Printed circuit board (PCB) is one of the most common names, and can also be called "printed wiring boards" or "printed wiring cards". Before the PCB appeared, the circuit was made up of point-to-point wiring. The reliability of this method is very low, because as the circuit ages, the breakage of the line can cause an open or short circuit of the line node.
Winding technology is a major advancement in circuit technology that enhances the durability and replaceability of the line by winding small diameter wires around the posts at the joints.
As the electronics industry moves from vacuum tubes and relays to silicon semiconductors and integrated circuits, the size and price of electronic components are also declining. Electronic products are appearing more and more frequently in the consumer sector, prompting manufacturers to look for smaller and more cost-effective solutions. So, the PCB was born.
The PCB looks like a multi-layered cake or lasagna - a layer of different materials in the process that is pressed together by heat and adhesive.
Start with the middle layer.
FR4The substrate of the PCB is generally glass fiber. In most cases, the fiberglass substrate of a PCB is generally referred to as the "FR4" material. The solid material "FR4" gives the hardness and thickness of the PCB. In addition to the FR4 substrate, there are flexible circuit boards produced on flexible high-temperature plastics (polyimide or the like) and the like.
You may find PCBs of different thicknesses; however, the thickness of SparkFun's products is mostly 1.6mm (0.063''). Some products also use other thicknesses, such as LilyPad and Arudino Pro Micro boards with a thickness of 0.8mm.
Cheap PCBs and hole plates (see above) are made of materials such as epoxy or phenol, which lack the durability of FR4 but are much cheaper. When soldering things on such boards, you will smell a lot of odor. This type of substrate is often used in very low-end consumer products. Phenolic substances have a low thermal decomposition temperature, and the long welding time causes decomposition and carbonization, and gives off an unpleasant taste.
Copper
The following is a very thin copper foil layer that is pressed into the substrate by heat and adhesive during production. On the double-sided board, the copper foil is pressed to the front and back sides of the substrate. In some low-cost applications, copper foil may only be pressed on one side of the substrate. When we refer to "double-panel" or "two-layer board", it means that there are two layers of copper foil on our lasagna. Of course, in different PCB designs, the number of copper foil layers may be as small as one layer or more than 16 layers.
The thickness of the copper layer is relatively large and is measured in weight. It is generally expressed by the uniform weight of copper covering one square foot (oz). Most PCBs have a copper thickness of 1oz, but some high-power PCBs may use 2oz or 3oz copper. Convert ounces (oz) per square foot, roughly 35um or 1.4mil copper.
SoldermaskAbove the copper layer is a solder mask. This layer makes the PCB look green (or SparkFun's red). The solder mask covers the traces on the copper layer to prevent traces on the PCB from coming into contact with other metals, solder or other conductive objects. The presence of the solder mask allows you to solder in the right place and prevent solder bridges.
In the example above, we can see that the solder mask covers most of the PCB (including traces), but the silver hole ring and SMD pad are exposed to facilitate soldering.
In general, solder masks are green, but almost all colors can be used for solder masking. Most of SparkFun's boards are red, but the IOIO boards are white and the LilyPad boards are purple.
Silkscreen (silk screen)
Above the solder mask, there is a white silk screen layer. Letters, numbers, and symbols are printed on the silkscreen of the PCB to facilitate assembly and guide you to better understand the design of the board. We often use the silkscreen symbol to indicate the function of certain pins or LEDs.
The most common color of the silk screen layer is white. Similarly, the silk screen layer can be made into almost any color. Black, gray, red and even yellow silk screens are not uncommon. However, it is rare to see a variety of silkscreen color on a single board.
The next page will introduce some common terms used in PCB.
TerminologyNow that you know the structure of the PCB, let's take a look at the PCB-related terminology.
Hole ring -- the copper ring on the metallized hole on the PCB.
A program that checks if the design contains errors, such as shorted traces, too thin traces, or too small holes.
Drill Hole Hit -- Used to indicate the deviation of the drill position required in the design from the actual drill position. Incorrect drilling centers caused by blunt drill bits are a common problem in PCB manufacturing.
(Gold) Fingers - A bare metal pad on the edge of the board that is typically used to connect two boards. Such as the edge of the computer's expansion module, the memory stick and the old game card.
Stamp Holes - In addition to V-Cut, there is another alternative board design method.By forming a weak joint between some continuous holes, it is easy to separate the board from the imposition. SparkFun's Protosnap board is a good example.
Automated circuit board production equipment often has problems when producing small boards, and combining several small boards can speed up production.
Plane -- a continuous piece of copper on the board. It is generally defined by boundaries, not paths. Also known as "Copper Copper"
The metallized via may be the connection point of a plug-in, the layer of the signal, or a mounting hole.
During the reflow process, the solder paste melts and establishes a reliable electrical and mechanical connection between the pad and the device pins.
Designing your own! Design your own!
Do you want to start designing your own PCB? The curved bends in the PCB design are too complicated to say here. However, if you really want to get started, here are a few points.
Find a CAD tool: There are many low-cost or free options in the PCB design market. When looking for a tool, consider the following points.
Forum support: Is there a lot of people using this tool? The more people use it, the easier it is for you to find the package library you have designed for the device you need.
Very easy to use. If it is not easy to use, you will not use it.
Performance: Many programs have limitations on the design, such as the number of layers, the number of devices, and the size of the board. Most require you to purchase an authorization to upgrade performance.
Suppressibility: Some free programs do not allow you to export or migrate to other software, limiting you to a single vendor. Perhaps the low price and convenience of the software is worth the effort, but sometimes it is not worth it.
Go and see the layout of other people. Open source hardware makes this thing easier.
Practice, practice, or practice.
Keep the expectations low. The first board you design may have a lot of problems, but the 20th may be a lot less, but there will be some problems. But it's hard to clear all the problems.
The schematic is quite important. Trying to design a PCB board without good schematic support is futile.
Finally, let's talk about some of the benefits of designing your own board. If you plan to participate in one or more established projects, the benefits of designing a board are obvious. Point-to-point routing on the breadboard is too difficult and relatively low reliability compared to designing a board. And, if your design is good, you can buy a good price for your design :)
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