PCB drilling: the main reasons and preventive measures for breaking the drill nozzle
1. Drilling parameters:
The setting of drilling parameters is very important. The drilling speed is too fast. It is broken when the drilling nozzle is too strong. The drilling speed is too slow, which will reduce the production efficiency. Because the board thickness, copper thickness, and sheet structure of the PCB boards produced by each sheet material manufacturer are different, the PCB needs to be set according to the specific conditions. Through calculation and testing, choose the most suitable drilling parameters. Generally, if the drill is 0.3mm, the lower cutting speed should be 1.5-1.7m/min, and the drilling depth should be controlled between 0.5-0.8.
2. The pad for drilling the aluminum plate and the aluminum plate requires moderate hardness, uniform thickness, flatness and thickness difference should not exceed 0.076mm.
If the soft and hard distribution of the pad is irregular, it is easy to get stuck in the drill, and the pad is not smooth. The pressure on the foot will not be tight, the drill will be twisted and broken, and the plate will move along with the drill during the up and down movement. The drill will be broken due to the unbalanced force during the returning process.
(1) The occurrence of burrs in the pores is suppressed.
(2) Fully penetrate the PCB board.
(3) Reduce the temperature of the nozzle edge and reduce the broken drill.
The aluminum sheet for drilling must have a certain rigidity to prevent the sheet from vibrating when the knife is lifted, and it needs to have corresponding elasticity. The drill tip softens immediately at the moment of the drill-down contact, and the drill tip is precisely aligned with the drilled position, so that the drill tip does not deviate from the original hole position, resulting in a broken drill nozzle.
The role of aluminum sheet:
1. Prevent burrs and scratches on the surface of the PCB.
2, from the heat dissipation and bit cleaning.
3. The drill bit can be guided into the track of the PCB to improve the accuracy of the drilling.
The aluminum sheet requires a large thermal conductivity, so that the heat generated during drilling can be quickly taken away and the temperature of the drill tip can be lowered. The aluminum sheet of 0.15-0.2 mm thickness or the aluminum alloy composite sheet of 0.15-0.35 mm should be used as much as possible. Prevent the drill bit from being broken due to the high temperature of the drill hole caused by the high temperature during drilling.
3, the quality of copper-clad sheet material The fiberglass cloth of the sheet material is thick,
the bonding strength is not good, it will have a greater impact on the broken drill bit. If the resin of the sheet resin is not completely polymerized, it is easy to produce a large amount of hole wall glue, and the chip discharge is bad and the drill bit is broken. If there is a cavity in the substrate, the drill will be broken due to uneven force during drilling. Therefore, the sheet must be baked before drilling. Baking time is generally 4 hours / 150oC ± 5oC
4. Drilling nozzle When using the drill nozzle,
the drill head of different types of functions must be selected according to the purpose of processing, the quality requirements of the product hole wall, and the purpose. The main types of drills are 1: ST type (straight drill) 2: UC type (under cut drill) 3: ID type (inverse drill), the most commonly used type is ST type, suitable for containing paper, epoxy paper, phenol. Double-panel and non-four-layer PCB boards for sheets such as epoxy glass. The UC type drill tip is characterized in that the diameter below the tip is smaller than the diameter above the head (that is, the head is large and small). The design principle is to reduce the friction with the hole wall during the drilling process, and prevent the hole wall from being too thick and broken. needle. It is very important to choose a supplier with timely delivery, stable quality and perfect after-sales service.
5, machine performance In the drilling production process must ensure that the rig is in a stable and accurate state.
Due to the vibration of the drilling machine, the vibration of the main shaft and the large RUNOUT, the COLLET design is poor or there are debris, the Z-axis is not moving, the dust removal is not good, and the (X, Y) axis movement is bad, which leads to the broken drill nozzle, so it depends on the PCB. The board’s own customer base and product structure are chosen to use well-performing rigs. Under normal circumstances, the difference between the highest and lowest height of the flatness of the machine is <0.125mm, and the deviation accuracy of the X and Y axes is <0.076mm.
SPINDLE dynamic RUNOUT < 2. 5um. compressed gas temperature = room temperature. Dew point = 3oC, oil residue ≤ 0.01mg / m3, solid residue ≤ 0.1um (otherwise, causing water in SPINDLE oil, affecting SPINDLE life and drilling accuracy), vacuuming force within 100-150Mbar range. The pressure of the pressure foot should be 21-24N/CM2. The presser foot of each drill shaft should be adjusted to be about 1.3 mm longer than the drill. When drilling, the pressure pad will press the aluminum piece before it is drilled. When the hole is retracted, the pressure pad will leave the plate, otherwise the drill will be easily broken. And the accuracy of CNC drilling is checked and adjusted regularly.
6. Working environment The requirements for 5S in the production workshop are high, and dust is reduced.
Machine marble countertops, beams should be scrubbed with alcohol. keep clean. The operating room temperature is controlled between 20oC ± 2oC, ensuring that the machine works in an adapted environment, ensuring quality while ensuring the life of the CNC rig.