Mechanical stress is the internal force that interacts with each part of an object when it is deformed due to an external cause (force, load, temperature, etc.) to resist the effect of this external cause, and tries to make the object from the deformed position. Revert to the position before the deformation.
The mechanical stress in the assembly manufacturing process mainly includes the following aspects:
1. The force acting on PCBA during the operation of tooling equipment.
For example, when the PCBA is disassembled from a very tight fixture, chip capacitors may be cracked; the second side of the double-sided printing may be misaligned, resulting in cracks or damage to the top-mounted components. The board is broken or the components are damaged.
2, the rapid difference between the cold and hot changes in the welding process on the PCBA force.
In reflow soldering, wave soldering, and manual soldering PCBA processes, when the temperature difference is too large, the PCB may warp. Solder curing causes mechanical stress on components on the PCB, resulting in stress cracks in the ceramic and glass components of the component. Stress cracking is an unfavorable factor affecting the long-term reliability of solder joints.
3, tolerance to mechanical shock by collision and fall when PCBA board is taken improperly
Solder joints are generally not damaged by mechanical impact. However, other parts of the welded structure may fail. For example, the large inertia force of a large and heavy leaded component subjected to a mechanical impact may cause peeling of the copper plate on the PCB or breakage of the plate, and the component itself may also be damaged.
4, PCBA packaging improper protection, tolerance to vibration in the transport process.
For packaging protection of PCBA, consideration should be given to the design of packaging materials. For PCBA transportation, the use of a dedicated anti-static box is supplemented by a built-in knife card.