On Mon, May 23, 2011 at 2:16 PM, V G wrote: > On Mon, May 23, 2011 at 3:43 PM, Denny Esterline >wrote: > > > About a million things :-) > > I would suggest that you start with the understanding that the "perfect= " > > design is impossible, then work to "functional". > > > > There would be lots of ways to make it functional, but I would like to sa= ve > a few square inches on the board, it would save quite a bit of money. Als= o, > I'm gonna be using these guys: http://www.pcbgeek.com/ and they have a > 7x7" > restriction. I'd still like to use surface mount parts, mostly. > > > > First, I see a classic newbie mistake - no mounting holes. > > > > My mistake. Thanks for pointing that out. > > > > You said the autorouter does it "fine", why is that not an acceptable > > solution? > > > > It is! I just need to place the components properly. The board will be > operating at low speeds. The microcontroller already has it's own board > (UBW32), and everything else will be running at around 9600 bits/s or les= s > > > > You want to "save as much space as possible" - why? If it physically > > doesn't fit in the mounting location, ok, that's a good reason. If you'= re > > trying to reduce costs on the board, you need to re-evaluate your > motives. > > Saving $5 off the PCB on a total production run of three units, compare= d > to > > the dozen hours or more it takes to lay out a space optimized version m= ay > > not be your best choice. > > > > Difference between 6x6 and 7x7 is 13 sq in. That can mean a $65 differenc= e > if I use Dorkbot, for example. So squeezing everything down a couple of > inches on each dimension would save a lot of money. > > > > Also consider the future - if you were able to shrink this down to a 2" > > square using the tiniest parts available, how convenient would it be to > > assemble or debug? A little extra space at this stage can make your lif= e > a > > lot easier later. > > > > That's true, but I have no intention of going smaller than I can > comfortably > solder by hand. Someone else pointed out that 1206 size surface mount > components are a good choice, so I'll go with those. > -- > Hmmm... don't know about Dorkbot. I tend to use PCBFabExpress for low volum= e and proto work. Just poked on their website, 2 layer 6"x6", 5 day turn time= , three boards $35 ea. vs. 7"x7" $41.67 ea. So about a $20 difference. Not enough to make me redesign, but your economics may figure differently. For my money, 1206 isn't enough smaller than through hole to make it worth doing. SOIC and 0806 are easy enough to deal with. 0604 and TSSOP is doable= , but at least for me, passes the point of being "fun". I've done smaller by hand, but I don't enjoy it. -Denny --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .