Silcon pads - re use

[Synchro-bias]

I am concerned after reading that you cant re use Silicon pads.

I used re used them after i cleaned my V9 on the Sanken output transistors - i made sure i put them back tighly - amp never gets hot but with the V9 I dont really take it past 2 usually - it gets warm after a long use, but never hot no sign of heat stress on the pcb

The thyristor pads were on very tight and left an imprint on the Silicon pad - which is still present - also screw hole or break in one of them

I have a few MT200 mica washes around( brand new) and - 4 year old abouts Wakefield 120 paste.
If needed I could re use the MT200 and get if needed washers for TO-220 - have to use a wash between metal heatsink?

 

[NAD80]

Have to be careful with the torque on the screws. Too tight and the pad can tear and if anything foreign is stuck on either side of the pad can puncture the pad shorting out the device to the chassis. Use the Berquist Sil-Pads at work. Easy to damage them if too tight. Shows up on Hypot testing as a failure to chassis.

 

[NAD80]

Used a torque driver set to 2ft/lbs of torque.

 

[Synchro-bias]

Thanks Nad80, so i can still re use the old then? I didnt get any in my MOuser Order

 

[Synchro-bias]

I got Mouser to add on the Silica pads to my order, which is great
951-SPK4-0.006-00-58 - spare for Sanken output transistors - looks approx size
951-SP900S-009-00105 - thyristors

 

[ConradH]

The manufacturers tell you not to reuse them, though I sometimes do. Torque on semiconductors is a big issue and many people get it wrong. The hardware should never be very tight. That risks warping the device and actually cracking the internal silicon die. The instructions are somewhat generic, so download various recommendations and pay attention to the torque. If you don't have a calibrated driver, at least understand that 8 inch-ounces would be 8 ounces applied at 1 inch out. Or it could be 1 ounce applied at 8 inches. Or any equal product. That should give you a rough feel for it.

 

[Synchro-bias]

Used a torque driver set to 2ft/lbs of torque.

Thanks Nad80, they look good the Berquist Sil-Pads. I dont have a torque driver set so will not over tighen so much, or maybe i can see if my brother has a torque driver

 

[Synchro-bias]

The manufacturers tell you not to reuse them, though I sometimes do. Torque on semiconductors is a big issue and many people get it wrong. The hardware should never be very tight. That risks warping the device and actually cracking the internal silicon die. The instructions are somewhat generic, so download various recommendations and pay attention to the torque. If you don't have a calibrated driver, at least understand that 8 inch-ounces would be 8 ounces applied at 1 inch out. Or it could be 1 ounce applied at 8 inches. Or any equal product. That should give you a rough feel for it.

Hello Conrad,
Thank you. I will leave the re used silipads on the heatsink output transistors ( not very tight) but since the silipad isa bit broken thyristor pads i just got new ones. I hope the factory didnt have them like that they were super tight. I will carefully do it and see if any friends have such a product , hopefully Berquist will have information or can ask them about the specific part. I can practice on the old ones - also i forgot to note but there was a bit of silipad rubber left on the heatsink - hence mustve been on tight

I am you are felling better
I got the FM/FC coming for the amp and tuners

 

[Synchro-bias]

The re used V9 silica pads and it never gets hot the heatsink though i never exceed 2 on the volume dial. My conern is i have them very tightly screwed on. I do have spare Mica washers and thermal grease for the Sankens. ( i have since moved the bit of solder near one of the sankens