What is a Printed Circuit Board(PCB)?

After World War II, printed circuits replaced conventional wiring in much electronic equipment, such as radio and television sets, computers and control equipment, and airborne and guided-missile electronic systems.

PCB is an acronym for printed circuit board. It is a board that has lines and pads that connect various points together. In the picture above, there are traces that electrically connect the various connectors and components to each other. A PCB allows signals and power to be routed between physical devices.

Step 1: Design and Output.

Circuit boards should be rigorously compatible with, a PCB layout created by the designer using PCB design software. Commonly-used PCB design software includes Altium Designer, OrCAD, Pads, KiCad, Eagle etc. NOTE: Before PCB fabrication, designers should inform their contract manufacturer about the PCB design software version used to design the circuit since it helps avoid issues caused by discrepancies.

Step 2: From File to Film.

PCB printing begins after designers output the PCB schematic files and manufacturers conduct a DFM check. Manufacturers use a special printer called a plotter, which makes photo films of the PCBs, to print circuit boards. Manufacturers will use the films to image the PCBs. Although it's a laser printer, it isn't a standard laser jet printer. Plotters use incredibly precise printing technology to provide a highly detailed film of the PCB design.

Step 3: Printing the Inner layers: Where Will the Copper Go?

The creation of films in previous step aims to map out a figure of copper path. Now it's time to print the figure on the film onto a copper foil. This step in PCB manufacturing prepares to make actual PCB. The basic form of PCB comprises a laminate board whose core material is epoxy resin and glass fiber that are also called substrate material. Laminate serves as an ideal body for receiving the copper that structures the PCB. Substrate material provides a sturdy and dust-resistant starting point for the PCB. Copper is pre-bonded on both sides. The process involves whittling away the copper to reveal the design from the films.

Step 4: Removing the Unwanted Copper.

With the photo resist removed and the hardened resist covering the copper we wish to keep, the board proceeds to the next stage: unwanted copper removal. Just as the alkaline solution removed the resist, a more powerful chemical preparation eats away the excess copper. The copper solvent solution bath removes all of the exposed copper. Meanwhile, the desired copper remains fully protected beneath the hardened layer of photo resist.

Step 5: Layer Alignment and Optical Inspection.

Once the layers are placed together, it's impossible to correct any errors occurring on the inner layers. Another machine performs an automatic optical inspection of the panels to confirm a total absence of defects. The original design from Gerber, which the manufacturer received, serves as the model. The machine scans the layers using a laser sensor and proceeds to electronically compare the digital image with the original Gerber file.

Step 6: Layer-up and Bond.

In this stage, the circuit board takes shape. All the separate layers await their union. With the layers ready and confirmed, they simply need to fuse together. Outer layers must join with the substrate. The process happens in two steps: layer-up and bonding. The outer layer material consists of sheets of fiber glass, pre-impregnated with epoxy resin. The shorthand for this is called prepreg. A thin copper foil also covers the top and bottom of the original substrate, which contains the copper trace etchings. Now, it's time to sandwich them together.

Step 7: Drill.

The drills use air-driven spindles that turn at 150,000 rpm. At this speed, you might think that drilling happens in a flash, but there are many holes to bore. An average PCB contains well over one hundred bore intact points. During drilling, each needs its own special moment with the drill, so it takes time. The holes later house the vias and mechanical mounting holes for the PCB. The final affixation of these parts occurs later, after plating.

Step 8: Plating and Copper Deposition.

After drilling, the panel moves onto plating. The process fuses the different layers together using chemical deposition. After a thorough cleaning, the panel undergoes a series of chemical baths. During the baths, a chemical deposition process deposits a thin layer - about one micron thick - of copper over the surface of the panel. The copper goes into the recently drilled holes. Prior to this step, the interior surface of the holes simply exposes the fiber glass material that comprises the interior of the panel. The copper baths completely cover, or plate, the walls of the holes. Incidentally, the entire panel receives a new layer of copper. Most importantly, the new holes are covered. Computers control the entire process of dipping, removal and procession.

Most of these issues were directly addressed when PCBs went into regular production. 1920s – The early PCB material could be almost anything, from Bakelite and Masonite to plain old thin pieces of wood. Holes could be drilled into the material and flat brass wires would be riveted onto it.

The printed circuit board (PCB) is probably one of the most important inventions of the 20th century. The intellectual father of the printed circuit board was Paul Eisler.

Although the development leading up to the invention of the circuit board can be traced all the way back to the 1890s, the invention of the printed circuit board is credited to Paul Eisler, an Austrian inventor. Paul Eisler first developed the printed circuit board when he was working on a radio set in 1936, but circuit boards did not see mass usage until after the 1950s. From then onwards, the popularity of PCBs began rapidly growing.

You may have noticed that the majority of printed circuit boards have a green colour and you’re probably wondering why. The green colour that you see on the circuit board is actually just the colour of the solder mask that is showing through the glass epoxy. The purpose of the solder mask is to protect the electronic traces underneath from moisture and dust. In reality, the solder mask can come in a variety of colours, such as orange, blue, and yellow, not just green.

There are a few reasons why the majority of circuit boards are green:

The green colour is believed to have been used as the regulation standard for PCBs when they were being used by the American military and it has spread to the rest of the world. The original colour of the glass epoxy is naturally green and the colour may still be used to stay conventional.

Ultimately, the green colour is largely used in the manufacturing of PCBs because engineers find it easier to look for faults in the trace lines.

Did you know that printed circuit boards can be completely customised to your order? You can request a PCB company to design and manufacture circuit boards that completely ticks all of your requirements. For example, if you need to add more functionality to a device, then ordering a custom PCB may be better than a standard PCB. If you require PCB manufacturing, then take a look at our PCB fabrication services here.