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Low-temperature lead-free solder paste and preparation method thereof

A lead-free solder paste, low temperature technology, applied in the direction of welding equipment, welding medium, manufacturing tools, etc., can solve the problems of solder wettability, poor tensile and shear performance, etc., to achieve improved drop resistance and thermal cycle life Enhanced effect

Active Publication Date: 2020-06-23
DONGGUAN YONGAN TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Medium-temperature alloys also include Sn69.5Bi30.0Cu0.5 alloy (solidus temperature 149°C, liquidus temperature 186°C) and Sn82.5Bi17.0Cu0.5 (solidus temperature 190°C, liquidus temperature 209°C) , the wettability, tensile and shear properties of the above solders are poor
[0007] However, SnBiAgCu quaternary alloys, in which the bismuth content is between 17-58%, have not yet been reported.

Method used

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  • Low-temperature lead-free solder paste and preparation method thereof
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  • Low-temperature lead-free solder paste and preparation method thereof

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preparation example Construction

[0043] The present invention also discloses a preparation method of low-temperature lead-free solder paste, comprising the following steps:

[0044] (1) Weigh rosin, thixotropic agent, active agent and solvent in proportion.

[0045] (2) Add solvent into the container, heat up to 150-160°C, add rosin and stir until completely melted, then add thixotropic agent and stir until completely melted.

[0046] (3) Cool down the above system to 120-130°C, then add active agent, stir until completely melted, cool to get paste flux, put it in 0-10°C freezer for future use.

[0047] (4) Weigh low-temperature tin-bismuth-silver-copper quaternary lead-free solder powder and flux in proportion, pour them into a vacuum mixer, stir initially at low speed for 5-10 minutes, then fill with nitrogen and stir at medium speed for 25-35 minutes, so that Thoroughly mix tin powder and flux, and then vacuumize and stir at medium speed for 5 to 7 minutes to prepare solder paste.

Embodiment 1

[0050] A. Prepare a flux with the following ratio:

[0051]

[0052] The preparation method is as follows:

[0053] Weigh 23% by mass of polymerized rosin, 24% by mass of hydrogenated rosin, 4% by mass of modified hydrogenated castor oil, 3% by mass of ethylene bis stearic acid amide , 36.2% by mass of diethylene glycol hexyl ether and 3% by mass of succinic acid, 3% by mass of adipic acid, 0.3% by mass of diphenylguanidine hydrobromide Salt, 3.5% by mass of benzotriazole; add solvent to stainless steel container and heat to 160°C, add rosin and stir until completely melted, keep this temperature and add thixotropic agent and stir until completely melted; cool down to 130°C ℃, 3% by mass of succinic acid, 3% by mass of adipic acid and 0.3% by mass of diphenylguanidine hydrobromide are added to the container, and stirred until completely melted, Finally, 3.5% by mass of benzotriazole was added and stirred to melt. After cooling, the flux is obtained, and stored in a 7°C f...

Embodiment 2

[0061] Prepare a solder paste with the following ratio:

[0062]

[0063] The preparation method is as follows:

[0064] 87.5% by mass of Sn49.6Bi48.5Ag1.0Cu0.9 solder powder was poured into a vacuum mixer filled with nitrogen and stirred at a low speed for 5 minutes.

[0065] Then weigh 12.5% ​​by mass of flux in proportion, add it to the above mixed solder powder, stir in a vacuum mixer at low speed for 5 minutes, then fill with nitrogen and stir at medium speed for 30 minutes, so that the tin powder and flux are fully mixed Evenly, then evacuate and stir at medium speed for 5 minutes to prepare solder paste.

[0066] This solder paste is applied to remote control PCB board soldering, placed in an air reflow oven with a peak temperature of 175°C, no damage to the LED lamp, and full tin on the plug-in position, all tests meet the customer's process control requirements.

[0067] Classification of existing soldering processes and maximum reflow temperatures in the electro...

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Abstract

The invention discloses a low-temperature lead-free solder paste and a preparation method thereof. The low-temperature lead-free solder paste is prepared from the following raw materials according tomass percent: 86% to 91% of low-temperature tin-bismuth-silver-copper quaternary lead-free solder powder and 9% to 14% of scaling powder, wherein the low-temperature tin-bismuth-silver-copper quaternary lead-free solder powder is composed of four elements including tin, bismuth, silver and copper, the mass percent of bismuth is 46% to 52%, the mass percent of copper is 0.3% to 1.2% of copper, themass percent of silver is 0.4% to 1.2%, and the mass percent of tin is 45.6% to 53.3%. The solder paste is prepared by adopting the formula and the method, the bismuth content is in a relatively highreasonable range, so that the solidus temperature of the product is increased from 138 DEG C to 151 DEG C, the solder paste is suitable for a low-temperature packaging process, the welding peak temperature does not exceed 200 DEG C, and compared with Sn42Bi58 alloy, the tensile strength, the shear strength, the anti-dropping performance and the thermal cycle life of the product are greatly increased.

Description

technical field [0001] The invention relates to the technology in the field of solder, in particular to a low-temperature lead-free solder paste and a preparation method thereof. Background technique [0002] In the field of tin-based solder, we can provide soldering under low temperature conditions and have many years of practical experience, mainly Sn42Bi58 alloy with a eutectic point of 138 ° C, which is used in the welding end of components. The coating is lead-free; the lead coating is due to SnPbBi There is a eutectic point of 96°C in the elemental alloy, which limits its application. Sn42Bi58 alloy will segregate hard and brittle Bi during solidification, which has poor mechanical drop impact resistance and low thermal conductivity. [0003] The foreign Indium company introduced the Sn42Bi57Ag1.0 alloy in terms of improving the mechanical properties of the Sn42Bi58 alloy, and its liquidus temperature was slightly increased to 140 °C. Domestic use of Sn42Bi57.6Ag0.4 ...

Claims

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Application Information

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IPC IPC(8): B23K35/26B23K35/40
CPCB23K35/262B23K35/264B23K35/40
Inventor 吴国齐连亨池李奕林刘明莲
Owner DONGGUAN YONGAN TECH
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