I do not want to start a flame war, since I am relatively new here but I have to comment ...
On Sun, 2008-10-26 at 20:47 +0100, Stefan Salewski wrote: > Am Sonntag, den 26.10.2008, 14:25 -0500 schrieb Kipton Moravec: > > > > There are huge differences in the size of these footprints! > > Please note, some are metric, see > > http://archives.seul.org/geda/user/Sep-2008/msg00312.html > Why in gods name would some one call a footprint 0603 when it is really an 0201. Nobody uses a metric name for resistors or capacitors. You folks are asking for trouble. > > > > First of all why so many? When would you use one versus another? > > > > We may need more than one -- hand, wave, reflow soldering... > If you do some search in Internet you will find many different size > recommendations. I do not buy that. Everything I build is designed for machine placement and solder, and so a human can perform touch-up if necessary, but my assembly shop decides how they will build it. If it is a small order they may hand build it. If it is more then they will use the pick-and-place machine. Everyone should design for the machine. Same is true for through hole. You build your footprints so a machine can stuff it. If there is not enough volume to use a machine, it cam be hand placed. But if you design your footprints for only hand placement, then a machine can never place it. Bad idea. Also assume it will be wave soldered for the same reason. I worked at an assembly shop for awhile, so I would better understand the assembly process, and I could design for manufacturability. I was amazed at how bad some boards were layed out and how difficult they were to inspect, and they were doing production in the thousands! The biggest problem nowadays is that the designers do not follow the board through production in most places. They need to know the whole process from design to placing in the customers hands. You have one guy design the schematic, another person lay it out, another person purchase the parts, another person assemble the board and another person inspect the board, and another person test it. And they do not talk to each other. I design boards so they can be built. I design boards so they can be inspected. I design boards so they can be tested. I design boards with parts that are in stock or do not have long lead times (> 4 weeks). My customers want me to design a board, and provide them finished product at a certain rate per month. If I make it easy for the assembly house to build, they can assemble it cheaper, with less errors, and we all make more money. You design it one time, but build it many many times. Make it easy to build, even if it takes a little longer in the design. Kip -- Kipton Moravec AE5IB "Always do right; this will gratify some people and astonish the rest." --Mark Twain _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
