How to improve the dimensional accuracy of high-frequency PCBs?

In high frequency pcb processing, strict control of dimensional accuracy can improve product performance and ensure overall quality. From material selection to process optimization to strict quality control, every step needs to be meticulous to achieve high-precision manufacturing goals.

Material selection

In high-frequency PCB processing, the selection of high-quality raw materials is the basis for ensuring dimensional accuracy and product performance. Reasonable selection and management of raw materials can enhance processing stability and optimize PCB electrical performance.

Material quality and durability
Material uniformity: Select materials with uniform thickness and composition, such as FR-4 and ceramic substrates, to reduce deformation and error.

Heat and chemical resistance: Materials need to be resistant to high temperatures and chemical corrosion, such as polyimide, to extend service life and reduce dimensional deformation.

Mechanical strength: Materials with high tensile strength and hardness can avoid cracks and damage and maintain dimensional stability.

Material quality and durability
Thickness accuracy: Select materials with small thickness tolerance to reduce stacking and drilling errors.

Coefficient of thermal expansion (CTE): Select low CTE materials that match the copper foil to avoid dimensional changes caused by thermal expansion and contraction.

Humidity stability: Use materials with low hygroscopicity, such as ceramic substrates, to reduce the impact of humidity changes on dimensions.

Optimization of process parameters

Etching parameter optimization
The etching determines the size of the wires and gaps on the circuit board. By optimizing etching parameters, such as the concentration of the etching solution, temperature, etching time, etc., the etching rate and etching depth can be controlled, thereby achieving control of dimensional accuracy.

Optimization of copper plating parameters
Copper plating is to form a conductive layer on the surface of the circuit board. By optimizing parameters such as the composition of the copper plating solution, current density, and copper plating time, the copper plating process can be accurately controlled to ensure a uniform and required copper layer.

Drilling parameter optimization
Drilling is an important step in forming connection holes on the PCB board. By selecting the appropriate drill bit and controlling drilling speed, pressure and other parameters, you can ensure that the size and location of the drill hole meet the design requirements.

In addition to the key process steps mentioned above, there are many other parameters that need to be optimized, such as pattern overlay, lamination parameters, etc.

High-precision processing technology

Positioning accuracy of inner layer boards
Use high-precision alignment and lamination equipment to ensure accurate alignment between inner layer boards. The optical alignment system can detect and adjust the position of inner layer boards in real time to improve positioning accuracy. In addition, optimize the lamination process, control temperature, pressure and time to ensure stable interlayer bonding and avoid dimensional errors caused by poor bonding.

Control drilling accuracy and positioning accuracy
Optimize drill speed, feed speed and pressure to reduce burrs and deviations and improve drilling accuracy. In the process of drilling multilayer circuit boards, use high-precision alignment and clamping systems to ensure that the holes of each layer are aligned and avoid interlayer misalignment.

Cutting accuracy and positioning accuracy
Use laser cutting machines to achieve high-precision plate cutting, with high laser beam fineness and controllability, reducing mechanical cutting errors. For complex shapes, CNC milling machines can accurately mill various shapes and openings through computer control to ensure dimensional accuracy.

Strict quality control and testing methods

Detecting the accuracy and precision of measuring equipment
1. Optical measurement

Optical measurement technology, such as AOI, can quickly detect defects on PCBs, including open circuits, short circuits and dimensional deviations.

2. Coordinate measurement

Coordinate measuring machines (CMMs) can provide high-precision dimensional data, especially for PCBs with complex structures and high precision requirements.

Quality inspection for each link
1. Incoming material inspection
Raw materials are strictly inspected upon entry to ensure that their thickness, uniformity and other key parameters meet the requirements. Use high-precision measuring equipment, such as thickness gauges and optical microscopes, to inspect materials.

2. Process control
Real-time monitoring and feedback are implemented in key process steps, such as etching, copper plating, drilling and cutting. For example, during etching, the etching rate and depth are detected in real time, and the etching parameters are automatically adjusted to ensure dimensional accuracy.

3. Intermediate inspection
Intermediate inspection is performed after each key process. For example, after multilayer board stacking and drilling, the interlayer alignment and hole position accuracy are checked to ensure the accuracy of the foundation for subsequent processing.

Other strict quality control measures
1. Finished product inspection

Final inspection is carried out before the finished product leaves the factory to ensure that all dimensions and electrical performance indicators meet the design requirements. Use X-ray inspection (X-Ray) and AOI systems to non-destructively inspect the internal structure and external features of the circuit board.

2. Environmental control

Strictly control the temperature, humidity and cleanliness of the production environment to reduce the impact of environmental factors on dimensional accuracy. Use clean rooms in key process steps to reduce the impact of dust and impurities on PCB processing.

3. Employee training

Strict training and assessment of operators to ensure that they have the necessary technical skills and quality awareness to correctly operate equipment and perform quality control procedures.

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