Aug 13, 2019|Product Innovations and Design, Technological Advancements and Materials

Presensitizing is a method of processing PCBs (printed circuit board) that involves using UV light exposure. Presensitizing your PCB using UV light is an enjoyable and unique way to process your DIY electronics project. However, there are many steps involved! 

Before you get started, ask yourself if you love the idea of a lighter PCB manufacturing process and if you love the idea of experimenting with your own DIY electronics projects. If your answer is yes, then it’s worth it to learn more about presensitized PCB manufacturing.

In this guide, you’ll learn more about the process of presensitized PCB, photosensitive PCB board, and how to process presensitized PCB boards from scratch, even if you’ve never done it before.

An Introduction to Presensitized PCB

If you love electronics, are a professional, or just an expert level electronics tinkerer, then you’ve probably read all about processing PCBs. Manufacturing your unique PCB can be a very labor intensive and tricky craft better left for the professionals! But maybe you want to create a unique PCB using custom board artwork? If that’s the case, then creating presensitized PCBs might be right up your alley.

You might be asking yourself, what’s the point of presensitizing PCB in the first place? The major benefit that presensitizing offers is that it can be more accurate than other PCB processing methods, such as the toner transfer method.

Creating your presensitized PCB is also very fun if you’re an electronics hobbyist, and if you enjoy tinkering with a unique creation.

Another huge benefit of presensitized PCB is that the process is very low cost. The PCB presensitization process eliminates fabrication steps and thereby lowers cost, so you can afford to experiment with your creative passions without worrying about blowing your budget! 

What Are Presensitized PCBs Exactly?

A presensitized PCB is a special type of PCB where the surface of the board contains a unique photo-sensitive material coating. This presensitized PC board makes it easy for you to apply your unique custom design by transferring (or “burning”) the image by using UV lights. 

A presensitized PCB is like a regular copper-clad PCB, the main difference being how the design transfers onto the board. 

Traditional (copper-clad) PCB boards transfer images in the following ways:

       * Toner Transfer Method

       * Inkjet Masking Method

       * Dry Film Photopolymer Method

Candor uses an innovative liquid film method

Presensitized PCB boards transfer images in the following ways:

       * Exposure to UV light

Presensitized PCBs have a special photosensitive coating added during the manufacturing process. The photosensitive coating is very sensitive to light! A “peel-off” layer protects the unique photosensitive coating from inadvertent light exposure. You should only remove the peel-off protective layer just before UV light exposure!

printed circuit board
A Beautiful Example of Presensitized PCB Artwork! Source: YouTube

The PCB Printing and Preparation Process

Please remember that PCB printing requires an abundance of effort, patience, and testing! So, keep in mind that the first time you print your PCB board using photosensitive PCBs, you might make a mistake. For that reason, it might be a genius idea to create multiple experimental boards the first time you attempt any manufacturing tests.

It’s also a very good idea to become familiar with a reliable PCB manufacturer, so you can remain confident that you’re working with reliable components, and that your supply chain never diminishes, fades, or becomes an issue during your production process!

PCB Preparation

The very first thing to do when working with a presensitized PCB is to take a close look at the thick gray film on either side of the board. This film is designed to protect the board itself from inadvertent exposure to UV lighting. 

Remember that when you remove the film, the board is going to be very sensitive to light, so don’t remove the film until you’re ready to expose the board to your UV light immediately!

Before you remove the protective film, be sure to cut your board according to your project’s specifications. The PCB board and protective film are surprisingly robust and tough, so you don’t have to worry about inflicting damage. It might be a very smart move to cut the PCB larger than your presensitized artwork, as this added real estate can be useful during the etching phase of your board.

Now that your board has been cut and is ready, it might be an even better idea to prepare a second (or third) copy of your board, so you can experiment with the exposure process and try to get the best results. Remember that practice makes perfect, and working with presensitized boards can be tricky the first time you do it!

PCB Exposure

PCB exposure typically takes place inside of an exposure box. An exposure box is simply a box with UV lighting. You can create a unique exposure box yourself or search your favorite electronics store to find a pre-assembled box. Amazon and eBay both have exposure boxes available to buy, but if you’re a true electronics enthusiast, then creating your own will probably be more fun. 

One of the most important things to remember is that if the glass on either side of your exposure box is dirty, then these smudges can easily transfer onto your PCB board during the exposure process!

Nothing will be as annoying and frustrating as to have an ugly blotch, spec, stain or blemish appear on your otherwise-perfect board. So, it goes without saying to ensure that the glass and UV light fixtures in your exposure box are perfectly clean. You should wipe the glass of your exposure box with a microfiber cloth and mild detergent to ensure that the surface is immaculate before you begin the exposure process.

Also remember that when you remove the protective gray film from your presensitized board, just about any source of light can have an impact upon your board. Your board is very light sensitive! So, it might be a good idea to work in a relatively controlled area where there are no bright lights (other than the UV light within your exposure box, of course).

When you are sure that your exposure box is clean, and when you have eliminated all extra sources of bright lights, then it’s time to remove the protective film from either side of your presensitized board.

Now that the presensitized board has had the protective film removed, it’s vital to remember not to touch the surface of your board if possible. The board is very sensitive, so be careful not to smudge or expose the board to any sharp, bright lights!

Carefully, place the top and bottom portions of your presensitized PCB artwork layers around your board so that everything is perfectly aligned and centered. Once you’re satisfied with the alignment, then place your presensitized board inside of the exposure box. Don’t turn the lights on yet!

Once your board is inside of the exposure box, it’s a very good idea to lay a thin and flat piece of glass on top of your board. The reason you do this is so the artwork layer can contact the surface of your board, and to also ensure that your board and artwork layers are both flat.

Once you are certain that your artwork layer aligns perfectly around your board, and once you are certain that the artwork is laying flat against your board, you can then turn on your exposure light.

The time that the exposure process takes is going to vary based upon the strength of your light, and the overall design of your exposure box. Usually, you can expect the exposure process to last anywhere from 1 minute up to over 10 minutes! This variance is why experimentation is so important, and it’s also why we recommended creating many different copies of your board!

uv light
An Amazing Custom-Made PCB Exposure Box! Source: YouTube

Presensitized PCB Concluding Thesis

Congratulations! You now have a much better understanding of presensitized PCBs, and you also realize that creating custom PCBs can be a truly unique, fun and cheap way to experiment with your love for all thing’s electronics.

Make no mistake about it; being able to manufacture PCBs can be one of the most important skills for the electronic hobbyist. If you master this one skill, you can save yourself a ton of frustration, time, and cash, while also having an abundance of fun!

To recap, here are the advantages of creating your unique presensitized PCB:

       1. A very handy skill for the electronics DIY tinkerer to have.

       2. Can be a great way to manufacture a unique PCB design.

       3. Can eliminate steps in the manufacturing process, making it quicker and cheaper.

If you need help with your unique PCB manufacturing process, then never hesitate to check our manufacturing turnaround by using this handy link. If you need help during any phase in your product’s development lifecycle, then we’re here for you every step of the way. Your project needs elite materials, plus knowledgeable support that’s eager to help. We’ve got you covered on all angles.

If you ever have any questions about presensitized PCBs, or if you want help brainstorming any manufacturing process, then never hesitate to contact us. We’re always around to help you, and we love to brainstorm this type of stuff.

Thanks again for reading this guide, and please have a beautiful day!

Author Profile

Sunny Patel
Sunny Patel is the Engineering and Sales Manager at Candor Industries. Sunny is trained as a IPC-A-600 trainer, AS9100 Lead auditor, IPC CID and got his Engineering degree at the University of Toronto.