Detailed explanation of PCB drilling key technologies and precautions in the PCB production process

In the manufacturing process of printed circuit boards (PCB), drilling technology plays a core role and is a key step in achieving electrical interconnection between different layers. This article will delve into the technology, process, challenges, and techniques for improving the quality of PCB drilling, aiming to provide comprehensive guidance for PCB engineers and manufacturers.

1、 Overview of PCB Drilling Technology

PCB drilling mainly uses two techniques: mechanical drilling and laser drilling.

Mechanical drilling: suitable for larger sized holes, with relatively low cost, but limited accuracy. The lifespan of the drill bit varies with the hardness of the material, and it is prone to burrs and resin coating.

Laser drilling: capable of precise drilling with smaller apertures, suitable for high-density interconnect HDI PCB boards. Despite its high cost, it can effectively handle complex materials and reduce thermal effects.

2、 Drilling process and technical details

Pre processing: The laminated board is loaded onto the drilling machine, and the burr formation is reduced through the export material panel, while covering with aluminum foil for heat dissipation.

Drill bit selection: HSS (high-speed steel) and cemented carbide (WC) are commonly used materials, with cemented carbide being more suitable for processing glass fiber reinforced polymer (GFRP). Drill bit designs with a top angle of 130 ° and a helix angle of 30 ° -35 ° help improve efficiency and accuracy.

CNC drilling machine: The CNC controlled drilling machine precisely drills holes according to preset coordinates, reduces resin coating through high-speed rotation, and ensures accurate hole positions.

3、 Important considerations for drilling

Aspect ratio: It directly affects the copper plating ability, and maintaining a reasonable aspect ratio (such as PTH of 10:1 and micropores of 0.75:1) is crucial to ensure good electrical performance.

Copper drilling gap: Maintain an appropriate distance between the edge of the hole and the copper features to avoid short circuits, with a typical value of 8 mils.

4、 Classification and specifications of drilling holes

Electroplated through-hole (PTH): used for multi-layer interconnection, with a minimum finished hole size of 0.006 inches.

Non electroplated through-hole (NPTH): used for mounting holes, with no conductivity requirements, the minimum finished hole size is the same, but the edge to edge gap is smaller.

5、 Potential drilling problems and their remedial measures

During the drilling process, there may be issues such as drill bit wear, hole roughness, resin coating, burrs, nail heads, and delamination. Solutions include:

The process of removing adhesive residue removes resin,

The deburring process improves the quality of the hole wall,

Use laser drilling to reduce the risk of stratification.

6、 Techniques for improving drilling quality

Guide hole: Pre drill guide holes to ensure accurate positioning of the drill bit.

Drill bit selection and speed: Select the drill bit correctly based on the aperture, and control the appropriate drilling speed and power.

Drilling machine usage: Use the drilling machine to improve drilling accuracy and efficiency, and correctly set drilling machine parameters.

Post processing: After drilling, thoroughly clean the holes and perform appropriate soldering treatment to enhance conductivity and stability.

7、 DFM (Design for Manufacturing) Verification Techniques

Optimize aspect ratio and drilling size, reduce drill bit types to improve efficiency.

Accurately define drilling types, rigorously verify drilling data, and ensure consistency with production requirements.

Pay special attention to small closed holes and edge copper features to prevent potential manufacturing issues.

Through the above in-depth analysis, it is not difficult to see that PCB drilling is not only a simple physical process, but also a comprehensive consideration of process technology, design rules, and quality control. Correct design, rigorous process control, and meticulous post-processing are the key to ensuring PCB drilling quality and improving overall circuit board reliability.