PCBMay Provides Different Types of PCB Stack-up

Why Choose PCBMay for Your PCB Stack-up

PCBMay provides many types of multilayer PCBs with layers in the range from 4 to 40 layers, board thickness from 0.2mm to 5.0mm, copper thickness from 18μm to 350μm (0.5oz to 10oz), inner layer copper thickness from 18μm to 21μm (0.5oz to 6oz), and minimal spacing between layers to 3mil.

As an ISO and UL certificated PCB manufacturer in China, we put quality first. We have strict procedures to control the incoming materials.

PCB Stackup: The Ultimate FAQ Guide

Do you want to enhance the reliability and efficiency of PCB? If the answer is positive, you can think about PCB stackup.

PCB stackup can develop the compatibility of PCB along with cost minimization. But, how much do you know about PCB stackup? Are you aware of the pros & cons, layers, laminations, etc of PCB stackup?

Don’t worry. We are here to make you aware of such topics. This ultimate FAQ guide will answer all of your queries about PCB stackup.  Let’s make a move.

What is PCB Stackup

PCB stackup means organizing the insulating layers and copper layers of PCB. PCB stackup needs to be done before completing the design of the PCB layout. A proper PCB stackup ensures experiencing excellence in the electric circuit.

PCB Stackup

PCB stackup deals with PCB layers, cores, prepregs, laminations, vias, etc. The right PCB stackup depends on all of these.  It can render you the integrity of circuit, noise-free signals, most noteworthy a high-quality PCB.

PCB Stack-up refers to the arrangement of copper layers and insulating layers that make up a PCB prior to board layout design.

While a layer stack-up allows you to get more circuitry on a single board through the various PCB board layers, the structure of PCB stack-up design confers many other advantages:

• A PCB layer stack can help you minimize your circuit’s vulnerability to external noise as well as minimize radiation and reduce impedance and crosstalk concerns on high-speed PCB layouts.
• A good layer PCB stack-up can also help you balance your need for low-cost, efficient manufacturing methods with concerns about signal integrity issues.
• The right PCB layer stack can enhance the Electromagnetic Compatibility of your design as well.

The simple stack up is 2layer, please see the stack up as below:

2layer Stack-up

It will very often be to your benefit to pursue a stacked PCB configuration for your printed circuit board-based applications.

For multilayer PCBs, general layers include ground plane (GND plane), power plane (PWR plane), and inner signal layers.

Why Is A Multilayer PCB Stackup Better Than Single Layer PCB?

Both single layer and multilayer PCB stackup can render a positive change in your circuit. But, multilayer PCB stackup provides you more benefits than single layer PCB. Do you know about their differences?

Nothing to worry about. We are now explaining the distinguishing points on how multilayer PCB stackup is better.

High Quality

Multilayer PCB stackup maintains a higher quality than single layer PCB. You need to assemble skilled manufacturers, top-class materials, and highly effective tools for experiencing a well-designed multilayer PCB stackup.

Multilayer PCB

All of these will result in a high-quality device. Besides, you have to add up-to-date features for controlling impedance and resisting electromagnetic radiation.

In the case of single-layer PCB stackup, you don’t need to maintain such an intensive process.

Compatible With Complex Circuit

In a device with a complex circuit, you should apply multilayer PCB stackup rather than single-layer PCB. Multilayer PCB can connect more electric circuits on a single PCB. So it saves the space of your circuit.

Moreover, you can operate complicated circuits. In modern times, you can’t afford a complex design in a single-layer PCB. So, multilayer PCB stackup is capable of handling such difficulties.

Lightweight With Small Size

Multilayer PCB stack layers on top of one another. That’s why you can make it functional in a smaller space easily. So its size is smaller than other PCBs. This small size results in a lightweight which enhances its functionality multiple times of the single-layer PCB.

Single-layer PCB can match the efficiency of multilayer PCB after connecting a lot of single-layer PCB. But, this will turn your device huge and bulky.

Durability

Multilayer PCB stackup is preferable to single-layer PCB for its high durability. A developed stacked multilayer PCB has high thickness. It increases its longevity. A well-designed multilayer PCB stackup can make it safe from external forces also.

Again, multilayer PCB stackup can increase the ability to operate at high speed.

Unique Connection Point

Unlike multiple single-layer PCBs, you can connect all the components of multilayer PCBs to a unique point. This property makes the PCB stackup hassle-free.

So, if you are looking for the best PCB, a multilayer PCB  stackup will be the correct choice for you. We provide the best service of multilayer PCB stackup. Contact us for your PCB project.

How Can You Stack Up The PCB Layers?

An ill-fabricated PCB can cause the degradation of the performance of devices. For experiencing the maximum output, PCB stackup is the best solution.

To stack a PCB properly, you have to determine some necessary things first.

• The required number of layers for a well-designed PCB stackup depends on the pin density, signals, ground layers, controlled impedance, etc. Now multilayer PCB stackup is providing more advantages. Usually 6 or 8 layers PCB stackup is highly effective.
• You need to choose the layer materials comparing the standard values.
• Layer arrangement should be in a proper way. You should place the ground and power planes in the inner layer. Again, signal layers must not be placed sequentially.
• Determine the right vias for the PCB stackup.
• Lastly, select an effective software to run the stackup smoothly.

8 Layer PCB Stackup

Now, you are ready for PCB stackup after determining the above factors. You can make  the layer arrangement of 8 layer PCB stackup in the following pattern:

• Top layer
• Prepreg
• Ground plane
• Core
• Inner layer
• Prepreg
• Power plane
• Core
• Ground plane
• Prepreg
• Inner layer
• Core
• Power plane
• Prepreg
• Bottom Layer

You need to place a power or ground plane between two signal layers. It protects from electromagnetic interference. You can watch this video:

What Are The Benefits Of PCB Stackup?

PCB is the base of electric circuits of modern days. To solve the increasing complications of circuits, PCB stackup is a great solution for manufacturers. PCB stackup has brought out immense benefits. Such as:

Connecting Multiple Circuits

PCB stackup permits the connection of several circuits on a single PCB. Multilayers PCB allows this joining.

Cost Minimization

A good stack of PCB can minimize the cost of production. As PCB stackup can place multiple electric circuits on a PCB, so you have to pay a lesser manufacturing cost.

Efficiency

PCB will become more efficient through a proper PCB stackup. PCB stackup reduces crosstalk issues in rapid audio-visual systems. That’s why PCB stackup promotes the effectiveness of electric circuits.

Proper PCB Stackup

Compatibility

It enhances the electromagnetic compatibility of PCB-based applications. So, PCB won’t be in a high-vulnerable state after PCB stackup.

Impedance Control

High impedance promotes electromagnetic interference to the signal. So, impedance increasing and mismatching are harmful to PCB. The impedance of PCB will be lessened after a well-designed PCB stackup.

Noise Reduction

A well-stacked PCB can save the internal layers from noises. So, external forces can’t hamper the PCB.

Decrease Radiation

In speedy PCB layouts, sometimes you can see huge radiation from the devices. PCB stackup reduces this radiation to a large extent.

Highly Functional

A good PCB stackup enhances the functionality of the device. It also develops speed. So, your PCB-driven device turns into an extremely functional device.

In addition to these, PCB stackup offers you space-saving facilities, compatibility with complex circuits, etc.

Is 8 Layer PCB Stackup Better Than 4 Layer PCB Stackup?

8 layer PCB stackup is better than 4 layer PCB in some aspects. Here, we are explaining the aspects for you.

• 8 layer PCB stackup makes it more compatible with complex circuits than 4 layer PCB.
• A well-developed 8 layer PCB stackup comes with more durability than a 4 layer PCB. So, it is protected from external noises.
• The data processing speed of 8 layer PCB is higher compared to 4 layer PCB.
• 8 layer PCB stackup reduces the weight and size of the PCB. So, the device will be light-weighted.

4 Layer PCB Stackup

On the contrary, 4 layer PCB stackup is cost-effective than 8 layer PCB. Besides, some circuits demand 4 layer PCB. But, you can choose 8 layer PCB stackup without any hesitation.

Why Are The Power and Ground Planes Usually Inner Layers For A 4 Layer PCB Stackup?

The ground plane is attached to the ground level of the power supply. Similarly, the power plane, which is a copper plane, is linked with the power. In a 4 layer PCB stackup, both of these planes are usually inner planes.

Do you know the reason? We are telling you about this.

In a 4 layer PCB,  components are connected in such a way that they can be routed on a single layer.  In that case, you don’t need a through-hole pad or via to connect the surface mount device component on the same layer.

Now think. You get all the signals on a layer without using any via except ground or power planes. This will give the opportunity of adding more circuits to the PCB. If you place the ground and power planes in the outer layer, it will be complicated to diagnose the PCB.

4 Layer PCB

PCB traces are normally located on the surface space. You can apply blind vias to place the traces in the inner layer. But, it demands more effort and cost.

What Are The Drawbacks Of Multilayer PCB Stackup?

Despite having immense advantages, multilayer PCB stackup has some drawbacks also. You should be aware of such limitations.

• Its price is higher than single-layer PCB stackup.
• A proper multilayer PCB stackup requires a longer time than the others.
• Multilayer PCB stackup is a relatively complex task. If PCB becomes physically damaged, it will be difficult to repair. You can’t repair it without a highly skilled manufacturer of PCB.
• A trustworthy manufacturer for multilayer PCB stackup is hard to find.

What Is The Best Lamination For PCB Stackup?

Lamination is an essential part of PCB stackup. It means arranging consecutive layers and binding them. Lamination is performed after stacking of inner layers and prepregs.

We are here to help you to choose the best lamination techniques for PCB stackup.

Teflon microwave lamination

This is the best lamination technique for PCB stackup dealing with high-speed signals and radio frequencies.

Sequential lamination

This is a costly and time-consuming process. It is performed in case of having more than two subsets of PCB.

Sequential Lamination In PCB

These are the most effective techniques of lamination for PCB stackup. Besides, you can also apply multilayer PCBs.

How Can You Calculate Impedance For PCB Stackup?

In a high-speed electric circuit, you need to control the impedance of the PCB trace for a good stackup. That’s why you have to know to calculate the controlled impedance for PCB stackup.

You can use a formula described in the IPC publication, IPC-2141. This contains a smaller range of configurations.  According to this, you need to calculate the rise time and maximum length of the PCB trace first.

Rise time, t= 0.35/maximum frequency.

Maximum trace length l= rise time x 2 in/ns

Then you can find the controlled impedance by using the following equation.

Impedance,

Here, ε_r  = Dielectric constant of the material

h= trace height, w=trace width, t= trace thickness

You can also use Wadell’s equation. It is more comprehensive to calculate impedance for PCB stackup.

Figure 7: Impedance Control PCB

Here, w’= equivalent width of a track

w= width, ηo= impedance at free space.

You should calculate the controlled impedance of the PCB trace at maximum frequency.

What Is Prepreg In PCB Stackup?

Prepreg is the short form of pre-impregnated. It is usually an insulation layer used in PCB stackup. It normally makes bonding between a copper foil and a core. Sometimes prepreg can connect two cores also. Here, the glass fiber with resin makes this bondage.

Impedance Control PCB

Prepreg is placed in the middle of cores and copper foil. The dielectric property of prepreg renders the required insulation to bind them. Its thickness varies with the height of the etched PCB board.

Unlike the cores, the dielectric constant of prepreg is not fixed. They are more flexible than the core. Depending on the amount of resin. Prepregs are different types. Like standard, medium, and high resin.

What Is PCB Via In PCB Stackup?

In PCB stackup, via refers to a hole to connect the pads of PCB, located in corresponding positions of different layers. Via acts like a channel to maintain the flow of electrical current through the layers of PCB.

Vias are used in PCB for distributing the heat from pads to the surface layers. Vias are turned to be conductive by using electroplating. The terminal diameter of the via is around 0.45mm. There are barrels, pads, and anti-pads inside of a via.

PCB Via Types

A barrel is an electrically conductive tube. It is used to fill up the hole. Pads make contact with the PCB component at both ends of the barrel. Anti-pads act like a clearance hole.

There are 3 types of via used in PCB stackup.

• Blind Via
• Buried Via
• Through-hole Via

So, vias are highly important for a faultless PCB stackup.  You need to use multiple vias for PCB stackup. It will help to get fast electric signals.

What Is The Difference Between Via-in-pad And Via Antipad in PCB Stackup?

There are some basic differences between via-in-pad and via-anti-pad. Let’s have a look at this issue.

Via-in-pad is a PCB design where vias are on the BGA pads. This design lessens the required space for the vias. Via-in-pad decreases the region needed for signal routing.

PCB Via In Pad

On the other hand, via antipad refers to the region between via and copper. Via antipads are required to be free from shorts and maintain the impedance. But, this design sometimes hampers the integrity of signal in multilayer PCB stackup.

What Factors Should Be Considered Before Choosing The Right Via For PCB Stackup?

Via is an unavoidable part of PCB. So, you need to keep some important matters in mind before choosing the right via for PCB stackup.

• You should know about the fan-out of PCB. Fan out is a technique for connecting traces and vias to IC easily. If you use the through-hole vias for the fan-out, then you don’t require using blind vias or buried vias.
• The current rating is another thing to keep in mind. Rated current for the through-hole vias, blind vias, buried vias is 1A, 300mA, 950mA respectively. So, you should choose the vias following the current rating.

PCB Vias

• You have to check the air gap between the pads of the silicon chip. Buried and blind vias are perfect for the air gap below 9mm.
• You should not use the through-hole vias for the components located under the BGA fan-out.

What Are Blind And Buried Vias In PCB Stackup?

Blind via and buried via are different types of PCB vias used in multilayer PCB stackup.

Blind Via

Blind via links an outer layer with a single or several inner layers. In the case of blind via, the aspect ratio should be 1.1. Here, the aspect ratio of via means the ratio of diameter and depth of the hole.

Blind And Buried Via

Blind vias are visible from one side of PCB. That’s why its name is the blind via.

Buried Via

Buried vias can only connect the inner layers while stacking PCB. They are not related to the outer layers.  The aspect ratio is 1.12 or more for blind via.

As blind vias link with internal layers, you can’t see them from the outside. So, they are named by the blind vias.

How Can You Choose The Correct Thickness For PCB Stackup?

In PCB stackup, the thickness of PCB depends on the number of layers you are using. The standard thickness of PCB can vary following your applications. So, you need to be very conscious about choosing the correct thickness for the PCB stackup.

The standard thickness is in the range of 0.008-0.24 inches. You must need to think about mechanical,  electrical, and thermal properties to identify what is the right thickness for you. Here is a list for you to keep in mind.

Impedance

The impedance of PCB is connected with the dielectric constant of PCB material. As thickness can influence the dielectric, so you need to know the controlled impedance to choose the right thickness.

Required Space

You should use a thicker PCB for a device having broader space. Otherwise, you can choose a thinner PCB for small devices.

Weight

A thinner PCB is usually required for a light-weighted device. But, you need to use it with heavy-weighted devices if the circuit demands it.

Components

Some components and connectors demand specific thickness. So, you have to use a PCB of such thickness.

How Can You Verify A PCB Is Rightly Fabricated?

You can verify the fabrication of PCB by conducting some effective tests. Now, We are going to explain these tests for your convenience.

In-circuit Test(ICT)

You need to use a huge number of testers, a specific fixture, and software for the in-circuit test. In this case, the tester checks the connection of the solder. The software gives the required instructions for the test.

Here, a bed of nails is used to add the probes and access points of the PCB prescribed in the fixture in a definite pressure  The value of different components, shorts and open, etc can be tested through the in-circuit test.

The ICT test is effective but costly. You can reduce the cost by checking a huge number of PCBs.

X-Ray Inspection Test

This test is conducted when you fail to detect the faults of the PCB stackup visually. Here, X-rays are used to find the defects of the connections of the solder,  components, connectors, etc of  PCB.

X-ray inspection is a time-consuming and costly test.

Flying Probe Test

This test has no custom fixture. You have to put the probe in different points of a PCB. That’s why its name is the “Flying probe test”.

Flying Probe Test

You can check the problems of capacitance, inductance, shorts and opens, etc through this test. This is a cost-effective test. But, it consumes more time than other tests.

You can also conduct an automated optical inspection test or functional test to verify the fabrication of PCB.

What Is HDI PCB Stackup?

HDI is the short form of a high-density interconnector. Unlike other PCBs, the wiring density per unit area is high for HDI PCB. It promotes the efficiency of multilayer PCB.

HDI PCB lessens the weight and size of the device.

But, it never trades off with the performance of PCB. Here, micro vias, blind vias, and buried vias are used. So the required PCB space is minimized. The use of these vias also reduces the impedance of PCB.

HDI PCB Stackup

On average, an HDI PCB can accommodate 120 to 170 pins on a PCB. It provides compact circuit design, the integrity of the signal, low cost, reliability, and versatility in PCB stackup.

During the HDI PCB stackup, you should try not to use more than three consecutive layers. HDI PCB is compatible with higher pitch packages. Here, direct drilling is not mandatory.

There are different types of HDI PCB stackup. Such as 1+N+1, i+N+i(i ≥2), any layer HDI, etc. Watch this video to know about PTH HDI PCB stackup:

What Is Meant By 1-N-1 In HDI PCB Stackup?

HDI PCB stackup can be classified into many types. These types are denoted by i+N+i, where i is any positive integer. Here, “i” denotes the number of lamination on each side of the PCB core.

1+N+1 means there is one sequential lamination used in HDI PCB stackup. You can apply 1+N+1 HDI PCB stackup by using buried via and micro via. There is no use of the stacked via.

1-N-1 HDI PCB

Here, one lamination can connect two copper layers. So, 4 copper layers are added on both sides of the core.

How Can You Choose The Best PCB Stackup?

Usually multilayers PCB stackup is preferable for the electric circuits. There are some criteria to choose the best PCB stackup. Such as-

• Compatibility with complicated circuits
• Reducing signal noise
• Lessening EMI
• Easy and rapid repairing
• Cost of stackup
• Durability in difficult conditions
• Availability of manufacturer

PCBMay’s Standard PCB Layer Stack-up

PCBMay manufactures multilayer circuit boards with layers in the range of 4 to 40 layers, board thickness from 0.4mm to 4.0mm, copper thickness from 1oz to 8oz, inner layer copper thickness from 1oz to 4oz, and minimal spacing between layers to 3mil.

The following images present PCBMay’s default layers stack-up of PCB service.

If you don’t require customized PCB layer stack-up,we will make the multilayer PCBs according to our default layers stack-up as below:

This is the stack-up for standard 4layer, normally there’re 4 Copper  foil’s,1 Core, and 2 Prepreg’s:

4layer Stack-up

This is the stack-up for standard 6layer, there’re 6 Copper  foil’s,2 Core, and 3 Prepregs:

6layer Stack-up

This is the stack-up for standard 8layer, normally there’re 8 Copper  foil’s,3 Core, and 4 Prepregs:

8layer Stack-up

This is the stack-up for standard 10layer, normally there’re 10 Copper  foil’s,4 Core, and 5 Prepregs:

10layer Stack-up

This is the stack-up for standard 12layer, normally there’re 12 Copper  foil’s,5 Core, and 7 Prepregs:

12layer Stack-up

Why Need Stack-up

Before designing a multi-layer PCB, designers need to first determine the circuit board structure according to the size of the circuit, the circuit board size, and EMC requirements.

That is, decide whether to use a 4layer or 6layer or 8layer or more circuit board.

After determining the number of layers, determine the location of the inner layers and how to distribute different signals on these layers.

Planning a multi-layer PCB stack-up configuration is one of the most important aspects to achieve optimal product performance.

Improperly designed substrates and improperly selected materials will reduce the electrical performance of the signal transmission, thereby increasing emission and crosstalk, and making products more susceptible to external noise.

These problems may cause intermittent operation due to timing failures and interference, which greatly reduces product performance and long-term reliability.

On the contrary, a correctly constructed PCB substrate can effectively reduce electromagnetic radiation, crosstalk and improve signal integrity, thereby providing a low-inductance power distribution network.

And, from a manufacturing point of view, the manufacturability of products can also be improved.

Conclusion

PCB stackup has become a beneficiary for electric circuits. It can provide you with the maximum output of PCB. This FAQ guide will help you to learn about PCB stackup better. Here, we have covered almost all the queries related to PCB stackup.

We have intended to make the explanation so simple. We hope you won’t face any problems with the PCB stackup next. You can’t upgrade your electric circuit from a bare minimum phase without a PCB stackup. Contact us to enjoy the supremacy of PCB stackup.