Analysis of the Causes of Printed Circuit Board Drilling Exceeding Tolerance

Printed circuit board drilling exceeding tolerance refers to the deviation of drilling size from actual requirements. There are many factors that can cause drilling deviation, such as materials, drill bits, aluminum sheets, and pads, which can all affect the accuracy of drilling.

1.Materials

Different circuit board materials have a significant impact on the wear of the drilling nozzle, usually according to ordinary double-sided boards (four pieces per stack), 2500-3000 holes can be drilled; 500 holes can be drilled on high-density multi-layer boards; For FR-4 (three blocks per stack), 2500 holes can be drilled; For harder FR-4 high Tg materials, the average parameter reduction is 30-40%. If Tg is high, the modulus is high, the rigidity is good, the warpage is small, but the brittleness is large, and the wear of the drill tip will increase. Improper control and excessive wear of the drilling nozzle can lead to hole deviation and rough hole walls, and in severe cases, the plate may burst.

The influence of copper thickness, board thickness, and glass yarn on drilling of circuit boards: Cutting too thick copper into wire shapes affects the discharge of cutting materials and the roughness of hole walls. Glass yarn is the main factor affecting the wear of the drill bit, and excessively worn drill bits will inevitably affect the occurrence of hole deviation. The thicker the plate, the more severe the wear, so the re grinding of the drill bit will be particularly important.

2.Aluminum sheet

Drilled aluminum sheets for circuit boards are usually around 0.17mm thick, with a certain surface hardness to prevent burrs on the surface of the drilled holes; It also requires a certain degree of elasticity, which immediately deforms when the drill bit comes into contact with the drill bit, allowing the drill bit to accurately align with the position being drilled, ensuring the accuracy of the drilling position. The wrinkling of aluminum sheets and the inclusion between aluminum sheets and circuit boards can affect the adhesion and bonding between aluminum sheets and circuit board surfaces, resulting in burrs. Once burrs are generated, the raised burrs lift the aluminum sheets, separating them from the board, and causing the burrs to develop towards the surrounding area. This is the automatic diffusion of burrs. Once the burrs diffuse, the dust particles mixed between the plate and the aluminum sheet during chip removal will force the drilling nozzle to change the drilling position, ultimately causing deviation and breakage of the drilling nozzle.

3.Base plate

The commonly used drilling pad for circuit boards on FR-4 materials is traditional solid pulp board, which can be divided into medium density and high density. A good pad can avoid excessive wear of the drill blade, as the drill tip rotates and rubs at high speed in the pad, causing the drill blade to wear out. If impurities are present in the pad, it will accelerate the wear of the drill blade. Having a good surface hardness, flatness, and minimal impurities are the basic requirements for backing plates.

4.Drill bit

Improper selection of drill bits is also a reason for exceeding the tolerance of printed circuit board drilling. The material, diameter, sharp angle, cutting groove and other factors of the drill bit will directly affect the drilling quality. If the wrong drill bit is selected, it is easy for the drilling to exceed the tolerance.

In addition, improper control of the drilling process can also lead to printed circuit board drilling exceeding tolerances. The drilling process requires strict control of factors such as rotational speed, feed speed, and cutting lubrication. If these factors are not adjusted reasonably, they will have a negative impact on the quality of drilling, leading to situations of exceeding tolerances.

Sihui Fuji continuously strengthens control measures from the five dimensions of human, machine, material, method, and environment (5M), including personnel, machines, materials, drilling parameters, methods, temperature, humidity, voltage, and other factors, to ensure that the drilled products meet customer requirements.