Stack packaging method and packaging structure

Abstract

The invention relates to the technical field of semiconductor device packaging, and discloses a stacked packaging method and a packaging structure. The stack packaging method comprises the following steps: providing a first device layer which comprises a first surface and a second surface with a plurality of first bonding pad points; forming a first conductive column at the first bonding pad point; providing a second device layer, wherein the second device layer comprises a third surface with a plurality of second bonding pad points and a fourth surface; forming an insulated and annular first box dam structure with a first accommodating space at the second bonding pad point; the first accommodating space is filled with conductive glue; the first device layer is fixed on the second device layer, and the first conductive columns are in contact with the conductive glue in the first box dam structure; and curing the conductive glue to form a first conductive glue layer which is fixedly bonded with the first conductive upright post. The first conductive columns and the conductive glue in the first box dam structure are reinforced and connected, electrical and structural interconnection is achieved, the subsequent reflow soldering process is prevented from affecting the device stacking and interconnection reliability, and stacking packaging of multiple device layers is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device packaging, and in particular to a stacking packaging method and a packaging structure. Background Art

[0002] As electronic devices are rapidly developing towards high integration, high assembly density and high operating speed, the size of semiconductor devices is required to gradually tend towards high integration and multifunctionality. 3D (Three Dimensional) packaging is widely used because of its small size and light weight, which can meet the development needs of semiconductor technology. 3D stacking technology refers to the stacking processing technology that stacks chips, devices or structures with different functions together in the vertical direction through stacking technology or micro-machining technology such as via interconnection to form a three-dimensional package with three-dimensional integration and signal connectivity. At present, 3D stacking technology mainly uses solder ball flipping for vertical interconnection in package on package (PoP) products.

[0003] Flip-chip solder balls refer to pre-placing solder balls on the product base pads by laser ball implantation or steel screen printing, and then flipping the devices or structures to be stacked on the product base, and soldering the upper and lower parts of the devices or structures together through the melting of the solder balls during the reflow process, ultimately achieving electrical and structural interconnection. However, if the devices or structures continue to be stacked upward, the reflow process of the upper layer of solder balls will remelt the solder balls of the lower layer that have already undergone the reflow process, resulting in reliability problems in the welding of the lower layer of devices and device displacement. In response to this situation, the related art uses a method of stacking layers of solder balls with different melting points. For example, the melting point of the flip-chip solder balls used in each new device layer is lower than the melting point of the flip-chip solder balls used in the lower device layer. However, this method is cumbersome in actual operation, and it is difficult to control the reflow temperature. In addition, the melting point of the solder balls is difficult to adjust at will, which is not conducive to stacking multi-layer devices. Summary of the invention

[0004] In view of this, the present invention provides a stacking packaging method and packaging structure to solve the problem that the product structure in the existing stacking packaging has poor thermal stability, the subsequent reflow process will cause remelting, and more layers of devices cannot be vertically stacked.

[0005] In a first aspect, the present invention provides a stacking packaging method, comprising:

[0006] Providing a first device layer, the first device layer comprising a first surface and a second surface arranged opposite to each other, and a plurality of first pads on the second surface;

[0007] forming a first conductive column at a first pad point on the second surface;

[0008] Providing a second device layer, the second device layer comprising a third surface and a fourth surface arranged opposite to each other, and a plurality of second pads are provided on the third surface;

[0009] Forming a first dam structure at the second pad point on the third surface, wherein the first dam structure is a ring-shaped insulating structure having a first accommodating space;

[0010] Filling the first accommodating space of the first dam structure with conductive glue;

[0011] Fixing the first device layer on the second device layer so that the second surface is arranged opposite to the third surface and the first conductive pillar contacts the conductive glue in the first dam structure;

[0012] The conductive glue in the first dam structure is cured to form a first conductive glue layer, and the first conductive glue layer is fixedly bonded to the first conductive column.

[0013] Beneficial effects: The stacking package of the first device layer and the second device layer abandons the traditional solder ball interconnection method, sets a highly conformal first conductive column on the first device layer, sets a first dam structure on the second device layer, and sets conductive glue in the first dam structure. The first dam structure plays a role in limiting the flow of the conductive glue; the first conductive column and the conductive glue in the first dam structure are reinforced during the curing process to achieve electrical and structural interconnection functions. It is important that there is no reflow problem caused by solder ball remelting in this process. Baking and curing promote the cross-linking of organic molecules inside materials such as conductive glue, turning them into a solid solid structure. Different from metal melting, there is no risk of remelting in the glue cross-linking process, which avoids the occurrence of reflow in the subsequent device layer stacking process and affects the stacking and electrical interconnection, and finally ensures reliable electrical interconnection between device layers, and finally achieves reliable stacking packaging of multi-layer device layers.

[0014] In an optional embodiment, forming a first conductive column at a first pad point on the second surface includes:

[0015] Printing conductive paste at the first pad point on the second surface in a vertically pulling manner;

[0016] The conductive paste is baked and cured to form a first conductive column.

[0017] Beneficial effects: Highly conformal conductive paste is used, and direct writing printing is used. Precise air pressure control is used to push the printing needle to precisely discharge the material, and the first conductive column is formed on the second surface of the first device layer. The free end of the first conductive column after vertical pulling and printing, that is, the first connecting end, is pointed. When such a pointed structure is interconnected with the conductive glue in the first dam structure of the second device layer, it is not easy to cause the conductive glue to overflow due to the small volume of the pointed tip. The first conductive column processed by direct writing printing is cured by baking, so that the binder inside the conductive paste is cured and cross-linked and adheres to the surface of the pad, and the metal particles fuse with each other to form conductivity. Conductive paste is different from alloy tin balls. After baking and curing, the conductive paste itself will not remelt.

[0018] In an optional embodiment, the conductive paste includes a binder and metal particles, the size of the metal particles ranges from 30 nm to 30 μm; the viscosity of the conductive paste ranges from 100,000 cps to 800,000 cps, and the thixotropic index ranges from 3 to 7.

[0019] Beneficial effect: The conductive paste is a conductive paste containing micron and nano mixed metal particles, the size range of the metal particles is limited to between 30nm and 30μm, so that it has a high conformal feature, and the metal particles can be silver, so that it has excellent conductivity and can withstand a reflow process at 260°C. Preferably, the viscosity setting and thixotropic index of the highly conformal conductive paste in this embodiment help to further enhance its shape retention ability.

[0020] In an optional embodiment, the temperature range of baking and curing the conductive paste is 100° C. to 200° C., and the time of baking and curing the conductive paste is 0.5 h to 3 h.

[0021] Beneficial effect: Under the above-mentioned baking and curing temperature range and time conditions, it is helpful to form a first conductive column with excellent shape stability and conductive performance.

[0022] In an optional implementation, forming an insulating first dam structure at the second pad point on the third surface includes:

[0023] Printing a ring-shaped insulating glue on the outer periphery of the second pad point on the third surface;

[0024] The insulating glue is baked and cured to form an insulating first dam structure.

[0025] Beneficial effects: Insulating glue, specifically epoxy encapsulation insulating glue, is used. Through direct writing printing, precise air pressure control drives the printing needle to accurately discharge the material, and the first dam structure is formed by drawing circles or frames around the second pad point on the third surface of the second device layer. The first dam structure processed by direct writing printing is cured by baking, so that in subsequent processes, the first dam structure can be reliably adhered to the second pad point on the third surface of the second device layer. Insulating glue is different from alloy solder balls. After baking and curing, it can withstand a reflow process of 260°C, and the glue itself will not remelt.

[0026] In an optional implementation, the viscosity of the insulating glue ranges from 100,000 cps to 1,000,000 cps, and the thixotropic index ranges from 2 to 7; the thixotropic index of the conductive glue in the first dam structure ranges from 2 to 7.

[0027] Beneficial effect: The viscosity setting and thixotropic index setting of the insulating glue used in the first dam structure help it have good shape retention ability. Due to the existence of the first dam structure, the conductive glue filled in the first dam structure can be a low-viscosity conductive glue, and its flow is limited to the first dam structure at the second pad point.

[0028] In an optional implementation manner, the temperature range for baking and curing the insulating glue is 100° C. to 200° C., and the time for baking and curing the insulating glue is 0.5 h to 3 h.

[0029] Beneficial effects: The limited temperature range and baking time for baking and curing the insulating glue are helpful to form a first dam structure with excellent shape stability and insulation performance.

[0030] In an optional implementation manner, the fourth surface of the second device layer has a plurality of third pads; after curing the conductive glue in the first dam structure to form the first conductive glue layer, the method further includes:

[0031] forming a second conductive column at the third pad point on the fourth surface;

[0032] Providing a third device layer, the third device layer includes a fifth surface and a sixth surface arranged opposite to each other, and a plurality of fourth pads are provided on the fifth surface;

[0033] A second dam structure is formed at the fourth pad point on the fifth surface, wherein the second dam structure is an annular insulating structure having a second accommodating space;

[0034] Filling the second accommodation space of the second dam structure with conductive glue;

[0035] Fixing the first device layer and the second device layer on the third device layer so that the fifth surface is arranged opposite to the fourth surface and the second conductive pillar contacts the conductive glue in the second dam structure;

[0036] The conductive glue in the second dam structure is cured to form a second conductive glue layer, and the second conductive glue layer is fixedly bonded to the second conductive column.

[0037] Beneficial effect: After the first device layer and the second device layer are stacked and solidified, the first device layer and the second device layer are flipped again, and the fourth surface of the second device layer is placed upward to facilitate stacking of more devices. By setting a second conductive column on the third pad point on the fourth surface of the second device layer, setting a second dam structure and filling conductive glue on one side of the fifth surface of the third device layer, and connecting the second conductive column to the conductive glue in the second dam structure, the third device layer is electrically interconnected with the first device layer and the second device layer as a whole, and finally placed in a manner that the first surface contacts the placement platform and the sixth surface faces upward, the three-layer device as a whole can be used as a new first device layer for subsequent repeated stacking.

[0038] In a second aspect, the present invention further provides a stacked packaging structure, which is manufactured by the above-mentioned stacked packaging method, comprising:

[0039] A first device layer, a first conductive column, a second device layer, a first dam structure and a first conductive adhesive layer, wherein the first device layer includes a first surface and a second surface arranged opposite to each other, and the second surface has a plurality of first pads; the first conductive column is arranged at the first pad on the second surface; the second device layer includes a third surface and a fourth surface arranged opposite to each other, and the third surface has a plurality of second pads; the second device layer is fixedly connected to the first device layer, and the third surface is arranged opposite to the second surface; the first dam structure is arranged at the second pad on the third surface, and the first dam structure is an annular insulating structure having a first accommodating space; the first conductive adhesive layer is arranged in the first accommodating space, and the first conductive adhesive layer is fixedly bonded to the first conductive column.

[0040] Beneficial effect: In the stacked packaging structure, the stacked packaging of the first device layer and the second device layer abandons the traditional solder ball interconnection method, and instead sets a highly conformal first conductive column on the first device layer, sets a first dam structure on the second device layer, and sets a first conductive adhesive layer in the first dam structure. The first dam structure ensures that the first conductive adhesive layer has a complete structure and has a good conductive connection with the first conductive column. After the first conductive column and the first conductive adhesive layer in the first dam structure are connected, such a connection avoids backflow in the subsequent device layer stacking process, which affects the stacking and electrical interconnection, thereby ensuring reliable electrical interconnection between device layers, and ultimately achieving reliable stacking packaging of multi-layer device layers.

[0041] In an optional embodiment, the fourth surface of the second device layer has a plurality of third pads; the stacked packaging structure also includes: a second conductive column, a third device layer, a second dam structure and a second conductive adhesive layer, wherein the second conductive column is arranged at the third pad on the fourth surface, and the free end of the second conductive column, i.e., the second connection end, is also formed into a pointed shape; the third device layer includes a fifth surface and a sixth surface arranged opposite to each other, the fifth surface has a plurality of fourth pads, the third device layer is fixedly connected to the second device layer, and the fifth surface is arranged opposite to the fourth surface; the second dam structure is arranged at the fourth pad on the fifth surface, and the second dam structure is an annular insulating structure having a second accommodating space; the second conductive adhesive layer is arranged in the second accommodating space, and the second conductive adhesive layer is fixedly bonded to the second conductive column.

[0042] Beneficial effect: After the stacked first device layer and the second device layer are flipped, the first surface of the first device layer contacts the placement platform, and the fourth surface is placed upward, and can be used as a new first device layer for subsequent stacking. A third pad point is arranged on the fourth surface, and a second conductive column is arranged at the third pad point. A fourth pad point is arranged on the fifth surface of the third device layer, and a second dam structure is arranged at the fourth pad point and a second conductive adhesive layer is formed in the second dam structure. The second conductive column on the fourth surface is bonded and fixed to the second conductive adhesive layer in the second dam structure to complete the stacking of the three-layer device layer. Finally, the first surface of the first device layer contacts the placement platform, and the sixth surface of the third device layer is placed upward, which is convenient for subsequent stacking of the fourth layer, the fifth layer, or even more layers of devices. The conductive columns and conductive glue that realize interconnection between the lower layer devices will not cause the problem of remelting and reflow, and the reliability of the multi-layer device stacking is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic diagram of a stacking packaging method according to an embodiment of the present invention;

[0044] Figure 2 is a schematic top view of a second surface side of a first device layer in an embodiment of the present invention;

[0045] Figure 3 is a front schematic diagram of an embodiment of the present invention after a first conductive column is disposed on a first device layer;

[0046] Figure 4 is a schematic diagram of starting to cut material using a printing needle on the first device layer according to an embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of the lifting process of the printing needle during blanking according to an embodiment of the present invention;

[0048] Figure 6is a schematic diagram of a printing needle stopping material removal and detaching on a first device layer according to an embodiment of the present invention;

[0049] Figure 7 is a schematic diagram of performing blanking printing at another printing point on the first device layer according to an embodiment of the present invention;

[0050] Figure 8 is a schematic top view of a third surface side of the second device layer of an embodiment of the present invention;

[0051] Fig. 9 is a front view schematic diagram of a second device layer in an embodiment of the present invention;

[0052] Fig.10 is a schematic diagram of flipping a first device layer and placing it on a second device layer according to an embodiment of the present invention;

[0053] Fig.11 is a schematic diagram of an embodiment of the present invention after the first device layer and the second device layer are flipped and a second conductive column is arranged on the fourth surface of the second device layer;

[0054] Fig.12 is a schematic diagram of an embodiment of the present invention in which the first device layer, the second device layer and the third device layer are turned over as a whole, and the sixth surface of the third device layer is arranged upward;

[0055] Fig.13 It is a schematic diagram showing that a fifth component is disposed on the sixth surface of the third device layer of an embodiment of the present invention.

[0056] Description of reference numerals:

[0057] 1. first device layer; 11. first surface; 12. second surface; 13. first pad point; 14. first component;

[0058] 2. a first conductive column; 21. a first connecting portion;

[0059] 3. second device layer; 31. third surface; 32. fourth surface; 33. second component; 34. third component;

[0060] 4. The first dam structure;

[0061] 5. The first conductive adhesive layer;

[0062] 6. a second conductive column; 61. a second connecting portion;

[0063] 7, third device layer; 71, fifth surface; 72, sixth surface; 73, fourth device; 74, fifth device;

[0064] 8. Second dam structure;

[0065] 100. Printing needle; 200. Conductive paste. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only some structures related to the present invention are shown in the accompanying drawings, rather than all structures. In the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified for the purpose of clear expression, and some details may be omitted. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary, and may be deviated due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. In addition, if one layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0067] In the related art, during the stacking packaging of semiconductor devices, the process of using solder balls for flip-chip stacking interconnection has poor thermal stability. The stacked and connected devices are easily affected by subsequent reflow and the electrical interconnection fails. The method of stacking layers by using solder balls with different melting points is cumbersome and difficult to control the reflow temperature, which will also cause reliability problems.

[0068] Therefore, in view of the poor reliability and complicated process of multi-layer device stacking in the above-mentioned semiconductor device stacking package, reference is made to Figures 1 to 13 , this embodiment provides a stacking packaging method, Figure 1 The flowchart of the stacking packaging method of this embodiment includes:

[0069] Step S101 , providing a first device layer 1 , wherein the first device layer 1 comprises a first surface 11 and a second surface 12 arranged opposite to each other, and the second surface 12 has a plurality of first pads 13 .

[0070] like Figure 2As shown, exemplarily, a 5mm*5mm substrate is used as the first device layer 1, and the first device layer 1 can be a silicon substrate, a gallium arsenide substrate or a metal substrate, etc. The first surface 11 of the first device layer 1 serves as the back side, and the second surface 12 serves as the front side. The second surface 12, i.e., the front side, is provided with a plurality of first solder pads 13 with a diameter of 500μm and an interval size of 750μm. The first solder pads 13 can specifically be copper solder pads.

[0071] Step S102 , forming a first conductive column 2 at the first pad 13 on the second surface 12 .

[0072] like Figure 3 As shown, a first conductive column 2 is disposed at each first pad point 13 on the second surface 12 of the first device layer 1. For example, the first conductive column 2 can be formed by using a conductive paste 200. In this embodiment, a cylindrical structure with a diameter of 200 μm and a height of 500 μm is preferred as the first conductive column 2. Of course, other sizes can also be selected without strict limitation, as long as they are adapted to the size of the first pad point 13.

[0073] Step S103 , providing a second device layer 3 , wherein the second device layer 3 comprises a third surface 31 and a fourth surface 32 which are arranged opposite to each other, and the third surface 31 has a plurality of second pads.

[0074] For example, a 5mm*5mm substrate is also used as the second device layer 3. The second device layer 3 can be a silicon substrate, a gallium arsenide substrate or a metal substrate, etc. The third surface 31 of the second device layer 3 is used as the front side, and the fourth surface 32 is used as the back side. The third surface 31, i.e. the front side, is provided with a plurality of second solder pads with a diameter of 500μm and an interval size of 750μm. The second solder pads can also be copper solder pads.

[0075] Step S104 , forming a first dam structure 4 at the second pad point of the third surface 31 , wherein the first dam structure 4 is a ring-shaped insulating structure having a first accommodating space.

[0076] A first annular dam structure 4 is provided at each second pad point on the third surface 31 of the second device layer 3. For example, the first dam structure 4 can be formed of an insulating structure using epoxy insulating glue; a first accommodation space connected to the second pad point is formed in the middle of the annular first dam structure 4 so as to form a conductive connection with the second pad point later. In this embodiment, the radial dimension of the first dam structure 4 is set to 150 μm, and the thickness is set to 100 μm.

[0077] Step S105 , filling the first accommodation space of the first dam structure 4 with conductive glue.

[0078] The second surface 12 of the first device layer 1 is facing upward and the third surface 31 of the second device layer 3 is facing upward, and then the first dam structure 4 of the second device layer 3 is filled with conductive glue to cover the entire first accommodation space of the first dam structure 4. In this embodiment, the depth of the conductive glue filled is 80μm, which is slightly lower than the depth of the first dam structure 4 to avoid glue overflow during the contact with the first conductive column 2.

[0079] Step S106 , fixing the first device layer 1 on the second device layer 3 , so that the second surface 12 and the third surface 31 are arranged opposite to each other, and the first conductive pillars 2 are in contact with the conductive glue in the first dam structure 4 .

[0080] refer to Fig.10 , flip the first device layer 1, and face the second surface 12 of the first device layer 1 provided with the first conductive pillar 2 downward, and gradually move the first conductive pillar 2 toward the second device layer 3 in alignment with the first dam structure 4 until it contacts the conductive glue and penetrates an appropriate distance, thereby increasing the contact area with the conductive glue. In this embodiment, a nozzle structure is used to absorb the first surface 11 of the first device layer 1 and pick it up and flip it, and then drive the first device layer 1 to gradually move toward the second device layer 3. After the first conductive pillar 2 contacts the conductive glue, the nozzle structure continues to press down 30 μm, so that the first conductive pillar 2 is fully in contact with the conductive glue. At this time, the conductive glue has not yet solidified, and still has a certain degree of adhesion after contacting the first conductive pillar 2, so that the first conductive pillar 2 of the first device layer 1 can be temporarily fixed.

[0081] Step S107 , curing the conductive glue in the first dam structure 4 to form a first conductive glue layer 5 , and the first conductive glue layer 5 is fixedly bonded to the first conductive column 2 .

[0082] The stacked first device layer 1 and second device layer 3 are baked and cured, so that the conductive glue in the first dam structure 4 is cured, and the first device layer 1 and the second device layer 3 are firmly stacked. Then, the stacked first device layer 1 and the second device layer 3 are placed on the platform with the first surface 11 in contact and the fourth surface 32 facing upward. The baking and curing temperature of the conductive glue is generally between 100 and 200°C, and the baking time is 0.5h to 3h. The curing temperature and curing time of different conductive glues are different and are not specifically limited. In this embodiment, the conductive glue is selected from the conductive glue with a viscosity of 3300cps and a thixotropic index of 3. The curing condition is to bake at 180°C for 60min to achieve reliable bonding between the conductive glue and the first conductive column 2. At this time, the upper and lower first device layers 1 and the second device layers 3 are stacked and merged, and can be used as a new first device layer 1 for subsequent repeated stacking.

[0083] In this embodiment, the stacking package of the first device layer 1 and the second device layer 3 abandons the traditional solder ball interconnection method, and a highly conformal first conductive column 2 is set on the first device layer 1, a first dam structure 4 is set on the second device layer 3, and a conductive glue is set in the first dam structure 4. The first dam structure 4 serves to limit the flow of the conductive glue; the first conductive column 2 and the conductive glue in the first dam structure 4 are used to reinforce the connection during the curing process. What is important is that there is no reflow problem caused by remelting of the solder balls in this process. Baking and curing promote the cross-linking of organic molecules inside materials such as the conductive glue, so that it is transformed into a solid solid structure. Different from metal melting, there is no risk of remelting in the glue cross-linking process, which avoids the risk of reflow in the subsequent device layer stacking process and affects the stacking and electrical interconnection, thereby ultimately ensuring reliable electrical interconnection between the device layers and ultimately achieving reliable stacking packaging of multiple device layers.

[0084] In one embodiment, the above step S102, forming the first conductive pillar 2 at the first pad point 13 of the second surface 12, includes:

[0085] Step S1021 , printing the conductive paste 200 at the first pad point 13 of the second surface 12 in a vertically pulling manner.

[0086] A highly conformal conductive paste 200 is used, and the printing needle 100 is pushed to precisely discharge the material by direct writing printing, and the first conductive column 2 is formed on the second surface 12 of the first device layer 1. The direct writing printing process of this embodiment can use the high-precision electronic 3D printing equipment produced by Core Element Company. According to the size of the pad point, a ceramic printing needle 100 with an inner diameter of 100μm is preferred. Figures 4 to 7 As shown, during printing, the printing needle 100 cartridge filled with high conformal conductive paste is installed in the printing device. Figure 4 , the printing needle 100 moves downward close to the first device layer 1 and is aligned with the center position of the first pad point 13 on the side of the second surface 12. The conductive paste 200 is extruded after the air pressure is turned on. The printing speed is set to 3 mm / s, the air pressure is 45 psi, and the material is unloaded when the distance from the first pad point on the side of the second surface 12 is 70 μm. At this time, the printing needle 100 is left to stand for 100 ms, and then refer to Figure 5 Gradually raise the printing needle 100 to a distance of 500 μm from the second surface, and then Figure 6 Stop discharging, and continue to lift the printing needle 100 upward until the conductive paste 200 inside the printing needle 100 is disconnected from the pillar paste, completing the printing of a first conductive pillar 2. It should be noted that at the end of each first conductive pillar 2, the printing needle 100 needs to close the feed air pressure in advance to reduce the paste accumulation at the printing needle 100 so as to continue processing the conductive pillar at the next pad position. Figure 7 The printing needle 100 moves to the next printing position for subsequent printing. Through the above steps, the free end of the printed first conductive column 2, that is, the first connecting portion 21, is pointed. When such a pointed structure is interconnected with the conductive glue in the first dam structure 4 of the second device layer 3, the conductive glue is not easily overflowed due to the small volume of the pointed first connecting portion 21.

[0087] Step S1022 , baking and curing the conductive paste 200 to form a first conductive column 2 .

[0088] The first conductive pillar 2 processed by direct writing is cured by baking, so that the binder inside the conductive paste 200 is cured and cross-linked to adhere to the surface of the pad, and the metal particles fuse with each other to form conductivity. The conductive paste 200 is different from the alloy solder ball. After baking and curing, it can withstand the reflow process of 260°C, and the conductive paste 200 itself will not remelt.

[0089] Furthermore, the conductive paste 200 includes a binder and metal particles, the size of the metal particles ranges from 30 nm to 30 μm; the viscosity of the conductive paste 200 ranges from 100,000 cps to 800,000 cps, and the thixotropic index ranges from 3 to 7.

[0090] Specifically, the conductive paste 200 is a conductive paste 200 containing a mixture of micron metal particles and nano metal particles. The size range of the metal particles is limited to between 30nm and 30μm to make it highly conformal. The metal particles can be silver to make it have excellent conductivity. Preferably, in this embodiment, the viscosity of the highly conformal conductive paste 200 is set to 550000cps and the thixotropic index is set to 5 to further enhance its shape retention ability.

[0091] The temperature range of baking and curing the conductive paste 200 is 100°C to 200°C, and the time of baking and curing the conductive paste 200 is 0.5h to 3h, so as to form a first conductive column 2 with excellent shape stability and conductive performance. Preferably, in this embodiment, the condition of baking the conductive paste 200 is specifically baking at a temperature of 200°C for 30 minutes to complete curing, which has the best effect.

[0092] In one embodiment, the aspect ratio of the first conductive pillar 2 can be greater than or equal to 5:1, and high-density solder pad interconnection can be achieved through the first conductive pillar 2. At the same time, because the height of the first conductive pillar 2 is higher than that of the traditional solder ball, the stacking gap (i.e., Gap) between layers can be larger, and components can be arranged on both sides of each layer, which can accommodate more component arrangement space. Figure 2 , Figure 3 , Figures 8 to 10As shown, in this embodiment, a first component 14 is further disposed on the second surface 12 of the first device layer 1 , a second component 33 is first disposed on the third surface 31 of the second device layer 3 , and a third component 34 is disposed on the fourth surface 32 .

[0093] In one embodiment, the above step S104, forming an insulating first dam structure 4 at the second pad point on the third surface 31, includes:

[0094] Step S1041 , printing a ring-shaped insulating glue on the outer periphery of the second pad point on the third surface 31 .

[0095] Insulating glue, specifically epoxy encapsulated insulating glue, is used. Through direct writing printing, precise air pressure control drives the printing needle 100 to precisely discharge the material, and the first dam structure 4 is formed around the second pad point on the third surface 31 of the second device layer 3. Similarly, the direct writing printing process of the insulating glue also uses the high-precision electronic 3D printing equipment produced by Core Element, preferably a ceramic printing needle 100 with an inner diameter of 100μm. During printing, the printing needle 100 barrel filled with insulating glue is installed in the printing equipment, the printing speed is set to 3mm / s, and the feed air pressure is 45psi. First, the printing needle 100 is aligned with the edge of the second pad point of the second device layer 3 in turn, and the insulating glue is squeezed out after the feed air pressure is turned on. The insulating glue is used to print the first dam structure 4 in a circular manner around the second pad point. Refer to Figure 8 and Fig. 9 At the end of each first dam structure 4, the print head needs to close the air supply pressure in advance to reduce the glue accumulation at the printing needle 100, so that the head and tail of each first dam structure 4 are as small as possible, but no gaps should appear in the first dam structure 4, otherwise the subsequent conductive glue will overflow from the pad after filling, causing a short circuit.

[0096] Step S1042 , baking and curing the insulating glue to form an insulating first dam structure 4 .

[0097] The first dam structure 4 processed by direct writing printing is cured by baking, so that in the subsequent process, the first dam structure 4 can be reliably adhered to the second pad point on the third surface 31 of the second device layer 3. The insulating glue is different from the alloy solder ball. After baking and curing, it can withstand the reflow process of 260°C, and the glue itself will not remelt.

[0098] Furthermore, the viscosity of the insulating glue mentioned above ranges from 100,000 cps to 1,000,000 cps, and the thixotropic index ranges from 2 to 7; the thixotropic index of the conductive glue in the first dam structure 4 ranges from 2 to 7.

[0099] Specifically, in this embodiment, the insulating glue used in the first dam structure 4 is epoxy insulating glue. Preferably, the viscosity of the epoxy insulating glue is set to 550000cps, and the thixotropic index is set to 3, so that it has good shape retention ability. The thixotropic index of the conductive glue filled in the first dam structure 4 is set to 2-7, and a conventional conductive glue for packaging such as EPO-TEK H20E (epoxy conductive silver glue, 100% solid content silver filled epoxy resin adhesive, also known as silver conductive paste) can be used. Due to the presence of the first dam structure 4, a low-viscosity conductive glue can be used here, and its flow is limited to the first dam structure 4 at the second pad point.

[0100] The temperature range of the above-mentioned baking and curing insulating glue is 100℃~200℃, and the time of baking and curing insulating glue is 0.5h~3h, forming a first dam structure 4 with excellent shape stability and insulation performance. Preferably, the condition of baking insulating glue in this embodiment is specifically baking at a temperature of 150℃ for 30min to complete curing, which has the best effect.

[0101] like Fig.11 As shown, after the first device layer 1 and the second device layer 3 are stacked and solidified, the first device layer 1 and the second device layer 3 are flipped again, with the fourth surface 32 of the second device layer 3 facing upward to facilitate stacking of more devices.

[0102] In one embodiment, the fourth surface 32 of the second device layer 3 has a plurality of third pads; after curing the conductive glue in the first dam structure 4 to form the first conductive glue layer 5 in step S107, the method further includes:

[0103] A second conductive column 6 is formed at the third pad point of the fourth surface 32 .

[0104] like Fig.11 As shown, a second conductive column 6 is provided at the pad point on the other side surface of the second device layer 3 away from the first device layer 1, and the free end of the second conductive column 6, i.e., the second connecting portion 61, is also formed into a pointed shape. It can be understood that the stacked first device layer 1 and the second device layer 3 are used as a new first device layer 1, and the conductive column and other structures are again provided on the new first device layer 1, so as to facilitate the stacking of three or more layers of devices.

[0105] A third device layer 7 is provided. The third device layer 7 includes a fifth surface 71 and a sixth surface 72 which are arranged opposite to each other. The fifth surface 71 has a plurality of fourth pads.

[0106] refer to Fig.12The third device layer 7 can be set to the same structure as the second device layer 3, that is, a 5mm*5mm substrate is used as the third device layer 7, the fifth surface 71 of the third device layer 7 is used as the front side, and the sixth surface 72 is used as the back side. The fifth surface 71, that is, the front side is provided with a plurality of fourth solder pads with a diameter of 500μm and an interval size of 750μm. The fourth solder pads can also be copper solder pads.

[0107] A second dam structure 8 is formed at the fourth pad point of the fifth surface 71 . The second dam structure 8 is a ring-shaped insulating structure having a second accommodating space.

[0108] An annular second dam structure 8 is arranged at each fourth solder pad point on the fifth surface 71 of the third device layer 7. In the present embodiment, the second dam structure 8 has the same specifications as the first dam structure 4. The radial dimension of the second dam structure 8 is set to 150 μm, and the thickness is set to 100 μm. Epoxy insulating glue is used to form an insulating structure. A second accommodating space connected to the fourth solder pad point is formed in the middle of the annular second dam structure 8, so as to form a conductive connection with the third solder pad point later.

[0109] The second accommodating space of the second dam structure 8 is filled with conductive glue.

[0110] The stacked first device layer 1 and second device layer 3 are placed with the fourth surface 32 facing upward, and the fifth surface 71 of the third device layer 7 is also placed upward. Then, the second dam structure 8 of the third device layer 7 is filled with conductive glue to cover the entire second accommodation space of the second dam structure 8. In this embodiment, the conductive glue filled in the second dam structure 8 is the same as the conductive glue filled in the first dam structure 4, that is, the depth of the conductive glue filled in the second dam structure 8 is also set to 80μm, which is slightly lower than the depth of the second dam structure 8 to avoid glue overflow during contact with the second conductive column 6.

[0111] The first device layer 1 and the second device layer 3 are fixed on the third device layer 7 so that the fifth surface 71 is arranged opposite to the fourth surface 32 , and the second conductive pillar 6 contacts the conductive glue in the second dam structure 8 .

[0112] The first device layer 1 and the second device layer 3 are turned over as a whole, and the fourth surface 32 of the second device layer 3 provided with the second conductive pillar 6 is facing downward, and the second conductive pillar 6 is aligned with the second dam structure 8 and gradually moves toward the third device layer 7 until it contacts the conductive glue in the second dam structure 8 and penetrates a proper distance, thereby increasing the contact area with the conductive glue. In this embodiment, a nozzle structure is used to absorb the first surface 11 of the first device layer 1 and pick it up and turn it over, and then the first device layer 1 and the second device layer 3 are driven to gradually move toward the third device layer 7 as a whole. After the second conductive pillar 6 contacts the conductive glue, the nozzle structure continues to press down 30 μm, so that the second conductive pillar 6 is fully in contact with the conductive glue in the second dam structure 8. At this time, since the conductive glue has not yet solidified, it still has a certain degree of adhesion after contacting the second conductive pillar 6, and the second conductive pillar 6 of the second device layer 3 can be temporarily fixed.

[0113] The conductive glue in the second dam structure 8 is cured to form a second conductive glue layer, and the second conductive glue layer is fixedly bonded to the second conductive column 6 .

[0114] The stacked first device layer 1 and the second device layer 3 as a whole and the third device layer 7 are baked and cured, so that the conductive glue in the second dam structure 8 is cured, and the first device layer 1, the second device layer 3 as a whole and the third device layer 7 are firmly stacked. The baking treatment of the conductive glue in the second dam structure 8 is the same as the baking treatment of the conductive glue in the first dam structure 4. The baking curing temperature is generally between 100 and 200°C, and the baking time is 0.5h to 3h. The curing temperature and curing time of different conductive glues are different and are not specifically limited. In this embodiment, the above-mentioned conductive glue uses a conductive glue with a viscosity of 3300cps and a thixotropic index of 3. The curing condition is baking at 180°C for 60min to achieve reliable bonding between the conductive glue and the second conductive column 6. At this time, the third device layer 7 is stacked and merged with the first device layer 1 and the second device layer 3 as a whole. Then, the stacked three-layer device is flipped over, and the first surface 11 is in contact with the placement platform, and the sixth surface 72 is placed upward. After flipping, the entire three-layer device can be used as a new first device layer 1 for subsequent repeated stacking. Fig.13 shown.

[0115] This embodiment also provides a stacked package structure. Fig.10, manufactured by the above-mentioned stacking packaging method, including: a first device layer 1, a first conductive column 2, a second device layer 3, a first dam structure 4 and a first conductive adhesive layer 5, wherein the first device layer 1 includes a first surface 11 and a second surface 12 arranged oppositely, and the second surface 12 has a plurality of first pads 13; the first conductive column 2 is arranged at the first pad 13 of the second surface 12; the second device layer 3 includes a third surface 31 and a fourth surface 32 arranged oppositely, and the third surface 31 has a plurality of second pads; the second device layer 3 is fixedly connected to the first device layer 1, and the third surface 31 is arranged oppositely to the second surface 12; the first dam structure 4 is arranged at the second pad of the third surface 31, and the first dam structure 4 is an annular insulating structure with a first accommodating space; the first conductive adhesive layer 5 is arranged in the first accommodating space, and the first conductive adhesive layer 5 is fixedly bonded to the first conductive column 2.

[0116] In the present embodiment, in the stacked packaging structure prepared by the above-mentioned stacked packaging method, the stacked packaging of the first device layer 1 and the second device layer 3 abandons the traditional solder ball interconnection method, and instead sets a highly conformal first conductive column 2 on the first device layer 1, sets a first dam structure 4 on the second device layer 3, and sets a first conductive adhesive layer 5 in the first dam structure 4. The first dam structure 4 makes the first conductive adhesive layer 5 structurally complete and has a good conductive connection with the first conductive column 2. After the first conductive column 2 and the first conductive adhesive layer 5 in the first dam structure 4 are connected, such a connection avoids the occurrence of reflow in the reflow process during the subsequent device layer stacking process, thereby affecting the stacking and electrical interconnection, thereby ensuring reliable interconnection between the device layers, and ultimately achieving reliable stacking packaging of multiple device layers.

[0117] In one embodiment, the fourth surface 32 of the above-mentioned second device layer 3 has multiple third pads; the stacked packaging structure also includes: a second conductive column 6, a third device layer 7, a second dam structure 8 and a second conductive adhesive layer, wherein the second conductive column 6 is arranged at the third pad of the fourth surface 32, and the free end of the second conductive column 6, that is, the second connection end, is also formed into a pointed shape; the third device layer 7 includes a fifth surface 71 and a sixth surface 72 arranged opposite to each other, and the fifth surface 71 has multiple fourth pads, the third device layer 7 is fixedly connected to the second device layer 3, and the fifth surface 71 is arranged opposite to the fourth surface 32; the second dam structure 8 is arranged at the fourth pad of the fifth surface 71, and the second dam structure 8 is an annular insulating structure with a second accommodating space; the second conductive adhesive layer is arranged in the second accommodating space, and the second conductive adhesive layer is fixedly bonded to the second conductive column 6.

[0118] After the stacked first device layer 1 and the second device layer 3 are flipped, the first surface 11 of the first device layer 1 contacts the placement platform, and the fourth surface 32 is placed upward, and can be used as a new first device layer 1 for subsequent stacking. A third pad point is arranged on the fourth surface 32, and a second conductive column 6 is arranged at the third pad point. A fourth pad point is arranged on the fifth surface 71 of the third device layer 7, and a second dam structure 8 is arranged at the fourth pad point, and a second conductive adhesive layer is formed in the second dam structure 8. The second conductive column 6 on the fourth surface 32 is bonded and fixed to the second conductive adhesive layer in the second dam structure 8 to complete the stacking of the three device layers. Finally, the first surface 11 of the first device layer 1 contacts the placement platform, and the sixth surface 72 of the third device layer 7 is placed upward, as shown in FIG. Fig.13 As shown, it is convenient to carry out subsequent stacking of devices of the fourth layer, the fifth layer or even more layers. The conductive pillars and conductive glue for interconnecting the lower layer devices will not have the problem of remelting and reflow, and the reliability of the multi-layer device stacking is guaranteed.

[0119] refer to Fig.13 As shown, the fifth surface 71 of the third device layer 7 in this embodiment is provided with a fourth component 73 , and the sixth surface 72 is provided with a fifth component 74 .

[0120] The further functional description of each of the above structures is the same as that described in the above corresponding method embodiments and will not be repeated here.

[0121] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0122] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A stacking packaging method, characterized in that: include: Providing a first device layer, the first device layer comprising a first surface and a second surface arranged opposite to each other, the second surface having a plurality of first pads; forming a first conductive column at a first pad point on the second surface; Providing a second device layer, wherein the second device layer comprises a third surface and a fourth surface which are arranged opposite to each other, and a plurality of second pads are provided on the third surface; forming a first dam structure at the second pad point on the third surface, wherein the first dam structure is a ring-shaped insulating structure having a first accommodating space; Filling the first accommodating space of the first dam structure with conductive glue; Fixing the first device layer on the second device layer so that the second surface is arranged opposite to the third surface and the first conductive pillar contacts the conductive glue in the first dam structure; The conductive glue in the first dam structure is cured to form a first conductive glue layer, and the first conductive glue layer is fixedly bonded to the first conductive column.

2. The stacking packaging method according to claim 1, characterized in that: The forming of a first conductive column at a first pad point on the second surface comprises: Printing conductive paste at the first pad point on the second surface in a vertically pulling manner; The conductive paste is baked and cured to form a first conductive column.

3. The stacking packaging method according to claim 2, characterized in that: The conductive paste comprises a binder and metal particles, wherein the size of the metal particles ranges from 30 nm to 30 μm; the viscosity of the conductive paste ranges from 100,000 cps to 800,000 cps, and the thixotropic index ranges from 3 to 7.

4. The stack packaging method according to claim 2, characterized in that: The temperature range of baking and curing the conductive paste is 100° C. to 200° C., and the time of baking and curing the conductive paste is 0.5 h to 3 h.

5. The stacking packaging method according to claim 1, characterized in that: The insulating first dam structure is formed at the second pad point on the third surface, comprising: Printing a ring-shaped insulating glue on the outer periphery of the second pad point on the third surface; The insulating glue is baked and cured to form an insulating first dam structure.

6. The stack packaging method according to claim 5, characterized in that: The viscosity of the insulating glue is in the range of 100,000 cps to 1,000,000 cps, and the thixotropic index is in the range of 2 to 7; the thixotropic index of the conductive glue in the first dam structure is in the range of 2 to 7.

7. The stack packaging method according to claim 5, characterized in that: The temperature range of baking and curing the insulating glue is 100° C. to 200° C., and the time of baking and curing the insulating glue is 0.5 h to 3 h.

8. The stack packaging method according to any one of claims 1 to 7, characterized in that: The fourth surface of the second device layer has a plurality of third pads; After curing the conductive glue in the first dam structure to form a first conductive glue layer, the method further includes: forming a second conductive column at a third pad point on the fourth surface; Providing a third device layer, the third device layer comprising a fifth surface and a sixth surface arranged opposite to each other, the fifth surface having a plurality of fourth pads; forming a second dam structure at the fourth pad point on the fifth surface, wherein the second dam structure is an annular insulating structure having a second accommodating space; Filling the second accommodating space of the second dam structure with conductive glue; Fixing the first device layer and the second device layer on the third device layer so that the fifth surface is arranged opposite to the fourth surface and the second conductive pillar contacts the conductive glue in the second dam structure; The conductive glue in the second dam structure is cured to form a second conductive glue layer, and the second conductive glue layer is fixedly bonded to the second conductive column.

9. A stacked package structure, characterized in that: include: The first device layer comprises a first surface and a second surface which are arranged opposite to each other, wherein the second surface has a plurality of first pads; A first conductive column is disposed at a first pad point on the second surface; The second device layer comprises a third surface and a fourth surface which are arranged opposite to each other, and the third surface has a plurality of second pads; the second device layer is fixedly connected to the first device layer, and the third surface is arranged opposite to the second surface; A first dam structure is arranged at the second pad point of the third surface, wherein the first dam structure is an annular insulating structure having a first accommodating space; The first conductive adhesive layer is disposed in the first accommodating space, and the first conductive adhesive layer is fixedly bonded to the first conductive column.

10. The package stacking structure according to claim 9, wherein: The fourth surface of the second device layer has a plurality of third pads; the stacked package structure further includes: A second conductive column is disposed at a third pad point on the fourth surface; A third device layer comprises a fifth surface and a sixth surface which are arranged opposite to each other, and the fifth surface has a plurality of fourth pads; the third device layer is fixedly connected to the second device layer, and the fifth surface is arranged opposite to the fourth surface; a second dam structure, disposed at the fourth pad point of the fifth surface, wherein the second dam structure is an annular insulating structure having a second accommodating space; The second conductive adhesive layer is disposed in the second accommodating space, and the second conductive adhesive layer is fixedly bonded to the second conductive column.

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