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Old 20th November 2011, 02:01 PM   #501
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What a space, what an oppertunity to spread the transistors physically! I'd have tried to give eacch transistor much more Sq/Inch to give each a better buffer for thermal transients.
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Old 20th November 2011, 02:08 PM   #502
AndrewT is offline AndrewT  Scotland
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The pic showing Kapton appears as pink. I thought Kapton was clear.
Is that isolator coated with some other material on one, or both sides?

Thin mica with Thermal compound on both sides is a very good heat conductor. Very few film based insulators can match it's Thermal performance. Choose carefully if you need good Thermal performance. Even fewer film based insulators can improve on thin mica+goop.
Kapton film on it's own is a flat surface that will not conform to the imperfections of the heatsink nor the device. Plain smooth Kapton requires Thermal compound on both faces just like mica.
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Last edited by AndrewT; 20th November 2011 at 02:11 PM.
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Old 20th November 2011, 02:13 PM   #503
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by MagicBox View Post
What a space, what an opportunity to spread the transistors physically!.................a better buffer for thermal transients.
The PCB is done. It fixes the devices in a tight group.
Looks like it is designed for blown tunnel cooling. At the maximum power expected they are more like PA amplifier PCBs, where blown cooling is the norm.
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Last edited by AndrewT; 20th November 2011 at 02:16 PM.
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Old 20th November 2011, 02:16 PM   #504
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Originally Posted by AndrewT View Post
the PCB is done. It fixes the devices in a tight group.
Looks like it is designed for blown tunnel cooling. At the maximum power expected they are more like PA amplifier PCBs, where blown cooling is the norm.
Ah, with active cooling it's less of a concern yes I just didn't get that from the chosen heatsink - if it would have been these high-density fin designs I'd have assumed active cooling.
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Old 20th November 2011, 02:43 PM   #505
AndrewT is offline AndrewT  Scotland
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Your concern is valid.
The PCB is designed for tunnel cooling, if high power must be dissipated.
That tall heatsink is quite unsuited to obtaining good heat dissipation efficiency with the PCB.
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Old 20th November 2011, 02:56 PM   #506
a.wayne is offline a.wayne  United States
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^^^I guess you know this from your last 1kw/ch@1ohm build


Err, ahh i guess you mised the xtra outputs or the 7" tall caps ...... room for the soft start, regulated supply and the 8.5x4 " transformer ..





Last edited by a.wayne; 20th November 2011 at 03:04 PM.
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Old 20th November 2011, 03:06 PM   #507
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Quote:
Originally Posted by AndrewT View Post
The pic showing Kapton appears as pink. I thought Kapton was clear.
Is that isolator coated with some other material on one, or both sides?

Thin mica with Thermal compound on both sides is a very good heat conductor. Very few film based insulators can match it's Thermal performance. Choose carefully if you need good Thermal performance. Even fewer film based insulators can improve on thin mica+goop.
Kapton film on it's own is a flat surface that will not conform to the imperfections of the heatsink nor the device. Plain smooth Kapton requires Thermal compound on both faces just like mica.
Yes Andrew it is coated with a compound on both sides.I do use them very often.
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Old 20th November 2011, 03:10 PM   #508
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Quote:
Originally Posted by AndrewT View Post
Your concern is valid.
The PCB is designed for tunnel cooling, if high power must be dissipated.
That tall heatsink is quite unsuited to obtaining good heat dissipation efficiency with the PCB.
I will use this sink
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Old 20th November 2011, 03:16 PM   #509
Junie is offline Junie  Philippines
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Quote:
Originally Posted by AndrewT View Post
The pic showing Kapton appears as pink. I thought Kapton was clear.
Is that isolator coated with some other material on one, or both sides?

Thin mica with Thermal compound on both sides is a very good heat conductor. Very few film based insulators can match it's Thermal performance. Choose carefully if you need good Thermal performance. Even fewer film based insulators can improve on thin mica+goop.
Kapton film on it's own is a flat surface that will not conform to the imperfections of the heatsink nor the device. Plain smooth Kapton requires Thermal compound on both faces just like mica.
Andrew it's not a Kapton it's a Sil-pads, here's what it says:

Sil-pads come in a few different varieties. The most common is a silicone rubber material reinforced with fiberglass. A different version has 2 thin silicone rubber layers sandwiching a layer of polyimide film. Many manufacturers use sil pads because they don't require grease to perform to spec (which makes assembly quicker and easier).
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Old 20th November 2011, 03:28 PM   #510
a.wayne is offline a.wayne  United States
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Originally Posted by meanman1964 View Post
I will use this sink
Nice setup for fans, fans will not work for me due to the noise, i will have a fan to cool the case if temps escalate , but only for those brief moments. Also i do not like the heat concentration such a setup creates ....

Quote:
Originally Posted by Junie View Post
Andrew it's not a Kapton it's a Sil-pads, here's what it says:

Sil-pads come in a few different varieties. The most common is a silicone rubber material reinforced with fiberglass. A different version has 2 thin silicone rubber layers sandwiching a layer of polyimide film. Many manufacturers use sil pads because they don't require grease to perform to spec (which makes assembly quicker and easier).
Thanks for that tid bit junie ....
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