Gene Heskett wrote: > I would add that temporary storage of the > pasted board should be in an oxygen-free environment until the board comes > out to goto the pick-n-place station, then back into the same low oxygen > box while the reflow oven is warming up. > I normally get my boards from the paste application to the P&P and into the oven in 10 minutes or so. But, sometimes when I got interrupted, I have let them sit for several hours with no problem at all. > > That seems like a needless method then, because it would take far more time > to do a board dot by dot than by the stencil method. Yes, when everything it working right, it takes me more like 10 seconds to apply paste to a small board. Lift stencil, drop board into fixture, lower stencil, wipe paste in with metal blade, lift stencil and remove board. I have to get pictures of my super-simple fixture for this. An aluminum plate with a grid of tapped holes, and bars with a step on one edge that are clamped to hold the board. Stencil is attached with a piece of masking tape to form a hinge. > I wouldn't fix what > isn't broken. :) Except of course for one-offs while developing the next > design. For that, I'd be tempted to try putting the dispenser head on an > XY plotter and stripping the locations to paste out of the eagle (or > whatever you use) files so that is largely automated. For first article boards, I just do the whole board by hand. Even if the stencil was produced at the push of a button, I'd still have to set up the P&P machine, which is time consuming. I have to find all the parts, put them on feeders and put the feeders in the right spot. Programming is nearly automatic, I wrote a program that gets the part and placement info from the CAD package and writes the file for the P&P machine.
And, the WHOLE job of the solder flux is to take care of the oxidation problem! Jon ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
