EMRFD Message Archive 5654
Message Date From Subject 5654 2011-01-03 18:14:36 RadiosRUs Copper Plate for QRO FET A 12" X 12" X 1/4" sheet of copper plate is available from the following company;
The price is about 60% of the FET cost ($168)--so not cheap AND I also think the experts will tell you that the plate needs to be "faced" so both side are flat to insure maximum heat transfer. Thus some more costs to have the plate milled flat. That might actually require purchasing the next size up assuming the milling will remove an amount of material. The next size is about the same cost ($252) as that of the FET.
I have no connection with the company but have purchased aluminum sheet stock from them and it was very satisfactory.
Back to the bench.
[Non-text portions of this message have been removed]
5655 2011-01-03 20:40:42 William Carver Re: Copper Plate for QRO FET >From the transistors viewpoint you only need flatness over the base ofthe device. There's no need to face the whole top surface. I've had very
good luck with copper scrap from our local junkyard. That's no longer
cheap, but not as bad as buying new material.
Obviously you don't want a piece that is abused or isn't flat. Use a
steel ruler. Thick sheet that's been cut on a shear is likely to be
curved and unsuitable. I used very fine grit paper with oil on a granite
surface plate in my shop to remove burrs and nicks from the bottom and
bolted it securely to the aluminum heatsink with a very thin layer of
heatsink compound between them.
An even slicker solution for cooling four MRF150s in Motorola's EB104
amplifier is to mill a "labrynth" of grooves for water paths in one
piece of copper, then soldering a solid piece against it. WATER is
incredibly better at removing heat even with a small immersion fishtank
pump. After 1/2 hour at 500 watts of continuous DC dissipation a bucket
of water was just a bit warm.
5658 2011-01-04 05:21:26 kb1gmx Re: Copper Plate for QRO FET 5659 2011-01-04 05:52:58 ae5ew Re: Copper Plate for QRO FET Grainger sells copper bars, milled
5663 2011-01-04 08:58:12 Tim Re: Copper Plate for QRO FET Several ham radio solid state medium-power-to-QRO articles from the past couple of years take good advantage of high-end-PC-gaming thermal solutions. They can be surprisingly affordable compared to machining heat sinks and heat pipes out of billet. A recent QEX article by KD1K ("Heat Pipes", Jul/Aug 2010) points out some of the possibilities.
CPU coolers move
5666 2011-01-04 11:29:23 William Carver Re: Copper Plate for QRO FET On Tue, 2011-01-04 at 16:58 +0000, Tim wrote:
> I've never done anything as fancy as heat pipes but I use PC-clone CPUThe CPU/Fan are indeed neat/cute bases for power projects. The one I
> heat sink/fan combos all the time for assorted projects because of
> their cheap prices and easy availability.
used for a class A MRF151 attempt has tall fins of constant width from
base to tips at the fan end. What I observed is the tips of the fins
were cool but the block of aluminium at the base was more than warm, it
was HOT with 50 watts of dissipation. There was a large temperature
gradient over the length of the fin. The broad-at-the-bottom tapered fin
of common commercial heatsinks is there for a good reason.
Not long after I observed the big temperature gradient on the fins and
the high temperature of the base, I accidentally bumped the bias up
while making IMD measurements. Before I could reach over and drop the
drain current back down to one amp the MRF151 melted into a 30 ohm
silicon blob. Oops.
5667 2011-01-04 12:00:18 k5nwa Re: Copper Plate for QRO FET Stick to the better ones made for Quad Core CPUs that pull 130 Watts
and have copper contact areas, they do an excellent job. You can find
them on eBay, brand new from Intel for about $15 or less.
At 01:29 PM 1/4/2011, you wrote:
>On Tue, 2011-01-04 at 16:58 +0000, Tim wrote:
> > I've never done anything as fancy as heat pipes but I use PC-clone CPU
> > heat sink/fan combos all the time for assorted projects because of
> > their cheap prices and easy availability.
> > Tim.
>The CPU/Fan are indeed neat/cute bases for power projects. The one I
>used for a class A MRF151 attempt has tall fins of constant width from
>base to tips at the fan end. What I observed is the tips of the fins
>were cool but the block of aluminium at the base was more than warm, it
>was HOT with 50 watts of dissipation. There was a large temperature
>gradient over the length of the fin. The broad-at-the-bottom tapered fin
>of common commercial heatsinks is there for a good reason.
>Not long after I observed the big temperature gradient on the fins and
>the high temperature of the base, I accidentally bumped the bias up
>while making IMD measurements. Before I could reach over and drop the
>drain current back down to one amp the MRF151 melted into a 30 ohm
>silicon blob. Oops.
< www.softrockradio.org > < www.qrpradio.com >
< http://parts.softrockradio.org/ >
Never take life seriously. Nobody gets out alive anyway.
5668 2011-01-04 12:26:56 R Wall Re: Copper Plate for QRO FET I found the following add on CPU cooler that is specified as having a thermal resistance of 0.2 deg C/Watt (with no fan). I emailed the manufacturer twice to find out what the maximum temperature the heat pipes will work at but they haven’t (won’t) replied.
Xigmatek Thors Hammer S126384 Cooler
I also found that a lot of add
5669 2011-01-04 13:04:17 William Carver Re: Copper Plate for QRO FET > Stick to the better ones made for Quad Core CPUs that pull 130 WattsTHANK YOU for that info, that's GREAT to know and I'll see if I can pick
> and have copper contact areas, they do an excellent job. You can find
> them on eBay, brand new from Intel for about $15 or less.
one or two of those up.
5671 2011-01-04 19:05:31 kb1gmx Re: Copper Plate for QRO FET Those can work well if you recognize they are designed for forced air cooling. this is generally true for most CPU coolers.
I have a few (many) from an oddball P4 that are solid copper
including brazed copper fins. the fins are .400 high, the area
of the plate is 2.4x2.5 inches and the 2.4x4" section is .24
inches thick. I found with a pair of Dale loads on them they could get quite hot (50C) at about 40W dissipated power and no fan at all
mounted vertical for convection cooling. Putting the fan
5674 2011-01-05 01:32:25 drmail377 Re: Copper Plate for QRO FET Pete,
Unless I've got the math wrong; IMO the Cu plate from onlinemetals.com you reference is outrageously expensive. Assuming raw copper costs around $4.40 USD/lb and has a density of 0.324 lb/in^3, the $168 USD cost of the 12"x12"x0.25" example you cite carries a 228 percent mark-up!
Something like 50 percent mark-up from raw material cost to product price before shipping might be tolerable for a commodity item like copper plate in small quantity. That would make the sell price around $77 instead of $168 USD for this example.
5677 2011-01-05 11:54:36 Gary, WB9JPS Re: Copper Plate for QRO FET Another metal price benchmark: My local metal dealer--a big outfit called Alco Ir 5678 2011-01-05 12:35:27 Lasse Re: Copper Plate for QRO FET CCI sells not only RF kits but copper heat spreaders 6x8x0.375
inches... said to fit MRF150 kits, at $40 plus shipping.
Gary, WB9JPS skrev 2011-01-05 20:54:
> Another metal price benchmark: My local metal dealer--a big outfit called Alco Ir
5679 2011-01-06 05:59:26 g0kla Re: Copper Plate for QRO FET CCI do not have the copper plate in stock, due to the high prices of raw material. If they were to re-offer it, they told me it would be over $100.
I ordered a 6x8x0.375 inch copper plate from Online Metals and it was $93. That said, it is cut on a press and has a very slight bow to it. That is not an issue over the surface area of the transistors, but I'm concerned that it will not be a tight enough fit to the heatsink.
I have bigger issues though. I broke two drill bits before I worked out I needed to use WD40 or something similar as a lubricant when drilling the holes.
And I have now broken a tap into one of the transistor mounting holes...
5680 2011-01-06 06:46:17 w4zcb Re: Copper Plate for QRO FET Your mechanical skills could use some sharpening, you MUST use high
sulphur cutting oil when working in "sticky" copper. Use MANY bolts
between the heat spreader and the heat sink, and pull the two
together until you can see with a straightedge that the spreader IS
flat. (Don't try to make up for it with heat sink compound!)
I used to get my spreader material from Small Parts Inc. Don't know
if they still carry it or not, but it WAS flat.
CCI do not have the copper plate in stock, due to the high prices of
raw material. If they were to re-offer it, they told me it would be
I ordered a 6x8x0.375 inch copper plate from Online Metals and it was
$93. That said, it is cut on a press and has a very slight bow to it.
That is not an issue over the surface area of the transistors, but I'm
concerned that it will not be a tight enough fit to the heatsink.
I have bigger issues though. I broke two drill bits before I worked
out I needed to use WD40 or something similar as a lubricant when
drilling the holes.
And I have now broken a tap into one of the transistor mounting
5681 2011-01-06 08:05:05 g0kla Re: Copper Plate for QRO FET Yes agree 5682 2011-01-06 08:19:11 William Carver Re: Copper Plate for QRO FET Copper is nasty, "grabby" stuff to drill and especially tap. Harold's a
better machinist than I am, but for what it's worth I use "TAP MAGIC"
and haven't lost any taps in copper lately.
This probably sounds nuts at first, but I tap with a little Black and
Decker reversible drill that has variable speed on the trigger. I don't
cinch down on the chuck key, so the tap will slip if the torque gets too
high. The main advantage, and I confirmed my thinking with a
professional machinist, is that using the electric drill lets me
concentrate on staying perpendicular to the surface so I don't put a lot
of bending stress on the tap at it goes in. It also is more
"effortless", so I'm less inclined to go "just one more turn" before
reversing the tap and cleaning the chips from the threads.
But have to admit, when I first started tapping with the drill I was a
little scared because I, too, have broken taps off in a half-finished
piece. In copper I tend to go very slowly, few turns at a time, blowing
out the hole, cleaning and dipping the tap in Tap Magic each time.
On Thu, 2011-01-06 at 16:05 +0000, g0kla wrote:
> Yes agree
5683 2011-01-06 08:25:53 bobtbobbo Re: Copper Plate for QRO FET Before tapping the holes in my copper heat spreader I inquired at a machine shop as to cutting oil and the machinist said that plain old Liquid Wrench would work just fine for that, which it did. Remember the basics: keep the tap perpendicular to the plate, turn slowly and when it gets a little tight, back out the tap, clean the hole of chips, apply a little more liquid Wrench and start with the tap again.
5684 2011-01-06 09:25:42 w4zcb Re: Copper Plate for QRO FET Try Harveys thread cutting oil, 8 Oz bottle from Ace hardware
The only cure for your broken tap is to remove it and any burr, and
move the board and transistors a quarter inch and start over. GO
----- Original Message -----
5687 2011-01-06 15:54:57 kb1gmx Re: Copper Plate for QRO FET I used to tap stainless (308, 316l and friends) that way.
I also have a tap reverser for the drill press. My drill press is a cheapie modded with a variable speed 1/5hp DC motor so real slow with torque is easy and the tap reverser is a gadget that you mount the tap and then mout it in the DP. When you put down weight on it it rotates in and when you relax the weight, it reverses. Very handy and makes tapping a lot of holes much easier.
tap magic is the stuff. I also use kerosene, candle was and
good old motor oil depending on the material.
5690 2011-01-06 17:50:01 William Carver Re: Copper Plate for QRO FET Ooooh. I'd give my left........ no, let me rephrase that. "I'd love to
have one of those Tapmatics!"
On Thu, 2011-01-06 at 23:54 +0000, kb1gmx wrote:
5691 2011-01-06 19:42:01 kb1gmx Re: Copper Plate for QRO FET Look at it this way..
nearly 40years in the electronics industry, part of doing work that
had high mechanical content (upper uhf used to be milled from a block of aluminum). Worked with a lot of machinists, a few were artisans
with metals. So when one of those guys said get xxx I did, and
bowed graciously to them. I Learned a lot practical how to from
Mine is not a tapmatic, it's a clone bought 30 years ago and paid
$80 then. Worth every cent along with the dial calipers and dial guages. First time I used it was in a Bridgeport vertical mill
to tap 55 holes for 4-40 and some 2-56. Interdigital filter for 460mhz, now we do that
5695 2011-01-07 12:46:37 w1kilofoxtrot Re: Copper Plate for QRO FET Last spring I got a 2" x 3" x .25 piece of cooper from an ebay seller for $2, plus shipping. Great heat spreader for a small amp I'm building. Write me off list, and I'll send you his email. At that time, he said he had lots of smaller pieces that were not worth listing, because of the shipping expense. He might still have off cuts that would work for our kind of projects...