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PCB routing is a critical step in transforming raw PCB workpieces into finished boards that meet specific specifications. This process utilizes a CNC routing machine, using rotating cutting tools according to pre-programmed procedures to perform precise cutting and drilling operations on the PCB. This process effectively cuts the PCB into the desired design shape and creates various mounting and locating holes.
Detailed Explanation of the PCB Routing Process
Creating the routing strip: This is the initial and crucial step in PCB routing. Engineers use specialized CAM software to generate a precise routing program, also known as the routing strip, based on the client's PCB design and related production materials. The routing strip details all the routing machine parameters used during the processing, including key information such as tool path, rotation speed, feed rate, and cutting depth. The completed routing strip is then transmitted online to the routing machine control system. During production, operators can conveniently access the corresponding routing program based on the work order name or model number, ensuring accuracy and consistency during the processing.
PCB routing
Preparation and Board Stacking: Before officially beginning the routing process, a series of preparatory steps are required.
First, precisely drill locating pins into the bakelite board. These locating pins act as coordinate origins, providing a precise positioning reference for subsequent PCB stacking and processing. Next, stack the PCB worksheets in a specific number based on the thickness of the PCBs. The stacking number varies for PCBs of varying thicknesses to ensure processing accuracy while improving production efficiency. Generally speaking, thinner PCBs can be stacked more frequently, while thicker PCBs can be stacked in smaller numbers. For example, for a 1.0mm thick PCB, 10-15 boards might be stacked per stack; for a 2.0mm thick PCB, 5-8 boards are more appropriate. In actual operation, ensure the flatness of the stacked boards to avoid compromising processing accuracy due to uneven stacking.
Rowing Processing: Once preparations are complete, place the stacked PCBs on the routing machine worktable and start the routing machine. The core component of a guillotine cutting machine is a high-speed rotating tool, typically reaching speeds of tens of thousands of revolutions per minute or even higher. During the machining process, the tool follows a pre-set path on the guillotine tape, performing operations such as cutting and drilling holes in the PCB. When cutting the edges of complex PCBs, the tool must precisely follow a curved path to ensure smooth, dimensionally accurate cuts. During drilling operations, the depth and position of the holes must be strictly controlled to meet the requirements for subsequent electronic component installation. For example, when machining an industrial control board with irregular edges and numerous high-precision mounting holes, the guillotine cutting machine precisely executes the guillotine tape program, enabling efficient and accurate machining, ensuring that the positional error of each mounting hole is kept to a minimal level. During the machining process, the operator must closely monitor the guillotine machine's operating status, regularly checking tool wear and promptly replacing severely worn tools to ensure consistent machining quality.
Cleaning and Quality Inspection: After guillotine cutting, a large amount of dust will remain on and around the PCB surface. This dust is primarily composed of copper shavings and insulation material debris generated during the cutting process. If not removed promptly, it may adversely affect the subsequent installation of electronic components and the electrical performance of the circuit board. Therefore, the finished PCB requires cleaning. This is typically done using specialized cleaning equipment, such as an ultrasonic cleaner or a spray cleaning line. The PCB is placed in a cleaning solution, where ultrasonic vibrations or high-pressure sprays thoroughly remove dust from the board surface. Cleaning lines are often equipped with a drying section to quickly dry the PCB after cleaning to prevent residual moisture. After cleaning, the PCB undergoes rigorous quality inspection. Key inspection items include dimensional accuracy after molding. Critical dimensions of the PCB are typically measured using 2D or 3D measuring instruments to ensure compliance with design requirements. The PCB's appearance is also carefully inspected for defects such as burrs, white spots, and scratches. For cosmetic defects, 100% inspection is typically performed through manual visual inspection or optical inspection equipment to ensure product quality.
Advantages of PCB Routing Processes
Highly flexible customization: PCB routing allows for the production of PCBs with complex shapes and sizes to meet diverse design requirements. Whether it's a small circuit board with irregular edges or a large motherboard requiring numerous specialized mounting holes, the routing process can easily handle it. This highly flexible customization allows PCBs to perfectly adapt to the internal structural designs of various electronic devices, meeting diverse market demands.
High Processing Precision: With the continuous advancement of CNC technology and tool manufacturing techniques, PCB routing can achieve extremely high processing precision. Modern advanced routing machines achieve tool positioning accuracy down to micron levels, effectively ensuring the production of high-precision mounting holes, fine trace edges, and complex, irregular contours. For example, in the processing of high-end chip packaging substrates, routing accuracy directly impacts the quality of the electrical connection between the chip and substrate. High-precision routing can effectively improve the reliability and performance of chip packaging.
Applicable to a variety of substrates: The PCB routing process is suitable for a wide range of PCB substrate types, including common rigid substrates such as FR-4 and CEM-1, as well as some specialized metal-based substrates and flexible circuit board materials. This allows for the selection of appropriate substrates for processing based on the electrical, mechanical, and heat dissipation requirements of the PCB in different application scenarios, further expanding the application range of PCBs.
As a key process in PCB manufacturing, PCB routing plays a decisive role in the final quality and performance of PCB boards. By continuously optimizing process flows, improving machining accuracy, resolving issues such as tool wear and dust pollution, and achieving a balance between machining efficiency and cost, PCB routing technology will continue to play a vital role in the electronics manufacturing field, driving the development of electronic devices towards higher performance and smaller size.