I'm working with Proteus and I'll be needing an IC which has packaging TO-99. This package is not available in ARES. I don't quite understand the data sheet of this package to make it, though I saw a few tutorials on Youtube. How to make out which type of hole is there and all. i.e, which one needs a pad and which doesn't. I'm not able to visualize it and that is what is creating the problem. Can someone throw some Light on this?

  • \$\begingroup\$ Leads which should make electrical connection get a pad, protrusions which should not simply get a hole. \$\endgroup\$ – Chris Stratton Jul 5 '13 at 17:37

I see no reason to suspect that any of the pins are not electrical contacts which deserve a pad, though the connection diagram might show that some of them are unconnected.

The drawing you link shows that the radius of the pin circle is .100 inches.

It also shows that the diamter of the housing is .370 inches, not counting the orientation tab.

While not very clear in presentation, the leads seem to be between .016 and .021 inches in diameter - they seem to show two numbers, one with tighter tolerance close to the package and one with looser further out.

  • \$\begingroup\$ The housing is the metal can which sits above the circuit board and protects/shields the internals and lead frame. How to make it would be the same as any of tutorials you found for your PCB package. If you can't figure out how to specify a circle of pins, use basic trigonometry to manually calculate their coordinates, +/- from the center of the package which you'd likely want to use as the footprint origin. \$\endgroup\$ – Chris Stratton Jul 5 '13 at 17:49
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    \$\begingroup\$ theoreticalmachinist.com/BoltCircleCalc \$\endgroup\$ – Chris Stratton Jul 5 '13 at 17:51
  • \$\begingroup\$ You can probably get away with only making the 8 through hole pads, but drawing the housing outline with its tab on your silkscreen and housing or keepout layers will help avoid making mistakes such as putting another component too close. BTW, anyone doing PCB design should get a pair of cheap inch/metric digital calipers - sometimes those and the actual component will save you from misinterpretation mistakes. \$\endgroup\$ – Chris Stratton Jul 5 '13 at 17:55
  • \$\begingroup\$ No. .021 is the upper bound of diameter for the lead, not its radius. You will need to specify the hole as larger than that, both to provide clearance and as the plating process may reduce the finished diameter below specified, by an amount which the board house can tell you. Probably if you made the hole twice as big by mistaking diameter for radius it would work with hand soldering, but might be a bit too loose a fit for reliable mass production. \$\endgroup\$ – Chris Stratton Jul 5 '13 at 18:02
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    \$\begingroup\$ I would probalby make the holes .035 diameter -may be larger than needed, but that size also suits 1/4w resistors, and lots of other parts -I try to minimize the number of different hole sizes. I would make the pad diameter .050 or .060. I would definitely put the package outline with orientation tab on the silkscreen layer. \$\endgroup\$ – Peter Bennett Jul 5 '13 at 18:10

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