Power Wire, MCPCB trace and XPG focusing issues

[kosPap]

edit: I bumped this thread waiting for an aswer on the wiremcpcb trace thickness issue....TNX

well here are 2 question in one post...

My first concern is wire to LED thickness and PCB trace....

The thicker the wires the better, but is there a real reason for when the MCPCB trace to the LED electrical contact has a smaller cross section taht the wire itself? Or as a matter of fact the soldering pad is so small to be covered by the wire?

Next issue..wire thickness and XPG focusing...Tried many times to focus properly an XPG in a P60 module but....Using 0.30mm thick wire there was so much the reflector could go down....the cituationwas aggavated by the plastic cover melting and getting thicker at its end.

sort of made it by filing the wire/solder blob. Should I go thinner?

BTW.....No luck in finding silicon covered wire here in Greece, in small amounts and diameter...I know its "sleeve" is thinner and will gain me some room, but .....:mecry:

 

[bshanahan14rulz]

You might need to find a different mcpcb. I know on my P60 reflectors there is a gap that they allow for the solder connections to the mcpcb.

 

[kosPap]

mine do not have.....so this may be a reflector thing....

what kind reflectors do you have? Mine are the KD and they are flat on the bottom

 

[bshanahan14rulz]

I am not really sure, it was a smooth blank drop-in.

The groove I'm talking about, I will try to describe:

Looking at the back of the reflector, starting from the center and working my way out I see the hole that the LED sits in. Around this hole it is flat for about .75cm. Then it recesses a little deeper until the threaded inner wall.

This recess is great for whatever size MCPCB they usually use for these drop-ins, but on the 8mm mcpcb that I have for my XP-G it doesn't line up.

On one build, I had a similar issue since I was soldering to the top-side contacts of an XP-E emitter. I used solid core copper wire and flattened the end with a hammer before soldering it on there flat :devil:

 

[kosPap]

exactly as I imagined it would be...in fact I was thinking of doing this to my reflectors, by hand and stone!

Thansk...kostas

 

[kosPap]

bump bump

 

[HarryN]

PCB traces tend to be pretty thin and narrow, as you have seen. In most cases, it works fine, because the length is so short, but physics don't change, so if things overheat, the lead will "blow" - just like a fuse.

PCBs traces are usually designed for "mean time to fail", not "lowest resistance", and MCPCBs are no exception. One of the "benefits" of MCPCBs is that since they are better for moving the heat away from the trace, you can use even smaller traces (from a reliability perspective). Obviously, the power losses are not improved doing this.

There are a lot of computer motherboards that have failed due to too thin / narrow of traces feeding power to modern CPUs. A few companies have gone from 0.5 or 1 oz copper to 2 oz copper to help deal with this. (thicker). I am using 2 oz copper based boards on my SL-20x project (see sig line) but frankly that is pretty rare due to the cost and supply challenges. Getting 2 oz copper is usually only available on high volume boards.

At 1 amp currents, normal PCP methods are fine, as long as the heating is due to the trace - not other components. At 4 - 5 amps, it takes special care, usually thicker copper or MCPCB. If you have components on the board that generate significant heat (same an AMC driver, which is more or less and LDO) then the two thermal loads need to be considered at the "total system" level. As you can imagine, some companies concern themselves with this more than others.

Coming back to your question, seriously consider using solder paste and soldering down the way an SMT part is intended. It really is not that hard.

 

[MikeAusC]

Kostas

0.3mm copper will produce insignificant voltage drop in a torch at 1.4 amp.

If you hammer it flat in critical places, there will be no increase in voltage drop.

 

[kosPap]

indeed....

but waht about the traces one the MCPCB especially the new KD black colored ones? too small?

and how about those people mounting SST50 on XRE 16mm boards?

as a side note...having done 2 mods with MCE mounted on the said boards I could not get more than 2.2A to the LED...such mods are a resistance monster for sure....

But pne baord sold by Shiningbeam had 2 solder pads for each pole (you know one pad in each corner of the LED).
I wonder what would happen if I soldered 2 neg and 2 pos wires to it...

woudl I gain anything over it? or would the trace limit any gains?
(one can solder the wire directly on the MCE of course - but I am exploring a SST50 mod)

thanks..kostas