At 09:43 AM 1/25/2002 -0800, Afshin Salehi wrote: >I have a question that has had me thinking every so often. When the >autorouter connects traces to small smt pads of IC's it never goes straight >into the pad. Instead it will go along the side of the pad and then turn >left or right and into the pad. This looks like a potential problem to me, >and on top of that it just looks cheesy! :) I am not sure what the most >efficient method would be to solve this problem (hint, hint).
It is a quality issue from two points of view. One is that it often causes pockets to be formed, i.e., included angles of less than 90 degrees, which traditional wisdom says can trap etchant, causing possible trace failure even a long time later. The other is cosmetic, which is important when you are making your living designing boards. I remember, many years ago, when I was prone to make very curvy traces instead of sticking to 45 degree angles for bends, an engineering manager nixed my work because it was "messy." (This was manual tape, and "messy" was a value judgement: a board had been designed with very high density made more possible because the traces packed in a curved manner; but he was used to everything being nice and orthagonal.) On the other hand, changes on that board would have been a bit of a nuisance, one would simply have ripped up all the routing. It *might* have been easier to make changes if the track had run on-grid in an orthagonal manner. In any case, I went to cut-and-bend with tape shortly thereafter and films of my layouts looked like they had been done with CAD unless you looked *very* closely (the 45 degree corners were very slightly rounded). Anyway, to the present point. The autorouter cleanup routines are almost brain-dead, there is no excuse, really, for the state in which it leaves layouts. It is a *lot* more difficult to do what they have already done -- autoroute a board with moderately good completion -- than to clean up meandering segments, since the latter process can be done very locally, one layer at a time, with one trace at a time. Simply eliminating segments and determining if the resulting new trace causes clearance violations would vastly improve routing appearance. (There is no requirement that the last segment of a trace be orthagonal or semi-orthagonal, it may be any-angle unless it is long.) To clean up traces manually, be sure to have Loop Removal and snap on. (tools/Preferences/Options/Automatically_Remove_Loops) You can then simply draw over the traces, very quickly, and the original segments will usually disappear. (With a little practice, you will learn how to drive this loop removal feature so that it almost always does what you want.) Loop Removal is the manual router's friend! [EMAIL PROTECTED] Abdulrahman Lomax Easthampton, Massachusetts USA * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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://email@example.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *