Sinterable preform, method for its production and use

Abstract

The application provides a sinterable preform and a preparation method and application thereof, and belongs to the technical field of electronic packaging materials.The sinterable preform comprises heat-conducting metal powder, nitrogen-containing heterocyclic polymer, organic carrier and release agent, and contains 0.01-3 parts by weight of the nitrogen-containing heterocyclic polymer, 0.01-3 parts by weight of the organic carrier and 0.01-1 part by weight of the release agent, with the mass of the heat-conducting metal powder being 100 parts; and the organic carrier has a nitrogen-carbon double bond.The sinterable preform is added with the nitrogen-containing heterocyclic polymer and the organic carrier with the nitrogen-carbon double bond, and the two interact to improve the shear strength of a sintered body formed by the sinterable preform.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to a sinterable preform, its preparation method, and its application. Background Technology

[0002] Power devices, represented by third-generation semiconductors, possess characteristics such as high breakdown voltage, high saturated carrier mobility, high thermal stability, high thermal conductivity, and high-temperature operation. Therefore, packaging materials require low-temperature bonding, high-temperature operation, excellent thermal fatigue resistance, high electrical and thermal conductivity, and moderate cost. Sintered silver materials, with their high operating temperature, high thermal conductivity, excellent reliability, and superior mechanical properties, are widely used in high-power device packaging. Sintered silver materials are generally in the form of sintered silver paste. The packaging process for sintered silver materials involves eight steps: refrigeration, rewarming, stirring, printing, preheating, testing, die bonding, and sintering. During use, the paste is applied to the substrate via stencil printing or dispensing, followed by chip mounting. A typical process involves printing the sintering paste onto the substrate, bonding the chips, and then, after a specific temperature profile, performing pressureless or pressure-assisted sintering to achieve the bonding connection between the chip and the substrate. This solution has several drawbacks and cannot be widely applied in industrial production. For example, during printing, silver paste is prone to extrusion and collapse, resulting in inconsistent thickness of the silver layer around the periphery and center after sintering, thus reducing the lifespan of power devices. The solvent in the sintered silver paste system evaporates during heating, creating micron-sized or larger pores in the sintered joint. The formation of these pores can cause hot spots during the service life of the power devices, leading to a mismatch in the coefficient of thermal expansion. Long-term stress can cause delamination and cracking of the sintered metal layer, significantly reducing the service life of the power devices. Furthermore, since the sintered silver paste exists in paste form, silver powder in the system is prone to sedimentation during storage and transportation, resulting in uneven distribution of the silver paste during use. In addition, the use of silver paste is also affected by the aforementioned silver paste printing and pre-drying steps, resulting in poor performance consistency during device packaging. Summary of the Invention

[0003] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a sinterable preform, its preparation method, and its application.

[0004] To achieve the above objectives, the technical solution adopted in this disclosure is as follows: In a first aspect, a sinterable preform is provided, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, the preform contains 0.01-3 parts by weight of the nitrogen-containing heterocyclic polymer, 0.01-3 parts by weight of the organic carrier, and 0.01-1 parts by weight of the release agent; the organic carrier has nitrogen-carbon double bonds.

[0005] This invention incorporates a nitrogen-containing heterocyclic polymer into the sinterable preform, which improves the adhesion between thermally conductive metal powder particles, reduces the brittleness of the sinterable preform, increases its strength, and prevents breakage during assembly and transfer. Furthermore, it increases the effective contact area between the thermally conductive metal powder particles, reduces the porosity of the sintered body, and enhances its shear strength. The nitrogen-carbon double bonds in the organic carrier undergo covalent adsorption with the surface of the thermally conductive metal powder, further increasing the adhesion between the powder particles and improving the density of the sinterable preform, thereby increasing the shear strength of the sintered body formed from the preform.

[0006] Specifically, the weight parts of the nitrogen-containing heterocyclic polymer can be, but are not limited to, 0.01 parts, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, or 3 parts; preferably, 0.5-2.5 parts.

[0007] Specifically, the weight parts of the release agent can be, but are not limited to, 0.01 parts, 0.05 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, or 1 part; preferably 0.2-0.5 parts.

[0008] Specifically, the weight parts of the organic carrier can be, but are not limited to, 0.01 parts, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, or 3 parts; preferably 0.5-2.5 parts.

[0009] When the weight proportions of nitrogen-containing heterocyclic polymer, organic carrier, and release agent are within the preferred range, the resulting sinterable preforms form sintered bodies with higher shear strength.

[0010] In some embodiments, the nitrogen-containing heterocyclic polymer is at least one selected from 2,2,4-trimethyl-1,2-dihydroquinoline homopolymer, morpholinomethyl polystyrene, poly(4-vinylpyridine-co-styrene), and poly-4-vinylpyridine. When the nitrogen-containing heterocyclic polymer is one of the above-mentioned substances, the overall properties of the resulting sinterable preform are improved.

[0011] Specifically, the degree of polymerization of the nitrogen-containing heterocyclic polymer is 100-2000; for example, it can be, but is not limited to, 100, 300, 500, 700, 900, 1200, 1500, 1800, 2000; when the degree of polymerization of the nitrogen-containing heterocyclic polymer is within the above range, the overall performance of the resulting sinterable preform is improved.

[0012] In some embodiments, the nitrogen-containing heterocyclic polymer is morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene), wherein the mass ratio of morpholinomethyl polystyrene to poly(4-vinylpyridine-co-styrene) is (3-10):1, for example, but not limited to 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1; when the nitrogen-containing heterocyclic polymer is morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene) and the mass ratio of morpholinomethyl polystyrene to poly(4-vinylpyridine-co-styrene) is (3-10):1, the shear strength of the sintered body formed by the resulting sinterable preform is higher.

[0013] In some embodiments, the organic carrier is an oxime; preferably, the oxime is a ketoxime.

[0014] In some embodiments, the ketoxime is at least one selected from acetone oxime, cyclopentanone oxime, cyclohexanone oxime, cycloheptanone oxime, cyclooctanone oxime, 3-hydroxy-3-methyl-2-butanone oxime, 3'-(trifluoromethyl)acetophenone oxime, phenylacetone oxime, 1,3-dihydroxyacetone oxime, 4-methylcyclohexanone oxime, cyclobutanone oxime, and 1-(4-fluorophenyl)acetophenone oxime.

[0015] The melting point of the organic carrier is below 100°C. Preferably, the melting point of the organic carrier is 30-80°C, and more preferably, the melting point of the organic carrier is 40-70°C. During the sintering process of the sinterable preform, melting occurs, which promotes the flow between the thermally conductive metal powder particles, increases the contact area between the thermally conductive metal powder particles, increases the sintering density, and reduces the porosity of the sintered body, thereby improving the shear strength of the sintered body formed by the sinterable preform.

[0016] Specifically, the melting point of ketoxime in this invention can be determined using a differential scanning calorimeter (DSC), an example of which is a calorimeter sold by TA Inc. in the United States under the name TA-SDTQ600 Thermal Comprehensive Analyzer.

[0017] The determination procedure is as follows: The ketoxime sample was placed in an aluminum flat-bottomed crucible, with an empty aluminum flat-bottomed crucible as a reference. An endothermic scanning measurement was performed, with the temperature increasing from 25℃ to 150℃ at a scanning rate of 5℃ / min. N2 was used for purging at a flow rate of 100mL / min. The melting point of the ketoxime was determined from the temperature of the endothermic peak.

[0018] In some embodiments, the average particle size of the thermally conductive metal powder is 0.51-20 μm; for example, it can be, but is not limited to, 0.51 μm, 0.55 μm, 0.6 μm, 0.8 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, or 20 μm, preferably 0.6-10 μm. The test method for this average particle size is GB / T 19077-2016. An average particle size of the thermally conductive metal powder within the above range is beneficial for improving the shear strength of the sintered body formed from the sinterable preform.

[0019] In some embodiments, the thermally conductive metal powder is at least one of silver powder, copper powder, gold powder, and silver-coated copper powder; the above-mentioned thermally conductive metal powder has a high operating temperature and thermal conductivity, which is beneficial to improving the sintering rate of the sinterable preform and increasing efficiency.

[0020] In some embodiments, the thermally conductive metal powder is in the shape of at least one of spherical or sheet-like shapes; preferably, the thermally conductive metal powder is in the shape of spherical or sheet-like shapes, with the thermally conductive metal powder particles of different shapes interleaved, which improves the strength of the sinterable preform and reduces its breakage.

[0021] In some embodiments, the release agent is at least one of wax, polysiloxane, and stearate with ≥18 carbon atoms.

[0022] In some embodiments, the wax is at least one of polyethylene wax and polyamide wax.

[0023] In some embodiments, the stearate with ≥18 carbon atoms is at least one of pentaerythritol tetrastearate and pentaerythritol tetraisostearate.

[0024] In some embodiments, the polysiloxane is at least one of carboxyl silicone oil and polyoxyethylene polyoxypropylene ether grafted silicone oil.

[0025] The aforementioned release agent improves the release performance of sinterable preforms, enabling them to be successfully demolded without breaking.

[0026] Secondly, a method for preparing the aforementioned sinterable preform is provided, comprising the following steps:

[0027] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to solvent in proportion and mixed evenly to obtain a mixture.

[0028] The mixture is dried, and the resulting powder is placed in a mold and held at a temperature of 21-25℃ and a pressure of 50-500MPa for 1-60s. The mixture is then demolded to obtain a sinterable preform.

[0029] Specifically, the solvent has a boiling point below 120°C, and may be, for example, but not limited to, ethanol, isopropanol, propanol, ethyl acetate, n-butanol, and isobutanol.

[0030] Specifically, based on the total mass of the thermally conductive metal powder, nitrogen-containing heterocyclic polymer, release agent, and organic carrier as 100%, the mass percentage of the solvent is 3-5%, for example, but not limited to 3%, 3.2%, 3.5%, 3.7%, 4%, 4.3%, 4.5%, 4.8%, and 5%.

[0031] In the preparation of sinterable preforms, during the drying of the mixture, the solvent evaporates, and the organic carrier melts to bond the thermally conductive metal powder particles together. In this way, the thermally conductive metal powders are tightly connected, resulting in a high density of the mixed powder. When the mixed powder is pressed, the thermally conductive metal powder retains its own activity while reducing the gaps between the thermally conductive metal powder particles, which significantly increases the contact area between the thermally conductive metal powder particles and reduces the difficulty of diffusion between thermally conductive metal atoms. This reduces the sintering temperature, sintering pressure, or sintering time of the sinterable preform, and also increases the shear strength of the sintered body, thereby improving the performance and lifespan of the power device.

[0032] To obtain complete sinterable preforms, the mixed powder should be laid as flat as possible when placed in the mold to reduce the thickness difference and porosity of the mixed powder in the mold, thereby improving the density of the sinterable preforms.

[0033] Specifically, the pressure for holding the pressure can be, but is not limited to, 50MPa, 80MPa, 100MPa, 120MPa, 140MPa, 160MPa, 180MPa, 200MPa, 250MPa, 300MPa, 400MPa, or 500MPa; preferably 100-180MPa.

[0034] Specifically, the pressure holding time can be, but is not limited to, 1s, 5s, 10s, 20s, 30s, 40s, 50s, or 60s; preferably 30-50s.

[0035] Holding pressure and time within the above range are beneficial for improving the density of sinterable preforms.

[0036] In some embodiments, the drying temperature is 80-140°C, for example, but not limited to 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, and 140°C; the time is 10-60 minutes, for example, but not limited to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes.

[0037] In this invention, sinterable preforms can be produced using molds of different sizes and shapes as needed; for example, in order to improve the production efficiency of sinterable preforms and reduce production costs, multi-cavity molds can be used to produce multiple products of the same size and shape.

[0038] Thirdly, an encapsulation material, characterized in that the encapsulation material comprises the sinterable preform.

[0039] Fourthly, a method for preparing an encapsulation material includes the following steps: assembling at least one sinterable preform with at least one metal surface of a device to be encapsulated, and sintering the assembly to obtain the encapsulation material.

[0040] Specifically, the sintering temperature is 240-260℃, for example, but not limited to 240℃, 242℃, 245℃, 247℃, 250℃, 253℃, 255℃, 258℃, and 260℃.

[0041] Specifically, the sintering pressure is 10-20 MPa, for example, but not limited to 10 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, and 20 MPa.

[0042] Specifically, the sintering time is 3-8 minutes, for example, but not limited to 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, or 8 minutes.

[0043] Sintering under the above sintering conditions can further ensure that the sinterable preform has a high degree of densification, low porosity, and high shear strength during sintering.

[0044] Fifthly, the sinterable preform or the sinterable preform prepared by the preparation method is used in the sintering of electronic packaging, power device packaging, power batteries, energy storage batteries, automotive radiators, and IGBT module radiators.

[0045] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0046] (1) The present invention adds a nitrogen-containing heterocyclic polymer to the sinterable preform, which can improve the adhesion between thermally conductive metal powder particles, reduce the brittleness of the sinterable preform, improve the strength of the sinterable preform, and prevent the sinterable preform from breaking during assembly and transfer; in addition, it can also increase the effective contact area between thermally conductive metal powder particles, reduce the porosity of the sintered body, and improve the shear strength of the sintered body; the nitrogen-carbon double bonds in the organic carrier will undergo corresponding covalent adsorption with the surface of the thermally conductive metal powder, further increasing the adhesion between the thermally conductive metal powders, improving the density of the sinterable preform, thereby improving the shear strength of the sintered body formed by the sinterable preform.

[0047] (2) During the preparation of the sinterable preform, when the mixture is dried, the solvent evaporates and the organic carrier melts to bond the thermally conductive metal powder particles. In this way, the thermally conductive metal powder is tightly connected and the density of the mixed powder is increased. When the mixed powder is pressed, the thermally conductive metal powder retains its own activity while reducing the gap between the thermally conductive metal powder particles, which greatly increases the contact area between the thermally conductive metal powder particles and reduces the diffusion difficulty between thermally conductive metal atoms. This reduces the sintering temperature, sintering pressure or sintering time of the sinterable preform, and also increases the shear strength of the sintered body, thereby improving the performance and life of the power device.

[0048] (3) The sinterable preform prepared by the present invention is easy to assemble, eliminates the coating and pre-baking process, is convenient to operate, and improves efficiency.

[0049] (4) The sintering temperature of the sinterable preform of the present invention is low, which avoids the harmful substances that may be generated during high-temperature sintering, thereby improving environmental protection and safety. Attached Figure Description

[0050] Figure 1 This is an appearance view of the sinterable preform obtained in Example 3. Detailed Implementation

[0051] To facilitate understanding of this disclosure, a more complete description will be provided below. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0052] As used in this article:

[0053] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0054] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0055] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1-5” is disclosed, the described range should be interpreted as including ranges “1-4”, “1-3”, “1-2”, “1-2 and 4-5”, “1-3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0056] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0057] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has 'a' parts by mass and component B has 'b' parts by mass, it means that the mass ratio of component A to component B is a:b. It is important to understand that, unlike mass percentage content, the sum of the mass parts of all components is not limited to 100 parts.

[0058] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0059] The raw materials used in the following examples and comparative examples were all purchased from Aladdin.

[0060] Example 1

[0061] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0062] The method for preparing sinterable preforms in this embodiment includes the following steps:

[0063] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0064] The resulting mixture was dried at 140°C for 30 minutes to obtain a mixed powder. The mixed powder was spread evenly in a mold and held under pressure at 25°C and 100MPa for 50 seconds before demolding to obtain a sinterable preform.

[0065] Examples 2-18 refer to the examples, and the differences between them and Example 1 are shown in Table 1.

[0066] Table 1

[0067]

[0068] Example 19

[0069] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 0.5 parts by weight of the nitrogen-containing heterocyclic polymer, 2.5 parts by weight of the organic carrier, and 0.2 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0070] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0071] Example 20

[0072] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 2.5 parts by weight of the nitrogen-containing heterocyclic polymer, 0.5 parts by weight of the organic carrier, and 0.5 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0073] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0074] Example 21

[0075] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 3 parts by weight of the nitrogen-containing heterocyclic polymer, 0.01 parts by weight of the organic carrier, and 0.01 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0076] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0077] Example 22

[0078] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 0.01 parts by weight of the nitrogen-containing heterocyclic polymer, 3 parts by weight of the organic carrier, and 1 part by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0079] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0080] Example 23

[0081] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of spherical copper powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is hydroxyl silicone oil.

[0082] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0083] Example 24

[0084] This embodiment provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of spherical copper powder with an average diameter of 0.8 μm, spherical silver powder with an average diameter of 0.8 μm, and spherical gold powder with an average particle size of 2 μm. The mass ratio of the flake silver powder to the spherical silver powder is 2:7:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is polyethylene wax.

[0085] The preparation method of the sinterable preform in this embodiment is the same as that in Example 1.

[0086] Example 25

[0087] This embodiment provides a sinterable preform with the same composition as in Embodiment 1.

[0088] The method for preparing sinterable preforms in this embodiment includes the following steps:

[0089] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0090] The resulting mixture was dried at 140°C for 30 min to obtain a mixed powder; the resulting mixture was spread evenly in a mold, held under pressure at 25°C and 180 MPa for 30 s, and then demolded to obtain a sinterable preform.

[0091] Example 26

[0092] This embodiment provides a sinterable preform with the same composition as in Embodiment 1.

[0093] The method for preparing sinterable preforms in this embodiment includes the following steps:

[0094] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0095] The resulting mixture was dried at 140°C for 30 minutes to obtain a mixed powder. The mixed powder was then spread evenly in a mold and held under pressure at 25°C and 50 MPa for 60 seconds before demolding to obtain a sinterable preform.

[0096] Example 27

[0097] This embodiment provides a sinterable preform with the same composition as in Embodiment 1.

[0098] The method for preparing sinterable preforms in this embodiment includes the following steps:

[0099] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0100] The resulting mixture was dried at 140°C for 30 minutes to obtain a mixed powder. The mixed powder was then spread evenly in a mold and held under pressure at 25°C and 50 MPa for 60 seconds before demolding to obtain a sinterable preform.

[0101] Example 28

[0102] This embodiment provides a sinterable preform with the same composition as in Embodiment 1.

[0103] The method for preparing sinterable preforms in this embodiment includes the following steps:

[0104] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0105] The resulting mixture was dried at 140°C for 30 minutes to obtain a mixed powder. The mixed powder was then spread evenly in a mold and held under pressure at 25°C and 500MPa for 3 seconds before demolding to obtain a sinterable preform.

[0106] Comparative Example 1

[0107] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 3 parts by weight of the nitrogen-containing heterocyclic polymer and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The release agent is pentaerythritol tetrastearate.

[0108] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0109] Comparative Example 2

[0110] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it contains 3 parts by weight of the organic carrier and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0111] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0112] Comparative Example 3

[0113] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is polyvinyl alcohol. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0114] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0115] Comparative Example 4

[0116] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is ethyl cellulose. The organic carrier is cycloheptanone oxime with a melting point of 22-23 °C, and the release agent is pentaerythritol tetrastearate.

[0117] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0118] Comparative Example 5

[0119] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is ethanol, and the release agent is pentaerythritol tetrastearate.

[0120] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0121] Comparative Example 6

[0122] This comparative example provides a sinterable preform, comprising thermally conductive metal powder, a nitrogen-containing heterocyclic polymer, an organic carrier, and a release agent. Based on 100 parts by weight of the thermally conductive metal powder, it comprises 1.5 parts by weight of the nitrogen-containing heterocyclic polymer, 1.5 parts by weight of the organic carrier, and 0.3 parts by weight of the release agent. The thermally conductive metal powder is a mixture of flake-shaped silver powder with an average diameter of 0.8 μm and spherical silver powder with an average diameter of 0.8 μm, with a mass ratio of flake-shaped silver powder to spherical silver powder of 1:1. The nitrogen-containing heterocyclic polymer is morpholinomethyl-polystyrene. The organic carrier is terpineol, and the release agent is pentaerythritol tetrastearate.

[0123] The preparation method of the sinterable preform in this comparative example is the same as that in Example 1.

[0124] Comparative Example 7

[0125] This comparative example provides a sinterable preform with the same composition as Example 1.

[0126] The comparative method for preparing sinterable preforms includes the following steps:

[0127] Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to propanol in proportion and mixed evenly to obtain a mixture; based on the total mass of thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier as 100%, the mass percentage of propanol is 3%;

[0128] The resulting mixture was dried at 140°C for 30 minutes to obtain a mixed powder. The mixed powder was then spread evenly in a mold and held under pressure at 25°C and 30MPa for 80 seconds before demolding to obtain a sinterable preform.

[0129] Performance testing

[0130] The sinterable preforms obtained in the examples and comparative examples were subjected to performance tests. The test method is as follows: The sinterable preform was placed on a gold-plated DBC substrate, and then a 3mm gold-plated chip was attached to the sinterable preform. Hot pressing and sintering were performed at 250℃ and 15MPa for 1 min to obtain a sandwich-like packaging structure of DBC / silver sintered layer / chip. Shear strength was tested using an in-situ dynamic mechanical testing system at a test speed of 0.5mm / s and a test height of 10μm. Five parallel test samples were tested, and the average shear strength is shown in Table 2.

[0131] Table 2

[0132]

[0133]

[0134] As can be seen from the experimental data in Table 1, the shear strength of the sinterable preform obtained in this application is ≥33MPa, indicating that the sintered body formed by the sinterable preform of this application has high shear strength.

[0135] Comparing the experimental data of Examples 1-7, it can be seen that when the melting point of the organic carrier is 30-80℃, the shear strength of the sintered body formed by the obtained sinterable preform is ≥65MPa; when the melting point of the organic carrier is 40-70℃, the shear strength of the sintered body formed by the obtained sinterable preform is ≥70MPa. This indicates that when the melting point of the organic carrier is 30-80℃, the shear strength of the sintered body formed by the sinterable preform can be improved, and when the melting point of the organic carrier is 40-70℃, the shear strength of the sintered body formed by the sinterable preform can be further improved.

[0136] Comparing the experimental data of Example 3 and Example 8, it can be seen that when the organic support is ketoxime, the shear strength of the sintered body formed by the obtained sinterable preform is ≥70MPa; indicating that when the organic support is ketoxime, the shear strength of the sintered body formed by the obtained sinterable preform is high.

[0137] Comparing the experimental data of Examples 5 and 9-13, it can be seen that when the nitrogen-containing heterocyclic polymer is morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene), and the mass ratio of morpholinomethyl polystyrene to poly(4-vinylpyridine-co-styrene) is (3-10):1, the shear strength of the sintered body formed by the obtained sinterable preform is ≥75MPa. This indicates that when the nitrogen-containing heterocyclic polymer is morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene), and the mass ratio of morpholinomethyl polystyrene to poly(4-vinylpyridine-co-styrene) is (3-10):1, the shear strength of the sintered body formed by the sinterable preform can be further improved.

[0138] Comparing the experimental data of Example 5 and Examples 14-18, it can be seen that when the average particle size of silver powder is 0.6-10 μm, the shear strength of the sintered body formed by the obtained sinterable preform is ≥70 MPa; indicating that when the average particle size of silver powder is 0.6-10 μm, the shear strength of the sintered body formed by the sinterable preform can be improved.

[0139] Comparing the experimental data of Example 1 and Examples 19-22, it can be seen that when the weight parts of the nitrogen-containing heterocyclic polymer are 0.5-2.5 parts, the weight parts of the release agent are 0.2-0.5 parts, and the weight parts of the organic carrier are 0.5-2.5 parts, the shear strength of the sintered body formed by the obtained sinterable preform is ≥54MPa. This indicates that when the weight parts of the nitrogen-containing heterocyclic polymer are 0.5-2.5 parts, the weight parts of the release agent are 0.2-0.5 parts, and the weight parts of the organic carrier are 0.5-2.5 parts, the shear strength of the sintered body formed by the sinterable preform can be improved.

[0140] Comparing the experimental data of Example 1 and Examples 25-28, it can be seen that when the pressing pressure is 50-180MPa and the time is 30-60s, the shear strength of the sintered body formed by the sinterable preform is ≥40MPa; indicating that when the pressing pressure is 50-180MPa and the time is 30-60s, the shear strength of the sintered body formed by the sinterable preform can be further improved.

[0141] Comparing the experimental data of Example 1 and Comparative Examples 1-6, it can be seen that without an organic carrier or nitrogen-containing heterocyclic polymer, or by using polyvinyl alcohol or ethyl cellulose to replace the nitrogen-containing heterocyclic polymer, or by using ethanol or terpineol as the organic carrier, the shear strength of the sintered body formed from the sinterable preform is ≤32MPa. This indicates that only the synergistic effect of the organic carrier and the nitrogen-containing heterocyclic polymer can improve the shear strength of the sintered body formed from the sinterable preform.

[0142] Comparing the experimental data of Example 1 and Comparative Example 7, it can be seen that during the preparation of the sinterable preform, the pressing pressure and time are not within the protection scope of this application, and the shear strength of the sintered body formed by the obtained sinterable preform is ≤32MPa; indicating that only within the pressing pressure and time range of this application can the sintered body formed by the obtained sinterable preform have high shear strength.

[0143] Figure 1 This is an appearance view of the sinterable preform obtained in Example 3. Figure 1 As can be seen from the above, the preformable sintered sheet of the present invention has a smooth surface and uniform thickness.

[0144] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this disclosure and not to limit the scope of protection of this disclosure. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the substance and scope of the technical solutions of this disclosure.

Claims

1. A sinterable preform, characterized in that, It includes thermally conductive metal powder, nitrogen-containing heterocyclic polymer, organic carrier and release agent, and based on 100 parts by weight of thermally conductive metal powder, it contains 0.01-3 parts by weight of nitrogen-containing heterocyclic polymer, 0.01-3 parts by weight of organic carrier and 0.01-1 parts by weight of release agent; The organic carrier is an oxime with a melting point ≤100℃; The nitrogen-containing heterocyclic polymer is at least one of 2,2,4-trimethyl-1,2-dihydroquinoline homopolymer, morpholinomethyl polystyrene, poly(4-vinylpyridine-co-styrene), and poly-4-vinylpyridine.

2. The sinterable preform as described in claim 1, characterized in that, The nitrogen-containing heterocyclic polymer is morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene), and the mass ratio of morpholinomethyl polystyrene and poly(4-vinylpyridine-co-styrene) is (3-10):

1.

3. The sinterable preform as described in claim 1, characterized in that, The average particle size of the thermally conductive metal powder is 510 nm-20 μm; And / or, the thermally conductive metal powder is at least one of silver powder, copper powder, gold powder, and silver-coated copper powder; And / or, the thermally conductive metal powder is in the shape of at least one of spherical or sheet-like.

4. The sinterable preform as described in claim 3, characterized in that, The average particle size of the thermally conductive metal powder is 0.6-10 μm.

5. The sinterable preform as described in claim 1, characterized in that, The oxime is a ketoxime.

6. The sinterable preform as described in claim 5, characterized in that, The ketoxime is at least one selected from acetone oxime, cyclopentanone oxime, cyclohexanone oxime, cycloheptanone oxime, cyclooctanone oxime, 3-hydroxy-3-methyl-2-butanone oxime, 3'-(trifluoromethyl)acetophenone oxime, phenylacetone oxime, 1,3-dihydroxyacetone oxime, 4-methylcyclohexanone oxime, cyclobutanone oxime, and 1-(4-fluorophenyl)acetophenone oxime.

7. The sinterable preform as described in claim 1, characterized in that, The release agent is at least one of wax, polysiloxane, and stearate with ≥18 carbon atoms.

8. The sinterable preform as described in claim 7, characterized in that, The wax is at least one of polyethylene wax and polyamide wax; And / or, the stearate with ≥18 carbon atoms is at least one of pentaerythritol tetrastearate and pentaerythritol tetraisostearate; And / or, the polysiloxane is at least one of carboxyl silicone oil and polyoxyethylene polyoxypropylene ether grafted silicone oil.

9. A method for preparing a sinterable preform as described in any one of claims 1-8, characterized in that, Includes the following steps: Thermally conductive metal powder, nitrogen-containing heterocyclic polymer, mold release agent and organic carrier are added to solvent in proportion and mixed evenly to obtain a mixture. The mixture is dried, and the resulting powder is placed in a mold and held at a temperature of 21-25℃ and a pressure of 50-500MPa for 1-60s. The mixture is then demolded to obtain a sinterable preform.

10. The method for preparing a sinterable preform as described in claim 9, characterized in that, The pressure held is 100-180 MPa, and the holding time is 30-50 seconds; And / or, the drying temperature is 80-140℃ and the time is 10-60 min.

11. An encapsulation material, characterized in that, The encapsulation material includes the sinterable preform as described in any one of claims 1-8 or the sinterable preform prepared by any one of claims 9-10.

12. The method for preparing the encapsulation material as described in claim 11, characterized in that, The process includes the following steps: assembling at least one sinterable preform with at least one metal surface of the device to be packaged, and sintering the assembly to obtain a packaging material.

13. The application of the sinterable preform as described in any one of claims 1-8 or the sinterable preform prepared by any one of claims 9-10 in the sintering of electronic packaging, power batteries, energy storage batteries, automotive radiators or IGBT module radiators.

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