diy led. PCB help

[Sancho]

So I am building a ridiculous LED for a 5 gallon tank. We will be upgrading to a '15 'gallon soon. I ordered a 6 up driver board from Coralux and a storm controller. I want this to look like it was bought at a store. All the DIY 'LED I have seen are done with wires soldered to each other. Why hasent anyone used a pcb board? I am using eagle to create the pcb board and plan on surface mounting the LEDS to the completed board. Has anyone here done this? any tips? Tricks? or info I need to proceed.

[Sancho]

I plan on using Coralcompulsion par38 as a template for my design. The LED's will be in the same format with 5 dimmable channels.

[adreef]

I think the main reason no one uses a pcb is because high-power LED modules need to be mounted directly to a heatsink. A pcb - even one with a thicker copper layer - just can't move the kind of heat. If you are using a bunch of low-power, discrete LEDs, maybe you can get away with it. I'd go with 2oz copper boards (or thicker, if you can find any). Are you planning on trying to etch your own boards, or having them made for you?

[Sancho]

The LEDS will be cut down to 2.5 watts and will probably never run them at 100%. I am not to worried about the heat. The board will be al surface mount nothing on the back. So it would be mounted directly to the heat sink. I would like to try and etch it myself but it is going to be a relatively small board. 10 to 12 LEDS mounted pretty close to each other. I want to do something similar to the Lumina 5.2 with less lights. Still will have 5 channels. Channel 1. 4 deep blue. Channel 2. 2 violet. Channel 3. 1 red, 1 lime. Channel 4. 2 white. Channel 5. 2 cool blue. I have some soldering experience but have never designed a PCB before. This should be very easy to do since all the complex circuitry is on the Coralux boards.

[adreef]

2.5 watts doesn't seem like much, but that can translate into a fair amount of heat to get rid of, especially if you are putting 10 to 12 or those on a small board. If the LEDs can't shed their excess heat, they aren't going to last long.

Are you saying that the back side of the board would be mounted directly to the heat sink? PCBs are typically made from fiberglass, which means you will have a nice thermal insulator between your copper traces and your heat sink. That would mean that your heat sink would be mostly ineffective.

You might look around on the web - there are online tools for calculating PCB trace widths based on operating current, so there may be some for heat dissipation also. I'll check to see if I have one bookmarked somewhere.

[acbaldwin]

If it helps, I'm 90% sure my chinese LEDs were on PCB. Can't quite remember. Might be worth looking at how they handled heat. I'm guessing most people don't do it because it's easier/more common skill to just solder wires on.

[Sancho]

I am going to use an aluminum board. They are made to handle the heat from the led. The rapid led aurora with less lights is what I am trying to accomplish.

[jasonp87]

I am going to use an aluminum board. They are made to handle the heat from the led. The rapid led aurora with less lights is what I am trying to accomplish.

In my experience in electrical manufacturing, most LED boards are aluminum so this is a good choice. I think most people avoid using surface mount because they lack the skills to solder the smaller connections. Use plenty of solder flux too, i would use a water soluable flux ans solder paste. The trick is to use a microscope, even when you think you can see everything. This ensures you get a good solder fillet on every joint. It also helps you see cold solder joints which can cause failures over time, especially in a board that will produce a good deal of heat. I would still use a heat sink mounted directly to the board. Have the board coated in solder mask on the side the LEDs will be mounted on to protect the surface and electrical traces from corrosion caused by the moist air. Leave the backside of the board as bare aluminum and mount the heatsink directly to it using a thermal transfer paste.

I have been doing this a lng time now and have multiple certs for this stuff including soldering and inspection, If you have any other questions let me know.

[Sancho]

here is the layout and colors I ordered. 4 by 4 is the size that I am trying to stick to.It is a small fixture. For now I am going to build it with star boards and wire it. I still want an aluminum PCB made for this layout if I am happy with it. The deep blue will have 90 degree optics and the rest will have 120 degree optics. I ordered a variety of LEDs and optics to play with. Cree, Phillips, Osram. So I will have some extras if anyone needs them. Again this will have 6 dimmable channels so I am thinking about red and green on one channel and possibly adding the UV to that channel. Let me know what you guys think.

[gus6464]

Attachment 39423
here is the layout and colors I ordered. 4 by 4 is the size that I am trying to stick to.It is a small fixture. For now I am going to build it with star boards and wire it. I still want an aluminum PCB made for this layout if I am happy with it. The deep blue will have 90 degree optics and the rest will have 120 degree optics. I ordered a variety of LEDs and optics to play with. Cree, Phillips, Osram. So I will have some extras if anyone needs them. Again this will have 6 dimmable channels so I am thinking about red and green on one channel and possibly adding the UV to that channel. Let me know what you guys think.

Unless you are hanging high there is no need for optics. If the light is going to be over 24" from the substrate then add the optics. Is your plan to test out the layout and then order the aluminum PCB and reflow the emitters yourself to it? Guessing you are trying to make your own Radion puck?

If that is the case you are going to need a heatsink no matter what you do. That is huge thermal load in such a small area for a sheet of aluminum and a fan to dissipate.

As far as whites go I would switch to neutral white (4000K). A good bin neutral white has all the red spectrum you need. If you do this swap the red and the green LEDs with 2x Luxeon Lime. The violets I'm guessing are the ledgroupbuy 410nm and 430nm?