In the miniaturization and complication process of modern electronic devices, PCB (printed circuit board) plays a crucial role. As a bridge between electronic components, PCB ensures the effective transmission of signals and the stable supply of power. However, during its precise and complex manufacturing process, various defects occur from time to time, affecting the performance and reliability of the products. This article will discuss with you the common defect types of PCB circuit boards and the reasons behind them, providing a detailed “health check” guide for the design and manufacture of electronic products.
1. Short circuit and open circuit
Reason analysis:
Design Errors: Negligence during the design phase, such as tight routing spacing or alignment issues between layers, can lead to shorts or opens.
Manufacturing process: Incomplete etching, drilling deviation or solder resist remaining on the pad may cause short circuit or open circuit.
2. Solder mask defects
Reason analysis:
Uneven coating: If the solder resist is unevenly distributed during the coating process, the copper foil may be exposed, increasing the risk of short circuits.
Poor curing: Improper control of baking temperature or time causes the solder resist to fail to fully cure, affecting its protection and durability.
3. Defective silk screen printing
Reason analysis:
Printing accuracy: The screen printing equipment has insufficient accuracy or improper operation, resulting in blurred, missing or offset characters.
Ink quality issues: Use of inferior ink or poor compatibility between the ink and the plate affects the clarity and adhesion of the logo.
4. Hole defects
Reason analysis:
Drilling deviation: drill bit wear or inaccurate positioning causes the hole diameter to be larger or deviate from the designed position.
Incomplete glue removal: The residual resin after drilling is not completely removed, which will affect the subsequent welding quality and electrical performance.
5. Interlayer separation and foaming
Reason analysis:
Thermal stress: The high temperature during the reflow soldering process may cause a mismatch in expansion coefficients between different materials, causing separation between layers.
Moisture penetration: Underbaked PCBs absorb moisture before assembly, forming steam bubbles during soldering, causing internal blistering.
6. Poor plating
Reason analysis:
Uneven plating: Uneven distribution of current density or unstable composition of the plating solution results in uneven thickness of the copper plating layer, affecting conductivity and solderability.
Pollution: Too many impurities in the plating solution affect the quality of the coating and even produce pinholes or rough surfaces.
Solution strategy:
In response to the above defects, measures taken include but are not limited to:
Optimized Design: Utilize advanced CAD software for precise design and undergo rigorous DFM (Design for Manufacturability) review.
Improve process control: Strengthen monitoring during the production process, such as using high-precision equipment and strictly controlling process parameters.
Material selection and management: Select high-quality raw materials and ensure good storage conditions to prevent materials from getting damp or deteriorating.
Quality inspection: Implement a comprehensive quality control system, including AOI (automatic optical inspection), X-ray inspection, etc., to detect and correct defects in a timely manner.
By in-depth understanding of common PCB circuit board defects and their causes, manufacturers can take effective measures to prevent these problems, thereby improving product yield and ensuring the high quality and reliability of electronic equipment. With the continuous advancement of technology, there are many challenges in the field of PCB manufacturing, but through scientific management and technological innovation, these problems are being overcome one by one.