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Home > Mall Dynamic > What Is PCB? Do You Really Know Enough About PCBS? What Does PCB Include?
In the electronics industry, there is a key component called the PCB (printed circuit board). This is such a basic part that many people have a hard time explaining exactly what a PCB is. This article will explain in detail the composition of PCBS and some of the terms commonly used in the field of PCBS. In this article, we will discuss the composition of a PCB, including some terminology, a brief assembly method, and an overview of the PCB design process.
PCB (Printed circuit board) is the most common name, which can also be called "printed wiring boards" or "printed wiring cards". Before PCBS, circuits were made up of point-to-point wiring. The reliability of this method is very low, because as the circuit ages, the rupture of the line will cause the line node to break or short.
Wire winding technology is a major advance in circuit technology, which improves the durability and replaceable ability of the line by winding the small diameter wire around the pole at the connection point.
As the electronics industry evolved from vacuum tubes and relays to silicon semiconductors and integrated circuits, the size and price of electronic components also declined. Electronic products are increasingly appearing in the consumer sector, prompting manufacturers to look for smaller and more cost-effective solutions. Thus, PCB was born.
PCBS look like multi-layer cakes or lasagna - layers of different materials are made and pressed together by heat and adhesives.
Let's start with the middle layer.
FR4
The substrate of PCB is generally glass fiber. In most cases, the glass fiber substrate of the PCB generally refers to the "FR4" material. The "FR4" solid material gives the PCB hardness and thickness. In addition to the FR4 substrate, there are flexible circuit boards produced on flexible high-temperature plastics (polyimide or similar) and so on.
You may find PCBS of different thicknesses; However, most of SparkFun's products are 1.6mm (0.063 ") thick. Some products also use other thickness, such as LilyPad, Arudino Pro Micro boards with 0.8mm board thickness.
Cheap PCBS and perforated boards (pictured above) are made from materials such as epoxy or phenol, which lack the durability of FR4 but are much cheaper. When you weld something on this board, you will smell very bad. This type of substrate is often used in very low-end consumer goods. Phenolic substances have a low thermal decomposition temperature, and too long welding time will lead to their decomposition carbonization, and emit bad taste.
Next is a thin layer of copper foil, which is pressed onto the substrate by heat and adhesives in production. On dual panels, the copper foil is pressed to both sides of the substrate. In some low-cost cases, the copper foil may only be pressed on one side of the substrate. When we talk about "double panels" or "double panels", we mean that our lasagna has two layers of copper foil on it. Of course, in different PCB designs, the number of copper foil layers may be as little as 1 layer, or more than 16 layers.
There are many kinds of thickness of the copper layer, and it is used as a unit of weight, generally using copper to evenly cover the weight of one square foot (ounces oz). Most PCBS have a copper thickness of 1oz, but some high-power PCBS may use 2oz or 3oz copper. To put that in terms of ounces per square foot, it's about 35um or 1.4mil of copper thick.
Above the copper layer is the solder shield. This layer makes the PCB look green (or SparkFun red). The solder stop layer covers the wires above the copper layer to prevent the wires on the PCB from contacting with other metals, solder or other conductive objects, resulting in short circuit. The presence of the solder shield allows you to weld in the right place and prevents solder bridging.
In the example above, we can see that the solder resistance covers most of the PCB (including the wiring), but the silver hole ring and SMD pad are exposed for easy welding.
In general, solder resistance is green, but almost all colors can be used to make solder resistance. SparkFun's boards are mostly red, while IOIO's are white and LilyPad's are purple.
On top of the solder stop layer, there is a white screen printing layer. Letters, numbers and symbols are printed on the screen printing layer of the PCB, which can facilitate assembly and guide everyone to better understand the design of the board. We often use the symbols of the screen printing layer to mark some pins or LED functions.
Screen printing layer is the most common color is white, similarly, screen printing layer can be made almost any color. Black, gray, red and even yellow silk screen layers are not uncommon. However, it is rare to see multiple screen printing layer colors on a single board.
You want to start designing your own PCB. The twists and turns in PCB design are too complicated to say here. However, if you really want to get started, here are a few key points.
Find a CAD tool: In the PCB design market, there are many low-cost or free options. Here are some things to consider when looking for a tool.
Forum Support: Do many people use this tool? The more people use it, the easier it is to find the designed package library for the device you need.
It's easy to use. If it didn't work, you wouldn't use it.
Performance: Many programs have design limitations, such as the number of layers, the number of devices, and the size of the board. Most require you to purchase a license to upgrade the performance.
Suppressability: Some free programs do not allow export or migration to other software, limiting you to a single vendor. The cost and convenience of the software may be worth it, but sometimes it's not.
Look at other people's fabric designs. Open source hardware makes this easier and easier.
Practice, practice, practice.
Keep your expectations low. The first board you design may have a lot of problems, but the 20th board may be a lot less, but there will be some problems. But it's hard to get rid of all the problems.
Schematics are very important. Trying to design a PCB board without good schematic support is futile.
Finally, talk about some of the benefits of designing your own board. If you plan to work on one or more established projects, the benefits of designing a circuit board are obvious. Compared to the design circuit board, the point-to-point wiring on the breadboard is too difficult, and the reliability is relatively low. And, if your design is good, you can buy your design for a good price:)
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