Question

Why are there cracks at the bottom of PCB stress holes?

Answer 1

Cracks at the bottom of PCB stress holes may be due to the following reasons:

1. Improper selection of boards. If a thinner plate is used, the strength and bending resistance of the plate will be poor; deformation cracks will occur. After the components are welded to the PCB board, the board bends excessively, causing the PCB board to deform, resulting in cracks.

2. Improper layout design. If the layout is unbalanced, the mechanical stress of the plate will be concentrated.

3. Improper manufacturing process. Improper temperature and humidity control may result in damage to the board.

4. Improper drilling or copper sinking. Such as poor drilling, copper bubbles, etc.

5. Extrusion cracks. Due to incorrect parameter settings of the pick-and-place machine, components squeeze the PCB board during placement, resulting in cracks.

6. Different thermal expansion coefficients. Different materials have different thermal expansion coefficients. When the temperature changes, the difference in thermal expansion causes the PCB board to deform and cause cracks.

Answer 2

The reasons for PCBA board welding cracks are as follows:

1. The infiltration of the circuit board pad and component soldering surface did not meet the requirements of production and processing.

2. The solder paste does not meet the production standards as required.

3. The thermal expansion coefficients of various components of the welding and electrode materials are asymmetric, and the spot welding is unstable during condensation.

4. The standard setting of the reflow soldering temperature curve cannot allow the organic chemicals and moisture in the solder paste to evaporate before entering the reflow area.

5. The difficulties in processing lead-free materials in SMT manufacturers are high temperature, high interface tension and high viscosity.