Abstract: A work cell for populating a ball grid array employs gravity for transferring solder balls from a tooling plate to the ball grid array. The tooling plate is positioned on a gantry along with a reservoir for solder balls. The gantry, along with the tooling plate and reservoir, is rotated through about one hundred and eighty degrees to spread the solder balls over the tooling plate and to recapture loose solder balls as the gantry rotates. A riser cylinder moves a ball grid array into juxtaposition with the populated tooling plate prior to the point (i.e. angle of rotation) at which gravity operates to drop the solder balls out of the tooling plate. Further rotation results in gravity transfer of the solder balls to a (fluxed) ball grid array. Apparatus employing more than one work cell is also described.

Abstract: The reliable population of a ball grid array is achieved by attaching the array to the inner face of a wheel which is rotatable about a central axis. A tooling fixture is attached to the outer face of the wheel. Each of the ball grid array and the tooling fixture has a face with recesses and the faces face one another. The wheel moves the tooling fixture into a reservoir of solder balls to populate the recesses in the tooling fixture and the solder balls are dropped into the corresponding recesses of the ball grid array when the wheel rotates to a position where the recesses in the ball grid array are beneath the recesses in the tooling fixture. The array and the fixture are spaced apart initially so that the rotation of the wheel moves only the fixture through the reservoir ensuring that all recesses in the fixture are filled and that all solder balls not occupying recesses are removed from the surface of the fixture by the force of gravity as the wheel turns.