What are the Characteristics of Water-Soluble Solder Paste_Solder Paste Cleaning

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The traditional solder flux is formulated with rosin orepoxy resin as the base material, mixing with an active agent, thixotropicagent, solvent, and other substances. At present, two major factions ofno-clean solder paste and water-soluble solder paste have been derived based onflux compositions. No-clean solder paste, as the name suggests, produces a tinyamount of residue after soldering and is unnecessary to clean. Althoughno-clean solder paste has less activity, it can still meet most consumerelectronics soldering needs. Currently, no-clean solder paste is adopted by themajority of companies because of its good stability and simple use process.However, some solders require higher flux activity, and the residue level isunacceptable, which needs to be removed by using cleaning agents.

Features of Water-Soluble Solder Paste

The water-soluble solder paste is still made by mixingalloy solder powder and flux but using water-soluble flux components.Water-soluble solder pastes are formulated with inorganic or organic fluxes.The inorganic formulation adopts inorganic acids or inorganic salts as matrixsubstances. Inorganic acids include hydrochloric acid, hydrofluoric acid, etc.For inorganic salts, zinc chloride and ammonium chloride are used. The residuegenerated after soldering is highly corrosive and needs to be removed withdeionized water in time. Organic formulations use lactic acid and citric acidas matrix substances. Similar to inorganic formulations, organic formulationsare acidic but less corrosive.

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Figure 1. Water-soluble solder paste.

Solder Paste Cleaning Process

There are many cleaning methods, such as water-based, alcohol-based,ether-based cleaning, etc. The water-soluble solder paste mentioned in thisarticle is a solder paste that uses deionized water for residue cleaning. Thecleaning agents used can also be divided into semi-water-based and water-basedcleaning. Currently, water-based cleaning is widely used. The circuit board iscleaned by soaking, spraying, ultrasonic, and other methods and then rinsedwith deionized water. Deionized water temperature is generally controlledbetween 25-60 ¡ãC. Finally, the PCBs are dry with hot air at 80¡ãC or drynaturally. It should be noted that natural drying takes a long time, which willreduce production efficiency. Manufacturers need to make research and judgmentsbased on actual needs.

Fitech can produce high-quality water-soluble solder paste with high soldering reliability. The solder jointsare bright and free from cleaning. Welcome to contact us for more information.