A solder bump is stenciled onto a substrate, providing bumped substrate at pitches below 400 microns. The solder is applied through stencil/mask and paste method; the mask, however, remains attached to the substrate during reflow. Pitches of greater than 400 microns may also be obtained through the...http://www.google.com.au/patents/US5672542?utm_source=gb-gplus-sharePatent US5672542 - Method of making solder balls by contained paste deposition
