Method and apparatus for solder sphere placement using an air knife

A method of solder bumping an array of solder pads on a substrate, comprising the steps of:

• applying an adhesion layer to the solder pads in the array of solder pads;
• placing a stencil over the substrate, the stencil having an array of apertures corresponding to the array of solder pads, each aperture exposing a substantial portion of each of the solder pads in the array;
• applying solder balls in bulk onto the stencil, wherein the stencil allows only one solder ball per aperture;
• and
• removing excess solder balls by using a directed column of air across the surface of the stencil.

A station in a manufacturing line for the accurate placement of solder balls on a ball grid array package and for the removal of excess solder balls, comprising:

• a substrate having an array of solder pads;
• an adhesion layer on the solder pads;
• a stencil placed on top of the substrate which allows only one solder ball to contact each solder pad, the stencil having an array of apertures corresponding to the array of solder pads and substantially exposing each of the solder pads of the array;
• a pallet for holding and transporting the substrate to the stencil and further along the manufacturing line;
• a dispenser for pouring solder balls in bulk over the stencil;
• a vibration device coupled to the station for urging the solder balls into the apertures of the stencil and onto the adhesion layer above the solder pads;
• and
• a means for removing excess solder balls from the stencil.

A station for the in a manufacturing line for the accurate placement of solder balls on a ball grid array package and for the removal of excess solder balls, comprising:

• a substrate having an array of solder pads;
• an adhesion layer on the solder pads;
• a stencil placed on top of the substrate and having a height between 1/4 times the diameter of one of the solder balls and 5/4 times the diameter of one of the balls, the stencil having an array of apertures corresponding to the array of solder pads and substantially exposing each of the solder pads of the array;
• a pallet for holding and transporting the substrate to the stencil and further along the manufacturing line;
• a dispenser for pouring solder balls in bulk over the stencil;
• a vibration device coupled to the station for urging the solder balls into the apertures of the stencil and onto the adhesion layer above the solder pads;
• and
• a moving directed column of air across the surface of the substrate to remove excess solder balls from the stencil.