With the microprocessor and a signal converter to enhance the transmission speed of the device, the operating speed digital circuit has reached a higher level: 100Gbps. Using a common PCB material will not reach the required high-speed signal, the selection circuit board will determine the performance of the product.
PCB material must be selected to meet the design requirements of mass production, the cost of the intermediate balance point. In simple terms, electrical and structural design requirements include reliability of two parts. This problem would be more important when the plate is usually very high-speed PCB design board (greater than a GHz frequency). For example, now commonly used FR-4 material, medium damage Df in the frequency of several GHz (Dielectricloss) will be great, it may not apply.
Different sheet loss
For example, 10Gb / S high-speed digital signal is a square wave, which can be considered as a superposition of sine wave signals of different frequencies. Thus 10Gb / S comprising a plurality of signals of different frequencies: the fundamental signal 5Ghz, 3 order of 15GHz, 5 order 25GHz, 7 35GHz order signals. Like holding steepness and integrity of the microwave and radio frequency along the vertical of the digital signal (harmonic portion of the digital signal reaches the microwave band) of the low-loss low-distortion transmission. Thus, in many respects, similar to the PCB selection circuit needs high-speed digital and RF microwave circuits.
Time / frequency domain
In the actual operation of the project, select the sheet seems simple but high-frequency considerations still very much through this introduction, as a high-speed PCB design engineer or project manager, select the properties sheet and have some knowledge . Learn plate electrical performance, thermal performance and reliability. And the rational use of stacked design a high reliability, workability good product, taking into consideration a variety of factors to optimize.
Following are descriptions, select the appropriate sheet main considerations:
1, manufacturability:
Such as how many times nip performance, temperature properties, resistance to CAF / heat resistance and mechanical toughness (viscosity) of (reliability), fire rating;
2, and various properties of the product matched (electrical performance stability, etc.):
Low loss, stable Dk / Df parameters, low dispersion, and the frequency with environmental change coefficient is small, a small material thickness and the content of gum tolerance (good impedance control), if the line take longer considered low roughness of the copper foil. Another point, the early high-speed circuit design are required simulation results is the standard reference design. "Hingsen technology - Agilent (high speed / RF) Joint Laboratory" to solve the simulation results and test results inconsistent problem, done a lot of closed-loop simulation and test verification, through the unique method can do the same simulated and measured.
3, the material can be acquired in a timely manner:
Many high-frequency plate procurement cycle is very long, even for 2-3 months; in addition to conventional high-frequency plate RO4350 stock, a lot of high-frequency board requires customers. Therefore, high frequency plate manufacturers need to communicate in advance and good preparation as soon as possible;
4, cost factors Cost:
Look at the price sensitivity of the product, consumer products, or communications, medical, industrial, military type of application;
5, the applicability of laws and regulations such as:
To blend with the environmental regulations in different countries, meet RoHS and halogen-free requirements.
Each of the above factors, high speed digital circuits operating speed is selected PCB factors considered, the higher the rate of the circuit, the value should be selected PCBDf smaller. Having the low loss circuit sheet will be suitable digital circuitry 10Gb / S; a lower loss sheet suitable 25Gb / s digital circuit; high-speed digital circuit having a low loss sheet would adapt faster, the rate may be 50Gb / s or higher.
Df look at the material:
Df is between 0.01 and 0.005 for the upper limit of circuit plates 10Gb / S digital circuit;
Df is between 0.005 to 0.003 for the upper limit of circuit plates 25Gb / S digital circuit;
Not more than 0.0015 Df circuit plate for 50Gb / S, even more high speed digital circuits.
Commonly used high-speed sheet are:
1), Rogers Rogers: RO4003, RO3003, RO4350, RO5880 and so on
2), sets Yao TUC: Tuc862,872SLK, 883,933, etc.
3), Matsushita Panasonic: Megtron4, Megtron6 etc.
4), Isola: FR408HR, IS620, IS680 etc.
5)、Nelco：N4000-13、N4000-13EPSI等
6), Dongguan Shengyi, Taizhou Wang Ling, microwave Taixing
Of course there are many other high-frequency boards, such as Arlon (last year was acquired by Rogers), Taconic, are the old brand RF microwave MILL, performance is guaranteed. More about pcb knowledge of Czech distribution network