A method for electromagnetic shielding of a power module and an electromagnetic shielded power module

Abstract

The application discloses a kind of electromagnetic shielding method and electromagnetic shielding power module of power module, method includes the following steps: power module is completed to power chip package and is carried out plasma cleaning;Utilize plastic package material to cover the component and device of the front of the substrate of power module, form plastic package layer;Electromagnetic shielding layer is set on plastic package layer, the electromagnetic shielding layer includes copper layer, first stainless steel layer, nickel layer, carbon structure grid, aluminum layer, second stainless steel layer and silver layer;Finally, plastic package is carried out on the surface of electromagnetic shielding layer.In the application, electromagnetic shielding layer is connected by magnetron sputtering process in physical vapor deposition method and low-temperature active soldering material in multilayer structure, in the case that power module does not use electromagnetic shield, and in the case that no chip surface is mounted magnetic material, the electromagnetic shielding between single power module is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of power chip packaging, specifically relating to an electromagnetic shielding method for a power module and an electromagnetically shielded power module. Background Technology

[0002] Power modules are subject to two types of electromagnetic interference: conducted electromagnetic interference (EMI) and radiated electromagnetic interference (EMI). Conducted EMI refers to interference signals that propagate through conductors in the form of voltage or current to connected circuits. Radiated EMI is interference that propagates as electromagnetic waves; its energy is radiated from the interference source and propagates through space according to the characteristics and laws of electromagnetic waves. Currently, power modules address conducted EMI by optimizing circuit structure design and reducing stray and parasitic inductance to minimize EMI generation. Radiated EMI is addressed by using electromagnetic shielding in large-scale power module applications and mounting magnetic shielding materials on the chip surface. However, electromagnetic shielding only protects power modules within a specific area from external electromagnetic radiation interference and cannot shield between individual power modules. Similarly, mounting magnetic shielding materials on the chip surface can prevent wire bonding, and the difference in thermal expansion coefficients between the magnetic shielding material and the chip surface coating can lead to chip failure during long-term operation, reducing reliability. Summary of the Invention

[0003] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide an electromagnetic shielding method and an electromagnetically shielded power module. By depositing an electromagnetic shielding layer on the front side of the power module's molding compound using physical vapor deposition, the electromagnetic shielding layer consists of a multi-layer structure connected by magnetron sputtering in physical vapor deposition with low-temperature active solder. This solves the problem of achieving electromagnetic radiation shielding between individual modules without using an electromagnetic shielding cover or mounting magnetic shielding materials on the chip surface.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides an electromagnetic shielding method for a power module, comprising the following steps:

[0006] S1. Perform plasma cleaning on the power module after the power chip packaging is completed;

[0007] S2. Use molding compound to cover the components on the front side of the power module substrate to form a molding layer;

[0008] S3. Sputter a copper layer on one front side and four sides of the molding layer to serve as the bottom layer of the electromagnetic shielding layer.

[0009] S4. Sputter a first stainless steel layer with a trapezoidal structure onto the surface of the copper layer;

[0010] S5. Sputter nickel layers are filled on both sides of the first stainless steel layer.

[0011] S6. Low-temperature welding of a carbon structure network based on biomass material onto the surfaces of the first stainless steel layer and the nickel layer;

[0012] S7. Low-temperature welding of a second stainless steel layer is performed on the surface of the carbon structure network. The second stainless steel layer has the same and symmetrical trapezoidal structure as the first stainless steel layer in step S3. This symmetrical structure can absorb electromagnetic interference. The second stainless steel layer is a pre-sputtered layer.

[0013] S8. Sputter aluminum layers are filled on both sides of the second stainless steel layer.

[0014] S9. Sputter a silver layer onto the surface of the second stainless steel layer and the aluminum layer.

[0015] S10. The electromagnetic shielding layer process is now complete. This electromagnetic shielding layer is used to electromagnetically shield the power module.

[0016] S11. Plastic seal the surface of the electromagnetic shielding layer.

[0017] As a preferred technical solution, in step S1, the specific process parameters for plasma cleaning are as follows: first, the power module is cleaned for 180 seconds in a mixed atmosphere of hydrogen and argon, and then the power module is cleaned for 120 seconds in an argon atmosphere.

[0018] As a preferred technical solution, the specific process parameters for the copper layer sputtering process in step S3 are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 1000W, sputtering time of 20min, sputtered copper layer thickness of 15-18 micrometers.

[0019] As a preferred technical solution, the specific process parameters for sputtering the first stainless steel layer in step S4 are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 300W, sputtering time of 80s, and sputtering trapezoidal stainless steel layer thickness of 4-7 micrometers.

[0020] As a preferred technical solution, the specific process parameters for the nickel layer sputtering process in step S5 are as follows: In the magnetron sputtering equipment, the vacuum level is 10... -7 Pa, sputtering power of 350W, sputtering time of 60S, and the thickness of the sputtered nickel layer is consistent with that of the first stainless steel layer, which is 4-7 micrometers.

[0021] As a preferred technical solution, in step S6, the preparation process of the carbon structure network is as follows: in a nitrogen heating furnace, under a high-purity nitrogen atmosphere, commercial cotton pads are pyrolyzed at 750°C for 50 minutes, then cooled to 550°C at a rate of 10°C / min, and finally naturally cooled to room temperature to prepare a biomass carbon structure network.

[0022] As a preferred technical solution, the specific process parameters for the low-temperature welding process of the second stainless steel layer in step S7 are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 300W, sputtering time of 80s, and sputtering thickness of 4-7 micrometers for the second stainless steel layer; after the pre-formed stainless steel layer is sputtered, it is low-temperature welded to the bio-carbon structure network in a vacuum reflow oven at 200℃ using low-temperature active solder.

[0023] As a preferred technical solution, the specific process parameters for the sputtering aluminum layer process in step S8 are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 450W, sputtering time of 70S, and sputtering aluminum layer thickness of 4-7 micrometers consistent with the second stainless steel layer.

[0024] As a preferred technical solution, in step S9, the specific process parameters for the silver layer sputtering process are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 1200W, sputtering time of 12min, and the thickness of the sputtered silver layer of 8-11 micrometers.

[0025] As a preferred technical solution, in step S11, the surface of the electromagnetic shielding layer is encapsulated, and the thickness of the encapsulation layer is one-fifth of that of the previous encapsulation layer.

[0026] Secondly, the present invention also provides an electromagnetic shielding power module, including power chips, multiple power chips are mounted on a substrate, the circuit connection between the power chips is completed by bonding wires, the substrate is mounted on a substrate, and finally the power terminals and power signal terminals are ultrasonically bonded to complete the front-end packaging; the electromagnetic shielding layer is physically vapor-deposited on the surface of the plastic encapsulation layer of the front side and four sides of the substrate using the electromagnetic shielding method of the power module described above.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) Compared with traditional electromagnetic shielding covers, the electromagnetic shielding layer in this invention can achieve electromagnetic interference shielding between individual modules, increasing the reliability and lifespan of the power module. Compared with surface-mounted magnetic shielding materials on chips, the electromagnetic shielding layer in this invention can realize the process operation of bonding leads on the device surface in the module, while also avoiding the risk of damage to power devices caused by surface-mounted magnetic shielding materials.

[0029] (2) From the perspective of feasibility, the electromagnetic shielding layer in this invention only requires physical vapor deposition on the surface of the encapsulation layer after the power module is encapsulated, which does not damage the power module and is safe and reliable. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart illustrating an electromagnetic shielding method for a power module according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the mounting and connection of the power chip on the front side of the heat dissipation substrate in an example of the present invention.

[0033] Figure 3 This is a schematic diagram of the encapsulated state in an example of the present invention.

[0034] Figure 4 This is a schematic diagram of a physical vapor deposition electromagnetic shielding layer on the surface of the molding layer in an example of the present invention.

[0035] Reference numerals: 1. Substrate; 2. Backing plate; 3. Power chip; 4. Bonding wire; 5. Power terminal; 6. Power signal terminal; 7. Molding layer; 8. Copper layer; 9. First stainless steel layer; 10. Nickel layer; 11. Carbon structure mesh; 12. Aluminum layer; 13. Second stainless steel layer; 14. Silver layer; 15. Molding layer Detailed Implementation

[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0037] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0038] Example

[0039] like Figure 1 As shown, an electromagnetic shielding method for a power module according to this embodiment includes the following steps:

[0040] S1. Perform plasma cleaning on the power module after the power chip packaging is completed, and then perform plastic encapsulation process.

[0041] Furthermore, the specific process parameters for plasma cleaning in step S1 are: first, 180 seconds in a mixed atmosphere of hydrogen and argon, then 120 seconds in an argon atmosphere. Plasma cleaning effectively removes impurities from the power module surface, thereby reducing the impact of impurities on the electromagnetic shielding effect.

[0042] Understandably, the power chip needs to be packaged before plasma cleaning, such as... Figure 2 As shown, the specific packaging process is as follows: multiple power chips 3 are mounted on the substrate 2, the circuit connection between the power chips 3 is completed by bonding wires 4, the substrate 2 is mounted on the substrate 1, and finally the power terminals 5 and power signal terminals 6 are ultrasonically bonded to complete the front-end packaging.

[0043] S2, such as Figure 3 As shown, molding compound is applied to the devices on the front side of substrate 1 to form molding layer 7. The molding compound does not include the heat sink at the bottom of substrate 1, so as not to affect the heat dissipation effect of the power module.

[0044] After completing the preliminary preparations, the next step is to perform physical vapor deposition of the electromagnetic shielding layer on the front and four sides of the molding compound of substrate 1. The structure of the electromagnetic shielding layer is as follows: Figure 4 As shown.

[0045] S3. First, a copper layer 8 is sputtered on the surface of the molding layer 7 (including one front and four sides). Copper is easily oxidized, so copper is chosen as the bottom layer of the electromagnetic shielding layer, which can not only achieve a good shielding effect against electromagnetic interference, but also protect the copper layer.

[0046] Furthermore, the specific process parameters for this sputtering process are as follows: in the magnetron sputtering equipment, the vacuum level is 10... -7Pa, sputtering power of 1000W, sputtering time of 20min, sputtered copper layer thickness of 15-18 micrometers.

[0047] S4. A trapezoidal first stainless steel layer 9 is sputtered onto the surface of the copper layer 8 of the electromagnetic shielding layer. The first stainless steel layer 9 can be made of 304 stainless steel, which has good electromagnetic shielding effect. At the same time, the trapezoidal structure can also be used for subsequent shielding material filling, thereby enhancing the electromagnetic shielding effect.

[0048] Furthermore, the specific process parameters for this sputtering process are as follows: in the magnetron sputtering equipment, the vacuum level is 10... -7 Pa, sputtering power of 300W, sputtering time of 80s, and sputtering trapezoidal stainless steel layer thickness of 4-7 micrometers.

[0049] S5. Sputtering nickel layers 10 are applied to both sides of the first stainless steel layer 9 of the electromagnetic shielding layer. The nickel layer has an adsorption effect on the self-magnetism of the stainless steel alloy, and the application has a promoting effect on the electromagnetic shielding of the stainless steel.

[0050] Furthermore, the specific process parameters for this sputtering process are as follows: In the magnetron sputtering equipment, the vacuum level is 10... -7 Pa, sputtering power of 350W, sputtering time of 60S, and the thickness of the sputtered nickel layer is consistent with that of the first stainless steel layer 9, which is 4-7 micrometers.

[0051] S6. A carbon structure network 11 based on biomass material is low-temperature welded onto the surface of the first stainless steel layer 9 and the nickel-filled layer 10 of the electromagnetic shielding layer, which can achieve tunable electromagnetic shielding with ultra-low emissivity.

[0052] Furthermore, the specific process parameters for this process are as follows: In a nitrogen heating furnace, under a high-purity nitrogen atmosphere, commercial cotton pads are pyrolyzed at 750°C for 50 minutes, then cooled to 550°C at a rate of 10°C / min, and finally allowed to cool naturally to room temperature to produce a biomass carbon structure network.

[0053] Furthermore, a low-temperature active solder is used to perform low-temperature soldering to the stainless steel layer 9 and the filler layer surface 10 in a vacuum reflow oven at a temperature of 200°C. The purpose of using a low-temperature active solder is that the maximum junction temperature of the chips in the power module is 175°C, and using a low-temperature active solder can reduce the damage to the power module devices caused by excessively high temperatures.

[0054] S7. Low-temperature welding of the second stainless steel layer 13 of the electromagnetic shielding layer is performed on the surface of the carbon structure network 11. The second stainless steel layer 13 is consistent with and symmetrical to the trapezoidal structure of the first stainless steel layer 9 in the previous process. This symmetrical structure can absorb electromagnetic interference. The second stainless steel layer 13 of the electromagnetic shielding layer is a pre-sputtered layer.

[0055] Furthermore, the specific process parameters for this process are as follows: in the magnetron sputtering equipment, the vacuum level is 10... -7 The sputtering power was 300W, the sputtering time was 80s, and the thickness of the second stainless steel layer was 4-7 micrometers. After the pre-formed stainless steel layer was sputtered, it was cryogenically welded to the bio-carbon structure network in a vacuum reflow oven at 200℃ using a low-temperature active solder.

[0056] S8. Sputter aluminum layers 12 are filled on both sides of the second stainless steel layer 13 of the electromagnetic shielding layer.

[0057] Furthermore, the specific process parameters for this sputtering process are as follows: in the magnetron sputtering equipment, the vacuum level is 10... -7 Pa, sputtering power of 450W, sputtering time of 70S, and sputtering aluminum layer thickness of 4-7 micrometers consistent with the second stainless steel layer 13.

[0058] S9. A silver layer 14 is sputtered on the surface of the second stainless steel layer 13 and the aluminum layer 12 of the electromagnetic shielding layer. The silver layer has a good anti-electromagnetic interference effect.

[0059] Furthermore, the specific process parameters for this process are as follows: in the magnetron sputtering equipment, the vacuum level is 10... -7 Pa, sputtering power of 1200W, sputtering time of 12min, and the thickness of the sputtered silver layer of 8-11 micrometers.

[0060] S10. Thus far, the electromagnetic shielding layer process is completed using the above steps S1-S9, and the electromagnetic shielding layer is used to electromagnetically shield the power module.

[0061] S11. Plastic seal the surface of the electromagnetic shielding layer.

[0062] Furthermore, the thickness of this encapsulation layer is one-fifth that of the previous encapsulation layer.

[0063] In the technical solution of this invention, the multi-layered electromagnetic shielding layer has a better electromagnetic shielding effect, and the intermediate biomass carbon structure network can provide support for the reuse of environmental resources. Compared with electromagnetic shielding covers, this invention achieves electromagnetic shielding between individual power modules; compared with chip surface mounting of magnetic shielding materials, it solves the problem of not being able to perform wire bonding on the surface of magnetic shielding material chips.

[0064] In another embodiment of the invention, such as Figure 3 , Figure 4As shown, an electromagnetic shielding module manufactured using the above-described shielding method is also provided. The electromagnetic shielding module includes power chips 3. Multiple power chips 3 are mounted on a substrate 2, and the circuit connections between the power chips 3 are completed via bonding leads 4. The substrate 2 is mounted on a substrate 1. Finally, power terminals 5 and power signal terminals 6 are ultrasonically bonded to complete the front-end encapsulation. Physical vapor deposition of the electromagnetic shielding layer is performed on the plastic encapsulation layer surface of the front side and four sides of the substrate 1 using the electromagnetic shielding method described above. This electromagnetic shielding method is as follows:

[0065] S1. Perform plasma cleaning on the power module after the power chip packaging is completed;

[0066] S2. Use molding compound to cover the components on the front side of the power module substrate to form molding layer 7;

[0067] S3. Sputter a copper layer 8 on one front side and four sides of the molding layer 7, and use the copper layer 8 as the bottom layer of the electromagnetic shielding layer.

[0068] S4. Sputter a first stainless steel layer 9 with a trapezoidal structure onto the surface of copper layer 8;

[0069] S5. Sputtering nickel layers 10 is performed on both sides of the first stainless steel layer 9.

[0070] S6. Low-temperature welding of a carbon structure network 11 based on biomass material onto the surfaces of the first stainless steel layer 9 and the nickel layer 10;

[0071] S7. Low-temperature welding of a second stainless steel layer 13 is performed on the surface of the carbon structure network 11. The second stainless steel layer 13 is consistent with and symmetrical to the trapezoidal structure of the first stainless steel layer 9 in step S3. This symmetrical structure can absorb electromagnetic interference. The second stainless steel layer 13 is a pre-sputtered layer.

[0072] S8. Sputter aluminum layers 12 are filled on both sides of the second stainless steel layer 13.

[0073] S9. Sputter a silver layer 14 onto the surface of the second stainless steel layer 13 and the aluminum layer 12.

[0074] S10. The electromagnetic shielding layer process is now complete. This electromagnetic shielding layer is used to electromagnetically shield the power module.

[0075] S11. Plastic seal the surface of the electromagnetic shielding layer.

[0076] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. The specification and claims do not distinguish components based on differences in name, but rather on differences in function. For example, the term "comprising" used throughout the specification and claims is an open-ended term and should be interpreted as "including but not limited to"; "generally" means that those skilled in the art can solve the technical problem within a certain margin of error and basically achieve the technical effect.

[0077] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electromagnetic shielding method for a power module, characterized in that, Includes the following steps: S1. Perform plasma cleaning on the power module after the power chip packaging is completed; S2. Use molding compound to cover the components on the front side of the power module substrate to form a molding layer (7). S3. Sputter a copper layer (8) on one front and four sides of the molding compound (7) to serve as the bottom layer of the electromagnetic shielding layer; S4. Sputter a first stainless steel layer (9) with a trapezoidal structure on the surface of the copper layer (8). S5. Sputtering nickel layers (10) is performed on both sides of the first stainless steel layer (9); S6. A carbon structure network (11) based on biomass material is low-temperature welded to the surface of the first stainless steel layer (9) and the nickel layer (10). S7. Low-temperature welding of a second stainless steel layer (13) is performed on the surface of the carbon structure network (11). The second stainless steel layer (13) has the same trapezoidal structure as the first stainless steel layer (9) in step S3 and is symmetrical. This symmetrical structure can absorb electromagnetic interference. The second stainless steel layer (13) is a pre-sputtered layer. S8. Sputter aluminum layers (12) are filled on both sides of the second stainless steel layer (13); S9. Sputter a silver layer (14) onto the surface of the second stainless steel layer (13) and the aluminum layer (12). S10. The electromagnetic shielding layer process is now complete. This electromagnetic shielding layer is used to electromagnetically shield the power module. S11. Plastic seal the surface of the electromagnetic shielding layer.

2. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S1, the specific process parameters for plasma cleaning are as follows: first, the power module is cleaned for 180 seconds in a mixed atmosphere of hydrogen and argon, and then the power module is cleaned for 120 seconds in an argon atmosphere.

3. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S3, the specific process parameters for the sputtering copper layer are as follows: in the magnetron sputtering equipment, the vacuum level is 10. -7 Pa, sputtering power of 1000W, sputtering time of 20min, and sputtered copper layer (8) thickness of 15-18 micrometers.

4. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S4, the specific process parameters for sputtering the first stainless steel layer (9) are as follows: in the magnetron sputtering equipment, the vacuum degree is 10. -7 Pa, sputtering power of 300W, sputtering time of 80s, and sputtering trapezoidal stainless steel layer thickness of 4-7 micrometers.

5. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S5, the specific process parameters for sputtering the nickel layer (10) are as follows: In the magnetron sputtering equipment, the vacuum level is 10. -7 Pa, sputtering power of 350W, sputtering time of 60S, and the thickness of the sputtered nickel layer is consistent with that of the first stainless steel layer (9) at 4-7 micrometers.

6. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S6, the preparation process of the carbon structure network is as follows: in a nitrogen heating furnace, under a high-purity nitrogen atmosphere, commercial cotton pads are pyrolyzed at 750°C for 50 minutes, then cooled to 550°C at a rate of 10°C / min, and finally naturally cooled to room temperature to prepare a biomass carbon structure network.

7. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S7, the specific process parameters for the low-temperature welding of the second stainless steel layer (13) are as follows: in the magnetron sputtering equipment, the vacuum degree is 10 -7 Pa, sputtering power of 300W, sputtering time of 80s, sputtering thickness of the second stainless steel layer (13) of 4-7 micrometers; after the pre-fabricated stainless steel layer is sputtered, it is low temperature welded to the bio-carbon structure network in a vacuum reflow oven at 200℃ using low temperature active solder.

8. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S8, the specific process parameters for sputtering the aluminum layer are as follows: in the magnetron sputtering equipment, the vacuum level is 10. -7 Pa, sputtering power of 450W, sputtering time of 70S, sputtered aluminum layer thickness of 4-7 micrometers consistent with the second stainless steel layer (13).

9. The electromagnetic shielding method for a power module according to claim 1, characterized in that, In step S9, the specific process parameters for the silver sputtering process are as follows: in the magnetron sputtering equipment, the vacuum level is 10. -7 Pa, sputtering power of 1200W, sputtering time of 12min, and thickness of sputtered silver layer of 8-11 micrometers; In step S11, the electromagnetic shielding layer is encapsulated on its surface, with the encapsulation thickness being one-fifth of that of the previous encapsulation layer.

10. An electromagnetically shielded power module, characterized in that, The process includes power chips (3), multiple power chips (3) are mounted on a substrate (2), and the circuit connection between the power chips (3) is completed by bonding wires (4). The substrate (2) is mounted on a substrate (1), and finally the power terminals (5) and power signal terminals (6) are ultrasonically bonded to complete the front-end packaging. The electromagnetic shielding layer is physically vapor-deposited on the front side and four sides of the substrate (1) using the electromagnetic shielding method of any one of claims 1-9.

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