Washing type tin-bismuth low-temperature solder paste for aluminum welding and preparation method of washing type tin-bismuth low-temperature solder paste

Abstract

The invention discloses washing type tin-bismuth low-temperature solder paste for aluminum welding and a preparation method thereof. The solder paste is composed of, by weight, 80%-85% of tin-based brazing filler metal powder and 15%-20% of flux paste. The tin-based brazing filler metal powder is a SnBi system alloy; the flux paste comprises 50 to 65 wt.% of an active agent, 2 to 3 wt.% of a thickening agent, 15 to 25 wt.% of a film-forming coating agent and 15 to 25 wt.% of an organic solvent. The solder paste has good wettability on an aluminum welding surface, residues after welding can be cleaned up with warm water, the cleaned welding spots have good reliability, and the film-forming coating agent can effectively coat the active agent and other components to prevent the solder paste from becoming dry. The method is suitable for welding of various aluminum bonding pad components, and particularly has a good effect on welding of an aluminum bonding pad light source plate and an aluminum sheet type radiator.

Description

Technical Field

[0001] The invention relates to the technical field of solder paste for aluminum welding and a preparation method thereof, and in particular to a water-washable tin-bismuth low-temperature solder paste for aluminum welding and a preparation method thereof. Background Art

[0002] Solder paste plays a key role in the welding of electronic products, which not only plays an electrical connection role, but also plays a physical welding role. In the field of household appliances, many structural parts use materials such as copper plates and aluminum plates, especially heat sinks and LED light source boards in electronic products. Aluminum not only has good electrical and thermal conductivity, but also has suitable strength, good corrosion resistance, low density and low cost. In most industries that do not require high heat dissipation, aluminum plates can be used to perfectly replace copper plates. Copper plates have good solderability, and the copper oxide film on the surface can be easily removed by the active substances in the flux paste. However, there is a dense and firm oxide film on the surface of aluminum, and the degree of surface oxidation of different aluminum plates varies greatly. The active substances of ordinary solder paste are difficult to remove the metal oxides on its surface, making it difficult to carry out low-temperature soldering smoothly, resulting in poor welding results. In order to ensure sufficient activity during welding, the solder paste currently used for aluminum plate welding generally has the characteristics of high residue and high corrosion, and the high residue also affects the reliability of the product. For example, Chinese patent application CN104625483A discloses a low-residue and low-corrosion aluminum solder paste and its preparation method, which uses a large amount of tetrahydroxypropylethylenediamine hydrofluoride. Although the solder paste has good wettability on the aluminum surface, the storage stability of the solder paste cannot be well solved, and the presence of residues will still affect the reliability of the solder joints. Chinese patent application CN103317260A discloses a solder paste for aluminum and aluminum alloy soldering and its preparation method. The solder paste is composed of 80-90% solder alloy powder and 10-20% flux, wherein the flux is composed of: 5-15% heavy metal fluoride activator, 65-75% hydrofluoride of polyhydroxyamine, and 10-25% ethylene glycol. The solder paste has strong activity and can obtain solder joints with strong bonding force. However, the solder paste produces a large number of bubbles and irritating gases during welding, and there is a lot of residue after welding, which is easy to corrode the solder joints and affect the service life. In addition, the solder paste is easy to dry out and affect the printing performance. Chinese patent CN102922162A discloses a solder paste for aluminum solder and a preparation method thereof. The solder paste is composed of 5-30% flux and 70-95% tin powder, wherein the flux is composed of: 80% hydroxylamine fluoride, 15% metal active salt, 2% active agent, and 3% corrosion inhibitor. This solder paste also has the problem of a large amount of residue after welding and severe corrosion of solder joints.

[0003] There are many public documents on solder paste for aluminum welding, but there are generally problems such as large residues, large residual corrosion, or insufficient storage stability of solder paste. Summary of the invention

[0004] In view of the deficiencies of the prior art, the purpose of the present invention is to solve the deficiencies of the prior art and provide a water-washable tin-bismuth low-temperature solder paste for aluminum welding that can significantly improve the ability of solder paste to remove oxide film on the surface of aluminum plates, has excellent wettability to aluminum plates, and can clean the post-welding residues with warm water and has reliable solder joints. The present invention also provides a method for preparing the solder paste.

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

[0006] A water-washable tin-bismuth low-temperature solder paste for aluminum welding, the solder paste consisting of 80-85wt.% of tin-based solder powder and 15-20wt.% of flux paste; the tin-based solder powder is a SnBi alloy; the flux paste comprises 50-65wt.% of a composite activator, 2-3wt.% of a thickener, 15-25wt.% of a composite film-forming coating agent, and 15-25wt.% of an organic solvent.

[0007] Furthermore, the compound active agent is compounded from three materials: D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone, and tetramethyldipropylenetriamine hydrofluoride.

[0008] Furthermore, in the composite active agent, the mass ratio of D-glucosamine hydrochloride: 2-amino-2',4'-difluoroacetophenone: tetramethyldipropylenetriamine hydrofluoride is 1: (2-3): (4-5).

[0009] Furthermore, the thickener is sodium carboxymethyl cellulose.

[0010] Furthermore, the composite film-forming coating agent is composited from four water-soluble polymer materials: polymaleic anhydride, polyvinyl pyrrolidone, PPG400, and polyacrylamide.

[0011] Furthermore, in the composite film-forming coating agent, the mass ratio of polymaleic anhydride: polyvinyl pyrrolidone: PPG400: polyacrylamide is (2-3): (1-2): (4-5): 1.

[0012] Furthermore, the organic solvent is a mixture of two or more of 1,2-propylene glycol, dipropylene glycol, and polyethylene glycol 200.

[0013] The method for preparing the water-washable tin-bismuth low-temperature solder paste for aluminum welding of the present invention comprises the following steps:

[0014] (1) Adding a compound active agent and a compound film-forming agent into a reaction kettle, coating the compound active agent with the compound film-forming agent, and then adding a thickener and an organic solvent until it becomes a uniform emulsion, pouring it into a container, and cooling it at room temperature to obtain a soldering solder paste;

[0015] (2) Grind the solder paste until the grain size is less than 100 μm;

[0016] (3) The ground solder paste is stirred and mixed with tin-based solder powder to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

[0017] Furthermore, the raw materials for preparing the compound active agent are added into a container, heated to 120-130° C. to prepare the compound active agent, and cooled for standby use.

[0018] Furthermore, various raw materials for preparing the composite film-forming coating agent are added into a container and heated to 80-100° C. to prepare the composite film-forming coating agent.

[0019] The present invention aims at the problems that the existing aluminum plate solder paste has more residue, larger residual corrosion, and insufficient storage stability of the solder paste, and the like. The present invention adopts a compound active agent and a compound film-forming coating agent for matching. The compound active agent can significantly improve the solder paste's ability to remove the oxide film on the aluminum plate surface, so that the solder paste has excellent wettability to the aluminum plate. This is because after the D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone, and tetramethyldipropylenetriamine hydrofluoride in the compound active agent are compounded, sufficient amino groups / hydrofluoric acid / hydrochloric acid / fluoride ions and other active factors can be released during the high-temperature welding process to remove the aluminum surface oxide film. The film-forming coating agent can effectively coat the active agent and other components to prevent the solder paste from drying out. The compound film-forming coating agent can also slow down the chemical reaction between the active agent and the tin powder in the solder paste, so that the solder paste has good storage performance. This is because the polymaleic anhydride, polyvinyl pyrrolidone, PPG400 and polyacrylamide in the compound film-forming coating agent can form a low surface tension polymer film-forming agent after heating, which has an excellent coating effect. The active agent, thickener, film-forming coating agent and organic solvent used in the present invention all have good water solubility, so that the residue after welding can be cleaned with warm water, and the cleaned solder joint has good reliability.

[0020] The solder paste of the present invention is suitable for welding various aluminum pad components, and can weld aluminum plate devices or structural parts firmly and reliably, which can significantly improve product performance and extend its service life, especially for aluminum pad light source panels and aluminum sheet heat sinks.

[0021] The solder paste preparation method of the present invention is simple, the process is easy to control, and the prepared product has stable performance. DETAILED DESCRIPTION

[0022] The content of the present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0023] Example 1

[0024] A water-washable tin-bismuth low-temperature solder paste for aluminum welding comprises 85wt.% of SnBi58 powder and 15wt.% of solder paste. The solder paste ingredients are: 7g of D-glucosamine hydrochloride, 14g of 2-amino-2',4'-difluoroacetophenone, 30g of tetramethyldipropylenetriamine hydrofluoride, 2g of sodium carboxymethyl cellulose, 6g of polymaleic anhydride, 4g of polyvinyl pyrrolidone, 10g of PPG400, 2g of polyacrylamide, 15g of 1,2-propylene glycol, and 10g of dipropylene glycol.

[0025] Preparation method of solder paste:

[0026] (1) Add D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone, and tetramethyldipropylenetriamine hydrofluoride into a beaker, heat to about 125°C, prepare a composite active agent, and cool it for use; then add polymaleic anhydride, polyvinyl pyrrolidone, PPG400, and polyacrylamide into a reactor, heat to about 90°C, and prepare a composite film-forming coating agent; then add the prepared composite active agent into the reactor, use the composite film-forming agent to coat the composite active agent, and then add sodium carboxymethyl cellulose, 1,2-propylene glycol, and dipropylene glycol until it becomes a uniform emulsion, pour it into a container, and place it at room temperature for cooling to obtain a solder paste;

[0027] (2) Grinding the solder paste until the grain size is less than 100 μm;

[0028] (3) Take 75 g of the ground solder paste and 425 g of SnBi58 powder and stir and mix them to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

[0029] Example 2

[0030] A water-washable tin-bismuth low-temperature solder paste for aluminum welding comprises 82wt.% of SnBi58 powder and 18wt.% of solder paste. The solder paste comprises: 80g of D-glucosamine hydrochloride, 160g of 2-amino-2',4'-difluoroacetophenone, 320g of tetramethyldipropylenetriamine hydrofluoride, 20g of sodium carboxymethyl cellulose, 60g of polymaleic anhydride, 40g of polyvinyl pyrrolidone, 100g of PPG400, 20g of polyacrylamide, 100g of 1,2-propylene glycol and 100g of polyethylene glycol 200.

[0031] Preparation method of solder paste:

[0032] (1) Add D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone, and tetramethyldipropylenetriamine hydrofluoride into a beaker, heat to 125-130°C to prepare a composite active agent, cool and set aside, then add polymaleic anhydride, polyvinyl pyrrolidone, PPG400, and polyacrylamide into a reactor, heat to 80-85°C to prepare a composite film-forming coating agent, then add the prepared composite active agent into the reactor, use the composite film-forming agent to coat the composite active agent, then add sodium carboxymethyl cellulose, 1,2-propylene glycol, and polyethylene glycol 200 until it becomes a uniform emulsion, pour into a container, and place at room temperature for cooling to obtain solder paste;

[0033] (2) Grinding the solder paste until the grain size is less than 100 μm;

[0034] (3) Take 180 g of the ground solder paste and 820 g of SnBi58 powder and stir and mix them to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

[0035] Example 3

[0036] A water-washable tin-bismuth low-temperature solder paste for aluminum welding comprises 80 wt.% of SnBi35 powder and 20 wt.% of solder paste. The solder paste comprises the following ingredients: 80 g of D-glucosamine hydrochloride, 200 g of 2-amino-2',4'-difluoroacetophenone, 370 g of tetramethyldipropylenetriamine hydrofluoride, 30 g of sodium carboxymethyl cellulose, 40 g of polymaleic anhydride, 20 g of polyvinyl pyrrolidone, 90 g of PPG400, 20 g of polyacrylamide, 100 g of 1,2-propylene glycol and 50 g of polyethylene glycol 200.

[0037] Preparation method of solder paste:

[0038] (1) Add 370g of D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone and tetramethyldipropylenetriamine hydrofluoride into a beaker, heat to 120-122°C to prepare a composite active agent, cool and set aside, then add polymaleic anhydride, polyvinyl pyrrolidone, PPG400 and polyacrylamide into a reactor, heat to 95-100°C to prepare a composite film-forming coating agent, then add the prepared composite active agent into the reactor, use the composite film-forming agent to coat the composite active agent, then add sodium carboxymethyl cellulose, 1,2-propylene glycol and polyethylene glycol 200 until it becomes a uniform emulsion, pour into a container, and place at room temperature for cooling to obtain solder paste;

[0039] (2) Grinding the solder paste until the grain size is less than 100 μm;

[0040] (3) Take 200 g of the ground solder paste and 800 g of SnBi58 powder and stir and mix them to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

[0041] Example 4

[0042] A water-washable tin-bismuth low-temperature solder paste for aluminum welding comprises 82wt.% of SnBi35 powder and 18wt.% of flux paste. The flux paste ingredients are: 60g of D-glucosamine hydrochloride, 180g of 2-amino-2',4'-difluoroacetophenone, 290g of tetramethyldipropylenetriamine hydrofluoride, 20g of sodium carboxymethyl cellulose, 60g of polymaleic anhydride, 40g of polyvinyl pyrrolidone, 120g of PPG400, 30g of polyacrylamide, 50g of 1,2-propylene glycol, 50g of dipropylene glycol, and 100g of polyethylene glycol 200.

[0043] Preparation method of solder paste:

[0044] (1) Add D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone, and tetramethyldipropylenetriamine hydrofluoride into a beaker, heat to about 128°C to prepare a composite active agent, cool and set aside, then add polymaleic anhydride, polyvinyl pyrrolidone, PPG400, and polyacrylamide into a reactor, heat to about 98°C to prepare a composite film-forming coating agent, then add the prepared composite active agent into the reactor, use the composite film-forming agent to coat the composite active agent, then add sodium carboxymethyl cellulose, dipropylene glycol, and polyethylene glycol 200 until it becomes a uniform emulsion, pour into a container, and place at room temperature for cooling to obtain solder paste;

[0045] (2) Grinding the solder paste until the grain size is less than 100 μm;

[0046] (3) 900 g of the ground solder paste was mixed with 4100 g of SnBi58 powder to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

[0047] The solder pastes prepared in the above four embodiments were tested, and the results are shown in Table 1.

[0048] Table 1 Solder paste performance test table of each embodiment

[0049]

[0050] As can be seen from Table 1, the solder paste of the present invention has good wettability, is easy to clean the residue, has good solder joint reliability, and has good storage stability.

[0051] The above embodiments are only some embodiments of the present invention and are not intended to limit the protection scope of the present invention. All embodiments obtained by data changes and replacement of equivalent technical means based on the scope of the claims of the present invention belong to the protection scope of the present invention.

Claims

1. A water-washable tin-bismuth low-temperature solder paste for aluminum welding, characterized in that: The solder paste is composed of 80-85wt.% of tin-based solder powder and 15-20wt.% of flux paste; the tin-based solder powder is a SnBi alloy; the flux paste includes 50-65wt.% of a composite activator, 2-3wt.% of a thickener, 15-25wt.% of a composite film-forming coating agent, and 15-25wt.% of an organic solvent.

2. The water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 1, characterized in that: The compound active agent is compounded from three materials: D-glucosamine hydrochloride, 2-amino-2',4'-difluoroacetophenone and tetramethyldipropylenetriamine hydrofluoride.

3. A water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 2, characterized in that: In the composite active agent, the mass ratio of D-glucosamine hydrochloride: 2-amino-2',4'-difluoroacetophenone: tetramethyldipropylenetriamine hydrofluoride is 1: (2-3): (4-5).

4. A water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 1, 2 or 3, characterized in that: The thickener is sodium carboxymethyl cellulose.

5. A water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 1, 2 or 3, characterized in that: The composite film-forming coating agent is composited from four water-soluble polymer materials: polymaleic anhydride, polyvinyl pyrrolidone, PPG400 and polyacrylamide.

6. The water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 5, characterized in that: In the composite film-forming coating agent, the mass ratio of polymaleic anhydride: polyvinyl pyrrolidone: PPG400: polyacrylamide is (2-3): (1-2): (4-5):

1.

7. A water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 1, 2 or 3, characterized in that: The organic solvent is a mixture of two or more of 1,2-propylene glycol, dipropylene glycol and polyethylene glycol 200.

8. The method for preparing a water-washable tin-bismuth low-temperature solder paste for aluminum welding according to any one of claims 1 to 7, characterized in that: The steps are as follows: (1) Adding a compound active agent and a compound film-forming agent into a reaction kettle, coating the compound active agent with the compound film-forming agent, and then adding a thickener and an organic solvent until it becomes a uniform emulsion, pouring it into a container, and cooling it at room temperature to obtain a soldering solder paste; (2) Grind the solder paste until the grain size is less than 100 μm; (3) The ground solder paste is stirred and mixed with tin-based solder powder to obtain the water-washable tin-bismuth low-temperature solder paste for aluminum welding.

9. The method for preparing a water-washable tin-bismuth low-temperature solder paste for aluminum welding as claimed in claim 8, characterized in that: The raw materials for preparing the compound active agent are added into a container, heated to 120-130° C. to prepare the compound active agent, and cooled for later use.

10. The method for preparing a water-washable tin-bismuth low-temperature solder paste for aluminum welding according to claim 8, characterized in that: The raw materials for preparing the composite film-forming coating agent are added into a container and heated to 80-100° C. to prepare the composite film-forming coating agent.

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