As the foundation of electronic devices, The quality of PCB directly affects the performance and reliability of the product. In the PCB manufacturing process, drilling is a crucial step that not only affects the implementation of electrical connections, but also affects the mechanical strength and signal transmission quality of the entire board. This article will introduce the basic concepts, processing methods, and importance of PCB drilling in simple and concise terms.
1 The importance of PCB drilling
There are two main types of holes on PCBs: through holes and blind/buried holes. Through holes run through the entire board layer, used to connect wires in the top, bottom, or middle layers; Blind holes and buried holes refer to only partially penetrating the board layer or completely buried inside the board, mainly used in high-density interconnect (HDI) boards to save space and improve signal transmission efficiency.
Drilling not only provides physical support for the installation of components, such as the welding of plug-in components, but more importantly, it forms conductive holes through processes such as copper plating, achieving electrical interconnection between different layers. Therefore, the accuracy of drilling and the smoothness of the hole wall directly affect the electrical performance and signal integrity of PCBs.
II PCB drilling processing method
Mechanical drilling: This is the most traditional and basic PCB drilling method. Using a high-speed rotating micro drill bit, accurately drill the required size holes according to the design drawings. Mechanical drilling is suitable for through hole machining and can handle holes ranging from standard diameters to very small sizes. The material of drill bits is usually hard alloy to ensure machining accuracy and durability. In order to improve drilling efficiency and accuracy, modern drilling machines are usually equipped with precision positioning systems and automatic tool changing devices.
Laser drilling: With the development of high-density PCBs, laser drilling technology has been widely used due to its non-contact processing, high precision, and flexibility. Laser can quickly and accurately form tiny blind or buried holes on PCBs, making it particularly suitable for the production of HDI boards. Laser drilling can be divided into various types such as carbon dioxide laser, ultraviolet laser, etc. Among them, ultraviolet laser is more suitable for fine processing due to its wavelength and energy concentration.
Plasma etching/chemical etching: These methods are mainly applied to the production of more complex HDI boards, especially to form small buried hole structures. Remove copper foil and substrate in specific areas through chemical reagents or plasma reactions, forming pores. These methods require a combination of multiple processes, including photolithography, etching, and subsequent metalization, to ensure the conductivity and stability of the hole wall.
3、 Treatment after drilling
After drilling is completed, the hole wall usually needs to undergo a series of treatments to enhance its electrical performance and mechanical strength. This includes:
Copper plating: By electroplating or chemical copper plating, the inner and outer surfaces of the hole walls are covered with a uniform layer of copper, achieving electrical connections between the layers.
Deburring: Use chemical or mechanical methods to remove burrs from the edge of the hole, ensuring a smooth hole wall and reducing signal interference.
Solder resist treatment: Apply solder resist ink to non connected areas to prevent short circuits and protect the hole walls from corrosion.
PCB drilling is an indispensable part of PCB manufacturing, and its technology and process level directly affect the overall performance of circuit boards. With the continuous progress of electronic technology, the requirements for the accuracy, efficiency, and complexity of PCB drilling are also increasing. Therefore, mastering and applying advanced drilling technology is crucial for improving the quality of electronic products and meeting the market demand for miniaturized and high-performance products.