阅读说明：本技术 一种锡基焊料熔体精炼用熔剂及其精炼方法 (Flux for refining tin-based solder melt and refining method thereof ) 是由 张家涛 唐芸生 梁华鑫 贾元伟 卢红波 储鑫 余琨 普友福 刘庆富 于 2020-08-19 设计创作，主要内容包括：本发明公开了一种锡基焊料熔体精炼用熔剂,其包括基础油、松香；该熔剂在锡基合金焊料熔炼合金化时使用,该熔剂能起到很好的防止氧化、去除杂质和氧化渣、熔体除气等作用,实现熔体的精炼；在锡基合金焊料熔炼过程中,添加本发明配置的油基熔剂并采用相应的合金熔体精炼方法,可以有效提高锡基焊料的熔体质量,改善锡基焊料在后续波峰焊接时生成的氧化渣形态；该油基溶剂价格便宜,可以批量制备,精炼效果明显,不增加原有锡基焊料生产的工序,成本低,效果好,特别适合在现有锡基焊料生产工艺上作为辅助工艺开展应用,进行生产。(The invention discloses a flux for refining a tin-based solder melt, which comprises base oil and rosin; the flux is used when the tin-based alloy solder is smelted and alloyed, and can play a good role in preventing oxidation, removing impurities and oxidation slag, degassing a melt and the like, so that the refining of the melt is realized; in the process of smelting the tin-based alloy solder, the oil-based flux prepared by the invention is added and a corresponding alloy melt refining method is adopted, so that the melt quality of the tin-based solder can be effectively improved, and the form of oxidation slag generated by the tin-based solder in the subsequent wave soldering is improved; the oil-based solvent is low in price, can be prepared in batches, has an obvious refining effect, does not increase the production process of the original tin-based solder, is low in cost and good in effect, and is particularly suitable for being used as an auxiliary process on the existing tin-based solder production process to be developed and applied to production.)

1. A flux for refining a tin-based solder melt, characterized in that: comprises base oil and rosin.

2. A flux for melt refining of a tin-based solder according to claim 1, characterized in that: the addition amount of the rosin is 1 to 20 percent of the weight of the base oil in percentage by weight.

3. A flux for melt refining of a tin-based solder according to claim 1 or 2, characterized in that: also comprises stearic acid or sodium stearate, and the addition amount of the stearic acid or sodium stearate is 1 to 10 percent of the weight of the base oil.

4. A flux for melt refining of a tin-based solder according to claim 3, characterized in that: the base oil is one or more of corn oil, peanut oil and tea oil.

5. A refining method using the flux for melt refining of tin-based solder according to any one of claims 1 to 4, characterized by comprising the steps of:

(1) adding rosin into base oil, fully stirring to dissolve the rosin, then adding stearic acid or sodium stearate, fully stirring to dissolve the stearic acid or sodium stearate to obtain an oil-based flux, and storing the oil-based flux in a closed container for later use;

(2) melting tin-based solder into a liquid phase at 300-400 ℃, adjusting the liquid phase temperature of the solder through the furnace temperature, and adding an oil-based flux accounting for 0.01-1% of the mass of the tin-based solder when the liquid phase temperature of the solder is adjusted to 350 +/-20 ℃ for two times;

(3) evenly dividing the oil-based flux into two parts, adding one part of the oil-based flux, stirring for 20-30 min, and scooping out the oil-based flux by using a steel spoon when black slag is seen on the surface of the solder melt to be sticky and pasty in the stirring process; after stirring, scooping out slag on the surface of the solder melt and the residual oil-based flux together by using a steel spoon; raising the temperature of the solder melt to 370 +/-20 ℃, adding the remaining half of the oil-based flux into the solder melt, stirring for 20-30 min, and scooping out the solder melt by using a steel spoon if slag exists on the surface of the solder melt in the stirring process; and (3) keeping the temperature of the stirred solder melt at 370 +/-20 ℃ for 10-30 min, and casting after the refining process is finished.

6. Refining process according to claim 5, characterized in that: the tin-based solder is a tin-silver-copper series, a tin-copper series or a tin-zinc series lead-free solder alloy.

Technical Field

The invention relates to an oil-based flux for refining a melt used in smelting a tin-based alloy solder and a refining method for refining the tin-based alloy melt by using the oil-based flux, belonging to the field of material preparation and forming.

Background

Because the requirements for environmental protection and life health are increasingly improved, the lead-free solder becomes a common welding material in the field of electronic packaging at present and is used for replacing the lead-containing solder; typical tin-based lead-free solders comprise Sn-Zn, Sn-Cu, Sn-Ag-Cu and the like, and the tin alloy solders have advantages and disadvantages, and in the actual use process, defects often exist, so that the welding effect cannot fully meet the use requirements. Therefore, research and development work on these tin-based solders has been continuously conducted.

At present, researches on lead-free solders such as Sn-Zn, Sn-Cu, Sn-Ag-Cu, etc. focus on the design of solder components and the adjustment of alloy elements, such as research paper "application of tin-copper lead-free solder in circuit board assembly" (electronics and packaging, 2012, 10: 7) and patent CN200410066350.4, and improvement of the wettability of solder by adding Ni, Ge, Sb, rare earth, etc. to tin-based solder; some process technologies focus on the application and development of flux for solder to improve the soldering performance, such as CN 201711361459.4; there are also some research efforts focusing on the solution of problems occurring in the practical application of tin-based solders, such as the article "common adverse conditions and improvement measures for wave soldering" (electronic technology, 2019, 3: 120).

When the tin-based solder is subjected to wave soldering, the solder can be re-melted into a liquid phase, the soldering process is limited by environmental use conditions, metal oxide slag can be generated in the solder melt, and the form and the characteristics of the oxide slag directly influence the technological process and the soldering quality of the wave soldering. In order to improve the wave soldering effect of tin-based solder, current research mainly focuses on improvement of equipment and process during wave soldering, such as treatises on influence of position of a tin furnace bladder of the wave soldering on the amount of tin-based solder oxidized slag (metal materials and metallurgical engineering, 2014, 5: 18) and on an improvement method for generating tin balls and tin slag through selective wave soldering (development and innovation, 2019, 5: 236). Few research works trace back to the important smelting process in the preparation process of the tin-based solder alloy, and when the tin-based solder is completely melted into a liquid phase in the smelting production process, the tin-based solder is kept at a high temperature for a period of time to realize the alloying process. Therefore, defects such as oxidation and inclusion generated during the melting process remain in the tin-based solder until the final application stage appears, resulting in defects of the solder.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a flux for refining a tin-based solder melt, which is used for refining a tin-based solder melt for typical series of solders such as Sn-Zn, Sn-Cu, Sn-Ag-Cu and the like in the tin-based solder, and when the solder is molten, the flux for refining the tin-based solder melt is added to purify the tin-based alloy melt so as to obtain a high-quality tin-based solder cast ingot.

The flux for refining the tin-based solder melt comprises base oil and rosin; according to the weight percentage, the base oil is used as the basis, and the addition amount of the rosin is 1-20% of the weight of the base oil.

The flux for refining the tin-based solder melt also comprises stearic acid or sodium stearate, and the addition amount of the stearic acid or sodium stearate is 1-10% of the weight of the base oil.

The base oil is one or more of corn oil, peanut oil and tea oil.

The flux for refining the tin-based solder melt is an oil-based flux used in the process of smelting and alloying the tin-based alloy solder, and plays roles in well preventing oxidation, removing impurities and oxidation slag, degassing the melt and the like, thereby realizing the refining of the melt; in the process of smelting the tin-based alloy solder, the oil-based flux is added and a corresponding alloy melt refining method is adopted, so that the melt quality of the tin-based solder can be effectively improved, and the form of oxidation slag generated by the tin-based solder in the subsequent wave soldering is improved; the oil-based solvent is low in price, can be prepared in batches, has an obvious refining effect, does not increase the production process of the original tin-based solder, is low in cost and good in effect, and is particularly suitable for being used as an auxiliary process on the existing tin-based solder production process to be developed and applied to production.

The use method of the flux for refining the tin-based solder melt comprises the following steps:

(1) adding rosin into base oil, fully stirring to dissolve the rosin, then adding stearic acid or sodium stearate, fully stirring to dissolve the stearic acid or sodium stearate to obtain an oil-based flux, and storing the oil-based flux in a closed container for later use;

the above substances can be added into the base oil separately or simultaneously; (2) melting tin-based solder into a liquid phase at 300-400 ℃, adjusting the liquid phase temperature of the solder through the furnace temperature, and adding an oil-based flux accounting for 0.01-1% of the mass of the tin-based solder when the liquid phase temperature of the solder is adjusted to 350 +/-20 ℃ for two times;

(3) evenly dividing the oil-based flux into two parts, adding one part of the oil-based flux, stirring for 20-30 min, and scooping out the oil-based flux by using a steel spoon when black slag is seen on the surface of the solder melt to be sticky and pasty in the stirring process; after stirring, scooping out slag on the surface of the solder melt and the residual oil-based flux together by using a steel spoon; raising the temperature of the solder melt to 370 +/-20 ℃, adding the remaining half of the oil-based flux into the solder melt, stirring for 20-30 min, and scooping out the solder melt by using a steel spoon if slag exists on the surface of the solder melt in the stirring process; and (3) keeping the temperature of the stirred solder melt at 370 +/-20 ℃ for 10-30 min, and casting after the refining process is finished.

The tin-based solder includes common lead-free solder alloys of tin-silver-copper (Sn-Ag-Cu) series, tin-copper (Sn-Cu) series, and tin-zinc (Sn-Zn) series.

The invention has the following advantages and technical effects:

1. the oil-based flux for refining is simple in configuration mode, the used raw materials are low in price and easy to obtain, and the purity of the conventional edible-grade vegetable oil completely meets the use requirement; the additives in the oil base have no chemical toxicity and can be purchased without limitation;

2. the refining deslagging effect of the oil-based flux is obvious, and a large amount of slag and the flux float on the surface of the melt together in the stirring process of adding the solder alloy melt, so that the oil-based flux can be ladled out by a steel ladle conveniently;

3. the oil-based flux has good anti-oxidation effect, the flux always floats on the surface of the solder alloy melt in the refining and stirring process, so that the oxidation of the solder melt is prevented, and the oil-based flux simultaneously has the effects of preventing the oxidation and refining the melt;

4. the oil-based flux is less in use amount, which accounts for less than 1% of the total amount of the solder, and gradually volatilizes at high temperature without residue in the refining and standing process; the volatilization process of the vegetable oil does not generate gas substances which have serious toxicity to human bodies and is far lower than the hexachloroethane C used in the industry at present₂Cl₆Or the poisoning effect of fluxes such as sodium hydroxide NaOH and the like;

5. the refining process flow of the oil-based flux is short, the melt purification effect is good, the production cost is low, and the method is suitable for large-scale production.

Drawings

FIG. 1 is a schematic illustration of a solder melt surface transparent oil-based flux;

FIG. 2 is a schematic illustration of the formation of a black viscous slag from surface oil based fluxes and impurities in the melt after refining agitation;

FIG. 3 is a schematic illustration of the formation of brown slag from the flux and impurities in the melt after refining agitation;

FIG. 4 is a schematic diagram showing that after the flux is added and stirred for the second time, the amount of black slag is obviously reduced, and the alloy liquid around the slag is silvery white;

FIG. 5 is a schematic view showing that the flux has a good anti-oxidation protection effect, the flux on the surface of the melt is transparent, the surface of the melt is not oxidized, and the surface of the melt is a mirror surface;

FIG. 6 is a schematic view showing the formation of a brown, white oxide film on the surface of an alloy melt without flux.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. Modifications or substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit and scope of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art; all reagents used in the examples are commercially available unless otherwise specified.