Chip packaging moisture absorption and heat dissipation structure and preparation method thereof

Abstract

The present invention discloses a chip packaging moisture absorption and heat dissipation structure and a preparation method thereof. The moisture absorption and heat dissipation structure comprises a base, a moisture absorption layer, a heat dissipation rib and a cover plate. The base and the cover plate are connected to each other to form a closed box structure. The moisture absorption layer is arranged below the inner wall surface of the cover plate, and the heat dissipation rib is arranged below the moisture absorption layer. The chip is mounted above the base and electrically connected to the base through bonding wires. Thermal conductive silica gel is provided above the chip, and the heat dissipation rib is connected above the thermal conductive silica gel. The present invention absorbs moisture by generating a Marangoni effect through the moisture absorption layer to achieve a moisture absorption function, and utilizes the fin effect of the thermal conductive silica gel and the heat dissipation rib to dissipate heat, thereby improving the efficiency of package heat dissipation. In addition, the present invention adopts a sintering process to prepare a bottom mold of the moisture absorption layer, and uses polystyrene balls to explode to form water absorption holes, so that the generated Marangoni effect is stronger and the moisture absorption effect is better.

Description

Technical Field

[0001] The present invention belongs to the technical field of chip packaging, and in particular relates to a chip packaging moisture absorption and heat dissipation structure and a preparation method thereof. Background Art

[0002] Among the various microelectronic device packages currently available, the vast majority, approximately 97%, are molded plastic. However, the inherent porous structure and hydrophilicity of epoxy-based encapsulants make them highly hygroscopic, allowing moisture to penetrate deep into the device's internal interfaces. Because encapsulants lack the required airtightness, they are susceptible to contaminants (such as Na+) in the production environment and residual ionic impurities (such as Cl-) in the encapsulant. This leads to reliability issues such as failure of encapsulated devices due to moisture absorption during subsequent assembly and operation. Furthermore, when electronic packaging devices are exposed to certain humidity and temperature conditions, they absorb moisture from the surrounding environment, which degrades the interfacial bonding strength of various materials. This moisture absorption causes the encapsulant to expand, generating moisture-thermal stress, which exacerbates interfacial stresses. During subsequent PCB assembly processes, under conditions such as lead-free reflow temperatures (260°C) or thermal cycling testing, the combined effects of moisture and thermal stress often lead to device delamination or cracking failure at the interface. Summary of the Invention

[0003] Based on the above problems, the present invention proposes a chip packaging moisture absorption and heat dissipation structure and a preparation method thereof to solve the problem that the current microelectronic device packaging has poor moisture absorption and heat dissipation, which easily leads to device failure.

[0004] The technical solution adopted by the present invention is a chip packaging moisture-absorbing and heat-dissipating structure, comprising a base, a moisture-absorbing layer, a heat-dissipating rib and a cover plate. The base and the cover plate are connected to form a closed box structure. The moisture-absorbing layer is arranged below the inner wall of the cover plate, and the heat-dissipating rib is arranged below the moisture-absorbing layer. The chip is installed above the base and electrically connected to the base through bonding wires. Thermal conductive silicone is provided above the chip, and the heat-dissipating rib is connected above the thermal conductive silicone.

[0005] Preferably, a plurality of water absorption holes are evenly and radially arranged on the moisture absorption layer at predetermined intervals, and the water absorption holes are in the form of a pitcher plant structure.

[0006] Preferably, the thermally conductive silicone is arched, the bottom end of the thermally conductive silicone is bonded to the chip, and the top end is in contact with the bottom surface of the heat dissipation rib.

[0007] Preferably, a deep etched groove is provided on the bottom surface of the moisture absorbing layer on one side of the water absorbing hole, and the heat dissipating fins are mounted in the deep etched groove by epoxy resin bonding to form heat dissipating ribs, which are arranged corresponding to the gaps of the water absorbing hole.

[0008] Preferably, the cover plate comprises a cover plate base disc, on which a plurality of micro holes are uniformly spaced at predetermined intervals; and a connecting piece is provided downwardly on the inner wall surface of the cover plate base disc close to the edge.

[0009] Preferably, the base includes a base base wafer, the edge of the base base wafer is raised upward and provided with a seal, a sealing gasket is provided on the top of the seal, a chip holder is welded in the middle of the upper part of the base base wafer, the chip is mounted above the chip holder and is electrically connected to the base base wafer through bonding wires, and pins are provided below the base base wafer, the bottom end of the pin extends 0.5 mm out of the base base wafer, serving as a port for connecting the chip to the outside world; the cover plate and the base are connected by parallel welds after being engaged with the seal through a connector.

[0010] Preferably, the four corners of the chip bracket are respectively threadedly connected to copper pillars, and the tops of the copper pillars are threadedly connected to the moisture absorbing layer.

[0011] Preferably, a humidity sensor is provided above the base substrate wafer and located on one side of the chip holder, and the humidity sensor is wirelessly connected to the controller.

[0012] The method for preparing the chip packaging moisture absorption and heat dissipation structure comprises the following steps:

[0013] Cover plate preparation: using ceramic, metal or glass wafers to prepare cover plate base wafers, and making micro holes on the cover plate base wafers;

[0014] Preparation of moisture absorption layer and heat dissipation ribs:

[0015] E1. A ceramic material is mixed with a dispersant, a binder, a plasticizer, a release agent, a defoaming agent, and water to prepare a mixed slurry, and then granulated to obtain a granulated powder. The powder is pressed into a green body, holes are drilled on the surface of the green body, and the green body is placed in a vacuum furnace for sintering to form a ceramic structural plate with semicircular through holes.

[0016] E2. Lay two ceramic structural plates of the same structure relative to each other, and fill the semicircular through-holes of the two ceramic structural plates with polystyrene balls. Sinter them at a high temperature of 1000°C, causing the polystyrene balls to explode and form irregular micropores that connect with the semicircular through-holes to form water absorption holes. The two ceramic structural plates are fixedly connected by eutectic welding to obtain a moisture absorption layer with a pitcher plant-like structure.

[0017] E3. Perform deep etching on one side of the hygroscopic layer, apply photoresist to form a mask layer, and etch away the bottom film layer through a rapid etching process to remove the hygroscopic layer material next to the pitcher plant structure, forming a deep etched trench;

[0018] E4. Install the heat dissipation fins in the deep etched grooves by bonding with epoxy resin to form heat dissipation ribs;

[0019] E5. Mill the rib layer into an arched structure;

[0020] Base preparation: A base wafer is made from ceramics through a sintering process; the chip holder is connected to the base wafer and a heat-dissipating insulating paint is applied to the chip holder; copper posts are installed by drilling holes in the four corners of the chip holder, the humidity sensor is bonded to the base wafer, and a sealing gasket is bonded to the connector; and direct-insert pins are introduced under the base.

[0021] Chip packaging: The chip is mounted on the chip holder and electrically connected to the base wafer through bonding wires. Thermal conductive silicone is placed above the chip and molded into an arch shape, bonded to the chip. The cover plate is fitted into the base, and sealed with parallel welds.

[0022] The ceramic material is mixed with a dispersant, a binder, a plasticizer, a release agent, and a defoamer in a mass ratio of 8:0.6:0.5:0.4:0.3:0.2.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) This greatly solves the problem of the package absorbing water vapor from the outside, improving the efficiency of the package's heat dissipation. During subsequent processing and heating, water vapor can evaporate and be discharged through the water absorption holes on the cover plate, solving the current problem of the combined effect of moisture stress and thermal stress in injection molding packages often leading to device delamination or cracking failure at the interface.

[0025] 2) The hygroscopic layer provided by the present invention is formed by sintering ceramics and connecting two plates to form a pitcher plant-like structure. When performing the hygroscopic function, it absorbs water through the Marangoni effect, achieving a hygroscopic function with a small size and low cost. A deep etching process is used to etch trenches in the hygroscopic layer to connect to the heat dissipation ribs. The fin effect is utilized to dissipate heat through microchannels and the rib structure. Furthermore, an arched thermally conductive silicone rubber is provided between the chip and the heat dissipation ribs, thereby improving the efficiency of the package heat dissipation.

[0026] 3) The base structure provided by the present invention achieves airtight packaging through the contact between the sealing gasket ring on the base and the cover structure during airtight packaging. It is compact and can monitor humidity issues within the chip in real time, making it suitable for use in humid environments. The four copper pillars are removable, making maintenance simple and suitable for use in fragile devices. The thermal grease on the chip enhances heat dissipation while also protecting the chip.

[0027] 4) The present invention uses a sintering process to prepare two ceramic structural plates as the bottom mold of the moisture-absorbing layer. Compared with the existing preparation methods using photolithography, development, etching and other technologies, it not only simplifies the process, reduces costs and shortens the preparation time, but also introduces polystyrene balls into the semicircular through holes of the two ceramic structural plates and utilizes the explosion of the polystyrene balls to form irregular micropores. Uncontrollable micropores are generated under controllable conditions. Together with the water-absorbing holes formed by the semicircular through holes of the two ceramic structural plates, the Marangoni effect produced is stronger and the moisture absorption effect is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the present invention;

[0029] Figure 2 Schematic diagram of the structure of the moisture-absorbing layer of the present invention

[0030] Figure 3 is a cross-sectional view of the moisture-absorbing layer of the present invention;

[0031] Figure 4 This is a schematic diagram of the connection between the moisture absorbing layer and the heat dissipation ribs of the present invention;

[0032] Figure 5 A flow chart for preparing the moisture absorbing layer of the present invention;

[0033] Figure 6 A comparison of the micropore structures formed by etching and those formed by the explosion of polystyrene balls;

[0034] Markings in the figure: 1. Base, 101. Seal, 102. Sealing gasket, 103. Chip holder, 104. Pin, 105. Copper pillar, 106. Humidity sensor, 2. Moisture absorption layer, 201. Water absorption hole, 202. Deep etching groove, 3. Heat dissipation rib, 4. Cover, 401. Connector, 5. Chip, 6. Bonding wire, 7. Thermal conductive silicone. DETAILED DESCRIPTION

[0035] The present invention will be further explained below with reference to the accompanying drawings to facilitate better understanding by those skilled in the art.

[0036] Example 1

[0037] like Figure 1-4As shown, a chip package moisture absorption and heat dissipation structure includes a base 1, a moisture absorption layer 2, a heat dissipation rib 3 and a cover plate 4. The base 1 and the cover plate 4 are connected to each other to form a closed box structure. The moisture absorption layer 2 is arranged below the inner wall of the cover plate 4, and the heat dissipation rib 3 is arranged below the moisture absorption layer 2. The chip 5 is mounted above the base 1 and is electrically connected to the base 1 through bonding wires 6. A thermal conductive silicone 7 is provided above the chip 5, and the heat dissipation rib 3 is connected above the thermal conductive silicone 7. The moisture absorption layer 2 and the heat dissipation rib 3 greatly solve the problem of the package absorbing water vapor from the outside, improve the efficiency of the package heat dissipation, and solve the problem that the combined effect of moisture stress and thermal stress of the current injection molding package often causes the device to delaminate or burst at the interface and fail.

[0038] Specifically, the base 1 includes a base substrate wafer, a chip holder 103, pins 104, a copper column 105 and a humidity sensor 106. The base substrate wafer is made of ceramic through a sintering process. The edge of the base substrate wafer is raised upward and provided with a seal 101. The top of the seal 101 is provided with a sealing gasket ring 102 to achieve airtight packaging and reduce the entry of external moisture. At the same time, in order to prevent stress from propagating into the integrated circuit area, a chip sealing ring is formed around the integrated circuit area; the chip holder 103 is welded to the middle of the upper part of the base substrate wafer by a resistance welding process, and the surface of the chip holder 103 is coated with heat dissipation insulating paint. The chip 5 is installed above the chip holder 103 and is electrically connected to the base substrate wafer through bonding wires 6. The chip holder 103 mainly plays the role of carrying and protecting the chip 5 and connecting the upper chip 5 and the lower circuit board. After packaging, it protects, fixes and supports the chip 5, enhances the thermal conductivity and heat dissipation performance of the chip 5, and can also connect the chip 5 with the printed circuit board to achieve The functions include electrical and physical connection, power distribution, signal distribution, and communication between the internal and external circuits of the chip 5; a pin 104 is provided under the base substrate wafer, and the bottom end of the pin 104 extends out of the base substrate wafer by 0.5 mm, serving as a port for connecting the chip 5 to the outside world, thereby realizing electrical interconnection between the assembled chip 5 and the outside world; four copper pillars 105 are respectively provided at the four corners of the chip bracket 103, and the top and bottom ends of the copper pillars 104 are respectively threadedly connected to the moisture-absorbing layer 2 and the chip bracket 103. The four copper pillars 104 are detachable, and the maintenance method is simple, which is conducive to application in fragile devices; the humidity sensor 106 is provided on one side of the chip bracket 103 and is bonded to the base substrate wafer by epoxy resin. The humidity sensor 106 is wirelessly connected to the controller and can monitor the humidity problem in the chip 5 in real time, which is conducive to application in humid places. When the humidity exceeds the standard, an alarm is issued to inform the user that the component is unreliable and needs to be dehumidified to ensure their normal operation and improve work efficiency and reliability.

[0039] The cover plate 4 includes a cover plate base disc, the material of which can be glass, ceramic, or metal. A number of micro-holes are evenly spaced at predetermined intervals on the cover plate base disc through a laser etching process or a plasma etching process in micro-nano processing technology, which plays a role in convective heat dissipation and water vapor dissipation; a connector 401 is provided on the inner wall surface of the cover plate base disc near the edge, and the cover plate 4 and the base 1 are connected by parallel welds after the connector 401 is engaged with the sealing member 101.

[0040] The hygroscopic layer 2 is provided with a plurality of water absorption holes 201 radially and evenly spaced at predetermined intervals. The water absorption holes 201 are pitcher plant structures. When performing the hygroscopic function, they absorb water through the Marangoni effect to achieve the hygroscopic function, with a small size and low cost. The bottom surface of the hygroscopic layer 2 is provided with a deep etched groove 202 on one side of the water absorption hole 201. The heat dissipation fins are mounted in the deep etched groove 202 by epoxy resin bonding to form heat dissipation ribs 3, which are arranged corresponding to the gaps in the water absorption holes 201, thereby improving the heat dissipation performance.

[0041] The thermally conductive silicone 7 is arched and is a thermally conductive medium material synthesized with silicone as the base material and metal oxide as the auxiliary material. The bottom end of the thermally conductive silicone 7 is bonded to the surface of the chip 5, and the top surface is in contact with the bottom surface of the heat dissipation rib 3. The thermally conductive silicone 7 has high thermal conductivity, excellent thermal conductivity, good electrical insulation, a wide operating temperature, good operating stability, low viscosity and good construction performance, and can efficiently conduct the heat around the chip 5 to the heat dissipation rib 3.

[0042] The present invention utilizes a pitcher plant-like structure, designing a moisture-absorbing layer 2 that mimics the pitcher plant structure. This layer utilizes the Marangoni effect to absorb moisture within the package. During subsequent heating, moisture is evaporated through micropores in the ceramic cover, addressing the issue of component moisture absorption. Furthermore, the present invention connects a microgrid heat dissipation rib structure beneath the pitcher plant-like moisture-absorbing layer 2. This structure utilizes the fin effect to dissipate heat through microchannels and the rib structure. A layer of thermally conductive silicone grease 7 is placed between the heat dissipation ribs 3 and the chip 5, enhancing heat dissipation. This addresses existing issues with injection-molded packages, such as delamination and cracking caused by moisture absorption in some components, as well as issues with wire bonding during injection molding, which can reduce chip quality and even lead to chip failure.

[0043] Example 2

[0044] like Figure 5-6 As shown, a method for preparing a chip packaging moisture absorption and heat dissipation structure includes the following steps:

[0045] Cover plate preparation: A cover plate substrate wafer is prepared using a ceramic, metal or glass wafer, and micro holes are made on the cover plate substrate through a laser etching process or a plasma etching process in micro-nano processing technology;

[0046] Preparation of moisture absorption layer and heat dissipation ribs:

[0047] E1. A ceramic material is mixed with a dispersant, a binder, a plasticizer, a release agent, a defoamer, and water in a mass ratio of 8:0.6:0.5:0.4:0.3:0.2 to form a mixed slurry. Ceramic powder particles are produced by a cold binder method to obtain a granulated powder. The fineness of the ceramic powder particles is 200 mesh. The powder is pressed into a green body, and holes are drilled on the surface of the green body by laser etching. The green body is placed in a vacuum furnace for sintering to form a ceramic structural plate with semicircular through holes.

[0048] E2. Laminating two ceramic structural plates of the same structure relative to each other, and filling the semicircular through-holes of the two ceramic structural plates with polystyrene balls. Sintering at a high temperature of 1000° C. causes the polystyrene balls to explode, forming irregular micropores that communicate with the semicircular through-holes to form water absorption holes 201. The two ceramic structural plates are fixedly connected by a eutectic welding process to obtain a moisture absorption layer 2 with a pitcher plant-like structure pattern.

[0049] E3. Deep etching is performed on one side of the hygroscopic layer 2. A photoresist is applied to form a mask layer. The base film layer is etched away by a rapid etching process to remove the hygroscopic layer 2 material next to the pitcher plant structure, thereby forming a deep etched trench 202.

[0050] E4. Install the heat dissipation fins in the deep etched grooves 202 by bonding with epoxy resin to form heat dissipation ribs 3;

[0051] E6. Mill the rib layer into an arched structure;

[0052] Base preparation: A base substrate wafer is made from ceramic through a sintering process; the chip holder 103 is connected to the base substrate wafer through a resistance welding process, and a heat-dissipating insulating paint is applied to the chip holder 103; copper pillars 105 are installed with threaded holes at the four corners of the chip holder 103, the humidity sensor 106 is bonded to the base substrate wafer using epoxy resin, and the sealing gasket 102 is bonded to the connector 101 using organic polymer glue; and direct-insert pins 104 are introduced under the base substrate to complete its direct connection port to the outside world, realizing electrical interconnection between the assembled chip 5 and the outside world.

[0053] Chip packaging: The chip 5 is mounted on the chip holder 103 and electrically connected to the base wafer through the bonding wire 6. A thermal conductive silicone rubber 7 is placed above the chip 5 and molded into an arch shape and bonded to the chip 5. The cover plate 4 is fitted into the base 1 and sealed with parallel welds.

[0054] The moisture-absorbing layer provided by the present invention is sintered from a ceramic material, pre-drilled before sintering. The resulting ceramic structure is covered with semicircular through-holes. Polystyrene balls are placed within the semicircular through-holes. High temperatures cause the balls to explode, creating irregular micropores that maximize the Marangoni effect and form water-absorbing pores with excellent moisture absorption. This method not only provides excellent efficacy but also simplifies the process and equipment compared to existing technologies, reducing costs and process complexity, making it more practical.

[0055] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a chip packaging moisture absorption and heat dissipation structure, characterized in that: The chip package moisture absorption and heat dissipation structure comprises a base (1), a moisture absorption layer (2), a heat dissipation rib (3) and a cover plate (4); the base (1) and the cover plate (4) are connected to form a sealed box structure; the moisture absorption layer (2) is arranged below the inner wall surface of the cover plate (4); the heat dissipation rib (3) is arranged below the moisture absorption layer (2); the chip (5) is mounted above the base (1) and is electrically connected to the base (1) via a bonding wire (6); a heat conductive silica gel (7) is provided above the chip (5); and the heat conductive silica gel (7) is connected to the heat dissipation rib (3) above. A method for preparing a chip packaging moisture absorption and heat dissipation structure comprises the following steps: Cover plate preparation: using ceramic, metal or glass wafers to prepare cover plate base wafers, and making micro holes on the cover plate base wafers; Preparation of moisture absorption layer and heat dissipation ribs: E1. A ceramic material is mixed with a dispersant, a binder, a plasticizer, a release agent, a defoaming agent, and water to prepare a mixed slurry, and then granulated to obtain a granulated powder. The powder is pressed into a green body, holes are drilled on the surface of the green body, and the green body is placed in a vacuum furnace for sintering to form a ceramic structural plate with semicircular through holes. E2. Lay two ceramic structural plates of the same structure relative to each other, and fill the semicircular through-holes of the two ceramic structural plates with polystyrene balls. Sinter them at a high temperature of 1000°C, causing the polystyrene balls to explode and form irregular micropores that connect with the semicircular through-holes to form water absorption holes. The two ceramic structural plates are fixedly connected by eutectic welding to obtain a moisture absorption layer with a pitcher plant-like structure. E3. Perform deep etching on one side of the hygroscopic layer, apply photoresist to form a mask layer, and etch away the bottom film layer through a rapid etching process to remove the hygroscopic layer material next to the pitcher plant structure, forming a deep etched trench; E4. Install the heat dissipation fins in the deep etched grooves by bonding with epoxy resin to form heat dissipation ribs; E5. Mill the rib layer into an arched structure; Base preparation: A base wafer is made from ceramics through a sintering process; the chip holder is connected to the base wafer and a heat-dissipating insulating paint is applied to the chip holder; copper posts are installed by drilling holes in the four corners of the chip holder, the humidity sensor is bonded to the base wafer, and a sealing gasket is bonded to the connector; and direct-insert pins are introduced under the base. Chip packaging: The chip is mounted on the chip holder and electrically connected to the base wafer through bonding wires. Thermal conductive silicone is placed above the chip and molded into an arch shape, bonded to the chip. The cover plate is fitted into the base, and sealed with parallel welds.

2. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 1, characterized in that: The moisture absorbing layer (2) is provided with a plurality of water absorbing holes (201) radially and evenly spaced at predetermined intervals, and the water absorbing holes (201) are of a pitcher plant structure.

3. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 2, characterized in that: The thermally conductive silica gel (7) is arched, the bottom end of the thermally conductive silica gel (7) is bonded to the chip (5), and the top end surface is in contact with the bottom end surface of the heat dissipation rib (3).

4. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 1, characterized in that: The bottom surface of the moisture absorbing layer (2) is provided with a deep etched groove (202) on one side of the water absorbing hole (201), and the deep etched groove (202) is connected to the heat dissipation rib (3), and the gap between the heat dissipation rib (3) and the water absorbing hole (201) is correspondingly provided.

5. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 1, characterized in that: The cover plate (4) comprises a cover plate base disc, on which a plurality of micro holes are evenly spaced at predetermined intervals; and a connecting piece (401) is provided on the inner wall surface of the cover plate base disc, close to the edge and pointing downward.

6. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 5, characterized in that: The base (1) includes a base substrate disc, the edge of the base substrate disc is upwardly protruding and provided with a sealing member (101), the top of the sealing member (101) is provided with a sealing gasket (102), a chip holder (103) is welded in the middle of the upper part of the base substrate disc, the chip (5) is mounted above the chip holder (103) and is electrically connected to the base substrate disc through a bonding wire (6), a pin (104) is provided below the base substrate disc, the bottom end of the pin (104) extends 0.5 mm from the base substrate disc, and serves as a port for connecting the chip (5) to the outside world; the cover plate (4) and the base (1) are connected by parallel welds after being engaged with the sealing member (101) through a connector (401).

7. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 6, characterized in that: The four corners of the chip bracket (103) are respectively threadedly connected to the copper pillars (105), and the tops of the copper pillars (105) are threadedly connected to the moisture absorbing layer (2).

8. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 6, characterized in that: A humidity sensor (106) is provided above the base substrate wafer and located on one side of the chip bracket (103), and the humidity sensor (106) is wirelessly connected to the controller.

9. The method for preparing a chip packaging moisture absorption and heat dissipation structure according to claim 1, characterized in that: The ceramic material is mixed with a dispersant, a binder, a plasticizer, a release agent, and a defoamer in a mass ratio of 8:0.6:0.5:0.4:0.3:0.2.

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