Various Types of "Holes" in PCBs
There are various types and functions of holes in PCBs, and the following is a detailed description of these holes:
A buried hole is a special type of hole that connects wires between the inner layers of a PCB and is therefore not visible from the surface of the PCB. Unlike blind vias, buried vias are types of vias that are not visible from the surface of the PCB.
In a multi-layer PCB, if only the wires between the inner layers need to be connected, then the vias may waste the space of the wires in other layers. The buried hole technique avoids this problem because it only penetrates a few of the layers, thus saving space and increasing the board's routing density.
In PCB design, the application of buried vias requires attention to some details. First, you need to choose the appropriate hole diameter and depth to meet the circuit board design requirements and processing technology. Secondly, the location of buried holes also needs to be determined according to the overall layout and wiring requirements of the circuit board to ensure the reliability of electrical performance and mechanical strength.
Vias are mainly used to connect the conductive lines of different layers to realize the electrical connection between the inner layer, outer layer or inner and outer layers. According to its role, vias can be divided into two categories: through holes and blind holes. Through holes extend through the entire PCB and are used to realize inner layer connections and/or component positioning and mounting, etc. Blind vias extend only to one layer of the PCB and are used to connect wires and reinforcement materials on a specific layer. The surface of the vias can be windowed (pads exposed), oil-covered or plugged.
Plug-in holes (Pad holes)
Plug-in holes are required to insert the pin holes for device soldering, and the pad surface must be exposed. These holes are used to insert the component pins, and soldering, thereby realizing the electrical connection between the component and the PCB. Plug-in holes come in different shapes and sizes to accommodate different component pins.
Copper-free mounting holes (Npth)
Copper-free mounting holes are mainly used for fixing components or devices with no electrical properties to act as a locating fixing. These holes are typically used for mounting screws or plastic retaining feet for devices. Copper-free mounting holes are designed to increase the mechanical strength and stability of the PCB.
Slot Holes (Long Holes)
Slotted holes are usually used to fulfill a specific mounting or fixing function. For example, long strip holes are mainly used for fixing or conduction, depending on the specific application scenario.
A common type of through-hole in PCB design, it runs through the entire PCB and is used to realize electrical connections between inner layers. Through holes are relatively simple to produce and low cost, so they are widely used in multilayer PCBs. The diameter of the through-hole is generally larger than the diameter of the plug pins, and leave a certain margin to adapt to different processing and manufacturing requirements.
Through-hole design requires attention to some details. First, the diameter and shape of the through-hole need to be selected according to the actual situation, in order to meet the circuit board wiring and component installation requirements. Secondly, the pad design of the through-hole is also very important, which realizes the electrical connection between the plated inner layer of the through-hole and the surface or internal alignment of the printed circuit board. The size and shape of the pads need to be determined based on the diameter of the through-hole and the overall design of the board.
The use of through-holes in PCB design can offer several advantages. First, through-holes can provide a better electrical connection to achieve stable conduction between inner layers. Secondly, through-holes can play a role in fixing components, improving the mechanical strength and stability of the circuit board. In addition, through-holes can provide better heat dissipation, helping to reduce the temperature of the circuit board.
Blind vias are through-holes that connect the surface layer to the inner layer without penetrating the entire board, and are usually located on the top and bottom surfaces of the printed circuit board, with a certain depth, for the connection of the surface layer lines and the inner layer lines below. The depth of the vias usually does not exceed a certain ratio (aperture diameter). Blind vias are designed to reduce the size of the board and can increase the wiring density of the board. In multilayer PCBs, the use of blind vias reduces the number of connections between inner layers, simplifies the fabrication process, and improves board reliability.
A hole that has one side on the surface of the board and then passes through to the inside of the board. A blind via is a hole that connects a surface layer to an inner layer without going through the entire board. Blind vias are vias that connect the inner layers and are not visible on the surface of the finished board.
In PCB design, blind vias are relatively complex and costly to produce, so they are only used in some special applications. The design of blind holes requires attention to a number of details, such as hole diameter, hole depth, location and other parameters of the choice to meet the circuit board design requirements and processing technology.
In addition to the holes described above, there are other types of holes in PCBs, such as metal half-holes and stamp holes. These holes vary according to actual needs and design requirements.
In PCB design, it is very important to choose the right type and specification of holes because they affect aspects such as the electrical performance, mechanical strength and reliability of the board. At the same time, parameters such as the pitch, diameter and depth of the holes need to be considered in the fabrication process to meet the requirements of the production process.
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