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Pad or Paste?


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Goodaye all

 

Whats the thinking on using pads or paste on output transistors?

Just finished the driver board on a Sansui AU2900 had a couple of pads missing as well as a lot of parts.

 

In the past l always used paste for CPU's

 

regards Bruce

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Pads or paste and insulating wafers? If you use paste, you will still need to insulate them from the heatsink, via the mica washers. But these days silicone heat transfer sheet/pads are used by most manufacturers, so I would think they would be OK. Probably should get them from a reputable source though, just in case.

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2 hours ago, bob_m_54 said:

But these days silicone heat transfer sheet/pads are used by most manufacturers, so I would think they would be OK. Probably should get them from a reputable source though, just in case.

 

10 minutes ago, mwhouston said:

For me sili pads every time. Or sticky sili pads. 

 

I've used silicone pads (instead of the old-style mica washers) ... but I prefer ceramic pads ... 2mm thick.

 

Andy

 

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The sticky ones are good but you have to be very careful when finaly aligning your power FETs up with the heatsink. I put the stickies on the FTEs with the mounting bolts in. Then as is, keeping the now sticky FETs well back, part screw the bolts in getting closer. With the final align as i push the pads onto the heat sink and systematically tighten the bolts down. Last time i did it this way it worked well, best i have ever done on a Holton build, eight FETs in all. 

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I guess I am old fashioned.   I prefer paste - with mica insulators if needed.

 

The one time I used a silicon pad under a power chip I had troubles with heat.   I see them as good for experiments where you might want to change the devices or heatsinks.

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3 minutes ago, aussievintage said:

 

I guess I am old fashioned.   I prefer paste - with mica insulators if needed.

 

The one time I used a silicon pad under a power chip I had troubles with heat.   I see them as good for experiments where you might want to change the devices or heatsinks.

I used mica a lot but now just the pads. Hard to know which has lower thermal resistance. Its probably stated somewhere. 

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