Whether you possess a curious nature or have ever disassembled the electronic equipment in your vicinity, you will likely come across a green metallic component known as a printed circuit board (PCB). With the continuous development and innovation in electronic technology, the demand for compact, lightweight, and high-performance devices has become paramount, and the role of the PCB in achieving these objectives cannot be understated.
Currently, various forms of PCBs are utilized, including rigid PCB, flexible PCB, rigid-flex PCB, and semi-rigid PCB. Among these, rigid board is the most prevalent. In comparison, rigid PCBs are cost-effective, reliable, and easily processable, making them a preferred choice for electronics manufacturers. In this article by TechSparks, we will delve deep into the subject and explore strategies for enhancing the cost-effectiveness of your electronic projects.
Importance of Rigid PCB Board in Electronics
Features of Rigid PCB
When a rigid printed circuit board is manufactured, a layer of solder mask is applied to its surface as a protective film. This solder mask significantly enhances the PCB’s reliability by effectively blocking current and providing resistance against mechanical wear.
The inherent stiffness of PCB prevents them from being easily bent or folded like flexible circuits. Any attempt to bend a rigid PCB board may result in component detachment or even cracks.
To accommodate more components and enable advanced functionalities, circuit boards require increased wiring. This is often achieved through a multilayer structure formed by stacking multiple layers. However, achieving such stacking is challenging and can raise manufacturing difficulties and failure rates. In contrast, manufacturing multilayer rigid PCB is relatively easier, with some factories capable of producing over 100 layers.
Printed circuit boards have been in existence for nearly a century, and manufacturers are highly familiar with this types of circuit board, especially single-layer rigid PCB. Designers have to consider fewer factors when designing circuits using rigid PCBs, allowing them to meet project requirements more efficiently.
The strength, ease of design, and manufacturing process enable rigid boards to withstand extreme application environments, such as corrosion, high temperature, humidity, etc. Rigid printed circuit boards can maintain performance over a long period of use by selecting appropriate materials and designs.
These are compatible with a wide range of testing methods, including AOI, X-ray, electrical testing, and more. These boards can be easily subjected to various testing procedures as long as the test engineer completes the necessary programming.
In the manufacturing and usage processes, it is inevitable for printed circuit boards to experience failures. However, the use of traditional plug-ins and connectors in rigid PCBs simplifies the component replacement process. Only a basic understanding of desoldering procedures is required, without the need for specialized techniques or tools.
As an indispensable tool in various aspects of human life, work, and entertainment, computers have undergone remarkable advancements since their inception. Do you still recall the computers from the year 2000? They were massive machines with a rigid appearance and substantial physical dimensions. However, today’s computers have evolved to be mere centimeters or even millimeters thick. The development of printed circuit boards has played a pivotal role in this transformative phenomenon. While we are quite familiar with the PCB used in computers, there is often a misconception that the CPU itself constitutes a circuit board. In reality, the CPU is just one component integrated onto the circuit board, which manufacturers install through assembly processes to create the rigid PCBA board.
As the central component of a refrigerator, the rigid PCB plays a critical role in integrating numerous electronic components to enable essential functions like cooling and lighting. When a household refrigerator malfunctions, it is highly likely that these circuit boards are the primary source of the issue. Upon connecting the power supply, the current flows through the circuit structure, reaching the PCB’s LED when we open the refrigerator door. Furthermore, the refrigerator’s rigid PCB also incorporates the cooling cycle and the defrost heater, which operate periodically. These components monitor and control temperature settings, triggering power conversion to optimize energy efficiency when specific conditions are met.
The lighting system offers a wide range of options, extending beyond traditional incandescent lamps to include PCB with integrated LED. Traditional incandescent lamps feature a built-in metal filament that emits light when energized by current. While these lamps adequately serve everyday lighting needs, they may fall short for specific requirements and large-scale commercial settings. As a result, LED lighting has emerged as the prevailing choice. These lighting systems utilize PCBs to support and interconnect LED chips, power drive circuits, and other essential electronic components, enabling enhanced integration, efficiency, and control capabilities. Examples include vibrant flash lights in nightclubs and powerful spotlights at concerts. For high-power applications, employing aluminum substrates as the rigid PCB substrate material ensures superior heat dissipation performance.
Rigid vs Flexible vs Rigid-Flex
|Fixed an unyielding structure, lacking the ability to bend or deform. Once manufactured, they maintain their original shape and cannot be easily adapted to alternate configurations.
|Also known as FPCB, is composed of a pliable insulating polymer film with conductive circuit traces. They establish reliable connections in confined spaces or areas that necessitate bending or flexing.
|Involves the strategic planning and interconnection of both rigid and flexible segments. While the rigid portion serves as a supportive backbone, the flexible portion accommodates circuits alongside FR4 material.
|Strong and can not be bent, with a simple design without further consideration.
|The biggest feature is that it can be bent and folded, and it is difficult to design a multi-layer structure.
|Combining the properties and characteristics of rigid and flexible boards.
|Production & Price
|It is not easy to fail during production, and the wide range of materials makes the price relatively lower.
|It is a circuit that is more difficult to build a multilayer board and needs to be repaired because it is prone to failure during production, and the price is between the three.
|Because the production process is more cumbersome, its price is the highest.
|Glass fiber cloth substrate (FR-4), metal substrate (aluminum, iron, copper), polymer material (PI, PA)
|Polyimide (PI), Polyamide (PET), Polyamide, Polyester (PET)
Rigid Circuit Board Stack Structure
Choosing the appropriate stacking structure is crucial for optimizing performance in various applications. It’s important to consider that fewer layers can offer advantages due to reduced manufacturing complexity and cost. In the case of multilayer rigid PCB, the layers are interconnected using adhesives and subjected to high temperatures. These layers typically include:
- Substrate Layer: This layer is a core component of the PCB and resides within the multi-layer structure of the rigid board. It facilitates electrical connections and provides support to the circuitry. The substrate layer is further divided into inner and outer layers. The inner layer separates insulating layers to form multiple electrical layers, while the outer layer is situated on the top and bottom of the PCB, enabling external connections and safeguarding the circuit. High-quality materials such as FR4, phenolic resin, and epoxy resin are commonly used for the substrate layer.
- Copper Layer: In the manufacturing process, the copper layer is created through copper plating. It is categorized into inner layer copper and outer layer copper. Inner layer copper resides between the inner substrate layers and is responsible for forming wires, signal transmission paths, and ground planes within the circuit. Outer layer copper, situated on the top and bottom of the circuit structure, connects circuit components, external connectors, pads, and more. Copper thicknesses, typically 1 oz (approximately 35 μm) and 2 oz (approximately 70 μm), can be chosen based on specific requirements and PCB copper thickness guidelines.
- Solder Mask: While rigid PCB is reliable and robust, the circuit patterns themselves are delicate, and even minor scratches can result in PCB short circuits. To address this, a solder mask is applied to the PCB’s surface. The composition of the solder mask inks may vary depending on the manufacturer.
- Silk Screen Layer: Also known as the marking or character layer, the silk screen layer is positioned above the solder mask layer. It includes component identification, polarity indications, reference lines, product models, manufacturer logos, and more. Its purpose is to assist in PCB assembly, aid in identification during installation and maintenance, and provide positioning references. Bright colors such as white, yellow, or black are commonly used for enhanced visibility and identification.
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