How to test the Er of a material ?
I have recently manufactured some antennas using Roger 5880. It was suppose to have a thickness of 1.575 mm but is around 1.27 mm. I have checked the datasheet. Roger do not supply this thickness sheet. Therefore I have doubts about the Er of the material as well. Could anyone tell me a simple method for testing the material Er.
Thanks.
To measure the permittivity of any flat material, cut a small square and measure its capacitance with a suitable cap.meter. Use as short leads as possible.
Measure the plate thickness without copper- after measuring, remove copper foils and use a micrometer to find the thickness.
Calculate the permittivity by the classical formula.
If you intend to use the PCB at a high frequency, the permittivity can vary with it and the loss tangent, too. Roger gives details about their products.
Alternatively, you might not need to know the Er.
Measure the antenna performance (radiation pattern, return loss) and observe the frequency shift. Compensate for the difference in your design,fabricate and measurement again.
High Accuracy Broadband Measurement of Anisotropic Dielectric Constant Using a Shielded Planar Dual Mode Resonator:
http://www.sonnetsoftware.com/suppor...ARFTGPaper.pdf
IPC Method:
http://www.ipc.org/4.0_Knowledge/4.1...-5_2-5-5-5.pdf
What's the point of measuring the Er of the mystery material?
Send it back to the PCB fabricator and insist they use the correct material.
But how do you make more of them? The OP doesn't know what material they are made from? If the OP knew what the mystery material was, then the OP wouldn't need to ask about the Er? The mystery material might have terrible stability over temperature or it might have environmental issues or fabrication issues etc etc.
What instrument did the use to measure the width of the material? Maybe it was measured poorly by the OP and it really is the correct Rogers 5880 material in 1.575mm?