On Tue, Mar 2, 2010 at 1:25 AM, Donald Tillman <[1]...@till.com> wrote:
On Feb 27, 2010, at 3:57 PM, John Luciani wrote: I use two different footprints. Both footprints have the pins inline. One footprint spaces the leads 1.39mm the other 2.60mm. The 2.60mm is the common formed lead pattern. I believe I used the spec from On-Semi. I use a finished hole size of 29mils. The fab tolerance is +-4mils. Hey John, Thanks for that. Researching this a little more... Fairchild's TO-92 spec says that the leads are rectangular, 0.46mm by 0.38mm, and the diagonal there works out to 23.5 mils. With a little extra room for tolerance, yeah, a 29 mil hole sounds good. But with 29 mil holes spaced 50 mils apart, that doesn't leave enough room for the pads and the space between. Maybe 7 mils each. So breaking away from the 50 mil grid by just a little bit and moving the outer legs 5 mils beyond allows the DRC to work. I use 1.39mm for the non-formed leads (apx 55mils). (* jcl *) -- You can't create open hardware with closed EDA tools. twitter: [2]http://twitter.com/jluciani blog: [3]http://www.luciani.org References 1. mailto:d...@till.com 2. http://twitter.com/jluciani 3. http://www.luciani.org/
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