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Selecting Material for connector/contacts

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Snajo

New Member
I'm trying to determine the ideal type of metal to be used for the manufacture of this connector for an LED module.

Use: Automotive Interior and upper engine compartment installation
Power: 2.5 to 3.0 Watts
Weight: ~0.2 gramms (total module with connectors)
Wire: 1mm diameter ~18AWG

Concerns: Solderability, Corrositon Resistance, Hardness, Cost (not super important at low quantity (1k pieces), but important if I do a second run of 10k+ pieces).

I've used tinned copper in the prototypes (excuse my messy soldering) and while it's great for hand-made parts, I would like something harder when this item is manufactured. I'm concerned that if I use nickel plated steel or stainless steel, this might complicate assembly. What might be some good choices?

Anyway, I appreciate any assistance.

About me: I'm an Electrical Engineering student that has a small business that functions as a hobby and learning tool. EE is a second career for me. For most of the last 13 years I've been either an active duty Airman or Solder.


 
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spec

Well-Known Member
Most Helpful Member
Hi Snajo,

Welcome to ETO.

About your contacts: can you tell us more about the application. Will you be soldering to the contacts, or will they be in contact, with another conducting material?

Also, will the loops of wire be used to support the LED assembly?

spec
 
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Snajo

New Member
Oh, the module mounts either using tension or compression. In one application they mount between two parallel posts with notches. In another they mount between a fixed post and a spring that pulls. Lastly, they mount between springs.




 

spec

Well-Known Member
Most Helpful Member
Thanks for pictures.

You haven't asked this, and I hate to say so, but you should not have solder/conducting connections subject to mechanical forces especially when there is vibration as in a road vehicle: it is a recipe for trouble because the joint tends to fracture.

The other point is that connections, that are not soldered, should be of the same material. If two different materials (metals) interface you can get problems with reactions.

Sorry to be negative, but perhaps somethings for you consider, especially as you are planning on going into production.

spec
 

Snajo

New Member
No worries. All valid concerns, but they haven't presented as problems with the standard version of this light that uses flat loops. I'm assuming the loops are steel, but I'm not sure how to tell.

I've seen pitting in the engine compartment lamp with the stock bulbs. I don't generally recommend the light for engine compartment use, but it's regularly requested and used there. I recommend the LED module be soldered in place when installed there after cleaning the copper of corrosion.

None of the LED modules installed in the interiors have failed at the contact joints.

I suspect the issues are minimal because the lights use a relatively low current (200mA max at 14V), the solder joints are relatively large (1mm diameter) and through-hole, and the mass of the module is small at 0.2 gram. I'm not sure of the force used to hold them in place, but the bulbs these replace are glass with metal end-caps.

Unless I learn anything new between now and when I place the order, I'll try the nickel plated steel. At worst, the nickel should corrode, sparing the copper or brass from deterioration.

http://www.galvanizeit.org/design-and-fabrication/design-considerations/dissimilar-metals-in-contact

Thanks!

I have much to learn.
 

spec

Well-Known Member
Most Helpful Member
You can tell if a material is steel by using a magnet.

By the way most through hole resistors have plated steel leads rather than brass as you may think. The leads are steel to give strength.

I'm pretty sure your approach will be fine.

spec
 

Snajo

New Member
:facepalm: Why did I not think of that?

Yep... the original wires stick to magnets. I suspected they were steel, but I figured it was primarily due to cost. The steel wire is a bit harder than the tinned copper I use making them by hand, but both get the job done. I'll try to remember to post again when I've made it through the process. I would like to think that I'll have fewer questions after I learn more, but we'll see!

Thanks for the audience and all the suggestions.
 

kubeek

Well-Known Member
Most Helpful Member
It seems you are replacing an omnidirectional filament lamp with a directional LED light, I would be worried that your board will be prone to rotate about the long axis and provide unpredictable intensity especially due to vibrations.
 

Snajo

New Member
These lights are generally off while the vehicle is moving as their use would be distracting to the driver. The compression mounts are both notched, preventing rotation. The tension mount method prevents rotation .

If loose, the metal mounts can be bent slightly to adjust compression or tension. The lamp housings I use for bench testing have put up with lots of abuse over the last three years. The mounts are pretty flexible. Mallagable? Whatever the opposite of brittle is in this case.

There is a bridge rectifier so it works regardless of mount polarity. With two versions, each of the up/down/left/right aiming directions are covered between the two versions of the light. As far as intensity due to vibration, in practice it's just on or off. This isn't my design - the company that makes the lights designed it around my specifications.

I do not hide the fact that I have a lot to learn. Despite everything against it, the light works pretty well.

The flat loop LED below is used in the mount below. It doesn't rotate. I only used the other light in this mount as an example.

 
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