Solder paste is used to create a desired pattern on a printed circuit board. It's often used via screen-printing processes, dispensed pneumatically or by “pin transfer” where a grid of pins dipped in solder paste is touched to the board. Some devices use a jet printing process where the paste is sprayed on the substrate through nozzles. It's critical that the operation is accurate and consistent and capable of functioning in tight quarters. Now Peter Jansen, a 3D printing researcher and electronics expert, has built an open source solder paste extruder to handle the job. You can read the whole story here: http://3dprint.com/53642/solder-paste-extruder/


Below is a photo of Jansen's setup: