PCB Blog - How to cut a circuit board?

Circuit board cutting refers to dividing a circuit board into two or several pieces according to a reasonable circuit without affecting its effectiveness. PCB cutting is usually carried out using a PCB cutting machine.

How to cut a circuit board?

1.Linear cutting (V-cutting): This is the most common cutting method. By using cutting tools or V-knives, perform straight cuts along the edges of the PCB board or specified cutting lines to achieve the desired size and shape.

2.Milling and cutting: For PCB boards that require more precise shapes and hole positions, CNC milling machines are often used for milling and cutting. According to the design documents, use a rotating tool to remove excess material from the PCB board to achieve the desired shape and size.

3.Wire cutting: Some complex PCB boards may require internal or complex curve cutting. At this point, wire-cutting technology can be used to cut PCB boards along a predetermined path using a high-speed fine wire-cutting machine. Wire cutting can achieve high accuracy and complexity.

4. Laser cutting: Laser cutting is a non-contact cutting technology that can achieve high-precision and complex shape cutting. By utilizing the thermal energy of the laser beam, the material on the PCB board is evaporated or melted, thereby achieving the desired shape cutting.

V-Cut cutting method

V-cut is a set of dividing lines that are pre-cut using a rotary cutting tool at specific positions on the PCB according to the drawing requirements. Its purpose is to facilitate the subsequent assembly of SMT circuit boards for the De panel.

Mechanical Cutting

Cutting is the first step in the mechanical processing of printed circuit boards to give them their basic shape and contour. This basic cutting technique can be applied to a wide range of different substrates and is particularly suitable for boards up to 2 mm thick. When confronted with substrates thicker than 2 mm, the cut edges tend to be rough and uneven, so this method is usually not used.

Cutting of laminates can be done either manually or with the help of electro-mechanical equipment, and despite the different methods of operation, both have some commonalities. Cutting machines are usually equipped with a set of adjustable cutting blades, as shown in Figure 10-1, which are rectangular in shape, with an adjustable angle of about 7° at the bottom and a maximum cutting length of 1000 mm. When selecting the longitudinal angle between the two blades, an angle between 1° and 1.5° is generally recommended, while for epoxy glass substrates the maximum adjustment can be up to 4°. In addition, the gap between the cutting edges of the two blades should be less than 0.25 mm.

The angle between the blades needs to be adjusted appropriately for the thickness of the material to be cut. The thicker the material, the greater the angle required. If the cutting angle is too large or the gap between the blades is too wide, it may lead to cracking of the sheet when cutting paper substrates; and for epoxy glass substrates, although they have a certain degree of bending strength and are not prone to cracking, deformation may still occur. To maintain the neatness of the edges of the substrate during the cutting process, the material can be heated to between 30 and 100°C.

To ensure that the edges are cut neatly, the sheet needs to be firmly pressed by a spring mechanism to prevent it from shifting unnecessarily during the cutting process. In addition, visual errors can lead to tolerances of 0.3 to 0.5 millimeters, which should be minimized as much as possible, and cutting accuracy can be improved through the use of aids such as corner markers.

Cutting machines are capable of handling a wide range of sheet sizes and can provide accurate repeatable cut sizes. Large cutting machines can handle hundreds of kilograms of substrate per hour.

The reason why V-Cut needs to be designed on the circuit board is because the circuit board itself has a certain strength and hardness,The pre-cut V-Cut circuit facilitates the operator to smoothly cut the original panel into a single board.

Firstly, V-Cut can only cut straight lines, and it can only be cut to the bottom with one cut. That is to say, V-Cut can only be cut into a straight line from head to tail. It cannot turn or change direction, nor can it jump off a small section like a sewing line. This is because the grooves of V-Cut are cut using an electric saw with two discs on top and bottom, and because PCB cutting requires precision (measured in millimeters), it is not possible to operate cutting only half and then retracting the tool.

Secondly, if the PCB thickness is too thin, it is not suitable to make V-Cut grooves. Generally, if the thickness of the board is below 1.0mm, it is not recommended to make V-cut grooves because V-cut grooves will damage the structural strength of the original PCB. When heavy parts are placed on a board with a V-cut design, the board will become easily bent due to gravity, which is very unfavorable for SMT welding operations (easy to cause empty welding or short circuits).

In addition, when the PCB passes through the high temperature of the reflow furnace, the board itself will soften and deform due to the high temperature exceeding the glass transfer temperature (Tg). If the V-Cut position and groove depth are not designed properly, the deformation of the PCB will be more severe, which is not conducive to the secondary reflow process.

Stamp hole connection

Generally, PCBs are V-CUT, and stamp holes may only be used when encountering irregular or circular boards. The boards (or empty boards) are connected by stamp holes to provide support and prevent them from falling apart. If the mold is opened, it will not collapse. The most common way is to use them to create PCB-independent modules, such as Wi-Fi, Bluetooth, or core board modules, and then use them as independent components placed on another board during the PCB assembly process.

V-cutting is mainly used to divide entire PCB boards to improve efficiency and reduce costs in mass production.

Mechanical Cutout

Cutting of laminates can be done either manually or with the help of electro-mechanical equipment, and despite the different methods of operation, both have some commonalities. The cutter is usually equipped with a set of adjustable cutting blades, which are rectangular in shape, with an adjustable angle of about 7° at the bottom and a maximum cutting length of 1000 mm. When selecting the longitudinal angle between the two blades, an angle between 1° and 1.5° is generally recommended, while for epoxy glass substrates the maximum adjustment can be up to 4°. In addition, the gap between the cutting edges of the two blades should be less than 0.25 mm.

The angle between the blades needs to be adjusted appropriately for the thickness of the material to be cut. The thicker the material, the greater the angle required. If the cutting angle is too large or the gap between the blades is too wide, it may lead to cracking of the sheet when cutting paper substrates; and for epoxy glass substrates, although they have a certain degree of bending strength and are not prone to cracking, deformation may still occur. To maintain the neatness of the substrate edges during the cutting process, the material can be heated to between 30 and 100°C.

To ensure that the edges are cut neatly, the sheet needs to be firmly pressed by a spring mechanism to prevent it from shifting unnecessarily during the cutting process. In addition, visual errors can lead to tolerances of 0.3 to 0.5 millimeters, which should be minimized as much as possible, and cutting accuracy can be improved through the use of aids such as corner markers.

Cutting machines are capable of handling a wide range of sheet sizes and can provide accurate repeatable cut sizes. Large cutting machines can handle hundreds of kilograms of substrate per hour.

Circuit board cutting techniques are varied, and each method has its own application scenarios. Whether it's straight line cutting, milling, wire cutting or laser cutting, the key lies in choosing the right process to ensure the precise segmentation and functional integrity of the circuit board. As technology continues to advance, circuit board cutting will become more efficient and precise, continuing to meet the development needs of the electronics manufacturing industry.