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PCB Fabrication Basics – Anatomy Of A Printed Circuit Board

From the used to be pagers or beepers, to radios and radars, to the modern cell phones and laptops, all of such computer systems are composed of one common basic component: PCBs. Printed circuit boards or printed wiring boards or cards – however you may call it, it is one of the fundamentals of electronics and let’s take time to understand how it is made and used.
 

What really is a PCB?

A printed circuit board, or PCB, is a self-contained module of interconnected electronic components. Simply speaking, it is a board consisting of lines and pads that connect various points together. It can perform a single specific function or even up to multiple ones.
 

What is it made of?

Like what was said earlier, a printer circuit board is composed of lines and pads, but going into more detail, let’s break down the components that make up this board’s composition (as determined through PCB fabrication). Imagine it like a layered cake, or a lasagna, wherein different layers are laid up and are laminated together through heat and adhesive materials.
 
PCB AssemblyFirst off, is the base material, substrate, usually fiberglass. This is the main component of a printed circuit board. This gives the board a thick and rigid solid core. In some cases though, a printed circuit board can be built on flexible high-temperature plastic, Kapton, for example, or any equivalent.
 
Printed circuit boards come in different thicknesses; though, commonly, they come in 1.6mm or 0.063”. There are also cheaper printed circuit boards and they come in made from other less expensive materials such as epoxies or phenolics. You need to take note though, that should you be opting for this alternative that they come in less durable.
 
You will notice this when you solder to it during PCB fabrication, they will emit a relatively distinct bad odor. They should be handled or used with extra care as they can have a low thermal decomposition temperature, causing them to delaminate, smoke up, and even char. Low-end consumer electronics are usually built on these types of printed circuit boards.
 
Printed circuit boardsThe next layer, would be a thin copper foil, laminated to the board with head and adhesive materials. On double sided printed circuit boards, the more common ones, this is applied to both sides of the substrate. However, in lower end electronic gadgets, copper could only come in one side of the board. When talking about double sided printed circuit boards, it just means that it is referring to the number of copper layers the board has, which is 2 in this matter. It can come in as few as one layer, or can grow as many as twenty or even more.
 
The thickness of this copper layer can also vary between PCB fabrication processes, but it is, and should be, specified by weight, in ounces per square foot. Majority, well vast majority, of printed circuit boards have one ounce per square foot but should they need to handle very high power, they can have up to 2 or 3 ounces per square foot. Each ounce per square foot translates to about 35 micrometers or 1.4 thousandths of an inch of thickness of copper.
 
The solder mask would be the next layer laid on top of the copper foil. This is what makes the printed circuit board green in color, though some rare varieties can come in red too so any color is possible. It is laid on top of the copper foil layer to insulate it and prevent contact to other metal components. This can help the user to solder to the proper places and prevent what they call, accidental jumpers.
 
Pcb fabricationA white silkscreen layer is what’s overlaid onto the solder mask layer. This adds letters, or numbers, or any symbols to the printed circuit board and makes easier assembly for users. This way, humans can see indicators and better understand the board. The silkscreen labels are used in indicating what the function of each pin or LED is. Normally, the silkscreen labels are white in color but any color can be just used, such as gray, red, black, or yellow. But never a case that multiple ones are used as it will be difficult to embed.
 
As you can see a printed circuit board is made up of dedicated materials and can be quite a challenge to build. However, to make our lives easier, and not to mention, safer, there are some services out there that can provide you ready made circuit boards. Or should you have a more detailed and specific design or build in mind, they can do the PCB fabrication process for you. Some services, such as from Imagineering, Inc., come in online. Ordering and obtaining your printed circuit boards are less hassle and come in a very timely manner, and not to mention, with highest of quality.

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Author | Elsie Hamilton Comments | 0 Date | July 13, 2016