Features of PCB board micro-hole mechanical drilling
Now that electronic products are updating rapidly, the printing of PCBs has expanded from the previous single-layer boards to double-layer boards and multi-layer boards with higher accuracy requirements. Therefore, the processing requirements of circuit board holes are increasing, for example: the hole diameter is getting smaller and smaller, and the distance between holes is getting smaller and smaller. It is understood that more epoxy resin-based composite materials are currently used in board factories. The definition of the hole size is small holes below 0.6mm in diameter and microholes below 0.3mm. Today I will introduce the machining method of the micro hole: mechanical drilling.
In order to ensure high processing efficiency and hole quality, we reduce the ratio of defective products. In the process of mechanical drilling, two factors, axial force and cutting torque, must be considered, which may directly or indirectly affect the quality of the hole. The axial force and torque will increase with the feed and the thickness of the cutting layer, so the cutting speed will increase, so that the number of cutting fibers per unit time will increase, and the amount of tool wear will also increase rapidly. Therefore, the life of the drill is different for different holes. Operators should be familiar with the performance of the equipment and replace the drill in time. This is also the reason why the cost of micro-holes is higher.
In the axial force, the static component force FS affects the cutting of the wide-blade Guangde, while the dynamic component force FD mainly affects the cutting of the main cutting edge. The dynamic component force FD has a greater impact on the surface roughness than the static component force FS. Generally, when the diameter of the prefabricated hole is less than 0.4mm, the static component force FS decreases sharply with the increase of the hole diameter, and the dynamic component force FD decreases more flatly.
The wear of the PCB drill is related to the cutting speed, feed rate, and slot size. The ratio of the bit radius to the width of the glass fiber has a greater effect on the tool life. The larger the ratio, the larger the fiber cutting fiber bundle width, and the greater the tool wear. In practical applications, a 0.3mm drill can drill 3000 holes. The larger the drill, the fewer holes are drilled.
In order to prevent problems such as delamination, hole wall damage, stains, and burrs during drilling, we can first place a 2.5mm thickness pad under the layer, place the copper clad board on the pad, Put the aluminum sheet on the copper clad board. The function of the aluminum sheet is to protect the surface of the board from scratches. 2. Good heat dissipation, the drill bit will generate heat when drilling. 3. Buffering effect / drilling effect to prevent deviated holes. The way to reduce burrs is to use vibration drilling technology. Hard carbide drills are used for drilling. The hardness is good. The size and structure of the tool also need to be adjusted.