I emailed Ideal this morning. Surprisingly, someone wrote back. Here's what I wrote:
"Good morning!
I'm not an industrial customer or anything like that. Just an LED hobbyist.
I was talking with another hobbyist on a forum about how to install the 50-2234C Cree CXA30 COB holder. There are two little dimples on the outer circumference of the holder. He felt that Ideal made those dimples to key into holes on the heatsink surface. He ground the dimples off so that the holder would set closer to the heatsink.
I told him that was a mistake. I believe the dimples act as insurance against crushing the COB with the holder, and also to avoid direct contact between the metal holder frame and the COB. My understanding, after assembling a few of the COB holders onto CPU heatsinks, is that the Ideal COB holder should touch the heatsink surface at 4 points.
Contact should be at the two dimples, and the two little plastic nubs sticking out from underneath the white plastic wire receptacles.
Do you have a moment to tell me whether I'm correct or not? There are people following his forum thread and I don't want other hobbyists to grind off the dimples on their holders!"
Here's what he wrote back:
Hello (deleted),
Thank you for your interest in our Chip-Lok products. Yes, you are correct, the dimples are important and need to make contact to avoid adding too much downward pressure on the COB. The plastic nubs actually help position the contacts, so all four must contact the heat sink. The design of the product is such that we provide the maximum pressure onto the COB which makes the contact to the heat sink, it is not important for the metal holder to make the contact to the heat sink. Our design actually acts as a secondary heat sink pulling 5-10 degrees of heat off of the top of the COB.
Regards,
Barry Reynolds
Engineered Solutions OEM Sales Specialist
IDEAL INDUSTRIES, INC.
1375 Park Avenue
Sycamore IL 60178
Phone: 800-435-0705, Ext. 271
Direct: 815-895-1271
Fax: 888-222-6140
Cell: 815-751-0977
www.idealindustries.com/products/oem/
So, I'm not going to argue with anyone about this. The holders are designed to touch the heatsink at the dimples, and the two little white plastic nubs, just like I said before. Those of you who are determined to do it differently, knock yourselves out. I was going to say that the heatsinks cap'n used are wrong for the Ideal holders, but it looks to me like if you were careful to drill the holes so that the white plastic wire receptacles were lined up with the diagonal axis they would just barely fit.
to bondoman - If I knew how to make a video and post it online I'd do it. It's virtually impossible to explain it in a forum. As previously stated, and confirmed by Mr. Reynolds, the holder is supposed to contact the heatsink at four points. Those 4 points are spread out equally, like four corners of a square. The holder is only supposed to bear down on the COB at two points. See the white plastic fingers that reach in from the perimeter of the holder? Those two plastic fingers have wire inside, and little metal contacts at the tips. When it's all put together correctly, those fingers push down on the COB's two electrical contact patches. The two fingers are all that's pushing the COB against the heatsink. There may be a tiny amount of contact in the corners, where the COB fits into the little recesses that are designed to hold the COB during assembly, but the lion's share of the work is done by the fingers. I used the term "wire receptacles" earlier - the fingers are the same thing.
Try as I might, I know that a verbal explanation is insufficient. You just have to see it in person to understand. And in case you think I'm off my rocker, I've built dozens of PC's. I know that the heat-producing gizmo (CPU or COB) has to make good contact with the sink or heat transfer is severely compromised.
I don't wish to make cap'n feel bad or anything. I don't have a need to prove I'm right. I just want people who are spending their money and time based on advice gleaned from these forums to have the best information available.