Halogen-free low cavity SnBi series soldering paste and preparation method thereof

Abstract

The application discloses a zero-halogen low-cavity SnBi-based soldering paste and a preparation method thereof. Components and mass percentages of the soldering paste are as follows: 35-40% of rosin, 4% of stabilizer ke-311, 6-8% of thixotropic agent, 1-2.5% of acid anhydride, 3-5.5% of a mixture of imidazole and imidazole derivatives, 10-15% of organic acid, and 30-40% of alcohol ether. The soldering paste prepared by using the application and solder powder are formulated into a tin paste, and the tin paste has the advantages of low welding cavity rate, good QFN tin climbing, no black edge on a welding point surface and periphery, good storage stability at normal temperature and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soldering paste and its preparation method, and particularly relates to zero-halogen low-cavity SnBi series soldering paste and its preparation method. BACKGROUND

[0002] In the technical field of soldering paste, SnBi series low-temperature soldering paste is currently still in the initial stage of development. In 2019, the International Electronics Assembly Production Alliance officially proposed to apply low-temperature soldering paste to actual SMT production. However, the current process conditions and formula research are not mature, and the application is not as extensive and mature as the traditional lead-free SAC series soldering paste. However, based on the advantages of low energy consumption, low cost and low carbon emission, SnBi series low-temperature soldering paste will be the development trend of future SMT welding. At present, low-temperature soldering paste in the industry is mainly applied to products such as heat dissipation modules, frequency converters, low-voltage electrical appliances and LED displays. The research on cavity rate is an important performance index for overcoming the application of low-temperature soldering paste, so it is very important and necessary to study it. The existing low-temperature soldering paste is not mature in terms of performance indicators, which is manifested in poor tin deposition, large cavity rate, black edge after welding and poor storage stability. In order to solve the problem of tin deposition, most manufacturers will add halogen, and the reliability after welding cannot be guaranteed. SUMMARY

[0003] The purpose of the present application is to solve the problems existing in the prior art, and to provide a zero-halogen low-cavity SnBi series soldering paste which has low cavity rate, good tin climbing, no black edge after welding and good stability after being prepared into soldering paste with solder powder. The present application also provides a preparation method of the soldering paste.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] A zero-halogen low-cavity SnBi series soldering paste, the components and mass percentage of the soldering paste are as follows: 35-40% of rosin, 4% of stabilizer ke-311, 6-8% of thixotropic agent, 1-2.5% of acid anhydride, 3-5.5% of a mixture of imidazole and imidazole derivatives, 10-15% of organic acid, and 30-40% of alcohol ether.

[0006] Further, the rosin is a polymerized rosin with a certain acid value and a low softening point, specifically one or two of AXE, fully hydrogenated polymerized rosin, HR-CH, 685 and SBR. The acid value of the rosin is 150-250 mgKOH / g, and the acid value of the rosin has a certain promoting effect on reducing the surface tension of alloy spreading; the softening point of the rosin is 50-100℃, and the low softening point can enhance the flow of the soldering paste after heating, increase the spreading, reduce the alloy flow work, improve the wetting, and thus reduce the cavity.

[0007] Further, the thixotropic agent is an amide thixotropic agent, one or two of ZHH, 6500 agent, THIXATROL PLUS, thixotropic agent R. The thixotropic agent is relatively sensitive to temperature, and is more beneficial to the spreading of the solder paste on the pad surface after heating in the reflow soldering process, thereby reducing the flow resistance of the molten tin liquid, and further improving the wetting and reducing the voids.

[0008] Further, the acid anhydride is one or two of glutaric anhydride and NA acid anhydride. By adding the acid anhydride, the reaction mechanism is that it reacts with water to generate a polybasic organic acid, and the generated polybasic organic acid continues to participate in the reaction to remove the oxides on the solder and the soldered metal surface, thereby reducing the influence of moisture on the voids, and further reducing the voids.

[0009] Further, the mixture of imidazole and imidazole derivatives is a mixture of benzimidazole, imidazole, and carbonyl diimidazole in a mass ratio of 1.1:1.35:2.2. A large amount of experimental data shows that the ratio is the lowest ratio for no visible black edge after soldering. If the ratio is too high, the viscosity of the solder paste is large, and it is not easy to print.

[0010] Further, the organic acid is a mixture of two or more of DMBA, amine-O, phenol, tetracosanoic acid, adipic acid, OP10, and hydrogenated dimer acid. The main reason for the drying and sanding of the solder paste is the oxidation-reduction reaction between the organic carboxylic acid and the solder powder. The reaction activity of the short-chain acid (less than six carbons) is relatively high. The present application uses long-chain acid to configure, which can greatly ensure the stability of the solder paste system. In addition, through experiments, the addition of surfactants OP10 and phenol can effectively improve the tin climbing performance.

[0011] Further, the alcohol ether substance is a mixture of hexanediol and EHDG in a mass ratio of 1-2:2-3. Hexanediol and EHDG are special solvents for solder paste, and have good solubility and moderate boiling point. According to the ratio, the volatilization degree is good (more than 80%) when the reflow soldering temperature is about 200℃ and the heating time is about 60s, which can effectively reduce the voids.

[0012] The preparation method of the zero-halogen low-void SnBi-based soldering flux provided by the application is as follows: pine resin, stabilizer, thixotropic agent, and alcohol ether substance are added to a container, heated to 165-180℃, and stirred until completely dissolved, then the heating is stopped, and acid anhydride, imidazole and its derivative substances are added, dissolved, and then organic acid is added, stirred until completely dissolved, poured into a container, and frozen to obtain the soldering flux.

[0013] Compared with the prior art, the soldering flux provided by the application has at least the following advantages:

[0014] (1) the soldering paste of the present application carries reasonable collocation of colophony, stabilizer, thixotropic agent, active agent, acid anhydride, mixture of imidazole and imidazole derivative, organic acid, alcohol ether, especially the imidazole and derivative with accurate proportion, which can ensure the surface and periphery of soldering point without black edge after soldering, the stabilizer ke-311 added can be stored for more than 6 months at normal temperature (about 25 DEG C) with good stability, the soldering paste does not contain halogen, and the reliability after soldering is good;

[0015] (2) the soldering paste of the present application has simple and easy preparation method, and can realize industrialized production.

[0016] (3) the soldering paste prepared by the present application has the advantages of small soldering cavity rate (soldering cavity rate of empty pad is less than 8%), good QFN tin climbing (more than 70%), no black edge after soldering, good stability and the like when being used to prepare tin paste with solder powder. DETAILED DESCRIPTION

[0017] The content of the present application is further illustrated below in combination with examples. Example 1

[0018] A zero-halogen low-cavity SnBi-based soldering paste, the components and mass percentage of the soldering paste are as follows:

[0019] HR-CH 38%

[0020] ke-311 4%

[0021] 6500 agent 5%

[0022] ZHH 3%

[0023] DMBA 3%

[0024] Adipic acid 2%

[0025] Phenol 1%

[0026] Hydrogenated dimer acid 4.5%

[0027] Benzimidazole 1.1%

[0028] Imidazole 1.35%

[0029] Carbonyl diimidazole 2.2%

[0030] NA acid anhydride 1.5%

[0031] EHDG 20.5%

[0032] Hexanediol 12.85%

[0033] The method for preparing the zero-halogen low-cavity SnBi series soldering paste is as follows: HR-CH, ke-311, 6500 agent, ZHH, hexanediol, EHDG are added into a container, heated to 180°C, and after stirring until completely dissolved, heating is stopped, benzoimidazole, imidazole, carbonyl diimidazole, and NA acid anhydride are added, and the temperature is kept at about 150°C, after dissolution, organic acid DMBA, adipic acid, phenol, and hydrogenated dimer acid are added, and after stirring until completely dissolved, the mixture is poured into a container, sealed, and cooled and solidified in a refrigerator to obtain the soldering paste of the application. The soldering paste is mixed with SnBi35Ag1.0 soldering powder at a mass ratio of 11.2:88.8 to prepare the soldering paste. Example 2

[0034] A zero-halogen low-cavity SnBi series soldering paste, the components and mass percentages of the soldering paste are as follows:

[0035] Fully hydrogenated polymerized rosin 25%

[0036] AXE 13%

[0037] ke-311 4%

[0038] Thixotropic agent R 4%

[0039] THIXATROL PLUS 4%

[0040] Phenol 1.5%

[0041] Tetracosanoic acid 4%

[0042] OP10 2.5%

[0043] Hydrogenated dimer acid 4.5%

[0044] Benzoimidazole 1.1%

[0045] Imidazole 1.35%

[0046] Carbonyl diimidazole 2.2%

[0047] Glutaric anhydride 1.5%

[0048] Hexanediol 13%

[0049] EHDG 18.35%

[0050] The method for preparing the zero-halogen low-cavity SnBi-based soldering paste is as follows: full-hydrogenated polymerized rosin, AXE, ke-311, thixotropic agent R, THIXATROL PLUS, hexanediol, EHDG are added into a container, heated to 165°C, and after stirring until completely dissolved, heating is stopped, imidazole, benzimidazole, carbonyl diimidazole, glutaric anhydride are added, the temperature is kept at about 160°C, after dissolution, organic acid phenol, tetracosanoic acid, OP10, hydrogenated dimer acid are added, after stirring until completely dissolved, poured into a container, sealed, placed in a refrigerator to cool and solidify, and the soldering paste of the application is obtained. The soldering paste is prepared into a solder paste by mixing with SnBi35Ag1.0 soldering powder at a mass ratio of 11.2:88.8. Example 3

[0051] A zero-halogen low-cavity SnBi-based soldering paste, the components and mass percentages of the soldering paste are as follows:

[0052] Full-hydrogenated polymerized rosin 25%

[0053] HR-CH 13%

[0054] ke-311 4%

[0055] Thixotropic agent R 3%

[0056] 6500 agent 5%

[0057] Phenol 1.5%

[0058] DMBA 4%

[0059] OP10 2.5%

[0060] Hydrogenated dimer acid 4.5%

[0061] Benzimidazole 1.1%

[0062] Imidazole 1.35%

[0063] Carbonyl diimidazole 2.2%

[0064] Glutaric anhydride 1.5%

[0065] Hexanediol 13%

[0066] EHDG 18.35%

[0067] The method for preparing the zero-halogen low-cavity SnBi-based soldering paste is as follows: full-hydrogenated polymerized rosin, HR-CH, ke-311, thixotropic agent R, 6500 agent, hexanediol, EHDG are added into a container, heated to 175°C, and after stirring to complete dissolution, heating is stopped, benzimidazole, imidazole, carbonyl diimidazole, glutaric anhydride are added, the temperature is kept at about 155°C, after dissolution, organic acid phenol, DMBA, OP10 are added, and after stirring to complete dissolution, the mixture is poured into a container and sealed, and after cooling and solidification in a refrigerator, the zero-halogen low-cavity SnBi-based soldering paste is obtained; the soldering paste is mixed with SnBi35Ag1.0 soldering powder at a mass ratio of 11.2:88.8 to prepare a soldering paste. Example 4

[0068] A zero-halogen low-cavity SnBi-based soldering paste, components and mass percentages of the soldering paste are as follows:

[0069] Full-hydrogenated polymerized rosin 25%

[0070] AXE 13%

[0071] ke-311 4%

[0072] Thixotropic agent R 5%

[0073] ZHH 3%

[0074] Phenol 1.5%

[0075] DMBA 4%

[0076] OP10 2.5%

[0077] Amine-O 4.5%

[0078] Benzimidazole 1.1%

[0079] Imidazole 1.35%

[0080] Carbonyl diimidazole 2.2%

[0081] Glutaric anhydride 1.5%

[0082] Hexanediol 13%

[0083] EHDG 18.35%

[0084] The method for preparing the zero-halogen low-cavity SnBi-based soldering paste is as follows: full-hydrogenated polymerized rosin, AXE, ZHH, ke-311

[0085] Thixotropic agent R, hexanediol, EHDG are added into the container, heated to 170℃, stop heating after stirring until completely dissolved, add carbonyl diimidazole, imidazole, benzimidazole, NA anhydride, keep the temperature at about 160℃, after dissolving add organic acid phenol, DMBA, OP10, amine-O, stir until completely dissolved, pour into the container, seal, put in the refrigerator to cool and solidify, then the soldering paste of the application is obtained, the soldering paste is mixed with SnBi35Ag1.0 soldering powder according to the mass ratio of 11.2:88.8 to prepare the soldering paste. Example 5

[0086] A zero-halogen low-cavity SnBi-based soldering paste, the components and mass percentage of the soldering paste are as follows:

[0087] Perhydrogenated polymerized rosin 13%

[0088] HR-CH 25%

[0089] ke-311 4%

[0090] Thixotropic agent R 2%

[0091] THIXATROL PLUS 6%

[0092] Phenol 1.5%

[0093] DMBA 4%

[0094] Tetracosanoic acid 2.5%

[0095] Adipic acid 4.5%

[0096] Benzimidazole 1.1%

[0097] Imidazole 1.35%

[0098] Carbonyl diimidazole 2.2%

[0099] Glutaric anhydride 1.5%

[0100] Hexanediol 13%

[0101] EHDG 18.35%

[0102] The method for preparing the zero-halogen low-cavity SnBi series soldering paste is as follows: add perhydrogenated polymeric rosin, HR-CH, ke-311, THIXATROL PLUS, thixotropic agent R, hexanediol, EHDG into a container, heat to 175°C, stop heating after stirring to complete dissolution, add benzimidazole, carbonyl diimidazole, imidazole, glutaric anhydride, keep the temperature at about 165°C, after dissolution, add organic acid phenol, DMBA, tetracosanoic acid, adipic acid, stir to complete dissolution, pour into a container, seal, put in a refrigerator to cool and solidify, and then the soldering paste of the application is obtained, and the soldering paste is prepared into a solder paste with SnBi35Ag1.0 solder powder in a mass ratio of 11.2:88.8. Example 6

[0103] A zero-halogen low-cavity SnBi series soldering paste, the components and mass percentages of the soldering paste are as follows:

[0104] HR-CH 25%

[0105] 685 13%

[0106] ke-311 4%

[0107] ZHH 6%

[0108] THIXATROL PLUS 2%

[0109] DMBA 3%

[0110] Adipic acid 2%

[0111] Phenol 1%

[0112] OP10 1%

[0113] amine-O 4.5%

[0114] Benzimidazole 1.1%

[0115] Imidazole 1.35%

[0116] Carbonyl diimidazole 2.2%

[0117] NA anhydride 1.5%

[0118] Hexanediol 14.5%

[0119] EHDG 17.85%

[0120] The method for preparing the zero-halogen low-cavity SnBi series soldering paste is as follows: HR-CH, 685, ke-311, THIXATROL PLUS, ZHH, hexanediol, EHDG are added into a container, heated to 180℃, and stirring is stopped after complete dissolution; imidazole, benzimidazole, carbonyl diimidazole, and NA acid anhydride are added, and the temperature is kept at about 170℃; after dissolution, organic acids DMBA, adipic acid, phenol, OP10, and amine-O are added, and stirring is stopped after complete dissolution; the mixture is poured into a container and sealed; after cooling and solidification in a refrigerator, the soldering paste of the application is obtained; and the soldering paste is mixed with SnBi35Ag1.0 soldering powder at a mass ratio of 11.4:88.6 to prepare a soldering paste.

[0121] Soldering black edge test method of soldering paste

[0122] The prepared soldering paste is prepared into a soldering paste according to a certain proportion, centrifuged for 2 minutes by using a soldering paste automatic centrifugal stirrer, printed on a red copper sheet by using a 0.12mm thick steel screen, kept on a constant temperature heating platform heated to 220℃ for 10s, and then observed under a high-definition microscope to observe the black edge of the soldering point surface and periphery.

[0123] QFN soldering paste climbing tin test method

[0124] The prepared soldering paste is used to solder the same model QFN chip on the same test PCB board under the same reflow soldering condition, the PCBBA sample board after soldering is placed under a microscope to measure the side climbing tin height at the same angle, and the climbing tin height percentage is recorded.

[0125] The soldering paste in the examples is tested under the same test condition according to the test method, and the performance test results are as follows:

[0126] Soldering paste performance test comparison table As can be seen from the above table, under the same test condition, the soldering paste of the application has a soldering cavity rate of less than 10%, and the QFN climbing tin is more than 70%, and the soldering paste in the examples is a zero-halogen soldering paste, and the soldering paste in example 3 has the best comprehensive performance.

[0127] The elimination of black edge of the soldering point after soldering is a difficulty of SnBi series alloy itself, and the soldering paste in the application does not appear black edge after soldering, and the soldering appearance is good.

[0128] The halogen content affects the storage stability of the soldering paste, and the soldering paste in the examples is in good condition after 90 days of long-term storage at room temperature, and the viscosity change value is less than 20Pa·s, and the storage stability is good, and the soldering paste in example 4 can be stored at room temperature for more than 6 months, and the viscosity change value is less than 10Pa·s.

[0129] The stabilizer ke-311 described in the present application, rosin such as AXE, fully hydrogenated polymerized rosin, HR-CH, 685, SBR, stearic acid amide thixotropic agent such as ZHH, 6500 agent, THIXATROL PLUS, thixotropic agent R, organic acid such as DMBA, amine-O, phenol, lignoceric acid, adipic acid, OP10, hydrogenated dimer acid, and glutaric anhydride, NA anhydride, benzimidazole, imidazole, carbonyl diimidazole, etc., are all commercially available.

[0130] The above examples are merely to describe the preferred embodiments of the present application, and are not intended to limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the technical scope of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A zero-halogen low cavity SnBi-based soldering paste, characterized by, The component and mass percentage of the soldering paste are as follows: 35-40% of rosin, 4% of stabilizer ke-311, 6-8% of thixotropic agent, 1-2.5% of acid anhydride, 3-5.5% of mixture of imidazole and imidazole derivative, 10-15% of organic acid, 30-40% of alcohol ether; The rosin is one or two of AXE, fully hydrogenated polymerized rosin, HR-CH, 685, SBR; The thixotropic agent is one or two of amide thixotropic agent, ZHH, 6500 agent, THIXATROL PLUS, thixotropic agent R; The acid anhydride is one or two of glutaric anhydride and NA acid anhydride; The mixture of imidazole and imidazole derivative is a mixture of benzimidazole, imidazole and carbonyl bismidazole with a mass ratio of 1.1:1.35:2.2; The organic acid is a mixture of two or more of DMBA, amine-O, phenol, tetracosanoic acid, adipic acid, OP10 and hydrogenated dimer acid; The alcohol ether is a mixture of hexanediol and EHDG with a mass ratio of 1-2:2-3.

2. The preparation method of a zero-halogen and low-cavity SnBi-based soldering paste according to claim 1, characterized in that, The preparation method is as follows: the rosin, stabilizer, thixotropic agent and alcohol ether are added into a container, heated to 165-180 DEG C, stirred until completely dissolved, then heated, and then the acid anhydride, the mixture of imidazole and imidazole derivative are added, dissolved, then the organic acid is added, stirred until completely dissolved, then poured into a container, and then frozen to obtain the soldering paste.

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