PCB drilling: the main reason and the preventive measures of the drill hole

- Nov 03, 2018-

Role of aluminum sheet:

1. Prevent the surface of PCB from burr and scratch.

2. Heat dissipation and bit cleaning.

3. It can guide the drill bit into the track of PCB board to improve the drilling accuracy.

Aluminum sheets require high thermal conductivity, which can quickly remove the heat generated during drilling and reduce the temperature of the drill nozzle. Aluminum sheets of 0.15-0.2mm thick or composite aluminum alloy sheets of 0.15-0.35mm should be used as far as possible to effectively prevent the failure of the drill nozzle caused by the high temperature during drilling.

3. The quality of the copper-clad sheet material is thick, and the bonding strength is not good, which will also have a great influence on the cutting tip.If the plate resin polymerization is not complete, it is easy to produce the hole wall glue dregs, poor chip removal and drilling.If there are holes in the substrates, the drill heads will break under uneven force during drilling.Therefore, the sheet must be baked before drilling.The baking time is generally 4 hours /150oC plus or minus 5oC

4. When using the drill mouth, the drill mouth of different types of functions must be selected according to the processing purpose and product hole wall quality requirements.The main categories of drillers are 1: ST type (straight drill) 2: under cut drill 3:ID type (inverse drill) 3. Currently, the most commonly used type is ST type, which is suitable for double-panel panels with sheet materials such as paper, epoxy paper, phenol epoxy glass and PCB boards below four layers.The characteristic of UC type drill nozzle is that the diameter below the tip is smaller than the diameter above the head (that is, the head is large and the body is small). The design principle is to reduce the friction with the hole wall in the drilling process, and prevent the hole wall from being too thick and broken needle.It is very important to choose a timely supplier with stable quality and perfect after-sales service.

5. The performance of the machine must be kept in a stable and good precision state during the drilling process.Due to the vibration of the drill press, vibration of the spindle and RUNOUT are too large, the COLLET design is poor or there is debris, the z-axis is not moving or dusting is not good, and (X, Y) the shaft is not moving well, which leads to the broken tip. Therefore, the drilling rig with good performance should be selected according to the PCB plant's own customer group and product structure.Under normal circumstances, the height difference between the highest and the lowest level of the machine platform is required to be <0.125mm, and the moving accuracy deviation of X and Y axes is <0.076mm.

SPINDLE dynamic RUNOUT<2.5um. Compression temperature = room temperature.Dew point =3oC, oil residue is no more than 0.01mg/m3, solid residue is no more than 0.1um(otherwise, water and oil inside SPINDLE will affect the SPINDLE life and drilling accuracy), and the dust absorption force is within the range of 100-150mbar.The pressure of the pressure foot should be 21-24N/CM2.The pressure pin of each drill shaft shall be adjusted to about 1.3mm longer than the drill nozzle.When drilling, press the pad to press the aluminum sheet before drilling in. When the drill tip is lifted, press the pad to leave the plate, otherwise it is easy to break the drill tip.The precision of nc drilling is tested and compared regularly.

6. The working environment has high requirements on 5S in the production workshop to reduce the existence of dust.Machine marble mesa, cross beam daily maintenance should be scrubbed with alcohol.Keep it clean.The temperature in the operation room is controlled between 20oC and + 2oC to ensure that the machine works in an appropriate environment and the quality is ensured while the life of the CNC drill is ensured.