Paste-like bonding material composition and bond

Abstract

To provide a paste-like bonding material which has a paste shape, can be used for a bonded article excellent in heat resistance, can provide a bonding method capable of usage in the conventional reflow apparatus and, moreover, permitting such bonding as to cause no failure of void or else on a bonded article, and to provide the bonded article using the bonding material.SOLUTION: A paste-like bonding material composition contains low-melting point metal particles and high-melting point metal particles. Therein, the high-melting point metal particles are contained in a paste-like bonding material composition in such a state that the high-melting point metal particles are treated by a metal inactivating agent, preferably, the low-melting point metal particles are lead-free solder alloy and the high-melting point metal particles are Cu, Ni, Cu-Ni alloy, and one kind or more selected from a group of Cu-Co alloy.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a paste-like bonding material, a paste-like bonding material composition used for bonding electronic components and the like, and a bonded body using the paste-like bonding material composition.

Background Art

[0002] Conventionally, silicon (Si) has been widely used for semiconductor elements. In recent years, materials such as silicon carbide (SiC), which have been recognized for their good characteristics but have been slow to spread due to cost and other issues, have begun to spread. And, as bonding materials for these semiconductors, high-temperature lead-containing solder materials containing 80% or more of lead having bonding reliability at high temperatures and sintered type bonding materials using fine particles of silver or copper have been studied. However, high-temperature lead-containing solder materials have environmental load problems, and sintered type bonding materials using fine particles of silver or copper have issues of cost and technology establishment.

[0003] On the other hand, for conventional diffusion bonding methods, a method of mixing solder particles and metal particles, processing them into a paste-like shape, and melting and bonding them in a reflow furnace or the like has been studied. However, in conventional solder pastes that mix solder particles, metal particles, and flux, solder particles or metal particles may oxidize during the manufacturing process or the soldering process, resulting in non-wetting of the solder particles or metal particles. Also, since the diffusion of metal particles in the bonding layer may proceed rapidly, there may be insufficient adhesion to the base material. As a result, voids or oxide film layers are formed inside the solder bonded body, the diffusion of metal elements and composition does not proceed, and the problem remains that intermetallic compounds are not uniformly formed inside the solder bonded body after bonding.

[0004] Therefore, bonding methods such as those in Patent Document 1 and Patent Document 2 have been proposed. Patent Document 1 discloses a technology that provides a heat-resistant bond at a price equivalent to conventional lead-free solder materials by providing a two-layer bonding layer between a semiconductor chip and a Cu wiring, with a Cu3Sn intermetallic compound on the Cu wiring side and a (Cu,Ni)6Sn5 intermetallic compound on the semiconductor chip side. Patent Document 2 relates to a solder preform for forming a diffusion solder joint, A solder preform is manufactured in which intermetallic compounds are pre-dispersed within the preform at intervals greater than a certain minimum, and a solder preform is manufactured in which the intermetallic compounds rapidly diffuse and stabilize throughout the entire bonding layer when the solder preform melts and forms a solder joint during the soldering process is disclosed.

[0005] However, Patent Document 1 requires the formation of two types of intermetallic compounds in the bonding layer, and Patent Document 2 also requires the formation of intermetallic compounds in the solder preform beforehand, which presents the problem of complicating the manufacturing method of the bonding material and the soldering process itself.

[0006] Furthermore, Patent Document 2 is insufficient in eliminating non-wetting caused by the oxide film of metal particles contained in the solder preform, and because it is in the form of a solder preform, there are limitations on the objects to be joined and the joining conditions. Therefore, there is a need for a joining material that can be used universally like solder paste, provides a soldered joint with excellent heat resistance, and is inexpensive, as well as a joining method using such a joining material. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-155761 [Patent Document 2] Japanese Patent Publication No. 2020-518457 [Overview of the project] [Problems that the invention aims to solve]

[0008] In view of the above circumstances, the present invention provides a bonding material having a paste-like form, wherein the bonded body using the bonding material has excellent heat resistance. 、 Furthermore, the objective is to provide a paste-like bonding material that enables bonding without defects such as voids in the joint, and a joint using said bonding material. [Means for solving the problem]

[0009] In order to solve the aforementioned problems, the present invention investigated a method to prevent oxidation of metal particles intended for diffusion contained in a paste-like bonding material. As a result, it was found that by pre-treating the metal particles with a specific metal deactivator, oxidation of the metal particles can be suppressed in the manufacturing process of the paste-like bonding material and in the bonding process using the bonding material. This allows the metal particles to diffuse within the bonded body without causing non-wetting during bonding, rapidly forming intermetallic compounds, and also allows for a reduction in the reaction rate, prioritizing compatibility with the base material. This led to the completion of the present invention. [Effects of the Invention]

[0010] The paste-like bonding material composition of the present invention and the bonded body using this bonding material exhibit fewer defects such as voids caused by non-wetting of metal particles present inside the bonded body during bonding, and have excellent heat resistance because intermetallic compounds are widely present inside the bonded body after bonding. Moreover, they can be provided at a cost not significantly different from conventional solder materials, making them widely applicable to bonding applications requiring heat resistance, such as power semiconductors. [Brief explanation of the drawing]

[0011] [Figure 1] Cross-sectional photograph of the joint surface of a copper test piece joined using the bonding material composition of Example 1. [Figure 2] Cross-sectional photograph of the joint surface of a copper test specimen joined using the bonding material composition of Comparative Example 1. [Modes for carrying out the invention]

[0012] The bonding material composition of the present invention is characterized in that its basic composition consists of solder particles and / or metal particles with a low melting point, metal particles with a high melting point, and flux. In the present invention, the low-melting-point metal particles that constitute the bonding material composition refer to metals and alloys with a melting point of 400°C or less, such as lead-free solder alloys (hereinafter referred to as "low-melting-point metal particles"), while the high-melting-point metal particles refer to metals and alloys with a melting point exceeding 400°C (hereinafter referred to as "high-melting-point metal particles").

[0013] The low-melting-point metal particles that can be used in the bonding material composition of the present invention are not limited in composition or particle size within the range in which the effects of the present invention are achieved. Examples of solder alloy particle compositions include lead-free solder compositions such as Sn-Ag-Cu, Sn-Cu, and Sn-Cu-Ni, while examples of metal particles with low melting points include Sn. Furthermore, the particle size of each particle is preferably the particle size specified in JIS standard Z3284-2 Annex A. Furthermore, regarding the amount added, it is preferable to use 10 to 90% by mass, when the total composition of the bonding material is considered as 100.

[0014] Furthermore, the high-melting-point metal particles that can be used in the bonding material composition of the present invention are not limited in composition, particle size, or shape, as long as they form an intermetallic compound inside the solder joint within the range in which the effects of the present invention are achieved. The composition of these metal particles can be exemplified by Cu, Ni, Cu-Ni alloys, Cu-Co alloys, etc., with particle sizes ranging from 0.1 μm to 100 μm, and shapes such as spherical or amorphous. Furthermore, regarding the amount added, it is preferable to use 0.1 to 70% by mass, when the total composition of the bonding material composition is considered as 100. Furthermore, multiple types of metal particles with different particle sizes, shapes, and compositions may be used in the bonding material composition.

[0015] On the other hand, the components and methods for processing metal particles are not limited within the scope of the effects of the present invention; any metal deactivator having a metal deactivation effect is acceptable. Examples of the metal deactivator include commercially available metal deactivators, such as triazole-based, imidazole-based, and thiadiazole-based ones. A metal deactivator having a melting point higher than that of the solder powder contained is preferred. Regarding the blending amount, there is no limitation as long as it is within the range where the effects of the present invention are achieved. However, if the content is increased, the metal deactivator or components derived from the metal deactivator may remain inside or around the solder joint after soldering, which may cause problems. Therefore, a smaller amount is preferred. Specifically, when the solvent component contained in the flux composition is set to 100, it is preferably 0.1% by mass or less. Also, there is no particular limitation on the treatment method. It is only necessary that the surface of the metal particles is coated with a metal deactivator and the oxidation of the metal particles can be prevented and suppressed until the soldering process.

[0016] The organic acid that can be used in the flux of the paste-like joining material composition of the present invention is not particularly limited as long as it is within the range where the effects of the present invention are achieved. Dicarboxylic acids and carboxylic acids are preferred. Examples of dicarboxylic acids include malonic acid, maleic acid, succinic acid, glutaric acid, adipic acid, etc., and examples of carboxylic acids include benzoic acid, lactic acid, oxalic acid, formic acid, acetic acid, etc. The solvent that can be used in the flux composition for the solder paste composition of the present invention is not particularly limited as long as it is within the range where the effects of the present invention are achieved. Preferably, it can dissolve the metal deactivator, and examples include alcohols and glycols. Furthermore, the flux of the paste-like joining material composition of the present invention may appropriately contain resin components such as antioxidants, binders, and rosin. Also, the blending amount of each component that can be used in the flux of the paste-like joining material composition of the present invention is not particularly limited as long as it is within the range where the effects of the present invention are achieved. A range where the workability such as printing characteristics is good as a joining material is preferred.

[0017] When forming a joint using the paste-like bonding material composition of the present invention, there are no limitations within the range in which the effects of the present invention are achieved. Examples of bonding methods include those using a pressurized firing apparatus as described in the examples, methods without pressurization, such as the conventional reflow method, heating in an oven, or bonding under a formic acid atmosphere or a reduced pressure atmosphere. [Examples]

[0018] The present invention will be described in detail below based on examples. [Processing of metal particles] 1) As a triazole-based metal deactivator, 0.1 g of ADEKA Stab CDA-1 (CDA-1) manufactured by ADEKA Corporation is mixed with 15 g of N-methyl-2-pyrrolidone (NMP) after weighing, and the mixture is uniformly dissolved to obtain the treatment solution. 2) 10 g of Cu-5.5Ni alloy particles with a Ni content of 5.5 atm% (5.1 mass%) (average particle size (approx. 6 μm)) was weighed into a glass sample bottle, then 5 g of CDA-1 and NMP treatment solution were added, the bottle was sealed tightly, and left to stand at room temperature. 3) After leaving step 2) for 65 hours, remove CDA-1 and the NMP treatment solution by filtration, dry the Cu-5.5Ni metal particles, and complete the process. (These were the metal particles used in Example 1.) 4) Next, regarding the metal particles used in Comparative Example 1, 10 g of Cu-5.5Ni alloy particles (average particle size (approximately 10 μm)) were weighed into a glass sample bottle, 5 g of NMP was added, the bottle was sealed tightly, and left to stand at room temperature. 5) After leaving step 4) for 65 hours, the NMP solution is removed by filtration, the Cu-5.5Ni metal particles are dried, and the coating process is completed. (These were the metal particles used in Comparative Example 1.) [Preparation of solder paste composition] The components shown in Table 1 were prepared, and samples of the present invention and comparative bonding paste compositions for measurement were prepared using the standard method for conventional solder paste. • Solder particles: SN100C Type 6 powder manufactured by Nippon Superior Co., Ltd. • Adipic acid (activator), decanol (solvent), isobornylcyclohexanol I used a commercially available binder.

[0019] [Table 1]

[0020] [Preparation of evaluation samples] Example 1, which is the paste-type bonding material composition of the present invention, and Comparative Example 1, which is a comparative example, are prepared. Each solder paste composition is applied to a 10 mmΦ copper test piece to a diameter of approximately 5 mm and a film thickness of 100 μm. The sample is then left on a hot plate at 130°C for 60 seconds to pre-dry. After that, a 5 mmΦ copper test piece is placed on the pre-dried solder paste composition so that the applied area and the copper test piece overlap. Subsequently, the samples for measurement were prepared by joining them using the HTM-3000 sintering device manufactured by Meisho Kiko Co., Ltd. under the following sintering conditions. (Sintering conditions) • Load: 5 MPa, Sintering temperature: 250°C, Firing time: 5 minutes, N2 atmosphere

[0021] 〔evaluation〕 The prepared samples were subjected to shear strength testing in accordance with "JIS Z 3198-5 Tensile and Shear Test Methods for Solder Joints". Specifically, the shear strength was measured using a Tensilon universal material testing machine manufactured by A&D Company, Limited, under the following conditions. • Shearing speed: 6mm / min, at room temperature (20℃~25℃) Furthermore, the bonding state was evaluated by observing the bonded cross-section using a JEOL Ltd. JSM-5700 scanning electron microscope. The shear strength results are shown in Table 2, and the cross-sectional observation results are shown in Figures 1 and 2.

[0022] [Table 2]

[0023] As shown in Table 2, the samples joined using the paste-like bonding material composition of the present invention have a shear strength that is 1.5 times higher than that of Comparative Example 1. This suggests that the soldered joints are denser and more uniform than those in the comparative example, and therefore high reliability can be expected. Furthermore, Figures 1 and 2 show that the samples joined using the paste-like bonding material composition of the present invention had extremely few voids in the bonded layer. This indicates that the metal particles contained in the paste-like bonding material composition of the present invention remained unoxidized until the soldering process, preventing non-wetting due to oxidation of the metal particles, and that virtually no metal deactivator, which is a treatment agent, remained. In contrast, Comparative Example 1 shows many voids in the bonding layer, indicating that the bonding state was incomplete due to issues such as non-wetting. As described above, the bonded body formed using the paste-like bonding material composition of the present invention has few voids, and the intermetallic compound is widely formed throughout the bonding layer, resulting in a good bonded body. Furthermore, since the intermetallic compounds widely distributed in the joint have a main composition of Cu6Sn5 or (Cu,Ni)6Sn5, they have a high melting point of over 400°C, resulting in excellent heat resistance and high reliability. [Industrial applicability]

[0024] The paste-like bonding material of the present invention and the bonded body formed using the paste-like bonding material composition can provide a heat-resistant bonding layer at low cost, and are therefore expected to have a wide range of applications in semiconductor bonding, in addition to bonding power modules and conventional electronic component bonding. [Explanation of symbols]

[0025] 1. 5mm diameter copper test piece 2 Bonding layer 3. Void 4. 10mmΦ copper test piece

Claims

[Claim 1] A bonding material composition having a paste-like consistency, It contains low-melting-point metal particles with a melting point of 400°C or less, high-melting-point metal particles with a melting point exceeding 400°C, and flux, The low-melting-point metal particles with a melting point of 400°C or less consist of lead-free solder alloys of the Sn-Ag-Cu, Sn-Cu, or Sn-Cu-Ni type. High-melting-point metal particles with a melting point exceeding 400°C consist of Cu, Ni, Cu-Ni alloy, or Cu-Co alloy, and these high-melting-point metal particles are coated with a triazole-based or imidazole-based metal deactivator. The flux composition contains organic acids, solvents, and binders. The organic acid in question is a dicarboxylic acid and a carboxylic acid. A paste-like bonding material composition characterized in that the binder is isobornylcyclohexanol.

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