PCB drilling: the main causes and preventive measures of drill break

- Jul 26, 2018-

1. Drilling parameters: the setting of drilling parameters is crucial. Too fast drilling speed means that the drill nozzle is under too much force and breaks off. Too slow drilling speed will reduce production efficiency.

As the thickness, copper thickness and structure of PCB boards produced by various plate manufacturers are different, PCB shall be set according to specific conditions.

Select the most suitable drilling parameters through calculation and testing.

Generally, if the drill bit is 0.3mm, the cutting speed should be 1.5-1.7m/min, and the drilling depth should be controlled between 0.5-0.8.

2, plate, aluminum plate requirements of drilling with moderate hardness, thickness, level off, should not be more than 0.076 mm thick, such as plate soft hard irregular distribution is easy to get stuck drill tsui, plate is not smooth, can make the pressure at the foot of pressure is not sealed, is broken, twisting drill tsui and drill tip in medium plate up and down movement process will follow sports, drill tip in his knife back with the unbalanced force and broken, the role of:

(1) inhibit the occurrence of burrs in the hole.

(2) fully penetrate the PCB board.

(3) lower the temperature of the drill nozzle blade and reduce the drilling break.

The aluminum sheet used for drilling should be rigid to prevent the plate from vibrating when lifting the knife, and should have the corresponding flexibility.

The drill nozzle becomes soft immediately at the moment when the drill is in contact with the drill. It is precisely aimed at the position where the drill nozzle is drilled.

Functions of aluminum sheet:

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

2. It plays the role of heat dissipation and bit cleaning.

3. The drill can be guided into the track of PCB board to improve the accuracy of drilling.

The thermal conductivity of aluminum sheet is required to be large, so that the heat generated during drilling can be taken away quickly and the temperature of drill nozzle can be reduced. The aluminum sheet with a thickness of 0.15-0.2mm or the aluminum alloy composite sheet with a thickness of 0.15-0.35mm should be used as far as possible to effectively prevent the bad chip discharge caused by the high temperature during drilling.

3. The quality glass fiber cloth of the copper clad laminate is coarse, and the poor binding force will also have a great impact on the fracture tip.

If the sheet resin polymerization is not complete, it is easy to produce a lot of hole wall glue slag, poor chip removal and drilling nozzle.

If there is a hole in the substrate, the drill nozzle will break off unevenly when drilling.

Therefore, the plate must be baked before drilling.

The baking time is generally 4 hours /150oC + / + 5oC

4. When using the drill nozzle, different types of functional drill nozzle must be selected according to the processing purpose, the quality requirements of the product bore wall and the purpose.

The main types of drill nozzles are: ST type (straight drill) 2:UC type (under cut drill) 3: inverse-drill. Currently, the most commonly used type is ST type, which is suitable for double-panel and four-layer PCB plates containing paper, epoxy paper, phenol epoxy glass and other materials.

The characteristic of UC type drill nozzle is that the diameter below the tip is smaller than that above the head (that is, the head is smaller than the body). The design principle is to reduce the friction with the hole wall during drilling and prevent the hole wall from being too thick and the needle from breaking.

It is very important to choose a supplier with timely supply, stable quality and perfect after-sales service.

5. The machine performance must ensure that the drilling machine is in a stable and accurate state during drilling production.

Due to the vibration of drill bed, vibration of main shaft and large RUNOUT, poor COLLET design or sundries, poor z-axis cavitation and dust removal, poor (X, Y) axis movement, etc. all lead to drill breakage tip, so the drilling rig with good performance should be selected according to the customer group and product structure of PCB board factory.

Under normal circumstances, the difference between the highest and lowest height of the platform flatness is required to be <0.125mm, and the deviation of X and Y axis movement precision is <0.076mm.

SPINDLE dynamic RUNOUT<2.

5um. Compression temperature = room temperature.

Dew point =3oC, oil residue less than or equal to 0.01mg/m3, solid residue less than or equal to 0.1um(otherwise, there is water and oil in SPINDLE, which affects the life and drilling accuracy of SPINDLE), and the dust absorption force is within the range of 100-150 mbar.

The pressure at the pressure foot should be between 21 and 24N/CM2.

The pressure foot of each drill shaft should be adjusted to about 1.3mm longer than the drill nozzle.

When drilling, the pressure pad presses the aluminum sheet before drilling in. When returning the knife, the pressure pad leaves the board after the drill nozzle is lifted up, otherwise, it is easy to break the drill nozzle.

The precision of nc drilling is measured and adjusted regularly.

6. The operating environment has high requirements for 5S in the production workshop, so as to reduce dust.

Machine marble countertop, beam day maintenance to use alcohol scrub.

Keep it clean.

The operating room temperature is controlled between 20oC plus or minus 2oC, so as to ensure that the machine works in the suitable environment and guarantee the quality while ensuring the life of the CNC drill.