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Why do material makers call the dielectric constant "Dk" rather than "D.c."? Is it kind of German? Something like Dielektrische Konstante? It is actually called a Dielektrizitatszahl in Germany. With the (d)issipation (f)actor it is more or less obvious.

Anyway, these guys (including guys from Rogers) sell their thing to engineers and scientists, but keep insistently naming it with their inhouse slang, sometimes creating confusion, particularly when they refuse to read the classic notation.

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  • \$\begingroup\$ Where have you seen Dk? I've seen \$k_D\$, but never Dk. \$\endgroup\$
    – Hearth
    Commented Oct 20, 2022 at 2:03
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    \$\begingroup\$ Every profession has its own habits and conventions. This notation is fairly common in the electronics industry as a whole, and widely used by many RF engineers. At least it's the case in the USA. If I'm a pandetic theoretical physicist, I'd say that even the term "dielectric constant" itself is obsolete, and should not be used. Everyone should just be more rigorous and call it "relative permittivity (\$\epsilon_r\$)" instead. Why do people refuse to follow the classic notation? But I'm pretty sure it would be a tough sale to some engineers. \$\endgroup\$
    – 比尔盖子
    Commented Oct 20, 2022 at 2:10
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    \$\begingroup\$ Probably because "DC" already was taken (i.e. "direct current") Same reason EE's use "j" for the imaginary number. We use "i" for current. \$\endgroup\$
    – Kyle B
    Commented Oct 20, 2022 at 2:24
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    \$\begingroup\$ The Greek letter \$\kappa\$ kappa is also used for dielectric constant. Perhaps this is a reason. \$\endgroup\$
    – RussellH
    Commented Oct 20, 2022 at 2:31
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    \$\begingroup\$ @Hearth, PCB laminate vendors, for example, often designate the dielectric constant of their materials as \$D_k\$ rather than \$\epsilon_R\$. \$\endgroup\$
    – The Photon
    Commented Oct 20, 2022 at 4:05

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The notation Dk for dielectric constant is common for PCB materials. E.g. Altium Layer Stack Manager:

Altium Layer Stack

The alternative notation Dc is taken by direct current.

Greek letters seem be to troublesome for some people or at least they used to be troublesome. Notice the Df notation in the image above which stands for dissipation factor, also called loss tangent or tan \$\delta\$. So Dk and Df might have been introduced at some point just to avoid greek letters.

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  • \$\begingroup\$ Not to avoid Greek letters, but because only English letters were available on the typewriters prior to computers. \$\endgroup\$
    – RussellH
    Commented Oct 20, 2022 at 18:38
  • \$\begingroup\$ Good point. I forgot the hurdle of late 80s of replacing the ASCII bitmaps in DOS just for rendering some Greek letters, when there is already a national alphabet above 7Eh. It is regrettable that the substrate makers keep arrogantly making an amused face when told the traditional notation. \$\endgroup\$
    – Asdf
    Commented Oct 22, 2022 at 8:31

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