Prev: Now for something entirely different
Next: RIP Randy Slone
From: Tim Williams on 17 Apr 2010 07:51
"Jasen Betts" <jasen(a)xnet.co.nz> wrote in message
news:hqbqef$f4l$3(a)reversiblemaps.ath.cx...
> however photdiodes packed in black plastic are packaged
> in plastic that is transparent in the infrared, black
> in the visible wavelengths cuts down on interferance
> from fluorescent lights etc...

I tested one of those with a red superbright. Just enough attenuation that
I got a useful signal with the LED positioned directly in front of the
sensor (CTR on the order of 0.01%).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


From: Phil Hobbs on 17 Apr 2010 11:06
On 4/17/2010 4:10 AM, Jasen Betts wrote:
> On 2010-04-16, Jim Thompson<To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote:
>> On Fri, 16 Apr 2010 01:27:15 -0700, Robert Baer
>> <robertbaer(a)localnet.com> wrote:
>
>> Even those diodes (and transistors) packaged in black plastic exhibit
>> photo effects.
>>
>> TI used to have a whole series of IR diodes (for TV remote links) that
>> had no window.
>
> I've seen some like that, a bare silicon wafer.
>
> however photdiodes packed in black plastic are packaged
> in plastic that is transparent in the infrared, black
> in the visible wavelengths cuts down on interferance
> from fluorescent lights etc...
>
>> And, John, they don't "leak when light hits them"... what a dummy :-)
>
>
> --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---

The old plastic transistors that were photosensitive were
phenolic-encapsulated, iirc. Metal can transistors detect light that
gets in through the green frit seals--it usually takes direct sunlight
before that's a problem, but it can be very puzzling!

Novolac epoxy (as used in all modern plastic packages afaik) is very
black at all optical wavelengths where silicon is photosensitive. I'm
not sure what it's like further out in the IR.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
From: Phil Hobbs on 17 Apr 2010 11:12
On 4/17/2010 11:06 AM, Phil Hobbs wrote:
> On 4/17/2010 4:10 AM, Jasen Betts wrote:
>> On 2010-04-16, Jim
>> Thompson<To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote:
>>> On Fri, 16 Apr 2010 01:27:15 -0700, Robert Baer
>>> <robertbaer(a)localnet.com> wrote:
>>
>>> Even those diodes (and transistors) packaged in black plastic exhibit
>>> photo effects.
>>>
>>> TI used to have a whole series of IR diodes (for TV remote links) that
>>> had no window.
>>
>> I've seen some like that, a bare silicon wafer.
>>
>> however photdiodes packed in black plastic are packaged
>> in plastic that is transparent in the infrared, black
>> in the visible wavelengths cuts down on interferance
>> from fluorescent lights etc...
>>
>>> And, John, they don't "leak when light hits them"... what a dummy :-)
>>
>>
>> --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
>
> The old plastic transistors that were photosensitive were
> phenolic-encapsulated, iirc. Metal can transistors detect light that
> gets in through the green frit seals--it usually takes direct sunlight
> before that's a problem, but it can be very puzzling!
>
> Novolac epoxy (as used in all modern plastic packages afaik) is very
> black at all optical wavelengths where silicon is photosensitive. I'm
> not sure what it's like further out in the IR.
>
> Cheers
>
> Phil Hobbs
>

Just to clarify: optical packages are _not_ made of the same
stuff--ordinary plastic packages are made from Sumitomo Bakelite's
Sumikon EME-6710 or its brethren. I looked for a decent datasheet but
there don't appear to be any online--typical of the chemical industry.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
From: Jim Thompson on 17 Apr 2010 11:22
On Sat, 17 Apr 2010 11:06:51 -0400, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

[snip]
>
>The old plastic transistors that were photosensitive were
>phenolic-encapsulated, iirc. Metal can transistors detect light that
>gets in through the green frit seals--it usually takes direct sunlight
>before that's a problem, but it can be very puzzling!
>
>Novolac epoxy (as used in all modern plastic packages afaik) is very
>black at all optical wavelengths where silicon is photosensitive. I'm
>not sure what it's like further out in the IR.
>
>Cheers
>
>Phil Hobbs

Phil, Have you looked at any I/C processes, like XFAB-XH035, which has
a photodiode module? They're using several "coating" layers to tailor
the response curve.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy
From: Phil Hobbs on 17 Apr 2010 12:29
On 4/17/2010 11:22 AM, Jim Thompson wrote:
> On Sat, 17 Apr 2010 11:06:51 -0400, Phil Hobbs
> <pcdhSpamMeSenseless(a)electrooptical.net> wrote:
>
> [snip]
>>
>> The old plastic transistors that were photosensitive were
>> phenolic-encapsulated, iirc. Metal can transistors detect light that
>> gets in through the green frit seals--it usually takes direct sunlight
>> before that's a problem, but it can be very puzzling!
>>
>> Novolac epoxy (as used in all modern plastic packages afaik) is very
>> black at all optical wavelengths where silicon is photosensitive. I'm
>> not sure what it's like further out in the IR.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Phil, Have you looked at any I/C processes, like XFAB-XH035, which has
> a photodiode module? They're using several "coating" layers to tailor
> the response curve.
>
> ...Jim Thompson

I'm currently doing an expert witness gig in a trade secret
misappropriation case that centres in part on similar things, but I
haven't dug into the process details.

The absorption depth of light in silicon is a strong function of
wavelength, so PD response depends a lot on the epi thickness and the
depth of the tub/substrate/whatever is the counterelectrode to the epi.
Besides that, you can use thin metal, silicides, nitride, and other
such stuff, and then there are the actual colour filters, as used in
image sensors.


Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
First  |  Prev  |  Next  |  Last
Pages: 1 2 3
Prev: Now for something entirely different
Next: RIP Randy Slone