RE: RE:heatsink flexing
Posted by
ballendo@y...
on 2000-10-06 14:04:56 UTC
Kevin,
Thank you for the reply. Good thoughts, all. More comments follow.
Have you seen Camtronics Heat sinks? They're HUGE!! And top-heavy."T-
shaped".
Of course, it also depends what we're attaching the H/S to. A 20 pin
DIP could have a BIG flat h/s with NO problem. Put the same thing on
a TO-220(type of pkg,black plastic w/3 "legs" and a screw "tab" at
the top, for those who don't know already) and you've got problems.
You are exactly right re: the bent leads/mounting distance.
Sockets(quality) are fine for most components, but I wouldn't
recommend their use for power output devices. You need GOOD, SOLID
contact here! Ask Dan Mauch the number of failed/ (temporarily)
malfunctioning boards due to poor soldering of the output transistors
or L298's!
Sockets used with T0-3 pkg would be an exception. (This one is shaped
like an exhaust gasket, Big circle in the middle, small holes to
mount on each side, 2 leads sticking out the bottom, with enough
metal to hold it all togther, again, for those who don't know all
these confusin' numbers Ballendo's talkin' 'bout.)
Many of the DIP style driver chips use the center pins as a heat sink
and recommend large areas of copper to assist this function. A socket
here would also be inappropriate.
Your "rule of thumb"(fingers??) is interesting. I would add that you
need to also consider vibration. Many "desktop" CNC's (and some
larger,too)have the control mounted where tool/cutting vibration is
transferred to the PC bd/heat sink(s). And we know, even small
amplitude,cyclic vibration is a bad thing for the electronics, as
well as the obvious effect on a "free" heat sink.
Ballendo
Thank you for the reply. Good thoughts, all. More comments follow.
Have you seen Camtronics Heat sinks? They're HUGE!! And top-heavy."T-
shaped".
Of course, it also depends what we're attaching the H/S to. A 20 pin
DIP could have a BIG flat h/s with NO problem. Put the same thing on
a TO-220(type of pkg,black plastic w/3 "legs" and a screw "tab" at
the top, for those who don't know already) and you've got problems.
You are exactly right re: the bent leads/mounting distance.
Sockets(quality) are fine for most components, but I wouldn't
recommend their use for power output devices. You need GOOD, SOLID
contact here! Ask Dan Mauch the number of failed/ (temporarily)
malfunctioning boards due to poor soldering of the output transistors
or L298's!
Sockets used with T0-3 pkg would be an exception. (This one is shaped
like an exhaust gasket, Big circle in the middle, small holes to
mount on each side, 2 leads sticking out the bottom, with enough
metal to hold it all togther, again, for those who don't know all
these confusin' numbers Ballendo's talkin' 'bout.)
Many of the DIP style driver chips use the center pins as a heat sink
and recommend large areas of copper to assist this function. A socket
here would also be inappropriate.
Your "rule of thumb"(fingers??) is interesting. I would add that you
need to also consider vibration. Many "desktop" CNC's (and some
larger,too)have the control mounted where tool/cutting vibration is
transferred to the PC bd/heat sink(s). And we know, even small
amplitude,cyclic vibration is a bad thing for the electronics, as
well as the obvious effect on a "free" heat sink.
Ballendo