At the rapid pace of electronics updates, PCB printing has expanded from previous single panels to double panels and more complex layers with high precision. Therefore, the circuit board hole processing requirements are more and more, such as: the aperture is getting smaller and smaller, the hole and the hole spacing is getting smaller and smaller. It is understood that now the board factory now uses more is epoxy resin based composite material, the definition of the hole size is the diameter of 0.6mm for small hole, 0.3mm for micro hole.
Today I will introduce the processing method of small holes: mechanical drilling.
In order to ensure high processing efficiency and hole quality, we reduce the ratio of bad products. During the mechanical drilling process, the axial force and the cutting torque are taken into account, which may directly or indirectly affect the quality of the hole. The axial force and torque will also increase with the feed amount and the thickness of the cutting layer, so the cutting speed will increase, so that the number of cutting fibers per unit of time will increase, and the amount of tool wear will also increase rapidly. Therefore, for the different sizes of holes, the life of the drill knife is also different, and the operators should be familiar with the performance of the equipment to replace the drill knife in time. This is also why small holes are added, the cost of work is higher.
In axial force, FS of static dividing force affects the wide-German cutting of the horizontal blade, while dynamic force FD mainly affects the cutting of the main cutting blade, and dynamic force FD has a greater impact on the surface roughness than static force FS. Generally, when the prefabricated aperture is less than 0.4mm, the static distraction FS decreases sharply with the increase of the aperture, while the trend of the dynamic distraction FD decreasing is more flat.
The wear of the PCB drill bit is related to the cutting speed, the feed amount, and the size of the groove hole. The ratio of the drill bit radius on the glass fiber width has a great impact on the tool life. The greater the ratio is, the greater the tool cutting fiber bundle width is, and the tool wear also increases. In practice, a 0.3mm drill tool has a full life of 3,000 holes. The larger the drill knife, the fewer holes are drilled.
In order to prevent layering, hole wall damage, stain, burr and these problems, we can first put a 2.5mm thickness cushion plate under the layer, put the copper clad plate on the cushion plate, and then put on the aluminum sheet, aluminum sheet function is 1. Protect the plate surface will not wipe flowers.2. Good heat dissipation, and the drill bit will produce heat when drilling.3. Buffering action / lead drilling action to prevent partial holes. The method to reduce the burr is to use the vibrational drilling technology, using a carbide carbide drill bit drilling, good hardness, the size and structure of the tool also need to be adjusted.