PCB assembly technology has two types of typical technics flow, one is solder paste → reflow soldering technics, and the other is adhesive glue→ wave soldering technics. In the latter case, the chip components are bonded to the surface of the PCB by PCB assembly chip, and the through-hole components are inserted on the other side of the PCB, and after the PCB manufactured and assembled, and the assembly work can be smoothly completed by wave soldering. The function of the PCB adhesive glue is to temporarily fix the surface-mount components to the corresponding welding pattern of the PCB before the wave soldering, so as to avoid the components falling off during the wave soldering after the PCB assembly. After the PCB assembly and soldering is completed, although it loses its function, it remains on the PCB and has good bonding strength and electrical insulation properties.
First, the chemical composition of PCB assembly adhesive glue
The pcb assembly chip typically consists of matrix resin, curing agent and solid promoter, toughening agent, and a filler.
(1) Matrix resin. The matrix resin is the core of the adhesive glue, typically an epoxy resin and an acrylate polymer. Polyurethanes, polyesters, silicone polymers, and epoxy-acrylate copolymers have also been used in recent years.
(2) Curing agent and solid accelerator. The adhesive glue is a viscous glue at room temperature and has a certain viscosity. After mounting must be cured to temporarily fix the components on the PCB. Therefore, it is usually necessary to add some curing agent to promote the curing.
(3) Toughener. In order to make up for this defect, since the simple matrix resin is brittle after curing, it is necessary to add a toughening agent to the formulation to improve the toughness of the cured adhesive glue.
(4) Filler. The addition of the filler can improve certain properties of the adhesive glue, such as improving the electrical insulation properties and high temperature resistance of the adhesive glue, and also obtaining suitable viscosity and bonding strength of the adhesive glue.
The above is the industry information provided by FASTPCBA company, I hope it’s helpful to you!