I want to lap my 8045, where do I start.?

[slick306]

Okay, well I want to lap my 8045 heatsink it has a lot of machine marks on the bottom. I want to know where to start?

I have sand paper

2 sheets of 400 grit
2 sheets of 600 grit
2 sheets of 800 grit
2 sheets of 1500 grit
2 sheets of 2000 grit

Where do I start, and what technique should I use whil sanding? anything special I should know?

Slick.

[Wicked Klown]

I'd say start with the 600 grit and do figure 8 motions. Then when you get it nice and flat switch to the 1000 or 1500grit. Also on the 1000 or 1500 remember to do a wet sand. Oh yea I almost forgot do all this on a piece of glass. Use Duct tape or black tape and tape down the sandpaper to the glass.

[ButcherUK]

Do it all wet, you'll get better results.

[slick306]

so I just use a little water or.?

[Wicked Klown]

Get the sandpaper nice and wet.

[mw521]

Originally posted by slick306
so I just use a little water or.? You can spit on it if you want to, but a little water is all you need. After sanding a bit wash off the paper under a faucet or hose. The paper will accumulate grit and not sand as well. If the surface is really rough take a fine large flat file and smooth it before starting.:beer: Whoops, edit here, make sure you use automotive body paper. It is waterproof. The smaller the number on the paper the coarser it is and vice versa. 200 = rough, 1500 = smooth. You have it already so you noticed this part.:beer:

[CrystalMethod]

I usually do it outside and use the the garden hose to just trickle the water over it continuously.

[mw521]

Originally posted by CrystalMethod
I usually do it outside and use the the garden hose to just trickle the water over it continuously. Me too, 'cept in winter. Where were you on [OCS] the other day, me and ROBB23 waited for you.:beer:

[DodgeViper]

Lapping, Grinding, or Otherwise Making a Heatsink or Cold Plate Surface Smooth and Flat

1. Use a piece of flat glass as your work surface (it must be very flat, and supported well)

2. Use waterproof sandpaper (sometimes called wet or dry)

3. Use lots of water (several cc at a time, the water flushes the metal particles away, keeps the sandpaper clog free, and makes it stick to the glass)

4. Depending on how flat and smooth your heatsink is, expect to spend 30 minutes or more at this work (I do it on a glass coffee table top in front of the television - you don't even have to watch the work [of course, if the show is bad enough, you can watch the work, and finish faster])

5. Use a relatively light pressure on the workpiece and move it back and forth across the sandpaper; try to keep an even downward force on the workpiece and avoid digging in the edges or corners. Rotate the heatsink 90 degrees approximately (NOT exactly) every dozen or so strokes.

6. If your heat sink is relatively flat and smooth, then 400 grit is a good place to start. If after ten minutes of work you do not see much progress (there are many pits larger than the surface roughness left by the 400 grit sandpaper), drop to a lower number grit (320) or (260).

7. Using finer grit sandpaper will help improve heat transfer: 1500 is certainly fine enough, but since you need to get such fine grades at an automobile parts store (it is used for finishing automobile paintwork), you might as well get a sheet each of 600, 800, 1000, 1500, and 2000. The more coarse grits are easy to find at a paint or hardware store 40, 60, 80, 120, 180, 220, 280, 320, 400, 600. (Grit # 40 will take the portrait off a franc coin in a minute or so; the average heatsink with faint circular milling marks can probably be started at 320.)

8. The work can be completed in less time if you step up through each grade, removing all the pits left by the previous grade before moving to the next finer grit.

9. Each time you change to a finer grit, VERY carefully wash the work surface, your hands, the heatsink, and the sandpaper. Any larger grit left when you start with a finer grade will leave visible scratches.

10. The waterproof (or wet/dry) sandpaper will last a long time. After you are through with the work, wash the sandpaper and let it dry. You can reuse it many times as long as it is not torn.

11. As an example of how fine 2000 grit is, you could use it on Mercedes paintwork and almost not notice an effect other than the missing wax polish.

12. Do not use too much pressure when sanding the heatsink; you want a flat as well as a smooth surface, and too much pressure can cause one edge or corner to be ground down more quickly (that is one reason for occasionally rotating the heatsink a random amount.) Too much pressure may also cause a corner to tear the sandpaper. If you do not tear the sandpaper, one sheet of each grade should last through ten or more heatsinks.

13. Emery cloth is similar to sandpaper, except that the base is cloth, rather than paper. It is ok for the rougher grits, but I think that I will not give as flat a surface when you move to finer grits.

14. Crocus cloth. This is a polishing material similar to emery cloth, but it has jeweler's rouge on the surface rather than emery grit. THIS IS NOT waterproof. I tried it to get a final polish, and added water. All the jeweler's rouge washed off! For a final polish, a soft cloth and a solvent that will remove dirt and grease are about all you need.

15. The method of grinding the heatsink you and I have described is the way flat mirrors for astronomical use are made (except there are machines that do the work now.) A spherical section mirror can be ground in exactly the same way, except that the grinding surface is circular, and the same size as the mirror. (The only additional action used for the flat and spherical mirrors is that the person grinding the mirror, also, after six or eight strokes, walks partially around the work surface to grind from a new angle.) This is probably not necessary for a heatsink, since the method used on astronomical mirrors makes a surface that is smooth and correct to less than 100 nanometers! At that point, thermal compound would not be necessary, and in fact, would have a negative effect. Even just going in a careful manner to the 1500 grit will give you a surface that, when placed on an FC-PGA CPU, will lift the CPU when the heatsink is raised.

16. Penultimate warning: the older CPU's with a relatively large metal cap (about 20 mm X 20 mm) can be very uneven. Sometimes the metal cap may be concave to the extent of a millimeter or two in the center. For something this bad, you will want to start with 280 grit.

17. Final warning: the FC-PGA CPU's, and the SECC2 CPU's have a very small heat transfer surface, about 11 mm X 9 mm. This is the bottom of the silicon slice the CPU is built into. It is laser cut from a single crystal of silicon, and cannot be made any smoother or flatter. DO NOT grind or polish this surface. It will not help, and the CPU gates and channels are less than 1 mm below this surface. Also beware that this will void any warranty on whatever you choose to lap!

[slick306]

Thank you very much, my sand paper says waterproof, and the 2000 is very smooth! I want to do a good job on it

Slick

[CrystalMethod]

Originally posted by mw521
Me too, 'cept in winter. Where were you on [OCS] the other day, me and ROBB23 waited for you.:beer:
Everytime I checked the server, it was empty. Even went in twice for about 1/2 hour just to see if any one would show.