Flux paste for moisture-proof soldering paste and preparation method of flux paste

Abstract

The invention discloses flux paste for moisture-proof soldering paste and a preparation method of the flux paste. The flux paste comprises the following components in percentage by mass: 15-25% of a film-forming agent, 15-25% of a thickening agent, 6-12% of an anti-settling agent, 5-15% of an active agent, 2-4% of a corrosion inhibitor and 35-45% of a solvent. The film-forming agent is prepared by compounding polyamide resin and linear low-density polyethylene according to a mass ratio of 3: 1. After the soldering paste prepared from the flux paste is subjected to reflow soldering, a layer of uniform and transparent thin film can be formed by residues to cover a welding spot, so that the moisture-proof and acid-base-proof functions are achieved, the short circuit problem caused by electromigration of a fine-pitch bonding pad can be effectively solved, normal operation of an electronic device is protected, and electrical faults are reduced; after soldering paste of the soldering flux is used for soldering, the three-proofing paint treatment process for a PCBA (Printed Circuit Board Assembly) is reduced, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0002] The invention belongs to the technical field of soft soldering materials, and as a soldering material for electronic products, specifically relates to a soldering paste for moisture-proof solder paste and a preparation method thereof. Background Art

[0004] Solder paste is increasingly used as a welding material in the SMT field. The existing solder paste film-forming agent is rosin, and the residual component after welding is rosin without moisture-proof function. It will absorb moisture and turn white when in humid air or acid-base environment, and the rosin acid will react chemically with the metal pad under the action of the acid-base medium, causing severe corrosion and short circuit of the pad. Therefore, after soldering the solder paste, it is necessary to apply three-proof paint on the PCBA circuit board for three-proof paint treatment to prevent corrosion of the solder joints caused by moisture, accelerate the growth of dendrites between the pads, and shorten the service life of electronic products. However, the three-proof paint process has high construction costs, cumbersome operations, and difficult maintenance. Therefore, it is necessary to develop a specific solder paste with moisture-proof function to reduce the need for three-proof paint treatment after welding electronic products. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the prior art and provide a flux paste for moisture-proof solder paste and a preparation method thereof.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A flux paste for moisture-proof solder paste, the flux paste comprising 15-25% by mass of a film former, 15-25% by mass of a thickener, 6-12% by mass of an anti-settling agent, 5-15% by mass of an activator, 2-4% by mass of a corrosion inhibitor and 35-45% by mass of a solvent:

[0009] The film-forming agent is a compound of polyamide resin and linear low-density polyethylene (LLDPE) resin in a mass ratio of 3:1;

[0010] The thickener is a compound of polyisobutylene PB950 and PB1400 in a mass ratio of 2:1;

[0011] The anti-settling agent is prepared by compounding AKN-7120 and CRAYVALLAC ULTRA polyamide wax in a mass ratio of 1:1;

[0012] The active agent is a compound of rosin alcohol ether surfactant, active agent GE-511, and 2-pyridine carboxylic acid in a mass ratio of 1:1:4;

[0013] The corrosion inhibitor is prepared by compounding methylbenzotriazole (TTA) and mercaptobenzothiazole (MBT) in a mass ratio of 5:2.

[0014] The solvent is prepared by mixing α-[(tetrahydro-2-furan)methyl]-W-hydroxypoly(oxy-1,2-ethylenediyl) and triethylene glycol butyl ether in a mass ratio of 2:1.

[0015] The present invention provides a method for preparing a moisture-proof solder paste flux paste, comprising the following steps:

[0016] (1) Weigh the film-forming agent, solvent and thickener and place them in an emulsifier. Heat at a rate of 3-4°C / min and a dispersion rate of 1000rpm to disperse, stir and emulsify.

[0017] (2) When the temperature rises to 60-100°C, add the anti-settling agent and emulsify for 10-15 minutes, then add the corrosion inhibitor and activator in sequence, and keep the temperature and emulsify for 2-3 hours;

[0018] (3) Turn off the heating, cool down and emulsify. When the temperature drops below 30°C, stop emulsification and take out the cream;

[0019] (4) Use a three-roll mill to grind the paste particles to less than 10 um to obtain the finished solder paste.

[0020] The present invention has at least the following advantages:

[0021] (1) The present invention analyzes the technical defects of existing solder paste after welding and the formation mechanism of the technical defects: the flux residue after existing solder paste welding flows greatly and is distributed on the pad and impedance film, connecting two fine-pitch pads. When wet, it adheres to dust and gradually corrodes in an acid-base environment, destroys the grain boundary of the pad, and rapidly generates dendrites, resulting in short circuit of the components. The present invention uses polyamide resin and linear low-density polyethylene (LLDPE) resin as film-forming agents. The residue after solder paste reflow soldering will form a uniform and transparent film covering the solder joint. This film has moisture-proof and acid-base resistant functions, effectively isolates moisture in the air to protect the circuit board from moisture invasion, resists the erosion of acids, alkalis and other organic salts, protects the normal operation of electronic devices, and reduces the occurrence of electrical failures.

[0022] (2) After soldering with the solder paste using the flux of the present invention, the three-proof coating process for the circuit board PCBA is reduced, the production cost is reduced and the production efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The solder paste of the solder paste of Examples 1-5 of the present invention and the solder paste solder joint residue distribution state diagram of the commercially available solder paste;

[0025] Figure 2 The figure is a corrosion state diagram of the solder paste of the solder paste of the present invention and the solder paste solder joints of commercially available solder paste under high temperature and high humidity. DETAILED DESCRIPTION

[0027] The content of the present invention is further described below in conjunction with embodiments.

[0028] The thickener used in the following Examples 1-5 is a compound of polyisobutylene PB950 and PB1400 in a mass ratio of 1:2; the anti-settling agent is a compound of AKN-7120 and CRAYVALLAC ULTRA polyamide wax in a mass ratio of 1:1; the active agent is a rosin alcohol ether surfactant, and the active agents GE-511 and 2-pyridinecarboxylic acid are compounded in a mass ratio of 1:1:4; the corrosion inhibitor is The invention discloses a novel novel film-forming agent comprising polyamide resin and linear low-density polyethylene (LLDPE) in a mass ratio of 3:1. The film-forming agent comprises polyamide resin and linear low-density polyethylene (LLDPE) in a mass ratio of 3:1.

[0029] Example 1

[0030] This embodiment provides a flux paste for moisture-proof solder paste, wherein the flux paste has the following mass percentage ratio: film former 15%, thickener 20%, anti-settling agent 12%; activator 8.5%; corrosion inhibitor 4.5%; solvent 40%;

[0031] A method for preparing a moisture-proof solder paste flux paste comprises the following steps:

[0032] (1) Place the film-forming agent, solvent and thickener weighed in the following proportions into an emulsifier, heat at a rate of 4°C / min, set the dispersion rate at 1000 rpm, and disperse, stir and emulsify;

[0033] (2) When the temperature of the emulsion is raised to 80°C, an anti-settling agent is added and emulsified for 10-15 minutes, and then a corrosion inhibitor and an active agent are added in sequence, and the temperature is kept and emulsified for 3 hours;

[0034] (3) Stop heating and cool down the emulsification. When the temperature drops to 30°C, stop emulsification and take out the cream;

[0035] (4) Use a three-roll mill to grind the paste particles to less than 10um to obtain the finished solder paste.

[0036] Example 2

[0037] This embodiment provides a flux paste for moisture-proof solder paste, wherein the flux paste has the following mass percentage ratio: film former 25%, thickener 15%, anti-settling agent 6; activator 7%; corrosion inhibitor 2%; solvent 45%;

[0038] A method for preparing a moisture-proof solder paste flux paste comprises the following steps:

[0039] (1) Place the film-forming agent, solvent and thickener weighed in the following proportions into an emulsifier, heat at a rate of 3°C / min, set the dispersion rate at 1000 rpm, and disperse, stir and emulsify;

[0040] (2) When the temperature of the emulsion is raised to 90°C, an anti-settling agent is added and emulsified for 10-15 minutes, and then a corrosion inhibitor and an active agent are added in sequence, and the temperature is kept and emulsified for 2.5 hours;

[0041] (3) Stop heating and cool down the emulsification. When the temperature drops to 30°C, stop emulsification and take out the cream;

[0042] (4) Use a three-roll mill to grind the paste particles to less than 10um to obtain the finished solder paste.

[0043] Example 3

[0044] This embodiment provides a flux paste for moisture-proof solder paste, wherein the flux paste has the following mass percentage ratio: film former 18%, thickener 25%, anti-settling agent 8; activator 12%; corrosion inhibitor 2%; solvent 35%;

[0045] A method for preparing a moisture-proof solder paste flux paste comprises the following steps:

[0046] (1) Place the film-forming agent, solvent and thickener weighed in the following proportions into an emulsifier, heat at a rate of 3°C / min, set the dispersion rate at 1000 rpm, and disperse, stir and emulsify;

[0047] (2) When the temperature of the emulsion is raised to 70°C, an anti-settling agent is added and emulsified for 10-15 minutes, and then a corrosion inhibitor and an active agent are added in sequence, and the temperature is kept and emulsified for 3 hours;

[0048] (3) Stop heating and cool down the emulsification. When the temperature drops to 30°C, stop emulsification and take out the cream;

[0049] (4) Use a three-roll mill to grind the paste particles to less than 10um to obtain the finished solder paste.

[0050] Example 4

[0051] This embodiment provides a flux paste for moisture-proof solder paste, wherein the flux paste has the following mass percentage ratio: film former 21%, thickener 18%, anti-settling agent 8; activator 15%; corrosion inhibitor 2%; solvent 36%;

[0052] A method for preparing a moisture-proof solder paste flux paste comprises the following steps:

[0053] (1) Place the film-forming agent, solvent and thickener weighed in the following proportions into an emulsifier, heat at a rate of 4°C / min, set the dispersion rate at 1000 rpm, and disperse, stir and emulsify;

[0054] (2) When the temperature of the emulsion is raised to 80°C, an anti-settling agent is added and emulsified for 10-15 minutes, and then a corrosion inhibitor and an active agent are added in sequence, and the temperature is kept and emulsified for 3 hours;

[0055] (3) Stop heating and cooling the emulsification. When the temperature drops to 30°C, stop emulsification and remove the emulsified flux;

[0056] (4) Use a three-roll mill to grind the emulsified flux paste to less than 10um to obtain the finished flux paste.

[0057] Example 5

[0058] This embodiment provides a flux paste for moisture-proof solder paste, wherein the flux paste has the following mass percentage ratio: film former 23%, thickener 17%, anti-settling agent 17; activator 8%; corrosion inhibitor 3%; solvent 42%;

[0059] A method for preparing a moisture-proof solder paste flux paste comprises the following steps:

[0060] (1) Place the film-forming agent, solvent and thickener weighed in the following proportions into an emulsifier, heat at a rate of 3°C / min, set the dispersion rate at 1000 rpm, and disperse, stir and emulsify;

[0061] (2) When the temperature of the emulsion is raised to 70°C, an anti-settling agent is added and emulsified for 10-15 minutes, and then a corrosion inhibitor and an active agent are added in sequence, and the temperature is kept and emulsified for 3 hours;

[0062] (3) Stop heating and cool down the emulsification. When the temperature drops to 30°C, stop emulsification and take out the emulsified cream.

[0063] (4) Use a three-roll mill to grind the paste particles to less than 10um to obtain the finished solder paste.

[0064] The raw materials used for preparing the solder paste of the present invention can all be purchased commercially, and the reactor used in the preparation method thereof is an existing technical device.

[0065] Performance evaluation:

[0066] The solder paste prepared in the above-mentioned Examples 1-5 was prepared with No. 4 solder powder of SnAg0.3Cu0.7 to prepare solder paste, and reflow soldering was performed under the same conditions as the commercially available SnAg0.3Cu0.7 moisture-proof solder paste.

[0067] The test results of Examples 1-5 and commercially available SnAg0.3Cu0.7 solder paste are shown in the following table:

[0068]

[0069] The residual state of each solder joint is as follows Figure 1 As shown, the solder paste residue on the commercially available solder joint is wrapped in the lower middle part of the solder joint, and there is no residue on the top of the solder joint, forming a distribution state that gradually decreases from the bottom to the top; while the solder paste residue of the present invention forms a layer of transparent film that evenly covers the solder joint.

[0070] A sample (the solder paste of the present invention) was randomly selected from Examples 1-5 and the commercial solder paste was tested for corrosion of the solder joints under a high temperature and high humidity environment of 85°C and 85%RH. The results are shown in FIG. Figure 2 After high temperature and high humidity, the residue on the solder joint surface of the commercially available solder paste softens and turns white, and there is corrosion around the solder joint. After corrosion, the solder paste of the present invention has no change on the residue on the solder joint surface, and the solder joint is not corroded.

[0071] Unless otherwise specified, all percentages described in the present invention are by mass percentages.

[0072] The materials used in the present invention can be purchased online or directly purchased offline. Other embodiments of the present invention can also be prepared by other ratio ranges in the claims and the specification. The aforementioned embodiments are only illustrative and are used to explain some features of the method of the present invention. The embodiments presented herein are only descriptions of selected implementation methods based on the combination of all possible embodiments. The attached claims are intended to require the widest possible range that can be imagined.

Claims

1. A flux paste for moisture-proof solder paste, characterized in that: The soldering paste includes 15-25% by mass of a film former, 15-25% by mass of a thickener, 6-12% by mass of an anti-settling agent, 5-15% by mass of an activator, 2-4% by mass of a corrosion inhibitor and 35-45% by mass of a solvent: The film-forming agent is a compound of polyamide resin and linear low-density polyethylene (LLDPE) resin in a mass ratio of 3:1; The thickener is a compound of polyisobutylene PB950 and PB1400 in a mass ratio of 2:1; The anti-settling agent is prepared by compounding AKN-7120 and CRAYVALLAC ULTRA polyamide wax in a mass ratio of 1:1; The active agent is a compound of rosin alcohol ether surfactant, active agent GE-511, and 2-pyridine carboxylic acid in a mass ratio of 1:1:4; The corrosion inhibitor is prepared by compounding methylbenzotriazole (TTA) and mercaptobenzothiazole (MBT) in a mass ratio of 5:2; The solvent is prepared by compounding α-[(tetrahydro-2-furan)methyl]-W-hydroxypoly(oxy-1,2-ethylenediyl) and triethylene glycol butyl ether in a mass ratio of 2:

1.

2. The method for preparing a moisture-proof solder paste flux paste according to claim 1, characterized in that: The following steps are involved: (1) Weigh the film-forming agent, solvent and thickener and place them in an emulsifier. Heat at a rate of 3-4°C / min and a dispersion rate of 1000rpm to disperse, stir and emulsify. (2) When the temperature rises to 60-100°C, add the anti-settling agent and emulsify for 10-15 minutes, then add the corrosion inhibitor and activator in sequence, and keep the temperature and emulsify for 2-3 hours; (3) Turn off the heating, cool down and emulsify. When the temperature drops below 30°C, stop emulsification and take out the cream; (4) Use a three-roll mill to grind the paste particles to less than 10 um to obtain the finished solder paste.

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