Out-of-tolerance zero ohm resistors

In Harwaii? :-)

DigiKey has them. They're called SMD 'shunts' or 'jumpers,'

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Here's one:

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Cheers, James Arthur

Reply to
dagmargoodboat
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Looks like you've caught 'em. Further, it looks like the best Siemens are solid copper--beware the copperplate!

Cheers, James Arthur

Reply to
dagmargoodboat

Resistance is fuse-ile.

(Better ablate than never?)

Cheers, James Arthur

Reply to
dagmargoodboat

I did not manually calculate. I used PCB Toolkit V6.8 available from .

Reply to
John S

May i have 20% tolerance rating?

Reply to
Robert Baer

My ancient "Reference Data for Radio Engineers" has a nomograph (!) that suggests more like 20C rise (100 mil wide trace, 2 oz, 10 amps). That was probably for an oldie 0.062 double-sided board. A multilayer, with internal planes, will cool traces a lot better. In most cases, the voltage drop is a bigger concern than trace heating.

--
John Larkin         Highland Technology, Inc 
picosecond timing   laser drivers and controllers 
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Reply to
John Larkin

I'd believe that for a long trace on a single or double-layer board.

The immediate situation is just a .12" length along a much fatter trace though, plus aggressive solid pours in four internal layers, ground on the bottom, then a massive heat sink not far away.

Which brings up a good point--instead of 0.10" (1210), we'd fill the gap with something wider, closer to 0.20".

Cheers, James

Reply to
dagmargoodboat

On Sun, 31 May 2015 04:59:49 -0700 (PDT), Phil Hobbs Gave us:

*film* of least resistance?
Reply to
DecadentLinuxUserNumeroUno

On Sun, 31 May 2015 09:53:25 -0700, John Larkin Gave us:

Also use 4oz.

Most "modern" "digital" PCBs are gold. Probably neither 2oz or 4oz numbers are accurate.

PS boards likely are still old style HASL copper with a tight mask.

Remember the "rivulet days".?

Reply to
DecadentLinuxUserNumeroUno

On Sun, 31 May 2015 10:06:49 -0700 (PDT), snipped-for-privacy@yahoo.com Gave us:

Also placing additional PTHs nearby such elements soaks/conducts heat better too.

Reply to
DecadentLinuxUserNumeroUno

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Reply to
Lasse Langwadt Christensen

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Yes, but if you stacked a million of them you've have a stack of gold nearl y one meter thick!

Cheers! James

Reply to
dagmargoodboat

I think they'd be more like a mile thick. ;-)

Reply to
krw

Anything that thick will really limit you on the components used.

Not true. Gold flashing is fairly rare. Its only purpose would be storage. Don't do that.

"Rivulet"? I've heard of wave soldering but liquid PCBs? Perhaps you mean "rivets"?

Reply to
krw

We only do gold-over-nickel these days. ENIG.

If it really matters, our fab note will say

START WITH 2 OZ COPPER

so they don't short-cut the plating. And if it really matters, I'll include a test trace that I can ohm out. And TDR.

Most boards' copper seem to come out a little on the thin side these days. We seldom get actual 1 Oz.

--
John Larkin         Highland Technology, Inc 
picosecond timing   laser drivers and controllers 
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Reply to
John Larkin

Gold over nickel is super planar, which is great for BGAs. And it's the best surface for lead-free solder. Solder practically leaps onto gold plate. That's all we buy now.

I prototype on gold-plated FR4, too. It doesn't tarnish like copper.

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--
John Larkin         Highland Technology, Inc 
picosecond timing   laser drivers and controllers 
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Reply to
John Larkin

for 0.062" boards said stack would be nearly a mile high,

--
umop apisdn
Reply to
Jasen Betts

A 1210 (3.2x2.5mm) patch of 0,2mm FR-4 (one six-layer board ply) has a thermal resistance of ~120C/W to the copper pour underneath.

So, 36mW (or 20mW) wouldn't be any sort of big deal all by itself.

A stalagmite / stalactite array might make a useful heat exchanger somewhere. But I found it easier to nail top and bottom together, then heatsink the bottom.

Cheers, James Arthur

Reply to
dagmargoodboat

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Yes, 0.979 miles, but you'd own a goldmine!

Cheers, James Arthur

Reply to
dagmargoodboat

Hmm, If you make an active negative resistance, does it have Johnson noise?

George H.

Reply to
George Herold

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