Welding materials are very important raw materials for processing in PCBA processing. The quality and selection of welding materials will directly affect the quality of SMT chip processing and the welding of plug-ins. This is reflected in the welding quality of PCBA and has become the most direct quality inspection. point.
The welding material is generally called solder, which is used to fuse two or more metal surfaces during the welding process, so that they become a whole metal or alloy.
The solder in PCBA processing can be divided into tin-lead solder, silver solder and copper solder according to the different components. Tin-lead solder is the most commonly used in actual processing and production. Here are some commonly used solders, solder pastes, and fluxes.
One, commonly used solder
1. Tubular solder wire
The tubular solder wire is made of flux and solder together into a tubular shape, and solid flux is entrained in the solder tube. Flux generally uses super-grade rosin as the matrix material, and adds a certain activator. Tubular solder wire is generally suitable for manual welding.
2. Anti-oxidation solder
The anti-oxidation solder used in PCBA processing is to add a small amount of active metal to the tin-lead alloy, which can reduce the tin oxide and lead oxide, and float on the surface of the solder to form a dense covering layer, thereby protecting the solder from further oxidation. This type of solder is suitable for dip soldering and wave soldering.
3. Silver-containing solder
Silver-containing solder is to add 0.5% to 2.0% of silver in tin-lead solder, which can reduce the amount of silver melting in the solder in the silver-plated parts, and can reduce the melting point of the solder.
Second, solder paste
Welding powder is a metal powder used for welding, and its diameter is 15～20µm. At present, there are Sn-Pb, Sn-Pb-Ag, Sn-Pb-In and so on. Organic matter includes resin or some resin flux mixture, used to adjust and control the viscosity of solder paste. The flux used is thixotropic glue, lubricant, metal cleaning agent.
3. Flux
The flux is mainly used in tin-lead soldering, which helps to clean the soldered surface, prevent oxidation, increase the fluidity of the solder, make the solder joint easy to form, and improve the soldering quality.
