A low-solids content flux and its preparation method

Abstract

This invention discloses a low-solids content flux and its preparation method, relating to the field of fluxes. The flux comprises the following components: 2-8% activator, 3-6% surfactant, 0.2-0.8% film-forming agent, 0.2-0.6% antioxidant, 0-0.8% additive, 0.1-0.5% corrosion inhibitor, and the remainder is solvent. The total mass percentage of all components is 100%. This flux is halogen-free, has a low solids content, uses deionized water as a solvent, has low volatile gases, no irritating odor, and does not cause solder splattering. By using organic acids with different activities and boiling points to form an activation gradient, it can remove oxide films from metal surfaces and help form solder joints. Through multiple hydrogen bonds, it can form a multi-layer structure, effectively avoiding the problems caused by incomplete film formation by a single corrosion inhibitor. It has good film-forming properties and can effectively protect the solder and substrate metal from oxidation during the soldering process.

Description

Technical Field

[0001] This invention relates to the field of fluxes, specifically to a low-solids-content flux and its preparation method. Background Technology

[0002] Flux is an indispensable part of the soldering process, its main function being to remove oxides from metal surfaces. In addition, it protects the soldering zone, reduces the surface tension of the liquid solder, improves the flowability of the liquid solder, enhances its filling ability, and improves heat transfer and balance in the soldering zone. Although modern fluxes are more environmentally friendly and healthier, they still have the following problems: high surface tension, insufficient ability to remove impurities and oxides, poor flux wetting and spreading properties, and poor film-forming properties leading to insufficient antioxidant protection can all significantly reduce the flux's soldering performance. Excessive post-soldering residue or reactions between organic solvents in the flux and solder resist inks severely affect the cleanliness of the PCB board and product performance. Although water-based fluxes primarily use water as their solvent, water has limited solubility for many active ingredients in the flux; for example, the commonly used antioxidant BHT is insoluble in water. Therefore, in practice, most fluxes add alcohol ether organic solvents as co-solvents. Solving these problems is key to breakthroughs in flux development.

[0003] To address the aforementioned technical problems, this invention provides a low-solids content flux and its preparation method. This solution resolves the issues raised in the background art, such as poor wetting and spreading properties of the flux, poor film-forming properties leading to insufficient antioxidant protection, which can significantly reduce the flux's soldering performance and result in excessive post-soldering residues or reactions between organic solvents in the flux and solder resist inks, severely affecting the cleanliness of the PCB board and product performance.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A low-solids flux comprises: 2-8% activator, 3%-6% surfactant, 0.2-0.8% film-forming agent, 0.2-0.6% antioxidant, 0-0.8% additive, 0.1-0.5% corrosion inhibitor, and the remainder being solvent, with the total mass percentage of all components being 100%.

[0006] Preferably, the activator is one or more of lactic acid, acrylic acid, malonic acid, adipic acid, and oxalic acid, compounded with DL-malic acid, and the temperature is controlled at 30~60℃ during compounding.

[0007] Preferably, the surfactant is a compound of AEC-9NA in alcohol ether carboxylate and NP-9 in alkylphenol polyoxyethylene ether;

[0008] The mass percentage of the alcohol ether carboxylate and alkylphenol polyoxyethylene ether is 1:(1~5).

[0009] Preferably, the film-forming agent is a compound of triethanolamine and sorbitol;

[0010] The mass percentage of triethanolamine and sorbitol is (3~8):1.

[0011] Preferably, the antioxidant is hydroquinone.

[0012] Preferably, the corrosion inhibitor is a compound of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan;

[0013] The mass percentage of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan is 1:(1~15):(1~4).

[0014] Preferably, the solvent is deionized water.

[0015] Preferably, the additive is polyethylene glycol 400.

[0016] A method for preparing a low-solids content flux, applicable to the aforementioned low-solids content flux, includes the following steps:

[0017] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0018] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0019] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0020] In steps two and three, heating equipment is used to maintain the temperature within the range of 30℃ to 60℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The film-forming agent is a compound of triethanolamine and sorbitol. Sorbitol contains a large number of hydroxyl groups, which can form a large number of hydrogen bonds with triethanolamine. Under the interaction of hydrogen bonds, they cross-link with each other and construct a relatively uniform network, thus having good film-forming properties. It can effectively protect the solder and the base metal from oxidation during the welding process.

[0023] It is prepared by compounding DL-malic acid with one or more of the following activators: lactic acid, acrylic acid, malonic acid, adipic acid, and oxalic acid. DL-malic acid can form chelates with metal ions and can be used to remove metal corrosion products. It can be used in combination with other organic acids to clean metals. Multiple acids are compounded as activators to prepare flux. By using organic acids with different activities and boiling points, an activation gradient is formed to make the activation effect stronger. It can remove the oxide film on the metal surface and help form solder joints.

[0024] Using mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan as corrosion inhibitors, the combined action of these three inhibitors can improve the corrosion resistance of the flux. At the same time, mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are linked by F…H, N…H, and O…H hydrogen bonds to form a multilayer structure, which can effectively avoid the problems caused by incomplete film formation by a single corrosion inhibitor. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention. Specific implementation methods

[0026] Example 1

[0027] This embodiment prepares a low-solids content flux, comprising the following components: 2% activator, wherein the mass ratio of malonic acid, acrylic acid, and DL malic acid is 1:1:1;

[0028] 3% surfactant, wherein the mass ratio of AEC-9NA to NP-9 is 1:1;

[0029] Film-forming agent 0.2%, wherein the mass ratio of triethanolamine to sorbitol is 3:1;

[0030] Antioxidant 0.2%;

[0031] Additives 0%;

[0032] The corrosion inhibitor is 0.1%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:1:1.

[0033] The remainder is solvent, and the total mass percentage of all components is 100%.

[0034] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0035] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0036] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0037] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0038] Example 2

[0039] This embodiment prepares a low-solids content flux, comprising the following components: 6% activator, wherein the mass ratio of malonic acid, acrylic acid, and DL malic acid is 1:2:4;

[0040] 5% surfactant, wherein the mass ratio of AEC-9NA to NP-9 is 1:3;

[0041] Film-forming agent 0.5%, wherein the mass ratio of triethanolamine to sorbitol is 5:1;

[0042] Antioxidant 0.5%;

[0043] Additives 0.5%;

[0044] The corrosion inhibitor is 0.3%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:11:3.

[0045] The remainder is solvent, and the total mass percentage of all components is 100%.

[0046] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0047] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0048] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0049] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0050] Example 3

[0051] This embodiment prepares a low-solids content flux, comprising the following components: 8% activator, wherein the mass ratio of malonic acid, acrylic acid, and DL malic acid is 1:5:6;

[0052] Surfactant 8%, wherein the mass ratio of AEC-9NA to NP-9 is 1:5;

[0053] The film-forming agent is 0.8%, wherein the mass ratio of triethanolamine to sorbitol is 8:1;

[0054] Antioxidant 0.6%;

[0055] Additives 0.8%;

[0056] The corrosion inhibitor is 0.5%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:15:4.

[0057] The remainder is solvent, and the total mass percentage of all components is 100%.

[0058] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0059] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0060] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0061] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0062] Example 4

[0063] This embodiment prepares a low-solids content flux, comprising the following components: 8% activator, wherein the mass ratio of lactic acid, oxalic acid and DL malic acid is 1:5:6;

[0064] Surfactant 8%, wherein the mass ratio of AEC-9NA to NP-9 is 1:5;

[0065] The film-forming agent is 0.8%, wherein the mass ratio of triethanolamine to sorbitol is 8:1;

[0066] Antioxidant 0.6%;

[0067] Additives 0.8%;

[0068] The corrosion inhibitor is 0.5%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:15:4.

[0069] The remainder is solvent, and the total mass percentage of all components is 100%.

[0070] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0071] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0072] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0073] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0074] Example 5

[0075] This embodiment prepares a low-solids content flux, comprising the following components: 6% activator, wherein the mass ratio of lactic acid, oxalic acid and DL malic acid is 1:5:6;

[0076] Surfactant 4%, wherein the mass ratio of AEC-9NA to NP-9 is 1:2;

[0077] Film-forming agent 0.4%, wherein the mass ratio of triethanolamine to sorbitol is 6:1;

[0078] Antioxidant 0.6%;

[0079] Additives 0.8%;

[0080] The corrosion inhibitor is 0.4%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:7:2.

[0081] The remainder is solvent, and the total mass percentage of all components is 100%.

[0082] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0083] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0084] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0085] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0086] Example 6

[0087] This embodiment prepares a low-solids content flux, comprising the following components: 8% activator, wherein the mass ratio of adipic acid, malonic acid and DL malic acid is 1:1:3;

[0088] Surfactant 8%, wherein the mass ratio of AEC-9NA to NP-9 is 1:3;

[0089] Film-forming agent 0.5%, wherein the mass ratio of triethanolamine to sorbitol is 8:1;

[0090] Antioxidant 0.3%;

[0091] Additives 0.1%;

[0092] The corrosion inhibitor is 0.4%, in which the mass percentages of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are 1:4:2.

[0093] The remainder is solvent, and the total mass percentage of all components is 100%.

[0094] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0095] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0096] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0097] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0098] Comparative Example 1

[0099] In this comparative example: a low-solids content flux was prepared, comprising the following components:

[0100] The surfactant is 8%, of which DL-malic acid is the main component.

[0101] Surfactant 8%, wherein the mass ratio of AEC-9NA to NP-9 is 1:3;

[0102] Film-forming agent 0.5%, the main component of which is triethanolamine;

[0103] Antioxidant 0.3%;

[0104] Additives 0.1%;

[0105] Corrosion inhibitor 0.4%, the main component of which is hydroxypropyl chitosan;

[0106] The remainder is solvent, and the total mass percentage of all components is 100%.

[0107] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0108] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0109] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0110] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0111] Comparative Example 2

[0112] This embodiment prepares a low-solids content flux, comprising the following components: 8% activator, wherein the mass ratio of malonic acid, acrylic acid, and DL malic acid is 1:5:6;

[0113] Surfactant 8%, wherein the mass ratio of AEC-9NA to NP-9 is 1:5;

[0114] Film-forming agent 0.8%, the main component of which is triethanolamine;

[0115] Antioxidant 0.6%;

[0116] Additives 0.8%;

[0117] The corrosion inhibitor is 0.5%, and its main component is hydroxypropyl chitosan;

[0118] The remainder is solvent, and the total mass percentage of all components is 100%.

[0119] The method for preparing a low-solids content flux is applicable to the aforementioned low-solids content flux, and the specific steps are as follows:

[0120] Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator.

[0121] Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃;

[0122] Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux.

[0123] test:

[0124] Test 1: Contact Angle Test

[0125] Each sample was tested individually according to the following steps: a 50mm×50mm×0.3mm copper plate was cut, the copper plate was first treated with micro-etching solution for 30-50s, then the copper plate was cleaned with deionized water and anhydrous ethanol in sequence, dried, and the flux sample was dropped onto the horizontal copper plate surface. The contact angle of the flux sample on the copper plate was measured from 0 to 60s using a contact angle measuring instrument, and the wetting and spreading properties of the flux on the copper plate were observed.

[0126] The specific data for each sample group were obtained through the experiment as follows:

[0127] flux <![CDATA[contact angle ( o )]]> Example 1 15.3, good wetting and spreading properties, and good film-forming properties. Example 2 22.4, good wetting and spreading properties, and good film-forming properties. Example 3 20.6, good wetting and spreading properties, and good film-forming properties. Example 4 20.6, good wetting and spreading properties, and good film-forming properties. Example 5 20.6, good wetting and spreading properties, and good film-forming properties. Example 6 17.5, good wetting and spreading properties, and good film-forming properties. Comparative Example 1 14.4, poor wet spreading and poor film-forming properties. Comparative Example 2 14.2, good wetting and spreading properties, but poor film-forming properties.

[0128] The results above show that the flux of the present invention, which uses a mixture of triethanolamine and sorbitol and a mixture of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan as film-forming agents and corrosion inhibitors, exhibits good wetting and spreading properties and good film-forming properties. Comparing Example 3 and Comparative Example 2, it can be seen that the two samples differ only in the composition of the film-forming agent and the inhibitor, but there is a significant difference in film-forming properties. This indicates that the use of the film-forming agent and corrosion inhibitor in accordance with this scheme can effectively improve the film-forming properties of the flux. When using the ratio of Example 2, the flux exhibits the best film-forming properties.

[0129] Test 2: Corrosion Test of Copper Mirror

[0130] Each sample was tested individually according to the following steps: Following standard GB / T2040, a 50mm × 50mm × 0.3mm copper plate was cut, flux sample was dropped onto the copper plate, and the plate was placed in a constant temperature chamber at 80℃ for two hours. Afterward, it was placed in a constant temperature and humidity chamber at 40℃ and 93% humidity for 72 hours. The color change of the copper plate surface was observed. If a significant color change occurred, such as turning green or black, it indicated corrosion of the copper plate. The data for each group was recorded in the table below.

[0131] flux corrosive Example 1 Non-corrosive Example 2 Non-corrosive Example 3 Non-corrosive Example 4 Non-corrosive Example 5 Non-corrosive Example 6 Non-corrosive Comparative Example 1 Slight corrosion Comparative Example 2 Slight corrosion

[0132] The results above show that the combined effect of these three corrosion inhibitors can improve the corrosion resistance of the flux. Compared with the experimental examples, Comparative Examples 1 and 2 used single-component corrosion inhibitors. The mass ratio of corrosion inhibitors in Comparative Examples 1 and 5, and Comparative Examples 2 and 3 was the same. However, Comparative Examples 1 and 2 showed slight corrosion, while the samples in Examples 5 and 3 did not corrode the copper plate. This indicates that the combined effect of these three corrosion inhibitors can reduce the corrosivity of the flux. At the same time, mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan are linked by F…H, N…H, O…H hydrogen bonds to form a multilayer structure, which can effectively avoid the problems caused by incomplete film formation by a single corrosion inhibitor.

[0133] Test 3: Solid content test

[0134] Each sample was tested individually according to the following steps: 6g of flux sample (m1) was weighed and placed in a 50ml clean and dried beaker. The beaker was then placed in a ventilated oven at (110℃±2℃) for 4 hours to dry. After drying, it was removed and placed in a desiccator to cool to room temperature. It was then weighed, and dried for one hour. This drying and weighing process was repeated until the error was within 0.005g, which was considered a constant. The mass of the sample at this point was m2. Three parallel samples were prepared, and the flux solid content was calculated. Within the error range, the average value of each group of data was taken, resulting in the following data:

[0135] flux Solid content (%) Example 1 3 Example 2 2.9 Example 3 2.7 Example 4 2.5 Example 5 2.6 Example 6 2.8 Comparative Example 1 4.2 Comparative Example 2 4.1

[0136] After testing the solid content of each sample, the solid content (theoretical value) of the embodiment was lower than that of the comparison ratio, indicating that by changing the composition of the flux, we effectively reduced the solid content of the flux, greatly reducing the residue left on the PCB. Therefore, for general-purpose electronic products, the present invention can usually eliminate the need for a cleaning process.

[0137] The foregoing has shown and described the basic principles, main features, advantages, and preparation method of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-solids content flux, characterized in that, include: The composition consists of 2-8% surfactant, 3-6% film-forming agent, 0.2-0.8% antioxidant, 0.2-0.6% additive, 0.1-0.5% corrosion inhibitor, and the remainder is solvent. The total mass percentage of all components is 100%.

2. The low-solids content flux according to claim 1, characterized in that, The activator is one or more of lactic acid, acrylic acid, malonic acid, adipic acid, and oxalic acid, compounded with DL-malic acid, and the temperature is controlled at 30~60℃ during compounding.

3. The low-solids content flux according to claim 2, characterized in that, The surfactant is a compound of AEC-9NA in alcohol ether carboxylate and NP-9 in alkylphenol polyoxyethylene ether. The mass percentage of the alcohol ether carboxylate and alkylphenol polyoxyethylene ether is 1:(1~5).

4. The low-solids content flux according to claim 3, characterized in that, The film-forming agent is a compound of triethanolamine and sorbitol; The mass percentage of triethanolamine and sorbitol is (3~8):

1.

5. The low-solids content flux according to claim 4, characterized in that, The antioxidant is hydroquinone.

6. The low-solids content flux according to claim 5, characterized in that, The corrosion inhibitor is a compound of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan; The mass percentage of mercaptobenzothiazole, diethylamine, and hydroxypropyl chitosan is 1:(1~15):(1~4).

7. A low-solids content flux according to claim 6, characterized in that, The solvent is deionized water.

8. The low-solids content flux according to claim 7, characterized in that, The additive is polyethylene glycol 400.

9. A method for preparing a low-solids content flux, applicable to the low-solids content flux as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Prepare the components according to the process requirements, add the activator to the solvent, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃ to dissolve the activator. Step 2: Add the surfactant to the solution obtained in Step 1, and stir at 1200 r / min for 1 hour at a temperature of 30℃~60℃; Step 3: Add the film-forming agent, antioxidant, corrosion inhibitor and additive to the solution obtained in Step 2, stir at 1500 r / min for 1.5 h at a temperature of 30℃~60℃, and after mixing evenly, filter to obtain the flux. In steps two and three, heating equipment is used to maintain the temperature within the range of 30℃ to 60℃.

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