I wonder whether silicone pads like Sil-pad have aging problem and also whether it can be reused. What I meant reuse is if you remove the transistor and put in the new one, do you have to change to a new one.
I know you need silicone grease when using mica, grease dry up after a while and you have to redo it after many years. Does silicone pad have this drying up problem?
I know you need silicone grease when using mica, grease dry up after a while and you have to redo it after many years. Does silicone pad have this drying up problem?
most, or maybe all, sil-pads need to be replaced after a first removal.
Grease does not dry up. Some of the volatiles may evaporate, but most remains even after prolonged high temperature.
What is used as the transport medium in the Thermal goops may not be grease. They may use a light oil with a very high proportion of volatiles. These could become "dry looking" but the remaining paste should still exclude air from the interface and thus give prolonged thermal performance.
Thermal paste should be renewed after first removal.
Grease does not dry up. Some of the volatiles may evaporate, but most remains even after prolonged high temperature.
What is used as the transport medium in the Thermal goops may not be grease. They may use a light oil with a very high proportion of volatiles. These could become "dry looking" but the remaining paste should still exclude air from the interface and thus give prolonged thermal performance.
Thermal paste should be renewed after first removal.
I can understand if the sil-pad is screwed on for years, how about during the testing phase where you take the board on and off a few times, it would be too expensive to change the sil pad.
I searched and posted side by side comparation, which by the way showed mica + grease to still be better than the better silpads (they are not the same) by some 30/40% but don´t remember where I saved the data.
But it must have been either here or at MEF with a very distant third possibility at SS Guitar, so if interested do a search and it should appear.
Or compare data at the silpad site to standard mica grease yourself .
But it must have been either here or at MEF with a very distant third possibility at SS Guitar, so if interested do a search and it should appear.
Or compare data at the silpad site to standard mica grease yourself .
Plenty - its an evergreen topic here and on many forums. Google is your friend for the hundreds of articles on the web.
This article covers the whole cooling subject in enough detail to make a wise choice of insulators for audio and most DIY applications: ESP - Heatsink design and transistor mounting.
This article covers the whole cooling subject in enough detail to make a wise choice of insulators for audio and most DIY applications: ESP - Heatsink design and transistor mounting.
From the article Ian provided, the table of comparison of mica, sil-pad etc. The info on the sil pad seems too high. The Sil-Pad SP600 is 0.35deg/W
Thermal - Pads, Sheets | Fans, Thermal Management | DigiKey
They have different Sil-Pad, the thermal resistance of SP600 is very low. Lower than mica according to the article from Ian.
Thermal - Pads, Sheets | Fans, Thermal Management | DigiKey
They have different Sil-Pad, the thermal resistance of SP600 is very low. Lower than mica according to the article from Ian.
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"Any thermal resistance data on mica and grease to compare? "
I generally figure around 0.3°C on a TO-3 (correctly applied).
Some sil-pads are lower °C, but those types can be quite expensive. They also can be used by lesser skilled operators.
Re-work and repair can be a costly thing with the one-use pads though.
I caught a repair operator reusing some pads at work (hey, they looked OK, right?).
Our customer returned goods involving a certain failure went down by 85% after this.
We use both sil-pads and mica + grease, depends on the design requirements.
Some pads have internal shields and a drain wire (to reduce capacitance effects).
I generally figure around 0.3°C on a TO-3 (correctly applied).
Some sil-pads are lower °C, but those types can be quite expensive. They also can be used by lesser skilled operators.
Re-work and repair can be a costly thing with the one-use pads though.
I caught a repair operator reusing some pads at work (hey, they looked OK, right?).
Our customer returned goods involving a certain failure went down by 85% after this.
We use both sil-pads and mica + grease, depends on the design requirements.
Some pads have internal shields and a drain wire (to reduce capacitance effects).
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Heatsink runs cooler with silpads
Just look at the thickness of the silpad
Some may be thinner
Kapton is typical 25 micron. I would say that it is less tolerant to imperfect surfaces but if you are serious about heat transfer then dont even consider a silpad
Just look at the thickness of the silpad
An externally hosted image should be here but it was not working when we last tested it.
Some may be thinner
Kapton is typical 25 micron. I would say that it is less tolerant to imperfect surfaces but if you are serious about heat transfer then dont even consider a silpad
Ive used alumina ceramic insulators about a dozen times now. With regular #4 screws and lockwashers. Zero problems, no cracking at all, and measurably, significantly better thermal performance than mica, which is better than silicone (I haven't measured Kapton insulators but theres data online indi ating they don't do much). The deramic filled or foil laminated silicone ones are said to do pretty well (haven't tested). The performance can be important if you're running class A and want to keep the device die temperature safe when the heatsink temperature goes high.
Alumina is a remarkably strong ceramic and not easy to break or crack. It does need to mount on a flat surface, but really, the surface needs to be flat on any heatsink if its going to work decently. Ive just used the as-received surface on black anodized heatsinks.
Alumina is a remarkably strong ceramic and not easy to break or crack. It does need to mount on a flat surface, but really, the surface needs to be flat on any heatsink if its going to work decently. Ive just used the as-received surface on black anodized heatsinks.
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