Flux paste for low-voidage solder paste and preparation method of flux paste

Abstract

The invention discloses flux paste for low-voidage solder paste and a preparation method of the flux paste. The flux paste comprises the following components in percentage by mass: 0.1-0.5% of a chelating agent, 0.01-0.2% of a flatting agent, 2.0-10.0% of a nonionic low-foaming surfactant, 3-10% of an active agent, 2-5% of a thickening agent and the balance of a mixture of rosin resin, a solvent and a thixotropic agent. The active agent is a mixture compounded by trimethyl butenediol and 2-dimethylolpropionic acid (DMPA) according to the mass ratio of (3-7): (2-5), and the nonionic low-foaming surfactant is a mixture compounded by TRITON CF-32 and alkyl alcohol polyoxyethylene (25) ether according to the mass ratio of 2: 1. Solder paste prepared from the flux paste prepared by the method is extremely low in BGA welding spot void rate, high in activity and good in stability, can effectively improve the reliability of welding spots of electronic products, and is particularly suitable for high-precision welding with the reliability requirement.

Description

Technical Field

[0001] The invention belongs to the technical field of tin welding materials, and particularly relates to a soldering paste for low void rate solder paste and a preparation method thereof. Background Art

[0002] Solder paste is an essential welding material for electronic assembly and is widely used in consumer electronics, automotive electronics, industrial electronics, communication equipment and other fields. Precision welding has very high requirements for solder joint reliability. The IPC standard requires that the void rate of lead-free solder paste BGA should be less than 25%, which can no longer meet the welding requirements.

[0003] Solder joint voids are an important factor affecting solder joint reliability, especially for precision components. Voids can cause the fatigue life of electronic products to deteriorate, the mechanical strength to drop sharply, and cause cracks or even breakage in solder joints. Voids reduce the effective thermal conductivity area of ​​solder joints, and heat concentration generates stress and strain that reduces the service life of electronic products. Therefore, research and development of low void rate solder paste is an urgent issue for solder paste manufacturers to solve. Summary of the invention

[0004] The purpose of the present invention is to provide a soldering paste with low void rate, strong activity, good stability and good printability during welding, and a preparation method thereof.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A soldering paste for solder paste with low voiding rate, the soldering paste comprises the following components and mass contents: 0.1-0.5% of a chelating agent, 0.01-0.2% of a leveling agent, 2.0%-10.0% of a nonionic low-foaming surfactant, 3%-10% of an activator, 2%-5% of a thickener, and the remainder is a mixture of rosin resin, a solvent and a thixotropic agent;

[0007] The chelating agent is prepared by compounding HYNIC and DOTA in a mass ratio of 2:1;

[0008] The leveling agent is a mixture of one or more of BYK300, BYK301, and BYK302;

[0009] The thickener is prepared by compounding TT-935 and polyisobutylene HV300 in a mass ratio of 1:1;

[0010] The mixture comprises 35-45% rosin resin, 30-40% solvent and 5-11% thixotropic agent; wherein the rosin resin is a mixture of HM8208 resin and hydrogenated rosin in a mass ratio of 1:3; the solvent is a mixture of DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol in a mass ratio of 1:1:1; and the thixotropic agent is a mixture of N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide in a mass ratio of 2:1.

[0011] A method for preparing a soldering paste for low voiding rate solder paste comprises the following steps:

[0012] (1) Calculate the mass of the materials according to the ratio of each material, weigh them, and place them in corresponding containers;

[0013] (2) Heat HM8208 resin and hydrogenated rosin to melt and mix evenly, and cool to form a film-forming agent;

[0014] (3) Mix and stir the solvent DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol evenly;

[0015] (4) mixing the thixotropic agent N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide evenly;

[0016] (5) First, add the solvent, film-forming agent and thickener into the reactor, heat and stir until they are completely melted. Keep the temperature at 160°C and stir for 5 minutes, then turn off the heat. Slowly add the thixotropic agent and stir until it melts. Then add the activator, non-ionic low-foaming surfactant, chelating agent and leveling agent in sequence. After the materials are completely melted, stir for 5 to 8 minutes. When the temperature drops to 130°C, transfer the molten flux to a container and seal it. Cool it to room temperature to obtain the flux paste.

[0017] The present invention has the following advantages:

[0018] 1. The commonly used activators in soldering solder paste are organic amines and organic acids, which are easy to decompose and produce a large amount of gas during the reflow process. In the reflow soldering process, some of the gas cannot be removed due to the surface tension of the molten metal, and is wrapped in the solder joint to form bubbles, and finally forms solder joint voids. The present invention uses trimethylbutylene glycol and 2-dihydroxymethylpropionic acid organic compounds in a mass ratio of (3-7): (2-5) as activators. The solder paste can effectively remove oxides and impurities from the pad and components during the reflow soldering process, is not easy to decompose and produce gas, and is not easy to form voids in the solder joint.

[0019] 2. The present invention uses low-foam TRITON CF-32 and alkyl alcohol polyoxyethylene (25) ether in a mass ratio of 2:1 to effectively reduce the surface tension of liquid solder, which is beneficial to the removal of gas inside the metal liquid, thereby reducing the void rate of the solder joint.

[0020] 3. The chelating agent of the present invention forms a stable chelate with metal ions, reduces the gas generated by the decomposition of the acidified product, and reduces the void ratio.

[0021] 4. The leveling agent of the present invention can not only improve the printability of solder paste, but also reduce the surface tension of liquid solder, improve wettability and reduce void rate.

[0022] 5. The soldering flux prepared by the present invention has low void rate, strong activity and good stability, and can effectively improve the reliability of solder joints of electronic products, and is particularly suitable for high-precision welding with reliability requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an X-ray scanning void rate diagram of the solder paste solder joints of the solder paste of Example 1 of the present invention;

[0024] Figure 2 This is an X-ray scanning void rate diagram of the solder paste solder joints of the solder paste of Example 2 of the present invention;

[0025] Figure 3 This is an X-ray scanning void rate diagram of the solder paste solder joints of the solder paste of Example 3 of the present invention;

[0026] Figure 4 This is an X-ray scanning void rate diagram of the solder paste solder joints of the solder paste of Example 4 of the present invention;

[0027] Figure 5 This is an X-ray scanning void rate diagram of the solder paste solder joints of the solder paste of Example 5 of the present invention;

[0028] Figure 6 This is the void rate diagram of the solder joint of ALPHA CVP390, a low void solder paste of the same type on the market. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the contents described in the examples.

[0030] The chelating agent used in the following Examples 1 to 5 is HYNIC and DOTA compounded in a mass ratio of 2:1; the thickener is TT-935 and HV300 compounded in a mass ratio of 1:1; the nonionic low-foaming surfactant is a mixture of TRITON CF-32 and alkyl alcohol polyoxyethylene (25) ether compounded in a mass ratio of 2:1; the rosin resin is a mixture of HM8208 resin and hydrogenated rosin in a mass ratio of 1:3; the solvent is a mixture of DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol in a mass ratio of 1:1:1; and the thixotropic agent is a mixture of N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide in a mass ratio of 2:1.

[0031] Example 1

[0032] A soldering paste for solder paste with low voiding rate: the components and mass contents of the soldering paste are 0.1% of a chelating agent, 0.2% of a leveling agent BYK300, 2% of a nonionic low-foaming surfactant, 10% of an activator (a mixture of trimethylbutylene glycol and 2-dihydroxymethylpropionic acid DMPA in a mass ratio of 3:5), 2% of a thickener, 37% of a rosin resin, 40% of a solvent, and 8.7% of a thixotropic agent.

[0033] A method for preparing a soldering paste for low voiding rate solder paste comprises the following steps:

[0034] (1) Calculate the mass of the materials according to the ratio of the above materials, weigh them, and place them in corresponding containers respectively;

[0035] (2) Heat HM8208 resin and hydrogenated rosin to melt and mix evenly, and cool to form a film-forming agent;

[0036] (3) DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol are mixed and stirred to prepare a solvent;

[0037] (4) mixing the thixotropic agent N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide to form a thixotropic agent;

[0038] (5) First, add the solvent, film-forming agent and thickener into the reactor, heat and stir until they are completely melted. Keep the temperature at 160°C and stir for 5 minutes, then turn off the heat. Slowly add the thixotropic agent and stir until it melts. Then add the activator, non-ionic low-foaming surfactant, chelating agent and leveling agent in sequence. After the materials are completely melted, stir for 5 to 8 minutes. When the temperature drops to 130°C, transfer the molten flux to a container and seal it. Cool it to room temperature to obtain the flux paste.

[0039] Example 2

[0040] A soldering paste for solder paste with low voiding rate: the components and mass contents of the soldering paste are 0.5% of a chelating agent, 0.1% of a leveling agent BYK301, 4.4% of a nonionic low-foaming surfactant, 8% of an activator (trimethylbutylene glycol and 2-dihydroxymethylpropionic acid DMPA mixed in a mass ratio of 4:3), 5% of a thickener, 40% of a rosin resin, 35% of a solvent, and 7% of a thixotropic agent.

[0041] The preparation method is the same as that of Example 1.

[0042] Example 3

[0043] A soldering paste for solder paste with low voiding rate: the soldering paste comprises the following components and weight contents: 0.35% of a chelating agent, 0.15% of a leveling agent (BYK300 and BYK301 are mixed in a mass ratio of 1:1), 6.5% of a nonionic low-foaming surfactant, 5% of an activator (trimethylbutylene glycol and 2-dihydroxymethylpropionic acid DMPA are mixed in a mass ratio of 5:4), 3% of a thickener, 41% of a rosin resin, 38% of a solvent, and 6% of a thixotropic agent.

[0044] The preparation method is the same as that of Example 1.

[0045] Example 4

[0046] A soldering paste for solder paste with low voiding rate: the components and mass contents of the soldering paste are as follows: 0.4% of a chelating agent, 0.03% of a leveling agent (BYK300 and BYK302 mixed in a mass ratio of 1:1), 8% of a non-ionic low-foaming surfactant, 7.07% of an activator (trimethylbutylene glycol and 2-dihydroxymethylpropionic acid DMPA mixed in a mass ratio of 7:2), 4% of a thickener, 35% of a rosin resin, 36% of a solvent, and 9.5% of a thixotropic agent.

[0047] The preparation method is the same as that of Example 1.

[0048] Example 5

[0049] A soldering paste for solder paste with low voiding rate: the soldering paste comprises the following components and mass contents: 0.42% of a chelating agent, 0.08% of a leveling agent (BYK301 and BYK302 mixed in a mass ratio of 1:1), 10% of a nonionic low-foaming surfactant, 3% of an activator (trimethylbutylene glycol and 2-dihydroxymethylpropionic acid DMPA mixed in a mass ratio of 4:5), 3% of a thickener, 45% of a rosin resin, 32% of a solvent, and 6% of a thixotropic agent.

[0050] The preparation method is the same as that of Example 1.

[0051] The solder pastes of Examples 1 to 5 were prepared into solder pastes with SAC305 solder powder, and compared with ALPHA CVP390, a low void solder paste of the same type available on the market. After reflow soldering, the test board was tested for BGA void rate using an X-ray device. The results are shown in the following table:

[0052] Serial number product BGA void rate % 1 Solder paste using the solder paste of Example 1 ＜7.6% 2 Solder paste using the solder paste of Example 2 ＜7.4% 3 Solder paste using the solder paste of Example 3 ＜7.8% 4 Solder paste using the solder paste of Example 4 ＜6.7% 5 Solder paste using the solder paste of Example 5 ＜6.5% 6 Commercially available ALPHA CVP390 solder paste ＜10.4%

[0053] From the above table and Figures 1 to 6 It can be seen that the solder paste BGA solder joint void rate prepared by the solder paste of the present invention is extremely low, which can effectively avoid the solder joint reliability problem caused by voids after solder paste welding, and is particularly suitable for high-reliability precision welding.

[0054] Unless otherwise specified, the percentages described in the present invention are all mass percentages. The materials used in the present invention can be purchased online or directly purchased offline. Other embodiments can also be prepared by limiting other raw material ratio ranges in the claims. The solder paste prepared by the present invention can produce SnAgCu series solder paste products, and the product has a low void rate and a simple preparation method.

Claims

1. A solder paste for low voiding rate solder paste, characterized in that: The components and mass contents of the soldering flux are chelating agent 0.1-0.5%, leveling agent 0.01-0.2%, non-ionic low-foaming surfactant 2.0%-10.0%, activator 3%-10%, thickener 2%-5%, and the balance is a mixture of rosin resin, solvent and thixotropic agent; The chelating agent is prepared by compounding HYNIC and DOTA in a mass ratio of 2:1; The leveling agent is a mixture of one or more of BYK300, BYK301, and BYK302; The thickener is prepared by compounding TT-935 and polyisobutylene HV300 in a mass ratio of 1:1; The mixture comprises 35-45% rosin resin, 30-40% solvent and 5-11% thixotropic agent; wherein the rosin resin is a mixture of HM8208 resin and hydrogenated rosin in a mass ratio of 1:3; the solvent is a mixture of DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol in a mass ratio of 1:1:1; and the thixotropic agent is a mixture of N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide in a mass ratio of 2:

1.

2. The method for preparing a soldering paste with low voiding rate as claimed in claim 1, characterized in that: The following steps are involved: (1) Calculate the mass of the materials according to the ratio of each material, weigh them, and place them in corresponding containers; (2) Heat HM8208 resin and hydrogenated rosin to melt and mix evenly, and cool to form a film-forming agent; (3) Mix and stir the solvent DBE dibasic ester, hexyldecanol and 2-methyl-2,4-pentanediol evenly; (4) mixing the thixotropic agent N,N'-1,6-hexanediylbis[N'-octadecyl-urea] and N,N'-1 / 2-ethylenediylbisoctadecylamide evenly; (5) First, add the solvent, film-forming agent and thickener into the reactor, heat and stir until they are completely melted. Keep the temperature at 160°C and stir for 5 minutes, then turn off the heat. Slowly add the thixotropic agent and stir until it melts. Then add the activator, non-ionic low-foaming surfactant, chelating agent and leveling agent in sequence. After the materials are completely melted, stir for 5 to 8 minutes. When the temperature drops to 130°C, transfer the molten flux to a container and seal it. Cool it to room temperature to obtain the flux paste.

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