1G ohm resistor

Digikey is your friend.

Bob

See:

The related " Newark InOne" does not seem to carry them.

....... Phil

I got a couple of 91M (IIRC) from Vishay as samples a few years back; it's worth a try if you only want a few. The worst that can happen is they say no.

Barry Lennox

On Mon, 17 Jul 2006 17:42:21 +1200, Barry Lennox Gave us:

It takes over ten of those in series to even approach 1GigOhm.

I don't know if this is still true, but you used to be able to get Newark stuff via Farnell, and Farnell stuff via Newark - delivery times were a couple of days, because the parts came from stocks held on the wrong side of the Atlantic, but here wasn't any problen about ordering small number of parts.

In general, yes, but are they in this case? I looked, and found high-value resistors, but none in surface mount.

Cheers, James Arthur

When I looked in May, Bill & Phil's present suggestion of Farnell looked best. Here's a cut-n-paste of my notes regarding manufacturers & suppliers I found:

Farnell stocks a number of high-value resistors. Farnell #9236473, 235052110476 by PHYCOMP (47M 5% 0805) is =A30.099.

RH73H2A50MKTN is 0805, 50M, for =A30.58, mfr =3D MEGGITT

Notes: Meggitt owns Piher, Ohmite owns Victoreen.

Stackpole Electronics:

HTH, James Arthur

Thank You everyone, I have requested ohmcraft and Stackpole people to send me a quote for resistors - 10Qty. Also asked Vishay if they can give me samples. Let me see if i can get them. Also Farnell has given me the quote. In the end of the day, i'll see which one is the best offer and buy. Thanks the replies helped a lot.

snipped-for-privacy@yahoo.com wrote:

Hmm, I see some of the links I supplied have already gone stale. Updated above.

James

Maybe because a surface mount resistor will be degraded to much by leakage of the board/ dirt film/moisture,in other words those resistors might have to be bigger,to be mounted with standoffs, and not touch anything in their neighborhood, protected by guard rings etc. Your surface mount resistor might surprise you unfavorably.

Those things can happen, but they don't explain DigiKey's lack of the parts. Several vendors offer surface mount resistors, with values up to 2T (2x10^12) ohms.

Of course, it has to be clean.

James

If your quantities are low, you can buy the through hole part and form the leads to surface mount it. This could save you if you have a mechanical reason to not use through hole.

I think Newark stocks IRC's 330M and 250M resistors. You could string a few in series.

What kind of surface are you going to mount a 1G resistor to without trashing its impedance?

On 17 Jul 2006 08:14:45 -0700, snipped-for-privacy@yahoo.com Gave us:

Typically SMD stops at one or max 2 MegOhms. A 1GigOhm SMD is actually hard to make reliably (read repeatably). The most common type is called a "flatso" package, and they come bare or epoxy coated. The leads can be formed such that surface mounting is possible (though slightly elevated).

Another thing about resistors that high in value. One MUST never touch them without gloves on, and one MUST get the area under the mount location VERY clean. Leakage is tantamount to not having the resistor value one thought one had. Even breathing coffee breath on them changes their value. The bare models are hygroscopic as is the epoxy to a slight degree (enough at these values). I would also recommend encapsulation after assembly as the environment will also change the value in fairly short order. A single fingerprint can lower the value several percentage points. At least enough to throw the tolerance out the window, and make the device function in an entirely unpredictable manner.

On 17 Jul 2006 08:20:00 -0700, snipped-for-privacy@yahoo.com Gave us:

If the application is a divider for HV, I would seriously recommend against using small SMD packages if you want reliably circuit operation. If the SMD must be used, the full encapsulation or conformal coating at the very least, would be a requisite procedure.

I have seen what appears to be a 100% clean installation fail. Hot solvent bath, and a good 0.5 hr bake at 60C made the problem go away. In a humid environ, however, it rears its ugly head again quite rapidly. Within a couple days easily, and I am in a dry climate.

The first thing we always did with a failure mode was ensure that the assembly is VERY clean, and well baked dry.

Also, if it is HV, I would recommend that no mask be applied in the HV component section(s), as it tends to delaminate from encapsulants, which is a bad thing. At that point, it is as if there is no encapsulant at all.

On Mon, 17 Jul 2006 21:54:19 +0200, Sjouke Burry Gave us:

See my post regarding this, and why I declared "flatso" packages and encapsulation to be the current "best practice".

Oh, and one cannot touch these devices either. They will suck it up, and NOT be of the same value any longer, and will be very unpredictable in behavior.

One with a slot milled between the pads?

On 17 Jul 2006 13:17:32 -0700, snipped-for-privacy@yahoo.com Gave us:

That's nuts. Cite?

On 17 Jul 2006 13:17:32 -0700, snipped-for-privacy@yahoo.com Gave us:

It has to be BEYOND clean. It has to be clean AND dry. Just for starters. It only takes a few picofarads of associated capacitance to cause problems as well.