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Should I plate electrical terminals ?...

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noel
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Username: noel

Post Number: 78
Registered: 06-2005

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Posted on Tuesday, 31 August, 2010 - 01:07 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi All,
I have an automotive application where a 12 vdc solenoid is used. The connector pins on the solenoid are brass (not plated) and the current draw / rating is anything between 60mA and 3.0 Amps. Apart from corrosion issues, are there any reasons why I should plate the connector pins ? Does tin plating offer any real advantages with this current rating ?

Any advice would be appreciated.
Thanks
Noel}
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chippie
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Post Number: 290
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Posted on Tuesday, 31 August, 2010 - 02:56 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Playing devil's advocate....
If you were to plate them how would you arrive at a uniform thickness and how thick would the plating need to be to be effective?

IMHO, tin plating the terminals isnt going to do anything to improve on them at the current levels you are drawing...
eccentric millionaire financed by 'er indoors
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microguy
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Post Number: 188
Registered: 01-2010

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Posted on Tuesday, 31 August, 2010 - 03:22 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ditto. A gold contact will give you less resistance. And that would make a difference at higher current levels. Depending on where this is located, I might do it just for the corrosion resistance.
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noel
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Post Number: 79
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Posted on Tuesday, 31 August, 2010 - 03:34 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thanks for your replys.
microguy: corrosion resistance is not an issue for me. What kind of difference would you expect at higher current levels. I was under the impression that plating improved reliability at low current levels (uAmp level) and for low voltage (less than 5VDC) levels more-so than higher current levels ?

Noel
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microguy
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Post Number: 190
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Posted on Tuesday, 31 August, 2010 - 04:03 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

It will help at all levels, but the way *I* understand it, you need the extra "oomph" of low resistance at higher current levels, because of the IR drop. And if you have a higher IR drop, you can't afford to lose much at 12V. (silver works good here too, less expensive, but I think the gold plating kits are more readily available).

At low current levels, you just don't generate that much of an IR drop. So as long as you have a good mechanical connection, I don't think the gold is buying you anything really.

In some cases, like audio, you may want gold connectors. This way, you know what sorts of metals the contacts are "made" of (what's mating to what).

Because when you place two different metals in contact with each other, they act like tiny batteries. Bad for low level audio, if you want the highest quality. There's also the corrosion thing, even in a clean environment. The tiny batteries will corrode the metals.

(I saw that first hand on my folks car. brand new Cadillac, two years later, the moulding on the side had big old rust spots right where it was mounted to the body of the car. The two different metals caused it. Nope, Cadillac never did fix it. One reason I buy Honda now)

If you gold plate them, then you know what sorts of metals are contacting each other.

The can also act like little PN junctions too. Yep, act like tiny diodes. Which is also not good. (that's what a bad solder joint can look like too!)

Having said that, I don't buy into the idea that ALL your audio connections need to be gold plated. For one, you probably can't hear the difference, two most are not that low level, and three, it's a sales gimmick.

So in some cases, yes, you will get more reliability, but I don't think so in your case.

How much difference? Can't tell. That would depend on several factors, that being what you had to start with.

Most of the "bus bar" that is used in industrial type set ups have silver plating (or a similar alloy) to reduce resistance. The difference between just plain copper (which oxidizes pretty fast) and plated copper was very significant.

And at those current levels, a high IR drop, can be enough to cause a fire if you're not careful.

If you have clean brass, you should have no problems and no need for gold. But brass oxidizes pretty well too. But if corrosion is not an issue, I wouldn't worry about it, because the brass won't oxidize where it's mated on the contact (it needs to be exposed).

That's why I said I would only do it if corrosion were an issue. That's the only reason I see to do it. But since you say that's not an issue, no problems.
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gajjer
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Post Number: 332
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Posted on Tuesday, 31 August, 2010 - 05:49 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi noel
I'm a bit confused by the first post. Do you really mean a solenoid or are you talking about a relay?
Also, why does the current in the solenoid range from 60mA to 3A?
If you are talking about fixed connections that do not move, I would have though that the soldering would dominate any other resistance.
On relay contacts operated at low current there is a possibility of oxidation and gold plating is prefered.
If you are switching an inductive load I would consider what you are doing about supression. You will get high voltages on turn off and could do serious damage.
cheers
gaj
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noel
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Post Number: 80
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Posted on Wednesday, 01 September, 2010 - 10:26 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Gajjer: Thanks for your reply.
It a solenoid alright. The solenoid is current controlled i.e. using current to vary the force developed by the solenoid - hence the variation in the current levels.
It is a fixed connection - the only movement caused by engine vibration.
Switching / supression / voltage spikes, ect, are controlled by other electronic components.

Thanks again - Noel.
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gajjer
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Post Number: 334
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Posted on Wednesday, 01 September, 2010 - 05:20 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi noel
Ok I have come across this kind of actuator.
The other question I should have asked is whether you are soldering to the connections or is it some sort of push on connection.
Assuming you are soldering the connections I can see no point in plating. The solder should envelop the connection and give you the best joint possible. Any plating would add an extra layer of material ( even if it is a very low resistance ) and can only add to resistance.
I might consider plating if the contact was a push on type - like a bayonet type. But the there are a lot of connectors in a car that have no plating and do not suffer.

cheers
gaj
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noel
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Post Number: 81
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Posted on Wednesday, 01 September, 2010 - 05:29 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi gajjer
The connection is a mechanical one - an electrical plug (male) being pushed into the mating socket (female) on the solenoid. This solenoid has the unplated brass pins.

The issue is really a long term reliability one. Judging from the posts here, I think it should be ok.

thanks
Noel.

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