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
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod