Have you ever wondered how a printed circuit board is made? If so, here is a simple beginner’s guide to the PCB manufacturing process.
Printed circuit boards are everywhere from your smart refrigerator to your laptop to your electric razor. These tiny brains run your world!
If you want some insight into printed circuit board production, read on. What you find out will make you appreciate your everyday devices in a whole new light.
Here is a simple beginner’s guide to the PCB manufacturing process.
A Brief Guide to the PCB Manufacturing Process
The printed circuit board (PCB) is the grand central station for all of your device’s communication. An electrical gadget needs an internal manager, which can control the distribution of electric current.
The PCB is that manager.
Every device has different functionality and electricity needs. There is an infinite number of PCB designs out there.
From capacitors to switches to diodes and resistors, the components that control your devices need a platform to function.
The PCB is that platform.
If you want to understand printed circuit board production, you should start by learning some of a PCB’s basic parts.
The Anatomy of a Printed Circuit Board
The four essential parts of a printed circuit board are the fiberglass substrate, copper, solder mask, and silkscreen.
Let’s look at each of these pieces individually, along with the process that brings it all together.
The substrate forms the central portion of the PCB. Manufacturers use a particular type of fiberglass, known as F4. F4 tends to be lightweight, heat tolerant, and durable enough to withstand the manufacturing process as well as the wear and tear a PCB will receive.
Copper serves as a vital avenue for electrical current within the circuit board. Old-time circuit boards (before printing capabilities) included cumbersome wires that connected each component.
With the advent of PCBs, copper trails, or “traces,” embedded in the fiberglass substrate, have taken the place of wires. By manufacturing the board in such a way that the copper tracings lie flat on the board, engineers were able to save an enormous amount of space.
Thanks in large part to copper traces, PCBs have evolved to be more compact, accommodating the trend towards smaller devices.
Solder mask is a polymer layer that covers the PCB.
Even though you can see the copper traces on the PCB surface, you can only solder it at particular areas, often where the components insert. The job of the solder mask is to protect the rest of the copper traces from unwanted surface interference.
As the PCB’s most superficial layer, the silkscreen layer is remarkably similar to other types of silkscreen. Relevant information about the board — including vital data, as well as a brand logo — gets printed on the silkscreen layer.
Printed Circuit Board Production
The printed circuit board manufacturing process is incredibly complex. Have you ever asked yourself, how are circuit boards made? Luckily, there are a few key processes that will help you understand how it all works.
The design process, while not technically part of the manufacturing, is the first step in PCB production.
Expensive software can help you engineer your PCB. However, no manufacturer will allow a PCB into production without first troubleshooting it.
In the design stage, developers make ultra-precise tweaks to ensure the PCB is ready and worthy for manufacturing. The process takes time and money, so the PCB’s circuit design must be spot on before the fabrication process begins.
Before anything goes to print, manufacturers must prepare the substrate. While the inner layer of any PCB is a fiberglass substrate, it must first bind with an outer layer of copper. The copper layer will eventually act as the traces. But, early on, it consists of an entire layer covering the substrate.
Note that printed circuit boards can come in a few basic styles. A PCB can come with a copper layer on just one side, both sides, or consist of multiple layers, depending on the functional needs. The more layers of copper, the more complex the functionality.
A layer of a chemical known as “photoresist” then covers the area in preparation for printing. The photoresist preserves the areas of copper that will remain as traces within the PCB.
At some point, the circuit pattern is etched onto this copper-substrate board. To accomplish this, manufacturers first print out the circuit on a thin film. The film is similar to the transparencies used for overhead projectors.
Known as the “production file,” the printed film acts as a photo negative. Manufacturers place the production file on the copper-substrate plate.
Then, a process using ultraviolet light burns away the photoresist layer not covered by the production file. All of the unneeded copper is now re-exposed and ready to be dissolved away with chemicals.
The circuit pattern involves various hole sizes. For example holes for screws, or holes to hold the components in place. Manufacturers drill these holes into the ultra-precise spots as outlined by the production file.
Manufacturers can now eliminate all of the copper not needed as traces. This process is done by washing the PCB with ferric chloride to dissolve copper.
Depending on whether the PCB is single-layered or multilayered, the above process may be done on both sides of a single PCB, or multiple PCBs (if multilayered).
Solder Mask Application
The function of the solder mask is just like it sounds: to protect the PCB board from soldering on traces you don’t want to disturb.
Finally, the silkscreen layer gets applied, typically to the component side.
Bringing a PCB from idea to reality is no small task. PCB fabrication production demands professional insight at every level.
Prepare for Your PCB Future
Thanks to the internet of things, devices are becoming smarter every year. As PCB manufacturing gets more efficient and less expensive, PCBs may soon be more user-friendly than ever.
Stay ahead of the curve by knowing as much as you can about the PCB manufacturing process!
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