What Is a Printed Circuit Board (PCB)?
dnfsdd871 > 12-24-2021, 08:01 AM
One thing that all schematics have in common is the utter inability to drive a motor, or blink an LED, or filter out noise, or do any of the other useful and interesting things that we expect electrical systems to do. A schematic is, after all, just a drawing. To actually accomplish something with a circuit, we need to translate its schematic into physical components and physical interconnections. Simple schematics can often be realized on a breadboard, but the vast majority of circuit designs enter the physical realm in the form of a printed circuit board, or PCB for short.
The Structure of a PCB
A very basic printed circuit board is a flat, rigid, insulating material that has thin conductive structures adhering to one side. These conductive structures create geometric patterns consisting of, for example, rectangles, circles, and squares. Long, thin rectangles function as interconnections (i.e., the equivalent of wires), and various shapes function as connection points for components.
A printed circuit board such as the example in the image has only one conductive layer. A single-layer PCB is very restrictive; the circuit realization will not make efficient use of available area, and the designer may have difficulty creating the necessary interconnections.
Incorporating additional conductive layers makes the 2 Layers PCB more compact and easier to design. A two-layer board is a major improvement over a single-layer board, and most applications benefit from having at least four layers. A four-layer board consists of the top layer, the bottom layer, and two internal layers. (“Top” and “bottom” may not seem like typical scientific terminology, but they are nonetheless the official designations in the world of PCB design and fabrication.)
Understanding PCB Features and Terminology
There’s quite a bit of specialized vocabulary that arises in discussions of printed circuit boards. This section describes physical structures found on 4 Layers PCBs and gives you the words that we use to identify them.
PCB believes that many people are familiar with PCB circuit boards, which may be heard frequently in daily life, but may not be familiar with PCBA, and may even be confused with PCB.
PCB is the abbreviation of Printed Circuit Board. Translated into Chinese is called a printed circuit board. Because it is made by electronic printing, it is called a "printing" circuit board. 8 Layers PCB is an important electronic component in the electronics industry, support for electronic components, and a carrier for electrical connection of electronic components.
PCBA is the abbreviation of Printed Circuit Board +Assembly, which means that PCBA is the whole process of passing the PCB empty board SMT and then passing the DIP plug-in.
Note: Both SMT and DIP are ways to integrate parts on the PCB. The main difference is that SMT does not need to drill holes in the PCB. In DIP, the PIN pin of the part needs to be inserted into the drilled hole.
SMT (Surface Mounted Technology) surface mount technology, mainly using the placement machine to mount some micro-miniature parts on the PCB, the production process is: PCB board positioning, printing solder paste, placement machine placement, over-reflow Furnace and finished inspection.
DIP is a "plug-in", which is to insert parts on the PCB version, which are integrated parts in the form of plug-ins that are large in size and not suitable for placement technology. Its main production processes are: adhesive backing, inserts, inspection, wave soldering, brushing and inspection.
*The difference between PCB and PCBA*
From the above introduction, it can be known that Industrial Control PCBA Board refers to a processing flow, which can also be understood as a finished circuit board, and the PCBA can be calculated only after the processes on the PCB are completed. The PCB refers to an empty printed circuit board with no parts on it.
In general: PCBA is a finished board; PCB is a bare board.
A humid and dusty environment is obviously not conducive to the preservation of PCBA. These factors will speed up the oxidation and dirt of PCBA and shorten the shelf life of PCBA. Generally, it is recommended to store Automotive PCBA Board in a dry, dust-free space with a constant temperature of 25 ℃. The reliability of components on different PCBAs also determines the shelf life of PCBA to a large extent. Components with high-quality materials and processes have the ability to withstand harsh environments, with a wider range of capabilities and stronger oxidation resistance, so that PCBA stability is guaranteed.
The shelf life of PCBA boards is a comprehensive work, which needs to follow scientific design specifications, manufacturing process specifications, and operation specifications, so that the shelf life can be extended to the greatest extent.
- A conductive interconnection is called a trace, and connection points for components are called pads (for pins that rest on the surface of the board) and through-holes (for pins that are inserted into holes drilled in the board). Basic PCB design consists of arranging pads and through-holes so that components can be properly installed, and then connecting these pads and through-holes using traces.
- Not all drilled holes are for through-hole components. We often need to transfer a signal or supply voltage from one PCB layer to another, and this is accomplished using small, conductive holes called vias.
- Many PCBs also include mounting holes, which have a mechanical rather than an electrical function and therefore don’t need to be plated. The term “plating” in this context refers to conductive material that has been deposited onto the interior of a drilled hole.
- A copper pour is a relatively large section of a Rigid-Flexible PCB layer that is filled with conductive material. Copper pours can be used to provide a very low-resistance or low-inductance connection between components and to improve thermal performance.
- A PCB layer that consists entirely of one large copper pour is called a plane layer. We frequently use an internal layer as a ground plane and create ground connections by placing vias next to component pins.
- A through-hole or via begins as a circle of copper and then becomes a hole when a drill bit passes through the circle (ideally through the center of the circle). The term annular ring refers to the width of copper that remains after the hole has been drilled.
- Printed circuit boards include a variety of “supplemental” information that have no role in the electrical functionality of the device. For example, reference designators uniquely identify components, dots indicate proper component orientation, and project titles or serial numbers help us to keep track of the many circuit boards that accumulate in a lab. We refer to this information as the silkscreen.