1. Prevent burrs and scratches on the surface of the PCB board.

　　2. Plays a role in heat dissipation and cleaning the drill bit.

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

　　Aluminum sheets require a high thermal conductivity to quickly remove the heat generated during drilling and reduce the temperature of the drill bit. It is recommended to use aluminum sheets with a thickness of 0.15-0.2mm or aluminum alloy composite aluminum sheets with a thickness of 0.15-0.35mm to effectively prevent the drill bit from breaking due to poor chip removal caused by high temperatures during drilling.

　　3. The quality of copper-clad board material is that the fiberglass cloth of the board material is coarse, and the bonding force is not good, which can also have a significant impact on the broken drill bit. If the resin polymerization of the board is not complete, it is easy to produce a lot of adhesive residue on the hole wall, poor chip removal, and broken drill bits. If there are voids inside the substrate, it will cause the drilling nozzle to be subjected to uneven force during drilling and break. Therefore, the sheet material must be baked before drilling. The baking time is generally 4 hours/150oC ± 5oC