Potted with glass?

[baconsteak]

Took apart a cdi the other day it was potted with some sort of rubber mixed with ground up glass. Anyone know why the glass? Its a high vibration environment (dirt bike).

Thanks.

[Lightages]

I would hazard to guess they use whatever cheap industrial waste they can get their hands on for filler instead of using just the expensive potting material.

[theatrus]

You do see epoxy or plastics with glass filler material, but those are microspheres and not cheap.

Have a picture?

[sleemanj]

Took apart a cdi the other day it was potted with some sort of rubber mixed with ground up glass. Anyone know why the glass? Its a high vibration environment (dirt bike).

My guess;

http://upload.wikimedia.org/wikipedia/commons/1/1e/Thermal_conductivity.svg

[baconsteak]

Sorry no pic its at my mates. The glass was maybe 2-3mm in diameter. The thermal thing sounds plausible though. It had no heat sinking anywhere. I was gonna try changing the scr. Some nec part with no datasheet to be found on the net. Was a job just to get at big parts. The whole underside was covered with smd parts. Whatever glue they were using was good. Decided it wasn't worth it for $150.

[SeanB]

Glass microspheres, used as they are hollow and thus reduce the mass of filler needed and make the part lighter as well. Common in the fibreglass industry and in boat building to mix in with resin to make light but strong resin castings. Makes a much lower density composite which is still as strong and waterproof as the original resin. If they wanted to only bulk it up they would use ground glass, like that used in car body filler, as this makes it more bulky and allows it to be shaped afterwards by sanding and filing.