what wire to use for LED "stars" ?

[RustyShackleford]

I am having a PCB assembly house reflow a bunch of LED emitters to Bergquist aluminum stars for me.  Turns out they'll also attach leads to them for no add'l cost (it's just two more pads of solder paste).  I'm wondering what wire to specify ?

I'll fold the wires back behind the the star and solder to a PCB that is attached there - but after that there will be no movement to speak of.   The assemblies will be used in some outdoor lighting, so subject to extremes of weather, but not to sunlight (other than indirect).  No significant chemical exposure, or abrasion.

I know I want 22awg copper (although 24awg can easily handle the current).   I imagine that solid or stranded would be fine, but any further thoughts on that ?  Tinned copper or plain ?  It looks like ordinary PVC insulation will be fine - able to handle the temperature extremes without getting brittle or cracking, but is it worth considering silicon or something fancier ?   Am I overthinking this ?

[bob91343]

The main reason to use stranded wire is that it's flexible and less prone to breaking if it's flexed.  Heavier gauge is stronger but in your case offers no electrical advantage.  Tinned is easier and faster to solder to than bare copper.

As for insulation, again with no adverse mechanical or chemical environment you might as well go the cheapest route.  If you need long term life, then select something impervious to UV.  I have seen many old wires fail due to insulation cracking with age from drying out.

Consider materials that won't be attractive as food for insects or rodents.

[RustyShackleford]

Consider materials that won't be attractive as food for insects or rodents.

I wonder if they have a preference for PVC over silicon, or vice versa ?   :-)

[RustyShackleford]

I'm thinking a big issue might be the tendency that insulation has to shrink (or curl) back from the bare wire when soldering heat is applied.   This would be bad, because then the wire might short-circuit against the MCPCB metal when I bend it back to attach to my circuit.  Would be better or worse with reflowing (as opposed to ordinary soldering) ?   Should I think of specifying silicon-insulated wire instead ?

[bob91343]

I believe you are overthinking this.  Shrinking insulation is only a factor when poor soldering technique is used.  Just go ahead and you won't have a problem as long as you use common sense.

[RustyShackleford]

I believe you are overthinking this.

Hey, we're engineers.   Our motto: anything worth thinking is worth overthinking !