TWI796109B - Package structure and packaging method - Google Patents

Abstract

The present invention provides a package structure, which includes: a heat dissipation substrate; at least one die, each of which includes a signal transceiving side and a heat conduction side, wherein the signal transceiving side and the heat conduction side are two opposite sides on the die, and the heat conduction side is disposed on the heat dissipation substrate; a plurality of metal bumps, electrically connected to the signal transceiving side; and a package material, encapsulating the die, a side of the heat dissipation substrate connected to the die, and the metal bumps, wherein a side of each metal bump is exposed to outside of the package material.

Description

Packaging structure and packaging method

The present invention relates to a packaging structure, especially a packaging structure that omits a lead frame to reduce parasitic resistance and parasitic inductance.

Referring to FIG. 1 , it shows a package structure 100 of a quad flat no lead package (Quad Flat No Lead, QFN), which is a common package method for existing chips 101. This package method uses a lead frame 102 (Lead frame) as Carrying structure, the die 101 is connected to the lead frame 102 by soldering, and then the lead frame 102 and the die 101 on it are covered with the packaging material 104 (Molding compound), and then the die 101 and the lead wire are cut and packaged Rack 102 to generate multiple packaged units. The die 101 in the QFN package transmits signals through the exposed part of the lead frame 102 in the package unit.

In the manufacturing technology of the QFN package, the package structure has some insurmountable problems, for example, the lead frame 102 causes high parasitic resistance and high parasitic inductance. Referring to FIG. 2 , when the conduction starts, the voltage may form a ringing effect for a long time due to the parasitic resistance and inductance generated by the lead frame 102 , causing signal transmission delay. For high-frequency signals, parasitic inductance will significantly affect the impedance, and this ringing effect will be very obvious when the current value is high.

Referring to Figure 3, in order to improve this problem, a prior art approach is to use the circuit analysis package software to perform optimization calculations, straighten the right-angled corners of the original lead frame circuit, and slightly reduce the parasitic resistance by shortening the circuit length with inductance.

For the heat dissipation in the packaging structure in the prior art, a heat dissipation material is mostly provided on the die disposed on the lead frame to enhance the heat dissipation capability. For example, FIG. 4 shows a package structure 10 of US Patent No. 7,812,437, FIG. 5 shows a package structure 20 of US Patent No. 7,164,210, and FIG. 6 shows a package structure 30 of US Patent No. 7,560,309. In these patent cases, the dies 11, 21, 31 are arranged on the lead frames 12, 22, 32, covered by the packaging materials 14, 24, 34, and the heat dissipation materials 15, 31 are arranged on the dies 11, 21, 31 25, 35. Importantly, in the packaging structures 10, 20, 30, the heat dissipation materials 15, 25, 35 are placed after the dies 11, 21, 31 are arranged on the lead frames 12, 22, 32. Errors may affect the cooling of the crystal grains 11, 21, 31. The problems of high parasitic resistance and high parasitic inductance caused by the above-mentioned arrangement of the lead frame are still difficult to overcome in these patent cases.

Aiming at the shortcomings of the prior art, the present invention provides a packaging structure technology, which can greatly reduce the parasitic resistance and inductance by omitting the lead frame, and has the effect of high heat dissipation efficiency.

From one point of view, the present invention provides a packaging structure, which can greatly reduce parasitic resistance and inductance compared with the prior art, and has high heat dissipation efficiency. The packaging structure of the present invention includes: a heat conduction layer; at least one crystal grain, including a signal transceiver side and a heat dissipation side, the signal transceiver side and the heat dissipation side are opposite sides, and the heat dissipation side is arranged on the heat conduction layer; a plurality of metal bumps , arranged on the signal receiving and receiving side; and a packaging material, covering the chip, the side connected to the chip on the heat conduction layer, and a plurality of metal bumps, and exposing the side of each metal bump outside the packaging material.

In one embodiment, the signal transmitting and receiving side is not signal-connected to the lead frame.

In one embodiment, the heat conduction layer is made of a high heat conduction material.

In one embodiment, the exposed side of the heat conduction layer on the packaging structure (the side opposite to the side of the die connected to the heat conduction layer) is in a plane, undulating shape, or an arrangement matrix of various geometric shapes.

In one embodiment, the heat dissipation side of the chip forms a heat dissipation path in the package structure through the heat conduction layer, and transfers the heat energy generated by the chip to the outside.

In one embodiment, the metal bump can be electrically connected to an external circuit board.

In one embodiment, the metal bumps are manufactured by an electroplating process or a ball-planting process, and the material of the metal bumps includes a single metal, an alloy, or a composite material structure.

In one embodiment, the packaging structure includes a plurality of dies, the metal bumps are respectively disposed on the signal receiving and receiving sides of each die, and the heat dissipation side of each die is disposed on the heat conduction layer. In one embodiment, the packaging structure further has a plurality of winding wires outside the packaging material for signal connection to the metal bumps respectively, and the packaging structure further includes a packaging stack layer to cover the winding wires and the packaging material.

In another aspect, the present invention provides a packaging method, which includes: providing at least one die, each die includes a signal transceiving side and a heat dissipation side, the signal transceiving side and the heat dissipation side are opposite to each other, a plurality of metal bumps Set on the signal transceiver side; set a heat conduction layer under the heat dissipation side; provide a packaging material to cover at least one crystal grain, heat conduction layer and metal bump on the heat conduction layer; and cut at least one crystal grain and metal Bumps to form at least one package unit, wherein each package unit includes a crystal grain, a metal bump, a thermally conductive layer after dicing, and a package material after dicing.

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 aforementioned at least one die is a plurality of dies, the metal bumps are respectively arranged on the signal transmitting and receiving side of each die, and the heat dissipation side of each die is arranged on the heat conduction layer, wherein the packaging method further includes: disposing A plurality of wires are wound outside the packaging material to connect the metal bumps with respective signals; and a packaging stack layer is provided to cover the winding wires on the packaging material.

In one embodiment, after the step of covering the crystal grains and the metal bumps on the thermal conduction layer, further includes: grinding the packaging material and the metal bumps; and performing reflow to repair the metal bumps.

In one embodiment, before the step of arranging the heat dissipation side on the heat conduction layer, the heat conduction layer is disposed on a carrier; and, after each package unit is formed, each package unit is removed from the carrier.

In the following detailed description by means of specific embodiments, it will be easier to understand the purpose, technical content, characteristics and effects of the present invention.

100,10,20,30: previous package structure

101,11,21,31: Grains

102,12,22,32: lead frame

13,23: External circuit board

104,14,24,34: Packaging materials

15,25,35: heat dissipation material

40,50: package structure

41: Thermal conduction layer

42, 42a, 42b, 42c: grain

421, 42a1, 42b1, 42c1: Signal transceiver side

422,42a2,42b2,42c2: cooling side

43:Metal bump

44: Encapsulation material

45: External circuit board

46: carrier board

47: Winding

48:Metal Stack Bump

49: Package stacking layer

PU: Packaging Unit

V: vertical direction

1 to 6 show related schematic diagrams of various packaging structures in the prior art.

FIG. 7 shows a schematic diagram of a packaging structure according to an embodiment of the invention.

8, 9A to 9E show schematic diagrams of the heat conducting layer of various embodiments of the present invention.

10A to 10C show schematic diagrams of dies and metal bumps in various embodiments of the present invention.

FIG. 11 shows a schematic diagram of a packaging structure in an embodiment of the present invention.

12A to 12D are schematic diagrams showing steps of a packaging method in an embodiment of the present invention.

13A to 13E are schematic diagrams showing steps of a packaging method in an embodiment of the present invention.

14A to 14F are schematic diagrams showing steps of a packaging method in an embodiment of the present invention.

Figure 15 shows the electrical comparison results between the prior art and the present invention.

Figure 16 shows the thermal resistance comparison results of the prior art and the present invention.

The drawings in the present invention are all schematic and mainly intended to show the relationship between components of various components, and the shapes and sizes are not drawn to scale.

Compared with the previous packaging technology, the manufacturing process of this case can omit the lead frame, so that the structure has lower parasitic resistance and capacitance. The heat conduction layer also has the functions of placing the chip and providing a heat dissipation path, simplifying the structure and improving the signal. The effect of delivering efficiency and simplifying the production process.

Referring to FIG. 7 , it shows a package structure 40 proposed according to a viewpoint of the present invention, including: a heat conduction layer 41; at least one die 42, including a signal transceiver side 421 and a heat dissipation side 422, and a signal output side 421 and The heat dissipation side 422 is opposite to each other (for example, the signal transceiver side 421 and the heat dissipation side 422 in FIG. The chip is placed on the lead frame, and the chip 42 in the present invention is arranged on the heat conduction layer 41 in an upside-down manner); a plurality of metal bumps 43 are arranged on the signal sending and receiving side 421, and the chip 42 in the package structure 40 is provided by the metal The bump 43 is connected to the outside of the packaging structure 40 for signals; and a packaging material 44 covers the die 42 , the side of the thermal conduction layer 41 connected to the die 42 , and a plurality of metal bumps 43 . Wherein, one side of each metal bump 43 is exposed outside the packaging material 41 . FIG. 7 shows a package structure including one die. For the package structure including multiple dies, please refer to the descriptions of other embodiments.

In the prior art, the lead frame often has both functions of signal transmission and heat dissipation, that is, the signal receiving and receiving side of the die is the same side as the heat dissipation side. In the present invention, the signal transceiving side 421 and the heat dissipation side 422 of the die 42 are not located on the same side of the die 42 , but on opposite sides of each other, and the signal transceiving side 421 is not signally connected to the lead frame. Wherein, the package structure in some embodiments of the present invention basically has no lead frame therein.

In one embodiment, the heat conduction layer 41 is made of a high heat conduction material. The material of the thermal conduction layer 41 may include single metal (copper, aluminum, ceramics), alloy (aluminum-copper alloy), or composite material structure (nickel-clad copper, graphene coating on the surface of the copper plate).

In one embodiment, the exposed side of the heat conduction layer 41 on the packaging structure 40, that is, the side opposite to the side of the heat conduction layer 41 connected to the crystal grain 42 is a plane (for example: a solid plane, or a hollow pipeline under the plane ( FIG. 8 ) ), undulating, or a matrix of various geometric shapes (geometric shapes such as: long arc type (Fig. 9A), long square row type (Fig. 9B), long strip triangular type (Fig. 9C), independent conical protrusion columns (Figure 9D), independent square protrusions (Figure 9E), independent round protrusions, etc.). The design of the exposed side of these heat conduction layers can increase the contact area of the heat conduction layer 41 with the outside air, which has the effect of enhancing heat dissipation.

In one embodiment, the heat dissipation side 422 of the die 42 forms a heat dissipation path between the die 42 in the package structure 40 and the outside of the package structure 40 via the heat conduction layer 41 , and transfers the heat energy generated by the die 42 to the outside of the package structure 40 . In addition to reducing parasitic resistance and inductance, the packaging structure 40 has a better heat dissipation effect than the lead frame of the prior art. The heat transfer amount and heat transfer efficiency can be adjusted by the material, thickness and shape of the heat conduction layer 41. The size of the lead frame in the prior art is limited by various restrictions in the manufacturing process, and the adjustment flexibility of the heat dissipation effect is relatively limited.

Referring to FIGS. 10A, 10B, and 10C, in one embodiment, according to the projection in the vertical direction V of the signal transceiving side 421 of the die 42, the metal bump 43 can include a variety of shapes, for example: square (FIG. 10A), circular (FIG. 10B), ellipse (FIG. 10C), polygon, etc., its shape can be determined according to the requirements of manufacturing or signal connection.

Referring to FIG. 11 , in a package structure 50 of an embodiment, the metal bump 43 can be electrically connected to an external circuit board 45 (or flexible circuit board). When the distribution of the metal bumps 43 is too dense or for other reasons, the pitch between the external signal contacts can be increased by connecting with an external circuit board 34 .

Referring to FIGS. 7 and 11 , in one embodiment, the packaging material 44 fills the gaps between the metal bumps 43 . Wherein, the signal transceiving side 421 between the metal bumps 43 is filled with the packaging material 44 .

In one embodiment, the metal bump 43 can be fabricated on the signal transceiving side 421 by electroplating process or ball planting process. The material of the metal bump 43 may include a single metal (tin, copper), an alloy (tin-silver alloy, tin-lead alloy), or a composite material structure (copper+tin-silver alloy).

The package structure of the present invention can be applied to change the design of the traditional quad flat no lead package (Quad Flat No Lead, QFN), and can also be applied to the design of other traditional package structures. The aforementioned QFN package is just an example. Users are not limited to the application of QFN package. Any packaging method that can omit the lead frame and increase the design of the heat conduction layer can adopt the technology provided by the present invention. .

Referring to FIGS. 12A to 12D, in another viewpoint, the present invention provides a packaging method, which includes: providing at least one die 42 (in FIG. 12A, eight dies are used as an example for illustration), and each die Die 42 includes a signal transceiving side 421 and a heat dissipation side 422, a plurality of metal bumps 43 are arranged on the signal transceiving side 421, wherein the metal bumps 43 may include the same shape or multiple shapes; a heat conducting layer 41 is arranged on the die 42 The heat dissipation side 422 is on the bottom (FIG. 12B); a packaging material 44 is provided to cover at least one crystal grain 42 and the metal bump 43 on the thermal conduction layer 41, and one side of the metal bump 43 is exposed (FIG. 12C); and cutting (The hollow arrow shows the cutting direction) At least one die 42, the metal bump 43 and the heat conduction layer 41 are coated with the packaging material 44 (FIG. 12D) to form at least one packaging unit PU (the figure takes eight packaging units as an example) . Each packaging unit PU includes a die 42 , a metal bump 43 , a diced heat conduction layer, and a diced packaging material.

In one embodiment, when the heat conduction layer 41 is a soft material, the heat conduction layer 41 is pre-set on a carrier 46 ( FIG. 13A ). Referring to FIGS. 13B to 13D , the steps of the packaging method provided by the present invention further include: providing at least one die 42 ( FIG. 13B ), each die 42 includes a signal transceiver side 421 and a heat dissipation side 422 , and a plurality of metal bumps 43 Set on the signal transceiver side 421, wherein the metal bump 43 can include the same shape or multiple shapes; set a heat conduction layer 41 under the heat dissipation side 422 of the die 42 (FIG. 13C); provide a packaging material 44 to cover the heat conduction layer 41 on at least one crystal grain 42 and metal bump 43 (FIG. 13D); and cutting (the hollow arrow shows the cutting direction) at least one crystal grain 42, the metal bump 43 and the thermal conduction layer 41 after covering the encapsulation material 44 to form at least A packaging unit PU, each packaging unit PU is removed from the carrier 46 ( FIG. 13E ). Each packaging unit PU includes a die 42 , a metal bump 43 , a diced heat conduction layer, and a diced packaging material.

In one embodiment, the at least one die in the aforementioned packaging method includes: a die, a plurality of dies, or a plurality of dies on a wafer.

In one embodiment, the same package unit PU may include multiple dies. Referring to Figures 14A to 14F, the steps of the related packaging method provided by the present invention include: providing a plurality of dies 42a, 42b, 42c, and metal bumps 43 are respectively arranged on the signal receiving and receiving sides 42a1, 42b1, 42b1, On 42c1, the heat dissipation sides 42a2, 42b2, and 42c2 of the crystal grains 42a, 42b, and 42c are respectively arranged on the heat conduction layer 41 (FIG. 14A); a packaging material 44 is provided to cover the grains 42a, 42b, 42c and the heat conduction layer 41. Metal Bump 43 (FIG. 14B); a plurality of winding wires 47 are arranged outside the packaging material 44 to connect the metal bumps 43 with respective signals (FIG. 14C); metal stack bumps 48 are arranged on the winding wires 47 to electrically connect the winding wires 47 or electrically connected to the metal bump 43 (FIG. 14D); a packaging stack layer 49 is provided to cover the winding 47 on the packaging material 44 and the metal stack bump 48 (FIG. 14E); and cutting (the hollow arrow shows the cutting direction) The dies 42 a , 42 b , 42 c , the metal bumps 43 , the metal stack bumps 48 and the heat conduction layer 41 after the packaging stack layer 49 are covered with the packaging material 44 to form the packaging unit PU. In this embodiment, each package unit PU may include different dies 42a, 42b, 42c (FIG. 14F), wherein wires are used to connect the dies 42a, 42b, 42c.

In one embodiment, after the step of covering the dies 42a, 42b, 42c and the metal bumps 43 on the thermally conductive layer 41 (or after the step of covering the packaging stack layer 49 and the metal stack bumps 48), leveling may be required. However, this leveling process may damage the metal bump 43 (or the metal stack bump 48). Therefore, after the aforementioned step of covering the crystal grains 42a, 42b, 42c and the metal bump 48 on the heat conduction layer 41 (or after the step of covering the packaging stack layer 49 and the metal stack bump 48), it further includes: grinding the packaging material 44 and the metal bump 43 (or grinding the package stack layer 49 and the metal stack bump 48 ), and performing reflow to repair the metal bump 43 (or the metal stack bump 48 ).

Referring to FIG. 15 , it shows an electrical simulation comparison between the prior art QFN package and the package structure omitting the lead frame of the present invention. According to the comparison results, it can be seen that the resistance and inductance of the package structure of the present invention are reduced by more than 80% on average compared with the resistance and inductance of the prior art square flat no-lead package, and the effect is remarkable. Referring again to FIG. 16 , it shows a simulated comparison of the thermal resistance between the QFN package of the prior art and the package structure of the present invention omitting the lead frame. According to the comparison results, it can be seen that the thermal resistance of the package of the present invention is reduced by 0.9° C./W compared with the package thermal resistance of the prior art QFN package.

The present invention has been described above with reference to the embodiments, but the above description is only for making those skilled in the art understand the contents of the present invention easily, and is not intended to limit the scope of rights of the present invention. Within the same spirit of the present invention, various equivalent changes can be conceived by those skilled in the art. For example, The number of dies different from those shown in the drawings are arranged on the package structure, or the order of placement of components is different, or the shapes of the components are different from those shown in the drawings, etc., the scope of the present invention shall cover the above and all other equivalent changes.

40: Package structure

41: Thermal conduction layer

42: grain

421: Signal transceiver side

422: cooling side

43:Metal bump

44: Encapsulation material

Claims (15)

A packaging structure, comprising: a heat conduction layer; at least one crystal grain, including a signal transceiver side and a heat dissipation side, the signal transceiver side and the heat dissipation side are opposite sides, and the heat dissipation side is arranged on the heat conduction layer; a plurality of A metal bump is arranged on the signal receiving and receiving side; and a packaging material covers the die, the side of the thermal conduction layer connected to the die and the metal bumps, wherein one side of each metal bump is exposed on the Outside the packaging material; wherein the plurality of metal bumps and the packaging material have a flat surface on the signal receiving and receiving side; wherein the flat surface is obtained by grinding the packaging material and the metal bumps, and performing reflow ( Reflow) is formed after repairing the metal bumps. The package structure according to claim 1, wherein the signal receiving and transmitting side is not signal-connected to a lead frame. The package structure as claimed in claim 1, wherein the heat conduction layer is made of a high heat conduction material. The package structure according to claim 3, wherein the material of the thermal conduction layer comprises a single metal, alloy, or composite material structure. The package structure according to claim 3, wherein the exposed side of the heat conduction layer on the package structure is a plane, undulating, or geometrically arranged matrix. The package structure according to claim 3, wherein the heat dissipation side of the die forms a heat dissipation path in the package structure through the heat conduction layer, and transfers heat energy generated by the die to the outside. The package structure according to claim 1, wherein the metal bumps are electrically connected to an external circuit board. The package structure as claimed in claim 1, wherein the metal bump is manufactured by an electroplating process or a ball planting process. The package structure according to claim 1, wherein the material of the metal bump includes a single metal, alloy, or composite material structure. The package structure as described in Claim 1 includes a plurality of dies, the metal bumps are respectively arranged on the signal receiving and receiving side of each die, and the heat dissipation side of each die is disposed on the heat conduction layer. In the packaging structure described in claim 10, a plurality of winding wires are provided outside the packaging material to respectively connect the metal bumps with signals, and the packaging structure further includes a packaging stack layer to cover the winding wires and the metal bumps. packaging material. A packaging method, comprising: providing at least one die, each of the dies includes a signal transceiving side and a heat dissipation side, a plurality of metal bumps are arranged on the signal transceiving side; a heat conduction layer is arranged under the heat dissipation side; providing a Packaging material, coating the at least one crystal grain and the metal bumps on the heat conduction layer; cutting the coated at least one crystal grain, the heat conduction layer and the metal bumps to form at least one package unit, wherein each The packaging unit includes the at least one crystal grain, the metal bumps, the heat conduction layer after cutting, and the packaging material after cutting; after the step of covering the at least one crystal grain and the metal bumps on the heat conduction layer, grinding The packaging material and the metal bumps are reflowed to repair the metal bumps. The packaging method according to claim 12, wherein the at least one die comprises: a die, a plurality of dies, or a plurality of dies on a wafer. The packaging method as described in claim 12, wherein the at least one die is a plurality of dies, the metal bumps are respectively arranged on the signal transmitting and receiving side of each die, and the heat dissipation of each die The side is disposed on the heat conduction layer, wherein the packaging method further includes: disposing a plurality of winding wires outside the packaging material to respectively connect the metal bumps for signals; and disposing a package stacking layer to cover the packaging material on the some winding. The packaging method as claimed in claim 12, wherein the heat conduction layer is disposed on a carrier board, and the packaging method further includes: removing each of the packaging units from the carrier board after each of the packaging units is formed.

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