Welding is the core process of PCBA processing, and the reliability of solder joints is directly related to the service life and electrical performance stability of end products.

Pre-welding pretreatment of circuit boards and components serves as the fundamental step. PCBs shall undergo baking treatment to eliminate moisture influence; the flatness of pins for precision components including BGA and QFP needs to be checked. Meanwhile, the storage, temperature recovery and stirring duration of solder paste should be strictly controlled to prevent abnormal solder paste performance which may lead to subsequent welding defects.

The temperature profile of reflow soldering shall be adjusted according to PCB layers and thermal capacity of components. Reasonable parameters for preheating, constant temperature, reflow and cooling zones can lower thermal shock damage to PCB substrates and SMD parts. During wave soldering for through-hole components, operators need to regulate flux spraying volume, tin immersion depth and conveyor tilt angle to minimize bridging, missing solder and voids inside solder joints.

Meanwhile, standardized first article inspection, post-oven AOI automatic optical inspection and sampling solder joint cross-section audit should be implemented throughout the process to classify defective solder joints and trace root causes.

Systematic welding process control helps cut rework and repair costs, improve the first-pass yield of finished PCBA boards, and meet quality delivery requirements for various products such as consumer electronics and industrial control circuit boards.