The characteristic impedance of the transmission line of the impedance board manufacturer depends on the width of the conductor, the thickness of the medium between the conductor and the ground power reference plane, and the relationship between the dielectric constant of the medium and another dielectric constant. At the initial stage of the design, it is recommended that customers contact the manufacture to discuss impedance requirements. The discussion will provide an exchange platform to ensure that the specifications and effects of the material characteristics, including specific DK and production processes, will have an impact on the impedance requirements and tolerances of the project.
In order to determine the actual impedance, the impedance board manufacturer may need to build a small prototype for testing. Since the impedance required in the design is very small, it is usually necessary to do this. When the design has a smaller line width and medium thickness, you may need to be more sensitive to changes. For example, for a line width of 0.125 mm (0.005 inch), the tolerance variation of the etching variation is more important for a line of 0.25 mm (0.100 inch).
Only the reference dimensions of line width and media thickness are recorded. This allows manufacture to make small changes to the line width and dielectric thickness to meet the impedance target of the impedance board manufacturer. Note: When you need to change the line width, you need to change all lines of the same width in a particular layer. The client must be allowed to make such changes. Consider the importance of corrosion factors when calculating impedance. The etch factor is the result of the reduction in line width during the etching process. However, it is not necessary to consider the etching factor of pcb.
The aspect ratio of the impedance board manufacturer is GE 4.5/1, or the PCB thickness is GE 2.3 mm (0.093 inches), and the aspect ratio is GE 3:1. The impedance tolerance recommended is -10. Usually smaller tolerances can be obtained, especially for complete embedded microstrip and strip steel structures. Discuss this specification with XPCB Limited to get the best results.
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