I recently bought a hockey-puck SCR, without realising it needs to be clamped to a heatsink. I'm trying to decide whether to return it or whether to build a mount.
The SCR in question is an Internation Rectifier 250PA140, specs pasted at the end of this topic.
First of all, I haven't managed to find any information about how much force you need to clamp these things with. I'm assuming 2 metal plates with 3x6mm bolts should be ample.
Secondly, do I need to apply force or displacement? For example, if I need to apply exactly 1mm of displacement to the plates of the puck, then the puck contracts by 0.1mm this might be a disaster, unless there is some kind of springy contact inside that will take up the slack. Perhaps I should use some kind of springy bar to apply a constant pressure despite changes in temperature etc...
Thirdly, I presume that too much force will break the die, and too little will mean the contact has insufficient area for the device to function properly? How can I know when I've tightened the clamp the right amount?
Finally, I understand there is meant to be a snubber resistor between the gate and the cathode. But I get very low resistances of < 0.1 ohm and I wonder whether this implies it is broken?
If I(GT) Max. is 150m and the parallel resistance is < 0.1 ohms then as I see it the voltage can't rise high enough to cause the device to trigger - I'm assuming it needs at least a diode drop.
Thanks in advance for any help.
KV(DRM) Max.(V)Rep.Pk.Off Volt.=1.4k I(T) Max.(A) On-state Current=250? @Temp. (?C) (Test Condition)=70 I(TSM) Max. (A)=4.2k I(GT) Max. (A)=150m V(GT) Max.(V)=2.5 I(H) Max.(A) Holding Current=500m I(D) Max. (A) Leakage Current=11m @Temp. (?C) (Test Condition)=125 V(T) Max. (V)=2.3 @I(T) (A) (Test Condition)=250 dv/dt Min. (V/us)=200 t(q) Typ. (s)=60u Package=TO-200AB