Mitsubishi Denki Kabushiki Kaisha

Kazuharu Oshio

Hirozoh Kanegae

Kunito Sakai

A molding machine comprises a mold composed of lower and upper mold sections. A recess is defined in the lower mold section to receive a lead frame or other objects. The lead frame is sandwiched between the upper and lower mold sections. A mold cavity is defined in the lower mold section below the recess so as to receive a thermosetting resin or encapsulant. A gasket groove is defined adjacent to the mold cavity to receive a gasket. The gasket is subject to plastic deformation upon application of force. An oil chamber is communicated with the gasket groove and contains hydraulic oil. The hydraulic oil is pressurized to urge the gasket against the lead frame. As a result, the gasket is so deformed as to closely contact the surface of the lead frame and seal the mold cavity. The hydraulic oil is preferably mixed with thermoplastic resin in powder form.

Encapsulation method

A molding apparatus having an upper mold, a lower mold, and a cylindrical mold cavity defined between the upper mold and the lower mold and adapted to receive a molding material such as epoxy resin. An annular recess is defined in the lower mold adjacent to the mold cavity. A gasket is fit in the recess and made of lead. An oil passage is defined in the lower mold. Silicon oil as a pressure medium is fed to the recess through the oil passage so as to press the gasket against the upper mold. Then, the gasket is deformed to form a seal around a portion of the mold cavity where the upper and lower molds mate with one another. An annular spacer is placed in the bottom of the recess. An annular groove is defined below and along the bottom of the recess so as to allow the silicon oil to flow below and along the annular spacer, whereby sufficient pressure is exerted uniformly on the gasket to cause deformation of the gasket.

Molding apparatus and method in which a mold cavity gasket is deformed

A molding machine includes a mold composed of lower and upper mold sections. A recess is defined in the lower mold section to receive a lead frame or other objects. The lead frame is sandwiched between the upper and lower mold sections. A mold cavity is defined in the lower mold section below the recess so as to receive a thermosetting resin or encapsulant. A gasket groove is defined adjacent to the mold cavity to receive a gasket. The gasket is subject to plastic deformation upon application of force. An oil chamber is communicated with the gasket groove and contains hydraulic oil. The hydraulic oil is pressurized to urge the gasket against the lead frame. As a result, the gasket is so deformed as to closely contact the surface of the lead frame and seal the mold cavity. The hydraulic oil is preferably mixed with thermoplastic resin in powder form.

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Hyogo-ken, Japan

Kazuharu Oshio