You can find the On-Semi PDF article below. I found it in less than 5 seconds with a google.
On-Semi Mounting/soldering article
Mark
On-Semi Mounting/soldering article
Mark
Hi Mark,
Too late for that. The tap extractor broke off too. Once I get the darn things out I'll drill the hole larger and tap it for a big screw. After it's cut and sanded flat I'll drill and tap it for the original size. What a complete pain! It would have been cheaper to replace the heatsink.
I used a high speed steel tap, with oil. But they were blind holes with a #4 tap. My luck ran out on the 16th hole. Guess I was tired. Oh yeah, the tap is bottomed, but I guess you knew that.
-Chris
Too late for that. The tap extractor broke off too. Once I get the darn things out I'll drill the hole larger and tap it for a big screw. After it's cut and sanded flat I'll drill and tap it for the original size. What a complete pain! It would have been cheaper to replace the heatsink.
I used a high speed steel tap, with oil. But they were blind holes with a #4 tap. My luck ran out on the 16th hole. Guess I was tired. Oh yeah, the tap is bottomed, but I guess you knew that.
-Chris
Yea 4/40 is a pain. Figure about 6 holes per tap... thats what I generally follow so taps don't break off. I still have a broken 2/56 in my VistaVision camera lens mount... I cringe when ever I think of it
.
Anodizing will also get rid of the extractor... extractors are pretty usless in that size.
Mark
.Anodizing will also get rid of the extractor... extractors are pretty usless in that size.
Mark
Hi Mark,
Yes, I just bought the extractor. I also tried heating and cooling with it before the extractor broke.
I can normally get many more holes done with a tap (that one was new), I reverse often, back out and clean about three times a hole 3/8" deep. I am keeping the broken one to finish blind holes since it broke off square.
I have drilled around the broken bits already. Now I have some bits that taper. This just gets better and better. Thanks for your suggestions Mark, time for a new heatsink. I'll cut the damaged piece off so the rest can be used.
-Chris
Yes, I just bought the extractor. I also tried heating and cooling with it before the extractor broke.
I can normally get many more holes done with a tap (that one was new), I reverse often, back out and clean about three times a hole 3/8" deep. I am keeping the broken one to finish blind holes since it broke off square.
I have drilled around the broken bits already. Now I have some bits that taper. This just gets better and better. Thanks for your suggestions Mark, time for a new heatsink. I'll cut the damaged piece off so the rest can be used.
-Chris
fcel wrote:
We are never content!
Just ask Still4Given with his building TWO Krell Klones and now getting parts for his Pass XA build.
Those ceramics are ours. ALL ours! Bwwwaaaaaha!
I think we should all appear at Mark's doorstep on Halloween, with our
parts bags, chanting, "Tek or Treat!"
Lyndon
We are never content!
Just ask Still4Given with his building TWO Krell Klones and now getting parts for his Pass XA build.
Those ceramics are ours. ALL ours! Bwwwaaaaaha!
I think we should all appear at Mark's doorstep on Halloween, with our
parts bags, chanting, "Tek or Treat!"
Lyndon
Banned
Joined 2002
Pass DIY Addict
Joined 2000
Paid Member
Mark A. Gulbrandsen said:
Hey Mark,
Could you please explain how you would lap the surface of the heatsink. I'm familiar with using lapping compound to install new valves into a lawnmower engine - you apply some lapping compound, put the new valve in the seat and use a "suction cup wand" to rotate the valve until it mates with the seat in the engine block.
What do you use to lap the surface of the heatsink?
Eric
Hi Erik,
It's as simple as using some wet / dry sandpaper and a flat surface. Start at 400 grit and use a sanding block to smooth out the imperfections. You can proceed to 600 after that. The heatsink is now far smoother than it was. It may even be flat.
I use titanium blocks, and you can get larger "stones" guarantied flat from metal shops. I once even had to get some heatsinks milled before I started the sanding process. They were bowed. Then I had to start at 320 grit to get rid of the tool marks.
There is one brand of amplifier I have to file first before sanding. They manufacturer is under the impression the one use silpads will fill the imperfections. -ahhh, no!
-Chris
It's as simple as using some wet / dry sandpaper and a flat surface. Start at 400 grit and use a sanding block to smooth out the imperfections. You can proceed to 600 after that. The heatsink is now far smoother than it was. It may even be flat.
I use titanium blocks, and you can get larger "stones" guarantied flat from metal shops. I once even had to get some heatsinks milled before I started the sanding process. They were bowed. Then I had to start at 320 grit to get rid of the tool marks.
There is one brand of amplifier I have to file first before sanding. They manufacturer is under the impression the one use silpads will fill the imperfections. -ahhh, no!
-Chris
Pass DIY Addict
Joined 2000
Paid Member
Banned
Joined 2002
Hi jleaman,
Yes, I'd recommend it. The grease forces out the tiny bit of air between the solid mating surfaces to reduce the thermal resistance. The ceramic has a lower bulk resistance than mica I guess. One would have to calculate the thickness differences and figure out the actual thermal resistance to be sure which one is better.
-Chris
Yes, I'd recommend it. The grease forces out the tiny bit of air between the solid mating surfaces to reduce the thermal resistance. The ceramic has a lower bulk resistance than mica I guess. One would have to calculate the thickness differences and figure out the actual thermal resistance to be sure which one is better.
-Chris
Banned
Joined 2002
Hi moe29,
Then take one apart and use some heatsink grease. You will see the device temperature go down and the heatsink may get warmer.
Be careful to use a thin coat of grease, I use a #2 artists paint brush. There should only be a little bit that squeezes out the edges. Too much is a bad thing.
-Chris
Then take one apart and use some heatsink grease. You will see the device temperature go down and the heatsink may get warmer.
Be careful to use a thin coat of grease, I use a #2 artists paint brush. There should only be a little bit that squeezes out the edges. Too much is a bad thing.
-Chris
Banned
Joined 2002
Hi jleaman,
I think I'm a few thousand miles from you over here in Ontario. I don't mind lending a hand, it would be great if you were close by. Couple beers and bingo. Of course I'd put you to work as well.
What exactly do you need done? X number of holes in the heatsink tapped for 4-40? Blind holes can be a real problem some times. There is always a risk of snapping off a tap (just below the surface). I admit I'm much better at it than I used to be. Some troubles as of late.
-Chris
I think I'm a few thousand miles from you over here in Ontario. I don't mind lending a hand, it would be great if you were close by. Couple beers and bingo. Of course I'd put you to work as well.
What exactly do you need done? X number of holes in the heatsink tapped for 4-40? Blind holes can be a real problem some times. There is always a risk of snapping off a tap (just below the surface). I admit I'm much better at it than I used to be. Some troubles as of late.
-Chris
Well, you don't actually use a sanding block to lap a surface!! Normally special tools made fomr brass have to be made up to lap a surface. You can start by doing what Anatec mantioned however thats not the stopping point. A true flat lapped surface is done with a precision flat lapping tool loaded with lapping compound. The tool also has to be perfectly flat and has to have grooves in it to hold the lapping compound otherwise you'll just smear it around. You can get better results by draw-filing with differnet files starting at a medium then going to almost a smooth file. If you buy top quality files thay are generally extremely flat. In the old days a set of files was a machinists primary set of tools! There is also another method known as scraping the surface. This can be done in a precision manner and sometimes is also be done to remove high spots and then the surface gets lapped to what ever presision tolerance is called for. Scraping is often used on machine ways and the very slight scrape marks which look decorative actually have two definate pirposes, they are good for holding way oil and also are good wear indicators... they will disappear as a machines ways wear out.
Surface grinding is yet another method that is alot more practical and much more widely used, its also not very expensive to have done. There are thousands of small shops that do nothing but specialty grinding!! The mounting surface of any heatsink can be surface ground to extreme precision and almost as smooth as a lapped surface....
Blind holes are easier to tap if the hole is first tapped with a plug tap, then use the bottoming tap to finish it off. This is generally the way its done in production. On shallow holes a custom plug tap has to be made up. Having the majority of the hole already tapped out for the bottoming tap takes a ton of load off of it(these type are subject to much more load) and it only has to do a small portion of the actual tapping... think of it more as a finishing tap.....
Mark
Surface grinding is yet another method that is alot more practical and much more widely used, its also not very expensive to have done. There are thousands of small shops that do nothing but specialty grinding!! The mounting surface of any heatsink can be surface ground to extreme precision and almost as smooth as a lapped surface....
Blind holes are easier to tap if the hole is first tapped with a plug tap, then use the bottoming tap to finish it off. This is generally the way its done in production. On shallow holes a custom plug tap has to be made up. Having the majority of the hole already tapped out for the bottoming tap takes a ton of load off of it(these type are subject to much more load) and it only has to do a small portion of the actual tapping... think of it more as a finishing tap.....
Mark
Banned
Joined 2002
anatech said:Hi jleaman,
I think I'm a few thousand miles from you over here in Ontario. I don't mind lending a hand, it would be great if you were close by. Couple beers and bingo. Of course I'd put you to work as well.
What exactly do you need done? X number of holes in the heatsink tapped for 4-40? Blind holes can be a real problem some times. There is always a risk of snapping off a tap (just below the surface). I admit I'm much better at it than I used to be. Some troubles as of late.
-Chris
WEll shipping 4 heat sinks and some metal to you is cheaper than payin 80$ hour here in town to get my chassis built..
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.