Handsolder Cree XP-G: Cut original pads?

krutzbeuazen · Mar 15, 2011

Hello everybody,

I have three Cree XP-G LEDs. They are supposed to be soldered directly onto a slab of copper, I plan to contact them from the tiny "pads" on the top. After removing the protective layer from the top pads, this works.

How do I get rid of the original pads on the bottom? I think I see the connectionpoints where the lower pads are contacted (the "via", how are they called?). I have no idea how to cut them out: Best would be to have parts of the solder pads left for better connection to the heatsink. Using a dremel to rub away the pad around the connection failed.. that stuff is just too little!

Older LEDs had the connections at the corners, which could be chipped off - No luck here I guess?

Help greatly appreciated!

Manuel

krutzbeuazen · Mar 15, 2011

..here a pic from the backside too, I couldnt find any online. And dont forget: 3.45mm x 3.45mm. The whole LED, not the die!

Manuel

bshanahan14rulz · Mar 15, 2011

To solder to the topside pads, you will have to remove some of the dome material in the corners, and even then there's no guarantee that it will be an easily solderable surface. You could instead raise the center pedestal of your heatsink by sanding down the area around it. That will leave space for wires to connect to the bottom pads. Another thing that might be worth trying is using copper foil instead of wires to connect to the bottom pads. You can isolate them from the heatsink by using kapton. Or you could just use the heatsink as one of your electrical connections and short the heatsink pad to whatever connection is easiest from your design's point of view.

saabluster · Mar 15, 2011

krutzbeuazen said:
Hello everybody,

I have three Cree XP-G LEDs. They are supposed to be soldered directly onto a slab of copper, I plan to contact them from the tiny "pads" on the top. After removing the protective layer from the top pads, this works.

How do I get rid of the original pads on the bottom? I think I see the connectionpoints where the lower pads are contacted (the "via", how are they called?). I have no idea how to cut them out: Best would be to have parts of the solder pads left for better connection to the heatsink. Using a dremel to rub away the pad around the connection failed.. that stuff is just too little!

Older LEDs had the connections at the corners, which could be chipped off - No luck here I guess?

Help greatly appreciated!

Manuel

Yes they are small and hard to deal with but not impossible. Just use the technique shown in this thread. Just only remove the electrical contacts.

krutzbeuazen · Mar 15, 2011

Thank you again, you two!

I still opt for the two top "solderpads". Kapton tape is a good idea, I forgot about this! Never used it yet, I still cant really imagine this stuff, withstanding soldering temperatures? Wow!
This will increase the distance between LED and heatsink a bit (filled with solder), but should still perform a bit better than sanding the heatsink off except the tiny middle part for the middle pad only.
I will power by 1.4A "only", for short durations and with not-so-big housing (three heads, bicycle light, the other two LEDs will just get 300mA, constantly) - so I probably think too much about it anyway, and regular star board would have been sufficient too..

Will go shopping kapton tape tomorrow, hopefully!

Manuel

Handsolder Cree XP-G: Cut original pads?

krutzbeuazen

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krutzbeuazen

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bshanahan14rulz

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saabluster

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krutzbeuazen

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