In today's rapidly developing technology, various high-tech electronic products are constantly emerging, which has led to a sharp increase in demand for printed circuit boards from PCB manufacturers. The difficulty of production is becoming higher and the quality requirements are becoming increasingly strict. To ensure the high quality and stability of printed circuit boards, complete the quality management of PCB factories, and control the environment, it is necessary to have a thorough understanding of the characteristics of printed circuit board production skills. But the skill of making printed circuit boards is a comprehensive skill crystallization, which involves fundamental knowledge in physics, chemistry, optics, photochemistry, polymers, fluid mechanics, chemical kinetics, and many other aspects. Because there are many aspects and issues involved, it is easy for various quality defects to occur. Therefore, it is necessary to carefully understand the quality problems that occur in each process, quickly adopt process methods to eliminate them, and improve the production efficiency of PCBs.

Reason:

⑴ Differences in latitude and longitude directions result in changes in substrate scale; Due to the lack of attention to the fiber direction during shearing, residual shear stress is formed within the substrate. Once released, it directly affects the shortening of the substrate scale.

The copper foil on the surface of the substrate is etched away, which constrains the changes in the substrate and causes a scale change when stress is relieved.

When brushing the board, excessive pressure was used, resulting in compressive and tensile stress that caused deformation of the substrate.

The resin in the substrate is not completely cured, resulting in a change in scale.

⑸ Especially for multi-layer boards, poor storage conditions before lamination can cause thin substrates or semi cured sheets to absorb moisture, resulting in poor dimensional stability.

When multi-layer boards are pressed together, excessive glue flow causes deformation of the glass cloth.

resolvent:

⑴ Determine the change pattern of latitude and longitude directions and compensate for it on the film according to the shortening rate (this work should be done before light painting). When cutting together, process according to the fiber direction or according to the character markings provided by the manufacturer on the substrate (usually the vertical direction of the characters is the vertical direction of the substrate).

When designing circuits, efforts should be made to make the entire board surface evenly distributed. If it is not possible, it is necessary to leave a transition section in space (without affecting the orientation of the circuit). This is due to the difference in the density of warp and weft yarns in the glass cloth structure used for the board, resulting in a difference in the strength of the board in the warp and weft directions.

⑶ Trial brushing should be selected to ensure that the process parameters are in good condition, and then the rigid plate should be processed. For thin substrates, chemical cleaning processes or electrolytic processes should be used for cleaning treatment.

⑷ Adopt baking method to solve the problem. Especially before drilling, baking should be carried out at a temperature of 120 ℃ for 4 hours to ensure resin curing and reduce substrate scale deformation caused by the influence of heat and cold.

It is necessary to bake the substrate with oxidized inner layer to remove moisture. And store the processed substrate in a vacuum drying oven to avoid further moisture absorption.

⑹ It is necessary to conduct process pressure testing, adjust process parameters, and then impose restrictions. We can also choose the appropriate amount of adhesive flow based on the characteristics of the semi cured sheet.

Article source: Jiangmen single-sided and double-sided circuit boardhttp://www.yonghongpcb.com/