Re: [volt-nuts] PCBs with ceramic substrates

[Bruce Griffiths]

When the glass fibre bunch periodicity approaches a significant fraction of a 
wavelength the periodic spatial modulation of the substrate dielectric constant 
under or surrounding transmission lines has interesting  effects on the 
properties of the transmission line. At even higher frequencies the surface 
texture of the copper also becomes an issue. Ditching glass fibre in favour of 
small ceramic particles eliminates the effect of the periodic spatial 
modulation of the substrate dielectric constant. Just as with dielectric 
absorption it should be possible to fit a Cole-Coles or similar model to the 
variation of dielectric properties (including loss) with frequency.

Bruce

> On 17 April 2017 at 15:54 cheater00 cheater00  wrote:
> 
> 
> Thanks, that second article had exactly what I had in mind. I would love 
> to see that permittivity vs freq graph in more detail around one of the flat 
> crossings of the saw graph with the smooth fitted curve, maybe +/- 10 MHz 
> around that crossing (not around the steep jump)
> 
> If ceramic is fragile and FR4 can be hook less then I assume FR4 is 
> better, testing anyways doesn't hurt.
> 
> The periodicity of the "saw" graph is telling. Could this have to do with 
> the size of layers created by the fibers, or the size of fibers themselves or 
> their spacing? Maybe a random fiber dimension (diameter, spacing) would be 
> better here than using a constant dimension of fibers.
> 
> 
> On Mon, 17 Apr 2017 05:35 Bruce Griffiths,  mailto:bruce.griffi...@xtra.co.nz > wrote:
> 
> > > 
> > There's little out there on the frequency dependence of dielectric 
> > constant at audio and sub audio frequencies.
> > 
> > A bit more for 10MHz and above like:
> > 
> > 
> > http://www.edn.com/design/analog/4398951/2/What-PCB-material-do-I-need-to-use-for-RF-
> > 
> > 
> > http://ac.els-cdn.com/S1474667015373043/1-s2.0-S1474667015373043-main.pdf?_tid=2e1d6d30-231a-11e7-84ab-0aab0f26=1492398280_a0295abea04d2b08db9f227ee52506fc
> >  
> > http://ac.els-cdn.com/S1474667015373043/1-s2.0-S1474667015373043-main.pdf?_tid=2e1d6d30-231a-11e7-84ab-0aab0f26=1492398280_a0295abea04d2b08db9f227ee52506fc
> > 
> > 
> >  There's also the article in The October 8 1978 issue of 
> > electronics on
> > 
> > Getting rid of hook: The hidden pc-board capacitance by authors 
> > from Tektronix and Norplex.
> > 
> > This article is in the files section of the Tekscopes yahoo group.
> > 
> > Otherwise there are various values given in the literature and on 
> > the web for the low frequency relative permittivity of FR4 which are all 
> > noticeably higher than the value at 10MHz.
> > 
> > Bruce 
> > 
> > > > > On 17 April 2017 at 14:31 cheater00 cheater00 
> >  wrote:
> > > 
> > > 
> > > Thank you. Do you have a plot of the effect on impedance due 
> > > to hook out into high frequencies, measured on a real world material? It 
> > > would tell me a lot.
> > > 
> > > 
> > > On Mon, 17 Apr 2017 04:19 Bruce Griffiths, 
> > >  wrote:
> > > 
> > > > > > > 
> > > > Hook is merely a manifestation of the variation of 
> > > > dielectric constant with frequency.
> > > > 
> > > > It affects the frequency response and transient of 
> > > > resistive attenuators by requiring more complex compensation than 
> > > > merely adjusting a trimmer cap to equalise the low frequency and high 
> > > > frequency attenuation. Since the dielectric "constant" (relative 
> > > > permittivity) of all dielectrics is frequency dependent all dielectrics 
> > > > will exhibit hook to some extent. Some PCB substrates like some 
> > > > versions of FR4 and G10 exhibit a significant variation in the 
> > > > dielectric constant from the dc value to a somewhat lower value for 
> > > > frequencies even in he audio range let alone frequencies of several 
> > > > MHz. Achieving a flat frequency response where the dielectric 
> > > > associated with circuit board capacitances exhibits significant hook is 
> > > > a complex task. Circuit board hook even affects the impedance of 
> > > > printed transmission lines (eg stripline, microstrip, CPW etc).
> > > > 
> > > > Bruce
> > > > 
> > > > > > > > > 
> > > > > On 17 April 2017 at 13:54 cheater00 cheater00 
> > > > >  wrote:
> > > > > 
> > > > > Are conformal coatings the right way to handle 
> > > > > this?
> > > > > 
> > > > > I understand there are kinds of FR4 and G10 that 
> > > > > don't have hook. What does
> > > > > one do about hook - how are those substrates 
> > > > > improved? 

Re: [volt-nuts] PCBs with ceramic substrates

[Bruce Griffiths]

There's little out there on the frequency dependence of dielectric constant at 
audio and sub audio frequencies.

A bit more for 10MHz and above like:

http://www.edn.com/design/analog/4398951/2/What-PCB-material-do-I-need-to-use-for-RF-

http://ac.els-cdn.com/S1474667015373043/1-s2.0-S1474667015373043-main.pdf?_tid=2e1d6d30-231a-11e7-84ab-0aab0f26=1492398280_a0295abea04d2b08db9f227ee52506fc
 
http://ac.els-cdn.com/S1474667015373043/1-s2.0-S1474667015373043-main.pdf?_tid=2e1d6d30-231a-11e7-84ab-0aab0f26=1492398280_a0295abea04d2b08db9f227ee52506fc


 There's also the article in The October 8 1978 issue of electronics on

Getting rid of hook: The hidden pc-board capacitance by authors from Tektronix 
and Norplex.

This article is in the files section of the Tekscopes yahoo group.

Otherwise there are various values given in the literature and on the web for 
the low frequency relative permittivity of FR4 which are all noticeably higher 
than the value at 10MHz.

Bruce 

> On 17 April 2017 at 14:31 cheater00 cheater00  wrote:
> 
> 
> Thank you. Do you have a plot of the effect on impedance due to hook out 
> into high frequencies, measured on a real world material? It would tell me a 
> lot.
> 
> 
> On Mon, 17 Apr 2017 04:19 Bruce Griffiths,  mailto:bruce.griffi...@xtra.co.nz > wrote:
> 
> > > 
> > Hook is merely a manifestation of the variation of dielectric 
> > constant with frequency.
> > 
> > It affects the frequency response and transient of resistive 
> > attenuators by requiring more complex compensation than merely adjusting a 
> > trimmer cap to equalise the low frequency and high frequency attenuation. 
> > Since the dielectric "constant" (relative permittivity) of all dielectrics 
> > is frequency dependent all dielectrics will exhibit hook to some extent. 
> > Some PCB substrates like some versions of FR4 and G10 exhibit a significant 
> > variation in the dielectric constant from the dc value to a somewhat lower 
> > value for frequencies even in he audio range let alone frequencies of 
> > several MHz. Achieving a flat frequency response where the dielectric 
> > associated with circuit board capacitances exhibits significant hook is a 
> > complex task. Circuit board hook even affects the impedance of printed 
> > transmission lines (eg stripline, microstrip, CPW etc).
> > 
> > Bruce
> > 
> > > > > 
> > > On 17 April 2017 at 13:54 cheater00 cheater00 
> > >  wrote:
> > > 
> > > Are conformal coatings the right way to handle this?
> > > 
> > > I understand there are kinds of FR4 and G10 that don't have 
> > > hook. What does
> > > one do about hook - how are those substrates improved? How 
> > > does hook
> > > manifest in circuits?
> > > 
> > > On Mon, 17 Apr 2017 03:48 David,  > > mailto:davidwh...@gmail.com > wrote:
> > > 
> > > > > > > 
> > > > FR4 has problems with consistency. Samples can have 
> > > > problems with
> > > > hook, dielectric absorption, leakage, and sensitivity 
> > > > to humidity.
> > > > 
> > > > On Sun, 16 Apr 2017 12:08:07 +0100, you wrote:
> > > > 
> > > > > > > > > 
> > > > > 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 -- volt-nuts@febo.com 
> > > > > mailto:volt-nuts@febo.com
> > > > > To unsubscribe, go to
> > > > > 
> > > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> > > > > and follow the instructions there.
> > > > > 
> > > > > > > > > 
> > > > ___
> > > > volt-nuts mailing list -- volt-nuts@febo.com 
> > > > mailto:volt-nuts@febo.com
> > > > To unsubscribe, go to 
> > > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> > > > and follow the instructions there.
> > > > 
> > > > > > > 
> > > > > 
> > > 
___

Re: [volt-nuts] PCBs with ceramic substrates

[cheater00 cheater00]

That's quite a difference from what I knew, thanks!

On Mon, 17 Apr 2017 05:17 Andy Bardagjy,  wrote:

> Synthetic sapphire has come down in price quite a bit, a 25mm dia 5mm thick
> sapphire window can be had for just $71
>
> https://www.thorlabs.com/thorproduct.cfm?partnumber=WG31050
>
> Andy ◉ Bardagjy.com  ◉ +1-404-964-1641
>
> On Sun, Apr 16, 2017 at 12:03 PM, Scott Stobbe 
> wrote:
>
> > 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, f...@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
> > >>
> > >
> > > ___
> > > volt-nuts mailing list -- volt-nuts@febo.com
> > > To unsubscribe, go to https://www.febo.com/cgi-bin/m
> > > ailman/listinfo/volt-nuts
> > > and follow the instructions there.
> > >
> > ___
> > volt-nuts mailing list -- volt-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> > mailman/listinfo/volt-nuts
> > and follow the instructions there.
> >
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>
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Re: [volt-nuts] PCBs with ceramic substrates

[Andy Bardagjy]

Synthetic sapphire has come down in price quite a bit, a 25mm dia 5mm thick
sapphire window can be had for just $71

https://www.thorlabs.com/thorproduct.cfm?partnumber=WG31050

Andy ◉ Bardagjy.com  ◉ +1-404-964-1641

On Sun, Apr 16, 2017 at 12:03 PM, Scott Stobbe 
wrote:

> 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, f...@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
> >>
> >
> > ___
> > volt-nuts mailing list -- volt-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/m
> > ailman/listinfo/volt-nuts
> > and follow the instructions there.
> >
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/volt-nuts
> and follow the instructions there.
>
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Re: [volt-nuts] PCBs with ceramic substrates

[cheater00 cheater00]

Hi David,
You could perhaps send some of that white material to Mike's Electric
Stuff, he has a mass spectrogram, which could tell you what it is.

On Mon, 17 Apr 2017 04:31 cheater00 cheater00,  wrote:

> Thank you. Do you have a plot of the effect on impedance due to hook out
> into high frequencies, measured on a real world material? It would tell me
> a lot.
>
> On Mon, 17 Apr 2017 04:19 Bruce Griffiths, 
> wrote:
>
>> Hook is merely a manifestation of the variation of dielectric constant
>> with frequency.
>>
>> It affects the frequency response and transient of resistive attenuators
>> by requiring more complex compensation than merely adjusting a trimmer cap
>> to equalise the low frequency and high frequency attenuation. Since the
>> dielectric "constant" (relative permittivity) of all dielectrics is
>> frequency dependent all dielectrics will exhibit hook to some extent. Some
>> PCB substrates like some versions of FR4 and G10 exhibit a significant
>> variation in the dielectric constant from the dc value to a somewhat lower
>> value for frequencies even in he audio range let alone frequencies of
>> several MHz. Achieving a flat frequency response where the dielectric
>> associated with circuit board capacitances exhibits significant hook is a
>> complex task. Circuit board hook even affects the impedance of printed
>> transmission lines (eg stripline, microstrip, CPW etc).
>>
>> Bruce
>>
>> On 17 April 2017 at 13:54 cheater00 cheater00 
>> wrote:
>>
>> Are conformal coatings the right way to handle this?
>>
>> I understand there are kinds of FR4 and G10 that don't have hook. What
>> does
>> one do about hook - how are those substrates improved? How does hook
>> manifest in circuits?
>>
>> On Mon, 17 Apr 2017 03:48 David,  wrote:
>>
>> FR4 has problems with consistency. Samples can have problems with
>> hook, dielectric absorption, leakage, and sensitivity to humidity.
>>
>> On Sun, 16 Apr 2017 12:08:07 +0100, you wrote:
>>
>> 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 -- volt-nuts@febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
>> and follow the instructions there.
>>
>> ___
>> volt-nuts mailing list -- volt-nuts@febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
>> and follow the instructions there.
>>
>>
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Re: [volt-nuts] PCBs with ceramic substrates

[cheater00 cheater00]

Thank you. Do you have a plot of the effect on impedance due to hook out
into high frequencies, measured on a real world material? It would tell me
a lot.

On Mon, 17 Apr 2017 04:19 Bruce Griffiths, 
wrote:

> Hook is merely a manifestation of the variation of dielectric constant
> with frequency.
>
> It affects the frequency response and transient of resistive attenuators
> by requiring more complex compensation than merely adjusting a trimmer cap
> to equalise the low frequency and high frequency attenuation. Since the
> dielectric "constant" (relative permittivity) of all dielectrics is
> frequency dependent all dielectrics will exhibit hook to some extent. Some
> PCB substrates like some versions of FR4 and G10 exhibit a significant
> variation in the dielectric constant from the dc value to a somewhat lower
> value for frequencies even in he audio range let alone frequencies of
> several MHz. Achieving a flat frequency response where the dielectric
> associated with circuit board capacitances exhibits significant hook is a
> complex task. Circuit board hook even affects the impedance of printed
> transmission lines (eg stripline, microstrip, CPW etc).
>
> Bruce
>
> On 17 April 2017 at 13:54 cheater00 cheater00  wrote:
>
> Are conformal coatings the right way to handle this?
>
> I understand there are kinds of FR4 and G10 that don't have hook. What does
> one do about hook - how are those substrates improved? How does hook
> manifest in circuits?
>
> On Mon, 17 Apr 2017 03:48 David,  wrote:
>
> FR4 has problems with consistency. Samples can have problems with
> hook, dielectric absorption, leakage, and sensitivity to humidity.
>
> On Sun, 16 Apr 2017 12:08:07 +0100, you wrote:
>
> 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 -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>
>
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Re: [volt-nuts] PCBs with ceramic substrates

[cheater00 cheater00]

Are conformal coatings the right way to handle this?

I understand there are kinds of FR4 and G10 that don't have hook. What does
one do about hook - how are those substrates improved? How does hook
manifest in circuits?

On Mon, 17 Apr 2017 03:48 David,  wrote:

> FR4 has problems with consistency.  Samples can have problems with
> hook, dielectric absorption, leakage, and sensitivity to humidity.
>
> On Sun, 16 Apr 2017 12:08:07 +0100, you wrote:
>
> >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 -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>
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Re: [volt-nuts] PCBs with ceramic substrates

[David]

FR4 has problems with consistency.  Samples can have problems with
hook, dielectric absorption, leakage, and sensitivity to humidity.

On Sun, 16 Apr 2017 12:08:07 +0100, you wrote:

>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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Re: [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, f...@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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Re: [volt-nuts] PCBs with ceramic substrates

[f...@gmx.net]

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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Re: [volt-nuts] PCBs with ceramic substrates

[cheater00 cheater00]

>
>
> > On Sun, 16 Apr 2017 13:17 Poul-Henning Kamp,  wrote:

> In message <87inm44nl4@devereux.me.uk>, John Devereux writes:
>
> > There is also the question of exactly what properties of FR4 are
> > limiting for "metrology" use.
>
> FR4 are certainly not without its own problems, in particular
> with respect to mechanical/electrical phenomena (bending, tempco etc.)
>
> And saying "Ceramic" isn't really narrowing down what we mean
> anyway, pretty much anything in the Rogers catalog is in game:
>
> https://www.rogerscorp.com/acs/products.aspx
>
> I suspect only experiments would be able to tell which of many
> possible desirable properties are most beneficial ?

On Mon, 10 Apr 2017 20:06 Poul-Henning Kamp,  wrote:
> Chuck Harris writes:
>
> > Google is your friend. Do some research on ceramics.
>
> We can add that the toughest materials, on pretty much all parameters,
> is what is becoming known as "metalic glass", which is just a fancy
> way of saying "ceramics made of metals".
>
>
> --
> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
incompetence.

Indeed your friend would have told you that the materials to be had are
Al2O3, AlN, BeO, Si3N4, or ZrO2.

The first is commonly found on old cooking pots or bicycle parts, and you'd
know that the whiteish film, while resistant to water, is easile malleable.
It has low fracture resistance, sometimes even if sintered. Its
monocrystalline version, sapphire, is not commonly used in manufacturing.
While it has excellent electrical properties, any experimental chemist will
tell you that sapphire windows, tiny bits of (synthetic) sapphire, are
prohibitively expensive and have to be handled with care; the largest ones
affordable to a well funded university are a couple inches across. Sintered
Al2O3 is used in spark plugs. I think it needs to be sintered into form and
cannot be milled or otherwise machined. Spark plugs also have huge gaps in
the metal casing due to different thermal expansion between ceramics and
metals such as say copper traces placed on a pcb. So even if you can solder
the board without fracturing either the substrate or the traces, just
keeping it in variable weather will fracture either one due to them working
all the time.

AlN is commonly used as a structural support in cheap heating elements, eg.
the dreaded "drop your iron and it's dead" soldering tip heating elements.
It's the reason everyone, including cheap Chinese manufacturers, moved to
including the heater directly in the tip as one exchangeable part. I've had
a tile stove with AlN heating elements inside and after 5 years the beads
housing the heating wire started falling apart on their own, without having
been touched once, while placed on a solid concrete base. This is likely
due to thermal shock, and goes to show objects out of AlN will have a
mechanically fragile structure on the interface of separate crystals that
make them up. But since ceramics are all porous they will all eventually
include other substances that will break the crystalline structure.

BeO is highly piezoelectric /and/ pyroelectric, which is just fuuun for
standards. This is due to its Wurtzlite crystalline structure, which it
shares with AlN. What it doesn't share with aluminum nitride is its ability
to give you cancer. It's so common it has its own name, berylliosis.

Si3N4 is ok. Except it covers in SiO2, silica, which is a thermal
insulator, so your chips can be nice and cozy. It's also nicely
piezoelectrical, which is why it's used in quartz oscillators. Quartz is
another name for silica. Si3N4 is also very hard, therefore fragile. So if
you shock mount it, it might be ok, otherwise just the thermal expansion of
whatever it's mounted to rigidly might stress it. Such as the copper
traces, which you have to balance out on both sides, or you're risking
fracture. It is commonly used in ball bearings. It can't really be milled.
So you only get the pre-made sizes. If you keep the board in SF6 or mineral
oil all the way from manufacture through use, it might be good, but don't
quote me on that.

Anyone who's ever owned one of those cheap tomato knives out of white
ceramic knows how easily ZrO2 chips when it is in a thin structure.

To know most of this stuff you'd have to have cooked for yourself or been
outside on a bike a few times, and googled for the other stuff, but I guess
making padding for a mail sig takes its toll, so I won't attribute this one
to malice.

A big issue with ceramics of all kinds is their thermal expansion
coefficient. It is incompatible with copper. Here's a company extolling
their revolutionary copper cladding process:

"Unlike the fragility of thick and thin film circuits, the DBCu circuits
allow rough handling and can endure repeated eutectic bonding temperatures.
The selection of the ratio of 

Re: [volt-nuts] PCBs with ceramic substrates

[Chuck Harris]

Hi John,

I am not advocating ceramics in place of FR4, or vice versa.
That was someone else wondering why ceramics weren't used in
metrology...

As to what you can use that isn't brittle, that is up to your
imagination.  Unlike common FR4 materials, ceramics don't do
well with the usual FR4 process of thermally bonding a thin
sheet of copper to each side, masking, etching, and being happy.

Ceramic PCB's, in my experience, are more of a silk screen
a silver ore gold bearing "glaze" on the surface of the ceramic,
and fire in a kiln process.

Any ceramic you can get in a thin sheet the thickness you desire,
and in the shape/size you desire is a candidate.

Some ceramics might not do well with drilling, or other machining
processes, so may have to be formed, drilled, etc. while in the
greenware state.

I shudder to think what machining ceramic armor plate, as is
used for the breastplate in a "bullet proof vest" might be like.

There are some ceramics that would eat tungsten carbide drills
for breakfast, so diamond tooling is probably essential.

-Chuck Harris

John Devereux wrote:
> 
> 
> 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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Re: [volt-nuts] PCBs with ceramic substrates

[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

Chuck Harris  writes:

> Simple, ceramic is a generic term, like car.
>
> And, ceramic substrates are available in all manner
> of different thicknesses, densities, and materials.
>
> Like every other engineering material, you decide what
> characteristics are important to you, and you pick the
> appropriate material that meets those characteristics.
>
> If you work outside of the envelope of that material's
> capabilities, the results will be disappointing.
>
> You were opining that ceramic was too brittle, and
> breakable and shouldn't be used for metrology work, I
> disagreed, and attempted to enlighten you with tales of
> some ceramics that you would be hard pressed to break,
> even with repeated blows from a hammer.
>
> I could tell you of transparent ceramics that are
> amazingly hard, and strong.
>
> I could go further and tell of other ceramics where you
> can crumble brick sized blocks with light finger pressure.
>
> And I could tell you of still other ceramics that you can
> heat white hot with a torch, and then in a fraction of a
> second, press the glowing section against your arm without
> it even feeling warm.
>
> Which could lead some to say: ceramics are cool!
>
> But as they say, you can lead a horse to water, but you
> cannot make him drink.
>
> -Chuck Harris
>
> cheater00 cheater00 wrote:
>> What can account for this difference between your and my experience
>> and what Chuck said?
>> 
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-- 

John Devereux
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