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, [email protected] <[email protected]> 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 >> > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
