The components that are to be placed on a PCB are connectected by either ‘through hole’ methods, or they are surface mounted. With the former, small wires are pushed through small holes in the board and soldered to connectors on the circuits. Surface mounted components are connected directly using J or L shaped legs and solder paste is used to keep them in place until the solder is melted in an oven to make the connection more permanent.
PCB LayoutWhile it seems pretty standard and uniform, there is no such as thing as a standard PCB layout or design. Every board is custom made for a specific product, and it has to perform a specific function in the space given to it.
In the design process, special software is used so that designers can ‘map out’ the space available for the board and where the components can fit in the best way possible. This includes holes for leads, wires and connection points and where they need to go.
This is then sent to the drilling machine, or the the auto solder paster which is used in the manufacturing process. With the pattern laid out a negative mask is printed on clear plastic.
What’s it made of?The most common material used in constructing the base is a reinforced glass fibre resin, which has a copper foil bonded on either one or both sides. However, there is a much cheaper type which is made from a reinforced paper base. These are typically found in things like television remote controls.
Circuits themselves are made from copper, which has either been plated or etched onto the surface of the board in order to create the required pattern. To prevent oxidisation, the circuits are then coated with a thin layer of tin-lead. Contacts are also coated in this way, with the addition of nickel and gold to increase conductivity.
It’s in the making of itThe assembly and processing of circuits board are done in extremely clean conditions, where everything including the air can be cleared of particulates. Manufacturers typically own their own proprietary processes to make certain of a clean environment.
The actual process of making printed circuit board is a lot more complicated, involved and fantastically awesome than you would probably first imagine it to be. There is so much involved that you wouldn’t think of, such as the application of layer upon layer of copper, tin (as alluded to above) polymer, resins, solder and even gold. All of which is interspersed with bath type dunks to remove surplus coatings from the areas that it isn’t welcome (we’ve all been there, I think).
Have you ever wondered exactly why they are called ‘printed’ circuit boards? Well, It’s because many of the production stages involve the use of printing the kinds of masks previously mentioned.
Any text or legends are silk-screened onto the printed board. This is done by using the biggest inkjet printer that you ever saw.
Best PracticeWhen designing circuit boards, manufacturers tend to stick to a few basic rules to make the entire production process as simple for everyone as is possible. These rules are not rules at all, really, more best practice guidelines. A selection are shown here for reference:
Grid spacing is very important and designers need to find one that is going to fit the majority, if not all, of the components. A lot of devices are available in different sizes, so designers take advantage advantage of that.
For maximum efficiency, like for like should be grouped together. If discrete components are needed for a particular device then place them close by to it. This way the bypass capacitors and resistors are there too.This will keep track lengths short and helps with fault finding.
The printed silkscreens are supposed to convey information and pertinent details to the board builder, service engineers, test engineers, installers and the end user. Too much detail or superfluous text is confusing and cause a lot of problems further down the line. That said, things should not be left out either. Component orientation is not always obvious or clear cut.
These kinds of details are important and should not be overlooked, even if wording ends up underneath components after everything has been assembled. Proper screening, on both sides of the board, can actually reduce build times.
Printed circuit board designs are becoming widely shared, and increasingly so. Reference designs are also being relied upon more by in-house design teams as well as hobbyists.
It is important then that that basic, best practice rules remain in printed circuit design, and are continued by everyone in the PCB manufacturing industry. Keeping these basics firmly in mind means that PCB developers are able to retain flexibility. This means they can continue to add value to their products and get the most out of every single board that they make.
Looking to the future of the printed circuit boardPCBs of the future, if a certain university in Texas has it’s way, will be 3D printed. In fact, they won’t be PCBs anymore. The printed circuit structure is still in development but it is most definitely coming.
However long it takes for that to happen, the ‘traditional’ printed circuit board isn’t going anywhere. They can be found in every aspect of our lives and to move away from them would be living in a tent , in the middle of a field.
The simple fact is, if it uses electricity in any way then it almost certainly has a printed circuit board buried away inside it somewhere.
Know that you know the kind of thought and effort that goes into making a PCB, spare the designer a thought before throwing the TV remote while watching the big game.