Characteristics of PCB microhole mechanical drilling
Today, with the rapid update of electronic products, PCB printing has expanded from previous single-layer boards to double-layer boards and complex multi-layer boards of higher complexity. Therefore, there are more and more processing requirements for the plate holes, for example, the holes are getting smaller and smaller, and the distance between the holes and the holes is getting smaller and smaller. It is understood that more epoxy resin-based composite materials are used in the sheet metal factory. The pore diameter is defined as a small hole having a diameter of 0.6 mm or less and a micro hole having a diameter of 0.3 mm or less. Today I will introduce the micropore processing method: mechanical drilling.
To ensure high processing efficiency and hole quality, we have reduced the proportion of defective products. In the mechanical drilling process, two factors, axial force and cutting torque, are considered, which may directly or indirectly affect the quality of the hole. The axial force and torque increase with the feed amount and thickness of the cutting layer, and the cutting speed is further increased, so that the number of cutting fibers per unit time increases, and the amount of tool wear increases rapidly. Therefore, the life of the drill bit is different for different sized holes. The operator should be familiar with the performance of the equipment and replace the drill bit in time. This is why the cost of handling tiny holes is higher.
The static component FS in the axial force affects the lateral blade wide-cutting, while the dynamic component FD mainly affects the cutting of the main cutting edge. The dynamic component force FD has a greater influence on the surface roughness than the static component force FS. Generally, when the preformed hole diameter is less than 0.4 mm, the static component force FS sharply decreases as the pore diameter increases, and the dynamic component force FD decreases as the flattening tendency.
The wear of the PCB bit is related to the cutting speed, the feed rate and the size of the groove. The ratio of the bit radius to the fiberglass width has a large impact on tool life. The greater the ratio, the greater the fiber bundle width of the tool and the greater the tool wear. In practical applications, a 0.3 mm drill can drill 3000 holes. The larger the drill bit, the less the drill hole.
In order to prevent delamination, hole wall damage, stains and burrs during drilling, we can place a 2.5mm thick pad under the layer and place the CCL on the backing plate. The aluminum plate is placed on the copper clad plate, and the function of the aluminum plate is 1. The surface of the plate is not rubbed. 2. The heat dissipation is good, and the drill bit will generate heat when drilling. 3. Buffer effect / drilling action to prevent local holes. The way to reduce burrs is to use vibratory drilling techniques. Drilling with carbide drills, hardness, and the size and structure of the tool needs to be adjusted.