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Although Protel99SE has the function of automatic layout, it can not fully meet the working needs of high-frequency circuits. It is often necessary to rely on the designer's experience. According to the specific situation, the manual layout method is used to optimize the position of some components, and then combined with automatic layout. Complete the overall design of the PCB. The rationality of the layout directly affects the life, stability, EMC (electromagnetic compatibility) of the product, etc., must be from the overall layout of the circuit board, the feasibility of wiring and the manufacturability of the PCB, mechanical structure, heat dissipation, EMI (electromagnetic Comprehensive considerations such as interference), reliability, and signal integrity.
Generalization of PCB design principles (1-30)
Via is one of the important components of a multilayer PCB, and drilling costs typically account for 30% to 40% of PCB board costs.
There are many popular EDA tools available on the market. However, these PCB design softwares are similar in terms of their use of terms and function keys. How do you use these tools to better implement PCB design? Careful analysis of the design before starting the wiring and careful setup of the tool software will make the design more compliant. The following is a general design process and steps.
The main parasitic components generated by board layout are resistors, capacitors, and inductors. When switching from a circuit diagram to an actual board, all parasitic components have a chance to interfere with circuit performance. When a system mixes digital and analog components, careful routing is key to the success of the board. In particular, digital traces that are often close to high-impedance analog traces will cause severe coupling noise, which can only be avoided by keeping the two traces at a distance. This article quantifies the toughest board parasitic components, board capacitors, and lists the performance examples that can be clearly seen on the board.
Impedance PCB final test eligibility criteria
Eight Principles of PCB Design
When a square wave of a signal is propelled forward by a high-level positive pressure signal in the signal line of the transmission line assembly, the theoretical reference layer (such as the ground layer) is theoretically necessary. The negative pressure signal induced by the electric field is accompanied by the forward path (equal to the return path of the positive pressure signal reverse path), so that the integral loop system can be completed. If the "signal" advances its flight time for a short period of time, it can be imagined that it suffers from the instantaneous impedance value (Instantanious Impedance) from the signal line, the dielectric layer and the reference layer. This is called "Characteristic impedance."
As memory designs become more complex and compact, and data rates are increasing, the use of BGA probes to detect DDR DRAM is becoming more popular and has become a requirement. The DDR3 and DDR4 data rates have increased from 800 MT/s to approximately 3200 MT/s. Memory system designers are concerned about whether current BGA probe designs can meet high bandwidth requirements for optimal signal fidelity. Signal fidelity is important for accurate DDR conformance measurements based on JEDEC specifications. In addition, the memory designer needs to perform signal integrity measurements to complete the margin test. Moreover, the margin after eliminating the DDR BGA probe detection effect can be used to design components with lower tolerances. This article describes a new probe calibration method for scalable DDR BGA probe bandwidth to increase the margin of signal integrity testing and minimize errors caused by DDR BGA probes.
The main cause of electromagnetic interference caused by the ground line is the impedance of the ground line. When the current flows through the ground line, a voltage is generated on the ground line. This is the ground line noise. Driven by this voltage, ground loop current is generated, causing ground loop interference. When two circuits share a ground line, a common impedance coupling is formed. The method for solving the ground loop interference is to cut the ground loop, increase the impedance of the ground loop, and use a balanced circuit. The solution to the common impedance coupling is to reduce the impedance of the common ground portion or to use a parallel single-point grounding to completely eliminate the common impedance.
Computer-aided manufacturing technology, the English name is Computer Aided Manufacturing, referred to as CAM, is an advanced technology that is controlled by computer control. The development of computer technology and the emergence of laser plotters have led to the use of PCB-assisted manufacturing technology. Various CAM systems can generally process the gerber data (Gerber data), eliminate various defects in the design, make the design easier to produce, and greatly improve the production quality.
5-7 Measures taken to increase the system's ability of it.
For digital circuit designers, the inductance of the via is more important than the capacitance. Each via has a parasitic mid-inductance. Because the physical structure of the via is small, its characteristics are very lumped lumped circuit components. The main effect of the series inductance of the via is to reduce the effectiveness of the power supply bypass capacitor, which will make the overall power supply filtering effect worse.
The application of differential signal in high-speed circuit design is more and more extensive. The most critical signal in the circuit always uses differential structure design. What other way is it so popular? How can we ensure good performance in PCB design? With these two questions, we will discuss the next section. What is a differential signal? In layman's terms, the driver sends two equal-valued, inverted signals. The receiver determines whether the logic state is "0" or "1" by comparing the difference between these two voltages. The pair of traces carrying the differential signal is called differential trace.
In order to perform circuit simulation, it is necessary to first build a model of the component, that is, for the various components supported by the circuit simulation program, there must be a corresponding mathematical model to describe them in the simulation program, that is, a calculation formula that can be calculated by a computer. To express them. An ideal component model should reflect both the electrical characteristics of the component and the numerical solution on the computer. In general, the higher the accuracy of the device model, the more complex the model itself, and the more the number of model parameters required. In this way, the amount of memory occupied increases and the calculation time increases. While integrated circuits often contain a large number of components, a slight increase in the complexity of the device model can double the computation time. Conversely, if the model is too rough, the analysis results will be unreliable. Therefore, the complexity of the component model used depends on actual needs.
In a company, from a product-level perspective, what are the prerequisites for a signal integrity engineer, what they are doing, and a bystander's understanding is as follows:
The anti-jamming measures that are not common in some literatures are detailed below. Considering the practical application, especially in the trial production of products, double panels are still widely used. The following contents are mainly for double panels.
This article focuses on some of the signal integrity issues that PCB design needs to consider in gigabit device data transfers.
(1) The design of the circuit schematic: The design of the circuit schematic is mainly the PROTEL099 schematic design system (AdvancedSchematic) to draw a circuit schematic. In this process, we should make full use of the various schematic drawing tools and various editing functions provided by PROTEL99 to achieve our goal, that is, to obtain a correct and exquisite circuit schematic.
With the increase in PCB routing courier, EMC design has to be considered by our electronic engineers. In the face of Electromagnetic Compatibility (EMC) design, there are five important attributes to consider when conducting EMC analysis of a product and design:
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