**How to Print Punching Holes on the Circuit Board**

Punching a hole in a printed circuit board is a mechanical process similar to drilling. However, it typically does not achieve the same level of accuracy in hole diameter, wall smoothness, or prevention of delamination between the land and the substrate. Generally, larger holes are easier to punch than smaller ones. For instance, on reinforced paper substrates, holes smaller than 0.9mm and on reinforced glass cloth substrates, holes smaller than 1.2mm often result in punching failures.

Consequently, the load of the automatic punching machine is influenced by the type of substrate and the required cutting force. The cutting force for paper substrates is around 1200 psi, whereas for epoxy glass substrates, it is approximately 20,000 psi. This means that a paper substrate must endure a pressure of 16 tons. To enhance the performance, a withstand pressure of 32 tons is frequently employed.

Epoxy glass substrates exhibit 70% greater compression resistance compared to paper phenyl ester substrates, making high compression resistance essential even for basic boards. When using an automatic punching machine, the edges of the copper foil tend to lift. Consequently, it’s not advisable to have circuits on both sides of the board, as this can lead to pad detachment.

Furthermore, if the spacing between holes is too small, cracks may develop. In such cases, it’s important to adjust the operating procedure by refraining from etching the copper foil before punching. This allows the copper foil to provide structural support and helps prevent cracks. This approach is commonly applied in high-volume consumer printed circuit board products, which utilize both paper phenyl ester and epoxy-based substrates.

Another drawback of punching is the potential for pad delamination and substrate breakage at the connection holes. Additionally, the punching process can result in conical holes with thick surfaces. Therefore, printed circuit boards that do not adhere to professional standards require stricter smoothness criteria for the plated through-hole surfaces.

To achieve precise processing, there must be a specific tolerance between the drilling machine and the punching hole. Generally, for paper substrates, the punching hole should be 0.002 to 0.004 inches larger than the drilling machine, while for glass substrates, this tolerance should be halved. Figure 10-2 illustrates the differences between the drilling machine and punching hole, along with examples of the required tolerances.

For paper benzoic substrates (XXX and similar types), to prevent chipping, the temperature should be pre-heated to 50-70°C prior to punching. Substrates such as XXXPC and FR-2 can be punched at room temperature, provided the temperature exceeds 20°C. Non-woven reinforced glass substrates (epoxy and polyester) exhibit excellent punching performance, achieving a smooth hole wall suitable for electroplating with a die gap of 50-100μm.

**Tips for Operating an Environmentally Friendly Circuit Board Shredder**

The circuit board shredder produced by the PCB factory represents some of the most advanced equipment available in China. This series of shredders combines the advantages of multiple shredders, utilizing principles of impact, shear, high-speed impact, and mutual grinding for optimal performance.

**Operating Procedures for the Circuit Board Shredder:**

To enhance the efficiency, speed, and safety of the circuit board shredder, consider the following tips:

1. Aim to use the same type of materials whenever possible. For instance, when shredding wood, consistently shred only wood. If shredding cans, only shred cans. This ensures the shredder operates effectively and produces uniform shredded products, while also protecting the shredder itself.

2. Preheat and idle the PCB shredder before starting. Many overlook this step, but preheating and idling significantly improve operational efficiency and extend the shredder’s lifespan.

3. After shredding, ensure all material is completely discharged before turning off the machine.

4. Maintain proper lubrication of the shredder. This not only increases output and production capacity but also contributes to a longer service life for the equipment.
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