Low-temperature halogen-free solder paste, preparation method and application thereof

Abstract

This invention discloses a low-temperature halogen-free solder paste, its preparation method, and its application. The low-temperature halogen-free solder paste comprises: a tin-bismuth alloy, carbon nanotubes, and flux. The flux comprises, by weight percentage: 30-50% film-forming resin, 5-15% rosin-based surfactant, 3-10% activator, 2-8% thixotropic agent, and the balance being solvent. The low-temperature halogen-free solder paste, its preparation method, and its application provided by this invention improve the compatibility between carbon nanotubes and the alloy, producing excellent results. It not only effectively improves the toughness and solderability of the solder paste but also significantly reduces the void ratio in the solder joints and prevents oxidation of the solder paste during storage and use, maintaining its performance stability.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, and particularly relates to a low-temperature halogen-free tin solder paste, its preparation method, and its application. Background Technology

[0002] With the development of electronic information products towards ultra-large-scale integration and miniaturization, solder paste has become the most important process material in surface mount technology (SMT). Traditional solder paste generally uses SAC series alloys (tin-silver-copper series alloys) as soldering materials, and the soldering temperature usually needs to be higher than 240℃. In the soldering process of highly integrated microelectronic devices, it is easy to cause problems such as device deformation. Therefore, solder pastes with tin-bismuth series alloys as low-temperature solders are now more commonly used.

[0003] Because this type of solder paste contains a large amount of bismuth metal, the solder joints have low toughness, which in turn prevents electronic devices from meeting performance requirements. Carbon nanotubes, due to their excellent mechanical, electrical, and thermal properties, are being developed as an excellent reinforcing phase for traditional solder pastes. However, the nanosize effect and fiber entanglement of carbon nanotubes make them difficult to disperse in solder paste, and their poor compatibility with other components prevents them from fully exerting their reinforcing effect in solder pastes.

[0004] Patent CN111151909A discloses a carbon nanotube-modified low-temperature solder and its preparation method. This low-temperature solder comprises nickel-plated carbon nanotubes, hydroxyl-containing multi-walled carbon nanotubes, and tin-bismuth alloys. Through the synergistic combination of hydroxyl-containing multi-walled carbon nanotubes and nickel-plated carbon nanotubes, the compatibility between the carbon nanotubes and the alloys is improved, resulting in excellent effects. It can effectively improve the toughness and weldability of the solder, playing a reinforcing role. Although this patent enhances the compatibility with tin alloys, enabling the carbon nanotubes to achieve a reinforcing and toughening effect, the process is relatively complex, costly, and the product quality is unstable. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a low-temperature halogen-free solder paste, its preparation method and application, which improves the compatibility between carbon nanotubes and alloys, producing excellent results. It can not only effectively improve the toughness and solderability of solder paste, but also significantly reduce the void ratio in the solder joint, and prevent the solder paste from oxidizing during storage and use, thus maintaining its stable performance.

[0006] The present invention proposes a low-temperature halogen-free solder paste, comprising: tin-bismuth alloy, carbon nanotubes and flux;

[0007] The flux comprises, by weight percentage: 30-50% film-forming resin, 5-15% rosin-based surfactant, 3-10% activator, 2-8% thixotropic agent, and the balance being solvent.

[0008] Preferably, the film-forming resin is at least one of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin, or terpene resin.

[0009] Preferably, the rosin-based chelating agent is obtained by an addition reaction of rosin with 3-allyl-5,5-dimethylhydantoin.

[0010] Preferably, the rosin-based surfactant is obtained by amide condensation reaction of dehydroabsic acid acylation with 3-dimethylaminopropylamine, followed by nucleophilic substitution reaction with 3-chloropropionic acid.

[0011] In this invention, the structural formula of the rosin-based surfactant is as follows:

[0012]

[0013] In this invention, the anionic groups contained in the rosin-based surfactant can coordinate with the tin-bismuth alloy, and the cationic groups adsorb carbon nanotubes. Therefore, it can effectively promote the compatibility between carbon nanotubes and tin-bismuth alloy, greatly improve the dispersibility of carbon nanotubes in solder paste, solve the problem of poor reinforcement effect of carbon nanotubes in the prior art, and improve the strength and toughness of the solder joint during soldering.

[0014] Preferably, the activator is at least one selected from succinic acid, glutaric acid, adipic acid, azelaic acid, itaconic acid, salicylic acid, or malic acid.

[0015] Preferably, the thixotropic agent is at least one of hydrogenated castor oil, aromatic polyamide, organobentonite, polyethylene wax, ethylene bis-stearamide, ethylene bis-lauramide, or polyamide wax thixotropic agent; the solvent is at least one of ethylene glycol phenyl ether, tetraethylene glycol methyl ether, dipropylene glycol, polyethylene glycol 200, 2-ethyl-1,3-hexanediol, diethylene glycol hexyl ether, diethylene glycol dibutyl ether, or tripropylene glycol butyl ether.

[0016] In this invention, the synergistic effect of activators and thixotropic agents makes the solder paste finer, improves its wettability, and reduces soldering defects and the number of solder balls. In addition, the solder paste provided by this invention does not contain halogens or lead, is environmentally friendly and safe, and has less solder joint corrosion.

[0017] In this invention, the solder paste further includes: 1-5% rosin-based chelating agent;

[0018] The rosin-based chelating agent is obtained by reacting rosin with 3-allyl-5,5-dimethylhydantoin via a DA addition reaction.

[0019] In this invention, the rosin includes L-piperidine, therefore the representative structural formula of the rosin-based chelating agent is shown below:

[0020]

[0021] In the aforementioned rosin-based chelating agent, on the one hand, the carboxyl group it contains can promote the removal of oxides and reduce the use of acidic surfactants, achieving good wettability and solderability even without halogen surfactants; on the other hand, the dimethylhydantoin it contains has excellent chelating ability, which can chelate the metal elements on the surface of tin-bismuth alloys, reduce the surface tension of tin-bismuth alloys, promote the fusion between solder powders, reduce the solder void rate, and the presence of rosin groups can also improve the dispersibility of tin-bismuth alloy tubes in solder paste and enhance the storage stability of solder paste.

[0022] Preferably, the tin-bismuth alloy is Sn42Bi58, Sn64.5Bi35Cu0.5, Sn64.6Bi35Ag0.4, Sn42Bi57Ag1, or Sn42Bi57.6Ag0.4; and the carbon nanotube is hydroxylated multi-walled carbon nanotube or carboxylated multi-walled carbon nanotube.

[0023] Preferably, the tin-bismuth alloy accounts for 85-90 wt% of the solder paste, the flux accounts for 9-14 wt% of the solder paste, and the carbon nanotubes account for 0.05-1 wt% of the solder paste.

[0024] This invention proposes a method for preparing the above-mentioned low-temperature halogen-free solder paste, comprising the following steps:

[0025] The solvent is heated to 150-160℃, then film-forming resin is added and stirred to melt. Rosin-based surfactant and thixotropic agent are then added and stirred to melt. The temperature is lowered to 120-130℃, then activator is added and stirred to melt. After cooling, flux is obtained.

[0026] The tin-bismuth alloy, carbon nanotubes, and flux are first stirred in a vacuum mixer for 5-10 minutes, then stirred under nitrogen for 25-35 minutes, and finally stirred under vacuum for 5-10 minutes to obtain the low-temperature halogen-free tin solder paste.

[0027] The present invention also proposes an application of the above-mentioned low-temperature halogen-free solder paste in the packaging of electronic components.

[0028] Compared to existing technologies, the key to this invention lies in using a specific rosin-based surfactant compound as a flux, combined with specific solvents, film-forming resins, activators, thixotropic agents, and rosin-based chelating agents. The resulting solder paste not only exhibits low-temperature performance, making it suitable for applications requiring low-temperature soldering and solving the problem of limited application of medium- and high-temperature solder paste, but also significantly reduces the void ratio in solder joints. This low void ratio directly improves the mechanical strength and electrical stability of the solder joints, thereby providing higher connection reliability. The addition of carbon nanotubes as an additive not only enhances the mechanical strength of the solder joints but also optimizes thermal and electrical conductivity. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the residue after soldering with the low-temperature halogen-free solder paste described in the embodiment of the present invention. Detailed Implementation

[0030] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0031] In the following examples, the CAS number for hydrogenated rosin is 65997-06-0; the CAS number for disproportionated rosin is 8050-09-7; the CAS number for polymerized rosin is 65997-05-9; the CAS number for hydrogenated castor oil is 8001-78-3; the CAS number for aromatic polyamide is 5892-11-5; the CAS number for ethylene bis-stearamide is 110-30-5; the CAS number for diethylene glycol hexyl ether is 112-59-4; the CAS number for tetraethylene glycol methyl ether is 23783-42-8; the CAS number for diethylene glycol butyl ether is 203-961-6; and the CAS number for triethylene glycol butyl ether is 143-22-6.

[0032] Example 1

[0033] This invention proposes a low-temperature halogen-free solder paste, comprising by weight percentage: 86wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm), and 13.9wt% flux.

[0034] The flux paste comprises, by weight percentage: 30% hydrogenated rosin, 10% polymerized rosin, 10% rosin-based surfactant, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bis-stearamide, and the balance being triethylene glycol butyl ether.

[0035] The aforementioned rosin-based surfactant was synthesized by the following method: Dehydroabietic acid was dissolved in dichloromethane, and 40% (by weight) of oxaloyl chloride (by mass of dehydroabietic acid) was added. The mixture was heated to 35°C and stirred for 5 hours. The mixture was then distilled under reduced pressure to obtain dehydroabietic chloride. 80% (by weight of dehydroabietic acid) of 3-dimethylaminopropylamine and 1.2 times (by weight of dehydroabietic acid) of triethylamine were dissolved in dichloromethane. The dichloromethane solution containing the aforementioned dehydroabietic chloride was slowly added dropwise at 0°C. After the addition was complete, the reaction was continued at room temperature for 5 hours. Finally, the reaction was terminated with hydroxide solution at pH 12. The organic phase was washed five times with sodium sulfate solution, collected, and dried with anhydrous sodium sulfate. After standing, the anhydrous sodium sulfate was removed by filtration, and the residual solvent was removed by vacuum distillation. The product was then purified by silica gel column chromatography (the volume ratio of methanol to ethyl acetate as eluent was 2:1) to obtain dehydroabiamide. Dehydroabiamide and 3-chloropropionic acid were dissolved in ethanol and stirred at 90°C for 24 hours. After the reaction was completed, the residual solvent was removed by vacuum distillation, and the product was recrystallized three times with a mixture of ethanol and acetone to obtain the rosin-based surfactant. 1 H NMR (400MHz, CDCl3): δ7.03(m,2H),6.89(d,1H),6.93(s,1H),3.61(m,2H),3.36(s,6H),3.2 4-3.18(m,4H),2.90-2.78(m,5H),2.36-2.25(m,5H),1.85-1.35(m,12H),1.33-1.21(m,6H).

[0036] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0037] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt. Then, rosin-based surfactant, hydrogenated castor oil and ethylene bis-stearamide are added and stirred to melt. After cooling to 125°C, succinic acid and adipic acid are added and stirred to melt. After cooling, flux is obtained.

[0038] Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above flux were stirred in a vacuum mixer for 8 minutes, then stirred under nitrogen for 30 minutes, and then stirred under vacuum for 6 minutes to obtain the low-temperature halogen-free tin solder paste.

[0039] Example 2

[0040] This invention proposes a low-temperature halogen-free solder paste, comprising by weight percentage: 85wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.05wt% carboxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 14.95wt% flux.

[0041] The flux paste comprises, by weight percentage: 20% hydrogenated rosin, 10% disproportionated rosin, 5% rosin-based surfactant, 3% succinic acid, 4% glutaric acid, 3% adipic acid, 1% hydrogenated castor oil, 1% aromatic polyamide, and the balance being diethylene glycol hexyl ether.

[0042] The above-mentioned rosin-based surfactant was synthesized by the method described in Example 1.

[0043] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0044] Diethylene glycol hexyl ether was heated to 150°C, and then hydrogenated rosin and disproportionated rosin were added and stirred to melt. Rosin-based surfactant, hydrogenated castor oil and aromatic polyamide were then added and stirred to melt. After cooling to 120°C, succinic acid, glutaric acid and adipic acid were added and stirred to melt. After cooling, flux was obtained.

[0045] Sn42Bi58 alloy powder, carboxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 5 minutes, then stirred under nitrogen for 35 minutes, and then stirred under vacuum for 5 minutes to obtain the low-temperature halogen-free tin solder paste.

[0046] Example 3

[0047] This invention proposes a low-temperature halogen-free solder paste, which comprises, by weight percentage: 90wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.5wt% hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm) and 9.5wt% flux.

[0048] The flux, by weight percentage, comprises: 25% hydrogenated rosin, 25% polymerized rosin, 15% rosin-based surfactant, 1% succinic acid, 2% adipic acid, 4% hydrogenated castor oil, 4% ethylene bis-stearamide, and the balance being tetraethylene glycol methyl ether and diethylene glycol butyl ether.

[0049] The above-mentioned rosin-based surfactant was synthesized by the method described in Example 1.

[0050] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0051] After heating tetraethylene glycol methyl ether and diethylene glycol butyl ether to 160°C, hydrogenated rosin and polymerized rosin are added and stirred to melt. Then, rosin-based surfactant, hydrogenated castor oil and ethylene bis-stearamide are added and stirred to melt. After cooling to 130°C, succinic acid and adipic acid are added and stirred to melt. After cooling, flux is obtained.

[0052] Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above-mentioned flux were stirred in a vacuum mixer for 10 minutes, then stirred under nitrogen for 20 minutes, and then stirred under vacuum for 10 minutes to obtain the low-temperature halogen-free tin solder paste.

[0053] Example 4

[0054] This invention proposes a low-temperature halogen-free solder paste, comprising by weight percentage: 86wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm), and 13.9wt% flux.

[0055] The flux paste comprises, by weight percentage: 30% hydrogenated rosin, 10% polymerized rosin, 10% rosin-based surfactant, 3% rosin-based chelating agent, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bis-stearamide, and the balance being triethylene glycol butyl ether.

[0056] The above-mentioned rosin-based surfactant was synthesized by the method described in Example 1; the rosin-based chelating agent was synthesized by the following method: rosin (acid value 180 mg KOH / g) was heated to 230°C, and then 3% hydroquinone and 20% 3-allyl-5,5-dimethylhydantoin by weight of rosin were added. The reaction was carried out under nitrogen protection for 4 hours, and then the mixture was cooled and discharged to obtain the rosin-based chelating agent.

[0057] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0058] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt. Then, rosin-based surfactant, rosin-based chelating agent, hydrogenated castor oil and ethylene bis-stearamide are added and stirred to melt. After cooling to 125°C, succinic acid and adipic acid are added and stirred to melt. After cooling, flux is obtained.

[0059] Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above flux were stirred in a vacuum mixer for 8 minutes, then stirred under nitrogen for 30 minutes, and then stirred under vacuum for 6 minutes to obtain the low-temperature halogen-free tin solder paste.

[0060] Comparative Example 1

[0061] This invention proposes a low-temperature halogen-free solder paste, comprising by weight percentage: 86wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm), and 13.9wt% flux.

[0062] The flux, by weight percentage, comprises: 30% hydrogenated rosin, 10% polymerized rosin, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bis-stearamide, and the balance being triethylene glycol butyl ether.

[0063] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0064] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt. Then, hydrogenated castor oil and ethylene bis-stearamide are added and stirred to melt. After cooling to 125°C, succinic acid and adipic acid are added and stirred to melt. After cooling, flux is obtained.

[0065] Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above flux were stirred in a vacuum mixer for 8 minutes, then stirred under nitrogen for 30 minutes, and then stirred under vacuum for 6 minutes to obtain the low-temperature halogen-free tin solder paste.

[0066] Comparative Example 2

[0067] This invention proposes a low-temperature halogen-free solder paste, comprising by weight percentage: 86wt% Sn42Bi58 alloy powder (average particle size of 40μm), 0.1wt% hydroxylated multi-walled carbon nanotubes (outer diameter of 8-15nm, length of 0.5-2μm), and 13.9wt% flux.

[0068] The flux, by weight percentage, comprises: 30% hydrogenated rosin, 10% polymerized rosin, 10% betaine, 2% succinic acid, 5% adipic acid, 3% hydrogenated castor oil, 2% ethylene bis-stearamide, and the balance being triethylene glycol butyl ether.

[0069] The preparation method of the above-mentioned low-temperature halogen-free solder paste includes the following steps:

[0070] After heating triethylene glycol butyl ether to 155°C, hydrogenated rosin and polymerized rosin are added and stirred to melt. Then, betaine, hydrogenated castor oil and ethylene bis-stearamide are added and stirred to melt. After cooling to 125°C, succinic acid and adipic acid are added and stirred to melt. After cooling, flux is obtained.

[0071] Sn42Bi58 alloy powder, hydroxylated multi-walled carbon nanotubes and the above flux were stirred in a vacuum mixer for 8 minutes, then stirred under nitrogen for 30 minutes, and then stirred under vacuum for 6 minutes to obtain the low-temperature halogen-free tin solder paste.

[0072] The solder paste was applied according to relevant standards, and the tensile strength of the solder joints was tested. The post-soldering void rate was detected using X-ray equipment, and the testing was conducted using standard operating methods. The test results are shown in Table 1.

[0073] Tensile strength: Tested according to GB 2651-1989 standard;

[0074] Drop test: The drop test was conducted according to the standard JESD22-B111, using the Daisy Chain BGA soldered test link, and the test was conducted under a drop condition of 1500G.

[0075] Storage stability: Place the above solder paste in a sealed container and place it at 25°C and 60% humidity, and observe its appearance changes over 8 months;

[0076] Table 1. Performance test results of the low-temperature halogen-free solder paste described in the examples and comparative examples.

[0077]

[0078]

[0079] As can be seen from the results in Table 1, the low-temperature halogen-free solder paste provided by the present invention effectively improves the strength and toughness of the solder joints. Compared with the finished solder paste of the same specifications in the prior art, the void rate after soldering is significantly reduced. Furthermore, it is environmentally friendly and non-toxic, and can be adapted to the field of electronic packaging.

[0080] Figure 1 This is a schematic diagram of the residue after welding. As can be seen from the diagram, the area around the weld point is very clean, with no black residue at all.

[0081] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-temperature halogen-free solder paste, characterized in that, include: Tin-bismuth alloy, carbon nanotubes, and flux; The flux comprises, by weight percentage: 30-50% film-forming resin, 5-15% rosin-based surfactant, 3-10% activator, 2-8% thixotropic agent, and the balance being solvent; The tin-bismuth alloy is Sn42Bi58, Sn64.5Bi35Cu0.5, Sn64.6Bi35Ag0.4, Sn42Bi57Ag1, or Sn42Bi57.6Ag0.4; the carbon nanotubes are hydroxylated multi-walled carbon nanotubes or carboxylated multi-walled carbon nanotubes. The rosin-based surfactant is obtained by amide condensation reaction of dehydroabsic acid acylation followed by reaction with 3-dimethylaminopropylamine, and then nucleophilic substitution reaction with 3-chloropropionic acid. The tin-bismuth alloy accounts for 85-90 wt% of the solder paste, the flux accounts for 9-14 wt% of the solder paste, and the carbon nanotubes account for 0.05-1 wt% of the solder paste.

2. The low-temperature halogen-free solder paste according to claim 1, characterized in that, The film-forming resin is at least one of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin, or terpene resin.

3. The low-temperature halogen-free solder paste according to claim 1 or 2, characterized in that, The active agent is at least one of succinic acid, glutaric acid, adipic acid, azelaic acid, itaconic acid, salicylic acid, or malic acid.

4. The low-temperature halogen-free solder paste according to claim 1 or 2, characterized in that, The thixotropic agent is at least one of hydrogenated castor oil, aromatic polyamide, organobentonite, polyethylene wax, ethylene bis-stearamide, ethylene bis-lauramide, or polyamide wax thixotropic agent; the solvent is at least one of ethylene glycol phenyl ether, tetraethylene glycol methyl ether, dipropylene glycol, polyethylene glycol 200, 2-ethyl-1,3-hexanediol, diethylene glycol hexyl ether, diethylene glycol dibutyl ether, or tripropylene glycol butyl ether.

5. The low-temperature halogen-free solder paste according to claim 1 or 2, characterized in that, The flux also includes: 1-5% rosin-based chelating agent; The rosin-based chelating agent is obtained by reacting rosin with 3-allyl-5,5-dimethylhydantoin via a DA addition reaction.

6. A method for preparing the low-temperature halogen-free solder paste according to any one of claims 1-4, characterized in that, Includes the following steps: The solvent is heated to 150-160℃, then film-forming resin is added and stirred to melt. Rosin-based surfactant and thixotropic agent are then added and stirred to melt. The temperature is lowered to 120-130℃, then activator is added and stirred to melt. After cooling, flux is obtained. The tin-bismuth alloy, carbon nanotubes, and flux are first stirred in a vacuum mixer for 5-10 minutes, then stirred under nitrogen for 25-35 minutes, and finally stirred under vacuum for 5-10 minutes to obtain the low-temperature halogen-free tin solder paste.

7. A method for preparing the low-temperature halogen-free solder paste according to claim 5, characterized in that, Includes the following steps: The solvent is heated to 150-160℃, then film-forming resin is added and stirred to melt. Rosin-based surfactant, rosin-based chelating agent and thixotropic agent are then added and stirred to melt. The temperature is lowered to 120-130℃, then activator is added and stirred to melt. After cooling, flux is obtained. The tin-bismuth alloy, carbon nanotubes, and flux are first stirred in a vacuum mixer for 5-10 minutes, then stirred under nitrogen for 25-35 minutes, and finally stirred under vacuum for 5-10 minutes to obtain the low-temperature halogen-free tin solder paste.

8. The application of the low-temperature halogen-free solder paste according to any one of claims 1-5 in the packaging of electronic components.

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