4 Layer PCB Stack lp(
4 Layer PCB Stack Up
The number of layers of PCB is between 1 and 20, among which single-layer PCB has only one layer for placing circuit components and copper foil. Most common circuits can be laid out using single-layer PCB. Double-layer PCB adds a layer of copper foil on the basis of single-layer PCB, which is connected through through holes, making the plasticity of the circuit board further improved, and the price also increases accordingly. The higher the number of layers, the higher the price and the longer the production time. Today we mainly introduce 4 Layer PCB Stack Up.
-What is PCB Layer Stack Up
PCB layer stack up is a way to get multiple printed circuit boards in the same device by stacking them together while ensuring that there are predefined interconnections between them. Our team focuses on optimizing multi-layer stack up as it is one of the most important factors that determine the EMC performance of a product. For example, to improve the EMC performance of a 4-layer board, it is best to space the signal layers as close to the planes as possible and use large cores between the power and ground planes.
-How to stack up 4-layer PCB
1. SIG 01-GND 02-PWR 03-SIG 04
2. SIG 01-PWR 02-GND 03-SIG 04
3. PWR 01-SIG 02-GND 03-SIG 04
Scheme 1: Usually used when the main components are laid out on the top or the key signals are routed on the top, it can get better SI performance. It is not very good for EMI performance, but it can be controlled by routing and other details.
Scheme 2: Similar to scheme 1, it is suitable for the situation where the main components are laid out on the bottom layer or the key signals are routed on the bottom layer.
Scheme 3: Putting the power supply and ground planes on the top and bottom layers respectively can achieve a certain shielding effect. However, due to factors such as the power supply and the ground layer being too far apart and the component pads, the power supply layer and the ground layer lack effective coupling.
- The difference between 4 Layer PCB Stack Up and a common two-layer board
1. Compare Layers
The two-layer PCB stackup can be clearly marked: the bottom or top layer is described as the signal layer. The 0.0014-inch thick layer is made of copper material; the copper totals about 1 ounce. These parameters are valid for a circuit board with a final thickness of 0.062 inches (±10%). If the PCB manufacturer plans to manufacture custom PCBs, these values may vary depending on the required parameters.
On the other hand, the four-layer PCB stackup is very complex. Two inner layers, inner layers 1 and 2, are sandwiched between the top and bottom layers. From top to bottom.
The top, i.e., signal layer (0.0014-inch width), is followed by a prepreg with a thickness of 0.0091 inches and a dielectric constant of 4.2. The top layer is copper material. Following the prepreg layer is inner layer 1 (0.0014 inches), called a plane. The core sublayer is part of inner layer 1, which has a width of 0.037 inches. This is followed by Inner Layer 2, which is another plane layer made with 1 oz. copper and a thickness of 0.0014 inches. Another prepreg sublayer that makes up two sheets with a thickness of 0.0091 inches forms part of Inner Layer 2. The bottom layer is also 0.0014 inches thick and is also a signal layer. Interconnects are soldered and placed on the top and bottom layers.
2. Comparing Designs
The design of a two-layer PCB provides a larger surface area to accommodate conductor patterns. It is safe to say that its surface is twice that of a single-layer PCB. Vias are used to create electrical connections to enable routing of traces so that the traces reach the other side of the board.
On the other hand, as mentioned earlier, in a four-layer PCB design, more surface area is available for routing. Creating a four-layer PCB design involves a prepreg layer that bonds two or more two-layer boards by applying heat and pressure. The number of different conductor patterns produced is equal to the final number of layers. The prepreg also provides a dielectric between the layers.
3. Comparison of Functionality
If microstrip routing with a ground layer is used, a two-layer PCB will provide more functionality because there are no propagation delays or other issues. Nevertheless, a four-layer PCB design consisting of a ground layer and a VCC plane layer and two signal layers is preferable. However, this design does work on impedance and propagation delay.
4. Comparison of Cost
In terms of cost, it is not surprising that four-layer PCBs are more expensive due to the complexity of the design and higher sensitivity. The superior signal quality obtained by reducing distortion and propagation levels is also twice the cost of four-layer PCBs. More and more manufacturers are deciding to invest in four-layer PCBs due to higher signal integrity and lower interference levels.
5. Comparison of Prototyping
The challenge of getting a perfect PCB can be easily met through the prototyping process. Although a typical four-layer PCB prototype is a bit more complicated than a two-layer version, automated software such as Gerber can be used to help speed up prototype production. The software comes with many preset parameters such as board thickness, hole thickness, minimum spacing, board surface treatment, etc. Taking this approach can also simplify the creation of two-layer or four-layer custom PCBs.
-The Price of 4 Layer PCB
First of all, the price calculation of the four-layer board is mainly affected by the following factors: board material, board thickness, area, circuit complexity, production quantity, etc. Different choices will have an impact on the price.
First is the choice of board material. At present, the common four-layer board materials on the market are FR4, aluminum substrate, etc., and the prices of different materials vary greatly. FR4 is a common glass fiber reinforced material with a relatively low price. The aluminum substrate is a material with good heat dissipation performance and a relatively high price. Choosing the right board according to actual needs can reduce costs to a certain extent.
The second is the choice of board thickness. The board thickness of the four-layer board is generally between 0.8mm and 2.0mm, and different board thicknesses will also have a certain impact on the total price. Generally speaking, the price of thinner board thickness is relatively low, but the actual application needs and structural strength also need to be considered.
The third is the influence of area. The price of a four-layer board is proportional to the area. The larger the area, the higher the price. Therefore, when designing the circuit, you should arrange the component layout reasonably and try to reduce the area of the board to reduce the cost.
The fourth is the influence of circuit complexity. If the circuit layout of the four-layer board is more complex, the price will also be higher. Therefore, when designing the circuit, you should try to simplify the layout and reduce the number of layers to reduce the cost.
Finally, the influence of production quantity. In the PCB manufacturing process, the production quantity will also affect the overall price. Generally speaking, the cost of mass production is relatively low because optimized production methods and raw material procurement can be carried out. Therefore, if you need to mass produce PCB four-layer boards, you can always contact Kinglisheng (Shenzhen) Electronic and Technology Co., Ltd. to get a better price.
