Direct drive electro-mechanical press for encapsulating semiconductor devices

摘要

A direct drive electro-mechanical press for encapsulating semiconductor devices has at least a clamping axis and a transfer axis. The clamping axis has a planetary roller screw coupled to a tie bar platen assembly on which at least one top mold is mounted. A two-speed gearbox is further coupled to the clamping axis for switching between a high speed mode and a high torque mode along the clamping axis. The two-speed gearbox has a high speed clutch coupled to a speed reducer and a high torque clutch respectively. The transfer axis is slidably located above the clamping axis; the transfer axis has another planetary roller screw coupled to a bottom platen on which at least one bottom mold is mounted. The transfer axis transfers the molding resin from the pot into the cavities formed when the top and bottom molds are clamped together. The use of two-speed gearbox and planetary roller screw along the clamping axis and the use of planetary roller screw along the transfer axis not only reduce the number of joints or links required under prior art systems, but also permit the press to deliver superior velocities and clamping tonnage. A closed-loop control is provided to the clamping and transfer axes respectively for minimizing the disproportionate drive from the electro-mechanical press. In addition to the controllers and drives, the closed-loop control provides direct feedback on the clamping tonnage on the tie bars and transfer pressure in the mold blocks.