Choosing PCB board*** strikes a balance between meeting design requirements, mass production, and cost. Simply put, design requirements include electrical and structural reliability. Usually this board problem is more important when designing very high-speed PCB boards (frequency greater than GHz). For example, the commonly used FR-4 material now has a large dielectric loss Df (Dielectricloss) at a frequency of several GHz, which may not be applicable.

　　 For example, a 10Gb/S high-speed digital signal is a square wave, which can be seen as a superposition of sine wave signals of different frequencies. Therefore 10Gb/S includes many different frequency signals: 5Ghz fundamental wave signal, 3rd order 15GHz, 5th order 25GHz, 7th order 35GHz signal and so on. Maintain the integrity of the digital signal and the steepness of the upper and lower edges are the same as the low-loss and low-distortion transmission of radio frequency microwave (the high-frequency harmonic part of the digital signal reaches the microwave frequency band). Therefore, in many aspects, the selection of high-speed digital circuit PCB materials is similar to that of RF microwave circuits.

In actual engineering operations, the selection of high-frequency plates seems simple, but there are still many factors that need to be considered. Through the introduction of this article, as a PCB design engineer or high-speed project person in charge, you have *** Understanding. Understand the electrical properties, thermal properties, and reliability of sheets. And rational use of stacking, design a product with high reliability and good processability, the consideration of various factors is optimized.

　　 The following will introduce separately, the main considerations for choosing the right sheet:

　　1. Manufacturability:

　　For example, how is the multiple pressing performance, temperature performance, etc., CAF/heat resistance, mechanical toughness (adhesive) (good reliability), and fire rating;

　　2. Various properties that match the product (electrical, performance stability, etc.):

　　 Low loss, stable Dk/Df parameters, low dispersion, small variation coefficient with frequency and environment, small tolerance of material thickness and glue content (good impedance control), if the trace is long, consider low roughness copper foil. In addition, the design of high-speed circuits requires simulation in the early stage, and the simulation results are the reference standard for design.

　　 3. Timely availability of materials:

　　 Many high-frequency plates have a very long procurement cycle, even 2-3 months; in addition to the conventional high-frequency plate RO4350 in stock, many high-frequency plates need to be provided by customers. Therefore, high-frequency plates need to communicate with the manufacturer in advance and prepare the materials as soon as possible;

　　4. Cost factor Cost:

　　 depends on the price sensitivity of the product, whether it is a consumer product, or a communication, medical, industrial, or *** type of application;

　　5. Applicability of laws and regulations, etc.:

　　 It must be integrated with different environmental protection regulations to meet RoHS and halogen-free requirements.