| Electronics > Projects, Designs, and Technical Stuff |
| TO-71 PCB footprint |
| (1/1) |
| Eamonn Harter:
Hello, I am designing a PCB that will use a TO-71 package component, and am trying to decide on the correct footprint to use for the layout. With pins in a 100mil diameter circle, there isn't much room to use for the pads and plated through-holes. If I had more space, I would probably go with 25mil diameter holes in 40-50mil pads. Should I not be afraid to spread the pins on the TO-71 component and use a wider hole/pad spacing for the PCB? Does anyone know what the standard practice is in designing a PCB that uses TO-71 components? The internet hasn't been much help on this question, and datasheets also avoid the topic. (The specific component in question is an LSK389 dual N-channel JFET from Linear Systems.) |
| T3sl4co1l:
Yes, normally the leads are formed to a larger circle, or to a DIP-6 or 8 pattern. Tim |
| floobydust:
It's a really small part for 6-pins in basically a TO-46 can. You can splay out the pins to a larger circle but patience to install the leads. The part sits up anyhow. See here at the tiny pads if you keep the leads straight (0.1" dia.) verses a bit increased circle to 4mm dia.rad (0.157") This is what I came up with for a LSJ689/LSK489 pcb footprint. I haven't finished pcbs with it but the parts are here. Shown is 1.1mm pad (43thou) with 0.7mm hole (28thou) on 2mm radius, gives about 18thou clearance between pads. |
| Eamonn Harter:
Thank you both for your replies. I like the idea of using a slightly larger circular pattern. I searched on JEDEC for an officially sanctioned footprint, but came up empty handed. I guess for some problems you just need to use common sense. |
| David Hess:
Just like with a TO-92, there is no sanctioned footprint. With a TO-92, the pins are on 0.05" centers so often the outer two holes are placed 0.1" apart and the center hole is offset 0.05" which is common for crimped TO-92 leads anyway. With a TO-71, you could use this arrangement on each side or just make it up as you go along. |
| Navigation |
| Message Index |