If this is a product, I advise against your idea. If it is an in-house project that will only be used in controlled conditions, it will probably work - for a while.
Shorts through the solder mask are unlikely; however, some of the problems I see are: - The package will have uneven stresses on the leads unless the same geometry of leads is used on each side. - Fewer soldered pins means less physical strength between chip and board. Vibration, temperature cycles, etc. become more of a concern for possible solder joint failure at the pins. - Because the surface of the solder mask is above pad level in most cases, the unused leads will be stressed upward (or the soldered leads will not be down flush against the pad when soldered. If you run a trace under solder mask, under an unused pin, the upward distortion of the unconnected pin will be even more exaggerated. - Unused pins are not always "unused". Sometimes they are connected to the substrate, and should be returned to Vcc, Vee, or Vdd. It depends on the chip technology in use. I'm always wary of floating chip bond-outs. In my view, for anything except a quick-and-dirty in-house project, this is a bad idea. At 06:13 PM 6/7/02 -0700, you wrote: >i've got a 144 pin PQFP 0.5mm pitch >there are only a small number of connected pins, maybe a dozen or so >excluding power > >i am thinking about deleting a lot of unused pads to possibly open up >top side routes and reduce inspection and bridging concerns > >am i crazy? >do you think the leads will short thru the solder mask to traces below? > >is this good practice even if i don't run traces there, i.e. will it >solder and align properly with missing pads? snip * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
