Silver solder paste, its manufacturing method and applications

Abstract

The present invention relates to a silver solder paste and its manufacturing method and applications, belonging to the technical field of device packaging. The silver solder paste of the present invention is prepared from a silver ammine complex solution and an aldehyde-based organic solvent, with the molar ratio of the silver ammine complex solution to the aldehyde-based organic solvent being 1:1 to 1:5, and the silver ammine complex is prepared from a silver ketocarboxylate and an amino-based organic solvent, with the molar ratio of the silver ketocarboxylate to the amino-based organic solvent being 1:1 to 1:5. The silver solder paste of the present invention can be used to solder large areas (≥30 × 30 cm) at 300°C or below under low pressure (≤1 MPa) or no pressure conditions. 2 ) can be realized in packaging interconnections for wide bandgap semiconductor devices. The bonding layer formed by sintering this silver solder paste has good bonding strength at the bonding interface, is uniform, dense, and has a high shear strength of 35 MPa, making it suitable for use in large-area packaging interconnections for electronic devices.

Description

[Technical Field]

[0001] The present invention relates to the technical field of device packaging, and in particular to a silver solder paste and its manufacturing method and application. [Background technology]

[0002] As the power performance and driving range of electric vehicles continue to improve, wide bandgap semiconductor devices, which are the core of motor drive control systems, must not only adapt to the high temperature and strong vibration operating environment of electric vehicles, but also cope with the harsh conditions of large temperature differences and large current stress shocks caused by frequent start-stop cycles in a complex electrical, thermal, and mechanical stress environment in order to ensure the three attributes of electric vehicles: strong power, high efficiency, and safety and reliability.

[0003] In the packaging structure of wide bandgap semiconductor devices, packaging interconnect materials determine the electrical characteristics of the device, as well as its heat dissipation characteristics and reliability during long-term use, and are key to high-reliability, long-life, and temperature-resistant operation of electric vehicle motor drive control systems. From the perspective of the thermal, electrical, and mechanical performance of the bonding interface of wide bandgap semiconductor devices and their packaging process, low-temperature sintering interconnect technologies, represented by micro- and nano-silver solder paste, have been widely developed.

[0004] However, because wide-bandgap semiconductor devices have higher current carrying capacity and lower impedance, their heat dissipation requirements are much higher than those of conventional silicon devices. Conventional small-area bonding cannot meet these heat dissipation needs, creating an urgent need for the development of interconnect materials suitable for large-area bonding. While silver sintering technology has already been successfully applied in the field of small-area interconnects, large-area interconnect processes typically require physical means, such as increasing the sintering temperature and sintering pressure, to improve the sintering driving force. Increasing the sintering temperature and pressure not only increases processing difficulty and increases equipment requirements, but can also cause chip damage, reducing product yield and increasing costs. Therefore, developing a new silver solder paste that can be sintered and densified under low-temperature and low-pressure conditions is key to achieving large-area bonding. Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of the present invention is to provide a silver solder paste and its manufacturing method and applications to overcome the drawbacks of the prior art. The present invention is capable of forming wide bandgap semiconductor devices with a large area (≥ 30 × 30 cm) under low sintering pressure (0-1 MPa) and low sintering temperature (200-300°C). 2 ) packaging and interconnection can be well realized.

[0006] To achieve the above object, the present invention adopts the following technical solutions. In a first aspect, the present invention provides a silver solder paste prepared from a silver ammine complex solution and an aldehyde-based organic solvent (R1-CHO, where R1 is a hydrocarbon group), wherein the molar ratio of the silver ammine complex solution to the aldehyde-based organic solvent is 1:1 to 1:5; and the silver ammine complex solution is prepared from a silver ketocarboxylate and an amino-based organic solvent, wherein the molar ratio of the silver ketocarboxylate to the amino-based organic solvent is 1:1 to 1:5.

[0007] In a preferred embodiment of the silver solder paste according to the present invention, the molar ratio of the silver ammine complex solution to the aldehyde group organic solvent is 1:2 to 1:4, and the molar ratio of the silver ketocarboxylate to the amino group organic solvent is 1:2 to 1:4.

[0008] In the present invention, silver ketocarboxylate (C4H5O4Ag) has both an aldehyde group (-CHO) and a carboxylic acid group (-COOH), and is reacted with an amino-based organic solvent and a silver ammine complex ([Ag(R2NH2)2] + , R2 is a hydrocarbon group.) The silver ammine complex has high activity, effectively prevents the aggregation of nanoparticles during the sintering process, improves the sintering density, and can be used for wide bandgap semiconductor devices with a large area (≥30 × 30 cm). 2 ) can reduce the sintering temperature and pressure. In addition, the aldehyde-based organic solvent and the silver ammine complex undergo a silver mirror reaction, accelerating the decomposition of the silver solder paste. The resulting silver particles can reduce the porosity of the silver solder paste, further improving the sintering density. In addition, the aldehyde-based organic solvent has strong reducing properties and is decomposed by self-oxidation, suppressing oxidation of the substrate and preventing the generation of sintering residues, making it possible to manufacture wide bandgap semiconductor devices with large areas (≥ 30 × 30 cm). 2 ) further reduces the sintering temperature and pressure.

[0009] In the present invention, the molar ratio of silver ketocarboxylate to amino organic solvent and the molar ratio of silver ammine complex solution to aldehyde organic solvent both affect the performance of the silver solder paste. When the molar ratio is 1:2, the silver ketocarboxylate and the amino group form a highly active saturated silver ammine complex, which is more susceptible to decomposition during sintering. If the molar ratio of silver ketocarboxylate to amino organic solvent is too low, a saturated silver ammine complex cannot be formed. If the molar ratio of silver ketocarboxylate to amino organic solvent is too high, excessive amino solvent is introduced, causing organic matter to remain during sintering. If the molar ratio of silver ammine complex solution to aldehyde organic solvent is too low, the driving force of the silver solder paste is low and it cannot be fully decomposed. If the molar ratio of silver ammine complex solution to aldehyde organic solvent is too high, the amount of organic solvent is too high, resulting in a low solids content in the solder paste, which is unfavorable for forming interconnect structures by application. According to the present inventors, it is preferred that the molar ratio of silver ketocarboxylate to amino-based organic solvent is 1:2, and the molar ratio of silver ammine complex solution to aldehyde-based organic solvent is 1:1.

[0010] In a preferred embodiment of the silver solder paste according to the present invention, the aldehyde-based organic solvent is an aliphatic aldehyde having less than 12 carbon atoms.

[0011] Preferably, the aldehyde-based organic solvent is at least one of acetaldehyde, propionaldehyde, and butyraldehyde.

[0012] The selection of the above aldehyde-based organic solvent is advantageous in improving the performance of the silver solder paste and in improving the adhesive strength of the semiconductor device.

[0013] In a preferred embodiment of the silver solder paste according to the present invention, the amino group organic solvent has 10 or less carbon atoms.

[0014] Preferably, the amino organic solvent is at least one of 2-amino-2-methyl-1-propanol, 2-isopropylamine, ethanolamine, and hexylamine, which can provide a silver ammine complex with more stable performance and is advantageous for improving the density of the packaging interconnect structure of wide bandgap semiconductor devices.

[0015] In a second aspect, the present invention provides a method for producing the silver solder paste described above, comprising: Step S1: uniformly mixing a silver ketocarboxylate and an amino-functional organic solvent to obtain a silver ammine complex solution; Step S2: uniformly mixing the silver ammine complex solution obtained in step S1 with an aldehyde-based organic solvent to obtain a silver solder paste; The present invention provides a method of manufacturing a semiconductor device, comprising:

[0016] In a third aspect, the present invention provides the use of the above silver solder paste in a packaging interconnect structure for wide bandgap semiconductor devices.

[0017] Preferably, the packaging interconnect structure for the wide bandgap semiconductor device includes an upper substrate, a lower substrate, and a bonding layer for bonding the upper substrate and the lower substrate, and the bonding layer is sintered by a sintering process using the above-mentioned silver solder paste.

[0018] Preferably, the sintering temperature is 200 to 300° C., the sintering time is 10 to 30 minutes, and the sintering pressure is 0 to 1 MPa.

[0019] Preferably, the upper or lower substrate includes a copper plate, a gold plate, a silver plate, a ceramic plate whose surface is coated with copper, gold or silver, or a silicon plate and a functional device.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The silver solder paste of the present invention can be easily soldered to a large area (≧30×30 cm) at 300°C or less under low pressure (≦1 MPa) or no pressure. 2 ) can be realized in packaging interconnections for wide bandgap semiconductor devices. The bonding layer formed by sintering this silver solder paste has good bonding strength at the bonding interface, is uniform, dense, and has a high shear strength of 35 MPa, making it suitable for use in large-area packaging interconnections for electronic devices. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a flowchart showing the production of a silver-ammine composite solder paste according to the present invention. [Figure 2] 1 is a scanning electron microscope photograph of a cross section of a sintered body of a silver-ammine composite solder paste according to the present invention. [Figure 3] 1 is a flowchart showing the application of the silver-ammine composite solder paste of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to better explain the objectives, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific examples and comparative examples. However, this description is intended to facilitate a detailed understanding of the present invention and is not intended to limit the present invention. All other examples obtained by those skilled in the art without any creative effort are within the scope of the present invention. The experimental reagents and equipment used in carrying out the present invention are common reagents and equipment unless otherwise specified.

[0023] The raw materials used in the examples and comparative examples will be described below. Silver ketocarboxylate: Its chemical name is silver β-methylacetoacetate and its chemical formula is C4H5O4Ag. In the present invention, silver β-methylacetoacetate is prepared according to the published literature: Mariko Hatamura, Shunro Yamaguchi, Shin-ya Takane, Yu Chenb and Katuaki Suganuma, "Decarboxylation and simultaneous reduction of silver(i) β-ketocarboxylates with three types of coordinations," Dalton Trans., 2015, 44, 8993-9003, doi:10.1039 / C5DT00773A.

[0024] Example 1 Preparation of silver solder paste: Silver ketocarboxylate and ethanolamine were mixed uniformly at room temperature in a molar ratio of 1:1 to obtain a solution of an unsaturated silver ammine complex. The unsaturated silver ammine complex solution was then mixed with acetaldehyde in a molar ratio of 1:1 and ultrasonically mixed for 30 minutes in an ultrasonic machine to obtain a silver solder paste.

[0025] The silver solder paste prepared above was applied to the packaging interconnection structure of electronic devices. Pure copper substrates were selected as the upper and lower substrates in the packaging interconnection structure, and the area of ​​the upper substrate was 30 × 30 cm. 2 The area of ​​the lower substrate is 35 × 35 cm 2 The specific steps were as follows: S1: Substrate treatment: The pure copper substrates (upper and lower substrates) were polished with abrasive paper to remove the copper oxide layer on the surfaces of the pure copper substrates. The polished pure copper substrates were then ultrasonically cleaned in absolute ethanol for 2 minutes to remove impurities from their surfaces. They were then placed in a vacuum drying box and dried at 60°C for 3 minutes to remove the absolute ethanol. S2: The silver solder paste produced in this example was uniformly applied by screen printing to the joining surface of the lower substrate obtained in step S1 to a thickness of 8 μm. Thereafter, the joining surface of the upper substrate obtained in step S1 was bonded to the silver solder paste of the lower substrate, forming a laminated structure of upper substrate-silver solder paste-lower substrate. S3: The laminated structure of upper substrate-silver solder paste-lower substrate obtained in step S2 was placed in a pressure sintering furnace, heated to 250°C at a heating rate of 10°C / min, and maintained at 250°C for 30 minutes without pressure, so that the silver solder paste coating layer was sintered to form a bonding layer, and then naturally cooled to obtain a packaging interconnection structure.

[0026] The interconnect structure is 5 x 5 cm 2 The interconnect structure was divided into small blocks, the lower substrate was fixed, and the upper substrate was pressed using a push head.The force required to destroy the interconnect structure was approximately 500 N, and when this was divided by the bonding area, it was found that the bonding layer formed by sintering the silver solder paste of this example had a shear strength of 20±2 MPa after cooling.

[0027] Example 2 Preparation of silver solder paste: Silver ketocarboxylate and hexylamine were mixed uniformly at room temperature in a molar ratio of 1:3 to obtain a saturated solution of silver ammine complex. The saturated solution of silver ammine complex was then mixed with acetaldehyde in a molar ratio of 1:1 and ultrasonically mixed for 30 minutes in an ultrasonic machine to obtain a silver solder paste.

[0028] The silver solder paste prepared above was applied to the packaging interconnection structure of electronic devices. Pure copper substrates were selected as the upper and lower substrates in the packaging interconnection structure, and the area of ​​the upper substrate was 30 × 30 cm. 2 The area of ​​the lower substrate is 35 × 35 cm 2 The specific steps were as follows: S1: Substrate treatment: The pure copper substrates (upper and lower substrates) were polished with abrasive paper to remove the copper oxide layer on the surfaces of the pure copper substrates. The polished pure copper substrates were then ultrasonically cleaned in absolute ethanol for 2 minutes to remove impurities from their surfaces. They were then placed in a vacuum drying box and dried at 60°C for 3 minutes to remove the absolute ethanol. S2: The silver solder paste produced in this example was uniformly applied by screen printing to the joining surface of the lower substrate obtained in step S1 to a thickness of 10 μm. Thereafter, the joining surface of the upper substrate obtained in step S1 was bonded to the silver solder paste of the lower substrate, forming a laminated structure of upper substrate-silver solder paste-lower substrate. S3: The laminated structure of upper substrate-silver solder paste-lower substrate obtained in step S2 was placed in a pressure-assisted sintering furnace, heated to 280°C at a heating rate of 10°C / min, and maintained at 280°C and 0.5 MPa for 30 minutes, until the silver solder paste coating layer was sintered to form a bonding layer, after which it was allowed to cool naturally to obtain a packaging interconnect structure.

[0029] The interconnect structure is 5 x 5 cm 2 The interconnect structure was divided into small blocks, the lower substrate was fixed, and the upper substrate was pressed using a push head.The force required to destroy the interconnect structure was approximately 620 N, and when this was divided by the bonding area, it was found that the bonding layer formed by sintering the silver solder paste of this example had a shear strength of 25±2 MPa after cooling.

[0030] Example 3 Preparation of silver solder paste: Silver ketocarboxylate and 2-amino-2-methyl-1-propanol were mixed uniformly at room temperature in a molar ratio of 1:3 to obtain a saturated solution of silver ammine complex. This saturated solution of silver ammine complex was then mixed with acetaldehyde in a molar ratio of 1:3 and ultrasonically mixed for 30 minutes in an ultrasonic machine to obtain a silver solder paste.

[0031] The silver solder paste prepared above was applied to the packaging interconnection structure of electronic devices. Pure copper substrates were selected as the upper and lower substrates in the packaging interconnection structure, and the area of ​​the upper substrate was 30 × 30 cm. 2 The area of ​​the lower substrate is 35 × 35 cm 2 The specific steps were as follows: S1: Substrate treatment: The pure copper substrates (upper and lower substrates) were polished with abrasive paper to remove the copper oxide layer on the surfaces of the pure copper substrates. The polished pure copper substrates were then ultrasonically cleaned in absolute ethanol for 2 minutes to remove impurities from their surfaces. They were then placed in a vacuum drying box and dried at 60°C for 3 minutes to remove the absolute ethanol. S2: The silver solder paste produced in this example was uniformly applied by screen printing to the joining surface of the lower substrate obtained in step S1 to a thickness of 8 μm. Thereafter, the joining surface of the upper substrate obtained in step S1 was bonded to the silver solder paste of the lower substrate, forming a laminated structure of upper substrate-silver solder paste-lower substrate. S3: The laminated structure of upper substrate-silver solder paste-lower substrate obtained in step S2 was placed in a pressure-assisted sintering furnace, heated to 300°C at a heating rate of 10°C / min, and maintained at 300°C and 0.8 MPa for 30 minutes, until the silver solder paste coating layer was sintered to form a bonding layer, after which it was allowed to cool naturally to obtain a packaging interconnect structure.

[0032] The interconnect structure is 5 x 5 cm 2 The interconnect structure was divided into small blocks, the lower substrate was fixed, and the upper substrate was pressed using a push head.The force required to destroy the interconnect structure was approximately 740 N, and when this was divided by the bonding area, the bonding layer formed by sintering the silver solder paste of this example had a shear strength of 30±2 MPa after cooling.

[0033] Example 4 Preparation of silver solder paste: Silver ketocarboxylate and 2-amino-2-methyl-1-propanol were mixed uniformly at room temperature in a molar ratio of 1:5 to obtain a saturated solution of silver ammine complex. This saturated solution of silver ammine complex was then mixed with acetaldehyde in a molar ratio of 1:5 and ultrasonically mixed for 30 minutes in an ultrasonic machine to obtain a silver solder paste.

[0034] The silver solder paste prepared above was applied to the packaging interconnection structure of electronic devices. Pure copper substrates were selected as the upper and lower substrates in the packaging interconnection structure, and the area of ​​the upper substrate was 30 × 30 cm. 2 The area of ​​the lower substrate is 35 × 35 cm 2 The specific steps were as follows: S1: Substrate treatment: The pure copper substrates (upper and lower substrates) were polished with abrasive paper to remove the copper oxide layer on the surfaces of the pure copper substrates. The polished pure copper substrates were then ultrasonically cleaned in absolute ethanol for 2 minutes to remove impurities from their surfaces. They were then placed in a vacuum drying box and dried at 60°C for 3 minutes to remove the absolute ethanol. S2: The silver solder paste produced in this example was uniformly applied by screen printing to the joining surface of the lower substrate obtained in step S1 to a thickness of 8 μm. Thereafter, the joining surface of the upper substrate obtained in step S1 was bonded to the silver solder paste of the lower substrate, forming a laminated structure of upper substrate-silver solder paste-lower substrate. S3: The laminated structure of upper substrate-silver solder paste-lower substrate obtained in step S2 was placed in a pressure-assisted sintering furnace, heated to 300°C at a heating rate of 10°C / min, and maintained at 300°C and 1 MPa for 30 minutes, sintering the silver solder paste coating layer to form a bonding layer, and then allowed to cool naturally to obtain a packaging interconnect structure.

[0035] Measurements showed that the bonding layer formed by sintering the silver solder paste of this example had a shear strength of 25±5 MPa after cooling.

[0036] Comparative Example 1 This comparative example provides a silver solder paste and its manufacturing method and application, and differs from Example 1 in that the molar ratio of silver ketocarboxylic acid to ethanolamine is 1:0.5.

[0037] The shear strength of the bonding layer obtained in this comparative example was measured according to the measurement method of Example 1 and was found to be 3 MPa.

[0038] Comparative Example 2 This comparative example provides a silver solder paste and its manufacturing method and application, and differs from Example 1 in that the molar ratio of silver ketocarboxylic acid to ethanolamine is 1:5.5.

[0039] As a result, the solids content of the resulting solder paste was too low to be applied to form a viable bond.

[0040] Comparative Example 3 This comparative example provides a silver solder paste and its manufacturing method and application. This comparative example differs from Example 1 in that the molar ratio of the unsaturated silver ammine complex solution to acetaldehyde is 1:0.5.

[0041] The shear strength of the bonding layer obtained in this comparative example was measured according to the measurement method of Example 1 and was found to be 5 MPa.

[0042] Comparative Example 4 This comparative example provides a silver solder paste and its manufacturing method and application. This comparative example differs from Example 1 in that the molar ratio of the unsaturated silver ammine complex solution to acetaldehyde is 1:5.5.

[0043] As a result, the solids content of the resulting solder paste was too low to be applied to form a viable bond.

[0044] Comparative Example 5 This comparative example provides a silver solder paste and its manufacturing method and application. This comparative example differs from Example 1 in that ethanol was used instead of acetaldehyde, and the molar ratio of the unsaturated silver ammine complex solution to ethanol was 1:1.

[0045] As a result, they could not react to synthesize silver nanoparticles and could not sinter to form effective bonds.

[0046] Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and are not intended to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or equivalently substituted without departing from the essence and scope of the technical solution of the present invention.

Claims

1. 1. A silver solder paste, characterized in that the silver solder paste is prepared from a silver ammine complex solution and an aldehyde-based organic solvent, the molar ratio of the silver ammine complex solution to the aldehyde-based organic solvent being 1:1 to 1:5, and the silver ammine complex solution is prepared from a silver ketocarboxylate and an amino-based organic solvent, the molar ratio of the silver ketocarboxylate to the amino-based organic solvent being 1:1 to 1:

5.

2. 2. The silver solder paste according to claim 1, wherein a molar ratio of the silver ammine complex solution to the aldehyde-based organic solvent is 1:2 to 1:4, and a molar ratio of the silver ketocarboxylate to the amino-based organic solvent is 1:2 to 1:

4.

3. 2. The silver solder paste of claim 1, wherein the aldehyde-based organic solvent is an aliphatic aldehyde having less than 12 carbon atoms.

4. 2. The silver solder paste according to claim 1, wherein the amino-group organic solvent has 10 or less carbon atoms.

5. A method for producing the silver solder paste according to any one of claims 1 to 4, comprising: Step S1: uniformly mixing a silver ketocarboxylate and an amino-functional organic solvent at room temperature to obtain a silver ammine complex solution; Step S2: uniformly mixing the silver ammine complex solution obtained in step S1 with the aldehyde-based organic solvent at room temperature to obtain a silver solder paste; A manufacturing method comprising:

6. Use of the silver solder paste according to any one of claims 1 to 4 in a packaging interconnect structure for wide bandgap semiconductor devices.

7. The use of claim 6, wherein the packaging interconnect structure for a wide bandgap semiconductor device comprises an upper substrate, a lower substrate, and a bonding layer for bonding the upper substrate and the lower substrate, and the bonding layer is sintered by a sintering process using the silver solder paste according to any one of claims 1 to 4.

8. The use according to claim 7, characterized in that the sintering temperature is 200-300°C, the sintering time is 10-30 minutes, and the sintering pressure is 0-1 MPa.

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