[volt-nuts] PCBs with ceramic substrates

[Scott Stobbe]

As a practical aside regarding surface resistance, ignoring guard
amplifiers and guard traces, the historic solution is to point to point
wire in air. With some designs using Teflon standoffs for a more rigid
approach. Some of this can still be seen today, your smoke-detector likely
has a one-layer phenonlic PCB with the sense pin of a DIP package IC bent
up off board and point-point wired in air to the Ion chamber.

On Sun, Apr 16, 2017 at 1:25 PM, fala at gmx.net <fala at gmx.net> wrote:

> Possibly Macor (machinable ceramic) from Corning, or the comparable
> Vitronit, which are both glass ceramics.
>
> Comparable to borosilicate glass.
> Extremely machinable (HSS or carbide tools, use proper speeds and
> coolant), continously stable until 800°C.
> No safety concerns or toxic effects. The dust created when machining can
> be an irritant.
>
> Available from Corning as standard size maxi slab of 36*36*6 cm.
> Price = ?
>
> Quoting Wikipedia for technical data for Macor:
> ---
> Density: 2.52 g/cm³
> Young's modulus [GPa @ 25°C]: 66.9  (FR4 = 21 - 24, Aluminium = 69, Steel
> = 200)
> Specific stiffness [E6 m²/s²]: 26.55  (Al = 26, Steel = 25 +/- 0.5)
> Poisson's Ratio []: 0.29 (FR4 = 0.118 - 0.136, Al = 0.32, Steel =
> 0.27-0.31)
> Thermal conductivity [W/(m*K)]: 1.46  (FR4 ~ 0.3 - 1, Al ~ 300, Steel ~
> 15-50)
> compressive strenght [MPa]: ~350
> Electrical resistivity [Ohm*cm]: 1 E17 (FR4 = 1 E14, PTFE = 1 E23 to 1 E25)
> Coefficient of thermal expansion [E-6 m/(m*K)]: 9.3 (FR4 ~ 13 , Copper =
> 16.6)
>
> Firat
>
>
> Am 16.04.2017 um 13:08 schrieb John Devereux:
>
>>
>> Hi Chuck
>>
>> But the context is "PCBs with ceramic substrates". Are any of *those*
>> tough? They may well be, perhaps you know of some? It does not help us
>> with the subject much if there are ceramics with these amazing
>> properties if they are not available as PCBs.
>>
>> There is also the question of exactly what properties of FR4 are
>> limiting for "metrology" use.
>>
>> John
>>
>
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