How to Manufacture High Multilayer PCB?

Requirement of high multilayer PCB (Printed Circuit Boards) has been increased dramatically with the development of electronics, communications, and computing in recent years. High multilayer count PCBs are integral to many of today's devices, allowing for the complex implementation of multiple devices in a single circuit board. But producing high multilayer PCBs is an intricate and highly specialized process and calls for state of art technology, engineering and quality control. In this article we will discuss the step-by-step process to manufacture high multilayer PCB and focus on the particular concerns, difficulties and best practices.

What Are High Multilayer PCBs?

A CB refers to some layers of conductor patterns (usually copper layers) in more than two, the layers of each layer are separated by insulating materials (resin material or other materials). These are usually at least ten-layer boards, some in high-end designs may be more than fifty layers. High-layer/multi-layer PCBs are used in aerospace, automotive, medical, telecommunications and consumer electronics industry where compactness, reliability and performance are key factors, respectively.

An important feature of a high layer count PCB is that it can host more complex circuitry, as well as keeping a compact form factor. These are boards that offer greater routing density, better signal quality and lower EMI impact, and hence are highly valuable in the world of high-speed and high-frequency design. Critical steps in the fabrication of High Multilayer PCBs

High Multilayer PCB Manufacturing is a Complex Process Making one high multilayered printed circuit board is a complex and several step process that demands precision and skill. The manufacturing process is also illustrated in detail, as per the following:

1. Designing the PCB Layout

High multilayer PCB Fabrication The first step to creating high multilayer PCB is a good design. The PCB layout is designed with the help of computer-aided design (CAD) systems – for example ADVANCE. This will comprise pin-out location of components, route of signal tracks, location of power and ground planes and so on.

Important aspects to consider in the design:

• Layer Stack-Up Design: It is imperative to calculate number of layers and their order. An optimized PCB stack-up significantly reduces signal losses and enhances EMI performance.
• Impedance control: Impedance control is important to avoid signal degradation especially for high frequency applications.
• Thermal Considerations: Efficient cooling design must be included in the design to achieve reliable performance.

Design validation with an imitation of the inducer is carried out to avoid possible problems before manufacturing.

2. Material Selection

The selection of those materials, however, is an important factor in the performance and reliability of high multilayer PCBs. Some common materials used are:

Substrate: FR4 is used in most cases but for high frequency applications, material like Rogers, polyimide, or Teflon may be recommended.

Copper Foil: High-quality coppers exhibiting high conductivity and FPCs are applied for the product in terms of conductive properties.

Prepreg & Core - The insulating materials that bond the layers of a PCB together & add strength.

The materials must be selected to fit the particular needs of the application--for example, high thermal resistance is required, low dielectric constants are demanded, or high frequency performance is needed.

3. Inner Layer Preparation

The fabrication is initiated with the inner layers. These are done as follows:

Photoresist Application The copper-clad laminate is applied with photosensitive film.

Image transfer: PCB design is transferred onto the photoresist layer by exposing to UV light. Light-affected areas become hard, while the unexposed areas are soft.

Etching: The undesired copper is chemically etched, move the copper areas behind the mask.

Inspection: Inspection of the etched layers is carried out with the help of automatic optical inspection (AOI) systems.

4. Alignment and lamination of the layers

Regions of the core are then prepared and stacked together with prepreg and core materials in a desired order once the internal layers are ready. Accuracy matters at this point in order to have all layers nicely together.

The stack is then laminated such that:

Heat and Pressure: The stack is then pressed together in a press while at high temperature, causing the prepreg to melt and form a bond between the layers.

Cure the lamination stack is cured to cure the bonds and generate a solid PCB.

 

5. Drilling

Vias are then drilled using holes drilled into the PCB to join all layers. The holes are located and sized using a high precision CNC drilling machine.

The vias in high multilayer PCBs come in the following types:

• Through-hole Vias: Go all the way through the board.
• Blind Vias: Link outer layers to internal layers, but not entirely through the PCB.
• Burried Vias: Electrical connection to internal layers without penetrating outside layers.

 

6. Plating and Copper Deposition

After the holes are isplled, the holes are plated with copper to provide electrical connection between the layers. This involves:

• Cleaning: The hole is cleaned out through which drilling debris and the like must be cleaned out.
• Electroless Deposition: Depositing of a thin copper layer inside the holes and on the surface of the board is done chemically.
• Plating: More copper is added until the copper is the correct thickness.

 

7. Imaging and Etching the Outer Layer

It is similar to the inner layers: 3.2 Outer Layers The outer layers are processed in the same way.

Application of Photoresist: A photosensitive film is coated to an exterior side.

Image Transplant: A circuit pattern is transplanted by UV light exposure.

Etching: Any copper that is not covered by the resist is etched away, leaving a patterned circuit of conductive copper.

 

8. Solder Mask Application

A layer of solder mask is used to encapsulate the PCB and its copper traces to prevent solder bridges during assembly. The process involves:

• Coat”: The board is coated with solder mask material.
• UV Exposure: The solder mask is cured with UV light.
• Cure: The board is baked so that the solder mask hardens.

 

9. Surface Finish

The exposed copper surface is coated with a surface finish to protect the copper and provide acceptability for solder. Some of the popular surface finishes for high layer count PCB include:

• HASL (Hot Air Solder Leveling): A cheaper alternative, the solderabilities is well.
• ENIG (Electroless Nickel Immersion Gold): Excellent corrosion resistance and flatness for fine pitch devices.
• OSP (Organic Solderability Preservative): Eco and pocket friendly.
•  

10. Testing and Quality Control

Testing is a very important process to guarantee the functionality and the reliability of the high multilayer PCB. Sequence tests generally are performed using:

• Electrical Tests: Checks continuity and insulation of all circuits.
• Impedance Test: Guarantees that impedance level for the high frequency signal maintains the same.
• Thermal Testing: The board is tested for its thermal performance during operation.
• Such tests are carried out with great accuracy and economy using automated test equipment.

Difficulties in the Fabrication of High Multilayer PCB

There are numerous problems that need be resolved when manufacturers produce high multilayer PCBs’ products, such as:

High precision requirement: It becomes hard to maintain the alignment and higher precision as the layers grow.

Material Selection: It can be difficult to locate materials that meet the desired performance, but are economical.

Thermal Issues: High multilayer count PCBs produce a lot of heat that needs to be dissipated.

Cost: Due to the sophistication and requirement for sophisticated equipment, high multilayer PCBs are more costly to manufacture.

Best Practices to Fabricate High Multilayer PCBs

Time to Summary of cost cost High Multi-layer PCB manufacturing Tips In order to make high multilayer PCBs, producers must use the following best practices:

Work with EMPOWERED Designers: Partner with experienced PCB designers to prepare the layout to be manufacturable.

Invest in the Latest Equipment: Utilize cutting-edge equipment for drilling, plating, and testing.

Run Strict Quality Control: Check and test at all stages of manufacturing. Select Dependable Suppliers: Find trustworthy suppliers for good quality materials.

FAQ for High Multilayer PCB

• What is the highest multilayer of PCB?
• The number of layers in high multilayer PCBs exceeds 50 for some complex designs and application specifications.

 

• What is the material for high multilayer PCB?
• Typical materials comprise FR4, Rogers, polyimide and Teflon for the substrate and high-quality copper for the conductive layers.

 

• How are holes created in high multilayer PCBs?
• Through-holes are drilled into the PCB and copper-plated to provide connections between layers.

 

• What makes high level HDI PCBs so costly?
• The intricate process and advanced equipment required, in combination with the high grade of materials used, are what make high multilayer PCBs more expensive.

Conclusion

High multilayer PCB production is a complicated and highly specialized process that demands precision, knowledge, and high-end technology. From layout, material selection, alignment of layers and thorough testing, each step is critical to the overall quality and reliability of the end product. Manufacturers are able to manufacture high multilayer PCBs to the strict standards required by today’s electronic devices by adhering to best practices and addressing challenges. With the development of technology, the requirement to use the high multilayer PCBs will become more and more significant and it is becoming an indispensable part of electronic future.