In the production of PCBA SMT machine, the cracking of chip components is common in the multilayer chip capacitor (MLCC), which is mainly caused by thermal stress and mechanical stress.
1. The STRUCTURE of MLCC capacitors is very fragile. Usually, MLCC is made of multi-layer ceramic capacitors, so it has low strength and is easy to be impacted by heat and mechanical force, especially in wave soldering.
2. During the SMT process, the height of the z-axis of the pick and place machine is determined by the thickness of the chip components, not by the pressure sensor, especially for some of the SMT machines that do not have the z-axis soft landing function, so the cracking is caused by the thickness tolerance of the components.
3. Buckling stress of PCB, especially after welding, is likely to cause cracking of components.
4. Some PCB components may be damaged when they are divided.
Preventive measures:
Carefully adjust the welding process curve, especially the preheating zone temperature should not be too low;
The height of z-axis should be carefully adjusted in the SMT machine;
The cutter shape of the jigsaw;
The curvature of PCB, especially after welding, should be corrected accordingly. If the quality of PCB is a problem, it should be considered.
Post time: Aug-19-2021