] The packaging method of the chip heat dissipation structure comprises the following steps:

[0089] S011: coating the first solder paste in the paste of this embodiment on the surface of the chip by screen printing, and pre-curing at 120° C. to form a first solder film;

[0090] S012: coating the second solder paste in the paste of this embodiment on the surface of the heat sink by screen printing, and pre-curing at 120° C. to form a second solder film;

[0091] S013: The chip and the heat sink are relatively laminated up and down, and the first welding film is located above the second welding film for relative lamination, and then placed in a hot press, the pressure is maintained at 3MPa and the temperature is increased to 200°C, and the temperature is maintained and the pressure is maintained for 1.5 hours to obtain a chip heat dissipation structure.

[0092] Example 2

[0093] This embodiment provides a slurry and a preparation method thereof and a packaging method of a chip heat dissipation structure. The slurry includes a first welding slurry and a second welding slurry, and the first welding slurry and the second welding slurry are each independently measured;

[0094] The first solder paste includes the following components in parts by weight:

[0095]

[0096] The second solder paste includes the following components in parts by weight:

[0097]

[0098] The method for preparing the slurry in this embodiment comprises the following steps:

[0099] S001: Measure each raw material component in the slurry of this embodiment;

[0100] S002: Prepare the first welding slurry:

[0101] Mixing butyl diglycol, glutaric acid, benzotriazole and polyethylene glycol uniformly, and heating until completely dissolved to obtain a first mixed material;

[0102] Adding tin-bismuth alloy powder with an average particle size of 8 μm and the first mixed material into a planetary mixer and mixing them evenly to obtain a first welding slurry;

[0103] S003: Prepare the second welding slurry:

[0104] Mixing butyl diglycol, glutaric acid and polyethylene glycol uniformly, and heating until they are completely dissolved to obtain a second mixed material;

[0105] 10 wt % of the second mixed material and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and ground and dispersed using a three-roll mill to obtain a third mixed material;

[0106] The remaining (90 wt%) of the second mixed material is mixed with nano silver powder having an average particle size of 80 nm, and ultrasonically dispersed to obtain a fourth mixed material;

[0107] The third mixed material and the fourth mixed material are stirred evenly to obtain a second welding slurry.

[0108] The packaging method of the chip heat dissipation structure comprises the following steps:

[0109] S011: applying the first solder paste in the paste of this embodiment on the surface of the heat sink by screen printing, and pre-curing at 120° C. to form a first solder film;

[0110] S012: coating the second solder paste in the paste of this embodiment on the surface of the chip by screen printing, and pre-curing at 120° C. to form a second solder film;

[0111] S013: The chip and the heat sink are relatively laminated up and down, and the first welding film is located above the second welding film for relative lamination, and then placed in a hot press, the pressure is maintained at 3MPa and the temperature is increased to 200°C, and the temperature is maintained and the pressure is maintained for 1.5 hours to obtain a chip heat dissipation structure.

[0112] Example 3

[0113] This embodiment provides a slurry and a preparation method thereof and a packaging method of a chip heat dissipation structure. The slurry includes a first welding slurry and a second welding slurry, and the first welding slurry and the second welding slurry are each independently measured;

[0114] The first solder paste includes the following components in parts by weight:

[0115]

[0116] The second solder paste includes the following components in parts by weight:

[0117]

[0118] The method for preparing the slurry in this embodiment comprises the following steps:

[0119] S001: Measure each raw material component in the slurry of this embodiment;

[0120] S002: Prepare the first welding slurry:

[0121] Mixing butyl diglycol, glutaric acid, benzotriazole and polyethylene glycol uniformly, and heating until completely dissolved to obtain a first mixed material;

[0122] Adding indium powder with an average particle size of 8 μm and the first mixed material into a planetary mixer and stirring them evenly to obtain a first welding slurry;

[0123] S003: Prepare the second welding slurry:

[0124] Mixing butyl diglycol, glutaric acid and polyethylene glycol uniformly, and heating until they are completely dissolved to obtain a second mixed material;

[0125] 10 wt % of the second mixed material and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and ground and dispersed using a three-roll mill to obtain a third mixed material;

[0126] The remaining (90 wt%) of the second mixed material is mixed with nano copper powder having an average particle size of 80 nm, and ultrasonically dispersed to obtain a fourth mixed material;

[0127] The third mixed material and the fourth mixed material are stirred evenly to obtain a second welding slurry.

[0128] The packaging method of the chip heat dissipation structure of this embodiment is the same as that of the first embodiment.

[0129] Example 4

[0130] This embodiment provides a slurry and a preparation method thereof and a packaging method of a chip heat dissipation structure. The slurry includes a first welding slurry and a second welding slurry, and the first welding slurry and the second welding slurry are each independently measured;

[0131] The first solder paste includes the following components in parts by weight:

[0132]

[0133] The second solder paste includes the following components in parts by weight:

[0134]

[0135] The preparation method of the slurry comprises the following steps:

[0136] S001: Measure each raw material component in the slurry of this embodiment;

[0137] S002: Prepare the first welding slurry:

[0138] Mixing butyl diglycol, glutaric acid, benzotriazole and polyethylene glycol uniformly, and heating until completely dissolved to obtain a first mixed material;

[0139] Adding tin-bismuth alloy powder with an average particle size of 8 μm and the first mixed material into a planetary mixer and mixing them evenly to obtain a first welding slurry;

[0140] S003: Prepare the second welding slurry:

[0141] Mixing butyl diglycol, glutaric acid and polyethylene glycol uniformly, and heating until they are completely dissolved to obtain a second mixed material;

[0142] 10 wt % of the second mixed material and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and ground and dispersed using a three-roll mill to obtain a third mixed material;

[0143] The remaining (90 wt%) of the second mixed material is mixed with nano silver powder having an average particle size of 80 nm, and ultrasonically dispersed to obtain a fourth mixed material;

[0144] The third mixed material and the fourth mixed material are stirred evenly to obtain a second welding slurry.

[0145] The packaging method of the chip heat dissipation structure of this embodiment is the same as that of the first embodiment.

[0146] Example 5

[0147] This embodiment provides a slurry and a preparation method thereof and a packaging method of a chip heat dissipation structure. The slurry includes a first welding slurry and a second welding slurry, and the first welding slurry and the second welding slurry are each independently measured;

[0148] The first solder paste includes the following components in parts by weight:

[0149]

[0150] The second solder paste includes the following components in parts by weight:

[0151]

[0152] The preparation method of the slurry comprises the following steps:

[0153] S001: Measure each raw material component in the slurry of this embodiment;

[0154] S002: Prepare the first welding slurry:

[0155] Propylene glycol ethyl ether, adipic acid, methyl benzotriazole and polyvinyl pyrrolidone are mixed uniformly and heated until completely dissolved to obtain a first mixed material;

[0156] Adding tin-bismuth alloy powder with an average particle size of 8 μm and the first mixed material into a planetary mixer and mixing them evenly to obtain a first welding slurry;

[0157] S003: Prepare the second welding slurry:

[0158] Propylene glycol ethyl ether, adipic acid and polyvinyl pyrrolidone are uniformly mixed and heated until they are completely dissolved to obtain a second mixed material;

[0159] 10 wt % of the second mixed material and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and ground and dispersed using a three-roll mill to obtain a third mixed material;

[0160] The remaining (90 wt%) of the second mixed material is mixed with nano silver powder having an average particle size of 80 nm, and ultrasonically dispersed to obtain a fourth mixed material;

[0161] The third mixed material and the fourth mixed material are stirred evenly to obtain a second welding slurry.

[0162] The packaging method of the chip heat dissipation structure of this embodiment is the same as that of the first embodiment.

[0163] Comparative Example 1

[0164] This comparative example provides a solder paste and a preparation method thereof and a packaging method for a chip heat dissipation structure. The solder paste includes the following components in parts by weight:

[0165]

[0166] The preparation method of the comparative example welding slurry comprises the following steps:

[0167] S1a: mixing butyl diglycol, glutaric acid and polyethylene glycol uniformly, and heating until completely dissolved to obtain a mixed material a;

[0168] S2a: 10 wt% of the mixed material a and micron silver powder with an average particle size of 5 μm are added into a planetary mixer and stirred evenly, and then ground and dispersed using a three-roll mill to obtain a mixed material b;

[0169] S3a: mixing the remaining (90 wt%) of the mixed material a with nano silver powder having an average particle size of 80 nm, and performing ultrasonic dispersion to obtain a mixed material c;

[0170] S4a: Mix the mixed material b and the mixed material c to obtain a welding slurry.

[0171] The packaging method of the chip heat dissipation structure of the comparative example includes the following steps:

[0172] S1b: coating the solder paste of this comparative example on the surface of the chip by screen printing, and pre-curing at 120° C. to form a first solder film;

[0173] S2b: coating the solder paste of this comparative example on the surface of the heat sink by screen printing, and pre-curing at 120° C. to form a second solder film;

[0174] S3b: Fit the chip and heat sink up and down, put them into a hot press, maintain the pressure at 3MPa and raise the temperature to 200℃, and bake them at the same temperature and pressure for 1.5h to obtain a chip heat dissipation structure.

[0175] Comparative Example 2

[0176] This comparative example provides a solder paste and a preparation method thereof and a packaging method for a chip heat dissipation structure. The solder paste includes the following components in parts by weight:

[0177]

[0178] The preparation method of the comparative example welding slurry comprises the following steps:

[0179] S1: uniformly mix butyl diglycol, benzotriazole, glutaric acid and polyethylene glycol, and heat until completely dissolved to obtain a mixed material a;

[0180] S2: adding indium powder with an average particle size of 8 μm, micron silver powder with an average particle size of 5 μm and half of the mixed material a into a planetary mixer and mixing them evenly, and grinding and dispersing them using a three-roll mill to obtain a mixed material b;

[0181] S3: mixing the nano silver powder with an average particle size of 80 nm with the other half of the mixed material a, and performing ultrasonic dispersion to obtain a mixed material c;

[0182] S4: Mix the mixed material b and the mixed material c to obtain a welding slurry.

[0183] The packaging method of the chip heat dissipation structure of this comparative example is the same as that of comparative example 1.

[0184] Related performance test analysis:

[0185] The slurries of Examples 1 to 5 and the welding slurries of Comparative Examples 1 to 2 were characterized, and the performance characterization included:

[0186] (1) Welding strength test process: Take the chip heat dissipation structures prepared in Examples 1 to 5 and Comparative Examples 1 to 2, cut them into 2 mm*2 mm cubes at 5 locations by wire cutting, and fix them on the copper substrate by welding with 305 solder paste. Use a thrust gauge to push the top copper sheet to test the thrust strength.

[0187] (2) Thermal conductivity test: The first welding paste and the second welding paste of Examples 1 to 5 were dried and stacked together (the first welding paste was located on the upper layer), and solidified blocks were prepared at 200° C. and 3 MPa pressure. The welding pastes of Comparative Examples 1 to 2 were prepared at 200° C. and 3 MPa pressure and cut into blocks by wire cutting. The thermal conductivity of the module with a thickness of 2 mm was tested by the laser flash method.

[0188] (3) Remelting property test: The first welding paste and the second welding paste of Examples 1 to 5 were dried and stacked together (with the first welding paste on the upper layer), and solidified into blocks at 200°C and 3 MPa. The welding pastes of Comparative Examples 1 to 2 were solidified into blocks at 200°C and 3 MPa. A small amount of the solidified material was taken for DSC testing and repeatedly scanned 10 times to check the remelting properties of the welding paste.

[0189] (4) Thermal shock reliability test: The chip heat dissipation structures of Examples 1 to 5 and Comparative Examples 1 to 2 were placed in an environment of -40°C and 150°C for thermal cycle testing. After 300 cycles, the thrust change was tested according to the above-mentioned welding strength test process.

[0190] The corresponding evaluation items and standards are shown in Table 1, and the test results are shown in Table 2:

[0191] Table 1

[0192]

[0193] Table 2

[0194] project Welding strength Thermal conductivity Remelting characteristics Thermal shock test welding strength change Example 1 18MPa 240W / m·K none 10％ Example 2 12MPa 190W / m·K none 40％ Example 3 10MPa 180W / m·K none 60％ Example 4 8MPa 170W / m·K none 20％ Example 5 7MPa 169W / m·K none 21％ Comparative Example 1 20MPa 200W / m·K none 120％ Comparative Example 2 7MPa 140W / m·K Remelting 10％

[0195] It can be seen from Table 2 that the change in welding strength of the sintering interface (welding layer) of the chip heat dissipation structure of Examples 1 to 5 after being subjected to thermal shock is significantly lower than that of Comparative Example 1, indicating that the first welding slurry containing the first metal powder with a melting point ≤ 200°C can improve the wettability of the sintering interface, improve the change in welding strength after thermal shock, and has good reliability. The thermal conductivity of the sintered interface of the chip heat dissipation structure of Examples 1 to 5 is significantly higher than that of Comparative Example 2. The sintered interface of the chip heat dissipation structure of Examples 1 to 5 does not remelt, while Comparative Example 2 remelts, indicating that by respectively applying a first welding paste containing a first metal powder with a melting point ≤ 200°C and a second welding paste containing micron metal powder and nano metal powder on the chip and the heat sink to form a first welding film and a second welding film, and then the chip and the heat sink are relatively bonded through the first welding film and the second welding film, the low melting point first metal powder of the first welding paste located in the upper layer can effectively fill the gaps formed by sintering the nano metal powder of the second welding paste, thereby greatly reducing the porosity and improving the thermal conductivity, and the low melting point first metal powder of the first welding paste located in the upper layer can form an alloy with the micro-nano metal powder, so that the sintered interface does not remelt, and thus can meet the high temperature service requirements.

[0196] Figure 5 SEM image of the sintered interface of the chip heat dissipation structure obtained in Example 1, Figure 6 This is an optical magnified image of the sintering interface of the chip heat dissipation structure prepared in Comparative Example 1. Figure 7This is a SEM cross-sectional view of the indium copper sintering interface of the chip heat dissipation structure obtained in Example 3. Figure 5 and 6 It can be seen that the first welding paste of Example 1 of the present application, which contains the first metal powder with a melting point of ≤200° C., can reduce the porosity of the sintering interface.

[0197] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A slurry, characterized in that: The invention comprises a first welding paste and a second welding paste, wherein the first welding paste and the second welding paste are measured in independent parts by weight, The first welding paste comprises the following components in parts by weight: 50-95 parts of first metal powder, wherein the melting point of the first metal powder is ≤200°C; 2-5 parts of the first organic solvent The first activator 0.5~1 part Corrosion inhibitor 0.3~1 part 0.1~1 part of the first thickener; The second welding paste includes the following components in parts by weight: 10~80 parts of micron metal powder Nano metal powder 10~70 parts 2-5 parts of the second organic solvent The second activator 0.5~1 part 0.1~1 part of the second thickener; Among them, the micron metal powder is selected from a mixture of at least one or more of micron silver powder, micron copper powder, micron silver-copper alloy powder, micron aluminum powder and micron silver-coated copper powder; the nano metal powder is selected from a mixture of at least one or more of nano copper powder, nano silver powder and nano silver-copper alloy powder; the slurry is applied in a manner of first coating the first welding slurry on the surface of a chip or a heat sink for a first pre-curing treatment to form a first welding film, then coating the second welding slurry on the surface of a chip or a heat sink without a welding film for a second pre-curing treatment to form a second welding film, and finally performing relative bonding treatment on the chip and the heat sink, and making the first welding film located above the second welding film for relative bonding.

2. The slurry according to claim 1, characterized in that The first metal powder is 50-80 parts; and / or The particle size of the first metal powder is 0.5-10 μm; and / or The first metal powder is selected from at least one of indium powder, tin-bismuth alloy powder, tin-bismuth-silver-copper alloy powder, tin-bismuth-silver alloy powder, tin-indium alloy powder, silver-indium alloy powder and silver-zinc-indium alloy powder.

3. The slurry according to claim 1, characterized in that The first organic solvent is selected from at least one of ethylene glycol butyl ether, propylene glycol methyl ether, diethylene glycol butyl ether and propylene glycol ethyl ether; and / or The first activator is selected from at least one of L-malic acid, glutaric acid, adipic acid and itaconic acid; and / or The corrosion inhibitor is selected from any one of benzotriazole and tolyltriazole; and / or The first thickener is selected from any one of polyethylene glycol, polyvinyl butyral and polyvinyl pyrrolidone.

4. The slurry according to any one of claims 1 to 3, characterized in that The micron metal powder is 30-50 parts, and the nano metal powder is 30-50 parts; and / or The particle size of the micron metal powder is 1-10 μm; and / or The particle size of the nano metal powder is 20-200 nm; and / or.

5. The slurry according to any one of claims 1 to 3, characterized in that The second organic solvent is selected from at least one of ethylene glycol butyl ether, propylene glycol methyl ether, diethylene glycol butyl ether and propylene glycol ethyl ether; and / or The second activator is selected from at least one of L-malic acid, glutaric acid, adipic acid and citric acid; and / or The second thickener is selected from any one of polyethylene glycol, polyvinyl butyral and polyvinyl pyrrolidone.

6. A method for preparing a slurry, characterized in that: The following steps are involved: Providing each raw material component in the slurry according to any one of claims 1 to 5; Performing a first mixing process on the first organic solvent, the first activator, the corrosion inhibitor, the first thickener and the first metal powder to obtain the first welding slurry; The second organic solvent, the second activator, the second thickener, the micron metal powder and the nano metal powder are subjected to a second mixing process to obtain the second welding paste.

7. The preparation method according to claim 6, characterized in that: The step of subjecting the first organic solvent, the first activator, the corrosion inhibitor, the first thickener and the first metal powder to a first mixing treatment comprises: firstly mixing, stirring and heating the first organic solvent, the first activator, the corrosion inhibitor and the first thickener to obtain a first mixed material; then stirring the first metal powder and the first mixed material to be uniform; and / or The step of subjecting the second organic solvent, the second activator, the second thickener, the micron metal powder and the nano metal powder to a second mixing treatment comprises: firstly mixing, stirring and heating the second organic solvent, the second activator and the second thickener to obtain a second mixed material; mixing (5-15) wt % of the second mixed material with the micron metal powder and then successively subjecting the mixture to stirring and grinding to obtain a third mixed material; dispersing the nano metal powder in the remaining second mixed material to obtain a fourth mixed material; and mixing the third mixed material and the fourth mixed material and stirring them evenly.

8. A packaging method for a chip heat dissipation structure, characterized in that: The following steps are involved: Providing the slurry according to any one of claims 1 to 5 or the slurry prepared by the preparation method according to any one of claims 6 to 7, as well as a chip and a heat sink; Applying the first solder paste in the slurry on the surface of the chip and performing a first pre-curing treatment to form a first solder film, and applying the second solder paste in the slurry on the surface of the heat sink and performing a second pre-curing treatment to form a second solder film; Alternatively, the first solder paste in the slurry is applied on the surface of the heat sink to perform a first pre-curing treatment to form a first solder film, and the second solder paste in the slurry is applied on the surface of the chip to perform a second pre-curing treatment to form a second solder film; The chip and the heat sink are bonded relative to each other, and the first welding film is positioned above the second welding film for bonding relative to each other, so as to obtain a chip heat dissipation structure.

9. The packaging method according to claim 8, wherein: The thickness ratio of the first welding film to the second welding film is (0.3-0.5):1; and / or The heat sink is selected from any one of a substrate containing a metallization layer, a metal substrate, an aluminum oxide substrate and an aluminum nitride substrate; and / or The chip is selected from any one of a silicon carbide chip, a silicon-based chip, and an insulated gate bipolar transistor.

10. The packaging method according to claim 8, wherein: The temperature of the first pre-curing treatment is 90-120° C.; and / or The temperature of the second pre-curing treatment is 90-120° C.; and / or The step of relatively bonding the chip and the heat sink comprises: stacking the chip and the heat sink and placing them in a hot press with a pressure of 2-5 MPa and a temperature of 180-250° C. for baking for 2-2.5 hours.

Images