I'm sure some of you probably encountered this problem before... How do you cover heatsink holes ?
I got a possible deal on a huge heatsink but it already has holes that won't match my needs (I did check carefully....). Some holes will end up beneath the heat transfer area of the devices I intend to install....
I know different materials will have different expansions with temperature variations so it's probablematic but TBH I don't have experience with this. Is there a tried best method ? I guess another option would be leaving the holes and ignoring them but this will surely affect heat transfer... The question is how much...
Yes, I know an even better option is to pass on the deal, but it's a huge heatsink and a great deal.....
I got a possible deal on a huge heatsink but it already has holes that won't match my needs (I did check carefully....). Some holes will end up beneath the heat transfer area of the devices I intend to install....
I know different materials will have different expansions with temperature variations so it's probablematic but TBH I don't have experience with this. Is there a tried best method ? I guess another option would be leaving the holes and ignoring them but this will surely affect heat transfer... The question is how much...
Yes, I know an even better option is to pass on the deal, but it's a huge heatsink and a great deal.....
Threaded holes or plain? Could probably hammer in copper or aluminium rod into the holes like a rivet and then file off the excess? If threaded perhaps brass threaded stock?
@rayma
Nice to know . Is there a general consensus on that ? Cause less heat transfer area = less transferred heat.
@Mark Tillotson
It's threaded aluminum. Brass is very weak, wouldn't it be better to use the same material ? Trouble is I don't have access to metal work machinery... I guess I could try to find some aluminum screws that would cover the holes and cut/sand the surface afterwards... But would it be worth the hassle, that is my question...I'm already somewhat OCD and a procrastinator, so if I start losing time with details I'll end up not finishing it, that's pretty much what happens to me all the time .... 🙂
Nice to know . Is there a general consensus on that ? Cause less heat transfer area = less transferred heat.
@Mark Tillotson
It's threaded aluminum. Brass is very weak, wouldn't it be better to use the same material ? Trouble is I don't have access to metal work machinery... I guess I could try to find some aluminum screws that would cover the holes and cut/sand the surface afterwards... But would it be worth the hassle, that is my question...I'm already somewhat OCD and a procrastinator, so if I start losing time with details I'll end up not finishing it, that's pretty much what happens to me all the time .... 🙂
Post photos of the sink. A few small holes would not concern me, and patches will never be properly flat.
Is it anodized black? That's more important.
Is it anodized black? That's more important.
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Hi,
You can use one of this aluminum compound.
https://www.amazon.com/Hy-Poxy-H-450-Alumbond-Aluminum-Repair/dp/B001RMITIA?th=1
You can use one of this aluminum compound.
https://www.amazon.com/Hy-Poxy-H-450-Alumbond-Aluminum-Repair/dp/B001RMITIA?th=1
Sorry but no.
NO adhesive, no matter how much aluminum powder it incorporated will become even close to solid metal.
I once bought some 300 already drilled-for-TO3 heatsinks for peanuts, but I use TO218/247 transistors.
Originally I riveted solid aluminum bar in, completely filling non threaded holes, but as mentioned above, sanding (even with a mini belt sander) does not make surface really flat, because the sanding band has some elasticity.
A metal file will do the job, because it is rigid, but takes more man-hours than money saved , milling surface would be perfect but I don´t own a mill, so ....
Hate to junk anything (like most of us here) so solution was to get a proper width (around 20mm) by 2.5 mm thick extruded aluminum bar, cutting it into proper length pieces, punching them and using them as a heat spreader between transistor and heat sink, using thermal paste on both mating surfaces of course.
Works like a charm, for all practical purposes negating existing holes on actual heatsink, which now do NOT need to be filled.
Transistor case to spreader plate contact is unhindered (since it gets only one hole per transistor, the mounting one) , and spreader spreads it around old heatsink holes to where it meets solid metal.
NO adhesive, no matter how much aluminum powder it incorporated will become even close to solid metal.
I once bought some 300 already drilled-for-TO3 heatsinks for peanuts, but I use TO218/247 transistors.
Originally I riveted solid aluminum bar in, completely filling non threaded holes, but as mentioned above, sanding (even with a mini belt sander) does not make surface really flat, because the sanding band has some elasticity.
A metal file will do the job, because it is rigid, but takes more man-hours than money saved , milling surface would be perfect but I don´t own a mill, so ....
Hate to junk anything (like most of us here) so solution was to get a proper width (around 20mm) by 2.5 mm thick extruded aluminum bar, cutting it into proper length pieces, punching them and using them as a heat spreader between transistor and heat sink, using thermal paste on both mating surfaces of course.
Works like a charm, for all practical purposes negating existing holes on actual heatsink, which now do NOT need to be filled.
Transistor case to spreader plate contact is unhindered (since it gets only one hole per transistor, the mounting one) , and spreader spreads it around old heatsink holes to where it meets solid metal.
Depends on the thermal intensity of the device, ie the area and heat dissipation from the device.
STKs are famous, they need good thermal contact.
As a thumb rule, 5% of the area can be left open, or as JMFahey says, put a spreader.
If excessively large, use a saw, cut up to useful size....avoiding the holes.
And why does it have holes?
Extruded aluminum sections start at about$7 a kilo here, so how much of a great deal was this heat sink?
I have used window and curtain channel bits as heat sinks, free as scrap from the aluminum fabricator!
Some photos and device details, please...
STKs are famous, they need good thermal contact.
As a thumb rule, 5% of the area can be left open, or as JMFahey says, put a spreader.
If excessively large, use a saw, cut up to useful size....avoiding the holes.
And why does it have holes?
Extruded aluminum sections start at about$7 a kilo here, so how much of a great deal was this heat sink?
I have used window and curtain channel bits as heat sinks, free as scrap from the aluminum fabricator!
Some photos and device details, please...
+1 for a heat spreader. Just get some 3-5 mm thick aluminum flat bar or sheet, mount your devices to it, and mount it to the heat sink.
Tom
Tom
why would you even bother? Are we talking about one or two holes here and there, on that 'huge' heatsink, or it is more like swiss cheese like? As others stated, whatever you do it won't be like solid aluminum... why don't you just move components a bit and forget about them holes?!
My in-laws said they had a lawn, nice...
After my wedding I went to their house, and found a 8' x 8' patch of lawn, which I felt was small.
They were happy with a place to sit outside.
Everything is relative...
Here, huge may mean slightly over size.
Without more details, difficult to answer in a way to solve the problem.
After my wedding I went to their house, and found a 8' x 8' patch of lawn, which I felt was small.
They were happy with a place to sit outside.
Everything is relative...
Here, huge may mean slightly over size.
Without more details, difficult to answer in a way to solve the problem.
It would be even simpler to get a proper heat sink, they are not expensive if you know what you are doing, and have a fair idea of the dimensions required.
Al you need is a piece of metal that will dissipate heat at a higher rate than it recieves, need not be aluminum... steel, zinc and brass are also candidates.
Al you need is a piece of metal that will dissipate heat at a higher rate than it recieves, need not be aluminum... steel, zinc and brass are also candidates.
Steel is a poor choice, around 10 times worse than copper, and stainless is worse. That's why cooking utensils are made of stainless, one end can be boiling hot without the other burning you... Aluminium is light and has good thermal conductivity, which is why its the commonest choice for heatsinks - its also extrudable which really helps manufacture.
Thank you all for the replies. The heatsink deal was a local one and it's now gone. The discussion is very interesting nonetheless so please go on.... I guess it's better this way I'll get a proper one...
Some things I noticed though, the glue compound mentioned above does not mention the thermal conductivity in the spec sheet, it's use seems to be more on the side of physically stopping leaks in stuff like car radiators etc... The hole spacing was standing in the way of some devices if I was to use them like I planned, unless some were really on the limit of the heatsink... I like to keeps things tidied up...
The idea of using an intermediate plate I think was the best....
Regarding the prices I see some big ones (the one I was looking at was about 5Kg, dimensions approximately 340 x 160 x 80 mm) going for more than 100€ on eBay, so it's not that cheap anymore. They used to be....
Some things I noticed though, the glue compound mentioned above does not mention the thermal conductivity in the spec sheet, it's use seems to be more on the side of physically stopping leaks in stuff like car radiators etc... The hole spacing was standing in the way of some devices if I was to use them like I planned, unless some were really on the limit of the heatsink... I like to keeps things tidied up...
The idea of using an intermediate plate I think was the best....
Regarding the prices I see some big ones (the one I was looking at was about 5Kg, dimensions approximately 340 x 160 x 80 mm) going for more than 100€ on eBay, so it's not that cheap anymore. They used to be....
Note that JdAo is in Portugal where the economy is quite different to India where it seems you can buy goods very cheaply.
DIY....heat sink is supposed to transfer heat to the atmosphere, or at a stretch, a cooling medium.
You can use the head from a bike engine as a heat sink, or a piece of iron, the ability to dissipate heat must be more than the heat input.
I did all those in college, and when running a leaf spring plant, where heat treatment is very important.
As far as prices go, standard aluminum sections for windows should be available at a reasonable price anywhere in the world, and they are useable as finned sections, the wall side is nearly flat, you can cut off excess edges with a saw and file.
Here the merchants will insist on a full 12 to 20 foot length, and may be a higher price for difficult to sell sections.
So it may be easier to buy a chopped section for use as a heat sink, and they are readily sold as per device package by merchants here.
Regular sections, window fabricators will sell you the small pieces you need, a three track window section is good enough as a heat sink in the proper length.
And even a bike, car or truck piston can be put to use, a friend made a nice ashtray by parting off a truck piston at the gudgeon pin centre...he got nice half circles there.
The piston crown was faced, and became the bottom of the ash tray...
It looked nice, he had buffed it, and good quality Aluminum does not tarnish easily.
I detest smoking, only saying that it was a decorative use of scrap metal...
You need to be creative, this is do it yourself, and the look can be done to choice.
340 x 160 x 80 mm will be good for about 300 watts, so it is overkill for most projects...and like I said, 5 kilos at 8 Euros/ kilo is 40 Euros for a new one without holes...
So the poster saved some money by not getting it.
You can use the head from a bike engine as a heat sink, or a piece of iron, the ability to dissipate heat must be more than the heat input.
I did all those in college, and when running a leaf spring plant, where heat treatment is very important.
As far as prices go, standard aluminum sections for windows should be available at a reasonable price anywhere in the world, and they are useable as finned sections, the wall side is nearly flat, you can cut off excess edges with a saw and file.
Here the merchants will insist on a full 12 to 20 foot length, and may be a higher price for difficult to sell sections.
So it may be easier to buy a chopped section for use as a heat sink, and they are readily sold as per device package by merchants here.
Regular sections, window fabricators will sell you the small pieces you need, a three track window section is good enough as a heat sink in the proper length.
And even a bike, car or truck piston can be put to use, a friend made a nice ashtray by parting off a truck piston at the gudgeon pin centre...he got nice half circles there.
The piston crown was faced, and became the bottom of the ash tray...
It looked nice, he had buffed it, and good quality Aluminum does not tarnish easily.
I detest smoking, only saying that it was a decorative use of scrap metal...
You need to be creative, this is do it yourself, and the look can be done to choice.
340 x 160 x 80 mm will be good for about 300 watts, so it is overkill for most projects...and like I said, 5 kilos at 8 Euros/ kilo is 40 Euros for a new one without holes...
So the poster saved some money by not getting it.
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