This invention relates to solder bumps in general and particularly to a method for making high density solder bumps and for providing a socket on a substrate for receiving a solder bumped member. The use of solder bumps on a substrate for attachment to a second substrate by a reflow process is well known in the art. Solder bumps are particularly useful with pad grid array substrates. The closeness or density of solder pads is limited using known technologies due to problems in providing high density solder bumps and preventing the solder bumps from flowing together and shorting pads and bumps when reflowed. One approach for providing solder bumps involves using a stencil process where a stencil is placed over the substrate and solder paste is applied to the substrate through the stencil as by using a squeegee. With this approach the density is limited due to the slumping of the solder paste when the stencil is removed.
Another approach involves the use of solder balls which are precisely placed on a substrate. The placing of solder balls is time consuming and can present reliability problems. If a single ball is misplaced, the proper soldering to the substrate will not be accomplished.
USPTO Backgrounds
USPTO Backgrounds