4 layers PCB refers to the printed circuit board is made of 4 layers of glass fiber. There are four wiring layers: Top layer, bottom layer, VCC, and GND. Generally, through holes, buried holes, and blind holes are used to connect the layers. There are more buried and blind holes than double-side boards. In addition, try not to run signal track on the two layers of VCC and GND.
4 layer PCB boards have many advantages over double-sided boards. They can be designed more compactly, they significantly improve noise immunity, and are much easier to lay out.
4 Layer PCB Capability :
Provide free DFM Checking , We can suggest 4 layer PCB stack-up
Copper Thickness: Max to 6 oz inner copper, 12 oz outer copper
Min Hole: 0.15mm by mechanical drilling 0.1mm by laser
PCB Thickness :0.4mm – 6.5mm
Surface Process: Immersion gold ,HASL-LF,Hard Gold,Immersion Tin
Soler Mask: Green Yellon White Black or custom
Silkscreen: White Black Yellow or custom
Accept 4 layer PCB with Blind or buried hole
How to Design a 4 Layer PCB Board
1. 4 Layer PCB Layer-out Guidance
Generally speaking, 4 layer circuit board includes the top layer, bottom layer, and two middle layers. The top and bottom layers are lay out with signal lines. The middle layer first uses the command DESIGN/LAYER STACK MANAGER to add INTERNAL PLANE1 and INTERNAL PLANE2 with ADD PLANE as the most used power layers such as VCC and ground layers such as GND that is, connect the corresponding network labels. Please note: you should not use ADD LAYER. This will increase MIDPLAYER, which is mainly used for multi-layer signal line placement.
PLANE1 and PLANE2 are two layers of copper connecting the power supply VCC and the ground GND. If there are multiple power sources such as VCC2 or GND2, first use a thicker wire in PLANE1 or PLANE2 or FILL. At this time, the wire or the corresponding copper ground is not visible, and the wire or filling can be clearly seen against the light.
To delimit the power or ground plane (mainly for the convenience of the PLACE/SPLIT PLANE command later), use PLACE/SPLIT PLANE to delimit the area in the corresponding areas of INTERNAL PLANE1 and INTERNAL PLANE2. VCC2 copper and GND2 copper should not be in the same PLANE as VCC. Please note that different network surface layers in the same PLANE should not overlap if possible.
Suppose SPLIT1 and SPLIT2 overlap in the same PLANE (SPLIT2 is inside SPLIT1). The two pieces are automatically separated according to the SPLIT2 border (SPLIT1 is distributed on the periphery of SPLIT). Pay attention to the pads or vias of SPLIT1 when overlapping; don’t try to connect SPLIT1 to the area of SPLIT2. At this time, the via holes in this area are automatically connected to the corresponding copper in the same layer. The DIP footprint components and plug-in parts that pass through the top and bottom boards will automatically get away from the PLANE in this area. Click DESIGN/SPLIT PLANES to view each SPLIT PLANES.
The Layer Setting and the Division of the Internal Electric Layer of Protel99
There are two types of electrical layers in PROTEL99. Open a PCB design file and press the shortcut key L, and the layer setting window appears. The one on the left (SIGNAL LAYER) is the positive layer, including TOP LAYER, BOTTOM LAYER, and MID LAYER. The one in the middle (INTERNAL PLANES) is the negative layer, also called the INTERNAL LAYER.
These two layers have different properties and usage methods. The positive layer is generally used for pure track lines, including outer and inner lines. The negative film layer is mostly used as a ground and power layer. In the multi-layer PCB board, the ground and power layers generally use the whole piece or several large copper partitions for the circuit. You must lay copper if you use the MID LAYER, also known as the positive layer. Paving copper will make the entire design data volume very large, which is not conducive to data communication and transmission, and will affect the HDI design refresh speed. With negative film, you only need to create a THERMAL PAD at the junction of the outer and inner layers, which is very beneficial for design and data transmission.
Add and Delete Inner Layer
In design, there are instances where it will need to add or delete layers. For example, the double-sided board is changed to a four-layer board, or the four-layer board with higher signal requirements is upgraded to a six-layer board, and so on. If you need to add an electrical layer, you can follow the steps below:
In the DESIGN-LAYER STACK MANAGER, there is a schematic diagram of the current stack structure on the left. Click the upper layer where you want to add a new layer, such as TOP, and then click ADD LAYER (positive film) or ADD PLANE (negative film) on the right to complete the addition of the new layer. If the new layer is a PLANE (negative film) layer, you must assign the corresponding network to the new layer by double-clicking the layer name.
There can only be one network assigned. Generally, a GND is sufficient for the ground layer. If you want to add a new network to this layer, such as a power layer, it can only be achieved by internal segmentation in the subsequent operations. Therefore, you first have to allocate a network with a large number of connections.
If you click ADD LAYER, a MID LAYER (positive film) will be added, and the application method is the same as the outer circuit. Suppose you want to apply a mixed electrical layer with both wiring and a large copper surface for power. In that case, you must use the positive layer generated by ADD LAYER to design (see the reason below).
Slip of the Inner Electrical Layer
If several groups of power supplies are in the design, you can use inner layer division in the power layer to distribute the power network. The command to be used here is PLACE-SPLIT PLANE. Then set the layer in the dialog box that appears, specify the network to be allocated for the split at CONNECT TO NET, and place the split area according to the copper paving method.
After the placement is complete, the holes with the corresponding network in this segmented area will automatically generate flower hole pads, which completes the electrical connection of the power layer. You can repeat this step until all power is allocated. When the inner electric layer needs to allocate more networks, it is more troublesome to divide the inner layer and require proper experience.
There is also a problem to be noted here: Excluding PLACE FILL, there are two electrical connection methods for large copper in PROTEL. The first is POLYGON PLANE or ordinary copper paving. This command can only be applied to the positive layer, including TOP /BOT/MID LAYER. The other is SPLIT PLANE or the internal electrical layer division. This command can only be applied to the negative film layer or INTERNAL PLANE. Attention should be paid to distinguish the scope of use of these two commands. Modify the command of split copper plating is EDIT-MOVE-SPLIT PLANE VERTICES.
2.How to design the stack up when designing a 4 layer PCB board?
In theory, there are three options.
Option 1:
One power supply layer, one ground layer, and two signal layers are arranged as below:
TOP (signal layer);
L2 (ground layer);
L3 (power layer);
BOT (signal layer).
Option 2:
One power supply layer, one ground layer, and two signal layers are arranged as below:
TOP (power layer);
L2 (signal layer);
L3 (signal layer);
BOT (ground layer).
Option 3:
One power supply layer, one ground layer, and two signal layers are arranged as below:
TOP (signal layer);
L2 (power layer);
L3 (ground layer);
BOT (signal layer).
Signal layer
Ground layer
Power layer
Signal layer
What are the advantages and disadvantages of these three options?
Option 1: The main stack-up design of the four-layer PCB is a ground plane under the component surface. The key signal is preferably the TOP layer. As for the layer thickness setting, here are the following suggestions: the impedance control core board (GND to POWER) should not be too thick in order to reduce the distribution impedance of the power supply and the ground plane to ensure the decoupling effect of the power plane.
Option 2: In order to achieve a certain shielding effect, the power and ground are placed on the top and bottom layers. However, this method has the following defects:
1) The power supply and the ground are too far apart. The plane impedance is large.
2) The power supply and ground plane are incomplete due to the influence of electronic component pads. Because the reference layer is incomplete, the signal impedance is not continuous.
In fact, due to a large number of surface-mount components, the power supply and ground of the solution can hardly be used as a complete reference layer. The expected shielding effect is excellent, but it is challenging to implement; it has a limited scope of use. However, in individual boards, it is the optimal layer setting option.
Option 3 is similar to option 1 and applies to the condition where the main device is wired in the bottom layout or the underlying signal.
1.6 mm standard 4 layer PCB stack-up
0.2mm( PP thickness)+ 1.2mm(Double side core material)+0.2mm(PP thickness)=1.6mm 4 layer PCB stackup
1.2mm typical 4 layer PCB stack-up
1.2mm thickness=0.2mm PP & coil +0.8mm double side core material+0.2m PP with copper
How to Use Altium Designer10to Draw 4 Layer Board
If you could implement double side PCB, the same can be applied to 4 layer PCB boards. The following describes how to draw a 4-layer board based on a 2-layer board.
The above picture is a 2 layer board. The below shows two layers: the top and bottom layers. The layer is the signal layer, also known as the positive film, and can do circuit layout on this layer. Others include a mechanical layer, silkscreen layer, solder mask, and so on.
Below is the 3D drawing
In the English version, press and hold the ctrl + L keys to view frequently used layers.
As shown below:
The signal layer includes the top layer and bottom layer, and the mechanical layer includes 1, 13, 15 (of course, it can be added). The mask layer has top/bottom paste, top pad layer, or solder stencil layer, and top/bottom solder is the top or bottom solder mask to prevent it from being covered by green oil. There are two silkscreen layers below, top/bottom overlay. There are other layers, the keep-out layer used to define the shape of the board, the drill drawing layer, etc.
There is also an internal plane next to the signal layer, called the internal electric layer or negative film. Only layer division can be performed on this layer, and signal wiring cannot be performed.
Click Design — Layer Stack Manager in the menu bar, as shown in the figure below:
This is the layer manager. You can easily see the layer distribution in the above figure. This board has only two layers: the top and bottom layers, both of which are signal layers. There are two more options on the right. One is “Add Layer”, the other is “Add plane”. Add layer adds a signal layer, add plane adds an internal electric layer (negative film).
To add a layer, first select a base layer. Then click on “Add Layer” to add the signal layer under the top layer.
Then you can rename the added layer, such as VCC, and add another layer as GND, as shown in the following figure:
Back to the PCB interface, you can see that there are already 4 layers.
You already know how to create 4 layers, 6 layers, even 8 to 20 layers with the same operation.
When dividing the inner electric layer, we can only divide it and could not create a circuit layout, as shown in the following figure:
Adding the internal electrical layer is to add the “add plane” in the Layer Stack Manager.
The internal electrical layer split in the figure above can be split by drawing a line with the place—line command. After the split is completed, double-click to set the network label.
Pay attention to the distribution of components when splitting the internal electrical layer and distribute the same power supply in one area to facilitate the division.
The following is the signal distribution at different layers:
Top layer：
VCC layer：
GND layer:
Since the GND layer is a whole piece of GND, it is sufficient to lay the copper. Pay attention to maintaining the integrity of the GND layer.
Bottom layer:
When open all layers as below shown:
3D drawing：
Main points of 4-layer board wiring:
Pay attention to the distribution of power supply;
Pay attention to the signal line width setting and impedance control;
Distribution of layers, how to arrange 4-layer boards;
High-speed signal return problem;
Crosstalk between high-speed signals;
How to reduce the minimum loop and reduce the EMI problem;
Placement of decoupling capacitors;
If you learn to use Altium software to draw 4 layer boards, you can also use EasyEDA, Eagle, and KiCad to draw 4 layer boards.
2 layer vs. 4 layer PCB Prices
4 layer PCB board has GND and POWER layers in the middle of TOP and Bottom layers.
Features of the 4 layer board
1) Reference plane, impedance calculation can be done
2) Shorter return path
3) More layers, simpler design
4) Higher cost than 2-layer board
Based on the wiring density in the layout, look at the densest place of the flying lines, where there are crossovers. It is judged that at least 2 layers of wiring are required, and the cost (design multiple layers regardless of the cost), signal quality consider whether to choose 4-layer board.
After the layout, it is judged how many layers to use, mainly depending on the density of the signal and the place with the most flying lines.
Why Choose to Design 4 Layer PCB
- When there is a BGA package, the outer 2 rows can be directly pulled out to go to the top layer. The third and fourth layers can be drilled to go to the bottom layer, and the fifth and sixth rows can be drilled to go to the bottom layer. However, the inside power and ground wirescannot go out, so an additional layer design is required, and two more layers are added.
- The power lineblocks the signal line.
- Whenline density is not high, you can use a 2-layer board, but you can choose a 4-layer board based on signal quality considerations.
Different Manufacturing Process
How Do You Make a 4 Layer PCB
The 4-layer board is laminated based on the double-sided board. When lamination, PP, and copper foil are added on both sides of the double-sided board, it is then pressed into a multilayer board through high temperature and high pressure. In short, the 4-layer board has an inner layer. In terms of the process, some lines will be etched through the inner layer formed by lamination. The double-sided board can be drilled after cutting the raw material sheet directly.
Technology Process difference
- Double-sided PCB with HASL surface finished process:
Cutting material grinding → drilling → electroless copper → outer layer circuit → tin plating, etching tin removal → secondary drilling → inspection → printing solder mask → gold-plated → hot air leveling → printing silkscreen → outline processing → testing → inspection
- How do you manufacturea 4 layer PCB:
Cutting material and grinding → drilling positioning holes → inner layer circuit → inner layer etching → inspection → black oxide → lamination → drilling → electroless copper → outer layer circuit → tin plating, etching tin removal → secondary drilling → inspection →print solder mask→Gold-plated→Hot air leveling→print silkscreen→routing outline→Test→Inspection
Price difference
PCB production costs are related to the actual area and specific technology requirements. If there are no special requirements, a 4-layer board’s cost is almost 1.8 to 2 times that of a 2-layer board. This is not a linear relationship. If the 4-layer board has impedance or even a blind buried hole design, the price difference is even greater.
Altium Designer 4-layer PCB Design Tutorial
This tutorial allows beginners to get started. The software I use is Altium Designer 13, but the basic operations are similar to other software.
1.Preparation
Create a new project file, create a related schematic file, and prepare the relevant PCB design. Create a new PCB file.
2.Set the layers
In the PCB interface, click the main menu Design and then click Layer Stack Manager
As shown below:
After clicking, the following layer manager dialog box will pop up. The default is double-panel in AD, so we see only two layers of circuit.
Now let’s add a layer. First, click Top Layer on the left, and then click the Add Plane button in the upper right corner of the layer manager to add an internal electrical layer. Because we are working with a 4-layer board using negative film, you need to add an internal electrical layer and not Add Layer. Afterward, a layer will be automatically added under Top Layer. Double-click the layer, and we can edit the related attributes of this layer, as shown in the figure below:
In the item corresponding to Name, fill in VCC and click OK to close the dialog box. Rename the layer to VCC as the power layer during design. In the same way, add another GND layer. Below is the figure after completion:
3.Import network
Back to the schematic interface, click the main menu Design ==> Update PCB Document. As shown in the figure:
After finishing the layout of the components on the PCB drawing, draw the outline of the PCB on the Keep Out Layer, as shown below:
Modify the PCB drawing size to overlap the lines of the keep out layer. First, set the grid network width to 20mil. Then click the pad symbol in the shortcut toolbar, and move the mouse to the top left corner of the keep out layer. A circle should appear in the center of the pad. Click the arrow keys on the keyboard to move the pad (click in the left direction, click in the upper direction). Press the enter key, as shown in the figure:
Set the other four corners the same way.
Then click design -> board shape -> move board vertice, overlap the four points on the drawing with the pad placed just on the keep-out line, and click the right button.
Delete the pads on the four corners.
4.Set the inner electric layer; I have divided the inner electric layer in the process here.Then execute design -> layer stack management -> double-click the GND layer, and select the GND network in the NET NAME, which is defined as the GND layer (before, it was just a GND name).
Set the VCC layer: First, enter the VCC layer, use the line place -> line to divide the VCC layer (the closed line or both ends of the line are connected to the outer pullback line), divide into different NET layers, and then click on different areas to select different NET.
At this time, we can see a virtual circle around the pad of the corresponding internal electrical layer. The color of the cross on the pad represents the color of the corresponding internal electrical layer. For example, the inner layer GND is brown, and the cross of the pad is also brown.
p.s
The pullback automatically appears around the PCB drawing after the Layer Stack Manager is set. You can double-click the inner layer to set the pullback line width.
The cross of the pad only appears when the pad is placed on the corresponding net layer. If it is placed on other layers, it will not appear. As long as the cross passes through the VCC layer, it will appear.
