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Basic Knowledge of PCB

Posted:05:05 PM July 06, 2021 writer: louise


1. The PCB material currently used by MITAC

A. Urea cardboard

Features: The color is light yellow and is often used for single-sided panels, but because it is made of urea paper, it is easy to rot in a cool and humid place, so it is not commonly used now.

B. CAM-3 board

Features: The color is milky white, the toughness is good, it has a high CTI (600V), and the carbon dioxide emission is only a quarter of the normal. It is now more commonly used in single-sided panels.

C. FR4 fiberboard

Characteristic: It is made of fiber, has good toughness, and when it breaks, there are wires pulling each other. It is often used for multi-panel. Its thermal expansion coefficient is 13 (16ppm/c). The motherboard used by our factory is made of this board.

D. Multilayer board

Features: high Tg, high heat resistance and low thermal expansion rate, low dielectric constant, and dielectric loss materials, mostly used for four or more layers.

E. Soft board

Features: The material is soft and transparent, it is often used in the electrical connection of two boards, and it is easy to fold. For example, the connection between the LCD and the main body of the computer in a laptop computer.

F. Other

With a personal computer. With the popularity of multimedia digital information terminal products such as mobile phones, PCBs have become lighter, thinner, shorter, and smaller. Some large group companies abroad have successively developed more PCB boards, such as halogen-free and antimony-free environmentally friendly products, high heat resistance, high Tg boards, and low

Coefficient of thermal expansion, low dielectric constant, low dielectric loss sheet material. Its representative products are FR-5, Tg200 board, PEE board, PI board, CEL-475, etc.

2. The current MITAC PCB-Layout process

A﹒ R&D provides SCHEMATIC (EE), FAB OUTLINE (ME) product development department provides us with schematic diagrams, and mechanical engineers provide us with external resources
B﹒ Create a new part
We call out the part from LIBRARIAN according to the schematic diagram. If there is no such part in LIBRARIAN, we will create a new part.
C﹒ Part layout
After the parts are ready, we need to layout the parts
This is our main task. After we set up the game, we will proceed to route.
E﹒ Final finishing
After ROUTING, we need to use FABLINK to finally sort out the various data we need
F﹒ Convert GERBER
Converted to GERBER documents required by PC board manufacturers
G﹒ Data save
After all the work is done, save the data for later modification and verification

3. Some basic terms about printing plates

On an insulating substrate, according to a predetermined design, a printed circuit, a printed component, or a conductive pattern formed by a combination of the two are made, which is called a printed circuit. On an insulating substrate, a conductive pattern that provides electrical connections between components is called a printed circuit. It does not include printing components. The finished boards of printed circuits or printed circuits are called printed circuit boards or printed circuit boards, also known as printed boards. Printed boards can be divided into two categories according to whether the substrate used is rigid or flexible: rigid printed board brushes and flexible printed boards. Rigid-flexible printed boards have also appeared this year. According to the number of layers of conductor patterns, they can be divided into single-sided, double-sided, and multilayer printed boards. The entire outer surface of the conductor pattern is on the same plane as the surface of the substrate. The printing plate is called a flat printing plate.
After electronic equipment adopts printed boards, due to the consistency of similar printed boards, manual wiring errors can be avoided, and electronic components can be automatically inserted or mounted, automatic soldering, and automatic detection, ensuring the quality of electronic equipment and improving It improves labor productivity, reduces costs, and is easy to maintain. Printing boards have developed from single-layer to double-sided, multi-layer, and flexible, and still maintain their respective development trends. Due to the continuous development of high precision, high density, and high reliability The development of the direction, the continuous reduction of the volume, and the reduction of the cost, make the printed board still maintain a strong vitality in the development of electronic equipment in the future.


  Why Choose NEXTPCB Manufacturer  


4. V-1 level FR-4?

FR-4 (flame-resistant laminated board) is based on "glass fiber cloth" as the main body, impregnated with liquid flame-resistant "epoxy resin" as a bonding agent to form a film, and then laminated to form boards of various thicknesses. The so-called V-1 refers to a sample of a copper-free glass fiber epoxy resin substrate with a width of 0.5 inches, a length of 5 inches, and any thickness. After being burned on a specific flame at an oblique angle of 45°, the fire source is removed and Measure the number of seconds that it will continue to burn and wait until it is completely extinguished before continuing to burn. After ten consecutive trial burns,
Those with a total delay of fewer than 250 seconds are called V-1 FR-4, and those with less than 50 seconds are called V-0 FR-4.

5. A brief history of PCB development

The basic concepts of printed circuits have been proposed in patents at the beginning of this century. In 1947, the American Aviation Administration and the American Bureau of Standards initiated the first technical seminar on printed circuits. At that time, 26 different printed circuit manufacturing methods were listed. It is divided into six categories: coating method, a spraying method, chemical deposition method, a vacuum evaporation method, molding method, and powder compaction method. At that time, these methods failed to achieve large-scale industrial production.
Until the early 1950s, due to the solution of the adhesion problem between copper foil and laminate, the performance of copper-clad laminate was stable and reliable, and large-scale industrial production was realized. Copper foil etching became the mainstream of printed board manufacturing technology. Development till now.
In the 1960s, through-hole metallization double-sided printing and multilayer printed boards achieved mass production. In the 1970s, due to the rapid development of large-scale integrated circuits and electronic calculators, the 1980s represented surface mount technology and the 1990s multi-chips. 
The exhibition promoted the continuous progress of printed circuit board production technology. A batch of new materials, new equipment, and new testing instruments have emerged one after another. The production technology of printed circuits has further developed to high density, thin wires, multilayer, high reliability, low cost, and continuous automation. The direction of product development.

6. Schematic design process

The generation of schematic diagrams is generally regarded as the first step in the PCB production process. It is also the specific realization of the product vision by electronic engineering and technical personnel. It is composed of many logic components (such as various IC gate circuits, resistors, capacitors, etc.). ) Is composed of different logical connections. Make a schematic diagram,
The source of its logic components is that some CAD software contains a huge logic component library (such as TANGO PADS, etc.), while some CAD software is in addition to logic components.
In addition to the library of logical components, users can also add new logical components (such as Cadence, Mentor, Zuken, etc.) by themselves, and users can use these logical components to implement the logical functions of the product to be designed.


  • 1 Establish logic components

    • A logic component is a component that provides a logic function (such as an LSOO gate, a flip-flop or an ASIC circuit).
    • 1) The definition of the logical component model (or component name).
    • 2) Package form of logic component pins
    • 3) Description of logic component pins
    • 4) Definition of the shape and symbol size of logical components
  • 2 Functional description of logic components

    • To simulate the logic circuit, it is necessary to describe the functional characteristics of each logic component, such as the timing relationship of the logic component, the initial state rising edge (RISE), falling edge (FALL), delay time, and drive attenuation, Decay time, etc.

  • 3 Description of the logic component library

    • Since there are many logic components, they are all built under one library, which is easy to cause confusion and difficult to manage. Therefore, logic components with similar functional characteristics are generally placed in one library.
    • Next, it is managed by functional characteristics, such as A/D, D/A conversion devices, CMOS devices, storage devices, TTL devices, linear devices, op-amp devices, comparison devices, etc.,
    • They are all placed under similar libraries. It can also be classified by company manufacturers such as MOTOROLA, NEC, INTEL, etc.

7. The function of the printed circuits in electronic equipment

(1) Provide mechanical support for the fixing and assembly of various electronic components such as integrated circuits.
(2) Realize wiring and electrical connection or electrical insulation between various electronic components such as integrated circuits.
(3) Provide the required electrical characteristics, such as characteristic impedance, etc.
(4) Provide solder mask graphics for automatic soldering, and provide identifiers and graphics for component insertion, inspection, and maintenance.

8. How will PCB manufacturing technology change


1) Reduce lead content (2) Reduce the amount of formaldehyde used (3) Progress of MID (4) Other materials

9. High-speed circuit

It is generally believed that if the frequency of the digital logic circuit reaches or exceeds 45MHZ~50MHZ, and the circuit working above this frequency has already occupied a certain weight (for example, 1/3) of the entire electronic system is called a high-speed circuit. In fact, the harmonic frequency of the signal edge is higher than the frequency of the signal itself. It is the rising and falling edges of the signal (or signal jumps) that cause unexpected results in signal transmission. Therefore, it is generally agreed that if the line propagation delay is greater than 1/2 of the rise time of the digital signal drive end, it is considered this
Analog signals are high-speed signals and produce transmission line effects. The transmission of the signal occurs at the instant when the signal state changes, such as the rise or fall time. The signal passes a fixed period of time from the driving end to the receiving end. If the transmission time is less than 1/2 of the rising or falling time, the reflected signal from the receiving end will reach the driving end before the signal changes state. Conversely, the reflected signal will reach the drive end after the signal changes state. If the reflected signal is strong, the superimposed waveform may change the logic state.

10. V-CUT

One method for circuit board molding is to cut straight lines at the same position on the upper and lower sides of the board but not cut so that they can be broken manually or using a jig to form a V-shaped groove from the top and bottom of the board, so it is called C-CUT

11. Golden finger

It refers to some circuit boards-such as network cards. The gold-plated wires on the upper panel are called golden fingers because they are shaped like fingers.


Tag: PCB Knowledge
  • PCB
  • PCB
  • SMD

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