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What is a PCB?

By John Sunshine
Updated May 17, 2024
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A PCB is a printed circuit board, also known as a printed wiring board. It is used in electronics to build electronic devices. A PCB serves two purposes in the construction of an electronic device; it is a place to mount the components and it provides the means of electrical connection between the components.

A PCB starts out as a thin, non-conducting sheet of material. The most common material used is a glass fiber epoxy laminate material. A thin layer of copper is then chemically deposited on each side of this material.

The next step is to "print" the connection diagram onto the PCB. The connection diagram is the wiring required to connect the components. In the very early days of electronics, these connections were in fact done with wires. This is the reason PCBs are also sometimes referred to as printed wiring boards. The "printing" is usually done by photographically transferring the image to the board. This image is "printed" with an acid resistant material.

Next, the PCB is put into an acid bath. The acid bath removes the copper from the board, excepting the areas protected by the resistant material. This process leaves the connections or wiring "printed" on the PCB. Next, holes are drilled in the board to allow the components to be mounted to the board and the PCB itself to be mounted to the case protecting the electronics. Finally, a protective coating is applied to the board to prevent corrosion of the copper traces.

The above process describes what is referred to as a doubled sided or two layer PCB. It is possible to make them of almost any number of layers by repeating the process above and laminating the resulting boards into a single PCB. The circuit board inside of the computer on which you are reading this document has a minimum four layers and is more likely to be an eight or even 12 layer PCB.

It is also more common now for parts to be soldered directly to the board, eliminating the need for holes into which leads (wires) from the components must be inserted. A component soldered to the board is logically called a surface mount component, and the board is a surface mount PCB. This technique allows a large increase in the number of components to be mounted on the same PCB, or the same number of components to be mounted on a much smaller one. However, surface mounting also requires better quality control on the manufacture of the PCB.

A PCB is now used in almost every electronic product available. It is by far the most common method currently used to connect and assemble the components of almost any electronic device.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon229001 — On Nov 11, 2011

Its very good information for us, but tell me one thing that is used in coating for protection to prevent the corrosion.

By consultsoft — On Mar 08, 2011

It's a great starter article with some invaluable information right there. Who knew PCBs came in layers?

By anon155849 — On Feb 24, 2011

I very much enjoyed this article. Please keep putting out informative and high quality articles such as this one. Thank you.

By mike990 — On Oct 05, 2010

Interesting post and very informative. Now I have a very good idea about the basics of PCB.

By anon106138 — On Aug 24, 2010

Excellent work. Highly appreciated. Thanks.

By anon105647 — On Aug 21, 2010

Very well written and very descriptive!

By anon83675 — On May 12, 2010

thanks for such a valuable information. thank you.

By anon77494 — On Apr 14, 2010

thanks for info mate.

By anon52078 — On Nov 11, 2009

Thank you very much! Really helpful! I'm a PCB designer.

By anon51204 — On Nov 04, 2009

Good explanation. Thank you.

By anon51045 — On Nov 03, 2009

Simple and clear explanation. I was searching for introductory material on PCBs and found what I was looking for on your site. Thanks.

By anon30636 — On Apr 22, 2009

Really really helpful. Had to describe the process for a project (missed out when they were fabricating our boards at school) and this put it so simply.... Keep up the good work. Thanks

By anon21157 — On Nov 11, 2008

Thanks, that was a very clear and concise description.

By anon9115 — On Feb 28, 2008

Wonderful! I was looking for this knowledge-based article on PCB. I was bit confused between conducting and traces, but reading this article, I am quite sure what PCB is all about.

Thanks

By anon4298 — On Oct 12, 2007

Very good information about PCB, that helps people who are unknown about the wired circuit board.

Kalpesh Patel

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