How do you gauge if a heatsink is flat?

[nut]

I planned on lapping my heatsink, but before i do need to know if i really need to. How can i gauge whether a heatsink is truly uniform and flat as they say. Are there any techniques that i could do in order to test this? Thanks

 

[Cheesy Peas]

if you run your finger nail accross it and feel no ridges then thats pretty flat

im lapping mine right now.. but mines had some big scratches in it from being left around

 

[ronin1967]

If you want to ensure real flatness there is only one way:

1. Coat the entire bottom of the heatsink(machinists use a special colored dye, you could use magic marker).

2. On a large FLAT surface(a piece of glass or a mirror are usually readily availed in the home) place a piece of very fine grit sandpaper.

3. Apply even pressure to the heatsink while you gently sand it in a figure-8 pattern.

You will notice spots where the dye or magic marker have been removed and spots where it has not. The uncolored spots are high spots.

4. Repeat steps 1-3 until you see no more highspots

This is called lapping, it will ensure a flat level surface.

 

[nut]

thank you very much. I guess it doesn't mater what kind of marker it is. Would a permanent marker be fine like a Sharpie?

 

[Ge|atinousFury]

When I lapped my TC-4 on a piece of glass with 800 grit sandpaper, I could clearly see that the center of the surface of the waterblock was concave. No marker was needed. The lapped part stood out from the unlapped part.

 

[Daemonfly]

Yeah, you will see the scratches from the sandpaper compared to the normal base. But you can use a sharpie if you think you'll need it.

I'm lapping my soon to be waterblock here at work as I type, lol.

 

[markshelby]

The Quick and Dirty Way

Put some thermal compound on your heatsink. Attach it on the processor firmly.

Then take it off and look at the place where the processor touched the heatsink. If all the compound squeezed out the sides so that you can see the bottom of the heatsink without any patches of compound in the way, then your contact isn't too bad.