A stacked packaging structure and its fabrication method

Abstract

This invention relates to a stacked packaging structure and its manufacturing method. The manufacturing method includes the following steps: providing a first printed circuit board (PCB) and a second PCB; providing interconnect metal pillars, including a top metal pillar integrally formed from top to bottom, at least one intermediate metal pillar, and a bottom metal pillar, wherein the diameter of the top metal pillar is larger than the diameter of its directly adjacent intermediate metal pillar, and the diameter of the bottom metal pillar is larger than the diameter of its directly adjacent intermediate metal pillar; soldering the end of the top metal pillar to a pad on the first PCB, and soldering the end of the bottom metal pillar to a pad on the second PCB; filling the space between the first and second PCBs with a molding compound, such that the molding compound adheres to the surfaces of the first and second PCBs and the outer surfaces of the interconnect metal pillars. This invention solves the problem of easy delamination between the metal interconnect pillars and the molding compound in stacked packaging structures.

Description

Technical Field

[0001] This invention relates to the field of chip packaging technology, and in particular to a stacked packaging structure and its manufacturing method. Background Technology

[0002] In the prior art, the stacked packaging structure is formed by stacking two or more printed circuit boards together. There are various interconnection methods between the circuit board modules. One of them is to use copper pillars (i.e. metal interconnect pillars) as circuits to connect the upper and lower printed circuit boards so that they are electrically interconnected.

[0003] During the reliability verification and product use of the stacked package structure, a problem was found where the metal interconnect pillars and the molding compound in the stacked package structure had poor adhesion, resulting in delamination between the two. On the other hand, when soldering the metal interconnect pillars to the printed circuit board, the solder at the end of the metal interconnect pillars crawls along the outer surface of the metal interconnect pillars, resulting in less solder at the solder joint between the metal interconnect pillars and the printed circuit board. This worsens the adhesion between the solder on the surface of the metal interconnect pillars and the molding compound, exacerbating the risk of delamination between the molding compound and the metal interconnect pillars.

[0004] Therefore, how to solve the problem of easy delamination between metal interconnect pillars and molding compound in stacked packaging structures has become an urgent issue to be addressed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a stacked packaging structure and its manufacturing method to solve the problem of easy delamination between the metal interconnect pillars and the molding compound in the stacked packaging structure.

[0006] In a first aspect, the present invention provides a method for manufacturing a stacked packaging structure, the method comprising the following steps:

[0007] Provide a first printed circuit board and a second printed circuit board;

[0008] An interconnected metal column is provided, the interconnected metal column comprising a top metal cylinder integrally formed from top to bottom, at least one intermediate metal cylinder, and a bottom metal cylinder, wherein the diameter of the top metal cylinder is larger than the diameter of the intermediate metal cylinder directly adjacent to it, and the diameter of the bottom metal cylinder is larger than the diameter of the intermediate metal cylinder directly adjacent to it.

[0009] The top cylindrical end of the interconnect metal pillar is soldered to a pad on a first printed circuit board, and the bottom cylindrical end of the interconnect metal pillar is soldered to a pad on a second printed circuit board.

[0010] A molding compound is filled between the first printed circuit board and the second printed circuit board, so that the molding compound adheres to the surface of the first printed circuit board, the surface of the second printed circuit board, and the outer surface of the interconnecting metal pillars.

[0011] Optionally, the intermediate metal cylinder includes at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, and is connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder.

[0012] Optionally, the first diameter is smaller than the diameter of the top metal cylinder, and the first diameter is smaller than the diameter of the bottom metal cylinder; the second diameter is larger than the first diameter.

[0013] Optionally, the second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder.

[0014] Optionally, the molding compound is made by using epoxy resin and phenolic resin as the base resin, silica powder as the filler, and various additives.

[0015] In a second aspect, the present invention also provides a stacked packaging structure, comprising:

[0016] A first printed circuit board, a second printed circuit board, and interconnect metal pillars, wherein the interconnect metal pillars include a top metal pillar integrally formed from top to bottom, at least one intermediate metal pillar, and a bottom metal pillar, wherein the diameter of the top metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it, and the diameter of the bottom metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it.

[0017] The top cylindrical end of the interconnecting metal pillar is connected to the pad on the lower surface of the first printed circuit board, and the bottom cylindrical end of the interconnecting metal pillar is connected to the pad on the upper surface of the second printed circuit board.

[0018] A molding compound is disposed between the first printed circuit board and the second printed circuit board, and the molding compound is bonded to the lower surface of the first printed circuit board, the upper surface of the second printed circuit board, and the outer surface of the interconnecting metal pillar.

[0019] Optionally, the intermediate metal cylinder includes at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, and is connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder.

[0020] Optionally, the intermediate metal cylinder includes at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, and is connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder.

[0021] Optionally, the second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder.

[0022] Optionally, the molding compound may be granular, liquid, or film-type.

[0023] The above solution has the following beneficial effects:

[0024] The stacked packaging structure and manufacturing method of this embodiment, by setting an integrally formed top metal cylinder, middle metal cylinder, and bottom metal cylinder, constitutes an interconnecting metal pillar for connecting the first printed circuit board and the second printed circuit board. This can prevent solder from creeping to the outer surface of the interconnecting metal pillar when soldering the interconnecting metal pillar to the printed circuit board, so that the molding compound and the interconnecting metal pillar are tightly bonded. It can also increase the bonding area and spatial contact structure between the molding compound and the interconnecting metal pillar after the molding compound is filled, thereby enhancing product reliability. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for manufacturing a stacked packaging structure provided in one embodiment of the present invention;

[0026] Figure 2 This is a diagram of an interconnected metal pillar structure provided in one embodiment of the present invention;

[0027] Figure 3 This is a diagram of another interconnected metal pillar structure provided in one embodiment of the present invention;

[0028] Figure 4 This is a diagram of another interconnected metal pillar structure provided in one embodiment of the present invention;

[0029] Figure 5 This is a diagram of another interconnected metal pillar structure provided in one embodiment of the present invention;

[0030] Figure 6 This is a diagram of a stacked packaging structure provided in one embodiment of the present invention;

[0031] The symbols are explained as follows:

[0032] 21. Top metal cylinder; 22. Middle metal cylinder; 23. Bottom metal cylinder; 220. First middle metal cylinder; 221. Second middle metal cylinder; 222. First middle metal cylinder; 223. Second middle metal cylinder; 224. First middle metal cylinder; 1. First electronic component; 2a. First printed circuit board; 2b. Second printed circuit board; 3. Second electronic component; 5. Molding compound; 6. Solder; 7. Interconnect metal cylinder. Detailed Implementation

[0033] To make the technical problems solved by the present invention, the technical solutions and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] It should be understood that the embodiments described below represent essential information to enable those skilled in the art to implement the embodiments and to illustrate the best mode of implementation. Upon reading the following description in conjunction with the accompanying drawings, those skilled in the art will understand the concepts of this disclosure and recognize the applications of these concepts not specifically mentioned herein. It should be understood that these concepts and applications fall within the scope of this disclosure and the appended claims.

[0035] It should also be understood that although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of this disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] It should also be understood that when a component is referred to as "connected" or "coupled" to another component, it can be directly connected or coupled to the other component, or there may be intermediate components. Conversely, when an element is referred to as "directly connected" or "directly coupled" to another element, there are no intermediate components.

[0037] It should also be understood that the terms “upper,” “lower,” “left,” “right,” “front,” “back,” “bottom,” “middle,” “center,” “top,” etc., may be used herein to describe various elements, indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, these elements should not be limited by these terms.

[0038] These terms are used only to distinguish one element from another. For example, a first element may be referred to as the “upper” element, and similarly, a second element may be referred to as the “upper” element depending on the relative orientation of these elements, without departing from the scope of this disclosure.

[0039] To be further understood, the terms “comprising,” “including,” “including,” and / or “include” as used herein specify the presence of the said feature, integer, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0040] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that the terms used herein should be interpreted as having the same meaning as they mean in the context of this specification and related art, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0041] In one embodiment, a method such as Figure 1 The method for fabricating the stacked packaging structure shown includes the following steps:

[0042] S101, Provide a first printed circuit board and a second printed circuit board;

[0043] In this step, both the first and second printed circuit boards are single-layer circuit boards, and the main material is copper-clad laminate. The copper-clad laminate is composed of a substrate, copper foil and adhesive. The substrate is an insulating layer board composed of polymer synthetic resin and reinforcing materials. Depending on the insulating material, the substrate can be a paper substrate, a glass cloth substrate or a synthetic fiber board.

[0044] S102. Provide interconnecting metal pillars, the interconnecting metal pillars comprising a top metal pillar integrally formed from top to bottom, at least one intermediate metal pillar, and a bottom metal pillar, wherein the diameter of the top metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it, and the diameter of the bottom metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it.

[0045] In one example, the interconnected metal pillar structure provided in this step is as follows: Figure 2As shown, the structure includes a top metal cylinder 21, a middle metal cylinder 22, and a bottom metal cylinder 23. The diameter of the middle metal cylinder 22 is smaller than that of both the top and bottom metal cylinders 21 and 23. This diameter design increases the contact area between the molding compound and the interconnecting metal cylinder structure in subsequent steps. Therefore, it is necessary to ensure that the diameter of the middle metal cylinder 22 is minimized. Optionally, the diameters of the top and bottom metal cylinders 21 can be the same or different.

[0046] In one example, the interconnected metal pillar structure provided in this step is as follows: Figure 3 As shown, it includes a top metal cylinder 21, a first intermediate metal cylinder 220, a second intermediate metal cylinder 221, and a bottom metal cylinder 23. The first intermediate metal cylinder 220 is an intermediate metal cylinder directly adjacent to the top metal cylinder 21, and its diameter is smaller than that of the top metal cylinder 21. The second intermediate metal cylinder 221 is an intermediate metal cylinder directly adjacent to the bottom metal cylinder 23, and its diameter is smaller than that of the bottom metal cylinder 23. Furthermore, the diameter of the first intermediate metal cylinder 220 is not equal to the diameter of the second intermediate metal cylinder 221.

[0047] and Figure 2 compared to, Figure 3 The purpose of placing two intermediate metal cylinders 220 and 221 between the top metal cylinder 21 and the bottom metal cylinder 23 is to further increase the contact area between the molding compound and the interconnecting metal cylinder structure in subsequent steps. Optionally, the diameter of the first intermediate metal cylinder 220 can be larger than the diameter of the second intermediate metal cylinder 221, or the diameter of the first intermediate metal cylinder 220 can be smaller than the diameter of the second intermediate metal cylinder 221.

[0048] In other examples, n intermediate metal cylinders can be set, where n>2. The n intermediate metal cylinders are connected sequentially, with the first intermediate metal cylinder connecting to the top metal cylinder and the last intermediate metal cylinder connecting to the bottom metal cylinder. Furthermore, some of the intermediate metal cylinders can have the same diameter, while the remaining intermediate metal cylinders can have different diameters, as long as the diameters of two adjacent connected intermediate metal cylinders are different. This can maximize the contact area between the molding compound and the interconnecting metal cylinder structure in subsequent steps.

[0049] S103. The top cylindrical end of the interconnect metal pillar is soldered to the pad on the first printed circuit board, and the bottom cylindrical end of the interconnect metal pillar is soldered to the pad on the second printed circuit board.

[0050] In this step, the top cylindrical metal end of the interconnect metal pillar is soldered to a pad on the first printed circuit board using solder, and the bottom cylindrical metal end of the interconnect metal pillar is soldered to a pad on the second printed circuit board. Specifically, the soldering process can include: flux spraying, circuit board preheating, dip soldering, and drag soldering.

[0051] S104. Fill the space between the first printed circuit board and the second printed circuit board with molding compound, so that the molding compound adheres to the surface of the first printed circuit board, the surface of the second printed circuit board, and the outer surface of the interconnecting metal pillars.

[0052] In this step, after the molding compound is filled and cured, the upper surface of the molding compound adheres to the lower surface of the first printed circuit board, and the lower surface of the molding compound also adheres to the upper surface of the second printed circuit board. The side of the molding compound can adhere to the outer surface of the interconnect metal pillar.

[0053] The method for manufacturing the stacked packaging structure in this embodiment, by setting an integrally formed top metal cylinder, middle metal cylinder, and bottom metal cylinder, constitutes an interconnecting metal pillar for connecting the first printed circuit board and the second printed circuit board. This can prevent solder from creeping to the outer surface of the interconnecting metal pillar when soldering the interconnecting metal pillar to the printed circuit board, making the molding compound and the interconnecting metal pillar tightly bonded. It can also increase the bonding area and spatial contact structure between the molding compound and the interconnecting metal pillar after the molding compound is filled, thereby enhancing product reliability.

[0054] In other embodiments, the intermediate metal cylinders included in the interconnecting metal pillars in step S102 specifically include: at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, which are connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect the top metal cylinder, and the last first intermediate metal cylinder is used to connect the bottom metal cylinder.

[0055] See one example. Figure 4 The interconnecting metal pillar shown includes two first intermediate metal pillars 220 and 222 and one second intermediate metal pillar 221. In other examples, the intermediate metal pillar may also include N first intermediate metal pillars and N-1 second intermediate metal pillars, where N>2. The first and second intermediate metal pillars are arranged alternately, such that the two ends of the second intermediate metal pillars are respectively connected to a first intermediate metal pillar. Except for the first and last first intermediate metal pillars, the two ends of the first intermediate metal pillars at other positions are respectively connected to a second intermediate metal pillar.

[0056] In this embodiment, the number N of the first intermediate metal cylinders can be reasonably set according to the requirements to balance increasing the contact area between the filling molding compound and the interconnecting metal cylinder structure, as well as the size and cost of the stacked packaging structure.

[0057] In other embodiments, the first diameter is smaller than the diameter of the top metal cylinder and the first diameter is smaller than the diameter of the bottom metal cylinder; the second diameter is larger than the first diameter. The difference between the second diameter and the first diameter is a preset size. When multiple first and second intermediate metal cylinders are provided within the intermediate metal cylinder, the first diameters of the various first intermediate metal cylinders can be equal, unequal, or not completely equal; the second diameters of the various second intermediate metal cylinders can be equal, unequal, or not completely equal.

[0058] For example, such as Figure 5 The interconnected metal pillars shown include three first intermediate metal pillars 220, 222, and 224 and two second intermediate metal pillars 221 and 223. The diameters of the three first intermediate metal pillars 220, 222, and 224 are not equal. The first diameter of the first intermediate metal pillar 220 is smaller than the first diameter of the first intermediate metal pillar 222, and the first diameter of the first intermediate metal pillar 222 is larger than the first diameter of the first intermediate metal pillar 224. The diameters of the two second intermediate metal pillars 221 and 223 are not equal. The second diameter of the second intermediate metal pillar 221 is larger than the second diameter of the second intermediate metal pillar 223.

[0059] When the first diameters of the first intermediate metal cylinders are not completely equal, and the second diameters of the second intermediate metal cylinders are not completely equal, it is only necessary to ensure that the first diameter of each first intermediate metal cylinder with a direct adjacent connection is smaller than the second diameter of the second intermediate metal cylinder. That is, the design requirements of the intermediate metal cylinders in this embodiment can be met by connecting the first intermediate metal cylinders with narrow diameters (the same or not completely the same or completely different first diameters) and the second intermediate metal cylinders with wide diameters (the same or not completely the same or completely different second diameters).

[0060] In other embodiments, the second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder. Alternatively, the second diameter of the second intermediate metal cylinder may be greater than the diameter of either the top or bottom metal cylinder.

[0061] In other embodiments, the molding compound is made using epoxy resin and phenolic resin as the base resin, silica powder as the filler, and various additives. Furthermore, the molding compound can be granular, liquid, or film-type, and the molding method can be compression molding or vacuum lamination. When vacuum lamination is used, only film-type epoxy molding compound can be used.

[0062] In one embodiment, the following is employed: Figure 1 The method for fabricating the stacked packaging structure shown above yields a stacked packaging structure, such as... Figure 6 As shown, the stacked packaging structure includes:

[0063] A first printed circuit board 2a, a second printed circuit board 2b, and an interconnecting metal pillar 7, wherein the interconnecting metal pillar 7 includes a top metal pillar integrally formed from top to bottom, at least one intermediate metal pillar, and a bottom metal pillar, wherein the diameter of the top metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it, and the diameter of the bottom metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it.

[0064] The top cylindrical end of the interconnecting metal pillar 7 is connected to the pad on the lower surface of the first printed circuit board 2a, and the bottom cylindrical end of the interconnecting metal pillar 7 is connected to the pad on the upper surface of the second printed circuit board 2b.

[0065] A molding compound 5 is disposed between the first printed circuit board 2a and the second printed circuit board 2b. The molding compound 5 is bonded to the lower surface of the first printed circuit board 2a, the upper surface of the second printed circuit board 2b, and the outer surface of the interconnecting metal pillar 7.

[0066] The first printed circuit board 2a and the second printed circuit board 2b are respectively integrated with a number of first electronic components 1 and second electronic components 3. The first electronic components 1 may include BGA, IC chip, etc., and the second electronic components 3 may include capacitor, resistor, etc.

[0067] In this embodiment, the connection between the top metal cylindrical end of the interconnecting metal pillar 7 and the pad on the lower surface of the first printed circuit board 2a, and the connection between the bottom metal cylindrical end of the interconnecting metal pillar 7 and the pad on the upper surface of the second printed circuit board 2b, are both achieved by soldering with solder 6.

[0068] The stacked packaging structure of this embodiment, by setting an integrally formed top metal cylinder, middle metal cylinder, and bottom metal cylinder, constitutes interconnecting metal pillars for connecting the first printed circuit board and the second printed circuit board. This can prevent solder from creeping to the outer surface of the interconnecting metal pillars when soldering them to the printed circuit board, making the molding compound and the interconnecting metal pillars bond tightly. It can also increase the bonding area and spatial contact structure between the molding compound and the interconnecting metal pillars after the molding compound is filled, thereby enhancing product reliability.

[0069] In one embodiment, the intermediate metal cylinder includes at least two first intermediate metal cylinders of a first diameter and at least one second intermediate metal cylinder of a second diameter, which are connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder.

[0070] In one embodiment, the first diameter is smaller than the diameter of the top metal cylinder and the first diameter is smaller than the diameter of the bottom metal cylinder; the second diameter is larger than the first diameter.

[0071] In one embodiment, the second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder.

[0072] In one embodiment, the molding compound is granular, liquid, or film-type.

[0073] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a stacked encapsulation structure, characterized in that, The manufacturing method includes the following steps: Provide a first printed circuit board and a second printed circuit board; An interconnected metal column is provided, the interconnected metal column comprising a top metal cylinder integrally formed from top to bottom, at least one intermediate metal cylinder, and a bottom metal cylinder, wherein the diameter of the top metal cylinder is larger than the diameter of the intermediate metal cylinder directly adjacent to it, and the diameter of the bottom metal cylinder is larger than the diameter of the intermediate metal cylinder directly adjacent to it. The top cylindrical end of the interconnect metal pillar is soldered to a pad on a first printed circuit board, and the bottom cylindrical end of the interconnect metal pillar is soldered to a pad on a second printed circuit board. A molding compound is filled between the first printed circuit board and the second printed circuit board, so that the molding compound adheres to the surface of the first printed circuit board, the surface of the second printed circuit board, and the outer surface of the interconnecting metal pillars; The interconnect metal pillars are used to prevent solder from creeping to the outer surface of the interconnect metal pillars during soldering with the first printed circuit board and the second printed circuit board, so as to make the molding compound and the interconnect metal pillars tightly bonded; and to increase the bonding area and spatial contact structure between the molding compound and the interconnect metal pillars after the molding compound is filled. The intermediate metal cylinder includes at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, which are connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder. The first diameter is smaller than the diameter of the top metal cylinder, and the first diameter is smaller than the diameter of the bottom metal cylinder; the second diameter is larger than the first diameter.

2. The method for manufacturing the stacked packaging structure according to claim 1, characterized in that, The second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder.

3. The method for manufacturing the stacked packaging structure according to any one of claims 1-2, characterized in that, The molding compound is made by using epoxy resin and phenolic resin as the base resin, silica powder as the filler, and various additives.

4. A stacked packaging structure, characterized in that, include: A first printed circuit board, a second printed circuit board, and interconnect metal pillars, wherein the interconnect metal pillars include a top metal pillar integrally formed from top to bottom, at least one intermediate metal pillar, and a bottom metal pillar, wherein the diameter of the top metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it, and the diameter of the bottom metal pillar is larger than the diameter of the intermediate metal pillar directly adjacent to it. The top cylindrical end of the interconnecting metal pillar is connected to the pad on the lower surface of the first printed circuit board, and the bottom cylindrical end of the interconnecting metal pillar is connected to the pad on the upper surface of the second printed circuit board. A molding compound is disposed between the first printed circuit board and the second printed circuit board, and the molding compound is bonded to the lower surface of the first printed circuit board, the upper surface of the second printed circuit board, and the outer surface of the interconnecting metal pillars; The interconnect metal pillars are used to prevent solder from creeping to the outer surface of the interconnect metal pillars during soldering with the first printed circuit board and the second printed circuit board, so as to make the molding compound and the interconnect metal pillars tightly bonded; and to increase the bonding area and spatial contact structure between the molding compound and the interconnect metal pillars after the molding compound is filled. The intermediate metal cylinder includes at least two first intermediate metal cylinders with a first diameter and at least one second intermediate metal cylinder with a second diameter, which are connected sequentially in the arrangement order of first intermediate metal cylinder, second intermediate metal cylinder, and first intermediate metal cylinder, wherein the first first intermediate metal cylinder in the arrangement order is used to connect to the top metal cylinder, and the last first intermediate metal cylinder is used to connect to the bottom metal cylinder. The first diameter is smaller than the diameter of the top metal cylinder, and the first diameter is smaller than the diameter of the bottom metal cylinder; the second diameter is larger than the first diameter.

5. The stacked packaging structure according to claim 4, characterized in that, The second diameter is less than or equal to the diameter of the top metal cylinder, and the second diameter is less than or equal to the diameter of the bottom metal cylinder.

6. The stacked packaging structure according to any one of claims 4-5, characterized in that, The molding compound is a film type.

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