The present invention relates to a package structure, especially a package structure wherein a die is not connected to a lead frame so that the parasitic resistance and inductance are reduced, and as such the lead frame can even be omitted.
There is a problem that the QFN package needs to face. The lead frame 102 may cause high parasitic resistance and high parasitic inductance during transmitting signals. Referring to
Referring to
Regarding heat dissipation in the package structure, a typical prior art approach is to dispose an additional heat dissipation material on the die on the lead frame to enhance the heat dissipation capability. For instance,
In view of the aforementioned drawback in the prior arts, the present invention provides a package structure wherein the lead frame is omitted to significantly reduce the parasitic resistance and inductance caused by the lead frame, and further to provide a high heat dissipation efficiency in the package structure.
In one perspective, the present invention provides a package structure, which can greatly reduce the parasitic resistance and inductance as compared to the prior art, and at the same time have the performance of high heat dissipation efficiency. The package structure of the present invention includes: a heat dissipation substrate; at least one die, each die including a signal transmitting side and a heat conduction side, wherein the signal transmitting side and the heat conduction side are two opposite side to each other, and the heat conduction side is disposed on and in contact with the heat dissipation substrate; a plurality of metal bumps, disposed on the signal transmitting side; and a package material, encapsulating the die, a side of the heat dissipation substrate in contact with the die, and the metal bumps, wherein a portion of each metal bump is exposed outside the package material.
In one embodiment, the signal transmitting side has no signal connection with the lead frame.
In one embodiment, the heat dissipation substrate is made of a high thermal conductive material.
In one embodiment, the heat dissipation substrate has aside which is exposed to the outside of the package structure, and this exposed side has a planar shape, a wavy surface, or has a matrix of one or more geometric shapes.
In one embodiment, a heat dissipation path between the die and the outside of the package structure is formed through the heat conduction side of the die and the heat dissipation substrate, to transfer a heat energy generated by the die to the outside of the package structure.
In one embodiment, the metal bumps are electrically connected to an external circuit board or a redistribution layer.
In one embodiment, the metal bumps are fabricated by an electroplating process or a ball mounting process. The material of the metal bumps includes a metal, an alloy, or a composite material structure.
In one embodiment, the package structure includes a plurality of dies, wherein the metal bumps are disposed on the signal transmitting sides of the dies, and the heat conduction sides of the dies are disposed on the heat dissipation substrate.
In one embodiment, the package structure further includes a plurality of routing lines disposed on the package material for transmitting signals between the metal bumps. The package structure further includes a stack package layer to encapsulate the routing lines and the package material.
In one perspective, the present invention provides a package method, which includes: providing at least one die, each die including a signal transmitting side and a heat conduction side, wherein the signal transmitting side and the heat conduction side are two opposite side to each other; disposing a plurality of metal bumps on the signal transmitting side; disposing a heat dissipation substrate under and in contact with the heat conduction side; providing a package material to encapsulate the at least one die on the heat dissipation substrate and to encapsulate the metal bumps; and after the step of providing a package material to encapsulate the at least one die on the heat dissipation substrate and to encapsulate the metal bumps, cutting to separate the at least one die, the heat dissipation substrate and the metal bumps from other portions to form at least one package unit, wherein each package unit includes the at least one die, the metal bumps, a post-cut heat dissipation substrate, and a post-cut package material.
In one embodiment, the aforementioned at least one die includes: a die, a plurality of dies, or a plurality of dies on a wafer.
In one embodiment, the at least one die includes a plurality of dies, wherein the metal bumps are disposed in the signal transmitting side of each die, and the heat conduction side of each die is disposed on the heat dissipation substrate; wherein the package method further includes: disposing a plurality of routing lines on the package material to respectively connect the metal bumps; and disposing a stack package layer to encapsulate the routing lines on the package material.
In one embodiment, after the step of providing a package material to encapsulate the at least one die on the heat dissipation substrate and to encapsulate the metal bumps, the package method further includes: grinding the package material and the metal bumps; and performing a reflow step to recover tops of the metal bumps.
In one embodiment, the heat dissipation substrate is disposed on a carrier layer, and the package method further includes: after each package unit is formed, removing the package unit from the carrier layer.
The objectives, technical details, features, and effects of the present invention will be better understood with regard to the detailed description of the embodiments below, with reference to the attached drawings.
The drawings as referred to throughout the description of the present invention are for illustration only, to show the interrelations between the components or units, but not drawn according to actual scale of sizes.
Compared with the prior packaging technology, the present invention omits the lead frame, so that the package structure has lower parasitic resistance and inductance. The heat dissipation substrate provides both functions for disposing the die and for heat dissipation, so that the package structure and the manufacturing process are simplified while the signal transmission efficiency is improved.
In the prior art, the lead frame needs to provide both functions of signal transmission and heat dissipation, that is, the signal transmitting side and the heat conduction side of the die are on the same side. In the present invention, the signal transmitting side 421 and the heat conduction side 422 of the die 42, are not on the same side of the die 42, but on opposite sides to each other. The signal transmitting side 421 has no signal connection with the lead frame. In some embodiments of the present invention, the package structure does not include the lead frame.
In one embodiment, the heat dissipation substrate 41 is made of a high thermal conductive material. The material of the heat dissipation substrate 41 can include a metal (for example, copper or aluminum), a ceramic material, an alloy (for example, aluminum copper alloy), or a composite structure (for example, nickel-coated copper, or graphene-coated copper plate).
In some embodiments, a side of the heat dissipation substrate 41 exposed to the outside of the package structure 40 (that is, the side opposite to the side of the heat dissipation substrate 41 connected to the die 42) is of a planar shape (for example: plane with a solid body, or plane with hollow pipes under (
In one embodiment, a heat dissipation path between the die 42 and the outside of the package structure 40 is formed through the heat dissipation substrate 41 and the heat conduction side 422 of the die 42, to transfer the heat energy generated by the die 42 to the outside of the package structure 40. Thus, besides reducing the parasitic resistance and inductance, the package structure 40 according to the present invention further has a better heat dissipation effect over the prior art package structure with lead frame. The material, thickness or shape of the heat dissipation substrate 41 can be flexibly determined to achieve a much better heat conduction and heat transfer efficiency, as compared to the prior art lead frame technology which is relatively more limited under the manufacturing requirements.
In embodiments as shown in
In one embodiment as shown by the package structure 50 of
In embodiments as shown in
In one embodiment, the metal bump 43 can be fabricated on the signal transmitting side 421 by an electroplating process or a ball mounting process. The material of the metal bumps 43 can include: metal (for example, tin, or copper), alloys (for example, tin silver alloy, or tin lead alloy), or composite structure (for example, copper in combination with tin silver alloy).
The package structure of the present invention can be applied to modify the prior art QFN package structure, and other prior art package structures. The aforementioned QFN package is one example for this modification, and the application of the present invention is not limited to the QFN package; any package structure with lead frame can be modified according to the present invention to omit the lead frame, and to use the heat dissipation substrate as proposed by the present invention.
In one perspective,
In one embodiment, when the heat dissipation substrate 41 is a flexible material, the heat dissipation substrate 41 can be pre-disposed on a carrier layer 46 (
In one embodiment, the at least one die in the package method can include: a die, a plurality of dies, or a plurality of dies on a wafer.
In one embodiment, one package unit PU can include multiple dies. In one embodiment as shown in
In one embodiment, after the above-mentioned step of encapsulating the die 42a, 42b, 42c and the metal bumps 43 (or after the step of encapsulating the stack package layer 49 and the metal stack bumps 48), the exposed surface on the package structure may need to be planarized by grinding (or polishing). However, this grinding or polishing step may damage the metal bumps 43 (or the metal stack bumps 48). Therefore, after the aforementioned step of encapsulating the dies 42a, 42b, 42c and the metal bumps 48 (or after the step of encapsulating the stack package layer 49 and the metal stack bumps 48), when a step of grinding the package material 44 and the metal bumps 43 (or grinding the stack package layer 49 with metal stack bumps 48) is required, after the grinding step, a reflow step can be performed to recover the tops of the metal bumps 43 (or the tops of metal stack bumps 48), wherein the tops of the metal bumps or of the metal stack bumps 4843 are tops of exposed to the outside of the package material 44.
The present invention has been described in considerable detail with reference to certain preferred embodiments thereof. It should be understood that the description is for illustrative purpose, not for limiting the broadest scope of the present invention. An embodiment or a claim of the present invention does not need to achieve all the objectives or advantages of the present invention. The title and abstract are provided for assisting searches but not for limiting the scope of the present invention. Those skilled in this art can readily conceive variations and modifications within the spirit of the present invention. For example, two or more of the embodiments can be used together, or, a part of one embodiment can be used to replace a corresponding part of another embodiment. For example, the package structure is provided with a different number of dies to the drawings, or the components are placed in a different sequence, or the shapes of the components are different from the drawings, etc. In view of the foregoing, the spirit of the present invention should cover all such and other modifications and variations, which should be interpreted to fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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111102577 | Jan 2022 | TW | national |
The present invention claims priority to provisional application 63/282,574 filed on Nov. 23, 2021, and TW 111102577 filed on Jan. 21, 2022.
Number | Date | Country | |
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63282574 | Nov 2021 | US |