4-LAYER PCB TUTORIAL
DEFINITION, STACK UP, PROTOTYPE, AND MANUFACTURING COST
What Is 4-Layer PCB?
A 4-layer PCB simply means that it has four layers. These four layers include two inner layers, one top layer, and one bottom layer. Among these four layers, two are signal layers, one is VCC, and the remaining one is GND.
Usually, inner layers are used as power and GND, and outer layers (top and bottom) are used for signal routing and component placement. The reason behind using inner layers as power and GND planes because it tends to reduce EMI emissions, and it also improves the quality of the signal. In a 4-layer PCB, it is simpler and easier to connect the components than routing power and GND planes along with traces. However, with us, you don’t need to worry about that. We provide every type of 4-layer PCB and prototype services at JHYPCB.
Standard 4-Layer PCB Design – Stack up And Thickness
There are three ways you can stack up a 4-layer PCB when designing. A 4-layer PCB has four layers; one layer is power, one layer is ground, and the other two layers are signal layers. Now the stack-up can be different according to the placement of ground, VCC, and signal layers. There can be three types of 4-layer PCB according to stack-up.
1) First Stack Up:
- Top Layer – Signal Layer
- Inner Layer 1- Power Layer
- Inner Layer 2 – Ground Layer
- Bottom Layer – Signal Layer
The first type of 4 layer PCB stack up
The bottom layer of the PCB is the key signal layer. Here, core thickness also matters, and it should not be too much. This thickness of the core and PP (prepreg) between the layers is responsible for the distribution impedance. The lesser the distance between power and ground layer, the lesser will be the plane impedance. If the thickness is more, then it would be difficult to decouple the power plane.
2) Second Stack up:
- Top Layer – Power Layer
- Inner Layer 1- Signal Layer
- Inner Layer 2 – Signal Layer
- Bottom Layer – Ground Layer
The second type of 4 layer PCB stack up
This stack-up is one of the safest stack-ups for a 4-layer PCB. The power and ground layer act as a shield for the signal layers. But this stack up has some disadvantages.
The first disadvantage is the distance between the power and the ground layer. The plane impedance increases because of the distance between these two. Secondly, due to the effect of electronic components, the reference layer is not complete, so the impedance of the signal is not continuous. Due to a number of components, it is very difficult to use the ground layer as a complete reference layer. Moreover, it isn’t easy to implement as well. But the shielding of the signal layer is excellent in this stack up.
3) Third Stack up:
- Top Layer – Signal Layer
- Inner Layer 1- Ground Layer
- Inner Layer 2 – Power Layer
- Bottom Layer – Signal Layer
The third type of 4 layer PCB stack up
The third type of stack-up is very similar to the first one. In the first stack up, we know that the main device is connected to the bottom, but not in this stack up. Here, the key signal layer is the top layer. The rest of the stack-up is pretty the same.
Core and Prepreg (PP) Thickness
There are two types of Core and PP thicknesses when it comes to 4-layer PCBs. The standard one is 1.6 mm, and the others are a bit typical. 1.2mm is also commonly used. In 1.6 mm thick PCB, double side core material consists of 1.2 mm, and the two PP have a thickness of 0.2 mm, which in total becomes 1.6 mm.
Other typical 1.2mm thickness comprises double-sided core material of 0.8 mm, 0.2 mm PP along with coil and 0.2 mm PP with copper. These two types of thickness have their own pros and cons, and the choice depends on the user. The cost of a 4-layer PCB also depends on the thickness.
2-Layer VS 4-layer PCB
The first and basic difference between 2-layer and 4-layer PCB is the number of layers, as the name suggests. A 4-layer PCB has two additional layers for power and routing. The signals are usually routed inside the PCB, and the top and bottom layers are used for grounding. But as mentioned earlier, the inner layers are usually used for power and grounding.
In a 4-layer PCB arrangement, routing is much easier than in a 2-layer PCB. Moreover, a 4-layer PCB is more expensive and complex than a 2-layer PCB. The 4-layer PCB must be used when required because it is difficult and inefficient to use a 4-layer PCB for a simpler task, and it will be impractical.
The inner layers of a 4-layer PCB can hide traces that makes debugging extremely difficult. If a 4-layer PCB requires debugging, it would be easy to follow CAD designs and drawings rather than following the traces. But a 4-layer PCB makes your circuit compact and increases its performance. It also makes complex routing easy.
4 Layer PCB Prototype
4-layer PCBs are a bit complex; therefore, so you might not get the desired results. It requires the testing of desired results. There could be multiple errors and problems in the first prototype; thus, you might need to revise the design and make other amendments.
Before the mass production of PCBs, it is important to get a prototype. Once you are sure everything is perfect, you can proceed with the batch production. At JHYPCB, we offer quick 4-layer PCB prototypes so that you can test everything on your end. You can even order one 4-layer PCB prototype or as many as you want.
Low Cost 4-Layer PCB Prototype Manufacturing
As discussed above, there are multiple factors on which 4-layer PCB price depends. The type of stack up and the kind of thickness are the most important ones. The other things that contribute to the price are the material of the PCB, copper thickness, surface finish, Via process, testing, impedance control, etc. The quote of the PCB is determined by looking at all the factors, but you don’t need to worry about these things. You need to provide us the details, and we will give you a reasonable quote.
Get Your 4-Layer PCB from JHYPCB
JHYPCB is a well-known service provider of all types of PCB and Assembly services. We offer solutions to all your problems under one roof. We can provide 4-layer PCBs and prototypes at a reasonable price. There is no restriction on the quantity; you can even order one PCB. We will make sure to deliver your PCB as soon as possible.
Our strict quality management system ensures high-quality PCBs. We are RoHS, UL, and ISO certified. Thus, we take the responsibility from component procurement to the delivery of PCBs at your doorstep. For more information and details, feel free to contact our 24/7 customer service team.
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