Hi Wee Mei,
There are no recommended clearances between pads except those driven by
design with maybe the sole exception being annular ring requirements for
through-hole pads. Even in that instance you are limited only by tolerances.
For example:
1) If your through-hole component is going to be auto-inserted, the
machine that does the insertion will have guidelines for clearances to avoid
crashing the head of the inserter or clincher into the component next to it
(see IPC-2221 Section 8).
2) The proximity of pads to adjacent pads will also determine
whether or not the wave soldering machine will short the pads on the primary
side of the board when the wave soldering is done.
3) The voltage levels in the traces will determine how much spacing
is required in order to prevent flash over or arcing.
4) The manufacturer you choose will have limitations on how fine
line a space they can maintain with their etching process or imaging
process.
Today most shops can do 5 mil lines and 5 mil spaces. (0.127mm for those who
read in millimeters) If you want to use the less expensive shops, give them
more spacing. I use 8mil lines and 8mil spacing, typically, when at all
possible.
5) Access to the pads with test probes may also drive their spacing.
6) Electrical interference or noise could also be a factor in the
spacing between through-hole pads...
There are probably other issues, but I can't think of any at the moment...
But, as far as I know, there are no specific rules that say " a through-hole
pad must be X amount of distance from any other through-hole pad"...
Just make sure the other issues are taken into consideration when spacing
them. It is customary, to use a grid to make holes on some finite spacing if
you can. But it's not 'required'.
Just use good design practice and your designs should be fine.
Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
http://pcbwizards.com
-----Original Message-----
From: Lum Wee Mei [mailto:[log in to unmask]]
Sent: Monday, June 21, 2004 8:29 PM
To: [log in to unmask]
Subject: [DC] clearance between two solder pads
Hello,
Out of curiousity, is there a recommended clearance between two
through-hole solder pads, assuming it is too small to run a trace through.
Thanks and regards,
Wee Mei
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