Hi Gene, It costs me about $80 for a laser cut stencil. The process of applying the paste is shown here.
http://www.homanndesigns.com/index.php?option=com_content&view=article&id=54:manual-process-for-applying-solder-paste-via-a-stencil&catid=35:smt&Itemid=55 It takes less than 90 seconds to apply paste to a panel with this method. I also have a pneumatic paste dispenser that I use for prototypes and also for reworking. The paste in the syringes is a lot less viscous so it can be dispensed through the needle. It is not suitable for use with a stencil as the stencil paste is not suitable for use in a syringe. I did have a plan to make a paste dispenser machine as I have an auger driven paste dispenser heat of an old Camalot machine, along with some nice rails for the X/Y axis. But in the end, the stencil works so well. If I was doing a lot of one-off, it may be a different story. One day I'll make it just to see how well it works. For an automated dispensing machine an auger dispenser is essential as the viscosity of the paste changes with temperature. After about 50 dots from a pneumatic syringe dispenser, the syringe is noticeably warm, thinning out the paste. When using the pneumatic syringe dispenser, I'm continuously adjusting the dispense shot time to keep the dot the size I want. Cheers, Peter On 7/08/2012 4:51 PM, Gene Heskett wrote: > On Tuesday 07 August 2012 02:32:47 cogoman did opine: > >> On 08/06/2012 09:49 PM, Jon Elson wrote: >>> I make my own stencils for these. It is kind of a pain, but I'm >>> CHEAP! >> >> How about the cheapest CNC to build, an XY plotter like this: >> >> https://www.youtube.com/watch?v=WyLPpGdfR7s > > That seems to be pretty sloppy, with pen tilt being a major problem. In > addition to that, a 3rd tension pulling down would reduce the positioning > errors from the sag in the upper support lines. Ok for crayon on the wall > art, but obviously very slow. > >> but with the laser from an old DVD burner for the pen. You could >> produce plotter output files and convert them to G-code, and then cut >> them out of thin plastic (just shield your eyes while it runs, or box it >> in. > > Could one use the resultant laser cut stencil as if it was a silk screen to > apply the solder paste? > > If so, that would certainly cut large hunks of time out of the process once > the stencil was made. However, having the paste exposed to the air while > on the stencil would make me want to figure out a way to flood the area > with GN2 to slow the oxidation that would occur while doing the time > consuming pick-n-place, and on to the reflow oven. All of that should be > in an oxygen free atmosphere to preserve the solder ability. Quality wise > there probably would be a better flooding gas than GN2, but GN2 is > relatively cheap. > > >> Getting the tool set in line would take some time, but once you get >> the hang of it, it would save time in the long run. >> > > > Cheers, Gene > -- ----------------------------------------------------------------------------- eStore: http://www.homanndesigns.com/store Web : http://www.homanndesigns.com ModIO - Modbus Interface Unit email : [email protected] DigiSpeed - Isolated 10Vdc I/F Phone : +61 421 601 665 TurboTaig - Taig Mill Upgrade board ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
