MCPCB: help to build MCPCB sheet

[pretmetled]

If you want to go deeper understanding thermal management, you should go to the webs of the main manufacturers. Phillips Lumileds, Cree and Osram has excellent application notes about it.

Yep, thanks for the reminder. No single app note seems to have all the info I was looking for, but by reading through <too_many> pdfs you can get a reasonable understanding. Especially Cree and Osram were good. Still no info on HASL vs ENIG, but I guess I'll just have to try and see. With a bit of luck HASL will work out just fine, and I can use the cheapo PCB option.

 

[CKOD]

Yep, thanks for the reminder. No single app note seems to have all the info I was looking for, but by reading through <too_many> pdfs you can get a reasonable understanding. Especially Cree and Osram were good. Still no info on HASL vs ENIG, but I guess I'll just have to try and see. With a bit of luck HASL will work out just fine, and I can use the cheapo PCB option.

HASL is cheaper, ENIG is more pricy, obviously, HASL actually isnt level ;p so stuff like BGA's, and other super fine pitch stuff wont sit nicely for reflowing, and can have issues with "low" pads not even joining to the solder balls. ENIG will stay solderable longer since the gold doesnt oxidize, but then you may have to worry about gold embrittlement if you wanna consider every aspect.

For power LEDs etc, HASL is fine, if you have a 3 year old board with tarnished pads, clean the whole board before you use it with something like a not overly aggressive scotch-brite pad, (no metal!) and make sure to use flux. Easy enough, nice and cheaper too.

 

[pretmetled]

Thanks! I was hoping for someone with personal experience on it to come along.

Yeah, I wouldn't use HASL for bga packages. So I guess HASL is fine for leds, despite the uneven surface finish messing a little with the thermal contact surface. I was hoping for that to be the case, but always nice to have some confirmation. And it's good news too, because cheaper is better. Now if only I could find a board house that offers white solder mask for the same looooow prices as the green option I'd be all set!

 

[SemiMan]

Thanks! I was hoping for someone with personal experience on it to come along.

Yeah, I wouldn't use HASL for bga packages. So I guess HASL is fine for leds, despite the uneven surface finish messing a little with the thermal contact surface. I was hoping for that to be the case, but always nice to have some confirmation. And it's good news too, because cheaper is better. Now if only I could find a board house that offers white solder mask for the same looooow prices as the green option I'd be all set!

HASL is process dependent, i.e. some board vendors do much better than others. ENIG is definitely more consistent no matter who does it.

Of course are we talking home builds here or high volume? If it is low volume, small process irregularities from HASL are going to be very minor (not a concern) compared to anything you are going to do to put paste down. Even in volume production, a good screen print with HASL is likely better than a poor screen print with ENIG.

Semiman

 

[pretmetled]

HASL is process dependent, i.e. some board vendors do much better than others. ENIG is definitely more consistent no matter who does it.

Of course are we talking home builds here or high volume? If it is low volume, small process irregularities from HASL are going to be very minor (not a concern) compared to anything you are going to do to put paste down. Even in volume production, a good screen print with HASL is likely better than a poor screen print with ENIG.

Semiman

Maybe in the final stage I'll use an assembly house, but first runs are definitely home builds. I'd use a plastic paste stencil, but maybe for a led board with 16 leds on it dispensing it directly to the pads makes more sense. Putting 32 drops on location might be less work than messing with a stencil.

 

[jashhash]

pretmetled, if you can produce this MCPCB cheap enough I might have a lot of work for you. I work for a street light manufacturer and my specialty is retrofitting our product line with LED's. I have come to realize one of the biggest limiting factors for integrating LED's is the low heat transfer rate of traditional MCPCB. I Like the idea of printing a circuit directly onto an anodized surface since that would be great for heat transfer. However, for something like this to be viable it would have to cost about the same as the MCPCB that I buy right now. Right now I order my MCPCB from China and a complete MCPCB circuit board cost me about $190 - $250 per sq meter. This cost is for the complete circuit board (all the solder pads, and traces).

 

[alpg88]

what would be cool to build, and pbly have demand for it, a star that has driver on it, so far only lux-rc has tripple - single xp-g with driver on the same star.
there are lots of makers that make stars, but only 1 that makes star with driver.

 

[alpg88]

I have come to realize one of the biggest limiting factors for integrating LED's is the low heat transfer rate of traditional MCPCB. .

not all stars created equal, some have poor heat transfer, some have very good rate.