Overview:

The Disso Pad Placement cell places dissolvable spacers onto printed circuit assembly for precision military PCBAs. The system is comprised of a Seiko RT3000 cylindrical robot, a series of bowl feeders, a PCBA fixture and a dispensing/placement head.

Process Description:

Dissolvable spacers are temporarily adhered to the PCBA using a water soluble solder stop. The spacers are presented to the system in bowl feeders. A dispensing/placement head picks the approriate spacer from the feeder, deposits a dot of solder stop on the PCBA, and then places the spacer onto the dot.  The process continues until all of the spacers are in place.

Technical Challenge:

To be effective, the dissolvable spacers need to be placed abutting one another in some cases. As the parts and process were not inherently accurate enough to allow the parts to be placed that closely, the development team considered a number of mechanical solutions to the problem, including a centering mechanisms on the vacuum grippers and pre-alignment devices on the feeders. However, and "all software" solution was implemented which used a horizontal approach to the final pad target to nest the pads.  The pad would "swoop" into position approximately 1 mm above the target substrate, and then finish with a straight vertical move into position. The swoop direction could be controlled within the program so that any pattern that provided at least one open face could be created.