1. Types of PCBs
According to the number of circuit layers, PCBs can be classified into single-sided boards, double-sided boards, and multi-layer boards. Common multi-layer boards typically have 4 or 6 layers, while complex multi-layer boards can have dozens of layers. The following are the three main types of PCBs:
1. Single-Sided Boards
Single-sided boards (Single-Sided Boards) have components concentrated on one side, while the traces are concentrated on the other side (with surface mount components on the same side as traces and through-hole components on the opposite side). Because traces appear only on one side, this type of PCB is called single-sided. Due to the strict limitations in designing traces (as they cannot cross and must take separate paths), this type of board is only used in early circuits.
2. Double-Sided Boards
Double-sided boards (Double-Sided Boards) have traces on both sides. However, to utilize traces on both sides, there must be appropriate electrical connections between the two sides. These connections are called vias. Vias are small holes filled or coated with metal on the PCB, allowing connections between traces on both sides. Since double-sided boards have double the area of single-sided boards, they solve the wiring crossover issues found in single-sided boards (as traces can pass through vias to the other side), making them more suitable for more complex circuits than single-sided boards.
3. Multi-Layer Boards
Multi-layer boards (Multi-layer Boards) increase the wiring area by using more single or double-sided boards. A four-layer or six-layer PCB can be created using one double-sided board as an inner layer and two single-sided boards as outer layers, or two double-sided boards as inner layers and two single-sided boards as outer layers. These printed circuit boards are interconnected according to design requirements using positioning systems and insulating bonding materials. The number of layers does not represent the number of independent wiring layers; in special cases, empty layers may be added to control board thickness, and the number of layers is usually even, including the two outermost layers. Most motherboards are structured with 4 to 8 layers, but theoretically, PCBs can reach nearly 100 layers. Large supercomputers often use highly layered motherboards, but since such computers can now be replaced by clusters of many ordinary computers, ultra-multi-layer boards are gradually falling out of use. Since all layers in a PCB are tightly bonded, it is generally not easy to determine the actual number of layers, but if you closely observe a motherboard, you can still see it.
2. Important Factors to Consider When Selecting PCB Design for 1-20 Layers
Let’s start with considerations. You may have some understanding of the number of layers required for a PCB. However, you need to check why multi-layer PCBs are more ideal than single-layer PCBs. Focusing on the following points can alleviate your confusion:
· Purpose: Where will the PCB be used? As mentioned earlier, PCBs are used in various types of electronic devices, from simple to complex. Therefore, it is essential to clarify whether your application has minimal functionality or complex functionality.
· Required Signal Types: Did you know that printed circuit boards are also used in microwave applications? The choice of layers also depends on the types of signals they need to transmit. Signals can be categorized into high frequency, low frequency, ground, or power. For applications requiring multiple signal processing, you will need multi-layer PCBs. These circuits may require different grounding and isolation.
· Type of Vias: The choice of vias is another important factor to consider. If you choose buried vias, you may need more internal layers. Therefore, you can meet multi-layer requirements accordingly.
· Density and Number of Required Signal Layers: The determination of PCB layers is also based on two important factors – signal layers and pin density. The number of layers in a PCB increases as pin density decreases. For example, a pin density of 1.0 will require 2 signal layers. However, a pin density of <0.2 may require 10 layers or more.
· Number of Required Planes: Power and ground planes in a PCB help reduce EMI and shield signal layers. Therefore, the choice of layers will again depend on the number of required planes.
· Manufacturing Cost: Although it is a primary requirement, it is one of the deciding factors in selecting the number of layers in a 1-20 layer PCB design. The cost of manufacturing PCBs depends on the number of layers. Multi-layer PCBs are more expensive than single-layer PCBs. Manufacturing costs will largely depend on the above requirements.
· Delivery Time: The delivery time for a 1-20 layer PCB design depends on all the above factors. For example, if your design requires a single layer, the lead time may be shorter. If you order PCBs for complex industrial electronic devices, the delivery time will increase.
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