Lapping

[yonton228]

I have read multiple threads across many different forums about lapping both the CPU IHS and the CPU cooler. I know that lapping is supposed to yield better results when cooling than when it comes to not lapping (specifically when either the CPU IHS or the CPU cooler is convex/concave) However I have been having a hard time finding results on before and after temps when it came to lapping. So, I have a couple of questions; 1. Did you lap either of the 2 mentioned items? 2. What were the temps, both before and after.

 

 

 

Thanks for taking the time to read this post.

 

 

 

 

 

 

-yonton228/timmy

[Mirage]

I can't really comment on lapping the IHS, as I have no actual personal experience. But I have lapped a lot of different heat sinks and I can say from experience that you can get 1-5C temp drop just from lapping the HS. Sometimes the temp drop doesn't show up at idle, sometimes only at full load. So I would say to record your current temps. then lap the heat sink first.

 

Some of the newer high end coolers come stock pretty flat, but others really need a good lapping to take out machining imperfections and flatten out the mating surface. My advice is to look at what you got. If you don't like it, start by lapping the HS. Then try it. If you are happy with the temp drop, then fine. If not try the IHS. But be careful.

 

Hope this helps a little.

[panheimer]

I suggest to verify EVERY cooler, even the high end ones wich shows a mirror finish base.

I've had a Zalman CNPS 9500 led wich worked very well, but after a LONG and HARD work (i've found it very difficult to handle...) lowered my CPU temps by 5-6° C at full load.

Then i've moved to a thermalright si128 wich initially shows very good performance (very close to the lapped zalman), since i've took it down to change the CPU.

A very bad surprise when it scrached the CPU IHS in the removal operation: the base was concave!

So i've had to lap also this one.

So my suggest is to don't trust the product's name: check every base, the cheaper one or the expensive.

Personally i don't like to lap the IHS as you are going to void the warranty and risk to tie the pin during the operation.

[Prospector]

I have lapped every sink i get including Thermaltake Silent Tower,XP-120 and now my Big Typhoon.The Silent Tower and XP-120 were both concave.The

Big Typhoon was the flattest of them all but I lapped it anyway.Generally about 1-5 degree improvement.Iv'e never lapped the IHS on any cpu's Iv'e had.

[Cuttlefish1212]

I've begun lapping my heatsinks starting with my XP-90C. After seeing a 2C drop post-lap on the XP-90C, I lapped the HS on my other rigs. I would recommend a couple of things:

 

1. Never use an oscillating sander to lap...it's too hard on soft copper and you'll wear the base down quickly. Always use elbow grease and nothing else.

 

2. Use 1500-2000 grit paper. Anything more coarse will just tear the base up IMO.

 

3. Don't lap the IHS. It's thin enough as it is and you could bend/break pins in the process.

 

4. Get the surface to a nice mirror finish. If you can shave with it, then you've done a sweet lap job

 

You're going to see different results with different HS because of the various designs. Just try it out and see how it works for you

[Clay]

Temp diffrences depend on how bad it is to start with.

Starting grit of wet-dry sand paper? Again depends on how concave or convex or rough it is to start with. Though no one has ever successfully proved lapping past 600# gives better temps.(When using TIM) I allways take mine down to 1500#. (Ohhh....Shiney!...LOL)

Seems to me being nice and flat is mostly the point here.

 

Lapping IHS is mostly for soldered IHS's.(Intels newer AMD's) Most of us just take the IHS off.

[boywander]

First and only two attempts were on the ACFP 64 and VC-RE - didn't need to on the VF900 GPU HSF. Used a good kit from pcviper.net, grits from something like 280 to 1200, then three grades of polishing compound. HSFs with clear milling marks like these two might need 400 grade to start with then on up. Mirror finish is the ideal, but you can get results from less.

The IHS, I won't even go there. :eek:

[Guest Blooz1]

I've started with as low as 400 grit sandpaper when I had a lot of stock to remove on a severely cupped base.

 

I agree that "flatness" is more important than a totally mirror finish. A lot of people feel it's necessary to leave a little "haze" so that the particles in a good TIM have an area to adhere to.

 

Cuttlefish - That's the first time I've ever heard anyone even mention using a power sander for this purpose! I agree that it would be a very bad thing to do for many reasons.

[Cuttlefish1212]

Cuttlefish - That's the first time I've ever heard anyone even mention using a power sander for this purpose! I agree that it would be a very bad thing to do for many reasons.

 

 

Well, I would think this was common sense, but I had a guy at work recently ask me which power sander would work best for lapping :confused: Common sense isn't so common

[t_ski]

I've started with as low as 400 grit sandpaper when I had a lot of stock to remove on a severely cupped base.

I've has some cheapo AL heatsinks and a Tt Volcano 7 that I've had to use 60 grit on. I hate having to sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand and sand with 400+ grit and up to get the bad ones right. Just make sure you don't go too far too fast.

 

BTW, they do make lapping machines, but most of us would not have access to one. At my last job they had a sander than used to clean up car parts (cut with a cut-off wheel to check special inside diameters and such). They'd get a pretty decent finish off them if they went through all the papers they had.

[Guest Blooz1]

t_ski-Oh yeah, there's machines that will take a finish down to ridiculous smoothness! I used to be a Quality Assurance Manager in the electroplating biz, and we had such gear for processing metallographic samples, where we measured thicknesses in the millionths of an inch!

 

I tried having a Thermalright SK7 sink done on this gear once, and it came out too gorgeous to use on a CPU! (It's tarnished and nicked up now from moving, but I still have it!) With a finish that good, I really doubt that you'd get any adhesion with the TIM, and heat transfer wouldn't be as good as if it still had some slight scratches and "valleys".

[t_ski]

Sounds nice. Better than my old job (machining car parts) where we measured in microns.