Today, Lexus will give you some knowledge about important materials for SMT chip processing.

1. SMT chip processing technology solder paste

Solder paste is a paste made of alloy solder powder and paste flux evenly stirred. It is an indispensable welding material in SMT chip processing technology and is widely used in reflow soldering. Solder paste has a certain viscosity at room temperature and can initially stick electronic components to predetermined positions. At the soldering temperature, as the solvent and some additives evaporate, the components to be soldered and the PCB are connected to each other, forming a connection.

Most of the current SMT placement machines use the wire stencil printing method to apply solder paste, which is easy to operate and can be used after fast printing. However, it is also difficult to ensure the reliability of the solder joints, which is easy to cause virtual soldering, waste of solder paste, and high cost.

2. SMT chip processing technology chip adhesive

SMD glue, also known as SMT glue, SMT red glue, is usually red (also yellow or white). Adhesives such as hardeners, pigments, solvents, etc. are evenly distributed in the slurry, which are mainly used to fix components on the printed board. It is generally distributed by dispensing or stencil printing. After the components are pasted, they are placed in an oven or reflow oven to heat and harden.

Different from solder paste, the patch adhesive is cured after heating, and its freezing point temperature is 150°C, and it will not melt after being heated again, which means that the thermal hardening process of the patch adhesive is irreversible. The application effect of SMT glue will vary depending on the thermal curing conditions, connection objects, equipment used, and operating environment. When using SMT adhesives, the adhesive should be selected according to the PCB and PCA process.

3. Flux for SMT chip processing technology

Flux is the carrier of solder powder, and its composition is basically the same as that of general flux. In order to improve the printing effect, it is sometimes necessary to add an appropriate amount of solvent. Through the action of the activator in the flux, the solder can quickly diffuse through the oxides of the solder powder itself and adhere to the surface of the metal to be soldered. The composition of the flux plays a decisive role in the expansion, wettability, collapsibility, viscosity change, cleanability and shelf life of the solder paste.