laping heatsink

athalonheadathalonhead Member
edited June 2005 in Hardware
There was a thread or stickey about laping the heatsink. I thought it was here but I cant find it. anyone know where it is?

Comments

  • JChretienJChretien Vancouver, BC, Canada
    edited June 2005
    http://www.short-media.com/forum/showthread.php?t=11263&highlight=lap+heatsink

    it talks about picking the grit of sandpaper.

    As for lapping, i believe you wet-sand on a piece of glass to ensure absolute smoothness.

    i could be wrong though. Best to wait for a 2nd opinion
  • RobRob Detroit, MI
    edited June 2005
    Brown paper bag is one of the best for lapping to a mirror shine. I'm not sure if it's been talked about much here.

    Also, some people would argue that some small imperfections in the heat sink would increase the surface area and when used properly be more efficient than a mirror finish. The commercial stuff I use on servers has an intentional pattern ground into them.

    Thermal grease will soak into these spots, and artic silver should be worked into the heat sink and wiped off before seating.
  • athalonheadathalonhead Member
    edited June 2005
    This coolermaster hsf was a great deal but the cpu mating surface was real rough.
    I used glass and back and forward pattern turning 90 degrees every 20 strokes. I started with 400 grit to get all the marks out then went 1000 -1500 -2000 grit. Its not mirror finish but I think artic silver5 will do the rest.
  • edcentricedcentric near Milwaukee, Wisconsin Icrontian
    edited June 2005
    In theory there is an optimal smoothness, and too smooth is bad.
    In practice we can't get the surface perfect enough to matter.
    I am more concerned about fltness than smoothness. Don't confuse the two. For a heat sink flat is better than smooth.
    I work mine down through 800 grit wet. I use a piece of plate glass as my base.

    I was reading the other day about a guy that works for Mitutoyo (large Japanese measuring instrument company). He can lap metal plates flat within one micron. Now that is flat.
  • nicklogannicklogan
    edited June 2005
    I used to hand lap semiconductor wafers to similar tolerances and found that a figure 8 movement produces a flatter profile because it reduces the rocking caused by a back and forth movement. On a square surface reducing rocking to keep the edges from being over polished gets you a flatter overall finish. I finish off a copper heatsink with 2000 or 4000 grit paper and then use 3 um grit until I can see my eye pupil in the reflection. Probably it's overkill - the 2000 grit would be enough. I agree with edcentric, flatness is key.
  • DonutDonut Maine New
    edited June 2005
    Is lapping the heatsink worth the effort? Are we talking a noticeable difference?

    Yes a very noob question, but with as warm as its been...
  • athalonheadathalonhead Member
    edited June 2005
    My coolermaster heat sink was real rough and it wasent flat either. It took awhile with 400 to get it flat.I was going to try Robs brown paper bag idea but it is probally overkill.
  • NiGHTSNiGHTS San Diego Icrontian
    edited June 2005
    Donut wrote:
    Is lapping the heatsink worth the effort? Are we talking a noticeable difference?

    Yes a very noob question, but with as warm as its been...


    Tell me about it, this northeastern humidity is terrible lately! :shakehead

    I'm also interested in knowing, as I've got 800-1200 grit paper for a project I plan on doing to my keyboard, mouse, and controller.
  • LeonardoLeonardo Wake up and smell the glaciers Eagle River, Alaska Icrontian
    edited June 2005
    Is lapping the heatsink worth the effort? Are we talking a noticeable difference?
    Excellent question. It's important if you overclock your system significantly and need every bit of cooling efficiency that can be mustered. For day to day normal operation of a non-overclocked machine, the utility is negligible. The combination of using high quality thermal paste with a well-lapped heatsink is usually good for 2-4*C additional thermal efficiency. The cruder the finish on a heatsink's contact area, the greater the benefit lapping. If your system experiences heat-related crashes, lapping would be advisable. The first steps to take though, would be: freeing the machine (especially the fans) from dust, removing the factory heatsink pad (TIM) or paste, and applying quality paste.

    As to humidity, moist air removes heat more efficiently than dry air. But of course, humidity has the oppositie affect on humans. Humid air lowers the rate at which perspiration evaporates into the air, thereby lowering the rate at which body heat is dissipated. Machines that require thermal dissipation generally perform much more efficiently in humid areas than dry areas. In general, air conditioners and radiators perform much better in the South than in the desert Southwest. Not only is this solid physics, but I've experienced it.

    Forgive the long-winded answer to your question. Heat is a topic I really pay attention too. I enjoy the coolness of Alaska! :D
  • DonutDonut Maine New
    edited June 2005
    Usually I enjoy the coolnes of Maine also, but a couple of 90 deg. days put some hurting into my folding boxes. Looks like I'll be lapping a couple of heatsinks on my Xeons soon. :D

    Living in the Phoenix metro area when I was a teenager made me appreciate the cool.
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