Impedance matching Impedance matching means that when source is transmitted, the load impedance must be equal to the characteristic impedance of the transmission line. At this situation, the transmission will not reflect, which indicates that all source is absorbed by the load. Conversely, there is source loss during transmission. In HDI PCB design, impedance matching is related to the quality of the signal. When do PCB traces need impedance matching? It does not mainly decided by the frequency, but the key is the steepness of the signal, which the rise / fall time of the signal. It is generally considered that if the rise / fall time of the signal (based on 10% to 90%) is less than 6 times the wire delay, it is high speed signal, we must pay attention to impedance matching. The wire delay is generally set to 150ps / inch. Characteristic impedance During the propagation of a signal along a transmission line, if there is a consistent signal propagation speed everywhere on...

The choice of surface treatment process depends mainly on the type of component that is finally assembled. And the surface treatment process will affect the production, assembly and end use of the PCB. The use occasion of five common surface treatment processes will be described below. Hot Air Solder Level(HASL) HASL has been dominant in PCB surface treatment processes. In the 1980s, more than three-quarters of PCBs used HASL, but the industry has been reducing the use of hot air leveling processes for the past decade. It is estimated that about 25%-40% of PCBs currently use HASL. HASL are dirty, unpleasant, and dangerous, and have never been a favorite process, but it’s an excellent process for larger components and larger pitch wires. In a PCB with a higher density, the flatness of the HASL will affect the subsequent assembly. Therefore, the HDI board generally does not use the hot air leveling process. With the advancement of technology, the industry has now developed a HAS...

Summary：        We all know that the heat generated by the operation of the electronic device causes the internal temperature of the device to rise rapidly. If the heat is not dissipated in time, the device will continue to heat up, and the device will fail due to overheating, and the reliability of the electronic device will decrease. Therefore, it is very important to dissipate the board. Here are the relevant experiences shared by PCBWay for you! The direct factor for the temperature rise of PCB is the existence of power consumption parts and the heat generation intensity varies with the power consumption. There are two phenomena of temperature rise. 1.Sectional temperature rise or full -area temperature rise; 2. Short-term temperature rise or long-term temperature rise. For the detailed reasons, they are generally analyzed from the following aspects. 1.Electrical power consumption (1) Analysis of po...