Circuit boards are the backbone of modern electronic devices, serving as the foundation upon which complex electronic circuits are built. When we talk about circuit boards, we are usually referring to Printed Circuit Boards, commonly known as PCBs. These vital components play a crucial role in the functionality of virtually all electronic gadgets and systems we use today. In this article, we will explore what PCBs are, how they work, and why they are indispensable in the world of electronics.

1. What is a Printed Circuit Board (PCB)?

A Printed Circuit Board (PCB) is a flat, usually rigid board that supports and connects electronic components using conductive pathways etched or printed onto the surface. These pathways, or traces, are typically made from copper and are laid out in a precise pattern that determines how the components interact with each other.

Key Features of a PCB:

Conductive Traces: Copper pathways that carry electrical signals between components.

Layers: PCBs can be single-layered or multi-layered, depending on the complexity of the circuit.

Substrate: The base material of a PCB, usually made from fiberglass or other insulating material, provides structural support.

Components: Electronic components like resistors, capacitors, and integrated circuits are mounted on the PCB.

2. How Does a PCB Work?

PCBs serve two primary roles: mechanical support and electrical routing. Components are mounted onto the board, either through Surface Mount Technology (SMT) or Through-Hole Technology (THT). Signals travel along copper traces, enabling components to interact and the device to function as intended.

But here’s the kicker… The real magic lies in the layout. Well-designed PCBs reduce noise, ensure signal integrity, and optimize power distribution.

3. The Working Process: How a PCB Is Made

This is where it gets interesting, The manufacturing process of a PCB is an intricate, step-by-step journey combining chemistry, precision machining, and rigorous testing. Here’s a full walkthrough of over 30 key steps, reflecting industry-leading processes adopted by SQPCB: The process of EASYPCB or complex PCB is almost the same

3.1 PCB Boards Manufacturing: Cutting the Raw Material

The manufacturing process begins with cutting the raw PCB material. The material, typically fiberglass-reinforced copper foil, is cut to the required size. The accuracy of cutting is critical, with a tolerance of +/-2mm. Common material sheet sizes include 36”*48”, 40”*48”, and 42”*48”. Material utilization is important for reducing waste, and in special cases, materials can be mixed for cutting to optimize production efficiency.

3.2 PCB Boards Manufacturing: Inner Layer Processing

This stage involves several sub-processes:

Pre-treatment: Cleaning and preparing the laminate to ensure a contaminant-free surface.

Coating: Applying a photosensitive coating on the laminate surface.

Exposure: Using a photomask to expose the coating to UV light, transferring the design pattern onto the laminate.

Development and Etching: Developing the exposed pattern and removing unwanted copper using a chemical etching solution.

Drilling: Drilling holes for vias and component leads.

AOI (Automated Optical Inspection): Conducting visual inspection to ensure quality.

At SQPCB, advanced techniques such as LDI (Laser Direct Imaging) exposure machines and fully automated coating and baking lines are used. The use of LDI technology minimizes film shrinkage issues, ensuring precise alignment and reducing registration errors. This innovation helps maintain controlled shrinkage within 0.1um, improving the overall quality of the inner layers.

3.3 Lamination and Pressing

The lamination process involves the bonding of multiple layers to create multi-layer PCBs. This step includes:

Brown-Out and Riveting: Pre-pressing the laminate to form a stable base.

Pre-Stacking: Aligning the stacked layers of copper, laminate, and prepregs.

Pressing: Applying heat and pressure to bond the layers together.

X-ray Drilling Targets: Drilling targets are aligned and inspected using X-ray systems.

Edge Trimming and Grinding: Trimming the edges and ensuring uniformity in thickness.

Pressing is one of the most critical steps in multi-layer PCB production. SQPCB has optimized this process by selecting structures that not only meet the required board thickness but also improve impedance control. Materials such as 7628 are selected over more expensive options like 2116, significantly reducing costs while ensuring high performance.

3.4 Drilling Process

Drilling is a crucial step for creating holes for vias and through-hole components. It involves:

Pre-Drilling: Initial drilling to prepare the material for deeper cuts.

Drill Bit Grinding: Ensuring the drill bits are sharpened to maintain precision.

Pinning and Drilling: Ensuring accurate hole placement and depth.

Drill Bit Retirement and Peak Polishing: Polishing drill bits after 3,000-5,000 holes to maintain their effectiveness.

SQPCB uses linear motor-driven drilling machines, ensuring high-speed and high-precision drilling. These machines guarantee hole accuracy and consistency, ensuring that all holes meet IPC standards with a tolerance of +/-2mil.

3.5 Electroplating Process

Electroplating is essential for copper deposition inside drilled holes and on the PCB surface. The process includes:

High-pressure Water Washing: Ensuring the board is clean before electroplating.

PTH (Plated Through-Hole): Plating copper inside the holes for electrical conductivity.

Copper Electroplating: Depositing a thin layer of copper onto the surface and inside the holes to ensure good electrical connections.

SQPCB uses renowned electroplating equipment, investing in high-quality systems that improve yield and reduce the failure rate. While equipment costs may be higher, the long-term benefits of reduced downtime and superior quality outweigh the initial investment.

3.6 Outer Layer Processing

After the inner layers are completed, the outer layer processing begins. It includes:

Pre-treatment: Cleaning the copper surface before applying the protective coatings.

Film Lamination: Applying a protective film for further processing.

Exposure and Development: Using LDI technology to transfer the design onto the outer layer.

Etching and Removal: Removing the unwanted copper, leaving behind the designed circuit pattern.

AOI and Impedance Testing: Ensuring the design meets the required impedance and quality standards.

At SQPCB, LDI exposure machines with linear motor and optical scale control help achieve shrinkage accuracy within 0.1um, ensuring excellent alignment and reducing defects caused by manual handling.

3.7 Solder Mask Application

A solder mask is applied to the PCB to protect copper traces and prevent solder bridges during the assembly process. The steps include:

Pre-treatment and Silk Printing: Printing the solder mask onto the PCB.

Pre-baking: Pre-curing the solder mask to harden it before exposure.

Exposure and Development: Using UV light to expose and harden the mask where needed.

SQPCB implements automated solder mask applications, significantly reducing manual errors such as solder mask shift or incorrect pad coverage. This system helps maintain uniformity and ensures a high-quality finish for all PCBs.

3.8 Text and Legend Printing

Text and legends are applied to the PCB to mark components, references, and other essential information. The process includes:

Silk Screen and Inkjet Printing: Printing labels and other markings.

Post-Baking: Curing the printed ink to ensure durability.

SQPCB uses linear motor-driven inkjet printing machines, achieving exceptional control over shrinkage and print accuracy. This technology reduces defects caused by misalignment and guarantees clear, legible text.

3.9 Surface Finishing

A surface finish is applied to exposed copper areas to protect against oxidation and improve solderability. This step includes:

Gold Immersion (ENIG), HASL, or OSP: The choice of surface finish is based on customer requirements for durability and solderability.

3.10 Final Inspection and Electrical Testing

Before assembly, PCBs undergo a series of tests to ensure their functionality:

Electrical Testing: Detects open circuits, short circuits, or misalignments.

Flying Probe Testing and AOI: Ensure the PCB meets design specifications.

Final inspection is essential to ensure that no defects are present and the PCBs meet industry standards before packaging.

SQPCB, with over 14 years of expertise, follows a similarly rigorous process with a custom-built quality system to ensure each board meets high-reliability standards. also provide express PCB service

4. Types of PCBs

PCBs come in various types, each suited to specific applications:

Single-Layer PCBs: These have one layer of copper and are used in simple electronic devices.

Double-Layer PCBs: These feature two layers of copper, allowing for more complex circuits.

Multi Layer PCBs: With multiple layers of copper and insulating material, these are used in advanced electronics like smartphones and computers.

Flexible PCBs: Made from flexible materials, these PCBs can bend and fold, making them ideal for wearable devices.

Rigid Flex PCBs: A combination of rigid and flexible PCBs, used in applications where space and weight are critical.

5. Applications of PCBs

PCBs are ubiquitous in the electronics industry and are found in almost every electronic device. Some common applications include:

Consumer Electronics: Smartphones, laptops, and home appliances rely on PCB to function.

Automotive Industry: Modern vehicles use PCB in their control systems, infotainment systems, and safety features.

Medical Devices: PCB are crucial in medical equipment such as MRI machines, pacemakers, and diagnostic tools.

Telecommunications: Networking equipment, routers, and communication devices depend on PCB for signal processing and connectivity.

6. Importance of PCBs in Modern Technology

The invention and widespread use of PCBs have revolutionized the electronics industry. They allow for compact, reliable, and cost-effective circuit designs, enabling the development of increasingly sophisticated electronic devices. Without PCBs, the miniaturization of technology and the proliferation of portable electronics would not be possible.

7. PCB Circut Boards Cost Analysis

Cost Breakdown for 2-Layer PCB (1.6mm Thickness, Based on Base Material Cost = 1):

Base material cost: 1 (reference point)

Utilities and labor: Approximately 0.5 to 0.7

Surface finishes:

HASL (Hot Air Solder Leveling): ~0.2

OSP (Organic Solderability Preservative): ~0.1

ENIG (1μin gold): ~1

ENIG (2μin gold): ~1.4

Copper thickness increase:

For each additional 1oz copper on both sides: ~1

Cost Breakdown for 4-Layer PCB (Based on Base Material Cost = 1):

Base material cost: 1 (reference point)

Utilities and labor: Approximately 0.8 to 1.0 (due to additional steps like inner layer etching, lamination, and registration)

Surface finishes:

HASL: ~0.2

OSP: ~0.1

ENIG (1μin gold): ~1

ENIG (2μin gold): ~1.4

Copper thickness increase:

For each additional 1oz copper per layer (all four layers): total cost increase of ~2

Summary Recommendations:

For standard 2-layer PCBs, OSP is a cost-effective surface finish.

For multilayer PCBs, especially with gold fingers or requiring better solder pad reliability, ENIG is preferred.

When increasing copper weight, especially on multilayer PCBs, be aware of the significant cost increase across all layers.

8. Conclusion

Printed Circuit Boards (PCB) are the cornerstone of modern electronics, providing the necessary infrastructure for the functioning of countless devices. From simple gadgets to complex machinery, PCB are essential in making our digital world possible. Understanding the basics of PCB gives us a greater appreciation of the intricate design and engineering that goes into the devices we use every day.

For anyone interested in electronics or considering a career in this field, a solid understanding of PCB is fundamental. As technology continues to advance, the role of PCB supplier will only grow, further cementing their place as an indispensable component in the world of electronics.

9. FAQs About PCB Boards

Q1: What is the difference between SMT and PTH?
A: SMT (Surface Mount Technology) places components directly onto the surface of the PCB using solder paste and reflow soldering. It’s ideal for high-density, compact designs and is widely used in modern electronics due to its speed and automation compatibility.
PTH (Plated Through Hole), on the other hand, involves inserting component leads through drilled holes in the PCB and soldering them, usually from the bottom side. It’s mechanically stronger and better suited for connectors, large components, or products requiring higher reliability in harsh environments (e.g., automotive, military). In many designs, a hybrid of SMT and PTH is used to balance performance, size, and durability.

Q2: What’s the purpose of V-cut in PCB panels?
A: V-cut, or V-groove, is a shallow scoring process made on both the top and bottom surfaces of a PCB panel, allowing boards to be easily snapped apart after assembly. It’s commonly used in high-volume SMT production to panelize multiple identical boards together, enabling automated pick-and-place and reflow processes. V-cut is especially helpful for rectangular designs, offering a clean break without damaging the circuits or needing additional routing.

Q3: How many layers can a PCB have?
A: PCBs can range from a simple single-layer design to over 40 layers in advanced applications like servers, high-speed computing, or aerospace systems. Most consumer electronics, such as smartphones, routers, or tablets, typically use 4–8 layers.
Multilayer boards offer better electrical performance through dedicated power and ground planes, reduced EMI, and more routing space for dense circuits. However, more layers also mean higher cost and complexity in manufacturing and testing.

Q4: How does AOI (Automated Optical Inspection) work?
A: AOI is a non-contact inspection method that uses high-resolution cameras, structured lighting, and image processing software to scan assembled PCBs. It compares the actual board to a digital reference and detects issues like missing components, wrong polarity, solder bridging, tombstoning, and misalignment.
AOI is essential in modern SMT lines because it catches defects early—before boards move to the next stage like reflow, testing, or final assembly—thus saving cost and improving overall product quality and yield.

Q5: Can I prototype a PCB without going to mass production?
A: Yes, prototyping is not only possible but essential. A PCB prototype is a small-batch run used to validate the design before committing to mass production. It allows you to test circuit performance, component fit, thermal behavior, and signal integrity.
Many manufacturers—including SQPCB, known for their flexible engineering support—offer fast-turn prototyping services, including various copper thicknesses, material types, and surface finishes. Whether you’re a startup developing IoT devices or an established OEM testing a new product line, prototyping gives you the confidence to move forward with minimal risk.