Chemical composition and determination of soldering fluxes
Abstract
This paper introduces the chemical composition and determination method of soldering fluxes based on JB/T 7948-1999. Soldering fluxes play an important role in soldering operations, and the quality of soldering fluxes directly affects the welding quality. According to the relevant provisions of this standard, the chemical composition of soldering fluxes is mainly composed of activator, auxiliary surfactant, etc. It also introduces how to determine its pH value, flux content and residue content, so as to ensure the quality of soldering fluxes.
1 Introduction
Soldering is an important process of parts and components. It is an efficient method to form electrical and mechanical connections between parts and components. Soldering flux is used in the soldering process to remove various kinds of oxides on the surface of the workpiece. In addition, it also reduces the surface tension of the solder and promotes the wetting and wetting of the solder on the surface of the workpiece. In order to better ensure the quality of soldering, it is necessary to have a complete understanding of the chemical composition and determination of Soldering flux, so that it can meet the requirements of welding process.
2Chemical composition of soldering fluxes
Soldering fluxes are composed of a variety of chemical substances. According to the relevant provisions of JB/T 7948-1999, the chemical composition of soldering fluxes is mainly composed of activators, auxiliary surfactants, fillers, thickeners, preservatives and other auxiliary materials.
2.1 Activator
The activator is the main component of soldering fluxes, accounting for more than 80% of the total mass fraction of soldering fluxes. Commonly used activators are rosin, rosin derivatives, halogen-containing activators, amines and other organic substances, which have different chemical properties and different functions in soldering fluxes.
2.2 Auxiliary Surfactant
The auxiliary surfactant is added to the soldering flux for the purpose of improving the wetting and dissolution of the solder. The types of surfactants commonly used in soldering fluxes are long chain alcohols, glycerol, polyglycerol, glycol, mixtures of glycol, propylene glycol, surfactants and various organic amines.
2.3 Filler
The thickness agent is usually an inorganic powder or a mixture of organic and inorganic powders, which is used for the purpose of adjusting the viscosity and thixotropy of the flux and reducing the cost of the flux. Common fillers include inert powder, activated carbon powder, bentonite, calcium carbonate, talc, mica and other substances.
2.4 Thickener
Thickener is a kind of powder or resin material added to it, which is used to adjust the viscosity of the flux and make the flux a paste-like state. Common thickeners are resin, wax, cellulose and its derivatives.
2.5 Preservatives
Preservatives are used in soldering fluxes to maintain the shelf life and quality of them. Commonly used preservatives are organic benzene sulfonic acid, phenols and their derivatives.
3Determination of soldering fluxes
In order to better ensure the quality of soldering fluxes, they need to go through some tests. Common ones are pH value determination, flux content determination and residue content determination.
3.1 pH Value Determination
The pH value of soldering flux is an important indicator, which determines the basicity or acidity of the flux, and affects its ability to clean, wet, solder and microbial corrosion. Therefore, the pH value of soldering fluxes need to be tested regularly, the specific test is as follows:
(1) Weigh the test sample in a 100ml beaker.
(2) Gradually add 1ml of deionized water to the beaker, stir it evenly and measure its pH.
3.2 Flux Content Determination
Flux content is an important index to monitor the quality of soldering flux. The test method is to place a suitable amount of flux sample in a beaker together with 40ml of sodium hydroxide solution, stir evenly and dissolve, then filter out the residue after cooling, weigh it, and calculate the content.
3.3 Residue Content Determination
The residue content of the flux is related to its ability to clean the solder joint surface. High residue content will reduce the quality of the welding. Therefore, the determination method of the residue content is to take a certain amount of flux sample and dissolve it in 500ml of neutral detergent solution, filter out the residue, dry it and weigh it, calculate the residue content.
Conclusion
This paper introduces the chemical composition and determination method of soldering fluxes based on JB/T 7948-1999. The chemical composition of the flux is mainly composed of activators, auxiliary surfactants, fillers, thickeners and preservatives. In order to ensure the quality of soldering fluxes, the pH value, flux content and residue content need to be determined according to the relevant provisions. Through the above introduction, we have a certain understanding of the chemical composition and determination method of soldering fluxes, which can ensure the quality of soldering fluxes.
