How Are Printed Circuit Boards Made?

You need printed circuit boards, or PCBs, for your product to function. But how are these essential components made, and what are they made of? PCB technology is fairly complicated, and you might be curious about how your printed circuit boards are manufactured before they become part of your product.

This blog can walk you through the basics of PCB manufacturing. If you want to know the specifics about your PCB, you’ll need to ask your manufacturer to walk you through the details. However, though the process can be complex, it can usually be boiled down to these fundamental steps.

1. The Substrate
Most printed circuit boards are built in layers. The middle layer is the base material, also called the substrate. The substrate material takes up most of the PCB’s thickness-if you were to turn the board sideways, most of the width would be the substrate.

Depending on the material of the substrate, PCBs can be either rigid or flexible. Historically, most PCBs have been rigid with a fiberglass substrate, but that isn’t always the case anymore. Many new PCBs are made from a flexible substrate material like a special plastic that can withstand high temperatures.

To make the substrate, the material is usually laid out, sprayed with or dipped in epoxy resin, and rolled until it is the right thickness, like a baker would roll pie crust with a rolling pin. When the material is at the correct thickness, the rollers stop and the substrate material goes through an oven to cure it, making it firm and solid. At this point, the first layer of the printed circuit board is finished.

2. The Copper
Printed circuit boards can be very simple or very complex, depending on what they need to do. The base of the board is the substrate, but copper forms the essential layers. A PCB can have one layer of copper on top, two layers on either side of the substrate, or multiple layers alternating between substrate and copper-some PCBs have 16 or more layers of copper.

The copper layers are much thinner than the layers of substrate. The copper’s purpose is to carry charge; without this layer, electricity would not be able to flow through the printed circuit board.
The PCB manufacturer attaches the copper to the substrate with adhesive, pressure, and heat. The combination of these factors makes the copper bind very tightly to the base material. After it’s bonded, the PCB is ready for drilling.

To work properly, the PCB must be able to carry charge in the right places from one layer of the board to the other. Charge flows through holes called vias. Depending on your manufacturer, these vias may be drilled by a CNC machine, a UV laser, a CO2 laser, or another device. The more precise the drilling instrument, the more complicated and precise the PCB can be.

After the vias are drilled, the holes are cleaned, or deburred, to make sure that there isn’t any extra debris or material clogging them. Then the vias’ inside walls are coated in copper-that way, the via will carry the charge from one layer of the PCB to the other.

The next step is to print the circuit pattern itself. This can be done by either adding copper in the correct pattern or by adding more copper to the entire board, then scraping off everything that’s not part of the circuit pattern.

After the circuit pattern is printed, any components that need to be added, like LEDs, transistors, or capacitors, are soldered on.

3. The Solder Mask
All the exposed metal on the PCB can get damaged. Copper corrodes, which will wreck the PCB. In order to protect the copper plating and components, manufacturers add at least one extra layer on top.

Often, at least some portions of the PCB get plated over with either tin-lead, nickel, or gold, or all three, to protect it thoroughly. Over the top of everything, the manufacturer can put on a layer called the solder mask. This material is usually green, and it gives PCBs their recognized appearance.

This layer covers all the metal that doesn’t need to connect with anything, making sure that it stays intact and that electricity only flows through the proper paths. Over the top of everything, the manufacturer might put a final layer of silkscreen, simply to write labels on important areas.

Making a printed circuit board is complex and very technical. When you look for a manufacturer, look for an expert-you need someone who can make these devices with precision and expertise. You also need to find someone whose methods are proven and who has high-quality equipment.

Call Streamline Circuits. We’re a leading manufacturer of printed circuit boards, and you can rest assured that we know what we’re doing. Contact us, and we’ll make PCBs that will make your product shine.