Silver-based low-temperature and high-thermal-conductivity packaging material with double network structure and preparation method and application thereof

Abstract

The present invention discloses a silver-based low-temperature high-thermal conductivity packaging material with a double network structure, and a preparation method and application thereof. The preparation method of the silver-based low-temperature high-thermal conductivity packaging material comprises: providing a silver material with a porous network structure, wherein the pores in the silver material are directional or non-directional through holes with a micro-nano pore size, and the porosity of the silver material is 25% to 95%; evenly coating a molten low-melting point solder on the silver material, and rolling to obtain a silver-based low-temperature high-thermal conductivity packaging material with a double network structure. The preparation method is simple, reasonable, and flexible in operation. The obtained silver-based low-temperature high-thermal conductivity packaging material has a dense structure, excellent high thermal conductivity, low melting point, no pollution, and other characteristics, which well meets the semiconductor low-temperature packaging needs.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging materials, and in particular to a silver-based low-temperature and high-thermal conductivity packaging material with a double network structure, and a preparation method and application thereof. Background Art

[0002] In order to meet the high thermal conductivity and temperature requirements of semiconductor low-temperature packaging, low-temperature interface materials with high thermal conductivity are urgently needed solders in semiconductor packaging processing. At present, the field of semiconductor packaging usually uses solder alloys (tin and tin-based alloys) or silver-based alloys with silver added as solder to improve high-temperature welding strength and even thermal conductivity. However, the above alloy materials, especially those with a silver content of more than 10%, have the following shortcomings: ① The welding temperature is high, which greatly exceeds the temperature range required by conventional chip packaging processes; ② The thermal conductivity decreases with alloying, making it difficult to meet the high thermal conductivity requirements of chip packaging processes; thus, it is difficult to ensure the reliability of welding and cannot meet the needs of semiconductor packaging processing.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] In order to overcome the above-mentioned defects, the present invention provides a double-network structure silver-based low-temperature and high thermal conductivity packaging material and a preparation method and application thereof. The preparation method is simple, reasonable and flexible to operate. The obtained silver-based low-temperature and high thermal conductivity packaging material has a dense structure and excellent high thermal conductivity, low melting point, no pollution and other characteristics, which well meets the needs of semiconductor low-temperature packaging.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a silver-based low-temperature and high-thermal-conductivity packaging material with a double-network structure, comprising:

[0006] A silver material having a porous network structure is provided, wherein the pores in the silver material are directional or non-directional through holes with a pore size of micro-nanoscale, and the porosity of the silver material is 25% to 95%;

[0007] The low melting point solder in a molten state is uniformly coated on the silver material, and after rolling, a silver-based low-temperature and high thermal conductivity packaging material with a double network structure is obtained.

[0008] As a further improvement of the present invention, the porosity of the silver material is preferably 50% to 90%.

[0009] As a further improvement of the present invention, in the silver material, the through holes are two-dimensional or three-dimensional through holes with an average pore diameter of 2 to 200 μm.

[0010] As a further improvement of the present invention, the silver material is obtained by compounding and mixing silver powder, a binder, an organic solvent and a pore-forming agent, and then performing film-forming and high-temperature treatment.

[0011] As a further improvement of the present invention, the low melting point solder is any one of pure tin, Sn-Bi alloy, Sn-In alloy and Sn-Bi-In alloy.

[0012] As a further improvement of the present invention, the coating process conditions for uniformly coating the molten low melting point solder on the silver material are as follows: the coating conveying speed is 0.3 to 1 m / min; the width of the coating machine roller is 200 to 600 mm;

[0013] In addition, the processing conditions of the rolling are: the rolling rollers are made of polytetrafluoroethylene material, and the gap between the rolling rollers is 0.01-2 mm.

[0014] As a further improvement of the present invention, the molten low-melting-point solder fills all the through holes on the silver material, and at the same time, the molten low-melting-point solder is evenly coated on the surface of the silver material.

[0015] As a further improvement of the present invention, the silver-based low-temperature and high-thermal-conductivity packaging material is a sheet-like structure as a whole, and its thickness is 0.01 to 2 mm.

[0016] The present invention also provides a double-network structure silver-based low-temperature high-thermal conductivity packaging material, which is made by the preparation method of the double-network structure silver-based low-temperature high-thermal conductivity packaging material described in the present invention.

[0017] The present invention also provides an application of the double network structure silver-based low-temperature and high-thermal conductivity packaging material of the present invention as solder for semiconductor packaging.

[0018] The beneficial effects of the present invention are as follows: compared with the prior art, 1) the present invention, through technical innovation, combines a silver material having a micro-nano through-hole network structure and high thermal conductivity with a low-melting point solder having high-efficiency low-temperature melting weldability, thereby preparing a silver-based low-temperature high-thermal conductivity packaging material with a compact structure and excellent high thermal conductivity, low melting point and other characteristics, thereby well meeting the packaging requirements of "high thermal conductivity interface thermal conductivity packaging" and "low temperature, high efficiency and short time" required for semiconductor packaging, and effectively improving the welding effect. In addition, the silver-based low-temperature high-thermal conductivity packaging material obtained by the present invention can also effectively reduce welding stress when used for welding, thereby further improving the welding effect. 2) The silver-based low-temperature high-thermal conductivity packaging material obtained by the present invention does not contain flux, thereby avoiding the application field limitations caused by the use of flux, greatly expanding the applicability and versatility of the silver-based low-temperature high-thermal conductivity packaging material; it also avoids polymer pollution and residues caused by the use of flux, greatly improving the cleanliness, safety and welding effect of the silver-based low-temperature high-thermal conductivity packaging material when used, and saving the cleaning cost after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for preparing the silver-based low-temperature and high-thermal-conductivity packaging material with a double-network structure according to the present invention;

[0020] Figure 2 This is a three-dimensional simulation structure diagram of the double-network structure silver-based low-temperature and high thermal conductivity packaging material described in the present invention.

[0021] Combined with the accompanying drawings, the following description is given:

[0022] 1. Low melting point solder network structure; 2. Silver network structure. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with specific embodiments, but the present application is not limited to the following embodiments.

[0024] The present application provides a dual-network structure silver-based low-temperature high-thermal conductivity packaging material and its preparation method and application. The preparation method is simple, reasonable, and flexible to operate. The obtained silver-based low-temperature high-thermal conductivity packaging material has a dense structure and excellent high thermal conductivity, low melting point, and pollution-free properties, which well meets the semiconductor low-temperature packaging needs. The reason for this is that the present application optimizes and innovates the material selection and preparation method of the silver-based low-temperature high-thermal conductivity packaging material, as described below:

[0025] 1. Prepare the dual-network structure silver-based low-temperature and high thermal conductivity packaging material described in the present application; wherein, Examples 1 to 3 respectively show the situation that the silver material is the same but the low-melting point solder is different; Examples 4 to 7 respectively show the situation that the low-melting point solder is the same but the silver material is different (mainly the porosity of the silver material is different). Example 1

[0026] Please see attached Figure 1 As shown, this embodiment 1 provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double network structure, comprising the following preparation steps:

[0027] S1: providing a silver material having a porous network structure, wherein the pores in the silver material are directional or non-directional through holes with a pore size of micro-nano scale, and the porosity of the silver material is 25% to 95%.

[0028] Specifically, the method for preparing the silver material having a porous network structure described in Example 1 is as follows:

[0029] S11: silver powder is obtained by atomization powder making process, the particle size of the obtained silver powder is 300-400 mesh (37-48 μm), and the purity is more than 99.9%. It can be understood that the obtained silver powder belongs to fine silver powder.

[0030] The above-mentioned atomization powder making process is a method for making powder by atomizing a molten fluid (metal or alloy liquid) by rapid jetting, that is, forming the metal or alloy liquid into fine droplets, and then rapidly condensing them into solid spherical powder. This is a conventional technical means in the field of metal powder making, so it will not be described in detail here.

[0031] Supplementary explanation: According to product design requirements, chemical or electrochemical methods can also be used to produce ultrafine silver powder with a particle size of 0.05 to 5 μm when making silver powder.

[0032] S12: The obtained silver powder is mixed with a binder and the like to prepare a slurry.

[0033] Specifically, according to product design requirements, the slurry used to make the silver material in Example 1 may preferably adopt the following raw material formula: by weight percentage, 40% to 80% silver powder, 5% to 20% binder, 5% to 20% organic solvent and 10% to 20% pore-forming agent; the binder is preferably at least one of epoxy resin, acrylic resin, phenolic resin, ethyl cellulose, polyethylene glycol and polyvinyl alcohol; the organic solvent is preferably at least one of ethanol, propanol, isopropanol, acetone, toluene, xylene, pine alcohol, triethanolamine, isophorone and dibasic acid ester; the pore-forming agent is preferably at least one of polyethylene and polypropylene.

[0034] Specifically, the slurry is compounded by 70% of the silver powder, 8% of the binder (epoxy resin), 12% of the organic solvent (toluene) and 10% of the pore-forming agent (polyethylene) in terms of weight percentage.

[0035] It is understandable that, ① in the raw material formula of the above slurry, the organic solvent is used to dissolve the binder and disperse the silver powder and the pore-forming agent; the binder is used to bond the silver powder and the pore-forming agent; the pore-forming agent is used to generate the through holes in the silver material structure. ② The raw material formula of the above slurry is only a preferred embodiment. When the present application is actually used, the slurry used to make the silver material is not limited to the above raw material formula.

[0036] S13: coating or rolling the slurry to form a membrane blank, and then drying and high-temperature treating the membrane blank in sequence to obtain the silver material with a porous network structure.

[0037] Specifically, the drying process can be performed in a vacuum oven.

[0038] The high temperature treatment method may preferably adopt a high temperature sintering process, and the specific processing conditions of the high temperature sintering process may be optimally controlled as follows: nitrogen is selected as the protective gas, hydrogen is selected as the reducing gas; and sintering is performed at 750-900°C for 30-120 minutes. Supplementary explanation: The sintering time is determined according to the thickness of the obtained silver material and the specific application. Generally, a relatively short sintering time can be selected for thin silver materials, and a relatively long sintering time can be selected for thick silver materials.

[0039] Based on the above preferred method for making the silver material, it can be known that ① the present application adopts a method combining the processes of "making fine silver powder", "preparing slurry", "making membrane blank", "high temperature treatment (high temperature sintering)" to make the silver material, which can make the silver material have the characteristics of controllable overall thickness and size, controllable hole shape, pore size and layout of through holes, so that the silver material can have excellent micro-nano porous network structure characteristics, ultra-thinness, miniaturization and other characteristics. ② The method for making the silver material described in the present application is simple, reasonable, novel, easy to process, and low in processing cost, and can realize continuous and large-scale production.

[0040] In addition, based on the above-mentioned preferred method for making the silver material, the porosity of the silver material structure obtained in this embodiment 1 reaches 50%±2%, and the through hole is presented as a directional three-dimensional through hole with a spherical hole shape and an average pore size of 30 to 40 μm. It can be understood that in the silver material structure obtained in this embodiment 1, several of the three-dimensional through holes together constitute an array-type porous network structure. Through the array-type porous network structure and based on the good interface wettability between the silver material and the following low-melting point solder, the molten material of the following low-melting point solder can be quickly immersed in the array-type porous network structure with a controllable filling amount, and combined with it to form a dense double network interactive structure.

[0041] In addition, to facilitate the following coating and rolling operations, the silver material prepared in Example 1 is a sheet structure, and the thickness can be optimally controlled to be 0.05-1 mm. However, it is understandable that in the actual production process, the silver material is not limited to a sheet structure, and can also be a wire structure.

[0042] S2: evenly coating the molten low-melting-point solder on the silver material, and rolling it to obtain a silver-based low-temperature and high-thermal-conductivity packaging material with a double-network structure.

[0043] Specifically, the preferred processing method for coating the low melting point solder on the silver material and performing roller pressing in this embodiment 1 is:

[0044] S21: placing the silver material provided in S1 above on a work pad.

[0045] In particular, the working pad is made of Teflon material; before or after the silver material is placed on the working pad, the silver material needs to be preheated to the same temperature as the molten material of the following low-melting-point solder (in this embodiment 1, the silver material needs to be preheated to 242°C to 252°C) to ensure that the interface reactivity between the molten material of the low-melting-point solder and the silver material reaches the best state, that is, it has good interface reactivity to achieve the infiltration and composite effect, but does not melt the skeleton of the silver material during the short coating and composite operation process.

[0046] S22: using analytical pure tin (hereinafter referred to as “pure tin”) with a melting point of 232° C. as the low melting point solder, and heating the pure tin until it is melted to obtain a molten pure tin.

[0047] In this embodiment 1, the temperature of the molten pure tin is also optimally controlled to be higher than the melting point of the pure tin, specifically, the temperature of the molten pure tin is controlled at 242°C to 252°C (i.e., appropriately overheated by 10°C to 20°C). This can help improve the uniformity of coating the molten pure tin on the preheated silver material during coating in the subsequent process, and can help improve the interface reactivity between the molten pure tin and the preheated silver material, thereby achieving good interface wettability between the two.

[0048] S23: using a coater (preferably a single-sided continuous roller coater) to uniformly coat the molten pure tin on the preheated silver material, wherein the coating process conditions of the coater are preferably: a coating conveying speed of 0.3 to 1 m / min; and a coater roller width of 200 to 600 mm.

[0049] It can be understood that, on the one hand, due to the good interface wettability between the molten pure tin and the preheated silver material, the molten pure tin can be easily (quickly) and evenly coated on the surface of the silver material; on the other hand, due to the formation of an array-type porous network structure on the silver material, the molten pure tin can be coated on the silver material with a set and relatively large coating amount; thereby, the combination of the pure tin and the silver material can well meet the high thermal conductivity and low melting point requirements of solder for semiconductor low-temperature packaging.

[0050] In addition, according to product design requirements, through the interface wetting characteristics between the molten pure tin and the preheated silver material, and the above-mentioned coating process, it is possible to make the molten low-melting point solder fill all the through holes on the silver material and also make the molten low-melting point solder evenly coat the surface (such as the peripheral surface) of the silver material.

[0051] S24: The silver material coated with the pure tin is subjected to roller pressing by a roller press, and the processing conditions of the roller pressing are preferably: the rollers are made of polytetrafluoroethylene material, and the gap between the rollers is 0.01-2 mm (can be further optimized to 0.18-0.5 mm); a silver-based low-temperature and high-thermal conductivity packaging material with a sheet structure and a double network structure can be obtained. It can be understood that ① "double network structure" refers to: a silver network structure and a pure tin network structure that are interactively combined into one; please refer to the attached Figure 2 In the three-dimensional simulation structure diagram shown, label 1 indicates "low melting point solder network structure" and label 2 indicates "silver network structure". ② The shape of the silver-based low temperature and high thermal conductivity packaging material is not limited to the above-mentioned sheet shape, and can be determined according to product design requirements.

[0052] Furthermore, based on the above rolling process, the thickness of the silver-based low temperature and high thermal conductivity packaging material prepared in this embodiment 1 can be optimally controlled to be 0.01-2 mm. Furthermore, in this embodiment 1, the thickness of the silver-based low temperature and high thermal conductivity packaging material is preferably 0.2 mm.

[0053] In addition, according to product design requirements, after the silver-based low-temperature and high-thermal conductivity packaging material is obtained, this embodiment 1 can also selectively perform calendering or rolling processing on the silver-based low-temperature and high-thermal conductivity packaging material to further obtain the ultra-thin thickness of the silver-based low-temperature and high-thermal conductivity packaging material.

[0054] S3: The silver-based low-temperature and high-thermal conductivity packaging material (or the ultra-thin silver-based low-temperature and high-thermal conductivity packaging material) is subjected to conventional quality inspection and analysis, die-cutting and other processing operations in sequence, and the finished product of the silver-based low-temperature and high-thermal conductivity packaging material required for the process is produced after completion. Example 2

[0055] This embodiment 2 also provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double-network structure. Compared with embodiment 1, the difference of this embodiment 2 mainly lies in that the low melting point solder used in this embodiment 2 is different from that in embodiment 1.

[0056] Specifically, in this embodiment 2, a 42Sn-58Bi alloy with a melting point of 139° C. is used as the low melting point solder, and the 42Sn-58Bi alloy refers to a Sn-Bi alloy composed of 42% by weight of Sn and 58% by weight of Bi. It can be understood that the 42Sn-58Bi alloy also has good interface wettability with the silver material.

[0057] Correspondingly, in Example 2, before using the 42Sn-58Bi alloy for coating, the 42Sn-58Bi alloy is also heated and melted to obtain a molten material of the 42Sn-58Bi alloy. At the same time, the temperature of the molten material of the 42Sn-58Bi alloy is optimized to be between 149°C and 159°C (i.e., appropriately overheated by 10°C to 20°C), and the silver material (the same as the silver material obtained in Example 1) is preheated to 149°C to 159°C to improve the uniformity of coating the molten material of the 42Sn-58Bi alloy on the silver material, and to improve the interface reactivity / interface wettability between the molten material of the 42Sn-58Bi alloy and the silver material.

[0058] Based on the above differences, and in the case where the same silver material, coating and rolling process as in Example 1 are used in Example 2, a silver-based low-temperature and high-thermal-conductivity packaging material with an overall sheet structure and a double-network structure is also prepared in Example 2. Furthermore, in Example 2, the thickness of the silver-based low-temperature and high-thermal-conductivity packaging material is preferably 0.15 mm.

[0059] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 2, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then conventional quality inspection and analysis, die-cutting and other processing operations are carried out to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process. Example 3

[0060] This embodiment 3 also provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double-network structure. Compared with embodiment 1, the difference of this embodiment 3 mainly lies in that the low melting point solder used in this embodiment 3 is different from that in embodiment 1.

[0061] Specifically, in this embodiment 3, a 59Sn-41In alloy with a melting point of 119° C. is used as the low melting point solder, and the 59Sn-41In alloy refers to a Sn-In alloy composed of 59% by weight of Sn and 41% by weight of In. It can be understood that the 59Sn-41In alloy also has good interface wettability with the silver material.

[0062] Correspondingly, in this embodiment 3, before using the 59Sn-41In alloy for coating, the 59Sn-41In alloy is also heated and melted to obtain the molten material of the 59Sn-41In alloy. At the same time, the temperature of the molten material of the 59Sn-41In alloy is optimized to be between 129°C and 139°C (i.e., appropriately overheated by 10°C to 20°C), and the silver material (the same as the silver material obtained in embodiment 1) is preheated to 129°C to 139°C to improve the uniformity of coating the molten material of the 59Sn-41In alloy on the silver material, and to improve the interface reactivity / interface wettability between the molten material of the 59Sn-41In alloy and the silver material.

[0063] Based on the above differences, and in the case where the same silver material, coating and rolling process as in Example 1 are used in Example 3, a silver-based low-temperature and high-thermal-conductivity packaging material with an overall sheet structure and a double-network structure is also prepared in Example 3. Furthermore, in Example 3, the thickness of the silver-based low-temperature and high-thermal-conductivity packaging material is preferably 0.1 mm.

[0064] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 3, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then subjected to conventional quality inspection and analysis, die-cutting and other processing operations to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process. Example 4

[0065] This embodiment 4 also provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double-network structure. Compared with embodiment 1, the difference of this embodiment 4 mainly lies in that the silver material prepared in this embodiment 4 is different from that in embodiment 1.

[0066] Specifically, in Example 4, when making the silver material, the slurry formula used is: by weight percentage, the slurry is compounded by 60% silver powder, 15% binder (ethyl cellulose), 12% organic solvent (toluene) and 13% pore-forming agent (polypropylene), wherein the particle size of the silver powder is 300-400 meshes and the purity is above 99.9%. The obtained slurry is made into a film blank by coating or rolling process, and then vacuum drying and high-temperature sintering treatment are carried out in sequence to obtain the silver material with a porous network structure.

[0067] In the silver material structure obtained in Example 4, the porosity reaches 60%±2%, and the through holes are directional, spherical, and three-dimensional through holes with an average pore size of 30-40 μm, that is, a plurality of the three-dimensional through holes together form an array-type porous network structure. In addition, the silver material is also a sheet structure with a thickness of 0.05-1 mm as a whole.

[0068] Based on the above differences, and in the case where the same low melting point solder, the same coating and rolling process as in Example 1 are used in Example 4, a silver-based low temperature and high thermal conductivity packaging material with an overall sheet structure and a double network structure is also prepared in Example 4. Furthermore, in Example 4, the thickness of the silver-based low temperature and high thermal conductivity packaging material is preferably 0.2 mm.

[0069] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 4, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then conventional quality inspection and analysis, die cutting and other processing operations are carried out to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process. Example 5

[0070] This embodiment 5 also provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double-network structure. Compared with embodiment 1, the difference of this embodiment 5 mainly lies in that the silver material used in this embodiment 5 is different from that in embodiment 1.

[0071] Specifically, in Example 5, when making the silver material, the slurry formula used is: by weight percentage, the slurry is compounded by 65% ​​silver powder, 10% binder (epoxy resin), 10% organic solvent (toluene) and 15% pore-forming agent (polypropylene), wherein the particle size of the silver powder is 300-400 meshes and the purity is above 99.9%. After the obtained slurry is made into a film blank by coating or rolling process, vacuum drying and high-temperature sintering treatment are carried out in sequence to obtain the silver material with a porous network structure.

[0072] In the silver material structure obtained in Example 5, the porosity reaches 70%±2%, and the through holes are directional, spherical, and three-dimensional through holes with an average pore size of 30-40 μm, that is, a plurality of the three-dimensional through holes together form an array-type porous network structure. In addition, the silver material is also a sheet structure with a thickness of 0.05-1 mm as a whole.

[0073] Based on the above differences, and in the case where the same low melting point solder, the same coating and rolling process as in Example 1 are used in Example 5, a silver-based low temperature and high thermal conductivity packaging material with an overall sheet structure and a double network structure is also prepared in Example 5. Furthermore, in Example 5, the thickness of the silver-based low temperature and high thermal conductivity packaging material is preferably 0.3 mm.

[0074] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 5, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then conventional quality inspection and analysis, die-cutting and other processing operations are carried out to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process. Example 6

[0075] This embodiment 6 also provides a method for preparing a silver-based low-temperature and high-thermal conductivity packaging material with a double-network structure. Compared with embodiment 1, the difference of this embodiment 6 mainly lies in that the silver material used in this embodiment 6 is different from that in embodiment 1.

[0076] Specifically, in Example 6, when making the silver material, the slurry formula used is: by weight percentage, the slurry is compounded by 58% silver powder, 12% binder (epoxy resin), 13% organic solvent (toluene) and 17% pore-forming agent (polyethylene), wherein the particle size of the silver powder is 300-400 meshes and the purity is above 99.9%. After the obtained slurry is made into a film blank by coating or rolling process, vacuum drying and high-temperature sintering treatment are carried out in sequence to obtain the silver material with a porous network structure.

[0077] In the silver material structure obtained in Example 6, the porosity reaches 80%±2%, and the through holes are directional, spherical, and three-dimensional through holes with an average pore size of 30-40 μm, that is, a plurality of the three-dimensional through holes together form an array-type porous network structure. In addition, the silver material is also a sheet structure with a thickness of 0.05-1 mm as a whole.

[0078] Based on the above differences, and in the case where the same low melting point solder, the same coating and rolling process as in Example 1 are used in Example 6, a silver-based low temperature and high thermal conductivity packaging material with an overall sheet structure and a double network structure is also prepared in Example 6. Furthermore, in Example 6, the thickness of the silver-based low temperature and high thermal conductivity packaging material is preferably 0.2 mm.

[0079] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 6, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then subjected to conventional quality inspection and analysis, die-cutting and other processing operations to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process. Example 7

[0080] This embodiment 7 also provides a method for preparing a double-network structure silver-based low-temperature and high-thermal conductivity packaging material. Compared with embodiment 1, the difference of this embodiment 7 mainly lies in that the silver material used in this embodiment 7 is different from that in embodiment 1.

[0081] Specifically, in Example 7, when making the silver material, the slurry formula used is: by weight percentage, the slurry is compounded by 50% silver powder, 14% binder (ethyl cellulose), 16% organic solvent (toluene) and 20% pore-forming agent (polyethylene), wherein the particle size of the silver powder is 300-400 meshes and the purity is above 99.9%. After the obtained slurry is made into a film blank by coating or rolling process, vacuum drying and high-temperature sintering treatment are carried out in sequence to obtain the silver material with a porous network structure.

[0082] In the silver material structure obtained in Example 7, the porosity reaches 90%±2%, and the through holes are directional, cylindrical, and two-dimensional through holes with an average pore size of 30-40 μm, that is, a plurality of the two-dimensional through holes together form an array-type porous network structure. In addition, the silver material is also a sheet structure with a thickness of 0.05-1 mm as a whole.

[0083] Based on the above differences, and in the case where the same low melting point solder, the same coating and rolling process as in Example 1 are used in Example 7, a silver-based low temperature and high thermal conductivity packaging material with an overall sheet structure and a double network structure is also prepared in Example 7. Furthermore, in Example 7, the thickness of the silver-based low temperature and high thermal conductivity packaging material is preferably 0.2 mm.

[0084] In addition, after the silver-based low-temperature and high thermal conductivity packaging material is obtained in this embodiment 7, the silver-based low-temperature and high thermal conductivity packaging material can be selectively calendered or rolled according to product design requirements, and then subjected to conventional quality inspection and analysis, die-cutting and other processing operations to complete the production of the finished silver-based low-temperature and high thermal conductivity packaging material required by the post-process.

[0085] 2. Provide comparative examples;

[0086] The Sn-Bi binary alloy commonly used in the market is used as a comparative sample. The Sn-Bi binary alloy has a melting point of 139° C. and can be welded at a temperature below 185° C.

[0087] 3. Performance test of the double network structure silver-based low temperature and high thermal conductivity packaging material obtained in this application;

[0088] 3.1) Physical and chemical test results of the silver-based low-temperature and high-thermal conductivity packaging materials obtained in Examples 1 to 7 of the present application and the comparative samples:

[0089] Physical and chemical tests were performed on the silver-based low-temperature and high thermal conductivity packaging materials obtained in Examples 1 to 7 of the present application and the comparative samples, respectively. The test contents included: thermal conductivity test, melting point test, etc. The test results are shown in Table 1 below.

[0090] Table 1 Performance test results of the silver-based low-temperature and high-thermal conductivity packaging materials obtained in this application and the comparative samples

[0091]

[0092] It can be seen from Table 1 that the thermal conductivity of the silver-based low-temperature and high thermal conductivity packaging materials prepared in Examples 1 to 7 of the present application is controlled at 55 to 225 W / (m·K), and the melting point is controlled near the melting point of the low-melting point solder; that is, the silver-based low-temperature and high thermal conductivity packaging materials obtained in the present application have excellent high thermal conductivity and low melting point, and can be well applied to the field of semiconductor low-temperature packaging.

[0093] As for the comparative sample, although it has the performance of a low melting point, its thermal conductivity is relatively low, only 19 W / (m·K). Therefore, compared with the present application, the comparative sample cannot well meet the requirements of semiconductor low-temperature packaging.

[0094] 3.2) Welding performance test and results of the silver-based low-temperature and high-thermal conductivity packaging materials obtained in Examples 1 to 7 of the present application and the comparative samples:

[0095] The silver-based low-temperature and high-thermal-conductivity packaging materials obtained in Examples 1 to 7 of the present application and the comparative samples were respectively used for SMT reflow soldering, and the process parameters used during soldering were the same; then the smoke size, thermal stress size and distribution, and post-soldering residue during the soldering process were tested; the test results are shown in Table 2 below:

[0096] Table 2 Welding performance test results of the silver-based low-temperature and high-thermal conductivity packaging materials obtained in this application and the comparative samples

[0097]

[0098] It can be seen from Table 2 that when the SMT reflow soldering operation is performed using the silver-based low-temperature and high thermal conductivity packaging materials obtained in Examples 1 to 7 of the present application, ① no smoke is generated during the welding process and no residue is left after welding, which indicates that the silver-based low-temperature and high thermal conductivity packaging materials obtained in the present application have a high degree of cleanliness when used for welding, which not only ensures that the application site is pollution-free, but also saves the cleaning cost after welding; ② the thermal stress during welding is small and the thermal stress is evenly distributed, which indicates that when the silver-based low-temperature and high thermal conductivity packaging materials obtained in the present application are used for welding, the welding reliability defects caused by the risk of PCB and chip warping caused by thermal stress can be well avoided, and the welding effect is greatly improved.

[0099] As for the comparative sample, when performing SMT reflow soldering, the thermal stress generated is large, which will cause the interface bonding force between the PCB and the chip to be relatively low, thus easily causing product warping, poor welding quality, etc. Therefore, compared with the present application, the comparative sample cannot meet the semiconductor low-temperature packaging requirements well.

[0100] In summary, the present application, through technical innovation, combines a silver material having a micro-nano through-hole network structure and high thermal conductivity with a low-melting point solder having high low-temperature melting weldability, and obtains a silver-based low-temperature high thermal conductivity packaging material with a compact structure and excellent high thermal conductivity, low melting point and other characteristics, so that it can well meet the packaging requirements of "high thermal conductivity interface thermal conductivity packaging" and "low temperature, high efficiency and short time" required for semiconductor packaging, and effectively improve the welding effect. In addition, the silver-based low-temperature high thermal conductivity packaging material obtained in the present application can also effectively reduce welding stress when used for welding, thereby further improving the welding effect. In addition, the silver-based low-temperature high thermal conductivity packaging material obtained in the present application does not contain flux, thereby avoiding the application field limitations caused by the use of flux, greatly expanding the applicability and versatility of the silver-based low-temperature high thermal conductivity packaging material; and avoiding polymer pollution and residues caused by the use of flux, greatly improving the cleanliness, safety and welding effect of the silver-based low-temperature high thermal conductivity packaging material when used, and saving the cleaning cost after welding.

[0101] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a silver-based low-temperature and high-thermal-conductivity packaging material with a double-network structure, characterized in that: The method comprises the following preparation steps: S1: According to the weight percentage, 40% to 80% of silver powder, 5% to 20% of a binder, 5% to 20% of an organic solvent and 10% to 20% of a pore-forming agent are uniformly mixed to prepare a slurry, wherein the pore-forming agent is polypropylene; The slurry is coated or rolled to form a film blank, and then the film blank is dried and sintered at high temperature in sequence to obtain a silver material with an array-type porous network structure, wherein the pores in the silver material are directional through holes with a pore size of micro-nanoscale, and the porosity of the silver material is 25% to 95%; in addition, the drying is carried out in a vacuum oven, and the specific processing conditions of the high-temperature sintering are: nitrogen is selected as the protective gas, hydrogen is selected as the reducing gas; and sintering is carried out at 750 to 900° C. for 30 to 120 minutes; S2: heating the low melting point solder to melt to obtain a molten material of the low melting point solder, and controlling the temperature of the molten material of the low melting point solder to be 10° C. to 20° C. higher than its melting point; wherein the low melting point solder is any one of pure tin, Sn-Bi alloy, Sn-In alloy and Sn-Bi-In alloy; Using a coating machine to evenly coat the molten low-melting-point solder on the preheated silver material, so that the molten low-melting-point solder fills all the through holes on the silver material and evenly coats the surface of the silver material; The silver material coated with the molten material of the low melting point solder is subjected to roller pressing by using a roller press to obtain a silver-based low temperature and high thermal conductivity packaging material with a double network structure.

2. The method for preparing the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 1, characterized in that: The porosity of the silver material is preferably 50% to 90%.

3. The method for preparing the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 1, characterized in that: In the silver material, the through holes are two-dimensional or three-dimensional through holes with an average pore diameter of 2 to 200 μm.

4. The method for preparing the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 1, characterized in that: The silver-based low-temperature and high-thermal-conductivity packaging material is in a sheet-like structure as a whole, and its thickness is 0.01 to 2 mm.

5. The method for preparing the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 1, characterized in that: The temperature of the preheated silver material is the same as the temperature of the molten material of the low melting point solder.

6. The method for preparing the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 1, characterized in that: The coating process conditions of the coating machine are as follows: the coating conveying speed is 0.3-1 m / min; the width of the coating machine roller is 200-600 mm; The processing conditions of the rolling process are as follows: the rolling rollers are made of polytetrafluoroethylene material, and the gap between the rolling rollers is 0.01-2 mm.

7. A double network structure silver-based low-temperature and high thermal conductivity packaging material, characterized in that: The double network structure silver-based low-temperature and high thermal conductivity packaging material is manufactured by the preparation method of any one of claims 1 to 6.

8. Use of the double network structure silver-based low-temperature and high thermal conductivity packaging material according to claim 7 as solder for semiconductor packaging.

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