A wire bondable plastic encapsulated semiconductor device (58) having no die supporting surface can be manufactured. In one embodiment, a semiconductor die (22) and a plurality of conductors (12) extending toward the periphery of the die are provided. The die is rigidly held in place on a workholder (60) with a vacuum (62) for the wire bonding process. Wire bonds (26) electrically connect the die to the conductors. The wire bonded die is then placed inside a mold cavity (64), and a resin encapsulated is transferred into the cavity under elevated temperature and pressure to form package body (70) around the die, the wire bonds and a portion of the conductors. Before the package body is formed, the die is supported solely by the the rigidity of the wire bonds since there is no die supporting surface connected to the conductors.

Method for making semiconductor device having no die supporting surface

A molded plastic package incorporates a lead frame which includes a plurality of leads radially aligned around a central opening. A die is mounted in the central opening and is electrically connected to the leads by wire bonding. A molded plastic casing is formed over the die, wiring and lead frame to encapsulate the package. The lower surfaces of the die and lead frame are exposed through the package. A method for making the molded plastic package includes mounting the die and lead frame onto an adhesive tape, electrically connecting the die to the leads by wire bonding, forming a molded plastic casing over the die, wire bonding and lead frame, and then removing the adhesive tape to expose the lower surfaces of the die and the lead frame.

Plastic package with exposed die

A molded plastic package for semiconductor devices incorporating a heat sink, controlled impedance leads and separate power and ground rings is described. The lead frame of the package, separated by a dielectric layer, is attached to a metal heat sink. It has more than one ring for power and ground connections. The die itself is attached directly onto the heat sink through a window on the dielectric and provides high power dissipation. The package is molded using conventional materials and equipment.

Molded plastic package with heat sink and enhanced electrical performance

A major issue in the semiconductor industry is the amount of power that a silicon device dissipates. As the density of silicon integrated circuits increases with improvements in wafer processing, so does the amount of heat which must be evacuated. If the power of the silicon devices exceeds one watt, the plastic encapsulating material normally yields to the more expensive ceramic or metal packages which can dissipate thermal energy more efficiently. The conventional molded package is a silicon device such as a chip mounted onto a copper paddle which spreads the heat radially in the material and is bonded to leads via thin wires. The three major paths for the heat to escape are by conduction through the molding compound to the surface of the package where removal is by convection, and by conduction from the silicon device through the thin wires to the leads of the package and then to the printed circuit board, and by a heat conducting paddle which radially spreads the heat through the molding compound. In each instance, the heat dissipating path is through a relatively poor thermal conductor. In accordance with the principles of the invention, there is provided an improved thermal path for conducting heat from the silicon device to the surface of the plastic package. The improved thermal path comprises a post of heat conducting material positioned to extend from the silicon device to a surface of the plastic package. One end of the post is positioned to receive heat generated by the silicon device and the other end is exposed to air at the surface of the plastic package. A waist section of the post located between the ends of the post has a dimension which is different than that of the end. Additionally the ends can have dimensions which are either equal or unequal. The post configuration enables the molded package to capture the post without creating cracks in the molded package.

Molded circuit package having heat dissipating post

A tape ball grid array (TBGA) package, and a method of making a TBGA package, includes the use of a metal or other stiffener affixed to a flexible tape on which conductive traces connect contact points on an integrated circuit (IC) chip with an array of solder balls. The stiffener is perforated with a pattern of small vent holes. The TBGA package materials are hygroscopic. When the TBGA package is heated during 2nd level packaging, e.g., during solder reflow, moisture absorbed within the hygroscopic materials evaporates and the resulting water vapor is able to escape through the vent holes, rather than becoming trapped within the IC package and introducing various 2nd level packing failure modes.

Tape ball grid array package with perforated metal stiffener

A semiconductor device having a heat sink is provided in which an opening through the heat sink enables a vacuum source to be applied to a semiconductor die mounted surface. In one form, a semiconductor die is attached to a mounting surface of a leadframe. The leadframe also has a plurality of leads which are electrically coupled to the semiconductor die. The semiconductor die and portions of the leads encapsulated in a package body. Also incorporated in the package body is a heat sink. The heat sink has an opening which extends through the heat sink and exposes a portion of the mounting surface of the leadframe. The opening is used to apply a vacuum to the mounting surface during the formation of the package body so that the mounting surface and heat sink are held in close proximity. The closeness provides a good thermal conduction path from the semiconductor die to the ambient, thereby enhancing the thermal dissipation properties of the device.

Thermally enhanced semiconductor device utilizing a vacuum to ultimately enhance thermal dissipation

A method for making a semiconductor device having a heat sink is provided in which an opening through the heat sink enables a vacuum source to be applied to a semiconductor die mounting surface. In one form, a semiconductor die is attached to a mounting surface of a leadframe. The leadframe also has a plurality of leads which are electrically coupled to the semiconductor die. The semiconductor die and portions of the leads are encapsulated in a package body. Also incorporated into the package body is a heat sink. The heat sink has an opening which extends through the heat sink and exposes a portion of the mounting surface of the leadframe. The opening is used to apply a vacuum to the mounting surface during the formation of the package body so that the mounting surface and heat sink are held in close proximity. The closeness provides a good thermal conduction path from the semiconductor die to the ambient, thereby enhancing the thermal dissipation properties of the device.

Method for making a thermally enhanced semiconductor device by holding a leadframe against a heatsink through vacuum suction in a molding operation

A low profile semiconductor device (24) is manufactured by mounting a semiconductor die (26) onto a substrate (28) using an interposer (30). The interposer couples an active surface (32) of the die (26) to conductive traces (33) on the top surface of the substrate. The interposer is directionally conductive so that electrical conductivity is limited to the z-direction through thickness of the interposer. The interposer both affixes the die to the substrate and provides the first level of interconnects for the device. The inactive surface (36) of the die can be exposed for efficient thermal dissipation. An optional heat spreader (50) may be added for increased thermal management. The device may be overmolded, glob-topped, capped, or unencapsulated. Separate die-attach and wire bonding processes are eliminated. A second level of interconnects are provided by either solder balls (38), solder columns (44), or pins (64).

Low profile semiconductor device with like-sized chip and mounting substrate

A molded semiconductor device (24) having greater resistance to package cracking during board mounting in addition to increased thermal performance is provided wherein the device has a reduced semiconductor die to flag interface and a drop-in heat sink. The semiconductor die (12) is mounted on a leadframe (16) having a flag (15) with an opening to expose a substantial portion of the inactive surface (14) of the die (12). Decreasing the interfacial contact area between the die (12) and the flag (15) reduces the risk of package cracking during board mounting by limiting the area where delamination typically occurs. An encapsulant (22) forms a package body which encompasses an opening (23) to expose a substantial portion of the inactive surface (14) of the semiconductor die (12). A heat sink (26) is inserted into the opening (23), directly coupling the heat sink (26) to the die (12), after the semiconductor package is mounted onto a printed circuit board.

Drop-in heat sink package with window frame flag

The device has a semiconductor die (18) mounted upon a downset X-shape die support (12) of a lead frame (10, 40). The lead frame also has tie bars (16) which are connected to the X-shape die support. Attached to the tie bars are thermal bars (14, 14') which are located between the semiconductor die and inner portion of the leads (20). The inner portion of the leads, the tie bars, and the thermal bars are offset from the plane occupied by the X-shape die support. The thermal bars aid in dissipating the heat from the die into the nearby lead tips so that the heat can be conducted out of the package body (30) through the thermally conductive lead frame. The semiconductor die is wire bonded to the inner portion of the leads. A package body (30) protects the die, the wire bonds (26), the thermal bars, and the inner portion of the leads.

Bennett A. Joiner

Papers

Thermally enhanced semiconductor device utilizing a vacuum to ultimately enhance thermal dissipation

Method for making a thermally enhanced semiconductor device by holding a leadframe against a heatsink through vacuum suction in a molding operation

Low profile semiconductor device with like-sized chip and mounting substrate

Drop-in heat sink package with window frame flag

Method of fabricating a thermally enhanced lead frame