Basic concepts commonly used in PCB design, printed circuit board manufacturer SYS Technology_
Technical
What are the advantages and applications of flexible microcircuits?
FPC Reinforcement Types
Criteria for Classification of electronic Component Classes
Four softwares suitable for beginners to draw PCB circuit boards
What information is needed for SMT processing?
What are the advantages of small and medium batch SMT processing?
PCB related knowledge- The purpose of each layer of the PCB
How to do heat resistance testing for PCB board
Detailed explanation of rigid-flex board and IC carrier board
PCBA prototype procedure
Defects which can be detected by the SPI
What are the spacing requirements for designing PCB circuit boards?
What are the classification and advantages of PCB metal substrates?
Difference between the processing technology of 1Layer AL PCB and 2Layer AL PCB
Introduction of FPC Cable and its usage
advantages of Shenzhen SMT assembly factory
inspection items before PCB ordering
usages of ceramic substrates
main applications of PCB boards
Cost-effective PCB product services
How to check short circuit of a circuit board during manual soldering
Identify the polarity of electronic components during PCBA processing
Means Which Can Prevent Component Shifting in SMT Processing
Skills of PCB prototype manual soldering
Reasons for the shift of Components in the SMT Process
Seven Types of PCB Probes
What Should Be Paid Attention to in Layout of High-frequency PCB
Precautions for PCB CCL Selection
Advantages of LED Plant growth light
Advantages of using LED grow lights to grow industrial hemp
Detailed explanation of PCB manufacturing process and precautions
Detailed explanation of PCB manufacturing process and precautions
How to draw multilayer PCB on Altium Designer
Three basic elements of interference and how to suppression them.
Decrease interference between digital circuit and analog circuit
SMT Component Placement Process Of Parts : Manual Placement
SMT factory incoming PCB material inspection
Basic concepts commonly used in PCB design
Ideas and principles of High speed PCB layout
Component layout rules and safety distance considerations
SMT assembly process quality specification
5 points in PCB layout
Professional interpretation of SMT
Advantages and disadvantages of different PCB surface treatment
Special process in PCB prototype
Why the via hole become open after component assembly
Keep the cost of the PCB as low as possible
what are the causes of PCB board heating radiation problem
Pad size and via diameter dimensions consideration in PCB prototyping
How to Judge the Acceptance of PCB Quality
Which Color Circuit Board Sells the Most Expensive
Method to Solve the Noise Interference of Power Supply on High-frequency PCB Board
Disassembly Skills of Chip Components on PCB
What Factors Should Be Considered in the Selection of High-frequency PCB CCL
How to Place Special Components during PCB Layout
What Are the Functions of Capacitors in Circuits?
Testing Techniques for Common Electronics Components
What to do if There is a Short Circuit on the PCB
Desoldering Principles and knowhow during PCBA Processing
Black Oxidation of the Inner Layer of the Multilayer PCB
How to Ensure the High-performance Design of PCB
What Is the Printing Process of SMT Solder Paste?
PCB without fiducial mark, Is There Any Way to do SMT for It
What Are the Benefits of Reserving Break-up Tab for PCB Production
How Does SMT Affect PCB Production Time and Speed It Up
Classification of PCBs from three aspects
Common Problems and Solutions for Dry Film pasting during PCB Manufacturing process
Several Elements to Inspect after PCB Design
What is a halogen-free circuit board?
What Do Capacitive Coupling and Decoupling Mean?
What Are the Differences Between PCB Paste Mask and Solder Mask?
How PCBA Is Packaged and Shipped
How long can PCBA finished products be stored?
What Are the Differences and Relations Between PCB, PCBA, and SMT?
PCB Baking Specifications
PCB "Solder Mask Tenting" and "Solder Mask Opening"
Five reasons for PCB deformation and six solutions
Importance of first article inspection of PCBA board
Temperature zone standard for SMT reflow soldering
Small and medium volume PCB manufacturers in China
The main reason for PCBA cleaning
For power filter, the more capacitors, the better?
What does PCBA programming mean?
Content of PCB incoming testing
What conditions must be met for PCB circuit board soldering?
What is Blind via and Buried via
PCBA Manufacturers Temperature and Humidity Sensitive Components Management

Basic concepts commonly used in PCB design

A good engineer must design products that meet both the design requirements and meet the production process, a flaw in some aspect can not be considered a perfect product design. Standardize the product circuit design, process design, PCB design of the relevant process parameters, so that the production of physical products can meet the requirements of the technical specifications of manufacturability, testability, maintainability, etc., in the product design process to build the product process, technology, quality, cost advantages.

This article, China PCB manufacturer will take you from a beginner's point of view, quickly understanding of the basic concepts commonly used in PCB design.

1. FR4 Substrate
FR-4 is the glass fiber epoxy resin copper clad board, a substrate in the circuit board, can be divided into general TG FR4 and high TG FR4, Tg is the glass transition temperature, that is, the melting point. The circuit board must be flame-resistant and cannot be burned at a certain temperature, but only softened. The temperature point at this point is called the glass transition temperature, and this value is related to the dimensional stability of the PCB board.

General Tg of the FR4 board is 130 degrees or more, high Tg is generally greater than 170 degrees, medium Tg is about greater than 150 degrees. Usually Tg≥ 170 degrees Celsius PCB printed board, called high Tg printed board. The Tg of the substrate is improved, the heat resistance of the printed board, humidity resistance, chemical resistance, stability resistance and other characteristics will be increased and improved. the higher the TG value, the better the temperature resistance of the board, especially in the lead-free process, high Tg application is more.


2. Impedance matching
Impedance matching is mainly used in transmission lines to achieve all high frequency microwave signals can be transmitted to the point of load, and there is almost no signal reflection back to the source, thereby improving energy efficiency. The signal source internal resistance and the connected transmission line characteristic impedance of equal size and phase, or the transmission line characteristic impedance and the connected load impedance of equal size and phase, respectively, known as the input or output of the transmission line in the impedance matching state, referred to as impedance matching. PCB common impedance control values are: 100 Ohm differential impedance, 90 Ohm differential impedance and single-ended 50 Ohm impedance.

3. Surface treatment
PCB board surface treatment is generally divided into several, in order to better understand their own PCB design issues, is briefly introduced: 
1) HASL, HASL is the most common surface treatment process within the circuit board industry, it has good solderability and can be used for most electronic products. HASL board for other surface treatment, it is low cost, good weldability advantages; its shortcomings are no Immersion gold surface flat, especially when a large area of open windows, more likely to appear tin uneven phenomenon.

2) Immersion tin, Immersion tin and HASL difference is that it is good flatness, but the shortcoming is very easy to oxidation black.

3) Immersion gold, as long as it is "Immersion" its flatness is better than the "spray" process. Immersion gold is lead-free, Immersion gold is generally used for gold fingers, keypad, because the gold resistance is small, so the contact must be used gold, such as cell phone keypad light. Immersion gold is soft gold, for often to plug to use gold plating, Immersion gold is mainly Immersion nickel gold.

4)Gold plating
Gold plating has been mentioned in the Immersion gold, gold plating has a fatal deficiency when its poor solderability, but its hardness is better than Immersion gold. 

Little helper tip: If the flatness requirements, such as the frequency requirements of the impedance circuit board (such as microstrip lines) try to use the Immersion gold process; general with BGA MID board are used to Immersion gold process.

5) OSP
It mainly relies on the reaction between the reaction between the flux and the solder copper skin to produce solderability, the only advantage is the fast production, low cost; but because of its poor solderability, easy to oxidation, the circuit board industry is generally used less.


4. Core board (Core) / PP sheet (semi-cured sheet)
The reinforcement material is dipped in resin, one or both sides are covered with copper foil, and a board material is made by hot pressing, called copper foil laminate. It is the basic material for making PCBs and is often called the substrate. When it is used in the production of multilayer boards, it is also called core board (CORE)

The resin is synthesized with a carrier in a sheet bonding material called PP sheet.

Core board and semi-cured sheets are common materials used to make laminated multilayer boards.

5. Differential line
Differential signal is the driver side to send two equal and opposite signals, the receiver side by comparing the difference between the two voltages to determine the logic state "0" or "1". The pair of lines carrying the differential signal is called differential lines. Differential signals, some also known as differential signals, with two identical, opposite polarity signal transmission of data along the way, relying on the two signal level difference for the judgment. In order to ensure that the two signals are identical, the wiring should be kept in parallel, line width and line spacing remain the same.

6. Signal integrity
Signal integrity refers to the quality of the signal on the transmission line. A signal with good signal integrity means that when needed, it has the necessary voltage level value. Poor signal integrity is not caused by a single factor, but by a combination of factors in the board-level design. Major signal integrity issues include reflections, oscillations, ground bounce, crosstalk, etc. 

7. Signal Reflections
A reflection is an echo on a transmission line. A portion of the signal power (voltage and current) is transmitted to the line and reaches the load, but a portion is reflected. If the source and the load have the same impedance, reflections do not occur. A mismatch between the impedance of the source and the load will cause reflection on the line, and the load will reflect part of the voltage back to the source. If the load impedance is less than the source impedance, the reflected voltage is negative, and vice versa, if the load impedance is greater than the source impedance, the reflected voltage is positive. Variations in the geometry of the wiring, incorrect line termination, transmission through connectors and discontinuities in the power plane can cause such reflections.
Reflections can cause signal overshoot, undershoot, ringing, and edge retardation, also known as stepped voltage waves.

8. Crosstalk
Crosstalk is the coupling between two signal lines, the signal lines between the mutual inductance and mutual capacitance caused by the noise on the line. Capacitive coupling triggers coupling current, while inductive coupling triggers coupling voltage. the parameters of the PCB layer, signal line spacing, the electrical characteristics of the driver and receiver side and line termination have a certain impact on crosstalk.

9. Inner layer 
Inner layer is a negative layer of the PCB, the main role is to act as a layer of power or ground, when necessary for power split.

10. Blind buried holes
1) blind holes: from the middle layer extends to the PCB a surface layer of the over hole. Commonly known as first-order, second-order, such as first-order blind hole is the second layer to the TOP layer of the hole or the penultimate layer to the Bottom hole.
(2) buried holes: from one middle to another middle between the perforations, will not extend to the PCB surface layer.

11. Test points.
Generally refers to independent PTH holes, SMT PAD, gold fingers, Bonding fingers, IC fingers, BGA soldering points, and test points tested by customers after plug-in.

12. Fiducial point
Fiducial point is a circuit board design PCB applied to the automatic placement machine location identification points, also known as optical point location point. fiducial point selection directly affects the automatic placement machine placement efficiency. fiducial point is generally designed as Ф1 mm (40 mil) circular figure. Considering the contrast between the material color and the environment, leaving 0.5 mm (19.7 mil) larger than the optical positioning reference symbols without solder resistance area, also does not allow any characters, see the figure. The optical positioning reference symbol on the same board and its adjacent inner layer background should be the same, that is, the presence or absence of copper foil under the three reference symbols should be consistent. Around 10mm no wiring isolated optical positioning symbols should be designed with an inner diameter of 2mm ring width of 1mm protective circle, and surrounded by the upper and lower sides of the diameter of 2.8mm 8-sided isolated copper ring.

13. PTH (metallized hole) / NPTH (non-metallized hole)
Hole wall deposited with a metal layer of the hole is called metallized hole, which is mainly used for the electrical connection between the layers of conductive graphics. Conversely, they are non-metallic holes, which are generally used as positioning holes or mounting holes.