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Common PCB Drilling Process Faults and Solutions

PCB Drilling Process

PCB Drilling Process

In the PCB manufacturing process, drilling is a critical step that requires precision and accuracy. However, several issues can arise during drilling, leading to defects in the final PCB. This article discusses common PCB drilling process faults, their causes, and solutions to ensure a smooth and efficient drilling process.

1. Drill Bit Breakage

Causes:

  • Excessive spindle deflection.
  • Improper operation during drilling.
  • Inappropriate drill bit selection.
  • Insufficient drill speed, excessive feed rate.
  • Excessive number of stacked boards.
  • Presence of debris under the board or between the boards.

Solutions:

  1. Inform the technician to inspect and repair the spindle or replace it with a new one.
  2. Check the geometry, wear, and use appropriate drill bits with suitable chip flute lengths.
  3. Choose the correct feed rate and reduce the drilling speed.
  4. Reduce the number of stacked boards to an appropriate level.
  5. Clean the board surface and remove any debris under or between the boards.
  6. Adjust the spindle depth during drilling to ensure proper chip removal.
  7. Control the number of sharpening operations according to the operation manual or parameters.
  8. Select cover and spacer boards with appropriate hardness and flatness.
  9. Check the tape fixing status and width, and replace the cover board aluminum sheet if necessary.
  10. Reduce the feed rate appropriately.
  11. Pay attention to correct hole filling during operation.
  12. Replace drill bits with the same center.

2. Hole Damage

Causes:

  • Taking out the drill bit after breakage.
  • Drilling without an aluminum sheet or reverse bottom plate.
  • Incorrect parameters.
  • Drill bit elongation.
  • Insufficient effective length of the drill bit for the board thickness.
  • Manual hole drilling.
  • Special board material causing burrs.

Solutions:

  1. Identify and address the root cause of the drill breakage as per the previous point.
  2. Aluminum sheets and bottom plates serve to protect the hole ring. Always use them, and check their placement and direction before boarding.
  3. Before drilling, check if the hole depth matches the parameters, and ensure that each drill bit is correctly set.
  4. Check the drill bit length visually before boarding and ensure it meets the production board’s stack measurement requirements.
  5. Manual drilling is prohibited, as it does not meet the requirements for accuracy, speed, etc.
  6. Select parameters appropriately for special board materials and ensure that the drill speed is suitable.

3. Hole Misalignment

Causes:

  • Drill bit deviation during drilling.
  • Improper selection of cover board material, hardness, or flatness.
  • Expansion and contraction of the substrate causing hole deviation.
  • Improper use of fitting and positioning tools.
  • Improper setting of the pressure foot during drilling, hitting the positioning pin, causing the production board to move.

Solutions:

  • A, Check if the spindle is deflected. B, Reduce the number of stacked boards, usually to 6 times the drill diameter for double-sided boards and 2-3 times for multilayer boards. C, Increase drill speed or reduce feed rate. D, Check if the drill bit meets the process requirements, and grind it if necessary. E, Check the concentricity between the drill bit tip and the drill bit handle. F, Check the fixing status between the drill bit and the spring chuck, and adjust or replace the spring chuck if necessary. G, Check and correct the stability and flatness of the workbench.
  • Choose a cover board with a density of 0.50mm or replace it with a composite cover board material (two layers of aluminum foil with a thickness of 0.06mm on the top and bottom, and a fiber core in the middle, with a total thickness of 0.35mm).
  • According to the characteristics of the board, perform pre- or post-drilling plate baking treatment (usually at 145C + 5C, baking for 4 hours).
  • Check or test the tool hole size accuracy and the position of the positioning pin.
  • Check and reset the pressure foot height. The normal pressure foot height is 0.80mm from the board surface.
  • Choose the appropriate drill speed. Clean or replace the spring chuck.
  • The board is not fitted with positioning pins, the control board’s pins are too low or loose, and the pins need to be repositioned and replaced.
  • Select an appropriate feed rate or a drill bit with better bending strength.
  • Replace the cover board aluminum sheet with a smooth and uncracked surface.
  • Operate the hole filling correctly during operation.
  • Record and verify the origin.
  • Stick the adhesive paper at a 90-degree angle to the board edge.
  • Feedback and inform the technician to adjust and repair the drilling machine.
  • Check and verify, and inform the engineering department to make modifications.

Conclusion

In conclusion, PCB drilling process faults can lead to significant defects and impact the overall quality of the PCB. By understanding the causes of these faults and implementing appropriate solutions, manufacturers can ensure a smooth and efficient drilling process, ultimately leading to high-quality PCBs. Regular maintenance of drilling machines, proper selection of drill bits, and adherence to drilling parameters are key factors in preventing these faults and ensuring the reliability of the final PCB product.

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