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Old 03-03-2010, 08:42 PM   #3055 (permalink)
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Originally Posted by chapper View Post
The lower drawing (The Off-Road Controller) shows the same configuration, but it’s held together with anodized aluminum clamps for true electrical isolation and equalized surface clamping forces. It avoids screw threads abrading their tapped holes and potentially contacting different voltages. (In the upper drawing, note the 3 screws holding the buss bars to the heatsink. What happens if…?)

Silver plate the buss bars and PCB with “Cool-Amp” Conducto-Lube Co.
Between the MosFETs, diodes and buss bars use an electrically and thermally conductive compound like “Conducto-Lube”. Conducto-Lube Co.
Between the circuit board copper and the buss bars, use an electrically conductive compound like “Conducto-Lube”
Between the buss bars, and the aluminum heatsink, use a thermally conductive compound like: Aavid “Ultra Stick”
All anodizing is Type III
- The silver plating might help reduce any galvanic corrosion that might occur between two metals that are far apart on the activity scale but the coating has to be very, very smooth (almost like a mirror). Any change in the surface roughness of the surface can significantly affect its ability to transfer heat. It can prevent the oxidation of copper surfaces exposed to air. But, if that surface is exposed to air, it's not touching the other surface it need to in order the transfer heat or current.
- Is Conducto-Lube rated for the current density you're looking at (amps/cm-squared or similar)?
- How does the electrical conductivity of Conducto-Lube compare to that of copper itself? Might more pressure along the metal-to-metal interface be better than using Conducto-Lube? I don't know, just thinking out loud.
- Could the bus bars be made of aluminum? Well, they can, of course, but is it worth it? Then selectively plating the heat sink can allow it to be both the bus bar and heat sink. It's then easier to assemble and the heat-shedding efficiency goes up.
John M.
CamLight Systems
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