At 01:55 PM 2/27/2002 -0500, Mike Reagan wrote: >[I wrote] > > > (2) The ability to truly flip a design or design section for re-use in a > > new design which might predominantly be oriented bottom-up from the point > > of view of the first design. > > >I've read all the threads about wanting to view a board from the bottom up >and I cant figure out why anyone would do this.
I think I explained it, but it was a bit densely stated. I'll dilate it a bit. Suppose, I have designed a little piece of RF circuitry on the top of a PCB, including vias to layers just below, and this has been used successfully, tested, etc. Now I have another design where I would like to use this same circuitry, only I need to place it on the bottom. The rest of the design is on the top. > The IPC -D-325 >Documentation standard states in sec 4.2.6 VIEWING : The layout of >the board design should always viewed from the primary side of the board. "Primary" side of the board gets a tad arbitrary with SMT designs with components on both sides. Sometimes there are even through-hole components on both sides. Yes. But we are not talking about "documentation" of the "layout," but rather the layout itself, for one, where we might need to merge designs, flipping some of them and not others, plus, in documentation, we are talking about assembly drawings. Assembly drawings are traditionally done as viewed from the side being assembled. >blah blah blah.. I have hit mechanical engineers and anyone else who >wanted to view it otherwise on the head with a sledge hammer until the >morons got it right. Tsk, tsk. I'd be a moron too if I were being regularly hit over the head with a sledgehammer. > Why did I use a sledge hammer you ask? Because the >only designs that ever came back with backward connectors and parts were >the freaking ones they wanted flipped. Since they got my message that I >wouldn't flip boards anymore, we have not had one design come back flipped. >It was almost a regular occurrence because we had a mech engineer who >couldn't grasps the concept of a primary side, I have even seen BGAs, >and earlier days PGAs flipped because someone thought it was a good idea to >look at from the bottom. I remember one layout where I was using a DIP relay and the only description I had of the relay was a catalog photo of it; the relay had a drawing pasted on top showing the pinout. Naturally, much to my chagrin, it was a bottom view. When I got the actual relay, there was even a tiny piece of text, not readable in the catalog, which said "pin view" or something like that. Yes, I understand Mr. Reagan's concern. But I'd make an exception for *bottom assembly drawings," which are not used for fab but for assembly reference. One should be able to easily look at the drawing and at the physical board and say, yes, they put that diode in correctly. If that is easy for Mr. Reagan, my congratulations on his profound sense of spatial relations, with which I am fairly good, but not that good. And I think that most people are like me. I can read mirrored text without much difficulty, but determining orientations can get a tad dicey. I end up saying to myself "the cathode end will be near the IC" or something like that, so that I don't have to depend on "left" or "right." Which get reversed in a mirror view, unless it is rotated. > The advantage of the way the software flips it >now is, you know it wrong when you look at it because the text becomes >backward. Yes I said the view was wrong. I really do not want this >feature, I know some of you mechanical types do but I don't. You can flip >right now in the x axis or y axis, neither of which is an acceptable method >of documenting a design. The board must be viewed from the primary side >looking thu the board. (Actually ) I am going thru this same scenario right >now with a chassis because some mech bozo doesn't know up from down. Stick >to the standards and everyone is on the same page I don't think the standards conflict with what I am saying, but I could not find my copies at the moment.... In any case, bottom view assembly drawings are very common. Techserv does them, for example (or did,as I recall, last time I saw one of their assembly drawings). How does Mr. Reagan propose doing a bottom assembly drawing where there are components on both sides? Especially if, as would be normal, there is only *one* assembly drawing for the board? [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://firstname.lastname@example.org * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *