IC package with an implanted heat-dissipation fin

An IC package with an implanted heat-dissipation fin is introduced. The IC package provides a plastic package to seal an IC chip. One end of the heat-dissipation fin is implanted inside the plastic package, and another end is left outsides for directly heat-exchanging with a surrounding heat-transfer media. By providing the implanted heat-dissipation fin, a more efficient and broader heat-dissipation path for the IC package can be established so that the total heat dissipation of the IC package can be enhanced.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to an IC package with an implanted heat-dissipation fin, and more particularly to the IC package whose encapsultant merges a protrusive heat-dissipation fin for rapidly dissipating heat generating by the chip to the ambient.

(2) Description of the Prior Art

The concern of heat dissipation in IC packages or electronic devices is rising to an interesting degree that it just can't be ignored anyway in design; especially for those devices with hi-power chips. Generally in the art, two options are usually applied to resolve the heat-dissipating problem of IC packages; that is, attaching a heat-dissipation fin, or say a heat sink, directly onto the local IC package, or mounting an impinging fan aside the concerned IC package. However, foregoing two resolutions can only form an expediting mechanism that can only remove surface heat of the IC package, not the source heat deep in the poor-heat-conductivity encapsultant of the local IC package. Definitely, though the property of poor heat-conductivity is a nature of the plastic-made (typically, epoxy resin-made) encapsultant, yet the effort to quickly remove the interior heat thereof is still appreciated for the sake of reducing possible breakdown of the chip inside the hot encapsultant.

In the art, various efforts have been utilized to meet the aforesaid heat-dissipation problem to the encapsultant of IC package, and some of them are shown inFIG. 1throughFIG. 5.

Referring toFIG. 1, a drop-in heat spreader is schematically shown in an IC package. A heat-generating chip11resting on a pad12is shown to be sealed by an encapsultant10of the IC package1. The drop-in heat spreader13buried in the encapsultant10is located by a predetermined spacing under the pad12as well as the chip11. The drop-in heat spreader13is introduced to spread the heat of the chip11inside the encapsultant10. Upon such an arrangement, though the heat generated by the chip11can be easily spread out by the drop-in heat spreader13, yet the heat is obviously still kept inside the encapsultant10. Furthermore, the location of the heat spreader13is adjacent to the PCB side100of IC package1which in application can only leave a pretty small spacing with the printed circuit board (not shown), and thus the effect of the heat spreader13to lead major heat downward to dissipate through the PCB side100is definitely not superior.

Referring now toFIG. 2, an IC package1with an exposed pad12is schematically shown in which a bottom surface of the pad12is exposed to, typically flush with, the PCB side100of the encapsultant10. However, as described above, efficiency provided by the heat-dissipation mechanism of the exposed pad12to dissipate major heat through the PCB side100is not satisfied. Also in the art, the IC package1with the exposed pad12is usually designed to mount right above a specific metal-skin portion of the PCB (not shown) so that a better thermal way can be established between the PCB and the IC package1. However, the specific metal-skin portion does make difficult and higher cost to manufacture of the PCB.

Referring now toFIG. 3, the IC package1includes an exposed heat slug13directly contacting the pad12inside the encapsultant10. Again, such a design still utilizes the downward heat-dissipation path through the PCB side100of the encapsultant10. Except for the manufacturing problem mentioned above, the design ofFIG. 3still has problems in matching accuracy between the pad12and the heat slug13so that it is seldom used in practice.

In either example shown above,FIG. 1throughFIG. 3, the IC package1is one of plastic quad flat packs (known as PQFP) which the manufacturing is critical in molding and thereby the mold-in heat spreader13can only arranged at the PCB side100of the IC package1, not the opposing open side200which can proved a better ventilation environment after mounting the IC package. On the other hand, for an IC package of ball grid array packs (known as BGA), similar drop-in heat spreader can be also adopted. However, in consideration of the ball grids, the drop-in heat spreader of a BGA IC package is usually arranged close to the open side200of the encapsultant10; i.e. the side away from the printed circuit board or the main board which mounts the IC package.

Referring now toFIG. 4, a BGA IC package1having a stacked-die heat spreader13is shown. As illustrated, the heat spreader13is stacked right on the chip11inside the encapsultant10so that the major heat-dissipating pathway is directed upward through the open side200of the encapsultant10. However, in this example, the heat spreader13is still buried in the encapsultant10so that the overall heat-dissipation efficiency promoted by including the heat spreader13is obviously not satisfied.

Referring now toFIG. 5, another type of exposed drop-in heat spreader is shown in a BGA IC package. As illustrated, the exposed drop-in heat spreader13bridges over the chip11in the encapsultant10and has both ends foot on the pad12. Also, the top surface of the heat spreader13is exposed to the open side200of the IC package1. By proving the heat spreader13ofFIG. 5, it is apparent that the heat conducted by the heat spreader13can be easily transferred to the atmosphere through the open side200of the IC package1(precisely, through the top surface of the heat spreader13). However, the heat generated by the chip11can be transferred to the heat spreader13only through the poor-conductivity material of the encapsultant10between the heat spreader13and the chip11. Definitely, upon such an arrangement, though the difficulty for the heat to dissipate from the IC package1to the surroundings is eased, yet the difficulty for the heat to be conveyed out from the chip11through the encapsultant's material or the pad12still remains. Empirically, the hope of increasing overall heat dissipation of the IC package1by including the heat spreader13as shown inFIG. 5is sadly vague.

In the technique shown inFIG. 1toFIG. 3, heat dissipation of the IC package1is mainly interfaced through the heat spreader13or the pad12at the PCB side100. On the other hand, heat dissipation of the IC package1inFIG. 4orFIG. 5is mainly through the heat spreader13at the open side200. No matter whether the packing of the IC package1is a BGA or a PQFP, the mold-cavity consideration in molding the packing restricts itself to an encapsultant10with a limited volume which just can't accommodate a satisfied heat spreader13. Also, it is well known in the art that the involvement of any heat spreader13, described above, in an IC package1can only have an enhanced heat dissipation capability by a maximum 20% increase. Therefore, it is usually seen in application that an external heat sink or an impinging fan is introduced to expedite the heat dissipating from the IC package1to the surroundings.

Referring now toFIG. 6, an IC package1(say the one ofFIG. 1) integrates a heat sink2, or called as a heat-dissipation fin, at the open side200of the encapsultant10is shown. The heat sink2for providing the IC package1a broader heat dissipation surface is set onto the open side200with a sandwiched adhesive pad3. Upon such an arrangement, it is clear to see that two heat-transfer retarders exist in this combination to slow down the overall heat dissipation efficiency. One retarder is still the poor-conductivity encapsultant10, and the other is the adhesive pad3which forms substantial contact thermal resistance between the encapsultant10and the heat sink2.

Therefore, it is always appreciated in the art that an improvement to increase the heat dissipation capability of the IC package1can be provided.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide an IC package with an implanted heat-dissipation fin which can dissipate the heat generated by the chip directly by heat conduction to the surroundings through the solid-contact heat-dissipation fin and thereby which can enhance greatly the overall heat dissipation capability of the IC package.

It is another object of the present invention to provide a method for implanting a heat-dissipation fin while packing an IC chip, particularly during a curing of a dispensing molding process, which can integrate a heat-dissipation fin as a piece with an encapsultant of the IC package.

The IC package with an implanted heat-dissipation fin according to the present invention comprises an encapsultant having a PCB side and an opposing open side, a chip held inside the encapsultant, and a heat-dissipation fin implanted in the encapsultant with a portion thereof extending outside the open side. By providing the IC package of the present invention, a broader and more rapid heat-dissipating pathway for the heat generated by the chip can be obtained.

In one embodiment of the present invention, the heat-dissipation fin can contact directly with the chip so that a solid heat conduction relationship can be established in between.

In one embodiment of the present invention, the heat-dissipation fin and the chip can be kept apart inside the encapsultant by a predetermined spacing.

In one embodiment of the present invention, the portion of the heat-dissipation fin outside the encapsultant can further provide at least a hookup point for further hanging or mounting purposes.

According to the present invention, the method for implanting a heat-dissipation fin while packing an IC chip comprises a step of having a chip encapsulated inside an encapsultant at a melted state, a step of implanting a heat-dissipation fin into the encapsultant at a predetermined position above the chip and with a portion of the heat-dissipation fin left outside the encapsultant before the encapsultant is cured, and a step of holding in position the encapsultant and the heat-dissipation fin till the encapsultant is cured.

In the method of the present invention, the predetermined position related to the chip and the heat-dissipation fin can be a solid contact state or a position with a predetermined spacing.

All these objects are achieved by the IC package with an implanted heat-dissipation fin described below.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention disclosed herein is directed to an IC package with an implanted heat-dissipation fin. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention.

In the following description, elements that have same function but slight different shapes will be labeled by the same number and identical name so as to ensure overall consistency.

Referring now toFIG. 7AandFIG. 7B, a schematic cross-sectional view and a top view of a preferred embodiment of the IC package with an implanted heat-dissipation fin are shown, respectively. In this embodiment, the IC package6comprises an encapsultant10having a PCB side100and an opposing open side200, a chip11upheld by a pad12inside the encapsultant10, and a heat-dissipation fin61implanted in the encapsultant10with a portion thereof extending outside the open side200of the encapsultant10.

As shown, the heat-dissipation fin61of the present invention can be wider than the encapsultant10. The bottom portion613of the heat-dissipation fin61is buried into the encapsultant10while The opposing upper portion614of the heat-dissipation fin61is extended into the open space above the open side200of the IC package6. In particular, the upper portion614of the heat-dissipation fin61includes at least a plurality of fins and occupies an area, view from a top position, broader than the encapsultant10does. Thereby, the heat generated by operating the chip11can be directly transferred by conduction to the upper portion614of the heat-dissipation fin61and then dissipates into the open space above the IC package6. It is noted that a broader and more rapid heat-dissipating pathway for the IC package6of the present invention is obtained by reducing the importance of the encapsultant10in heat dissipation to a minimum.

As illustrated, the embodiment shown inFIG. 7AandFIG. 7Bis an IC package of a PQFP packing. Yet, the technique of the present invention can be still easily applied to an IC package of a BGA packing.

Referring now toFIG. 8, another preferred embodiment of the IC package with an implanted heat-dissipation fin in accordance with the present invention is shown. In this embodiment, two feet611that form part of the bottom portion613of the heat-dissipation fin61foot on the pad12while the upper portion614protrudes beyond the open side200of the IC package6. In particular, in this embodiment, the heat-dissipation fin61bridges over the chip11by these two feet611of the bottom portion613. Thereby, the major heat pathway from the chip11to the surroundings includes the pad12as well as the heat-dissipation fin61.

In the present invention, the position relationship between the chip11and the heat-dissipation fin61inside the encapsultant10can be a solid contact state as shown inFIG. 7Aor a position with a predetermined spacing S as shown inFIG. 8.

As shown inFIG. 8, the upper portion614of the heat-dissipation fin61can further include at least a hookup point612. The hookup point612can be formed as a hole as shown inFIG. 8, a protrusion, an indent, or any that can provide further hanging or mounting purposes. By providing the hookup point612of the present invention, the IC package6can then mount extension heat-dissipation accessories such as a connection metal to the casing, a connecting arm extending to another heat-dissipation fin, a impinging fan, a heat-pipe structure, a water-cooling structure, or any the like.

Referring now toFIG. 9, a flowchart of a method for implanting a heat-dissipation fin while packing an IC chip in accordance with the present invention is shown. The method, targeted to manufacture the IC package described above, includes a dispensing process300of the encapsultant material and a following curing process400. After the dispensing process300, the encapsultant burying the chip is actually at a melted state. And, only after the curing process400, the encapsultant can then be cured or, say, solidified. As shown, the curing process400includes a step401of beginning to cure when the encapsultant is still at a soft melted state, a step402of implanting a heat-dissipation fin into the encapsultant at a predetermined position above the chip and with a portion (in particular, the upper portion described above) of the heat-dissipation fin left outside the encapsultant before the encapsultant is cured, and a step403of holding in position the encapsultant and the heat-dissipation fin till the encapsultant is cured. Definitely, proper tooling should be used in these processes to avoid any unexpected displacement of the heat-dissipation fin.

In the present invention, the chip is obviously set in advance prior to the dispensing process300which proceeds to encapsulate the chip by the melted encapsultant material.

Apparently, in the preceding paragraph, several processes other than the dispensing process300and the curing process400for completely manufacturing an IC package are omitted herein. The reason for such omitting is because those processes are well known to the skilled person in the art and the improvement of the present invention does focus only on the curing process400.

Similarly, in the method of the present invention, the predetermined position related to the chip and the heat-dissipation fin inside the encapsultant can be a solid contact state or a position with a predetermined spacing.

According to the present invention, the method for implanting a heat-dissipation fin while packing an IC chip can be applied to manufacturing an IC package of a PQFP packing, a BGA packing, or any other type of packing.

In the method of the present invention, the curing process400for solidifying the encapsultant of the IC package can be better performed under a proper control upon the operation temperature and the pressure. However, this control is well known in the art and thus will be omitted herein.

In the step402of implanting the heat-dissipation fin into the encapsultant, the heat-dissipation fin can be held in position by landing the bottom portion onto the chip as shown inFIG. 7A, by footing on the pad as shown inFIG. 8, or by using any jig that is suitable to be applied to the operation environment of carrying out the curing process400.

In the present invention, the heat-dissipation fin can be a one-piece structure, or can be a combination of two separate parts. In an embodiment of the latter, the heat-dissipation fin can be separated to a bottom portion and an upper portion for being screwed with the bottom portion to make an integrated part. The bottom portion can be molded in the encapsultant in manufacturing the IC package but shall leave an exposed place to connect with the upper portion while in application. Yet, the embodiment of two-piece heat-dissipation fin described above still needs to be formed integrally as the former one-piece structure while in application. Thus, the technique of multiple-piece heat-dissipation fin shall be still in the scope of the present invention.

To show the superiority of the present invention, a typical simulation is presented to compare the heat-dissipation capacity between an IC package with a conventional add-in heat sink as shown inFIG. 6and an IC package with an implanted heat-dissipation fin as shown inFIG. 7A(but, both are BGA packed). Following are assumptions for this simulation.1. Material for the heat sink: aluminum made, 40×40×8.5 mm;Material for the heat-dissipation fin: aluminum made, 40×40×8.5 mm, with 0.5 mm high of bottom protrusion to the chip;2. Adhesive pad for the heat sink: thermal grease;3. Chip for both: power 3.5 watt, 8.24×8.06×0.325 mm4. Packing for both: BGA, 35×35×0.56 mm, with a four-layer base;5. PCB for both: 100×100×1.6 mm, four layers; and6. Boundary for both: environmental temperature 45° C., natural convention flow.

The simulation results are as follow.1. IC package with the conventional add-in heat sink: chip temperature 93.9° C., thermal resistance 13.97° C./W; and2. IC package with the implanted heat-dissipation fin: chip temperature 81.9° C. (12° C. low), thermal resistance 10.54° C./W (reduced by 24.55%).

From this simulation, the superiority of the present invention over the convention design is clear.

By providing the implanted heat-dissipation fin to the IC package in accordance with the present invention, following advantages can be obtained.

1. The heat generated by operating the chip can be rapidly and easily dissipated to the surroundings by the implanted heat-dissipation fin which can be sized certainly in advance to meet the application situation.

2. No adhesive pad is required so that the thermal resistance can be kept at an acceptable level.

3. Hookup points can provide further extension usage to additional heat-dissipation facilities.

4. The upper portion can be purposely designed to locate away from possible heat spots so that no specific consideration upon the PCB or the main board is required.

5. The heat-dissipation fin is easily implanted into the encapsultant by utilizing the soft melted state of the encapsultant in curing.

6. From the simulation results, it is quite certain that the present invention can provide the chip with a lower operation temperature.