Application of an additive in improving high temperature storage performance of solder paste

Abstract

The present invention relates to an application of an additive in improving the high temperature storage performance of solder paste, wherein the additive is composed of a mixture of two or three of 2,4-diphenyl-4-methyl-1-pentene, 3-isooctyl mercaptopropionate, and isobornyl methacrylate, and the additive is applied to solder paste. The additive of the present invention can effectively improve the high temperature storage performance of lead-free SnAgCu solder paste.

Description

Technical Field

[0001] The invention relates to an additive for lead-free SnAgCu solder paste, and in particular to a stabilizer capable of significantly improving the high-temperature storage time of the lead-free SnAgCu solder paste. Background Art

[0002] SMT (surface mount technology) refers to printing solder paste onto the circuit board pads through a steel mesh, or applying solder paste to the circuit board pads, and then mounting components such as capacitors, resistors, inductors, ICs, etc. onto the solder paste on the pads, and then performing heating and reflow soldering according to a specific reflow curve. During the soldering process, the solder paste melts, and the solder wets the pads and components, thereby achieving connection between the pads and components.

[0003] SMT plays an important role in the assembly of electronic components, especially in the preparation of miniaturized electronic products. In SMT technology, solder paste plays a key role in the process, and the quality of solder paste directly affects the soldering quality of the substrate. Excellent quality solder paste products should have good solderability, excellent storage, stability in use, and stable and reliable residues.

[0004] Solder paste is a mixture of tin powder and solder paste (also called flux), in which solder paste is mainly composed of rosin, activator, solvent, thixotropic agent and other materials. As the most critical component of solder paste, solder paste plays a role in removing metal oxides and the surface oxide film of the metal pad of the circuit board during the welding process, and protecting the solder from secondary oxidation during the welding process. Therefore, the activator in the solder paste is very critical. At present, the commonly used activators are mainly organic acids, halogen salts, organic amines and other types. The higher the activity of the flux, the easier it is to weld. But at the same time, the addition of highly active activators will also accelerate the corrosion of the surface of tin powder, which will lead to the loss of the function of some active substances during the storage of solder paste, and the viscosity of solder paste will increase during the storage process, and even cause the solder paste to dry out, which seriously affects the normal storage and use of solder paste. Solder paste has high requirements for the storage environment and needs to be stored at low temperature. Due to the poor environment of some manufacturers using solder paste, the indoor temperature is high in summer or the weather is hot during the transportation of solder paste, these situations will cause the solder paste to be exposed to high temperature for a long time. Therefore, reducing the reaction rate between the activator in the flux and the tin powder is very important to improve the high temperature storage stability of the solder paste.

[0005] In order to prepare solder paste that can be stored at high temperatures, the patent application with publication number CN107214431A uses bisphenol A epoxy resin, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, ε-hydroxycaprolactone, α-hydroxycarboxylate, etc. to soak the tin powder, then heat and dry or irradiate with ultraviolet light to form a surface coating film, and then stir with flux to obtain solder paste that can be stored at room temperature. The patent application number 200810239967.X removes the oxide film on the surface of the tin powder and then performs surface coating treatment, wherein the coating agent is sodium dodecyl sulfate, alkylphenol polyoxyethylene ether, polyethylene glycol, etc. The invention content mentions that the hydrophilic group in the coating agent can be adsorbed on the metal surface of the solder powder to form a coating film. Although there are many patent achievements for high temperature storage, most of them require the tin powder to be coated with a special coating agent first, and then stirred with the tin powder to form a solder paste. The operation steps are relatively complicated and the operation is difficult. Summary of the invention

[0006] The purpose of the present invention is to provide an additive that is easy to operate and can increase the high-temperature storage time of lead-free solder paste. The additive provided by the present invention can be dissolved in the flux paste at room temperature, effectively reducing the chemical reaction between the active substances in the flux paste and the tin powder, thereby improving the stability of the solder paste and achieving high-temperature storage of the solder paste.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] An additive is used in improving the high-temperature storage performance of solder paste. The additive is composed of a mixture of two or three of 2,4-diphenyl-4-methyl-1-pentene, isooctyl 3-mercaptopropionate, and isobornyl methacrylate. The additive is used in solder paste.

[0009] The additive of the invention is applied to lead-free SnAgCu series solder paste.

[0010] The application of an additive described in the present invention in improving the high temperature storage performance of solder paste is as follows:

[0011] 1) adding the additive into the soldering solder paste at 0.5% to 3% of the mass of the soldering solder paste, stirring evenly, and maintaining a vacuum degree of -0.1 to -0.12 MPa during stirring to obtain a mixed soldering solder paste;

[0012] 2) Add tin powder to the mixed flux paste and continue stirring to obtain a tin paste that is resistant to high temperature storage.

[0013] Preferably, in the above step 1), the temperature of adding the additive into the soldering solder paste is 20°C to 30°C.

[0014] Preferably, in the above step 2), tin powder is added to the stirred mixed solder paste at a mass ratio of tin powder: mixed solder paste of 86%:14% to 90%:10%.

[0015] The present invention is developed to solve the problem that the existing lead-free tin-silver-copper series solder paste is prone to sanding and drying under high ambient temperature conditions. Since the wettability of the lead-free tin-silver-copper series alloy itself is not as good as that of the lead-containing solder paste, it is common for the lead-free tin-silver-copper solder paste to dry out when stored in a high-temperature environment. Therefore, the proportion of active agent in the solder paste used for the lead-free tin-silver-copper series is usually higher than that of the lead-containing solder paste. The present invention adds additives to the solder paste and stirs to achieve uniform mixing of the additives and the solder paste, and then adds tin powder and stirs to obtain a solder paste product with good high-temperature storage performance.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) Compared with lead-free solder paste without the additive of the present invention, the additive of the present invention can make the solder paste have better high temperature storage resistance.

[0018] (2) The additive of the present invention is easy to use and can be directly added to the soldering paste at room temperature and then fully stirred to make the additive and the soldering paste completely mixed and uniform. DETAILED DESCRIPTION

[0019] The content of the present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0020] Example 1

[0021] An additive is used in improving the high-temperature storage resistance of solder paste. The additive consists of the following materials: 1 g of 2,4-diphenyl-4-methyl-1-pentene and 0.5 g of isooctyl 3-mercaptopropionate.

[0022] The method of applying additives to solder paste is as follows:

[0023] At 20℃~25℃, add 1g of 2,4-diphenyl-4-methyl-1-pentene, 0.5g of 3-mercaptopropionic acid isooctyl ester, and 50g of solder paste into a double planetary mixer and stir at a speed of 30rpm for 10min. During the stirring, the vacuum degree is maintained at -0.1MPa. Then, add 450g of SnAg3.0Cu0.5 tin powder into the stirred solder paste, continue to stir for 10min using the double planetary mixer, clean the pot wall, continue to stir for 20min, and fill the solder paste into a can or a syringe to obtain a finished solder paste product.

[0024] The solder paste with the additive of this embodiment and the solder paste without the additive were placed in a constant temperature oven at 40°C for high temperature storage. After 30 days of storage, the solder paste was taken out and returned to room temperature. It was observed that the solder paste with the additive of the present invention was in good condition and there was no drying phenomenon on the surface. The viscosity was then measured, and the results showed that the viscosity of the solder paste increased by 9 Pa.s. The wettability, collapse, and tin beads of the solder paste were then tested. The results showed that there was no significant difference between the solder paste before high temperature storage and the solder paste without the additive. The solder paste without the additive prepared from the same solder paste was observed again, and it was found that the surface state of the solder paste was poor, there was obvious drying phenomenon, and the test viscosity increased significantly.

[0025] Example 2

[0026] An additive is used in improving the high-temperature storage resistance of solder paste. The additive consists of the following materials: 0.3 g of 2,4-diphenyl-4-methyl-1-pentene and 0.2 g of isooctyl 3-mercaptopropionate.

[0027] The method of applying additives to solder paste is as follows:

[0028] At 25℃~30℃, add 0.3g of 2,4-diphenyl-4-methyl-1-pentene, 0.2g of 3-mercaptopropionic acid isooctyl ester, and 100g of solder paste into a double planetary mixer for stirring at a speed of 30rpm for 10min, and keep the vacuum degree -0.1MPa during stirring. Add 880g of SnAg3.0Cu0.5 tin powder into the stirred solder paste, continue to stir for 10min using the double planetary mixer, clean the pot wall, continue to stir for 25min, and fill the solder paste into cans or syringes to obtain the finished solder paste product.

[0029] The solder paste with the additive of this embodiment and the solder paste without the additive were placed in a constant temperature oven at 40°C for high temperature storage. After 30 days of storage, the solder paste was taken out and returned to room temperature. It was observed that the solder paste with the additive of the present invention was in good condition and there was no drying phenomenon on the surface. The viscosity was then measured, and the results showed that the viscosity of the solder paste increased by 7 Pa.s. The wettability, collapse, and tin beads of the solder paste were then tested. The results showed that there was no significant difference between the solder paste before high temperature storage and the solder paste without the additive. The solder paste without the additive prepared from the same solder paste was observed again, and it was found that the surface state of the solder paste was poor, there was obvious drying phenomenon, and the test viscosity increased significantly.

[0030] Example 3

[0031] An additive is used in improving the high-temperature storage resistance of solder paste. The additive consists of the following materials: 0.5 g of 2,4-diphenyl-4-methyl-1-pentene and 1 g of isobornyl methacrylate.

[0032] The method of applying additives to solder paste is as follows:

[0033] At about 25°C, add 0.5g of 2,4-diphenyl-4-methyl-1-pentene, 1g of isobornyl methacrylate, and 100g of solder paste into a double planetary mixer for stirring at a speed of 30rpm for 10 minutes, and keep the vacuum degree -0.12MPa during stirring. Add 800g of SnAg0.3Cu0.7 tin powder into the stirred solder paste, continue to stir for 10 minutes using the double planetary mixer, clean the pot wall, continue to stir for 20 minutes, and fill the solder paste into cans or syringes to obtain the finished solder paste product.

[0034] The solder paste with the additive of this embodiment and the solder paste without the additive were placed in a constant temperature oven at 40°C for high temperature storage. After 30 days of storage, the solder paste was taken out and returned to room temperature. It was observed that the solder paste with the additive of the present invention was in good condition and there was no drying phenomenon on the surface. The viscosity was then measured, and the results showed that the viscosity of the solder paste increased by 9pa.s. The wettability, collapse, and tin beads of the solder paste were then tested. The results showed that there was no significant difference between the solder paste before high temperature storage and the solder paste without the additive. The solder paste without the additive prepared from the same solder paste was observed again, and it was found that the surface state of the solder paste was poor, there was obvious drying phenomenon, and the test viscosity increased significantly.

[0035] Example 4

[0036] An additive is used in improving the high-temperature storage resistance of solder paste. The additive consists of the following materials: 0.5 g of isooctyl 3-mercaptopropionate and 1 g of isobornyl methacrylate.

[0037] The method of applying additives to solder paste is as follows:

[0038] Add 0.5g of 2-isooctyl 3-mercaptopropionate, 1g of isobornyl methacrylate, and 100g of solder paste into a double planetary mixer and stir at 30rpm for 10min. Keep the vacuum degree at -0.12MPa during stirring. Add 700g of SnAg0.3Cu0.7 tin powder into the stirred solder paste, continue to stir for 10min using the double planetary mixer, clean the pot wall, continue to stir for 22min, and fill the solder paste into cans or syringes to obtain the finished solder paste product.

[0039] The solder paste with the additive of this embodiment and the solder paste without the additive were placed in a constant temperature oven at 40°C for high temperature storage. After 30 days of storage, the solder paste was taken out and returned to room temperature. It was observed that the solder paste with the additive of the present invention was in good condition and there was no drying phenomenon on the surface. The viscosity was then measured, and the results showed that the viscosity of the solder paste increased by 8pa.s. The wettability, collapse, and tin beads of the solder paste were then tested. The results showed that there was no significant difference between the solder paste before high temperature storage and the solder paste without the additive. The solder paste without the additive prepared from the same solder paste was observed again, and it was found that the surface state of the solder paste was poor, there was obvious drying phenomenon, and the test viscosity increased significantly.

[0040] Example 5

[0041] An application of an additive in improving the high-temperature storage resistance of solder paste, the additive consisting of the following materials: 2 g of 2,4-diphenyl-4-methyl-1-pentene, 5 g of isooctyl 3-mercaptopropionate, and 3 g of isobornyl methacrylate.

[0042] The method of applying additives to solder paste is as follows:

[0043] At 25°C, add 2g of 2,4-diphenyl-4-methyl-1-pentene, 5g of isooctyl 3-mercaptopropionate, 3g of isobornyl methacrylate, and 1000g of solder paste into a double planetary mixer for stirring at a speed of 30rpm for 15min, and keep the vacuum degree -0.11MPa during stirring. Add 6142.8g of SnAg0.3Cu0.7 tin powder into the stirred solder paste, continue to stir for 10min using the double planetary mixer, clean the pot wall, continue to stir for 25min, and fill the solder paste into cans or syringes to obtain the finished solder paste product.

[0044] The solder paste with the additive of this embodiment and the solder paste without the additive were placed in a constant temperature oven at 40°C for high temperature storage. After 30 days of storage, the solder paste was taken out and returned to room temperature. It was observed that the solder paste with the additive of the present invention was in good condition and there was no drying phenomenon on the surface. The viscosity was then measured, and the results showed that the viscosity of the solder paste increased by 6 Pa.s. The wettability, collapse, and tin beads of the solder paste were then tested. The results showed that there was no significant difference between the solder paste before high temperature storage and the solder paste without the additive. The solder paste without the additive prepared from the same solder paste was observed again, and it was found that the surface state of the solder paste was poor, there was obvious drying phenomenon, and the test viscosity increased significantly.

[0045] In order to further verify the stability of the solder paste, a centrifugal test experiment was conducted to verify the effect of adding the additive of the present invention to the solder paste. The results are shown in Table 1.

[0046] Table 1 Test results of solder paste status after centrifugation for 40 minutes

[0047]

[0048] The soldering paste used in the present invention can be commercially available finished soldering paste, or can be prepared by itself according to the existing technology.

[0049] The additive of the invention has wide applications and can be widely used in various types of lead-free tin-silver-copper series solder pastes.

Claims

1. Application of an additive in improving the high temperature storage performance of solder paste, It is characterized in that The additive is composed of a mixture of two or three of 2,4-diphenyl-4-methyl-1-pentene, isooctyl 3-mercaptopropionate, and isobornyl methacrylate, and the additive is applied to solder paste; the specific application method is as follows: 1) adding the additive into the soldering solder paste at 0.5% to 3% of the mass of the soldering solder paste, stirring evenly, maintaining a vacuum degree of -0.1 to -0.12 MPa during stirring, to obtain a mixed soldering solder paste; 2) Add tin powder to the mixed flux paste and continue stirring to obtain a tin paste that is resistant to high temperature storage.

2. Use of an additive according to claim 1 in improving the high temperature storage performance of solder paste, It is characterized in that The additive is applied to lead-free SnAgCu series solder paste.

3. Use of an additive according to claim 1 in improving the high temperature storage performance of solder paste, It is characterized in that In the above step 1), the temperature for adding the additive into the soldering solder paste is 20°C to 30°C.

4. Use of an additive according to claim 1 or 3 in improving the high temperature storage performance of solder paste, It is characterized in that In the above step 2), tin powder is added to the stirred mixed flux paste at a mass ratio of tin powder: mixed flux paste of 86%:14% to 90%:10%.

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