Your Reliable Custom Multilayer PCB Manufacturer Since 2008

A multilayer PCB is needed in electronic devices for many reasons. Such as

• Multilayer PCB manufacturing process ensures reliability and high quality.
• It is supportive of rigid, rigid-flex, and flexible PCB applications.
• Multilayer circuit board assembly supports high-density designs.
• It offers simplified and stable designs.
• High-class designs because of compatibility with design software like Altium Designer, KiCAD, etc.
• Multilayer boards provide high capacity in a small footprint.
• It improves signal integrity in high-speed data transmission systems.
• Its usability in immense applications is commendable.

Heavy Copper PCB

Multilayer PCB functions superbly through its construction materials such as core, prepreg, etc. Prepreg is basically an alternating layer of fiberglass impregnated with Epoxy materials.

Here, prepreg and the conductive core materials get laminated together. The entire process is performed under high thermal pressure. Excessive heat melts the prepreg and connects the PCB layers perfectly.

Besides, dielectric materials ensure impedance control, electrical strength, flexural strength, etc. These features indicate superior mechanical and electrical properties in electronic appliances.

Functional Multilayer Circuit Board

Multilayer PCB layers vary from 4 to 40 in the case of multilayer printed circuit boards. The more the layer count increases, the more the functionality improves. The most used types of multilayer circuit boards include-

4 layer PCB

It contains two inner layers between the top and bottom layers. The stackup of a 4 layer PCB is elaborate. You can find rigid, rigid-flex, flexible, etc features in this PCB.

6 layer PCB

A 6 layer PCB contains a top signal layer, followed by an inner signal layer, ground layer, power layer, inner signal layer, and a bottom layer. It provides matched or variable impedance among these PCB layers that promote functionality to a great extent.

6 Layer PCB Board

8 layer PCB

This multilayer circuit board contains multiple signal layers with at least one power plane. It ensures amazing interplane capacitance through its ground and power planes. Besides, its stackup offers a lot of space for routing of power planes.

10 layer PCB

A 10 layer PCB comprises signal, ground, power planes, along with high-speed buses and solid grounds. This PCB has significant uses in home appliances, communication, and automotive industries.

10 Layer PCB

14 layer PCB

This is a customized multilayer circuit board that contains FR4 and high TG materials. Besides, flexible and rigid-flex PCBs have polyimide materials that ensure sufficient robustness and stretchability. They optimize the current conduction capacity and cost performance while enhancing the signal integrity.

14 Layer PCB

The basic multilayer PCB materials are copper foil, fiberglass, FR4, Epoxy resin, etc. These PCB materials are laminated in an alternating sandwich during a multilayer PCB manufacturing process.

Multilayer circuit boards provide outstanding functionality because of their construction materials. They ensure thermal and electrical features like transition temperature, CTE, dielectric strength, etc.

Basic Multilayer Circuit Board Materials

Between Surface Mount Technology (SMT) and Through-hole Technology (THT), SMT is the best option for multilayer PCB designs. Its main reasons are-

• SMT supports compact and miniature designs.
• It is cost-effective.
• SMT requires a low amount of drilling.
• It improves solderability.
• Its operation is easy and fast.

SMT In Multilayer PCB

Multilayer ceramic PCB and multilayer flex PCBs are more beneficial than single layer PCB in many aspects.  We are here with some comparison factors that differentiate these two.

High Quality  

Multilayer flex PCBs maintain a higher quality than single-layer PCBs. It is required to arrange experienced manufacturers, high-level materials, and pieces of machinery to design a multilayer circuit board.

Moreover, you have to upgrade features to have stable impedance and EMI protection. That’s why it can ensure high quality.

In the case of single-layer PCB design, you don’t need to maintain such intensive processes.

High Current Conduction

Multilayer circuit boards can handle high current loads and over-currents more conveniently than a single-layer PCB. It is possible due to high copper thickness and impedance control in different layers.

But PCB with a single layer suffers from short circuits and overloads while carrying excessive electricity.

Cost Performance

A single-layer PCB is less expensive than a 14 layer or 16 layer PCB. But the service you get from a multilayer circuit is outstanding. That’s why consumers prefer high layer counts for high-volume PCB productions to optimize the cost performance.

Complex Circuit Compatibility

Multilayer flex PCBs can handle more electric connections. So it optimizes the PCB surface with excellent reliability.

But single-layer circuit boards can’t take care of a complex design in modern electronic devices. So,  manufacturers prefer multilayer design to customize complicated circuits.

Design Stability

Multilayer stackup consists of PCB layers on top of one another. It results in a small and stable design. That’s why it is easy to accommodate them in a smaller space.

On the contrary, single-layer circuit boards can match the efficiency of multilayer circuits if you include a bunch of single-layer PCBs. But it increases the device weight and size to a large extent.

Durability

Multilayer ceramic PCB is preferable to single-layer PCB in terms of durability. A well-stacked multilayer circuit usually provides high thickness. It increases its longevity. Besides, it protects the device from external forces.

Comparisons Between Single Layer And Multilayer PCB

Multilayer PCBs have extensive applications in versatile sectors because of their amazing features and customization facilities. Their major applications include-

Medical Sector

These PCBs are widely used in heart monitors, CT scans, X-ray equipment, etc. Their improved functionality plays a vital role behind such a wide range of usability in the medical industry.

Industrial Equipment

Industrial control systems and machinery consist of multilayer ceramic PCBs because of their stable and miniature designs.

Communication

GPS, satellite applications, smart devices use multilayer circuit boards in most cases. They have high demand because of offering rapid signal transmission.

Consumer Products

Various consumer products like microwave ovens, washing machines, dishwashers, smartphones, etc become functional through this PCB. Its high durability and worthwhile size make it compatible with home appliances.

Lighting Industry

Multilayer circuits provide effective thermal conductivity and surface resistance. These features make them useful in lighting projects.

Computer Electronics

Multilayer stacks offer a space-saving component placement facility that improves their usability in computer electronics. Such as motherboard, CPU, etc.

Except for these, multilayer circuit boards are applicable in aerospace, military industry, automotive devices, etc. Besides, DIY multilayer PCBs are useful for new designers to check their device functionality.

Widely Used 6 layer PCB

The most significant multilayer PCB design guidelines include-

• Maintain an even distribution of ground and power while designing the power and ground layers.
• The adjacent signal layers should be in reverse directions.
• The inner signal layer dimension needs to be reduced
• Introduce a large number of routing channels
• Use small PCB vias and through-hole pads.
• Place thermally sensitive components away from the power source.

Multilayer PCB design brings a higher degree of flexibility and robustness. You can experience an extremely functional PCB design if you follow the rules mentioned above.

The electronic world is changing gradually. To cope with the continuous development, you need to use a PCB that offers superb compatibility with modern technologies. Multilayer PCB design provides tremendous advantages in electronic devices. Such as

• Multilayer stackup permits the connection of several circuits on a single PCB. It improves the usability of electric circuits.
• This is worthwhile for high-density component placement that improves the stability of multilayer designs.
• It minimizes production costs. As PCB stackup can place multiple electric circuits on a PCB, it affects manufacturing costs also.
• Multilayer ceramic and flex PCBs offer impressive thermal management. They can accommodate PCB thermal vias in specific locations that help dissipate additional heat from PCB layers.
• It maintains a stable impedance in different PCB layers.
• A well-stacked PCB design protects the signal layers from EMI and noise.
• Multilayer circuit upgrades the functional properties of the device.

Advantages Of Multilayer PCB

On a commercial scale, Printed Circuit Board manufacturing involves a series of extensively technical steps.

From design to development, each step is carried out according to the defined industrial standards.

The following steps are the major phases a PCB goes through before it is ready for assembling components.

Step 1: Design and Layout Development

PCB manufacturing starts with the development of the circuit’s soft layout using commercial software like Altium.

The designer creates a simulation of circuit design for extracting the CAD of the circuit.

When designing a PCB layout, one should take care of certain things, such as the route width, elements, and position. Each detail requires extensive care; even a slight mistake can cause PCB malfunctioning.

On the commercial scale, PCB designing tools are available in a wide range.

The designers usually extract PCB designs in Gerber format.

It encodes all the details, such as the number of copper layers, the number of masks required for soldering, and all other notations. When the program simulates a design, all the details can be easily inspected.

PCB Layout

Step 2: PCB Film Printing

The PCB design can be printed after all inspections are complete.

Contrary to other plans, PCB prints do not appear on a standard paper, such as the engineering drawing.

A plotter printer produces the PCB film. The plotter uses extremely accurate printing machinery to deliver an extensive film of the design.

Two ink colors represent the inner layer: The first is black ink used in copper paths and PCB circuits, and the second one is clear ink, which represents the PCB’s non-conductive areas and fiberglass base.

This mode is reversed in the case of outer layers in which clear ink refers to the copper pathway line, but black ink shows regions in which copper is removed.

Every layer of the PCB and the corresponding solder mask is given a film, so four sheets are needed for a simple two-layer PCB — one for every layer and the one apiece for each solder mask.

After the film is printed, it’s all lined up, and a hole is drilled in it, known as a registration hole. The recording hole is a reference for the later alignment of the films.

Step 3: Inner layer Processes

The copper is pre-connected to the same laminate portion after the PCB design is printed on the laminate and used as the PCB structure.

The copper is then etched to display the blueprint of the earlier edition. Then, a photo-sensitive film called resist is covered a laminate panel.

The resistance is made of a layer of photo-resistive chemicals that hardens when exposed to ultraviolet light. It enables the developers to precisely match the position of blueprint images with those printed to the photoresist.

After alignment of resist and laminate, they absorb ultraviolet light. The ultraviolet light passes the translucent sections of the film, which hardens the photoresist.

It exposes the copper patches that need to be kept as pathways. The black ink prevents light from reaching areas that are not to be hardened. This ink is removable.

Inner Layer

Step 4: Unwanted Copper Removal

Once the wanted and unwanted copper patches are markets, the unnecessary copper removal begins.

The board is submerged or treated with an alkaline solution which reduces the copper strength and eats it off.

All exposed copper is extracted in the copper solvent solution bath. In the meantime, under the hardened layer of photoresist, the desired copper is entirely safe and covered.

But since PCB comes in a variety of substrates and not all copper PCBs are the same, the process can slightly vary depending upon the concentration of copper.

Short-heightened boards need more copper solvents and different exposure lengths whereas large copper boards need more consideration in the spacing of the track.

Now that the solvent has eliminated the unwanted copper, the hardened resist safeguarding the remaining copper requires washing. Another solvent carries out this job.

With just the copper tracks available on PCB, the board now starts appearing in the desired shape.

Step 5: Board Inspection and Layer Alignment

Once the board is thoroughly cleaned, the board needs to be inspected. For aligning the inner and outer layers, the holes are used.

The developer punches the board using an optical punch to align the layers. The punch pushes in a pin through the holes to match the PCB layers.

The Automated Optical Inspection (AOI) machine is used for inspection afterward to ensure that there are no faults.

This is an extremely critical step since any defects that occur can never be resolved until the layers are permanently bound.

The machine compares the inspected PCB to an extended Gerber version for further confirmation.

After the PCB passes the AOI inspection, it qualifies for the layers’ lamination stage.

Step 6: Layer Lamination

PCB lamination is performed in two stages: the lay-up step and the lamination step.

The external part of the PCB is made from fiberglass pre-soaked with an epoxy resin.

A thin copper foil layer, which now contains gravures for the copper traces, is filled with the original substrate. When external and internal layers are ready, it is time to bind them.

The sandwiching is performed on a special press table with metal clamps.

Using special screws, each layer is fitted onto the table. The manufacturer begins by inserting pre-impregnated resin, also known as prepreg resin on the table alignment basin.

On the other side, the copper foil comes along with other sheets of pre-impregnated resin that are finished with a strip of cotton.

Now the stack is ready to be pressed once the copper press plate is in place.

The manufacturer passes it to a mechanical press and pushes it down, together with the layers. Then, the pins are forced down through the layer stack to make sure they are accurately fixed.

The PCB stack is then taken to the next press, a laminating press where the layers are adjusted.

The lamination press uses a pair of heated plates to apply heat and pressure for the stacking of layers.

The epoxy within the prepreg melts by the heat of plates, and by fusing the piles together.

Once the layers of the PCB are pressed together, a little unpacking is required. The technician has to remove the top press plate and the pins to release the PCB.

Multilayer PCB Manufacturing Process

Step 7: Drilling

Before the drilling begins, X-ray equipment is used to detect drill spots.

Registered holes are then drilled to protect the PCB stack until individual holes are drawn.

When it comes to drilling these holes, a computer-guided drill is used as per the design of the extended Gerber file.

Upon drilling completion, any copper that remains at the boundaries is extracted.

PCB Drilling

Step 8: Copper Plating

After the PCB is drilled, a chemical is used for fusing together all layers of the PCB.

Later, the PCB is bathed in a variety of chemicals after being thoroughly washed.

The panel is then coated with a micron-thick copper sheet put on the top layer and in the holes only drilled.

They are used to expose the fiberglass substrate; making up the panel’s insides before the holes are filled with copper.

The copper holes in the walls of the previously drilled holes are bathed.

VCP Plating Line

Step 9: Imaging and Photo-resistive Plating

In this phase, a new layer of photoresist is applied but only to the external layer since it still has to be imaged.

After the exterior layers are coated in photoresist and imaged, the internal layer of the PCB is plated precisely as in the last stage.

However, the outer layers receive the same process as a tin plate to guard the copper against the external layer.

Step 10: Etching

Before the external layer is etched, a tin guard is used to secure copper.

The unwanted copper is eliminated using the same copper solvent which was used earlier.

After the etching process, the PCB connections are set correctly and it is ready for solder masking.

PCB Etching

Step 11: Solder Masking

The panels are washed to ensure that they are ready for use.

After cleaning the PCB plates, an ink epoxy and a solder mask film are added.

The panels are exposed to ultraviolet light to differentiate certain areas of the solder mask.

The PCB is then put into an oven and warmed so that the solder mask may cure after the undesirable pieces of solder.

PCB Soldermask

Step 12: Surface Finishing

This stage involves chemically plating the board with gold or silver to add an additional solder capability to the PCB.

During this point, some PCBs also receive hot air pads. The appropriate level of hot air helps maintain uniform pads.

This process ends with a smooth surface finishing.

Immersion Gold

Step 13: Silkscreen

The silk-screening process labels all the critical information on the PCB.

For example, the manufacturer’s remarks, company ID number, and warning labels.

It is necessary since the PCBs have to be assembled, tested, and maintained in the future; the labeled information helps locate component positions.

Step 14: Electrical Testing

After the PCB goes through all the above steps, it qualifies for an electrical test to ensure its functionality.

Mainly, the circuit continuity and insulation tests are performed.

The continuity test checks if all short-circuit connections are closed (as needed), whereas the circuit insulation test checks the different sections of the PCBs that are designed to be insulated.

While electrical tests are primarily designed to guarantee functionality, they also evaluate how well the initial PCB design was supported in the production phase.

Automatic E-test

Step 15: Scoring and Profiling

Cutting and scoring the PCB is the last step in the manufacturing process, and then the PCB goes through a final test.

The PCB can be cut from the original panels in two ways:

First, using CNC equipment (which cuts tiny tabs around PCB edges), and the second one is using a V-groove, (which cuts the diagonal channel along the board sides).

PCB panels are usually routed and scored out with a single board or larger arrays, where necessary, to split off the board after assembling.

Till this step, the PCB has been just manufactured, it still needs to be assembled with necessary components for complete functionality.

Moreover, after assembling the PCB goes through a series of tests to ensure it functions as needed.

Evidently, PCB manufacturing is an extensively technical process.

Routing PCB Machines

Step 14: Vacuum Package

“PCB circuit board packaging” is crucial to the procedure, with moisture sensitive requirements, packaging requirements of sealing, desiccant, pumping air into a vacuum state.

But a lot of PCB company for this final process didn’t pay attention to, so a lot of the work is simple, using the PCB are not under good protection, leads to problems such as PCB board surface is easy to damage or friction.

Packing PCB

Despite having numerous positive sides, multilayer PCB offers some disadvantages also. You must have knowledge of such limitations while manufacturing a multilayer circuit board.

• It is expensive in terms of production and maintenance costs.
• A multilayer PCB stackup is time-consuming.
• Multilayer designing is a complicated task. If the printed circuit board consists of a damaged trace, its replacement or repair becomes difficult.

Flawless Multilayer PCB Design

Multilayer PCB design consists of some distinct features that make it different from a single or double-layer circuit board. You can easily identify a multilayer circuit if you consider some crucial points. Such as-

• The signal speed is high in the case of multilayer circuit boards.
• The number of layers is high
• Complex configuration
• The routing density of multilayer circuit boards is high
• They have complicated production processes compared to single-layer PCB.
• The production rate in a unit time is high for a single-layer PCB. But it is difficult to handle large-scale multilayer PCB productions.
• The lead time of multilayer stackup is long when its counterpart offers a shorter lead time.

Besides, you can identify a PCB with a high layer count by considering its functionality, parameters, speed, operating capacity, etc.

Multilayer PCB is compatible with different surface finishes that improve its solderability and resistance against corrosion. Such as-

• Electroless Nickel Immersion Gold (ENIG)
• Hot Air Solder Leveling (HASL)
• Hard Gold Finish
• Immersion Silver
• Immersion Tin

Among these metallic coatings, ENIG offers better services in a multilayer circuit board. It broadens the PCB surface to a large extent that helps handle dense designs. Besides, it resists surface corrosion and oxidation. That’s why PCB components remain functional for a long period.

ENIG In 12 Layer PCB

Multilayer PCB supports various soldering methods like SMT, THR, wave soldering, etc. Among them, the SMT soldering process offers more beneficial features to the circuit boards.

SMT Soldering

Surface mount devices are applicable for this type of soldering. Here, manufacturers insert SMDs into the top or bottom layer through welding. There is no need for using high-volume wire connections. It is essential to cover the metalization pad by using solder paste before the insertion of SMDs.

SMT soldering offers a higher degree of precision and automation. Besides, it supports high-density component placement on the board. It allows applying through-hole reflow process in the same PCB.

SMT Soldering In Multilayer Circuit Board

Multilayer PCB manufacturing machines are used for different purposes. Such as

• Drilling machines handle the drilling operations.
• Plating equipment.
• Routing machines.
• Lasering machines.
• Testing machines.
• Multilayer press machines are effective for pressing the PCB layers together. This industrial-grade machinery can apply force on various circuit board layers.
• Multilayer PCB prototyping machines are worthwhile for making a multilayer board in-home or prototyping laboratories.

There are mainly 4 types of via used in a multilayer PCB stackup.

• PCB Blind Via
• PCB Buried Via
• PCB Thermal Via
• Through-hole Via

In a multilayer stackup, buried vias connect an internal layer with the outermost layer. But buried vias and through-hole vias are used to connect two internal and external layers, respectively.

PCB Vias To Improve Signal Integrity

A multilayer PCB should be gone through regular inspection so that it can maintain its top-notch performance. There are several tests that deliver quality results concerning PCB dimensions, electrical features,  etc. The most notable tests include-

Automated Optical Inspection (AOI)

The AOI test functions by comparing photographs of multilayer circuit boards with an ideal design. An AOI machine takes 2D and 3D photos from different angles. Thus, you can identify faulty portions of multilayer circuit designs within a short period.

This test is expensive for low-volume PCB manufacturing. But it delivers reliable output.

Flying Probe Test (FPT)

Here, electrical probes get connected with specific PCB portions from different axes. Then, an inspector checks the current rating, power drops, etc. Besides, the flying probe test identifies the short connections, loose wirings, etc.

This test doesn’t require additional features and it ensures auto movement of circuit boards during tests. , loose wirings, etc.

This test is free from the hassle of additional fixtures. Again, its cost-effective features make it a good choice for small-scale PCB productions.

What Is Etching In Multilayer PCB?

Etching is a crucial part of multilayer PCB fabrication. It involves the elimination of unwanted copper from the PCB surface. Chemical process and laser technology are effective for ensuring proper etching of a 4 layer or 10 layer PCB.

In the case of chemical etching, the circuit board needs to be placed in a chemical solution. In most cases, Ferric Chloride or Cuprous Chloride is used. These solutions have enough toxicity to wash copper within a few minutes.

It is necessary to cover the required portions through a solder mask or other protections. After etching, you need to wash the circuit board and dry it properly before using it. Chemical etching is widely used because of its economical features and availability.

Etched PCB

On the contrary, eliminating copper by laser is very expensive. That’s why it is less used compared to chemical processes. Watch this video to know more about etching:

Amid an extremely competitive market in China, it is very tough to choose a reliable multilayer PCB manufacturer. You need to be highly cautious while choosing a trustworthy PCB maker. If you intend to make a good choice, focus on the following subjects that influence the PCB manufacturing process.

• Long experience of manufacturing PCBs having a higher layer count
• The capability of providing ODM and OEM services
• Custom solutions for different requirements.
• Cost-effective electronic products
• Skilled technical staff
• Certification from reliable organizations, like ISO, UL, etc.
• High-level production equipment
• Smart customer service

PCBMay deliver consumer-friendly PCB manufacturing services that improve the price-to-performance ratio. Our RoHS-certified engineers produce 6-layer, 10-layer, and 14-layer circuit boards which fulfill the conditions of IPC class 2 or 3 standards. You can rely on us to boost your business.

Multilayer PCB provides better services to electronic products compared to single or double-layer PCBs. If you want to boost your business or product’s efficiency, multilayer circuit boards are the best option.

PCBMay supplies different types of circuit boards having 4 to 40 layers. We tried to explain all the manufacturing details in simple words. If you have more queries, contact us any time. Hope for the best.