At present, most manufacturers use CNC drilling machines. The CNC drilling machines use hard alloy fixed-handle drills, which are characterized by automatic replacement of drill bits. High positioning accuracy, no need to use a drill sleeve. Large helix angle, fast chip removal, suitable for high speed cutting. In the entire length of the chip flute, the diameter of the drill bit is an inverted cone, the friction with the hole wall during drilling is small, and the drilling quality is high. Drill bits for drilling holes in printed boards Drill bits for CNC drilling machines can be divided into medical twist drills, fixed-hand twist drills and fixed-handle drill bits. Straight shank twist drills are mostly used in single-head drilling machines, which are used to drill simpler printed boards or single-panels with a drilling depth of up to 10 times the diameter of the drill. In the case where the substrate stack is not high, the drill sleeve can be used to avoid the drill deviation.
The material of the drill bit: the drill bit for the printed board is generally made of cemented carbide, because the epoxy glass cloth has a particularly fast wear on the tool. The cemented carbide is made of tungsten carbide powder as a matrix and pressed and sintered with cobalt powder as a binder. It usually contains 94% tungsten carbide and 6% cobalt. Due to its high hardness, it is very wear-resistant and has a certain strength, suitable for high-speed cutting. However, the toughness is very poor, and it is very brittle. Some use ion implantation technology to inject titanium, nitrogen, and carbon into the depth of the substrate, which not only improves the hardness and strength, but also injects the components during the regrind. There is also a physical method of forming a diamond film on the top of the drill bit, which greatly improves the hardness and wear resistance of the drill bit. The hardness and strength of cemented carbides are not only related to the ratio of tungsten carbide to cobalt, but also to the particles of the powder. The ultrafine particle cemented carbide drill has an average grain size of tungsten carbide phase of 1 micron or less. This kind of drill bit not only has high hardness but also improved compression resistance and bending strength. In order to save cost, many drill bits now use a welded shank structure. The original drill bit is made of cemented carbide as a whole, and now the rear shank is made of stainless steel. Greatly reduced, but due to the different materials, its dynamic concentricity is not as good as that of solid carbide drills, especially in small diameters.
Post time: Oct-18-2019