What Are Printed Circuit Boards Made Of? A Complete Beginner’s Guide

Have you ever wondered what’s inside the little green board that makes your phone or computer work? That’s called a PCB, and it’s like a small city for electricity! It has roads (copper lines), land (the base), and signs (markings) to help everything run smoothly.

The quick answer: A PCB is made of several layers, but the most important parts are:

 Base material – the strong board that holds everything and keeps it safe.

 Copper – the metal lines that carry electricity like tiny highways.

 Surface finish – a coating that protects copper and helps parts stick on.

In this guide, we’ll explore all the main materials in a PCB and what they do. Ready? Let’s dive in!

Why Materials Matter in PCB Design

Why should we care about what materials are used in a PCB? It’s simple: the materials decide how well your board works, how much it costs, and how long it lasts. Let’s break it down:

1. Materials affect performance

If you choose good materials, your PCB can carry signals faster and handle more heat. For example, high-frequency boards need special materials like Rogers so the signals don’t get lost. If the wrong material is used, the board might slow down or fail when it gets hot.

2. Materials affect cost

Not all materials cost the same. Standard FR4 is cheap and good for most projects. But special materials, like those used for 5G or satellites, can cost much more. So picking the right material can save a lot of money without hurting quality.

3. Materials affect reliability

Think about a phone that gets warm when charging. If the PCB inside uses weak material, it could break after a few months. Stronger materials can handle heat and stress, so the board works for years.

So, when making a PCB, choosing the right materials is like picking the right bricks for building a house. It makes everything safer, stronger, and more reliable.

Main Components of a Printed Circuit Board

A PCB is like a layered cake, but instead of cream and chocolate, it has materials that help electricity move safely. Let’s explore each layer:

1. Substrate or Base Material

This is the main body of the PCB. Think of it as the plate that holds everything else. It makes the board strong and stops electricity from going where it shouldn’t.

The most common material is FR4. It’s made of glass fibers mixed with a special glue called epoxy. It’s strong, hard, and does not let electricity pass through.

For flexible PCBs, we use Polyimide instead. This material can bend without breaking. Hard boards are like a wooden ruler – they stay stiff. Flexible boards are like a rubber band – you can bend them around shapes.

Why does this matter? If you need a board that fits inside a tiny watch or a folding phone, you need a flexible material. If it’s for a computer or TV, a hard board works best.

2. Copper Layer

On top of the base material, there’s a very thin layer of copper. This is the part that carries electricity, like roads for cars. The copper makes paths called traces, which connect all the parts so they can talk to each other.

Sometimes, the copper is thick, and sometimes it’s thin. If the board needs to handle a lot of electricity, the copper has to be thicker so it doesn’t overheat. If it’s for small signals, thin copper is fine.

3. Solder Mask

When you look at a PCB, you usually see green. That green layer is the solder mask. It’s like a raincoat for the copper – it protects it from dust, water, and other things that could cause problems.

The solder mask also helps when we attach parts to the board. It makes sure the metal (solder) sticks only in the right places, so there are no messy connections. Without a solder mask, the board would easily short-circuit.

4. Silkscreen

The silkscreen is like the labels on a map. It’s the white text and symbols printed on the board. It tells us where each part goes and what it’s called. For example, you might see “R1” for a resistor or “C1” for a capacitor.

Without these labels, it would be like trying to build LEGO without instructions. You wouldn’t know where to put each piece!

5. Surface Finish

The surface finish is the last layer that touches the copper pads. It has two main jobs:

 Stop the copper from rusting.

 Help the parts stick during soldering.

There are different kinds of surface finishes. One common type is HASL (Hot Air Solder Leveling). It’s cheaper and works for many boards. Another is ENIG (Electroless Nickel Immersion Gold), which uses gold. Gold doesn’t rust, so ENIG makes the board last longer and look shiny, but it costs more.

Common Materials Used in Different PCBs

Not all PCBs are the same. They use different materials depending on what the board needs to do. Some boards just need to be strong and cheap, while others need to handle high-speed signals or bend without breaking. Let’s look at the most common materials:

1. FR4 – The Most Common Choice

FR4 is the material you will find in most PCBs. It’s made of glass fiber and epoxy resin. This combination makes it strong and hard, like a thin, stiff plate. FR4 does not let electricity pass through, which keeps the signals safe inside the copper paths.

Where do we use it? Almost everywhere! Computers, TVs, toys, and many other electronics use FR4. It’s also affordable, which is why manufacturers love it.

2. Rogers – For High-Frequency Signals

Some electronics, like 5G antennas or radar systems, need to work with very high-frequency signals. FR4 can’t handle these signals well because it causes too much loss. That’s why we use Rogers material.

Rogers is a special type of laminate that can handle high-speed signals without slowing them down. It’s also more stable when the board gets hot. The downside? It costs more than FR4.

3. Polyimide – For Flexible Circuits

Have you seen a phone that folds or a wearable device that wraps around your arm? Those need PCBs that can bend without breaking. For this, we use Polyimide, a flexible material that stays strong even when bent many times.

Polyimide is heat-resistant too, so it works well in harsh environments. But, like Rogers, it’s more expensive than FR4.

Quick Comparison Table

Factors That Influence Material Choice

Choosing the right PCB material is like choosing clothes for the weather. You need the right one for the job. Here are the main things that matter:

1. Device Purpose (Everyday Gadgets vs. Special Equipment)

For devices like phones, toys, or TVs, FR4 is an excellent choice because it’s strong and affordable.

When it comes to advanced applications such as planes, rockets, or 5G base stations, Rogers material is the preferred option since it maintains signal clarity and speed.

For designs that require flexibility—such as smartwatches or foldable devices—Polyimide is ideal thanks to its softness and ability to bend without breaking.

2. Temperature and Speed

Boards that need to operate in high-temperature environments require heat-resistant materials such as High-Tg FR4 or Polyimide.

For high-speed signal transmission, like in Wi-Fi or radar systems, Rogers is ideal because it minimizes signal loss.

When dealing with standard speed and normal temperature conditions, FR4 remains the most cost-effective and reliable option.

3. Cost and Budget

Some materials cost a lot. FR4 is the cheapest and works for most boards.

Rogers and Polyimide cost more, so use them only if your design really needs them.

Simple idea: Use FR4 for most jobs. Use Rogers for super-fast signals. Use Polyimide when the board must bend. Pick the right material for the job so the board works well and costs less.

Conclusion

Now you know what PCBs are made of. They have a base material, a copper layer, a protective layer, and a surface finish. The material you choose is very important. It changes how well the PCB works and how much it costs.

If you want a high-quality PCB or you are not sure which material is best, talk to us at PCB MASTER. We are experts in PCB manufacturing and we provide custom PCB solutions for customers all over the world.

Click here or contact us today to get your custom PCB quote!

FAQs

1. Why are most PCBs green in color?

Most PCBs look green because of the solder mask. This layer protects the copper lines from short circuits and dust. Green became popular because it is easy on the eyes and shows tiny details clearly during inspection. Today, you can find other colors like red, blue, or black, but green is still the most common.

2. Can PCBs be recycled?

Yes, PCBs can be recycled, but it is not simple. A PCB has many materials, like fiberglass, copper, and sometimes gold. Recycling means separating these materials, which takes special machines. Recycling PCBs is important because it saves metal and reduces waste.

3. Why do some PCBs bend while others stay stiff?

Some PCBs are made to bend because they use flexible materials like polyimide. These are called flexible PCBs and are used in devices like foldable phones or cameras. Stiff PCBs use hard materials like FR4, which keeps them strong for heavy parts and big boards.