Printed Wiring Board vs PCB: A Deep Comparison of Both Boards

Circuit board with assembled components

We often use abbreviations and acronyms in the electronics design and circuit board manufacturing sectors, making it essential to know and understand these terms. Among the most frequently used terms in the fabrication of electrical devices are PWB (Printed Wiring Board) and PCB (Printed Circuit Board). These two definitions have even given rise to discourse, as they are sometimes used interchangeably within the electronics industry.

In this article, we will cover how to differentiate PWB from PCB. These terms can be confusing, so it is essential to know them both. Read along as we discuss the similarities and distinctions between the two to help address the questions you may have about PWB and PCB.

Introduction to PWB and PCB

Understanding the Basics

PWB and PCB stand for Printed Wiring Board and Printed Circuit Board, respectively. These terms refer to the boards that provide the physical support and electrical connections for electronic components. While they are both common in electrical and electronic devices, they have distinct differences. Let us break down some key areas to further grasp these overlaps and differences.

Historical Context

The distinction between PWB and PCB can be traced back to the historical development of these technologies. In the early days of electronics, PWBs were the primary means of interconnecting components, and the term “printed wiring board” accurately described their function. As technology advanced and electronic devices became more complex, the need for more sophisticated interconnections led to the development of PCBs, which incorporated multiple layers of conductive traces and embedded components.

PWB vs. PCB Technology

PWB Technology

PWB refers to a board without circuitry in an electronic device, utilizing an epoxy glass substrate without any printed components. It is an earlier technology, where in order to provide conduction-insulating surfaces between conduction-enabling traces, the materials are etched during the production process to create connections. It involves manually drawing and etching circuits onto the board and attaching components from point to point, in accordance with a specified design, resulting in an electronic circuit that can be used to create electronic devices.

PCB Technology

PCB technology is more advanced and involves using a computer to design and create circuits on the board. PCB fabrication typically employs an insulating board with interconnected wires. Elements are then printed in a predefined design from point to point on a dielectric substrate. The size and spacing of the conductors profoundly affect how the circuit operates more than simply a point-to-point connection.

Key point: PCBs can be more complex and densely packed with components than PWB assembly. They are composed of elements connected by conductive tracks, pads, and other features etched from copper sheets laminated onto a non-conductive substrate.

Materials Used in PWBs and PCBs

Conductive Layers

Copper, silver, and gold are popular PCB materials to provide a signal transmission channel for the conductive layer. While gold has the best conductivity with the least resistance, its inflated cost limits its application. Copper is favorable for most PWB and PCB applications as it is more economical with strong conductivity, among other advantages. The copper tracks can be applied directly onto the board by a process known as ‘etching’, or pre-made copper foil strips can be stuck onto the board.

Non-Conductive Layers

A low-conductivity substance makes up the non-conductive layer. This layer usually utilizes FR-4, a composite epoxy material, and ceramic. Manufacturers commonly use FR-4 in a range of variations to improve its dielectric performance. Ceramic design substrates, on the other hand, are ideal for high-power applications due to their increased heat conductivity rate.

Prepreg Substance

The prepreg substance is another typical material in PWBs and PCBs. The prepreg keeps the layers together, like the board core. Fabricators use resin-impregnated fiberglass, wherein when heated, it softens and binds to the layer surfaces before hardening and reinforcing a bond when cooled, which also helps to reduce vibration and shock damage.

Solder and Coating

Manufacturers also utilize materials like solder on these circuit boards. Solder is a substance composed of tin and lead, that manufacturers often use in component attachment to help preserve the copper from oxidation. The conductive traces may be coated to avoid corrosion using materials like gold, nickel, silver, and tin, providing additional protection from dust and moisture.

Key point: There are many different materials that manufacturers use in the fabrication of PWBs and PCBs, offering varying degrees of insulation and heat conductivity. Common elements include fiberglass or plastic, copper tracks for electrical pathways, adhesive for holding components together, and a protective coating for dust and moisture resistance. The choice of material depends on the intended use of the board and the requirements of the electronic components it will support.

Application and How It Can Affect Your Choice between PWB and PCB

PWB Applications

PWB serves as a foundation and framework for components that are wired together manually or with cables. It can involve soldering, crimping, splicing, or other wiring methods. As it allows you to move and re-route the wires over time, it is easy to make changes to the design without replacing the entire board. Hence, PWBs are preferable in projects where flexibility is a crucial factor.

PCB Applications

PCB architecture employs automated processes like etching and plating. The components are mounted directly onto the board instead of being wired separately, allowing for more significant numbers of components to be connected in a much smaller space than what would be possible with PWB. This makes them more reliable because there’s no need to worry about loose connections due to wear and tear over time. However, making changes to a PCB design requires completely replacing the board since all the components are embedded into it permanently. PCBs are suitable for projects that require high accuracy and repeatability, with minimal maintenance needed over time.

PCB with immersion gold surface technology

PWB, PCB, and Other Related Terms

Terminology and Usage

Generally, PCB encompasses the entire circuits on a board, while PWB refers to the board itself. The distinction between the two is subtle, to the point that there is no official “correct” terminology. Geography also plays a role in term usage. In the US electronics sector, the terms PCB and PWB are often interchangeable. PWB is an earlier term for boards in the early days of the tech industry. Eventually, the term came to characterize the functions of circuit architecture. While the term PCB is common in the prevailing US electronics sector, modern Japan adopts the term PWB. PCB was more prevalent when the technology sector initially emerged in Japan. However, because PCB also stands for “polychlorinated biphenyls,” or poison, the term PWB has become preferable. Hence, both terms occur regularly in documents and articles from various periods and locations.

Related Terminology

Aside from PCB and PWB, you may also want to be familiar with PCBA (Printed Circuit Board Assembly), CCA (Circuit Card Assembly), PCA (Printed Circuit Assembly), and PWA (Printed Wire Assembly). These terms are also used in relation to printed circuit boards.

• PCBA (Printed Circuit Board Assembly): When a PCB is assembled, it is referred to as PCBA or PCB assembly.
• PWA (Printed Wire Assembly): An old term for PCB assembly, often known as PCBA.
• CCA (Circuit Card Assembly): Technically the same as PCBA; however, CCA is a less common term.
• PCA (Printed Circuit Assembly): The same as PCBA, although seldom encountered nowadays.

Comparing PWBs and PCBs

Design Complexity

PWBs are typically single-sided and are suitable for simpler designs with lower component density. In contrast, PCBs can be single-sided, double-sided, or multilayer, offering greater design flexibility and higher component density.

Manufacturing Techniques

PWB manufacturing involves simpler processes such as photolithography or screen printing for pattern generation and chemical etching for trace formation. In contrast, PCB manufacturing requires more advanced techniques like laser direct imaging (LDI) or inkjet printing and multilayer lamination, to accommodate the increased design complexity and performance demands of modern electronic devices.

Performance and Reliability

PCBs generally offer better signal integrity, thermal management, and reliability compared to PWBs. This makes them more suitable for high-performance applications that demand high-speed data transmission, efficient power distribution, or operation under harsh environmental conditions.

Material Selection

The choice of substrate material can impact the performance, durability, and cost of the final product. PWBs typically use lower-cost materials such as phenolic paper or epoxy glass, which may be sufficient for less demanding applications. PCBs often employ higher-performance materials such as FR-4, polyimide, or Rogers materials to meet more stringent performance and reliability requirements.

Cost and Budget Considerations

The overall cost of PWBs and PCBs can be influenced by several factors, including material selection, manufacturing processes, and design complexity. PWBs generally involve lower costs due to simpler materials and manufacturing techniques, making them an attractive option for low-volume production or applications with tight budget constraints. PCBs, with their advanced design capabilities and performance benefits, can justify higher costs for specific applications, especially in high-volume production.

16 layer PCB for advanced electronics

Choosing Between PWB and PCB

Factors to Consider

When selecting between PWB and PCB for a specific project or application, several factors must be considered:

• Design Complexity: The complexity of the circuit design is a critical factor. PWBs are well-suited for simpler designs with lower component density, while PCBs offer greater design flexibility and can accommodate more complex circuits with higher component density.
• Performance Requirements: The performance requirements of the electronic device or system play a significant role. PCBs generally offer better signal integrity, thermal management, and reliability compared to PWBs, making them more suitable for applications that demand high-speed data transmission, efficient power distribution, or operation under harsh environmental conditions.
• Manufacturing Constraints: PWB manufacturing typically involves simpler processes and lower costs, making it an attractive option for low-volume production or applications with tight budget constraints. PCB manufacturing requires more advanced techniques and equipment, which can result in higher costs and longer lead times.
• Material Selection: The choice of substrate material can impact the performance, durability, and cost of the final product. PWBs typically use lower-cost materials, while PCBs often employ higher-performance materials.
• Regulatory and Industry Standards: Certain applications may require adherence to specific standards, influencing the choice between PWB and PCB.

Cost and Budget Considerations

• Material Costs: PWBs typically use cheaper materials, resulting in lower overall costs. PCBs use higher-performance, costlier materials.
• Manufacturing Costs: PWB manufacturing involves simpler and less expensive processes. PCB manufacturing requires advanced techniques, resulting in higher costs.
• Design Complexity: PWBs are suitable for simple, low-cost designs. PCBs can accommodate complex, high-cost designs.
• Production Volume: PWBs are cost-effective for low-volume production. PCBs benefit from economies of scale in high-volume production.

Performance and Reliability

• Signal Integrity: PCBs provide better signal integrity for high-speed data transmission, essential for advanced electronic devices.
• Thermal Management: PCBs offer superior thermal management, crucial for high-power applications.
• Mechanical Stability: PCBs provide better mechanical stability and environmental resistance, making them suitable for harsh conditions.

Key point: By carefully evaluating these factors, professionals can make informed decisions when selecting between PWB and PCB for their electronic design and manufacturing projects.

Conclusion

In the consumer electronics sector, the terms PWB and PCB are sometimes interchangeable. Printed wiring boards (PWBs) and printed circuit boards (PCBs) are both types of electronic circuits used to support and connect electronic components. They are integral parts of any electronic device; however, they serve different purposes when it comes to completing the circuitry.

In summary, the use of the term varies widely per region, but the fundamental distinction between the terms lies within the circuitry. PCBs contain pre-etched circuits, allowing them to be mass-produced quickly and efficiently; in contrast, PWBs have none. Generally, the printed wiring board is a fundamental step in PCB production. The intricate circuit boards we know today were originally PWBs; only they have now evolved to the point where the term PCB is now requisite. This breakthrough brought several benefits for PCB manufacturing in technology and research; however, it did not effectively wipe out the term PWB, which is why both terms are still in use today.

Key point: Understanding the differences between PWBs and PCBs is crucial for making informed decisions in electronic design and manufacturing. PWBs are suitable for simpler, low-cost applications, while PCBs offer greater design flexibility and performance for advanced devices. By considering factors such as design complexity, performance requirements, manufacturing constraints, material selection, and cost, professionals can select the appropriate technology for their specific needs.

FAQs

What is the main difference between PWB and PCB?

The main difference lies in their design complexity and manufacturing techniques. PWBs are simpler, single-sided boards, while PCBs can be single-sided, double-sided, or multilayer, supporting more complex circuits.

Can PWB and PCB be used interchangeably?

While the terms are often used interchangeably, they refer to different board types with varying levels of design complexity and performance. Clarification is essential when discussing specific boards.

When should I choose a PWB over a PCB?

PWBs are suitable for basic electronic functionality, lower component density, and simpler designs. They are cost-effective for low-volume production.

When should I choose a PCB over a PWB?

PCBs are suitable for applications requiring higher component density, complex circuits, and improved performance. They are ideal for high-volume production and advanced devices.

How do the manufacturing processes of PWBs and PCBs differ?

PWB manufacturing involves simpler processes, while PCB manufacturing requires advanced techniques to accommodate increased design complexity and performance demands.