Hi Forum,

Not sure where to start but have a need for some custom LED boards for a custom automotive project - 12-14VDC supply (looking at feasibility)

Essentially I have halo light with multifunction spot lights. Todate I have has laser cut 2mm 47mm dia Alum base plate which has a 10W LED centred and 3 x 3 (or 3x5w preferred) on the outside- this 'just fits' so all ok here. The challenge as at the LEDs need operate independently it requires 2 drivers - as said the space below the plate and mounting location is tiny - so fitting all of this in is to say the least hard.

Given the vibration etc I am also worried about the service life of this approach.

What I am considering is a Alu PCB with the driver/s onboard a d surface mount LED's - So in essence All I need to do is solder in 1 x negative an 2x12-14.7VDC wires to operate.

I know many organisations use Gerber files bit I am not even sure where to begin

 

The main consideration here must be heat dissipation ... Leds are very heat sensitive , if all that is sealed in a car lamp the heat will be mostly trapped inside , reducing the life of the leds .... this may not be too much of a problem for a car since the light will not be in constant use , and outside the ambient temperature is lower ... but it's good practice to use heat sink compound between leds and heatsink .

 

The main consideration here must be heat dissipation ... Leds are very heat sensitive , if all that is sealed in a car lamp the heat will be mostly trapped inside , reducing the life of the leds .... this may not be too much of a problem for a car since the light will not be in constant use , and outside the ambient temperature is lower ... but it's good practice to use heat sink compound between leds and heatsink .

they are fixed with thermal adhesive- the metal base also joined to the alum body which is finned to cool

 

Take a look at a program called Diptrace, it's free for small hobby projects. It's fairly simple to use compared to other PCB software. Also popular is Eagle, but I'm not sure if a free version is available. KiCAD is free and open source, but powerful and with a large learning curve.

 

Hi,

Aluminum based PCBs are still expensive in small orders, even from China, even if you can order them (most fabs won't do that kind of PCBs). I would suggest an alternative: basically the "2 Layer 2oz 0.8mm" service from OSH Park. You have to design your PCB with heavy via stitching on the ground plane in order to conduct the heat from the LEDs to the heat sink on the back. Also, don't use solder mask on the back, just on the front. The bare copper on the back will conduct heat very efficiently to the heat sink, and provided that you use a single ground plane, you shouldn't have unexpected electrical shorts.

If you have to use more than one plane/fill for dissipation reasons (when using LEDs in series), then it is better to isolate the different planes (especially the ones that are not at ground potential) from the heat sink, so as not to create a short.

Of course you should still go for an aluminum based PCB, as you wouldn't have the need to take he precautions listed above in the first place. So, try to get them if you can.

Kind regards, Samuel Lourenço

 

When using bloguetronica's solution you might find it beneficial to also use a very thin layer of heatsink compound between the bare copper back of the board and the aluminum heatsink, and use the thinnest copper clad board you can get your hands on so as to minimize the thermal resistance between the component side and the back of the board.

I did that some years ago and got a very good result.

 

Ups, forgot about the heat sink compound. As DickCappels said, use a very thin layer of it. The compound will stop being beneficial if you use too much of it.

Thanks, DickCappels! I had that in mind when I wrote the answer, actually, but I took it for granted.

Kind regards, Samuel Lourenço