Basics of PCB Soft Brazing
PCB soldering can be divided into the following three categories: fusion soldering, pressure soldering and brazing. Besides, there are other types of soldering like ultrasonic pressure soldering, gold ball bonding and laser soldering.
Brazing can be divided into hard brazing and soft brazing. The former refers to high-temperature large-scale soldering, the latter refers to lower-temperature small-size soldering like component soldering. The following is the supplementary to soft brazing.
Soft brazing refers to the soldering at temperatures below 450°C. That means the fusion point of soft brazing solder is lower than that of components, so components won't melt in the process of brazing, but soft brazing solder can be basically eliminated. This implies that soft brazing process is reversible.
When soldering metal, the soldered metal is heated to a certain temperature range, the activation of the soldering flux will be enough to remove oxide and pollutants on the metal surface. As solder occurs between solder and soldered metal surface, the solder will become solid after the solder joint is formed and cooled down. The extension strength is related to the lattice structure and thickness of the bonding layer between metals.
The main procedure of soft brazing contains wetting, diffusion, dissolution and metallurgic bonding.