Previous Posts:
TI and Würth Elektronik LED RoadTest+ application and un-boxing - Blog 1 - Nov 10
LED Road Test - Software issues - Blog 2 - Nov 26
Related links:
search for a PCB for Würth power leds
Introduction
I was planning to use the Würth leds: http://katalog.we-online.com/led/datasheet/158353060.pdf, for my project, so I asked for some Daylight (5000K) and Cool White (6000K) samples. A few days later I got two big bags in the mail, each containing 15 LEDs.
So the next challenge is how to get a proper PCB and heatsink. For my application if possible the PCB should be ring shaped, for mounting around a lens.
Würth told me that there is a thermal pad in the middle of each LED. Usually the way how you can solve the dissipation of those LEDs is to connect thermal pad from top side of the board to bottom where you have a heat sink (see pictures below).
On the internet there are some examples of ring shaped PCBs, like here: 24W&18W&12W High Power LED Aluminum Plate Circular Ceiling Diameter 260mm 206mm 150mm- wholesale Circular Arc-shaped Alu… Which looks very convenient to use. But that one is not designed for the Würth leds form factor.
Douglas Wong in his blog (LED Road Test - Power LEDs - Up & Running - Blog 7 Nov 24) described how he connected the Würth LEDs on aluminum circuit cards intended for other form factor LEDs. In his blog he has a picture what that looks like - he soldered twice as many LEDs as the card was intended to carry, one on each lead - using the central heatsink pad to connect each pair. A very clever solution, although I'm a little bit worried about the heath transfer from the LEDs to te board.
Dragan Knezevic pointed me to sources for PCBs dedicated for the Würth leds form factor. (25pcs 16mm Aluminium PCB Board 3535 Type for CREE XPE XPE2 XPG XPG2 XTE XPL LED | eBay) These are declared as 3535 and that's exactly what Würth LEDs are:
I immediately ordered these boards and as soon as they arrive I will complete this blog and share my experience on soldering the LEDs and look at heath dissipation and performance. I also did a search for circular 3535 LED boards, but unfortunately didn't find one. So for my application I will either place single led boards in a circular way, or use another layout.
stay tuned.