Resistors With Steel Leads

[MrAl]

Hello there,

A while back i had purchased some 1/4 watt 1 percent resistors at a discount as i bought one half of the entire purchase going in halves with someone else. I got a lot of resistors for very low price, and lots and lots of values, the half order takes up a whole parts box by itself.

About two weeks ago i noticed that the leads are strongly attracted to a magnet, which means they are steel or other iron content metal, plated with tin i think. The values are close enough to the color coded value as tested with an Ohm meter.

So the question is, does anyone have any information on resistors with steel leads? For example, skin effect in steel will be MUCH higher than in copper because steel is very magnetically active, whereas copper is not. The up side to this though is that the resistors are stronger when mounted, so they can withstand more extreme shock and vibrations. The down side is at higher frequencies there has to be skin effect that could alter the characteristics in a circuit that might change dramatically with higher resistance at higher frequencies. I suppose this could be minimal for certain DC value AC value ratios and short cut lead lengths, but i cant remember that details from long ago.

So any information regarding the things to watch out for using steel lead resistors would help greatly as i have a LOT of these resistors and i would hate to throw them all in the garbage.

 

[ronsimpson]

The leads have copper over the steel and over the copper is solder.
Maybe no copper but definitely solder.
They are OK to use. Don't put them in the garbage.

 

[chemelec]

I Doubt they are Copper Plated, Just Tinned Steel.
Some may be ROHS Compliant.
And considering the Short Lengths of wire, it is unlikely to be any worse at High Frequencies than with copper leads.
But they are Cheaper to manufacture.

 

[dr pepper]

I wonder if the steel will rust and affect a solder joint?

 

[crutschow]

I wonder if the steel will rust and affect a solder joint?

If it's a good solder joint then the solder will prevent the steel from corroding since the solder is bonded to the steel.

 

[dr pepper]

I was thinking if you soldered then snipped off the lead you would be leaving a section of bare steel, do you think the bond between the solder and the steel would be good enough to prevent oxidation from creeping in between the 2?
Kinda makes me think, lead free solder, steel wires, how reliable are pcb's going to be these days.

 

[chemelec]

Rusted Steel is No Different than Oxidized Copper.

 

[Nigel Goodwin]

I was thinking if you soldered then snipped off the lead you would be leaving a section of bare steel, do you think the bond between the solder and the steel would be good enough to prevent oxidation from creeping in between the 2?
Kinda makes me think, lead free solder, steel wires, how reliable are pcb's going to be these days.

Resistors have been like this for a GREAT many years, it's never been a problem.

 

[MrAl]

Hello,

Well these resistors came from a less reputable source, while ALL other resistors i have are copper.

Also, steel rust is definitely much different than oxidized copper because rust does not form a coating like the oxide does. That means that steel never stops rusting even after it has rusted a little, so it is possible to completely rust away an iron wire while the copper would take many many years if it every did oxidize away under normal conditions. However, i doubt enough of the steel would be exposed only the very tiny end i would think after cutting.

What i was really hoping for was some technical data on the differences between having the steel leads vs the copper leads, so it would be a completely objective view. This would be in the form of measurements most likely, or possibly some theoretical data.

 

[kubeek]

Just plug the correct constants here and see for yourself how worse will the skin effect be http://en.wikipedia.org/wiki/Skin_effect#Formula
Edit: or just look at this http://www.compliance-club.com/archive/old_archive/990810a.gif

 

[chemelec]

Since they are Tin or Tin/Lead Plated, What is the SKIN Effect of This?

 

[kubeek]

how thick is the plating, if it is just a few μm then it won´t matter at all. I am not sure how much will the steel core affect a plating of coppper, but I guess even if the copper were thick enough the magnetic effect of the steel would make it just as bad.

But on the other side, how long is the connection between the resistor and the PCB and what is the net result of the skin efffect on the total impedance? If the DC resistance of the two milimeters of connecting wire is a few miliohms, how will a resistance increase of even say a hundred times affect a resistor that is 10 ohms?

 

[BobW]

All of my resistors, capacitors and semiconductors have steel leads. I haven't seen any with copper leads for many many years. The only components with copper leads that I still see available are inductors, for obvious reasons. The reason for steel leads is that they conduct less heat from the soldering process into the internals of the component, and also because the leads are stronger and more suitable for automated assembly equipment.

 

[MrAl]

Hi,

That's funny because every other resistor i have has copper or at least non magnetic leads, and i have purchased a countless number of these things over the years. Back when i worked in the industry we never used steel lead resistors either, but i dont remember what the exact reason for doing that was that's partly why i created this thread.

I suppose i could do some lower frequency testing myself, maybe up to say 20MHz. My scope isnt that great though so it might be hard to do. Yes, the questions come up as i was saying, like what is the ratio of the effect to the DC resistance. That would be nice to know, and also how much it would interact with another adjacent resistor close by on the same board or on a board say in a card cage where the spacing between boards was minimal. Probably only a little effect, but then again now little is hard to nail down because it also depends on the other impedances and the degree of coupling and the actual normal signal level. For example, would they pick up 60Hz hum in an audio amplifier more than copper leaded devices, or pick up more interference in an RF circuit from another RF circuit.

Usually we dont want things in our circuits that we cant explain away exactly enough

 

[Nigel Goodwin]

Al, you really need to stop worrying about nothing all the time

 

[MrAl]

Al, you really need to stop worrying about nothing all the time

Hello Nigel,

It is becoming clear to me that you and i come from different walks of life. You are happy with some things that i am not happy with. In particular, i come from a place where at one time i needed to know where every electron was in a given circuit for example, where most of the time we dont need this information, we just need a basic measurement like for current. If we measure 1.0 amps and it's really 1.01 amps, most of the time we dont care. But sometimes we do, and i like to dig deeper. What is causing that extra 10ma? Sometimes it matters, sometimes it doesnt, but i prefer not to use a blanket policy for everything where i ignore certain details just so it makes it easier.

There two ways of looking at science and the practical. One is to look deeply into the details, so every 1 nano amp out of 10 amps might matter, and the other is to skip over that extra nano amp. Most of the time we dont need to know that, but in science sometimes the details tells a more complete story of what is happening. A notable case is GSP where the frequency reference has to be precise, and the small details of relativity theory have to be taken into account in order to get the required accuracy on position measurements on the earth.

But even for lack of agreement on this or that, we still should have respect for one another. Enough to recognize that if someone brings up a question or an answer and that person has proven in the past to find answers to questions that were pressing at the moment for hundreds or even thousands of other people, that there is most likely something to this or at the very least, the *possibility* that there could be something to this. If it turned out that there was a little something to it, then it would add to all of our knowledge in the field. If it turned out that there was absolutely nothing to it, then nothing's really lost.

What surprises me is that for someone that has proven in the past to find good answers to problems that their opinion should be counted as so seemingly little. That kind of attitude can be counter productive in that the one that ignores the reasoning may look like the one that isnt quite paying enough attention

You may want to note the other responses too, as some of them were quite intelligent as you can plainly see. So some people must have had the same thoughts, and as i look around on the web i see a similar situation...where some people were questioning the possibility that one type of metal might cause a problem were another type might not.
It might also interest you to know that i have purchased wire from a no so reputable source, and that wire was very high in resistance and even would not solder properly. So you see what can happen. It was mentioned that it could be copper plated wire, because it looked copper but it could not have been very good quality copper. That was the first time that i remember getting something i could call 'bad' wire.

You might also remember the RTC battery issue in the past. Many people seem to agree that an Li-ion battery should not be charged above the recommended voltage for at the very least reason that it would ruin the battery. Many sites also note that it is dangerous to charge above the recommended max voltage.
So my choices are:
1. Go ahead and charge above the max voltage anyway despite all the warnings on the web, or
2. Make darn sure that the voltage doesnt go above 4.2 volts.
Since #2 surely is not that hard anyway, i chose not to take a chance on stressing the part and i believe that is the most reasonable, as do others who know a lot about these kinds of batteries.

 

[JimB]

MrAl, you raise some interesting points.

I have previously noticed magnetic connecting leads, usually on semiconductor devices such as transistors and three terminal regulators.

I had a look at a random sample of my stock of resistors and I did not find any magnetic leads.
However all the resistors which I tested had something magnetic within the body of the resistor. I assume that this is the end caps which connect onto the ceramic former of the resistor where the carbon or ceramic film is deposited.

I have no idea of the effect of the magnetic leads in the impedance of the resistor, if this is something you wish to study further, don't forget that the resistor is "adjusted" during manufacture by laser etching a spiral in the carbon/copper film. This in itself will have a small amount of inductance.

A quick examination of other components showed that some electrolytic capacitors had magnetic leads, as had some quartz crystals.

JimB

 

[Nigel Goodwin]

Hello Nigel,

It is becoming clear to me that you and i come from different walks of life. You are happy with some things that i am not happy with. In particular, i come from a place where at one time i needed to know where every electron was in a given circuit for example, where most of the time we dont need this information, we just need a basic measurement like for current. If we measure 1.0 amps and it's really 1.01 amps, most of the time we dont care. But sometimes we do, and i like to dig deeper. What is causing that extra 10ma? Sometimes it matters, sometimes it doesnt, but i prefer not to use a blanket policy for everything where i ignore certain details just so it makes it easier.

But the result of that is you will NEVER get anything done, steel wires in components have been commonplace for decades, and it's crazy imagining magnetic and skin effects etc. As for your 1.01A suggestion, that's just as crazy - it's within 1%, which is likely to be considerably better than the tolerances of any components involved.

Look at an old CRT TV PCB that's been out in the rain or water damaged in some way, it's VERY common for the component leads to be rusted, because they are steel and not copper - it makes no difference.

 

[jpanhalt]

Magnetic (steel) leads on electrolytic capacitors have been known for a very long time. 4QD motor drives commented on that fact 15 years ago. In its applications, screw-mounted caps were preferred for the high currents they carried.

I just checked some recent purchases. An inexpensive set of 1% metal film resistors had magnetic leads, and the bodies were also magnetic. DigiKey-sourced 1%-resistors had magnetic bodies, but not the leads. Maybe nickle film is involved in the magnetic bodies? Trimming capacitors (ceramic, <200 pF) sourced from a local surplus place more than 10 years ago are not magnetic. Ones sourced from DigiKey recently are magnetic.

John

 

[tvtech]

But the result of that is you will NEVER get anything done, steel wires in components have been commonplace for decades, and it's crazy imagining magnetic and skin effects etc. As for your 1.01A suggestion, that's just as crazy - it's within 1%, which is likely to be considerably better than the tolerances of any components involved.

Look at an old CRT TV PCB that's been out in the rain or water damaged in some way, it's VERY common for the component leads to be rusted, because they are steel and not copper - it makes no difference.

We throw stacks of CRT TV's away because of water damage....pot plants on top of them...all caused by the customer watering the pot plant with too much water and that runs into the tv etc,etc.

Even when the set is off....the damage is done. Component leads rust themselves to pieces eventually. And repair then is not worth the time or trouble.

tv