Chip stack package structure

Abstract

The application discloses a chip step-stacking packaging structure, which comprises a packaging substrate, a chip stacking body, a plurality of moisture-discharging functional areas, a steam discharging channel and a packaging material layer. The chip stacking body is arranged on the packaging substrate, and comprises a plurality of chips which are sequentially arranged in a thickness direction. The plurality of chips are horizontally staggered layer by layer in a preset direction to form a plurality of step gaps. The moisture-discharging functional areas are arranged in the corresponding step gaps respectively and are in communication with the corresponding chip bonding layer interfaces respectively. The steam discharging channel is arranged in the packaging structure, and is in communication with the plurality of moisture-discharging functional areas respectively and extends to the outside of the packaging structure. A continuous steam releasing path is formed by the plurality of moisture-discharging functional areas and the steam discharging channel, so that the water vapor gathered at the chip bonding layer interfaces can be discharged in time when the packaging structure undergoes a high-temperature process, the steam pressure in the packaging is reduced, and the popcorn effect is inhibited.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip packaging technology, and more specifically to a chip ladder stacking packaging structure. Background Technology

[0002] As electronic products evolve towards higher capacity, higher integration, and miniaturization, multi-chip stacked packaging is widely used in memory devices such as eMMC, UFS, and NAND Flash to increase storage capacity per unit area. Current stacked packaging typically involves stacking multiple chips sequentially, connecting them via a chip bonding layer, and then encapsulating them using molding compound.

[0003] However, during packaging manufacturing, transportation, and storage, materials such as molding compounds and chip bonding layers easily absorb moisture from the environment. When packaged devices undergo high-temperature processes such as reflow soldering, the internal moisture rapidly vaporizes, forming high-pressure water vapor. In traditional stacked packaging, the internal water vapor is difficult to expel in time, easily accumulating at the chip bonding layer interface and generating significant internal pressure. This can lead to problems such as chip-bonding layer delamination, molding compound cracking, and bonding failure, a phenomenon known as the "popcorn effect." Summary of the Invention

[0004] The purpose of this invention is to provide a chip ladder stacking packaging structure to solve the above-mentioned problems existing in the prior art.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: A chip ladder stacked packaging structure includes: Packaging substrate; A chip stack is disposed on the packaging substrate. The chip stack includes a plurality of chips stacked sequentially along the thickness direction. Adjacent chips are connected by a chip adhesive layer. The plurality of chips are horizontally staggered layer by layer along a preset direction to form a plurality of stepped gaps. Multiple dehumidification functional areas are respectively set in the corresponding stepped gaps and are respectively connected to the interface of the corresponding chip bonding layer; A steam discharge channel is disposed inside the encapsulation structure. The steam discharge channel is connected to multiple dehumidification functional areas. The steam discharge channel includes branch guide channels connected to each of the dehumidification functional areas, and a main guide channel connected to the multiple branch guide channels. The main guide channel is connected to the outside of the encapsulation structure. An encapsulation material layer covers the outer side of the chip stack; The multiple dehumidification functional areas and the steam conduction channels together form a steam release path located inside the encapsulation material layer.

[0006] Preferably, the dehumidification functional area includes a dehumidification cavity formed in the corresponding stepped gap, and the dehumidification cavity is connected to the corresponding edge area of ​​the chip bonding layer.

[0007] Preferably, the steam discharge channel further includes at least one through discharge hole disposed in the packaging substrate, one end of the through discharge hole being connected to the main flow channel, and the other end being connected to the packaging substrate and the external environment.

[0008] Preferably, a breathable liquid-blocking membrane is provided at the through-hole, the breathable liquid-blocking membrane being configured to allow gaseous water vapor to pass through while preventing liquid water and external contaminants from entering the steam discharge channel.

[0009] Preferably, at least one of the dehumidification functional areas is filled with a thermally conductive elastic porous composite layer, the thermally conductive elastic porous composite layer comprising an elastic polymer matrix and thermally conductive fillers dispersed within the elastic polymer matrix.

[0010] Preferably, the elastic polymer matrix has an elastic modulus lower than that of the chip and the encapsulation material layer, and the thermally conductive elastic porous composite layer is configured to absorb thermal stress caused by the difference in thermal expansion coefficients between adjacent chips.

[0011] Preferably, the thermally conductive filler includes at least one of aluminum nitride, boron nitride, aluminum oxide, graphene, and carbon nanotubes.

[0012] Preferably, the steam discharge channel is configured as a labyrinthine flow channel containing multiple bends.

[0013] Preferably, the chip bonding layer includes an epoxy resin bonding layer, a polyimide bonding layer, or a hygroscopic resin bonding layer.

[0014] Compared with the prior art, the present invention has the following beneficial effects: by horizontally staggering multiple chips layer by layer along a preset direction, a stepped gap is formed between adjacent chips, and the stepped gap is used to construct a dehumidification functional area connected to the chip bonding layer interface. At the same time, multiple dehumidification functional areas and steam guide channels form a continuous steam release path, thereby enabling the timely removal of water vapor accumulated at the chip bonding layer interface when the packaging structure undergoes high-temperature processes, reducing the steam pressure inside the packaging and suppressing the popcorn effect. Meanwhile, the stepped gap formed by chip staggering is directly used as part of the dehumidification path, realizing the functional utilization of the stepped gap. The integrated design of the steam guide structure is completed without increasing the number of packaging layers, which is beneficial to improving the reliability and space utilization of the packaging structure. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a chip ladder stacked packaging structure according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of a chip ladder stacked packaging structure according to another preferred embodiment of the present invention.

[0016] Explanation of reference numerals in the attached drawings: 100, packaging substrate; 210, chip; 220, chip bonding layer; 300, dehumidification functional area; 410, branch channel; 420, main channel; 430, through-hole; 440, gas-permeable and liquid-resistant membrane; 450, packaging material layer. Detailed Implementation

[0017] The present invention will be further illustrated below by way of examples.

[0018] like Figure 1 As shown, this embodiment provides a chip stepped stacked packaging structure, including a packaging substrate 100, a chip stack, multiple dehumidification functional areas 300, vapor discharge channels, and a packaging material layer 450. The chip stack is disposed on the packaging substrate 100 and includes multiple chips 210 stacked sequentially along the thickness direction. Adjacent chips 210 are connected by chip adhesive layers 220. The multiple chips 210 are horizontally staggered layer by layer along a predetermined direction to form multiple stepped gaps. Multiple dehumidification functional areas 300 are respectively disposed within corresponding stepped gaps and communicate with the interfaces of corresponding chip adhesive layers 220. Vapor discharge channels are disposed inside the packaging structure, communicating with the multiple dehumidification functional areas 300 and extending to the outside of the packaging structure. The packaging material layer 450 covers the outside of the chip stack. The multiple dehumidification functional areas 300 and the vapor discharge channels together form a vapor release path located inside the packaging material layer 450.

[0019] This application arranges multiple chips 210 horizontally staggered layer by layer along a preset direction, forming a stepped gap between adjacent chips 210. This stepped gap is used to construct a dehumidification functional area 300 connected to the chip bonding layer 220 interface. Simultaneously, the multiple dehumidification functional areas 300, together with the steam guide channel, form a continuous steam release path. This allows for the timely removal of water vapor accumulated at the chip bonding layer 220 interface during high-temperature processes, reducing internal steam pressure and suppressing the popcorn effect. Furthermore, by directly utilizing the stepped gaps formed by the chip stagger as part of the dehumidification path, the functional utilization of the stepped gaps is achieved. This integrated design of the steam guide structure is completed without increasing the number of packaging layers, which is beneficial for improving the reliability and space utilization of the packaging structure. The preset direction is a selected direction parallel to the upper surface of the packaging substrate 100.

[0020] In some embodiments, the dehumidification functional region 300 includes a dehumidification cavity formed within the corresponding stepped gap, the dehumidification cavity being connected to the edge region of the corresponding chip bonding layer 220. This allows the dehumidification cavity to serve as a buffer and collection space for water vapor between chip layers, guiding water vapor generated at the interface of the chip bonding layer 220 into the vapor discharge channel, reducing the residence time of water vapor between chip layers and the accumulation of local pressure, thereby further improving the dehumidification capability and anti-popcorn effect capability of the packaging structure.

[0021] In some embodiments, the steam exhaust channel includes branch guide channels 410 communicating with each dehumidification functional area 300, and a main guide channel 420 communicating with the branch guide channels 410. Specifically, the branch guide channels 410 of the steam exhaust channel are disposed within the encapsulation material layer 450 and extend vertically downward. The main guide channel 420 is located within the encapsulation substrate 100 and extends horizontally.

[0022] By setting branch guide channels 410 that are connected to multiple dehumidification functional areas 300 and a total guide channel 420 that merges with multiple branch guide channels 410, water vapor generated between chip layers can be collected and transported in stages along a preset path, avoiding water vapor retention or local pressure concentration between different chip layers, thereby improving the continuity and effectiveness of the steam release path inside the package, and further reducing the risk of popcorn effect caused by steam pressure accumulation during high-temperature processes.

[0023] In some embodiments, the vapor channel further includes at least one through-hole 430 disposed in the encapsulation substrate 100, one end of the through-hole 430 being connected to the main flow channel 420, and the other end being connected to the encapsulation substrate 100 and the external environment.

[0024] Specifically, the through-hole 430 is located on the side end face of the packaging substrate 100 and is discharged from the side end face of the packaging substrate 100 to the external environment, so as to avoid the bottom solder ball dense area.

[0025] In some embodiments, a processing method for the dehumidification cavity and steam discharge channel is also provided, which can be formed by pre-processing the packaging substrate 100 using sacrificial layer technology. First, a main flow channel 420 and a through-flow channel 430 are pre-formed inside the packaging substrate 100 by etching or mechanical processing, and sacrificial material is filled in the main flow channel 420 and the through-flow channel 430 to prevent subsequent molding compound material from intruding. The chip stack is mounted on the packaging substrate 100, and multiple chips 210 are horizontally staggered layer by layer along a preset direction to form multiple stepped gaps. Sacrificial material is then filled in each stepped gap, so that the sacrificial material occupies the entire space of the dehumidification cavity to be formed and is in direct contact with the edge area of ​​the chip bonding layer 220. At the same time, sacrificial material strips are formed at the positions of the branch flow channels 410 to be formed in the packaging material layer 450. The sacrificial material strips extend vertically, with their upper ends connected to the sacrificial materials in each stepped gap and their lower ends connected to the sacrificial materials in the main flow channel 420. Next, encapsulation is performed, so that the encapsulation material layer 450 covers the outside of the chip stack and the sacrificial material strip and cures. Finally, the encapsulation is heated to cause the sacrificial material to thermally decompose and vaporize, and the generated gas is discharged to the external environment through the through-hole 430. After the sacrificial material is removed, a dehumidification cavity communicating with the edge of the chip bonding layer 220 is formed in situ in the stepped gap, and a branch channel channel 410 connecting each dehumidification cavity and the main channel channel 420 is formed in the encapsulation material layer 450, thereby obtaining a vapor release path not filled by the encapsulation material, which is composed of the dehumidification cavity, the branch channel channel 410, the main channel channel 420 and the through-hole 430. The sacrificial material can be a thermally decomposable polymer, such as polycarbonate or polyoxymethylene with a decomposition temperature of 200℃~300℃, and is precisely filled by dispensing or printing.

[0026] In some embodiments, a permeable liquid-resistant membrane 440 is provided at the through-hole 430. The permeable liquid-resistant membrane 440 is configured to allow gaseous water vapor to pass through while preventing liquid water and external contaminants from entering the steam exhaust channel. This embodiment, by providing a permeable liquid-resistant membrane 440 at the through-hole 430, enables the steam exhaust channel to have environmental protection functions. During high-temperature processes such as reflow soldering, water vapor generated inside the package can escape smoothly, while in non-humidification states, it can effectively block external liquid water and contaminant particles from entering the package, avoiding the environmental reliability degradation caused by traditional open exhaust structures, thus balancing the moisture exhaust performance and protective performance of the package structure.

[0027] Among them, the gas-permeable and liquid-blocking membrane 440 is made of polytetrafluoroethylene microporous membrane. The ePTFE membrane has a large number of interconnected micropores with a pore size of about 0.05 to 1 μm. Water vapor molecules can pass through, but liquid water cannot pass through due to surface tension. Furthermore, the long-term working temperature can reach over 200℃.

[0028] In some embodiments, at least one dehumidification functional area 300 is filled with a thermally conductive elastic porous composite layer, which includes an elastic polymer matrix and thermally conductive fillers dispersed within the elastic polymer matrix. By filling at least one dehumidification functional area 300 with a thermally conductive elastic porous composite layer, the composite layer simultaneously possesses thermal conductivity, air permeability, and stress buffering functions. The elastic polymer matrix can absorb the thermomechanical stress generated between the chip 210 and the packaging material due to the difference in thermal expansion coefficients, reducing stress concentration at the chip interface; the thermally conductive fillers can improve the heat transfer capability between the chip 210 and the packaging substrate 100, improving the heat dissipation performance inside the stacked chip. Simultaneously, the thermally conductive elastic porous composite layer has a porous structure, allowing gas to communicate with the vapor discharge channels through the thermally conductive elastic porous composite layer, providing a continuous transport path for water vapor. This enables the thermally conductive elastic porous composite layer to possess heat conduction, stress buffering, and auxiliary dehumidification functions, improving the reliability of the stacked packaging structure under high-temperature cycling environments.

[0029] The elastic polymer matrix includes silicone rubber, polyurethane, or epoxy-modified elastic resin.

[0030] In some embodiments, the elastic polymer matrix has an elastic modulus lower than that of the chip 210 and the encapsulation material layer 450, and the thermally conductive elastic porous composite layer is configured to absorb thermal stress caused by the difference in thermal expansion coefficients between adjacent chips 210.

[0031] By using an elastic polymer matrix with low elastic modulus, the thermally conductive elastic porous composite layer can generate elastic deformation during temperature cycling, thereby alleviating the thermomechanical stress caused by the mismatch of the thermal expansion coefficients of adjacent chips 210, reducing stress concentration at the interface of the chip bonding layer 220, and reducing the risk of warping and interface delamination of the packaging structure.

[0032] In some embodiments, the thermally conductive filler includes at least one of aluminum nitride particles, boron nitride particles, alumina particles, graphene, and carbon nanotubes. By providing a thermally conductive filler composed of aluminum nitride, boron nitride, alumina, graphene, or carbon nanotubes within the elastic polymer matrix, the thermal conductivity of the thermally conductive elastic porous composite layer is improved. This allows the heat generated by the chip 210 to be transferred to the packaging substrate 100 via the dehumidification functional region 300, reducing heat accumulation inside the chip stack structure, improving the heat dissipation performance of the packaging structure, and maintaining the elastic buffering capacity of the composite layer.

[0033] In some embodiments, the chip adhesive layer 220 includes an epoxy resin adhesive layer, a polyimide adhesive layer, or a resin-based chip adhesive layer.

[0034] In some embodiments, such as Figure 2As shown, the steam discharge channel is constructed as a labyrinthine flow channel with multiple bends. Specifically, the branch guide channels 410 of the steam discharge channel are disposed within the encapsulation material layer 450, and the main guide channel 420 is located within the encapsulation substrate 100, with the main guide channel 420 configured as a labyrinthine flow channel. The labyrinthine flow channel significantly increases the flow path and flow resistance of water vapor entering the encapsulation structure in the reverse direction. This causes external water vapor to continuously change direction and decrease in velocity as it flows through the long-distance, multi-bend channel. At the same time, it provides sufficient time and space for water vapor to condense and settle on the channel wall. The condensed droplets are trapped in the low-velocity area of ​​the bends and cannot continue to move forward. Thus, without affecting the forward discharge of internal water vapor, it effectively suppresses the reverse diffusion and intrusion of external environmental water vapor, achieving the "one-way valve" effect of the steam discharge channel.

[0035] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A chip ladder stacked packaging structure, characterized in that, include: Packaging substrate; A chip stack is disposed on the packaging substrate. The chip stack includes a plurality of chips stacked sequentially along the thickness direction. Adjacent chips are connected by a chip adhesive layer. The plurality of chips are horizontally staggered layer by layer along a preset direction to form a plurality of stepped gaps. Multiple dehumidification functional areas are respectively set in the corresponding stepped gaps and are respectively connected to the interface of the corresponding chip bonding layer; A steam discharge channel is disposed inside the encapsulation structure. The steam discharge channel is connected to multiple dehumidification functional areas. The steam discharge channel includes branch guide channels connected to each of the dehumidification functional areas, and a main guide channel connected to the multiple branch guide channels. The main guide channel is connected to the outside of the encapsulation structure. An encapsulation material layer covers the outer side of the chip stack; The multiple dehumidification functional areas and the steam conduction channels together form a steam release path located inside the encapsulation material layer.

2. The chip ladder stacked packaging structure according to claim 1, characterized in that, The dehumidification functional area includes a dehumidification cavity formed in the corresponding stepped gap, and the dehumidification cavity is connected to the edge area of ​​the corresponding chip bonding layer.

3. The chip ladder stacked packaging structure according to claim 1, characterized in that, The steam discharge channel also includes at least one through discharge hole disposed in the packaging substrate. One end of the through discharge hole is connected to the main flow channel, and the other end passes through the packaging substrate and is connected to the external environment.

4. The chip ladder stacked packaging structure according to claim 3, characterized in that, A breathable liquid-blocking membrane is provided at the through-hole. The breathable liquid-blocking membrane is configured to allow gaseous water vapor to pass through and prevent liquid water and external pollutants from entering the steam discharge channel.

5. The chip ladder stacked packaging structure according to claim 1, characterized in that, At least one of the dehumidification functional areas is filled with a thermally conductive elastic porous composite layer, the thermally conductive elastic porous composite layer comprising an elastic polymer matrix and thermally conductive fillers dispersed within the elastic polymer matrix.

6. The chip ladder stacked packaging structure according to claim 5, characterized in that, The elastic polymer matrix has an elastic modulus lower than that of the chip and the encapsulation material layer, and the thermally conductive elastic porous composite layer is configured to absorb thermal stress caused by the difference in thermal expansion coefficients between adjacent chips.

7. The chip ladder stacked packaging structure according to claim 5, characterized in that, The thermally conductive filler includes at least one of aluminum nitride, boron nitride, aluminum oxide, graphene, and carbon nanotubes.

8. The chip ladder stacked packaging structure according to claim 1, characterized in that, The steam discharge channel is constructed as a labyrinthine flow channel containing multiple bends.

9. The chip ladder stacked packaging structure according to claim 1, characterized in that, The chip bonding layer includes an epoxy resin bonding layer, a polyimide bonding layer, or a hygroscopic resin bonding layer.

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