As the level of intelligence increases, more and more robotic sensors are used. There are three types of intelligent robots : interactive robots, sensor robots and autonomous robots. From the anthropomorphic function, vision, force and touch are the most important. It has already entered the practical stage, and the hearing has also made great progress. Others have sense of smell, taste, and slid. There are various sensors, so the robot sensing industry has also formed. Production and research strength. Internal sensor Machine-mechatronics products, internal sensors and mechanical components such as motors and shafts or mechanical structures such as arm (arm), wrist (Wrist), etc. are installed together to complete the measurement of position, speed and strength to achieve servo control. Position (displacement) sensor The linear motion sensor has two types of potentiometer sensors and adjustable transformers. The angular displacement sensor has three types: a potentiometer type, a variable transformer (resolver) and a photoelectric encoder. The photoelectric encoder has an incremental encoder and an absolute encoder. The incremental encoder is generally used for zero-position uncertain position servo control. The absolute encoder can obtain the instantaneous value of the drive shaft corresponding to the initial lock position of the encoder. When the device is under pressure, just read each joint code. The reading of the servo can adjust the given value of the servo control to prevent excessive movement during the start of the robot. Speed ​​and acceleration sensor Speed ​​sensors measure both translational and rotational motion speeds, but in most cases are limited to measuring rotational speed. Using the derivative of the displacement, especially the photoelectric method, the light is irradiated to the rotating disk, the rotation frequency and the number of pulses are detected, the rotation angle is determined, and a gap is formed by the disk, and the angular velocity is recognized by the two photodiodes, that is, the rotation speed This is the photoelectric pulse speed sensor. In addition, there are speed measuring generators for speed measurement. A strain gauge, a telescopic gauge, is also a stress sensor for acceleration measurements. The acceleration sensor is used to measure the dynamic control signals of industrial robots . Generally, there is a power derived from the velocity measurement and the power generated by the acceleration of a known mass object, that is, the strain gauge is used to measure the force for deduction, and the following method is also performed: The force associated with the measured acceleration can be generated by a known mass. This force can be electromagnetic or electrodynamic, and is ultimately reduced to the measurement of the current. This is the servo return sensor, and there are actually many vibrating acceleration sensors.
Packing the power of a double-layer PCB into a format that's a fraction of the size, multilayer PCBs are becoming increasingly popular in electronics. They come in a wide range of sizes and thicknesses to accommodate the needs of their expanding applications, with variants ranging anywhere from four to twelve layers. Layers most often come in even numbers, since odd numbers of layers can cause issues in the circuit like warping, and are no more cost-effective to produce. Most applications require between four and eight layers, though applications like mobile devices and smartphones tend to use around twelve layers, and some professional PCB manufacturers boast the ability to produce multilayer PCBs with nearly 100 layers. Multilayer PCBs with that many layers are rare to see, however, as they are extremely cost-inefficient.
12 Layer PCB Stack UP
With those irreversible trends and continuing progress of technology, many expect to see multilayer PCBs become even more abundant in the future.
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What is Multilayer PCB
Definition of Multilayer PCB Circuit Board
The multilayer PCB came into being due to the evolving changes in the electronics industry. The functions of electronics have become progressively more sophisticated over time, requiring more complex PCBs. Unfortunately, PCBs were limited by problems like noise, stray capacitance and crosstalk, and therefore needed to follow certain design constraints. These design considerations made it difficult to get a satisfactory level of performance from a single or even double-sided PCB - thus the multilayer PCB was born.
Why Do We Need Multilayer Circuit Boards?
Multilayer PCB is an integral part of most of the electronics when it comes to connecting number of electronic components on the board. Multilayer PCB helps us getting rid of the old ways of joining components where components were joined together by end to end wiring, resulted in covering more space and weight and unable to fulfill the requirements of more complex designs. Experts are in constant struggle to improve electronic design with compact shape so it provides better user experience and turns out to be less costly than its predecessors.
Now, you have got a clear idea why do we need PCB. There are already different types of PCB Board available in the market i.e. single layer board and double layer board. But, sometimes these boards fail to deliver more complex designs because of availability of less number of conductive layers on the board. Technology is evolving with the greater need of making devices cheap and low weight so they can meet the requirements in less cost and capable of performing more functions than using conventional ways of making electronic devices.
Multilayer Circuit Board Can Simplify The Design
Multilayer PCB boards came into play with the intention of constructing more number of conductive layers on the board than single-layer or double-layer boards. Multi-layer boards come with a combination of single-layer or double-layer board and give opportunity to connect more electronic components in less space. These boards are made with number of conductive layers with insulated material between them. Multilayer boards are mostly developed in rigid form, because making multilayer board in flexible form is very difficult to achieve and it also results in more cost than rigid boards. Instead of using flexible multilayer boards, most of the professionals prefer using combinations of single or double sided board that are very effective in most of cases and are cheaper than multilayer flexible boards.
Development of Multilayer PCB Board totally depends on customers'demands. With the invention of new technology multilayer circuit boards can be manufactured with up to 100 conductive layers, making complex design where more number of components are joined together. Smartphones are a great example of multilayer PCB that gives a benefit of performing more functions using single board. This refrains from spending more money on the combination of single sided or double sided boards, because they cost heavily with no guarantee of fulfilling requirements as multilayer PCB.
Multilayer PCB Board Fabrication
Multilayer boards can be manufactured with even conductive layers or odd conductive layers on them. However, it is recommended to use multilayer PCB with even layers because it results in simple design and helps in joining number of different components on the board where board design with odd layers can be costly and pertains to complex design, making it difficult to join number of electronic components on the board. Also, design with odd layers makes it very difficult twisting the board during execution of project, as odd layers are not equally distributed over the whole board structure which can damage the boards when they are subject to under heavy weights.
Some multilayer boards are manufactured so closely, making it very difficult of you to count the total number of layers with naked eye. However, still you can guess total number of layers based on the layers pattern and how they are laminated on the board. Number of different conductive layers on the multilayer boards can be termed as signal, power or ground planes. Power or ground planes are directly proportional to the number of voltage requirements on the board, if there is a need of more than voltage supply on the board, then multilayer boards come with more than one power or ground planes.
The difference between single-layer PCB, Single Sided PCB , and multi-layer PCB
Single Layer PCB vs multilayer PCB
When it comes to Printed Circuit Boards, an immediate question before design is whether to use single or multi layered PCBs for your circuit. The benefit and use of each depends entirely on what you`re intending to do. First we should define each type of circuit board.
Single layer or single sided PCB
These PCBs simply have components on one side of the board and the conductor pattern on the other side. This reason is why it`s known as a single sided or single layer PCB. Often, these are used for simpler devices as no wires can cross if the circuit is to function correctly. These are usually slightly cheaper to manufacture than multi layer PCBs.
How to identify a multilayer PCB
If you have some PCBs to hand and you`re interested in how many layers it uses, there is a way to see without causing damage to the board itself.
Firstly, shine a light into the edge in an attempt to see the copper planes, this may result in you seeing the signal traces. This will only work if the copper comes close to the edge however.
Using some sort of bright light source again, we can see if a board has inner layers even if doesn`t have blind vias. The best place to do this is [where there aren`t traces/planes on the visible, outer layers-" The areas where it`s blocked are usually copper.
Some companies or manufacturers are known to label the individual layers on the board itself, so check around the edges for numbers.
How Are Multilayer PCBs Fabrication?
4 Layer PCB Stack up
8 Layer PCB stackup
10 Layer PCB Stack UP
PCBs Manufacturing multilayer PCBs requires a specialized hydraulic press with heated platens. Initially the books are squeezed with a [kiss" pressure of 50 psi prior to being heated to 350F at 350 psi for a minimum of one hour. The assembly is then allowed to cool slowly before removal for further processing. At Omni, the maximum size of a multilayer board is 12"x 16" while the board thickness can range from 0.015"to 0.125".
The outer layers of multi-layer consist of sheets of glass cloth pre-impregnated with uncured epoxy resin (prepreg) and a thin copper foil.
The lay-up operator has already placed a copper foil and 2 sheets of prepreg on the heavy steel baseplate. Now he places the pre-treated core carefully over the alignment pins. Then he adds 2 more sheets of prepreg, another copper foil and an aluminium press plate
He builds up 3 panels on the baseplate in the same way. Then he rolls the heavy stack under a press which lowers down the steel top plate. He pins the stack together and rolls the finished stack out of the clean room into a rack.
The press operator collects 3 stacks on a loader and loads them into the bonding press. This press uses heated press plates and pressure to bond the layers of the PCB together. The heat melts and cures the epoxy resin in the prepreg while the pressure bonds the PCB together. The process is computer controlled to build up the heat and the pressure correctly, hold it and then to cool the press down. In this way we ensure a permanent bond that will last the lifetime of the PCB. Our board has 4 layers but complex PCBs for defence, avionic and telecommunications applications can have more than 50. These may include sub-assemblies of cores, prepregs and foils drilled and plated before being assembled into the final PCB.
Once the cycle is completed the press operator unloads the press and carefully rolls the heavy stacks into the clean room. Here the lay-up operator de-pins the stack and removes the top plate. He unloads each of the panels from the stack, removing the aluminium press plates used to ensure a smooth copper finish. The copper foil is now bonded in place to form the outer layers of the PCB.
Design for Manufacturability (DFM) for multilayer circuit boards
PCB design plays an important role in determining the mechanical,electrical and thermal performance of the complete electronic system. Many advanced electronic components use multilayer PCB, because it allows large number of components to incorporate on a single board, hence allowing the higher component density. Some PCBs are highly complex that make use of electronic components that are embedded on the substrate material.
Signal integrity and power integrity are two important features you must take into consideration before you intend to make PCB layout design. You must adopt following rules in order to maintain complete power integrity and signal integrity of the PCB.
Bow and Twist in multilayer PCBs is typically the result of unconventional designs.
Bow and twist is more likely to occur in asymmetric designs which can result in unbalanced stress conditions. For example, odd layer counts (3, 5 layer) are known to cause issues. Another source of multilayer PCB bow and twist comes from designs which specify variable layer thicknesses. For example, a 4 layer build specification of 7 / 28 / 21 creates more risk of deformation than a standard build. Even different circuit configurations can be influencing factors.
Multilayer PCB Thickness Parameters
Standard Multilayer Builds
Mils
per Dielectric Layer
Resulting
Thickness
4 Layer
14
/ 28 / 14
62
mil
6 Layer
7
/ 14 / 14 / 14 / 7
62
mil
8 Layer
7
/ 5 / 11 / 5 / 11 / 5 / 7
62
mil
10 Layer
4
/ 5 / 7 / 5 / 7 / 5 / 7 / 5 / 4
62
mil
So how can understanding more about the PCB multilayer assembly process help you reduce your PCB costs?
Ensure the specifications you are requesting are truly needed. While deviations from standard [tried and true" recipes are often possible, each subtle change carries additional risk, usually reflected in higher pricing, slower delivery times and occasional failure which could require a re-design. Additionally, we strongly recommend electrical testing for most multilayer printed circuit boards. Today`s software has helped designers provide consistently more manufacturable PCBs and you should expect even better results when you infuse your designs with the considerations provided above.
Multilayer PCB Disadvantages
The benefits of multilayer PCBs are numerous, making them applicable to a wide variety of advanced technologies. However, these types of PCBs aren't appropriate for all applications. In fact, several drawbacks can outweigh multilayer PCB advantages, especially for electronics of lower cost and complexity. These disadvantages include the following:
However, these issues do not diminish from the utility of multilayer PCBs. While they tend to cost more than a single layer PCB, a multilayer PCB claims many advantages over this type of Printed Circuit Board.
Multilayer PCB Benefits
From a technical point of view, multilayer PCBs present several advantages in design. These benefits multilayer PCBs present include:
These benefits make multilayer PCBs highly useful in a variety of applications, particularly mobile devices and high-functioning electronics. In turn, with so many industries turning to mobile solutions, multilayer PCBs are finding a place in an increasing number of industry-specific applications.
Advantages of Multilayer PCBs over Single Layer Alternatives
So, what do these factors mean when deciding between a multilayer and single layer construction? Essentially, if you're looking to produce a small, lightweight and complex device where quality is essential, a multilayer PCB is likely your best choice. However, if size and weight are not primary factors in your product design, then a single or Double Layer PCB design may be more cost-effective.
Multilayer PCB Applications
The advantages and comparisons discussed above beg the question: what's the use of multilayer PCBs in real world? The answer is just about any use.
For numerous industries, multilayer PCBs have become the preferred option for a variety of applications. Much of this preference derives from the continuous push across all technology toward mobility and functionality. Multilayer PCBs are the logical step in this progression, achieving greater functionality while reducing size. As such, they've become fairly ubiquitous, used in many technologies including:
Why Are Multilayer PCBs So Widely Used?
The specific applications listed above represent only a fraction of multilayer PCBs applied throughout the industry. But why are they used so widely?
Much of the favoritism toward multilayer PCBs lies in industry trends. With electronics progressing ever toward miniaturization yet multi-functional options, the internal components of those electronics must follow the same trend. While single and double-sided PCBs have proven limited in their ability to balance size and functionality, multilayer PCBs provide a comprehensive solution.
While there are several drawbacks to using multilayer PCBs over single and double-layer options, such as increased costs, design times and production inputs, these costs are becoming more accepted in today's world. Functionality is largely favored over cost, and people are willing to pay more for high capacity electronics. Additionally, as the technology becomes increasingly mainstream, production techniques and machinery will eventually become less expensive, especially as new techniques arrive in the industry.