Super-tiny ferrite rods anywhere?

[Joerg]

Hello,

Looking for a way to either buy very tiny ferrite rods or have them made
somewhere. Like this:

http://www.fair-rite.com/cgibin/cat...ircuit&THEPART=Antenna/RFID+Rods#select:freq1

Except that we need to get the diameter down 0.004" (0.1mm). Length
0.120" to 0.160" (3-4mm) but that's easy to cut. We need to make coils
with these ferrites that will be used in the >10MHz range, so 43, 61 or
67 material would be ok.

Do you guys know any sources or shops that can machine ferrite to such a
small size?

 

[[email protected]]

Hello,

Looking for a way to either buy very tiny ferrite rods or have them made
somewhere. Like this:

http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Inductive+Compone....

Except that we need to get the diameter down 0.004" (0.1mm). Length
0.120" to 0.160" (3-4mm) but that's easy to cut. We need to make coils
with these ferrites that will be used in the >10MHz range, so 43, 61 or
67 material would be ok.

Do you guys know any sources or shops that can machine ferrite to such a
small size?

damn how are you going to wind them? can't use standard smd?

doubt you can machine something that small and brittle I think they
would have
to be cast like that

-Lasse

 

[[email protected]]

Metglas! Or maybe steel or permalloy wire? Plated ceramic?

extruded and fired/baked like how they make pencil lead


-Lasse

 

[Tim Williams]

Just checking... you sure that's not a typo?

That's like... superconductor wire: a brittle ceramic, very fine, but made
out of ferrimagnetic material rather than type II superconductor in this
case.

Best thing I can suggest is, hope you're doing something in the billions
units/year range and can get them made monolithically like ferrite beads.
Or even thick film if it's really truely that tiny. Heck, if it's in the
billions, maybe you can get a whole coil-on-chip monolithic process
developed that puts ferrite and copper on top of silicon. Analog Devices
would love that, I bet -- they already have their line of monolithic
transformers, but those are air cored...

As I'm sure you already know, powdered iron is more common for inductors
(as opposed to RFCs and transformers) at those frequencies. #61 and #67
are kind of on-par I'd say, of course you get more inductivity out of the
ferrites.

Not sure how you might make a microscopic powdered iron choke anyway; I
wonder if carbonyl iron can be deposited in a useful form directly?

Tim

 

[Martin Riddle]

Hello,

Looking for a way to either buy very tiny ferrite rods or have them
made
somewhere. Like this:

http://www.fair-rite.com/cgibin/cat...ircuit&THEPART=Antenna/RFID+Rods#select:freq1

Except that we need to get the diameter down 0.004" (0.1mm). Length
0.120" to 0.160" (3-4mm) but that's easy to cut. We need to make coils
with these ferrites that will be used in the >10MHz range, so 43, 61
or
67 material would be ok.

Do you guys know any sources or shops that can machine ferrite to such
a
small size?

Sounds microwaveish. Have you looked into the guys that do the micowave
coils?

Cheers

 

[tm]

Sounds microwaveish. Have you looked into the guys that do the micowave
coils?

Cheers

Maybe you can wind the coil and dip it is a Fe loaded epoxy.

 

[Spehro Pefhany]

I think you may want to look for "CoorsTek" or something like that (I
never heard it spelled -- just spoken). Born of the beer company, but
does all sorts of fancy ceramic stuff. If you need it done and you have
a great big pile of money, they'd like to hear from you.

The last I heard about them it was in a conversation about making a frame
for some optics out of silicon carbide -- and it was a conversation with
a guy who you can never tell if he's talking sensible mechanical
engineering, or if he's strayed off into zap-ray science fiction, so I
couldn't even tell you if what he was trying was sensible (well, other
than the fact that Coors Tek was willing to take money to try it).

I believe these are the same guys who make ceramic nose cones for
missiles and such like-- very capable company.. not sure if they do
ferrites though. AFAIK ferrites require somewhat different processing.



Best regards,
Spehro Pefhany

 

[John S]

Hello,

Looking for a way to either buy very tiny ferrite rods or have them made
somewhere. Like this:

http://www.fair-rite.com/cgibin/cat...ircuit&THEPART=Antenna/RFID+Rods#select:freq1

Except that we need to get the diameter down 0.004" (0.1mm). Length
0.120" to 0.160" (3-4mm) but that's easy to cut. We need to make coils
with these ferrites that will be used in the >10MHz range, so 43, 61 or
67 material would be ok.

Do you guys know any sources or shops that can machine ferrite to such a
small size?

Hi, Joerg -

I seem to vaguely recall some conversation on this group a few years ago
about "atomic" wristwatches and the ferrite rod antenna they used.

Maybe that will lead you somewhere.

Cheers,
John

 

[George Herold]

Hello,

Looking for a way to either buy very tiny ferrite rods or have them made
somewhere. Like this:

http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Inductive+Compone....

Except that we need to get the diameter down 0.004" (0.1mm). Length
0.120" to 0.160" (3-4mm) but that's easy to cut. We need to make coils
with these ferrites that will be used in the >10MHz range, so 43, 61 or
67 material would be ok.

Do you guys know any sources or shops that can machine ferrite to such a
small size?

Ouch, that sounds really hard. (I know that might just spur you
on.)
Have you contacted Fair-rite (or others)?
Is there some other way to 'skin that cat'?
JL suggested an iron or nickel (alloy) wire would that work?
It'd be easy to try.

George H.

 

[Joerg]

Well, not exactly, but we had Coors (yes, the water-ey-beer company)
make us a batch of tiny (40 mil dia, 0.5" long) ceramic rods as coil
forms, for one of our magnetic field mapper systems.

https://dl.dropbox.com/u/53724080/Gear/Mappers/IMG_2633.JPG

https://dl.dropbox.com/u/53724080/Gear/Mappers/IMG_2680.JPG

Did they send a six-pack along?

But 4 mils sounds (how can I express this politely?) wildly
ludicrously totally insane. Wouldn't they break if you tried to wind
wire on them?

You'd need other tricks, for example winding on a mandrel, torque coil
open (in the direction where diameter increases), scoot over to the
ferrite, gently release torque.

This is almost MEMS stuff and I may need to talk to MEMS folks about this.

The Piconics inductors are something crazy like 40 gage wire, filled
with ferrous-loaded epoxy. No self-resonance to 40 GHz.

http://www.piconics.com/conical-inductors/

Thanks, John, I'll talk to them. Iron-powder and ferrite-loaded epoxy
are also an option. But it would need to be super-runny for this.

 

[Joerg]

damn how are you going to wind them? can't use standard smd?

SMT won't work here. Unless there was stuff a lot smaller than 01005.

doubt you can machine something that small and brittle I think they
would have
to be cast like that

You probably can machine it. For example, leave the sides thick, machine
down only a few millimeters in the center, break thick ends off. Of
course this requires super-balanced machinery and nobody is allowed to
sneeze with 10ft.

 

[Joerg]

And just as fragile.

Food for thought... how do they make hearing-aid telecoils?

T-coils are much larger.

 

[Joerg]

Sounds microwaveish. Have you looked into the guys that do the micowave
coils?

In our case it's all meggeehoitzish

Do you have any company names that come to mind besides Piconics?

 

[Joerg]

Nope. Make your own. Grind up some of your favorite ferrite shapes
with a grinder or buy powder from some ferrite vendor. Find some
tubing that's tiny enough. Pack the tubing with the powder, seal, and
you're done. Just think of it as a ferrite bead with the hole and
wire on the outside instead of down the middle.

That's what I wanted to avoid if possible. Dissolved ferrite never
reaches the performance of sintered ferrite. But if push comes to shove
we may have to do it. I am a bit used to this process because in
ultrasound we have to make acoustic backing material starting with a
magic potion.

If the increased diameter of the tubing is a problem, just mold your
own from powder. Almost any thin glue should hold it together.
<http://www.ferroxcube.com/appl/info/gluing.pdf>
Don't forget the mold release (grease). You're on your own for
handling the very fragile result.

Thanks, Jeff, I have stored this document on my server. Just in case
they ever pull it.

 

[Joerg]

Hi, Joerg -

I seem to vaguely recall some conversation on this group a few years ago
about "atomic" wristwatches and the ferrite rod antenna they used.

Maybe that will lead you somewhere.

Their ferrite antennas are huge monsters compared to ours

 

[Joerg]

Ouch, that sounds really hard. (I know that might just spur you
on.)

It sure does

Have you contacted Fair-rite (or others)?

Not yet. My experience with large companies is that they wave off the
minute you want baked potatoes instead of fries with that.

Is there some other way to 'skin that cat'?
JL suggested an iron or nickel (alloy) wire would that work?
It'd be easy to try.

Yeah, we can use other materials but they all come with a penalty.
Generally in the form or less or much less inductance for the max number
of turns we can get on there. We need all the inductance we can get.

 

[[email protected]]

It sure does










Not yet. My experience with large companies is that they wave off the

minute you want baked potatoes instead of fries with that.











Yeah, we can use other materials but they all come with a penalty.

Generally in the form or less or much less inductance for the max number

of turns we can get on there. We need all the inductance we can get.



--

Regards, Joerg



http://www.analogconsultants.com/

How much inductance?? And what frequency range? ">10Mhz" isn't a range; it's a lower limit.

 

[Joerg]

How much inductance?? And what frequency range? ">10Mhz" isn't a range; it's a lower limit.

The goal is to get above 5uH. Frequency will be determined by how much
inductance we get because the capacitance will be fixed (most likely
around 5pF). That's why I wrote >10MHz, because it is unlikely we can
get below that. Worst case we'll end up at up to 80MHz. Of course, for
obvious reasons we want to really avoid the FM band and also the
aircraft band above that. So 80MHz is a hard limit for this case. Lower
= better.

 

[Gerhard Hoffmann]

Am 21.12.2012 18:05, schrieb Joerg:

Do you have any company names that come to mind besides Piconics?

Piconics prices are breathtaking.

Mini Circuits comes to mind.

When I was with Infineon Fiber Optics, I said to a MCL sales man
that they could sell a bias tee for every ERA-8 or so if the
price was right. Seems they listen.
Ok, at least the price is better.

BTW a colleague of mine decided not to wait until the Piconics
samples were here, put ferrite into a mortar, added
epoxy glue and formed some ferrite cores. They were ugly,
but his conical coils where surprisingly good.

regards, Gerhard

 

[Gerhard Hoffmann]

Am 21.12.2012 18:15, schrieb Joerg:
HAve you contacted Fair-rite (or others)?

Not yet. My experience with large companies is that they wave off the
minute you want baked potatoes instead of fries with that.

You might try Würth, also. They have been quite flexible for
a friend, even for small runs.

Gerhard