1st build started today Quin SST-50

Curdog92

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Not sure how this will turn out--going for mass lumens, with an attempt at handling the heat. I'm not concerned with practical use, size, or weight. I'm using 2" x 4" flat aluminum bar and turning it to build the head. The head alone will be almost 4" (diameter) x 6" (length) with imbedded copper cores under each LED. I will press in a 5/8" x 2 inch copper core into each hole in the head, then solder each LED directly to the copper heatsinks. I will cut fins in to create as much surface area as possible.

Any ideas on how long this will handle the heat of almost 100W?

Well, someday I'll get to post pics.
 

Curdog92

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I have read the rules and FAQs but cannot seem to find the post count required to attach an image. Can someone tell me how to obtain posting attachment privileges? Thanks.
 

Curdog92

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Hopefully I have figured out the image thing :)

Here's some starting photos: 1.5 inch X 4 inch aluminum bar turned to 100mm X 37mm
img3660resized.jpg


Layout with reflectors
img3663resized.jpg


First holes bored. Layout done with manual protractor. They were off by more than 0.1 inches in various directions. The copper bar will be cut for heat dissipation.
img3667resized.jpg


Since I have no rotary table or indexing head, I created this simple jig for more precision in boring holes for copper heatsinks.
img3674resized.jpg


Now they are off by less than 4 thousandths in any direction.
img3677resized.jpg


Copper bar cut to be turned and pressed into holes.
img3670resized.jpg


Press 1 & 2 went well, #3 was a couple thou larger and the soft copper expanded, got sideways before I noticed.
img3681resized.jpg


Should have used a sleeve--about 1/2 inch short of full press
img3682resized.jpg
 

Curdog92

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My plan is 5 SST-50s on this massive heatsink driven by a H6Flex at 5 amps. Practicality is not a consideration, so I'm not worried about size. I'll keep adding aluminum block with fins until it the heat can be fully dissipated. Any initial thoughts/comments/suggestions from the pros on this forum?
 

moderator007

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Wow! Thats going to be one massive head. Is this a flashlight powered by batteries?
 

cmacclel

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Looks good so far but I hate to say it you will not gain anything really measurable going with copper inserts. I made 2 complete heatsinks one out of aluminum the other from solid copper. The copper heatsink at the end of my testing kept the LED's about 10 degrees (F) cooler.

Mac
 

Curdog92

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Not sure how I'll power it away from the bench. I have a variable 30V/10A power supply to test with. With the H6Flex, I'll probably have to create a S/P battery combination to get any runtime at all with 18650s, right? (I have quite a few of these, no experience with many others used on builds I've seen in the forums.) I suspect I'll have to move up to higher capacity batteries, possibly hi drain/hi capacity RC batteries if I can get the head to produce the output I'm hoping for. (Before anyone says it, I realize I'm approaching this backwards :)

One of the main reasons I am using copper is that I wanted to solder the LEDs directly to the heatsink. I don't have star LEDs. I'm already regretting that decision--too much work for very little gain as you pointed out.
 

cmacclel

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One of the main reasons I am using copper is that I wanted to solder the LEDs directly to the heatsink. I don't have star LEDs. I'm already regretting that decision--too much work for very little gain as you pointed out.

You would of had to solder the LED's to the Copper posts before pressing them into the aluminum heatsink as it would be really hard to do it now. I have some extra left over SST-50 bare star boards if you want 6 of them PM me your address. I think I have that many left :)

Mac
 

Curdog92

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Thanks for the offer, but before I take you up on it, let me get your advice on my plan. I had intended to mill a 6.5x5.6mm rectangular platform on each copper core. (Similar to what was done in this thread http://www.candlepowerforums.com/vb...arbolight-U9-with-SST-50-driven-at-5A-by-H6CC, but my platforms would be sized to the LED die, versus a round platform as wquiles did.) Since this head is massive, a heat station or heat pen is not practical, so I was hoping to use solder paste and mount the LED dies in an oven much like many DIYers use ovens/solder paste to remount SMDs. My big question is this: can a SST-50 LED withstand 475 F in an oven? (I had planned to test this theory with a cheaper LED.)
 

MikeAusC

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. . . . My big question is this: can a SST-50 LED withstand 475 F in an oven? . . . .

For a reliable life, the ONLY data you can trust is from the manufacturers datasheet.

Heating time = 2.75 to 3.5 minutes

Max Temperature = 217 deg C for 30 to 60 sec

Cooldown rate = LESS THAN 4 degC per second

Cooldown time 30 to 60 seconds
 
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Curdog92

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Thanks for the input. Yes, I have followed quite a few of these massive builds, and they were my inspiration. I was a little off on my C to F conversion...I bought Zephyrtronics solder paste which reflows at 217-219C, same spec as the LED temp. Reflowing a SMD on a PCB is easy in an oven. Just cover the pad with solder paste, place the SMD on the pad/paste, and watch until the solder liquifies/SMD settles into place, and remove from oven. But with this massive head/heatsink, I fear there will be a huge time differential between the heatsink and LED reaching the required temperature. My plan is to preheat the head. I'll place it in the oven, and time how long it takes to get up to the required temp. Once I know the required time, then I can complete the task in one quick step. For example, if it takes the head 10 minutes to get to 217 C, then I know that at 9 minutes, I have to open the oven, place the LEDs with tweezers, wait for them to settle, then remove from oven.

Or, if I knew the LED could withstand the temp longer than specs on the data sheet, I would set it all up while cool, "cook until done" and remove. I guess I should have fully explained my question. Thanks for the input.
 

moderator007

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Maybe you could try it in a cast iron frying pan on the range. The leds shouldn't see as much heat until seated.
 

Curdog92

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That's a great idea! I had not thought of that...Thanks.

All 5 copper cores now pressed:

img3701resized.jpg


This weekend I'll mill them down to to the size of the LED die and let you know if the frying pan idea works!
 
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I can said that massive heatsink is very bad idea , heatsink must be light and have big surface and material from high thermal conuctivity .

To full use of the thermal transport routes (and lower common mass ) temperature should be spread form the thick base with placed leds to the most remote section of which is the thinnest .

The best shape for handheld torch inserts is H shape .

To optimize such big beast is very good idea to thermal isolate leds between them not to cumulate heat in the heatsink mass...

circuitBoard.gif


white area is thermal insulator in black air gap
 
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moderator007

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A propane torch may also help in the installation. You could try heating the side of the heat sink inline with the copper pedestal while in the pan at a lower temp. To bring just the pedestal where your installing the led up to temp. Then move to the next one once reflowed. This may keep the heat down on the leds you have installed while trying to install the rest. This is all just suggestion's. I do know that aluminum will spread heat pretty evenly and quickly. Wish you luck Curdog92. :wave:
 
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The_bad_Frag

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Wow that looks nice! I would add a lot of fins to the heatsink. A massive heatsink alone wont keep it cool for long.
 

Curdog92

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Thanks. I've got a plan for fins and cooling...remember I expect the head alone to be about 6 x 4 inches when done. (If that's not enough, I'll add more.) Instead of leaving the round copper cores protruding, and milling them to 5.6 x 6.5 mm to create LED solder pads, I decided to create a smooth copper/aluminum surface, and mill grooves to create the pads. See photo--haven't milled grooves yet.
img3718resized.jpg


I do have a question. What guage wire should be used to wire the LEDs up in series? And then, let's say I have to go 4 inches to the H6flex, what guage?
 
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