High-power ball grid array package, heat spreader used in the BGA package and method for manufacturing the same

A high-power BGA includes a printed circuit board with a through hole, connection pads formed on the bottom of the printed circuit board, matrix solder balls surrounding the through hole and adjacent to the connection pads, a heat spreader on the top surface of the printed circuit board that includes an insulating layer of a high thermal conductivity, a semiconductor chip mounted within the through hole on the bottom surface of the heat spreader that includes a number of contact pads for bonding with the connection pads using gold wires, and a passive film filling the through hole and around the semiconductor chip. By interposing a ceramic insulating layer between the semiconductor chip and the heat spreader, charge generation between the semiconductor chip and the heat spreader is sharply reduced, and defects such as ESD (electrostatic discharge) is reduced during testing and mounting of the package.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No. 2002-32972, filed on Jun. 12, 2002, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to semiconductor packages and, more particularly, to a high-power ball grid array (BGA) package having a heat spreader, a method for manufacturing the heat spreader, a BGA printed circuit board (PCB) to which the method is applied, and a method for manufacturing the BGA PCB.

2. Description of the Related Art

As devices become highly integrated, the number of connection pads in a semiconductor device, such as a semiconductor memory device, increases. Thus, the number of lead lines in a package included in a PCB also increases. As the number of lead lines increases, a lead frame using conventional package technology cannot be applied to a highly-integrated semiconductor chip having over 400 lead lines. Accordingly, a BGA package has been introduced in which package output terminals are arranged on a large bottom board of the package.

The BGA package includes a square-shaped main body, a semiconductor chip which is mounted on the top surface of the main body, and matrix solder balls at the bottom surface of the main body that contact the printed circuit board and thus can be arranged and mounted on a pad of the printed circuit board by using a reflow process.

Such a BGA package requires a heat spreader on the surface of the semiconductor chip so as to emit heat to the outside the package when a considerable amount of heat is generated during the operation of the semiconductor chip. However, since a gold wire is formed upwardly to connect the semiconductor chip with the pad of the main body of the package, it is difficult to mount the heat spreader on the BGA package and so such BGA package is not appropriate for a high-power BGA package.

Referring toFIG. 12, illustrated is a conventional, high-power BGA package structured to overcome the heat emitting problem of the conventional BGA package described above. The conventional high-power BGA package includes a package printed circuit board1200, a through portion1200aat the center of the package circuit board1200, pads for bonding (not shown) at the bottom surface of the printed circuit board1200, a heat spreader1110that is connected to the top surface of a metal layer1120, a supporting main body1130that is connected to the bottom surface of the heat spreader1110, and a semiconductor chip1101that is mounted under the supporting main body1130within the through portion1200a, includes a plurality of metal pads1101aon its bottom surface, and is connected to pads for the bonding (not shown) and gold wires1101b. This conventional high-power BGA package is capable of easily emitting heat away and cooling the semiconductor chip through the heat spreader1110that is stably mounted on the surface of the BGA package, even though the heat is generated in the semiconductor device.

The heat spreader1110of the conventional high-power BGA package, however, is composed of conductive copper and surface-processed nickel, a fact that results in a constant voltage between the semiconductor chip1101and the heat spreader1110during the operation of the semiconductor chip1101and can cause damage to the semiconductor chip1101in many cases. Consequently, the semiconductor device yield of the conventional BGA package decreases, and the reliability of the semiconductor device may not be ensured when mounting the semiconductor chip on the printed circuit board.

Embodiments of the invention address these and other limitations of conventional devices.

SUMMARY OF THE INVENTION

Embodiments of the invention include a high-power BGA package, a heat spreader used for the high-power BGA package, and a method for manufacturing the high-power BGA package and the heat spreader.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention now will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. In the drawings, the shapes of elements are exaggerated for clarity, and like reference numerals are used to refer to like elements throughout.

FIG. 1is a cross sectional view of a high-power BGA package according to an embodiment of the invention.

Referring toFIG. 1, a high-power BGA package includes a printed circuit board200having a square shape and in which a metal interconnection (not shown) is embedded and a through portion200ais formed at the center. The printed circuit board200includes a plurality of connection pads201surrounding the through portion200a, a heat spreader110that is attached to a lower metal layer120on the surface of the printed circuit board200and includes an insulating layer111formed of a ceramic material, a semiconductor chip101in which there are a plurality of metal pads101anear the center of the bottom surface of the heat spreader110, the metal pads101abeing mounted outwardly through the through hole120a(FIG. 2) and connected with the connection pad201by gold wires bib, a passive film230that fills the through portion200aand forms a protection layer outside of the passive film230, and a dam203which surrounds the outside of the passive film230and protrudes from the printed circuit board200.

The printed circuit board200is a generally square board whose shape is suitable for the BGA package. In the center of the printed circuit board200the through portion200a, which is square in shape, is formed within the printed circuit board200so the semiconductor chip101can be mounted therein. Around the through portion200a, the connection pads201the metal interconnection (not shown) embedded in the printed circuit board200and electrically connect the metal interconnection with the semiconductor chip101.

In the region adjacent to the connection pads201on the bottom surface of the printed circuit board200, solder balls210are formed surrounding the through portion200a. The solder balls210are formed of a low melting point eutectic metal alloy, such as a lead (Pb) or tin (Sn) alloy. When the BGA package is mounted on a mounted body (not shown), a reflow process is performed by applying heat, and the solder balls210are melted and alloyed with an adhesive pad (not shown) of the mounted body, thereby allowing the printed circuit board200to easily adhere to the mounted body.

FIG. 2is a cross sectional view of a heat spreader that is mounted on the high-power BGA package ofFIG. 1

Referring toFIG. 2, on the surface of the printed circuit board200, the heat spreader110of the high-power BGA package is a generally square board of roughly the same size and shape as the printed circuit board200and is formed to contact the upper portion of the through portion200a(FIG. 1). That is, formed on the region on which the printed circuit board200contacts are a lower metal layer120having a through portion120ashaped like the through portion200aof the printed circuit board200, an insulating layer111on the lower metal layer120, an upper metal layer113on the insulating layer111, and a protection layer115on the upper metal layer113to protect the surface of the upper metal layer113.

The insulating layer111can be formed of a ceramic of a high thermal conductivity, such as AIN, Al2O3, BeO, or the like. Then, the ceramic functions as an insulating material and as a thermal conductor, thereby heat emission can be obtained. The upper metal layer113on the insulating layer111and the lower metal layer120under the insulating layer111are grounding electrodes and are formed of copper (Cu), a copper alloy, or the like. Forming a material having a high thermal conductivity, i.e., the upper metal film113, on the upper portion of the insulating layer111enhances the heat emission. In addition, on the surface of the upper metal layer113, the protection layer115may be further formed of nickel Ni, a nickel alloy, or the like, having a good etching quality so as to protect the surface of the metal layer113. Consequently, in the heat spreader110, the lower metal layer120contacts the printed circuit board200and the insulating layer111, and the upper metal layer113and the protection layer115are sequentially formed on the lower metal layer120.

FIGS. 3 through 7are sectional views illustrating a sequence of steps in the manufacturing of the heat spreader for the high-power BGA package according to embodiments the present invention.

Referring toFIG. 3, an insulating board111having a predetermined size and shape is prepared. (The insulating board will become the insulating layer of the heat spreader, and thus the same reference numeral (111) is used for the insulating board). The insulating board111is preferably shaped like a square board so that a maximum number of the heat spreaders110can be manufactured from a given insulating board111. The insulating board111is made of a ceramic having a high thermal conductivity, such as AIN, Al2O3, or BeO, for instance. Thin metal layers are applied to both sides of the prepared insulating board111and the lower metal layer120and the upper metal layer113are arranged on the insulating board111. Here, the upper and lower metal layers113and120have high electric and thermal conductivities and are formed of material such as copper (Cu) or a copper alloy. The upper and lower metal layers113and120are formed on both sides of the insulating board111by adhering the prepared thin metal layers to both sides of the insulating board111through direct adherence or brazing. Such adherence is advantageous for low cost production. Alternatively, the upper and lower metal layers113and120may be formed by electroless plating or physical vapor deposition, or by other methods.

Referring toFIG. 4, a chip receiving portion120a, where the semiconductor chip101will be mounted after a patterning process, is formed on the lower metal layer120. One method for forming the chip receiving portion is for a photoresist300to be formed on the lower metal layer120, and a pattern for the chip receiving portion120ato be formed on the photoresist300. The exposed metal layer120is then removed by wet etching with sulfuric acid and hydrochloric acid using the photoresist300as a mask. Alternatively, the exposed metal layer may be etched using a dry etch process such as reactive ion etching (RIE) or plasma etching in order to form finer patterns. A pattern of the chip receiving portion120ais printed on the lower metal layer120.

Referring toFIG. 5, a cutting pattern111ais formed on the upper metal layer113and the lower metal layer120so that the heat spreader110can be cut to a predetermined size. Here, the cutting pattern may be formed by a laser. The upper and lower metal layers113and120are completely cut, and the cutting pattern111apartially cuts through the surface of the insulating board111to a predetermined depth. Consequently, the heat spreader110can be easily cut to a predetermined size using the cutting pattern111aon the insulating board111.

Referring toFIG. 6, a protection layer115is formed on the surface of the upper metal layer113. Here, the protection layer115can be made of nickel Ni or a nickel alloy and may be formed by electroless plating, sputtering, or physical vapor deposition such as metal evaporation. The protection layer115protects the surface of the metal layer113by preventing the surface of the upper metal layer113from being exposed to an etching environment.

Referring toFIG. 7, after the manufacturing is completed, an individual heat spreader110is produced by cutting the heat spreader110to a predetermined size using the cutting method described above. When mass production of the BGA package process is required, a single heat spreader110or a grouping of of heat spreaders may be cut, e.g., a unit composed of 8 heat spreaders.

FIGS. 8 through 11are sectional views illustrating a sequence of steps in the manufacturing of the high-power BGA package having the heat spreader described inFIGS. 3 to 7.

Referring toFIGS. 8 through 11, the printed circuit board200for the high-power BGA package, which is manufactured according to conventional methods, is mated with the heat spreader110. At the center of the printed circuit board200, a through portion200ahaving a square shape and a predetermined size is formed. At the surface of the printed circuit board200, connection pads201are formed surrounding the through portion200a. The other surface of the printed circuit board200has a flat junction side to contact the heat spreader110. The flat junction side is mated to the lower metal layer120of the heat spreader110. Here, it is desirable that a junction layer, such as a black oxide layer140, is further included between the printed circuit board200and the lower metal layer120. The black oxide layer140is applied to the metal of the heat spreader110to improve the junction between a pre-pleg, which is a material for the junction of the printed circuit board200and the surface of the heat spreader110, which is formed of a contact metal such as copper or nickel.

A dam203protrudes from the bottom of the printed circuit board200. The dam203functions as a sidewall that prevents the liquid filler material of the passive film230(seeFIGS. 1 and 11) from flowing over the dam203when the passive film230is subsequently formed.

Referring toFIG. 9, a chip supporting body130is formed on the bottom surface of the insulating layer111of the heat spreader110, which is exposed by a through portion200aof the printed circuit board200, and the semiconductor chip101is adhered to the chip supporting body130. Here, the semiconductor chip101is mounted such that the side where the metal pads101aare formed faces downward.

Referring toFIG. 10, metal pads101aon the semiconductor chip101are connected to the connection pads201on the printed circuit board200with gold wires101b(FIG. 11). The metal pads101aand the connection pads201aface downward, and so the gold wires101bare connected such that the surface of the insulating layer111of the heat spreader110exposed through the through portion200afaces downward.

Referring toFIG. 11, a passive film230is formed of a synthetic resin to fill the through portion200awhere the semiconductor chip101is located and to completely cover the region where the connection pads201on the printed circuit board200are formed. The passive film230protrudes in the area between the dam203at the bottom of the printed circuit board200.

A number of solder balls201are formed surrounding the through portion200awhere the printed circuit board200is exposed. Here, it is preferable to form the solder balls201in the shape of a matrix to achieve a high solder ball density. The dam203can either be formed when the printed circuit board200is manufactured or when the package assembly is manufactured.

As described above, according to the high-power BGA package of embodiments of the invention, the heat spreader110that includes the insulating layer111between the heat spreader110and the printed circuit board200includes a ceramic of a high conductivity to prevent static electricity from charges flowing between the semiconductor chip101and the upper metal layer113, which functions as ground for the heat spreader110. By using a ceramic of a high thermal conductivity, it is possible to not only obtain the same heat emission effect as the heat emission of the metal layer but also enhance the mechanical strength as a result of the characteristics of the ceramic.

In manufacturing the heat spreader110, the heat spreader110is easily cut to a predetermined size, and any mistakes made during the cutting of the heat spreader110can be reduced by forming grooves to a predetermined depth on the insulating board111of the heat spreader110according to the cutting pattern11a, as described above.

The dam203may be formed when the printed circuit board200is manufactured or when the package is assembled.

The high-power BGA package and a method for manufacturing the heat spreader of the high-power BGA package according to embodiments of the invention are advantageous for the following reasons.

In the high-power BGA package the capacitance occurring between the semiconductor chip and the heat spreader is reduced. Consequently, the number of defects such as ESD (electrostatic discharge) is sharply reduced.

Furthermore, through the method for manufacturing the heat spreader of the high-power BGA package, a cutting pattern of grooves cut through the metal layers and partially through the insulating board is formed such that the heat spreader can be easily cut, and any mistakes made during the cutting of the heat spreader can be reduced.

According to specific examples of the present invention, there is provided a high power ball grid array including a printed circuit board which has a through hole near its center, connection pads which are formed on the bottom of the printed circuit board, matrix solder balls which surround the through hole and are adjacent to the connection pads on the bottom of the printed circuit board, a heat spreader which is formed on the top surface of the printed circuit board and includes an insulating layer of a high thermal conductivity, a semiconductor chip which is mounted downwardly on the bottom surface of the heat spreader, within the through hole, and includes a plurality of pads for bonding via gold wires with the connection pad, and a passive film which fills the through hole and is formed at the bottom of the semiconductor chip.

The printed circuit board can be formed of a synthetic resin or a ceramic material, for instance. The heat spreader includes a chip supporting body to which the semiconductor chip can be adhered to, the ceramic film which is formed on the surface of the chip supporting body, a metal layer which is formed on the surface of the ceramic film, and a protection layer which is formed on the surface of the metal layer to protect the metal layer. Here, the ceramic can include, for example, AIN, BeO, and Al2O3. The metal layer can include copper or a copper alloy. The protection layer is typically nickel or nickel alloy formed by electroless plating, or could be another material formed in another way.

In addition, in a region adjacent to the through hole, the printed circuit board further includes a dam which surrounds the passive film and projects from the printed circuit board.

Another specific example includes a heat spreader for a high-power ball grid array, the heat spreader having a board for emitting heat which is formed by sequentially depositing a supporting main body having a board shape and made of a ceramic, a metal layer for emitting heat, and a protection layer on the surface of the supporting main body, a lower metal layer which is formed on the bottom surface of the supporting main body and has a region where the chip can be mounted, and a region which is formed at the center of the heat spreader and where the semiconductor chip can be adhered.

The supporting main body could be AIN, BeO, and Al2O3, for instance. The metal layer for emitting heat and the lower metal layer could be formed of copper or a copper alloy. The protection layer can be nickel or nickel alloy, the layer formed by electroless plating.

Also disclosed are specific embodiments for manufacturing a heat spreader for a high-power ball grid array. The method includes preparing an insulating board, forming a metal layer on both surfaces of the insulating board formed of a ceramic, patterning the metal layer on one surface of the insulating board formed of a ceramic, to form a region to which the semiconductor chip can be adhered, cutting the metal layer on both surfaces of the insulating board formed of a ceramic to a predetermined size and recessing the surface of the insulating board of a ceramic to a predetermined depth, and forming a protection layer on the surface of the metal layer on both surfaces of the insulating board formed of a ceramic.

Here, the insulating board is formed of a ceramic.

The metal layer can have the same size as the insulating layer, and can be adhered to the metal layer onto both surfaces of the insulating layer. The metal layer could be copper or copper alloy. Adhering the metal layer to the insulating layer can be performed by direct copper bonding or metal brazing, for instance.

Patterning the metal layer can include forming a photoresist on the metal layer on one surface of the insulating layer, forming a pattern of a chip receiving portion where the semiconductor chip can be mounted, by applying a photo process to the photoresist, and transferring the pattern of the chip receiving portion on the metal layer by removing the metal layer which is exposed by etching using the patterned photoresist as a mask. The etching can be wet etching using an acid solution, for example.

A laser can be used for the cutting.

The protection layer can be nickel or nickel alloy, for instance. The protection layer is formed by electroless plating.

Patterning the metal layer can also include forming an oxide layer for a junction on the surface of the metal layer where the printed circuit board is mounted. The oxide layer for the junction can be a black oxide layer.

According to the high-power BGA package of some embodiments of the present invention, a ceramic layer of low conductivity, which is electrically insulated from a metal layer, is interposed between the semiconductor chip and the heat spreader, and thus the heat spreader on the surface of the semiconductor chip can reduce generation of charges between the semiconductor chip and the heat spreader. Accordingly, defects such as electrostatic discharge (ESD) can be reduced when applying an external voltage to high-power BGA package.