PCB drilling is a work of PCB plate making and a very important step. Mainly to punch the board, need to make a line, you need to make a hole, the structure needs, make a hole to do what; the multi-layer board punch is not finished once, some holes are buried in the circuit board, some are in The board was opened above, so there will be one drill and two drills.
PCB drill bits are mainly used in PCB manufacturing:
(PCB, Printed circuit board) printed circuit board,
It is composed of several layers of resin material bonded together, and the inside is made of copper foil. There are four, 6, and 8 layers.
Drilling accounts for 30-40% of the cost of printed circuit boards. Special equipment and drill bits are often required for mass production.
Good PCB drill bits are made of high quality hard alloy materials with superior rigidity, high hole position accuracy, good hole wall quality and long life.
PCB drill type
Types of drill bits for PCB drill bit controlled drilling machines: drills for printed board drilling include straight shank twist drills, fixed shank twist drills and fixed shank undercut drills. Straight shank twist drills are mostly used for single-head drilling machines, drilling simpler printed boards or single-sided boards, which are now rarely seen in large-scale circuit board manufacturers, and their drilling depth can reach 10 times the diameter of the drill bit. In the case where the substrate stack is not high, the use of the drill sleeve can avoid the deviation of the drill. At present, most manufacturers use CNC drilling machines. The CNC drilling machines use fixed shank drill bits with carbide, which is characterized by the ability to automatically replace the drill bits. High positioning accuracy, no need to use drill sleeve. Large helix angle, fast chip removal speed, suitable for high-speed cutting. Within the full 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. Common drill shank diameters are 3.00mm and 3.175mm.
PCB drill use:
The PCB drill is mainly used for PCB manufacturing: (PCB, Printed circuit board) printed circuit board, which is bonded together by several layers of resin materials, and uses copper foil wiring inside. There are 4, 6, and 8 floors. Drilling accounts for 30-40% of the cost of printed circuit boards, and mass production often requires special equipment and drill bits. Good PCB drills use good quality cemented carbide materials, with high rigidity, high hole accuracy, good hole wall quality, long life and other excellent characteristics.
PCB bit features
The raw materials of the products are cemented carbide rods and tungsten steel rods of international famous brands, which have high hardness, high wear resistance, high strength, resistance to bending, breakage and long tool life. (Complies with the EU “ROHS” environmental protection directive) Specifications: blade diameter 0.10mm to 6.50mm, shank diameter 3.175mm series of drills. (Special specifications can be customized)
① Large chip evacuation space: low chip evacuation resistance, smooth chip evacuation, small calorific value of drilling, reducing drilling pollution;
②Excellent cutting edge sharpness: due to the use of nanotechnology and advanced grinding technology, the cutting edge of the drill bit is sharper than before, which can reduce the cutting force, reduce the drilling break rate, and improve the quality of the hole wall; ③Tools based on customer applications Design: A variety of drill bits can meet different application needs. All parameters of the drill bit, such as core thickness, core taper, etc., have been carefully designed, and the actual effect is obvious; ④The cutting edge is strictly symmetrical: it is beneficial to efficient cutting and avoids drilling deviation.
PCB bit material
The drills used for the drilling of printed boards are generally made of cemented carbide, because the epoxy glass cloth composite copper foil board wears the tool particularly fast. The so-called cemented carbide is made of tungsten carbide powder as the matrix, with cobalt powder as a binder, which is pressed and sintered. Usually contains 94% tungsten carbide. Because of its high hardness, it is very wear-resistant and has a certain strength, suitable for high-speed cutting. But the toughness is poor and very brittle. In order to improve the performance of cemented carbide, some use chemical vapor deposition of a layer of 5-7 microns of ultra-hard titanium carbide (TIC) or titanium nitride (TIN) on the carbonized substrate to make it Has a higher hardness. Some use ion implantation technology to inject titanium, nitrogen, and carbon into their matrix to a certain depth, which not only improves the hardness and strength, but also migrates inwardly when the drill bit is reground. There is also a physical method to generate a layer of 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 carbide are not only related to the ratio of tungsten carbide, but also to the particles of the powder. The ultrafine particles of cemented carbide drills have an average size of tungsten carbide grains below 1 micron. This kind of drill has not only high hardness but also improved compressive and flexural strength. In order to save costs, many drill bits now use a welded shank structure. The original drill bit is made of cemented carbide. The rear drill shank uses stainless steel. The cost is greatly reduced. However, due to the different materials, its dynamic concentricity is not as good as the overall hard. Alloy drills, especially in small diameters.
- The drill bit should be packed in a special packaging box to avoid vibrations colliding with each other.
- When using it, remove the drill bit from the packaging box and install it in the spring collet of the spindle or in the tool magazine for automatic replacement of the drill bit. Put it back in the box immediately after use.
- Use a non-contact measuring instrument such as a tool microscope to measure the diameter of the drill bit to prevent the cutting edge from being damaged by contact with the mechanical measuring instrument.
- Some CNC drilling machines use a positioning ring. Some CNC drilling machines do not use a positioning ring. For example, the depth positioning when installing the positioning ring must be accurate. If the positioning bit is not used, the elongation of the drill bit to the main shaft must be adjusted. Consistent, multi-spindle drilling machines should pay more attention to this point, so that the drilling depth of each spindle should be consistent. If it is inconsistent, it may cause the drill bit to reach the table or fail to penetrate the circuit board and cause scrap.
- Normally you can use a 40x stereo microscope to check the wear of the cutting edge of the drill.
- Always check the concentricity of the spindle and the spring chuck and the clamping force of the spring chuck. If the concentricity is not good, it will cause the drill with a small diameter to break and the hole diameter is large. The poor clamping force will cause the actual speed and The set speed does not match, and the chuck and the drill bit slip.
- The fixed length of the fixed shank drill bit on the spring chuck is 4 to 5 times the diameter of the drill shank to be clamped firmly.
- Always check the spindle presser foot. The contact surface of the presser foot must be horizontal and vertical to the main shaft, and should not be shaken to prevent drill breakage and deviation holes in the drilling.
- The dust suction effect of the drilling machine is better. The dust suction air can reduce the temperature of the drill bit. Colleagues take away the dust to reduce friction and generate high temperature.
- The substrate stack including the upper and lower backing plates should be positioned and laid flat in a hole and slot positioning system on the workbench of the drilling machine. The use of adhesive tape should prevent the drill bit from sticking to the cutting tape on the tape, causing difficulty in chip removal and broken drill.
- When ordering the manufacturer’s drill bit, it is necessary to randomly check whether 4% of it conforms to the regulations when entering the factory. And 100% using 10 to 15 times microscope to check for notches, scratches and cracks.
- The drill bit is reground in time, which can increase the use and regrind times of the drill bit, extend the life of the drill bit, and reduce the production cost and expense. Usually measured with a tool microscope, within the full length of the two main cutting edges, the wear depth should be less than 0.2mm. When regrinding, it is necessary to grind off 0.25mm. Ordinary fixed shank drills can be regrinded 3 times, undercut The drill bit can be reground 2 times. Excessive re-grinding will reduce the quality and accuracy of drilling, which will result in the scrap of finished circuit boards. Excessive grinding effect is counterproductive.
- When the wear diameter is reduced by 2% compared with the original due to wear, the drill is scrapped.
- Setting of drill bit parameters Under normal circumstances, the manufacturer provides a parameter table of the rotation speed and lower speed of the drill hole produced by the factory. This parameter is only a reference. Actually, the technicians need to obtain a The actual speed and down speed parameters of the drill bit are usually different from the reference parameters but they will not differ too much.