Multilayer PCB

What Is Multilayer Printed Circuit Board ?

Multilayer PCB is a Printed Circuit Board with more than two layers. Double-sided PCBs have two layers of conductivity on both sides of the PCB’s substrate. A multilayer PCB should contain at least 3 layers of conductive material or a copper layer. The layers are connected by copper-plated holes. The layers could be as long as 4, 6, 8…up to 60 layers.

The multilayer PCB can be intricate because of its design. The top and bottom sides appear identical to the double-sided PCB, but they have secured layers both on each side of the central layer. The layers are all compacted to create one PCB, which is multilayer which is joined by copper-plated holes.

JarnisTech manufactures multilayer PCBs from 4 -60 layers. In addition, we can take single-material or mixed-press materials Fr4, Rogers, Polymide, and metal Core. Please send PCB Gerbers files to [email protected], We’ll give you a quick quote!

What Exactly Are Printed Circuit Boards(PCB) ?

The printed circuit board (PCB) is an electronic device that makes use of copper conductors for electronic connections for components. The printed circuit board provides structural support to electronic parts so that they can be placed within an enclosure. The design of a printed circuit board requires a sequence of steps that is compatible with the process of manufacturing, the integrated circuit packaging, as well as the layout of the circuit board.

The majority of PCBs used for simple electronics are made of single sided or double sided ciruit board. Higher-end hardware like motherboards or computer graphics cards could need multi layers, sometimes as high as 60.

Multilayer PCB Substrate Material & Multilayer PCB Base Materials

It is possible to divide it into two types:
● PCB rigid substrate
● The flexible PCB is a substrate

Multilayer Rigid PCB Substrate

General rigid PCB substrate material is an important variety of copper clad plate. It is composed of Reinforein reinforced material which is dipped in resin adhesive through cutting, drying, forming into blanks, and finally painted with copper foil using a steel plate as mold using a hot press to perform high temperature and pressure forming. The most common multilayer board, with the semi-cured part is copper-clad sheet used in the manufacturing process of semi-finished goods (mostly glass cloth that is soaked in resin and processed through drying). Rigid PCB substrates include Aluminum PCB material that is bare, Ceramic PCB substrate material and metal core PCB material that is bare as well as FR4 bare materials and a special PCB substrate.

Base Material of Multilayer Flexible PCB

Flexible circuits (also often referred to across the world as flexible circuits as well as Flexible printed circuit boards, Flex prints, as well as Flexi-circuits) are part of the interconnection and electronic family. They are made up of an insulating, thin polymer film with circuit-related patterns attached to it and typically come with a thin layer of polymer to shield the circuits of conductors. This technology has been utilized to connect electronics since 1950 in one way or in a different form. It’s now one of the main interconnection technologies used in the production of some of the latest electronic devices. Flexible PCB substrate materials include polyimide (PI )PCB substrates and PET PCB substrates.

Which PCB Substrate Material Do You Decide To Use To Create Multilayer Circuit Boards ?

Generally speaking, in the manufacturing process of multilayer PCB board, selecting which types of PCB substrate to use depends on the requirements of our clients.

Aluminum Base Materials&Metal Core Base Materials

If this circuit board was designed for the lighting companies, the customer would select an aluminum base material or a metal Core Base Material. What is the reason you chose aluminum boards and metal core as the base material？ Why not choose the FR4 base substrate as the base material?

From the analysis of performance, The performance of the metal base material is the most reliable choice. The electrical conductivity and thermal stability of aluminum plate base materials are higher than traditional RF4 base materials; however, the cost is higher than the FR4 substrate. If the money is enough cases, customers tend to choose the base material of aluminum plate base material as multilayer circuit board production. Why not use metal core base material, since the metal core base material is more expensive. As far as the design requirements of the customer are concerned, the aluminum plate is the best base material to choose, so we can save the customer more money. At the same time, we can satisfy the requirements of the design specifications. Of course, if the person who initially developed the circuit board’s specifications is destined to use the substrate of the soft board, We will, in accordance with the requirements of the customer in relation to substrate materials, produce the customer needs of the circuit board.

Multilayer Flex PCB Base Materials

As a general rule, multilayer flexible PCB boards need different types of substrates than ordinary ones since some of the performance parameters of ordinary substrates don’t meet customer design needs. As a substrate, most customers prefer ordinary Polyimide (PI) or PET for simple single-sided and double-sided flexible circuit boards.

However, if the design is 4 layer flex circuit board, then it is considered a high-end product, and high-end products require a high level of performance parameters of base materials. A normal soft circuit board base material cannot meet the demands of the customer.

Therefore, the customer will explicitly specify the brand of base material they need in the PCB data, which will be communicated to the circuit board manufacturer. If the customer sends us an email, our sales staff will pass along the customer’s requirements to our procurement department, and after the procurement and production times are determined, we can provide an exact delivery date for the board.

A traditional FR4 multilayer circuit board base material is available in many forms, the domestic one of the most commonly used KB PCB bare substrate materials and GB; however, if the customer design PCB circuit board is intended for aerospace, medical equipment, or high-end consumer products, including mobile phones, air conditioners, refrigerators, etc. And even some high-precision industrial products and military products.

Most of the customers will pick a few more famous boards, like Rogers bare material, Isola, SY, Panasonic, Taconic PCB, and Teflon board, as well as some high precision industrial products, military products, For example, Rogers bare material, Isola, SY, Panasonic, Teflon, etc. These planks and segmentation are out of many models’ specifications. Customers already know at the beginning of design what board sheet they need and what specifications they need. Experienced PCB designers will inform the PCB suppliers about PCB design materials. If not, our sales staff will follow the recommendations from our engineering department and give valuable suggestions to the customer in order to fulfill the board customization needs of the customer exactly.

Rigid-flex PCB Base Materials

Regarding the PCB bare substrate materials discussed in the previous three points, there’s a special PCB Bare materials that are composed of a flex circuit board and a rigid circuit board. It is referred to as rigid-flex boards, which could also be described by the term mixed PCB. Mixing PCB boards is not just rigid-flex, but also our typical mixing boards are also ordinary RF4 and Rogers and other brands that are well-known mixed together. If we examine the small details of our lives, we’ll see that the circuit board of a mobile phone, a popular consumer device in everyday life, it is constructed of PCBs made of rigid-flex. For this type of circuit board, how do we choose the bare PCB substrate? It is actually easy, an FPC circuit board uses flexible base material, a rigid circuit board uses rigid base material, and we will comply with the customer’s requirements if the customer requires a specific brand base material model so that we can manufacture a high-quality circuit board that meets the customer’s requirements.

Ceramic PCB Base Materials

A specific PCB substrate material is known as ceramic PCB substrate. As the development of electronic technology in a variety of areas of application highly integrated circuit boards have become a trend that is inevitable and highly integrated packaging modules requires a good thermal dissipation and bearing technology. The drawback of traditional circuit boards such as CEM-3 and FR-4 with respect to TC(thermal conductivity) is now a limitation to the growth in electronic technologies. The RAPID advancement in the LED industry over the past few years has also led to more stringent requirements regarding and the TC index of the PCB. In the realm of LEDs with high power, ceramic and metal materials that have excellent heat dissipation properties are typically used to create boards for substrate. Thermal conductivity for aluminum substrates that have the highest thermal conductivity is typically between 1-4W/M. K The heat conductivity in ceramic substrates could reach 220W/M. K, based on the procedure of preparation and the material formula. The base material is distinguished by high thermal conductivity, air tightness, excellent insulation, and good electric performance for the board it is a popular choice for PCB designers and engineers appreciate.

In contrast to the conventional FR-4 (wave fiber), Ceramic materials are distinguished by having excellent high-frequency and electrical performance. They are also very high in electrical conductivity, thermal stability as well as chemical strength.

Considering the thermal stability and performance of organic substrates, it is the ideal material for packaging large-scale integrated circuits and power electronics modules.

In reality, the ceramic plate substrates are divided into two kinds, aluminum Nitride ceramic board(AIN) and Al2O3 Alumina Ceramic. The process used to make their surface is Immersion silver, gold, OSP and nickel palladium gold. Because of the uniqueness of the PCB’s substrate made of the ceramic performance, the time to manufacture it generally is much longer than that of the traditional circuit board cycle is lengthy similar to the traditional cycle of multilayer circuit boards takes seven to ten working days. The ceramic plate, it could take up between 14 and 15 working days due to the production of ceramic plate technology. Compared to traditional circuit boards, the process becomes more complex.

JarnisTech company is a known multilayer circuit board manufacturer in Shenzhen of China. Whatever circuit board you require, we are able to produce top-quality circuit boards. An experienced engineering team and the latest equipment ensure the quality of our products and timely service to the client; Contact us today, and we’ll get back to your request as fast as possible. Additionally, it offers the most professional assistance in addressing multilayer circuit board-related concerns.

Copper foil of multilayer circuit board and multilayer PCB Substrate Material Thickness

We have copper foil available in the following thicknesses on hand:

The following FR4 prepregs are on hand:

Common lamination structures for multilayer PCBs and the Stack-Up of multilayer PCB:

Multilayer PCB Manufacturing Process

Cutting

Cutting refers to the procedure of cutting the copper-clad board into a piece that can be produced in the manufacturing line. Typically, the materials bought are available in these dimensions: 36.5 INCH x 48.5 INCH, 40.5INCH X 48.5 INCH, 42.5 INCH X 48.5 INCH and so on. PCB designers as well as PCB production engineers constantly think about how to make the most utilization of PCB raw materials during the manufacturing process.

Inner Dry Film

The dry film inside is the method of transfer of the inner circuit design onto the board of PCB.

For PCB production, we’ll discuss the idea of graphics transfer, since the creation of graphic conductive images is the basis for PCB manufacturing. This is why graphics transfer is vital to PCB production.

The dry layer of the inner layer comprises a variety of processes like stacking of the inner layer exposure and development and also the inner layer the etching. The film inside is a photosensitive film that sits that is placed on the outside of the copper plate. The film will cure once it is exposed to sunlight, creating an insulating film on the board. Exposure development is the process of exposing the board to the film fixed. The light-transmitting portion is then cured, while the area that does not transmit light is dry film. After the development process the dry film that is not cured is removed and the board that has the cured protective film is then etched. Following the removal of the film the inner circuit design is transferred onto the board.

Black Oxidation

The reason for the browning and blackening process is:

● Remove any contaminants, such as oil and impurities from the surface.

●  Increase the area of the foil, which increases the area of contact with the resin. This allows for the complete diffusion of the resin as well as the development of a stronger bonding force.

●  Transform the non-polar copper layer into the surface by using the polar CuO and Cu2O and enhance your polar bonds between copper and resin.

●  The surface that has been oxidized isn’t affected by moisture when temperatures are high, thereby reducing the risk of delamination of copper foils and resins.

The boards with the inner layer wiring have to be burned or blackened prior to when they are laminated. It’s to oxidize the copper layer’s surface. It is generally generated Cu20 has a red color, CuO can be black. Therefore Cu20 inside the layer of oxide is mostly known as browning. Cuo is usually referred to as blackening.

Lamination

The process is joining circuit layers to form an entire system by using B-stage prepreg. The bonding process is accomplished through the interdiffusion process and the diffusion of large molecules across the interface, which in turn interweave.

Purpose: The discrete multi-layer board and adhesive sheet should be pressed together into a multi-layer board of the required number of layers and thickness.

Typography

The copper foil or sheets for bonding (prepreg) and the inside layer boards, stainless steel insulation board, kraft paper the outer steel layer and many other materials are laminated in accordance with the requirements of the process. If the board is over six layers, it requires setting prior to the process.

Lamination Process

To bond the substrates and fill the gap in the stacked circuit boards, send them to the vacuum heat press. As the machine uses thermal energy to melt the resin, the resin sheet bonds to the substrate and fills the gap.

For designers, the primary factor to consider when considering lamination is symmetry. Since the board is subject to temperature and pressure as it is laminated and there will be pressure on the board post the lamination process. If it is not even on the two sides of the board, then the strain on both sides will be different, which causes the PCB to bend on one side, severely affecting how it performs on the PCB.

Furthermore, even in identical planes, in the event that copper distribution has uneven distribution, this can cause the flow rate of resin at each spot to be different, which means you will find that the region that has less copper will be a little thinner and one of the areas where copper is greater will be a little thicker.

To avoid these issues, aspects such as the uniformity of the distribution of copper, the design and layout of the blind buried holes，the symmetry of the stack，etc. It must be considered in detail during design.

Mechanical Drilling

Mechanical drilling uses drills to cut at high speed to create a through-hole onto the PCB.

Metalize the Through Hole

The circuit board is made up of glass fiber, copper foil as well as epoxy resin. When it comes to manufacturing the cross-sectional area of the hole’s wall after the substrate has been drilled is comprised of the previous three components.

The purpose of metalizing the hole is to solves the issue that covers the entire cross-section in uniform thermal shock-resistant copper alloy.

The process is split into three parts: one for the process of decontamination, two for facilitate the chemical plating through-hole procedure and three step for the copper thickening process.

Plated Through-hole and Thickened Copper

The metallization of holes involves a concept of capability, thickness-to-diameter ratio. Thickness-diameter ratio is the ratio of the thickness of the plate to the aperture. As the board thickens and the pore size decreases, the chemical liquid has a harder time entering the drill hole depth. A thin coating is necessary. There is a small open circuit in the drilling layer. At this time, when the voltage increases and the board is impacted under various harsh conditions, the defects become completely exposed, resulting in a broken board circuit, and the specified work cannot be carried out.

So, designers must know the technical capabilities of the manufacturers of boards at the right time. Otherwise, the proposed PCB is difficult to produce. It should be noted that the thickness-to-diameter ratio must be considered not only in the design of through holes but also in the design of blind buried holes.

Pattern Plating and Dry Film

The graphic transfer on the outer layer is very similar to the graphics transferred in the inside layer. Both employ photosensitive dry film and photographic techniques to print circuit designs on the board. The main difference between the dry film is the outer layer and the internal dry film:

● If subtraction is used, the external dry film will be identical to the inner dry film, and The negative film is used as the plate. The dry film that has been cured in the circuit board constitutes called the circuit. As the circuit pattern is protected by the film, the uncured film, after acid etching, is removed, leaving the cured film on the board.

● If the standard method is used, that outermost layer of the dry film is composed of positive films. The cured portion of the film is called the non-circuit portion (substrate space). Once the film that is not cured has been removed the pattern plating process is carried out. If there’s a film it can’t be electroplated, or if there isn’t a film the film is then plated with copper, and after that, tin. After the film is removed the alkaline etching process is carried out before the tin is taken away. Due to the tin’s protection, the circuit pattern remains on the board.

Wet Film Solder Mask

The process of soldering mask involves the addition of an additional layer of solder mask over the entire surface. The solder mask layer is known as Solder Mask or Solder Mask Ink which is also known as green oil. Its main function is to avoid tin buildup on conductor lines or other conductor lines. It also helps to stop short circuits in lines because of chemicals, moisture and other chemicals. At the same time, it also to prevent disconnection due to PCB poor production and PCB assembly processes, and resistance to harsh environments.

Presently, this layer of ink utilized by PCB manufacturers is primarily made up of ink with a photosensitive liquid. The principle of production is like Circuit Pattern Transfer. Film is also used to stop the light exposure and then transfer the pattern of solder to the PCB’s surface.

The process in detail is like this: Pre-treatment ->coating one-> pre-bake-> exposure> development -> UV curing ->thermal curing.

An associated process parameter is the solder mask file, which includes solder mask alignment accuracy, green oil bridge size, fabrication methods, and solder mask thickness. In addition, the quality of solder resists ink also affects surface treatment, SMT placement, preservation, and service life. At the same time, it is an important process in PCB production because of its long production time and variety of production methods.

Presently, the process of designing and manufacturing vias is the focus of numerous designers. The evident issues that result from the solder mask are among the principal items that are scrutinized by PCB quality inspectors.

Silkscreen

Since the accuracy requirements for characters are lower than the requirements for solder masks and wiring, The characters printed that are printed on PCBs are essentially screen printed. In the process, Initially, the screen for the printing plate is created according to the character film, then the character ink is printed onto the plate with the screen, and lastly, the ink is dried.

Surface Finished

PCB surface finish is the process of artificially creating an outer layer that has different physical, mechanical, and chemical characteristics of the substrate over the parts and electrical connections that are on the PCB. If the surface treatment of the circuit board is not carried out, it will be easy to form false welding and virtual welding, and in severe cases, the pads and components may not be able to be welded. The goal of treating the surface is to guarantee good electrical and solderability on the PCB.

The primary purpose of the treatment of surfaces is to guarantee excellent solderability and electrical properties.

Profiling

Until now, the PCB we have produced has always been in the form of a PANEL, that is, a large board. Since the manufacturing for the whole board is completed, we must segregate those graphics that are delivered from the main board in accordance with (UNIT delivery, or set delivery). In this stage, we’ll use this CNC machine to perform the processing of the graphics in line with the pre-programmed software. The contour edge milling and strip milling process will be finished in this stage. In the event of a VCU, the V-CUT process must be added. The parameters for capacity involved in the process include the shape tolerance, size and chamfer and the size of the inner corner. The distance of safety between the shape as well as the edges of the boards should be considered in the design.

E-test

The electronic test is an electrical performance test performed on the PCB. It is commonly referred to as”the “on” as well as the “off” examination for the PCB. Of the various electrical test methods employed by PCB manufacturers such as needle bed tests, flying probe tests are the most popular.

Needle beds are classified between general needle bed networks as well as needle beds that are specifically designed for use. This needle bed may be used to analyze PCBs with various network structures. However, its equipment is rather expensive. The needle bed that is dedicated is a needle bed specifically designed for a specific PCB and is only compatible with the PCB.

The flying probe test is an instrument called a flying probe that checks the integrity of each network by moving the probes (multiple pairs) across both ends. Because the probes are able to move around freely and move freely, the test of flying probes is also an overall test.

Final Inspection

The most common methods of inspection are:

Optical Inspection: It’s an instrument used to detect typical defects that occur in the welding process based on optical principles. The AOI test is a brand new kind of testing technology and is evolving quickly and numerous companies have introduced AOI testing equipment. In the event that automatic detection is used, the machine examines the PCB using the camera, captures the image, and then compares the solder joints that are tested against the parameters that are qualified in the database. After processing the image, you can check for any defects on the PCB and then mark the defect using the display or the automatic indicator. Repairs can be made by the maintenance staff.

Target Inspection Confirmation: Visual confirmation of inspection to verify or remove some genuine and false flaws.

Visual Inspection: fix or tear out the defects that have been confirmed and categorize the various layers.

Package

The primary packaging types are Moisture-Proof Packaging, Anti-Static Packaging and Anti-Vibration Packaging but the typical packaging utilizes vacuum packaging.

JarnisTech focuses on one-stop PCBA manufacturing solutions that are intelligent, employing artificial intelligence and big data technology. It is independently created China’s first PCBA modular intelligent manufacturing platform, which combines electronic components and product prototypes production, trial production, as well as mass production to supply clients with top-quality, high-efficiency service.

Benefits of Multilayer PCBs:

Size: Multilayer PCBs offer an additional benefit due to their size being small, which is why they can be used for a wide range of applications.

Lightweight: Small PCBs are also lighter and have smaller weights. This is especially the case due to the fact that single sided and double-layered PCBs require numerous connectors which increase the weight and limit mobility.

Reliability: Typically multilayered PCBs is the best in terms of reliability and of top quality.

Durability: Multilayer PCBs also have the highest durability because they are designed to stand up to the pressure and heat which is put on them.

Flexibility: In assemblies that utilize construction techniques that are flexible, a flexible multilayered PCB is a good option, especially for applications that require some bend.

Powerful: Multilayer PCBs usually have high density and offer larger capacity and speed.

Single Connection Point: Multilayered PCBs offer single connection points that make them desirable for gadgets where size and weight are important considerations.

Multilayer printed circuits are the result of the development of electronic technology with high-speed, multi-function large capacity, and low volume. With the continuous advancement of electronic technology, particularly the vast and extensive use of  large-scale integrated circuits, the multilayer printed circuits are rapidly evolving according to the directions of high precision,high layers,high density, high layers, tiny lines and small holes, buried holes, blind holes, high plate thickness to aperture ratio, and other technologies to meet market demands.

The Disadvantages of Multilayer PCB

Expensive Cost: If you’re an individual with a tight budget take into consideration the total cost of the project prior to choosing the multilayer PCB.

Manufacturing Time Is Long: If you’re a time-conscious person or are pressed for time to finish your project, this can be one of the major reasons.

Complex Repair: Multilayer PCBs require an additional complicated repair procedure in comparison to other PCB types.

Testing Methods That Are Highly Reliable: As a result, you must be aware of these limitations before making a final decision. If these limitations matter to you, please contact us what they mean to you and we’ll offer professional assistance to resolve your multilayer PCB problem.

Applications of Multilayer PCB

Multilayer PCBs are now the most popular choice for a variety of applications. The most popular multiplayer PCB applications are:

Consumer Electronics

The consumer electronics category is the main device that utilize multilayer PCBs. Because the majority of electronic devices used by consumers, such as laptops, smartphones and smartwatches multi-functional, they require refined PCBs.

Computer Electronics

The majority of electronics utilize multilayer PCBs because of their small size and their high performance. They are also suitable for various techniques in the field of computers.

Telecommunications

Electronic devices for communication like GPS signals transmission and satellites make use of multilayer PCBs. The reason is due to their endurance and function.

Medical Devices

Multilayer PCBs can also be found in a variety of medical devices because of their size and compact capabilities, and heavier than single-layer PCBs.They are utilized in CAT scanners as well as X-ray equipment, heart monitors, and other medical testing equipment.

Military

Because multilayer PCBs are long-lasting, lightweight, and light in weight, they have remarkable performance, and they are popular in the military field.

Automotive

The majority of cars depend on electrical components in the modern age. Automobile manufacturers use multilayer PCBs in GPS devices, computer systems, headlight switches, computers as well as many other devices.

Because they are strong and compact multilayer PCBs can be used for a variety of purposes and are suitable for all cars.

Aerospace

Like automobiles, planes and jets also have electronics and computers that make use of PCBs. Therefore, multilayer PCB is the ideal option for aircraft.

Other

Multilayer PCBs are employed in different industries, such as the science industry, research security, as well as appliances for homes.

JarnisTech Is a Leading Multilayer PCB Manufacturer in China

As technology advances that have led to the development of multilayer PCBs will continue to increase. Numerous contract manufacturers have made investments in these new trends and are focused on offering high-quality fabrication solutions in the field of Multilayer PCBs. JarnisTech is working to solve the biggest problems encountered during the manufacturing of Multilayer PCBs with efficiency with the most modern manufacturing process and machinery. You can create a high-performance multilayer PCB through collaboration with JarnisTech, which has expertise in dealing with these challenges and has had success manufacturing Multilayer PCBs.