Stiffened semiconductor die package

A stiffened semiconductor die package has a semiconductor die including an integrated circuit. The die has an active side with die bonding pads and an opposite inactive side. A conductive frame that acts as a ground plane surrounds all edges of the die and a mold compound covers the conductive frame and the edges of the die. A thermally conductive sheet is attached to the inactive side of the die. A dielectric support structure with external connector pads with solder deposits is attached to the active side of the die. The external connector pads are selectively electrically coupled to the die bonding pads.

BACKGROUND OF THE INVENTION

The present invention relates to semiconductor packaging and, more particularly, to a stiffened semiconductor die package.

Semiconductor die packages are often manufactured with increased functionality. As a result, the number of external connectors (pin count) must often be increased to accommodate the increased functionality and power supply rail requirements of the semiconductor die. The number of external connectors is due to the increase in the number of die connection pads comprising power rail pads, ground rail pads and data input and output pads. Other requirements of increased functionality semiconductor die packages can include increased heat dissipation and reduced package thickness, especially when the package is to be incorporated into a small handheld device where reduced device size can be a major specification requirement. Unfortunately, relatively thin semiconductor packages can warp during manufacturing, which may affect package yield. When populating circuit boards, such warping may also affect pick-and-place machine performance since the warped packages may not have a suitable flat surface required by suction cups of the pick-and-place machine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention, and is not intended to represent the only forms in which the present invention may be practised. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the invention. In the drawings, like numerals are used to indicate like elements throughout. Furthermore, terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that module, circuit, device components, structures and method steps that comprises a list of elements or steps does not include only those elements but may include other elements or steps not expressly listed or inherent to such module, circuit, device components or steps. An element or step proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements or steps that comprises the element or step.

In one embodiment, the present invention provides a stiffened semiconductor die package including a semiconductor die including an integrated circuit, the semiconductor die having an active side with die bonding pads and an opposite inactive side. A conductive frame that acts as a ground plane surrounds the edges of the die and a mold compound encapsulates the conductive frame and surrounds the edges of the die. The stiffened semiconductor die package has a thermally conductive sheet attached to the inactive side of the semiconductor die and there is a dielectric support structure with external connector pads having solder deposits mounted thereto. The dielectric support structure is attached to the active side of the semiconductor die and the external connector pads are selectively electrically coupled to the die bonding pads.

In another embodiment, the present invention provides a method of manufacturing stiffened semiconductor die packages. The method includes providing an assembly structure having a temporary support with a sheet of interconnected ground plane conductive frames mounted thereto, where each of the frames defines a die enclosure. Semiconductor dies are placed into respective die enclosures. The die has an integrated circuit formed therein, an active side with die bonding pads placed adjacent the temporary support, and an inactive side opposite the active side. A molding process is performed to encapsulate or cover the ground plane conductive frames, and the semiconductor dies, which covers the inactive side of each die. Next, a process of removing part of the mold compound to expose the inactive side of the semiconductor die is performed. The method also includes attaching a thermally conductive sheet to the inactive side of the semiconductor die, and replacing the temporary support with a dielectric support structure that has external connector pads selectively electrically coupled to the die bonding pads. There is also performed a process of separating the ground plane conductive frames from each other to thereby provide the stiffened semiconductor die packages.

Referring toFIG. 1, a top plan view of part of an assembly structure100in accordance with a preferred embodiment of the present invention is shown. The assembly structure100includes a temporary support110with a sheet120mounted on the temporary support110. The sheet120is a sheet of interconnected ground plane conductive frames130and each of the frames130defines a die enclosure140, each enclosure140being an aperture in the sheet120that exposes the temporary support110. There are blank slots150and through slots160in the interconnected ground plane conductive frames130, the blank slots150are on an underside of the sheet120and the through slots160expose areas of the temporary support110.

Referring toFIG. 2, a top plan view of part of a temporary die assembly200in accordance with a preferred embodiment of the present invention is shown. The temporary die assembly200is the assembly structure100with a semiconductor die210placed into a respective die enclosure140so that each semiconductor die210is mounted on the temporary support110.

Referring toFIG. 3, a cross-sectional side view, through2-2′, of a temporary framed die assembly300in accordance with a preferred embodiment of the present invention is shown. The temporary framed die assembly300is the temporary die assembly200with an abutting mold frame310that abuts the temporary support110. It will be clear from this illustration that each semiconductor die210has an active side,320with die bonding pads330placed adjacent the temporary support110, and an inactive side340that is opposite to the active side320. Also, as will be apparent to a person skilled in the art, the die bonding pads330are circuit access nodes for accessing, controlling, powering or communicating with an electronic circuit provided by each semiconductor die210.

The temporary support110is a multi-layered structure comprising a glass or ceramic substrate350with an upper surface360coated with a thermal release tape370. On top of the thermal release tape370is a double-sided silicon polyimide adhesive tape380which fixes to the temporary support110: each semiconductor die210; the sheet120of ground plane conductive frames130; and the mold frame310.

Referring toFIG. 4, a cross-sectional side view of a molded temporary assembly400, in accordance with a preferred embodiment of the present invention, is shown. The molded temporary assembly400is the temporary framed die assembly300after a process of molding. The molding process is usually performed by a liquid encapsulation or compression molding process and typically molds a single slab-like mold compound410over the ground plane conductive frames130, and each semiconductor die210. As a result, the mold compound410encapsulates or covers the inactive side340of each die210.

FIG. 5is a cross-sectional side view of a ground temporary assembly500in accordance with a preferred embodiment of the present invention. The ground temporary assembly500is the molded temporary assembly400after the mold frame310has been removed and part of the mold compound410has been removed by a grinding process. The grinding process removes enough of the mold compound410to expose the inactive side340of the semiconductor die210. Typically the grinding process also removes a layer of the inactive side340of the semiconductor die340and results in both cleaning the inactive side340and providing an upper planar surface510. The upper planar surface is formed by both a ground surface of the mold compound410and inactive side340of the semiconductor die210.

Referring toFIG. 6, a cross-sectional side view of a stiffened temporary assembly600in accordance with a preferred embodiment of the present invention is shown. The stiffened temporary assembly600is the ground temporary assembly500with a thermally conductive sheet610attached to the upper planar surface510by a thermally conductive epoxy620. The thermally conductive sheet610has an upper surface630with slots640and side surfaces650of the slots define outer edges of respective stiffened semiconductor die packages (shown later) formed by the assembly600. The slots640are aligned with the slots150,160in the ground plane conductive frames130, and slots150,160also have side surfaces660that define outer edges of respective stiffened semiconductor die packages (shown later) formed by the assembly600. The width of the slots150,160and640are identical and since these slots are aligned, their respective side surfaces650,660are coplanar.

FIG. 7is a cross-sectional inverted side view of an integrated assembly of stiffened semiconductor die packages700in accordance with a preferred embodiment of the present invention. The integrated assembly of stiffened semiconductor die packages700is the stiffened temporary assembly600with the temporary support110replaced with a dielectric support structure710. The dielectric support structure710has external connector pads720that are selectively electrically coupled to the die bonding pads330by electrically conductive runners730or any other connector arrangement that are known in the art. Typically, the dielectric support structure710is selectively formed from multiple masked layers (deposits) of dielectric material and conductive material. The conductive material is typically copper and provides the runners730and connector pads720by spin coating, sputtering or electroplating. Mounted to the external connector pads720are solder deposits in the form of solder balls740that have been held temporarily in place (by a flux paste) and then soldered, by a solder reflow heating process, to their respective external connector pads720.

FIG. 8is a cross-sectional side view of a stiffened semiconductor die package800in accordance with a preferred embodiment of the present invention. The stiffened semiconductor die package800is a package formed by separating the integrated assembly of stiffened semiconductor die packages700into individual die packages by a cutting, punching or sawing process typically known as singulating. Each separated (singulated) stiffened semiconductor die package800includes a single ground plane conductive frame130to which is molded the mold compound410. The mold compound410is also molded to all edges810of the semiconductor die210and therefore provides both structural support and a moisture barrier. Also each part of the separated (singulated) along the slots150,160and640typically by a saw with a blade width identical to the width of the slots150,160and640. The slots150,160and640therefore approximately define outer edges of the stiffened semiconductor die package800and reduce the demands on the blade thus facilitating a relatively fast and efficient singulation process.

The stiffened semiconductor die package800has the singulated area of the thermally conductive sheet610attached to the inactive340side of the semiconductor die210. The inactive side340is coplanar with the aligned surface of the mold compound410and forms the planar surface510to which is attached the singulated area of the thermally conductive sheet610. As shown, the dielectric support structure710is attached to the ground plane conductive frame130and thus the ground plane conductive frame130and mold compound410are sandwiched between the thermally conductive sheet610and dielectric support structure710. Furthermore, a surface820of the ground plane conductive frame130is coplanar, along a plane P, with a surface of the die bonding pads830. Also, the external connector pads720that are selectively electrically coupled to the die bonding pads330, or the singulated ground plane conductive frame130, by the electrically conductive runners730. In addition in this embodiment the solder deposits740form a ball grid array (BGA) structure850for surface mounting the stiffened semiconductor die package800to a circuit board.

Referring toFIG. 9, a cross-sectional plan view through8-8′ of the stiffened semiconductor die package800in accordance with a preferred embodiment of the present invention is illustrated. The ground plane conductive frame130surrounds all edges810of the semiconductor die210and also surrounds some of the mold compound410that is molded to the ground plane conductive frame130. More specifically, part of the mold compound410forms a rectangular frame910around the edges810of the semiconductor die210. The rectangular frame910is sandwiched between inner edges920of the ground plane conductive frame130and the edges810of the semiconductor die210.

Referring toFIG. 10, a flow chart illustrating a method1000of manufacturing stiffened semiconductor die packages800in accordance with a preferred embodiment of the present invention is shown. The method1000, at a providing block1010, provides the assembly structure100having the temporary support110with the sheet of interconnected ground plane conductive frames130. At a placing block1020, a process of placing the dies210into respective die enclosures140to form the temporary die assembly200is performed. The method1000, at a molding block1030, then performs a process molding the mold compound410to the ground plane conductive frames130and every semiconductor die210. The process of molding is usually performed by a liquid encapsulation or compression molding process. After the molding process is completed, the mold compound410covers the inactive side340of each die210so that there is a single slab-like mold compound410over the ground plane conductive frames130and each semiconductor die210.

At a removing block1040, a grinding process is performed to remove part of the mold compound410to expose the inactive side340. The grinding process typically removes a layer of the inactive side340. The grinding process also results in the inactive side340being coplanar with the aligned surface of the mold compound410and thus forms the planar surface510. The method1000, at an attaching block1050, performs a procedure of attaching the thermally conductive sheet610to the inactive side340of the semiconductor die210and also to the aligned planar surface510of the mold compound410.

At a replacing block1060, the temporary support110is replaced with the dielectric support structure710that has the external connector pads720selectively electrically coupled to the die bonding pads330. The dielectric support structure710and external connector pads720are formed by Redistributed Chip Packaging (RCP) techniques, which include photolithography and copper plating to create the required interconnects. It will therefore be apparent to a person skilled in the art that the dielectric support structure710is selectively formed from multiple masked layers (deposits) of dielectric material and conductive material.

At a selectively mounting block1070there is performed a process of selectively mounting the solder deposits (solder balls740) to the external connector pads720. Also, at a separating block1080, the ground plane conductive frames130are separated from each other by a singulation process to thereby provide the stiffened semiconductor die packages800. As mentioned above, the singulation process is performed by cutting or sawing along the slots150,160and640, and the singulation process also includes separating the single mold410as will be apparent to a person skilled in the art. Furthermore, the resulting individual semiconductor die packages800include the ball grid array structure850formed by the solder deposits (solder balls740).

Advantageously, the present invention provides a relatively thin stiffened semiconductor die package800that at least alleviates problems of warping during manufacturing since the thermally conductive sheet610and mold compound410provide additional rigidity or stiffening. Also, the thermally conductive sheet610is attached to the inactive side340of the semiconductor die210which can therefore assist in heat dissipation. In addition, the aligned slots slots150,160and640approximately define outer edges of the stiffened semiconductor die package800and thus alleviate or reduce the demands on the cutting blades during singulation.

The description of the preferred embodiments of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the invention to the forms disclosed. It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but covers modifications within the spirit and scope of the present invention as defined by the appended claims.