TO can package parasitics

Phil Hobbs

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Nov 29, 2021, 12:59:00 PM11/29/21

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Hi, all,

I need to build a fast front end for a fairly huge photodiode--2 mm
square, 12 pF, TO-8 can package.

The TO-8 has a pin spacing of 0.2 inch, so based on the usual
20-nH-per-inch rule of thumb, I expect its package inductance to come in
at 5 nH or thereabouts.

I looked around on the Web for some table of parasitics for varioius
packages, but didn't find anything that included old-timey packages such
as metal cans.

Does anybody have such a reference handy?

Thanks

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Robertson

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Nov 29, 2021, 2:05:17 PM11/29/21

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On 2021/11/29 9:58 a.m., Phil Hobbs wrote:
> Hi, all,
>
> I need to build a fast front end for a fairly huge photodiode--2 mm
> square, 12 pF, TO-8 can package.
>
> The TO-8 has a pin spacing of 0.2 inch, so based on the usual
> 20-nH-per-inch rule of thumb, I expect its package inductance to come in
> at 5 nH or thereabouts.
>
> I looked around on the Web for some table of parasitics for varioius
> packages, but didn't find anything that included old-timey packages such
> as metal cans.
>
> Does anybody have such a reference handy?
>
> Thanks
>
> Phil Hobbs
>

Have you checked bitsavers.org or archive.org? Al Kossow has sent
archive.org a lot of his scanned parts catalogues and reference manuals.
Easier to find on bitsavers though...

John :-#)#

John Larkin

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Nov 29, 2021, 5:45:11 PM11/29/21

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On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>Hi, all,
>
>I need to build a fast front end for a fairly huge photodiode--2 mm
>square, 12 pF, TO-8 can package.
>
>The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>20-nH-per-inch rule of thumb, I expect its package inductance to come in
>at 5 nH or thereabouts.
>
>I looked around on the Web for some table of parasitics for varioius
>packages, but didn't find anything that included old-timey packages such
>as metal cans.
>
>Does anybody have such a reference handy?
>
>Thanks
>
>Phil Hobbs

Can you TDR one?

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

legg

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Nov 29, 2021, 7:00:47 PM11/29/21

to

On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>Hi, all,
>
>I need to build a fast front end for a fairly huge photodiode--2 mm
>square, 12 pF, TO-8 can package.
>
>The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>20-nH-per-inch rule of thumb, I expect its package inductance to come in
>at 5 nH or thereabouts.
>
>I looked around on the Web for some table of parasitics for varioius
>packages, but didn't find anything that included old-timey packages such
>as metal cans.
>
>Does anybody have such a reference handy?
>
>Thanks
>
>Phil Hobbs

You sure you mean TO-8 ?

TO-8 is a package that was used almost exclusively
for power germanium parts.

RL

Phil Hobbs

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Nov 29, 2021, 8:06:37 PM11/29/21

to

Yup.

And a whole lot of larger-size optical detectors that aren't passivated
well enough for non-hermetic packages.

Cheers

legg

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Nov 29, 2021, 8:07:22 PM11/29/21

to

On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>Hi, all,
>
>I need to build a fast front end for a fairly huge photodiode--2 mm
>square, 12 pF, TO-8 can package.
>
>The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>20-nH-per-inch rule of thumb, I expect its package inductance to come in
>at 5 nH or thereabouts.
>
>I looked around on the Web for some table of parasitics for varioius
>packages, but didn't find anything that included old-timey packages such
>as metal cans.
>
>Does anybody have such a reference handy?
>
>Thanks
>
>Phil Hobbs

You might compare it to some laser diode packages for Mech/Elec
strays.

https://picolas.de/wp-content/uploads/2020/08/Application-Note-02_Impedance-of-Diodes_Bt03_tk01_sl02_am_HL_jhs2_asz.pdf

RL

Phil Hobbs

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Nov 29, 2021, 8:11:37 PM11/29/21

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John Larkin wrote:
> On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
>> Hi, all,
>>
>> I need to build a fast front end for a fairly huge photodiode--2 mm
>> square, 12 pF, TO-8 can package.
>>
>> The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>> 20-nH-per-inch rule of thumb, I expect its package inductance to come in
>> at 5 nH or thereabouts.
>>
>> I looked around on the Web for some table of parasitics for varioius
>> packages, but didn't find anything that included old-timey packages such
>> as metal cans.
>>
>> Does anybody have such a reference handy?
>>
>> Thanks
>>
>> Phil Hobbs
>
> Can you TDR one?
>

I could if I had one handy, but ATM I'm dealing with a requirement to
make a front end with ~ 350 MHz BW from a TO-8.

12 pF and 5 nH resonate at 650 MHz, so you see the issue.

I'm trying to decide whether to have a go at it or insist on the goal
posts being moved.

Cheers

John Larkin

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Nov 29, 2021, 8:41:47 PM11/29/21

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On Mon, 29 Nov 2021 20:06:25 -0500, Phil Hobbs

<pcdhSpamM...@electrooptical.net> wrote:

>legg wrote:
>> On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>>> Hi, all,
>>>
>>> I need to build a fast front end for a fairly huge photodiode--2 mm
>>> square, 12 pF, TO-8 can package.
>>>
>>> The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>>> 20-nH-per-inch rule of thumb, I expect its package inductance to come in
>>> at 5 nH or thereabouts.
>>>
>>> I looked around on the Web for some table of parasitics for varioius
>>> packages, but didn't find anything that included old-timey packages such
>>> as metal cans.
>>>
>>> Does anybody have such a reference handy?
>>>
>>> Thanks
>>>
>>> Phil Hobbs
>>
>> You sure you mean TO-8 ?
>>
>> TO-8 is a package that was used almost exclusively
>> for power germanium parts.
>>
>> RL
>>
>
>Yup.
>
>And a whole lot of larger-size optical detectors that aren't passivated
>well enough for non-hermetic packages.

https://www.dropbox.com/s/wm3a3cpxa8tcarg/S8551_1.JPG?raw=1

I could TDR that one, but it's a TO5.

Phil Hobbs

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Nov 30, 2021, 1:07:15 PM11/30/21

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Thanks, Rob.

Cheers

Phil

legg

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Nov 30, 2021, 2:34:24 PM11/30/21

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On Tue, 30 Nov 2021 13:07:03 -0500, Phil Hobbs

<pcdhSpamM...@electrooptical.net> wrote:

>legg wrote:
>> On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>>> Hi, all,
>>>
>>> I need to build a fast front end for a fairly huge photodiode--2 mm
>>> square, 12 pF, TO-8 can package.
>>>
>>> The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>>> 20-nH-per-inch rule of thumb, I expect its package inductance to come in
>>> at 5 nH or thereabouts.
>>>
>>> I looked around on the Web for some table of parasitics for varioius
>>> packages, but didn't find anything that included old-timey packages such
>>> as metal cans.
>>>
>>> Does anybody have such a reference handy?
>>>
>>> Thanks
>>>
>>> Phil Hobbs
>>
>> You might compare it to some laser diode packages for Mech/Elec
>> strays.
>>
>> https://picolas.de/wp-content/uploads/2020/08/Application-Note-02_Impedance-of-Diodes_Bt03_tk01_sl02_am_HL_jhs2_asz.pdf
>>
>> RL
>>
>Thanks, Rob.
>
>Cheers
>
>Phil

Any idea why gold-plated kovar would reduce inductance by factor of
3:1 ?

RL

John Walliker

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Nov 30, 2021, 2:48:14 PM11/30/21

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Maybe they got the decimal point in the wrong place. Otherwise it doesn't make sense.
John

Phil Hobbs

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Nov 30, 2021, 3:44:48 PM11/30/21

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Probably just closer to the baseplate--reduces loop area. Or it could
be wrong. ;)

Cheers

Phil Hobbs

Chris Jones

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Nov 30, 2021, 10:14:39 PM11/30/21

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I think kovar is magnetic, perhaps that would make a difference, at
least at some frequencies.

jla...@highlandsniptechnology.com

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Nov 30, 2021, 11:28:09 PM11/30/21

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I've seen butterfly package lasers with a long wirebond from the pin
to the laser chip, and some with a ceramic transmission line ramp
sloping down to the chip.

https://www.dropbox.com/s/4g9ac2x7nz20pos/Butterfly_ebay_Dyno1.jpg?raw=1

--

Father Brown's figure remained quite dark and still;
but in that instant he had lost his head. His head was
always most valuable when he had lost it.

legg

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Dec 1, 2021, 8:13:27 AM12/1/21

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On Tue, 30 Nov 2021 20:28:01 -0800, jla...@highlandsniptechnology.com

wrote:

>On Mon, 29 Nov 2021 20:04:11 -0500, legg <le...@nospam.magma.ca> wrote:
>
>>On Mon, 29 Nov 2021 12:58:42 -0500, Phil Hobbs
>><pcdhSpamM...@electrooptical.net> wrote:
>>
>>>Hi, all,
>>>
>>>I need to build a fast front end for a fairly huge photodiode--2 mm
>>>square, 12 pF, TO-8 can package.
>>>
>>>The TO-8 has a pin spacing of 0.2 inch, so based on the usual
>>>20-nH-per-inch rule of thumb, I expect its package inductance to come in
>>>at 5 nH or thereabouts.
>>>
>>>I looked around on the Web for some table of parasitics for varioius
>>>packages, but didn't find anything that included old-timey packages such
>>>as metal cans.
>>>
>>>Does anybody have such a reference handy?
>>>
>>>Thanks
>>>
>>>Phil Hobbs
>>
>>You might compare it to some laser diode packages for Mech/Elec
>>strays.
>>
>>https://picolas.de/wp-content/uploads/2020/08/Application-Note-02_Impedance-of-Diodes_Bt03_tk01_sl02_am_HL_jhs2_asz.pdf
>>
>>RL
>
>I've seen butterfly package lasers with a long wirebond from the pin
>to the laser chip, and some with a ceramic transmission line ramp
>sloping down to the chip.
>
>https://www.dropbox.com/s/4g9ac2x7nz20pos/Butterfly_ebay_Dyno1.jpg?raw=1

TL or just and SMD link?

https://www.knowlescapacitors.com/Products/Thin-Film-and-Substrates/Mounting-Shorts

Doesn't help if the canned part is prescribed.

RL

legg

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Dec 1, 2021, 8:14:47 AM12/1/21

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. . . any increase in permeability in the neighborhood could be
expected to make things worse, not better.

RL

Phil Hobbs

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Dec 1, 2021, 1:45:57 PM12/1/21

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Depends on the frequency. Up at UHF the skin depth in the kovar will be
zilch, and the permeability will be pretty small anyway--it goes to 1.0
around 500 MHz for most iron/nickel alloys AFAICT.

A quick search didn't turn up anything more recent than this:

<https://www.nature.com/articles/162528a0.pdf> (open access).

Cheers

Phil Hobbs