Hi Michael,

Our SMD equipment is made by an outfit called Zephyrtronics. (www.zeph.com). Our setup includes a pneumatic solder paste syringe (we tried manual, but it was just too unreliable). This allows a measured drop of solder paste to be applied, as well as continuous stripes. We also have a vacuum tool to pick up the small parts, much easier and faster than tweezers.

Once the board is pasted and parts have been put in place, the board is placed above a small box that blows 150F air to the underside of the board to preheat it. When the board is at temperature, you can see the solderpaste change appearance as the flux melts. Then get out the hot air pencil (this is definitely not suitable for stripping paint!). A little very hot air and the solder melts. When you get the hang of it you can quickly solder down those difficult parts and the surface tension of the melted solder will cause the parts to align on their pads. Really cool to see!

Rework is also easy. Preheat the board, apply flux, then resolder the part with some low temperature solder (this stuff melts at a much lower temp than regular 63/37). The part can be easily picked up off the board. Solder braid will clean up the excess solder and you have a clean board for a new part. (SO much easier than the rework article that was referenced previously...)

Dennis