In the field of electronic device manufacturing, printed circuit boards (PCBs), as core components, the precision and efficiency of their manufacturing processes directly determine the performance and quality of electronic products. Laser marking machines, as advanced processing equipment, have deeply integrated into the PCB industry with many unique advantages and have become a key force in promoting the innovation of PCB manufacturing technology.
Principles and Classification of Laser Marking Machines
Working Principle
Laser marking machines use a high - energy - density laser beam to irradiate the surface of the workpiece, causing the surface - layer material to vaporize instantaneously or undergo a chemical reaction that changes its color, thus leaving a permanent mark. After being focused, the laser forms a tiny spot, which acts like a precision tool for high - precision marking on the surface of the object, and the marking line accuracy can reach the millimeter - to - micrometer level. Take the scanning - type laser marking machine as an example. The operator inputs the required marking information into the computer through the marking software. The software converts the information into signals to control the laser and the X - Y scanning system. The expanded and collimated laser is focused by the F - θ field lens and scans on the surface of the PCB to complete the marking process.
Classification Methods
Classification by Light Source
- CO₂ Laser Marking Machine: It uses CO₂ gas as the working medium and generates a laser with a wavelength of 10.64um through glow discharge. After being scanned by a galvanometer and focused by an F - Theta lens, it is marked under the control of a computer and a laser marking control card. This equipment has high power and strong stability and is suitable for wide - range cutting of thick sheet metal and non - metal materials such as wood, plastic, and glass. In the PCB industry, it is often used for the processing of non - metal substrate materials.
- YAG Laser Marking Machine: It uses a YAG crystal as the laser medium and outputs near - infrared light with a wavelength of 1.06μm, which is easily absorbed by metal materials, causing material evaporation. It is often used for marking metal materials and parts and is widely used in the marking and processing of the metal parts of PCBs. It has the characteristics of stable operation and high processing quality.
- Fiber Laser Marking Machine: It uses a rare - earth - doped glass fiber as the gain medium. Under the action of pump light, a high - power density is formed to achieve laser oscillation output. It has excellent beam quality, high cutting accuracy, fast speed, strong flexibility, good cut - edge quality, high energy efficiency, and low maintenance cost, and is the most widely used in the PCB industry.
- Classification by Marking Method
- Mask - type: It consists of a laser, a mask plate, and an imaging focusing lens. The laser beam is uniformly irradiated on the pre - carved mask plate, and the transmitted part is focused on the material surface through a lens to achieve marking. The marking speed is fast, and one laser pulse can complete one mark, which is suitable for online flying marking of a large number of products. However, its flexibility is poor. Different marking contents require replacing the mask plate, and the energy utilization rate is low.
- Dot - matrix type: Multiple parallel small lasers simultaneously emit pulsed lasers. After being reflected by mirrors and focused by lenses, the laser pulses are focused on the surface of the processed material to ablate small pits to form characters and patterns. Generally, a small - power RF - excited CO₂ laser is used, and the marking speed can reach up to 6000 characters per second, which is an ideal choice for high - speed online marking. However, it can only mark dot - matrix characters, has limited resolution, and has difficulties in marking complex patterns or Chinese characters.
- Scanning type: It consists of a computer, a laser, and an X - Y plane scanning system. The laser and the scanning system are controlled by a computer and marking software, allowing the laser to scan on the surface of the processed material to form a mark. It has a fast marking speed and high accuracy, can perform fine marking and even bitmap marking, and has strong adaptability. It is the current mainstream marking method.Specific Applications of Laser Marking Machines in the PCB Industry
PCB Marking and Traceability
In the PCB production process, to effectively manage the entire life cycle of products, it is necessary to mark key information on the PCB board, such as production batches, characters, barcodes, and QR codes. Laser marking machines can accurately and clearly mark this information to meet the product traceability requirements. From production and manufacturing to after - sales service, by reading the laser marks on the PCB board, information such as the production batch, production date, and raw material source of the product can be accurately traced, helping enterprises improve their quality control level and after - sales service quality.
- Removing Surface Coatings: In PCB manufacturing, some process steps require the removal of surface coatings in specific areas. For example, before welding or connection, the surface solder - resist layer needs to be removed. The laser marking machine can accurately remove the coating using a high - energy laser beam without damaging the substrate, providing a good foundation for subsequent processes.
- Surface Micro - processing: With the development of electronic products towards miniaturization and high integration, the requirements for the precision of PCB surface micro - processing are increasing day by day. Laser marking machines can achieve micron - level processing accuracy and can perform micro - groove processing, micro - structure fabrication, etc. on the PCB surface. When manufacturing high - density interconnect (HDI) boards, tiny vias are processed by laser marking machines to achieve electrical connections between different layers.