A transfer molded plastic package having a cavity for accommodating a semiconductor chip is disclosed. A leadframe assembly process is shown wherein the leadframe finger pattern is provided with a resilient or elastic O-ring bead. Top and bottom housing plates which have dimensions that are larger than the bead form the upper and lower surfaces of the package. These plates can be formed of any suitably rigid material. They may be composed of ceramic in low power devices. For high power operation at least one metal plate can be employed. The chip or chips are connected to the lead frame and, along with the top and bottom plates, is located in a transfer mold. The plates are in registy and located so that their outer edges extend beyond the O-ring bead. The mold cavities include faces which press against the plates which are held apart by the O-ring bead so that the bead is compressed by the mold closure. A plastic encapsulant is molded around the periphery of the plates so that the leadframe fingers are secured therein to become package pins. The mold faces being pressed against the two plates precludes encapsulant from their faces which then become the outer faces of the package. The O-ring bead precludes the encapsulant from coming into contact with the semiconductor chip during the molding operation thereby creating a cavity package. In an improvement an elastic O-ring can be applied to a leadframe in registry with the outer package dimensions and the leadframe dam bars eliminated. When the transfer mold is closed the cavities are completed by the elastic ring. Therefore, the mold flash is eliminated and a dambarless leadframe assembly process is available. Finally, if desired, the dambarless process can employ a plastic that is soluble in a suitable solvent. Then, after the molding is completed, the bead is removed by means of the solvent. Desirably, a water solube plastic is employed.
A method of packaging a power semiconductor device is disclosed, comprising the steps of preparing a lead frame including a paddle for providing a semiconductor chip on a top surface thereof, tie bars for supporting said paddle, wherein said paddle being provided lower in horizontal surface than the leads; attaching a heat radiating plate on a bottom surface of the paddle by cladding; attaching a Kovar plate on the top surface of the paddle by soldering, said Kovar plate having similar heat expansion coefficient to that of the chip; providing the chip on the Kovar plate by soldering; wire-bonding terminals of said semiconductor chip to the corresponding leads of the lead frame, respectively; coating polyimide over the semiconductor chip by spin-coating; curing the polyimide coated thus; forming a metal cap above the said paddle by soldering, and injecting a molding material into a molder for enclosing the paddle and curing the molding material injected thus the method can be applied to produce a plastic package of a power semiconductor device at low cost. The metal cap is grounded through the tie bars as a source electrode to shield a noise.
A method of making an integrated circuit (IC) device comprises the steps of providing (300) at least one lead frame (10) comprising a plurality of leads (14), laminating (302) the lead frame (10) with a photoresist, exposing (304) a portion of the photoresist to impose a pattern on the photoresist (10), and developing (306) the photoresist on lead frame (10), such that the photoresist produces a pair of strips and forms non-electrically conductive bonds (30, 32) between leads (14). Further, an IC device comprises a plurality of leads (14) extending from a lead frame (10). The leads (14) comprise an inner lead portion (26), a middle lead portion (27) and an outer lead portion (28). A photoresist is overlaid onto the leads (14). The photoresist comprises an inner strip (30) disposed across the plurality of leads (14) between the inner lead portion (26) and the middle lead portion (27) and an outer strip (32 ) disposed across the plurality of leads (14) between the outer lead portion (28) and the middle lead portion (27). The photoresist inhibits cavity molding (42) plastic from seeping onto inner lead portion (26) or outer lead portion (28) and creates a non-electrically conductive bond between the leads (14).
Method and device for molding integrated circuit packages using dambarless lead frames are disclosed. The mold dies and the lead frame have means for preventing resin leakage out of the mold dies during the package molding step. The leakage preventing means may comprise a tape put on the leads, an enlarged area sections provided on each lead and notches formed on each lead. The leakage preventing means may comprise projections formed on a lead pressing frame of one of the mold dies. In another embodiment, an auxiliary lead frame, which has a plurality of rectangular openings and will be fixed to a bottom mold die, is used as the resin leakage preventing means. When using the auxiliary lead frame, the dambarless lead frame is laid on the auxiliary lead frame and clamped by a top mold die. The enlarged area sections may be formed on the inner leads exclusively or on both the inner and outer leads.
The invention relates to an arrangement comprising a support body with a substrate holder, mounted thereon on a gas bearing with rotating drive. The gas bearing and the rotating drive are formed by gas flowing in through nozzles arranged in the separating gaps between support body and substrate. The support body and the substrate holder are embodied as rings, whereby the rings lie on each other in a self-centering manner and the one ring comprises a ring bead extending into a ring recess on the other ring.
A molded encapsulated electronic component containing a silicon device, chip, or integrated circuit characterized by ease of fabrication and minimum possibility of breakage or dislocation, included a lead frame bearing a compressed, thin elastomeric, anisotropic, electrically conductive compliant interconnect on which the silicon integrated circuit is positioned--all mounted within an all-enveloping plastic.
