Parylene composite coating encapsulation method for implantable micro-mems sensors

Abstract

The application provides a poly-p-xylylene composite coating packaging method for an implantable micro MEMS sensor, relates to the technical field of sensor packaging, and aims to solve the technical problems of the existing MEMS sensor packaging method, such as the oversized packaging structure, and the decline of sensitivity, comprehensive accuracy and thermal stability after packaging. The method comprises the following steps: obtaining a MEMS sensor sample and performing cleaning treatment on the MEMS sensor sample; connecting a wire to the pad of the MEMS sensor sample after the cleaning treatment to form a conductive path, so that the electrical signal can be transmitted from the inside of the MEMS sensor sample to the outside; sealing the non-coating area of the MEMS sensor sample; and placing the sealed MEMS sensor sample into a packaging system, adding poly-p-xylylene raw materials for packaging, and obtaining a poly-p-xylylene coating, wherein the packaging system is configured as a vacuum environment.

Description

Technical Field

[0001] This invention relates to the field of sensor packaging technology, and more specifically, to a method for encapsulating a parylene composite coating for implantable micro MEMS sensors. Background Technology

[0002] For the packaging of implantable MEMS (Micro-Electro-Mechanical System) devices, there are five main requirements: ultra-thinness, resistance to body fluid corrosion, high reliability, high biocompatibility, and minimal impact on sensor performance. Different application scenarios may require different packaging strategies to ensure optimal sensor performance under a range of physiological conditions. Among these, parylene coatings are widely used in MEMS due to their low permeability and the highest biocompatibility certification at the micrometer level. However, their poor adhesion and low thermal stability limit their application. Simple parylene coatings exhibit strong frictional shear stress with the sensor surface, resulting in poor adhesion and thus unreliable packaging. Regarding enhancing coating adhesion, there are currently two effective methods: one method involves adding an A-174 coupling agent as an adhesive layer between the MEMS surface and the parylene layer, effectively improving adhesion by forming covalent bonds. The other method involves using parylene copolymer films; due to the higher surface energy and the presence of Si-F bonds in CF copolymer films, they exhibit greater bonding strength compared to C and F films.

[0003] However, all of the above packaging methods suffer from technical problems such as excessively large packaging structures and decreased sensitivity, overall accuracy, and thermal stability after packaging. Summary of the Invention

[0004] In view of this, the present invention provides a parylene composite coating encapsulation method for implantable micro MEMS sensors, which solves the technical problems of excessively large encapsulation structures and decreased sensitivity, overall accuracy and thermal stability after encapsulation in existing MEMS sensor encapsulation methods.

[0005] One aspect of the present invention provides a method for encapsulating a parylene composite coating for an implantable micro MEMS sensor, comprising: acquiring a MEMS sensor sample and cleaning the MEMS sensor sample; connecting wires to the pads of the cleaned MEMS sensor sample to form a conductive path, enabling electrical signals to be transmitted from the interior to the exterior of the MEMS sensor sample; sealing the non-coated areas of the MEMS sensor sample; placing the sealed MEMS sensor sample into an encapsulation system, adding parylene raw material for encapsulation, and obtaining a parylene coating, wherein the encapsulation system is configured as a vacuum environment.

[0006] According to an embodiment of the present invention, placing a sealed MEMS sensor sample into a packaging system and adding parylene raw material for packaging to obtain a parylene coating includes: placing a sealed MEMS sensor sample into a packaging system and adding parylene C powder for packaging to obtain a parylene C coating; wherein, the parylene C powder is gradually heated at 60°C to 100°C to obtain the parylene C coating, and during the gradual heating process, the temperature rises by 2°C every 20 minutes.

[0007] According to an embodiment of the present invention, the process of placing a sealed MEMS sensor sample into a packaging system and adding parylene raw material for packaging to obtain a parylene coating includes: placing a sealed MEMS sensor sample into a packaging system and adding parylene F powder for packaging to obtain a parylene F coating; wherein the parylene F powder is gradually heated at a temperature of 40°C to 80°C to obtain the parylene F coating, and during the gradual heating process, the temperature increases by 2°C every 30 minutes.

[0008] According to an embodiment of the present invention, the process of placing a sealed MEMS sensor sample into a packaging system and adding parylene raw material for packaging to obtain a parylene coating includes: placing a sealed MEMS sensor sample into a packaging system and adding parylene C powder and parylene F powder mixed in a preset ratio for packaging to obtain a parylene CF copolymer film coating; wherein, the mixture of parylene C powder and parylene F powder is gradually heated at 60°C to 100°C to obtain the parylene CF copolymer film coating, and the temperature rises by 2°C every 20 minutes during the gradual heating process.

[0009] According to an embodiment of the present invention, a sealed MEMS sensor sample is placed into a packaging system, and parylene raw material is added for packaging to obtain a parylene coating. The method further includes: placing the sealed MEMS sensor sample into the packaging system and adding a coupling agent for packaging, wherein the coupling agent is used to improve the adhesion of the parylene coating.

[0010] According to an embodiment of the present invention, the thickness of the coupling agent is 500nm-1000nm.

[0011] According to an embodiment of the present invention, the thickness of the parylene coating is 0.5 μm-10 μm.

[0012] According to an embodiment of the present invention, cleaning a MEMS sensor sample includes cleaning the surface of the MEMS sensor sample using a lint-free cloth and alcohol.

[0013] According to an embodiment of the present invention, the conductor includes aluminum wire and gold wire.

[0014] According to an embodiment of the present invention, the pressure value of the vacuum environment is less than 0.026 torr.

[0015] Compared with the prior art, the parylene composite coating encapsulation method for implantable micro MEMS sensors provided by the present invention has at least the following beneficial effects:

[0016] (1) The parylene composite coating encapsulation method for implantable micro MEMS sensors provided by the present invention uses smaller and more precise parylene raw materials (such as C powder, F powder and mixture of C powder and F powder) for encapsulation, realizing an ultra-thin encapsulation structure and meeting the volume requirements of implantable micro MEMS sensors.

[0017] (2) The parylene composite coating encapsulation method for implantable micro MEMS sensors provided by the present invention effectively enhances the adhesion of the parylene coating by introducing a coupling agent, thus solving the technical problem of low thermal stability of the parylene coating.

[0018] (3) The parylene composite coating encapsulation method for implantable micro MEMS sensors provided by the present invention can optimize the coating characteristics for different application requirements by adjusting the mixing ratio of parylene C powder and parylene F powder. Attached Figure Description

[0019] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0020] Figure 1 A flowchart illustrating a method for encapsulating a parylene composite coating for an implantable micro-MEMS sensor according to an embodiment of the present invention is shown.

[0021] Figure 2 The schematic diagram illustrates a method for encapsulating a parylene composite coating for an implantable micro MEMS sensor according to an embodiment of the present invention. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0025] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0026] For the packaging of implantable MEMS (Micro-Electro-Mechanical System) devices, there are five main requirements: ultra-thinness, resistance to body fluid corrosion, high reliability, high biocompatibility, and minimal impact on sensor performance. Different application scenarios may require different packaging strategies to ensure optimal sensor performance under a range of physiological conditions. Among these, parylene coatings are widely used in MEMS due to their low permeability and the highest biocompatibility certification at the micrometer level. However, their poor adhesion and low thermal stability limit their application. Simple parylene coatings exhibit strong frictional shear stress with the sensor surface, resulting in poor adhesion and thus unreliable packaging. Regarding enhancing coating adhesion, there are currently two effective methods: one method involves adding an A-174 coupling agent as an adhesive layer between the MEMS surface and the parylene layer, effectively improving adhesion by forming covalent bonds. The other method involves using parylene copolymer films; due to the higher surface energy and the presence of Si-F bonds in CF copolymer films, they exhibit greater bonding strength compared to C and F films.

[0027] However, all of the above packaging methods suffer from technical problems such as excessively large packaging structures and decreased sensitivity, overall accuracy, and thermal stability after packaging.

[0028] Based on this, the present invention provides a parylene composite coating encapsulation method for implantable micro MEMS sensors, which solves the technical problems of excessively large encapsulation structures and decreased sensitivity, overall accuracy and thermal stability after encapsulation in existing MEMS sensor encapsulation methods.

[0029] The method includes: acquiring a MEMS sensor sample and cleaning the MEMS sensor sample; connecting wires to the pads of the cleaned MEMS sensor sample to form a conductive path, so that electrical signals can be transmitted from the inside of the MEMS sensor sample to the outside; sealing the uncoated area of ​​the MEMS sensor sample; placing the sealed MEMS sensor sample into a packaging system, adding parylene raw material for encapsulation to obtain a parylene coating, wherein the packaging system is configured as a vacuum environment.

[0030] The parylene composite coating encapsulation method for implantable micro MEMS sensors provided in this invention uses smaller and more precise parylene raw materials (such as C powder, F powder, and mixtures of C powder and F powder) for encapsulation, achieving an ultra-thin encapsulation structure that meets the volume requirements of implantable micro MEMS sensors.

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0032] Figure 1 A flowchart illustrating a method for encapsulating a parylene composite coating for an implantable micro-MEMS sensor according to an embodiment of the present invention is shown.

[0033] like Figure 1 As shown, the parylene composite coating encapsulation method for implantable micro MEMS sensors in this embodiment may include, for example, operations S1 to S5.

[0034] In operation S1, a MEMS sensor sample is acquired and cleaned.

[0035] In operation S2, wires are connected to the pads of the cleaned MEMS sensor sample to form a conductive path, enabling electrical signals to be transmitted from the inside of the MEMS sensor sample to the outside.

[0036] In operation S3, the uncoated areas of the MEMS sensor sample are sealed.

[0037] In operation S4, the sealed MEMS sensor sample is placed into the packaging system, and parylene is added for packaging to obtain a parylene coating. The packaging system is configured as a vacuum environment.

[0038] In this embodiment, after obtaining the MEMS sensor sample, the MEMS sensor sample is cleaned. For example, a lint-free cloth and alcohol from the production area can be used to clean the surface of the MEMS sensor sample.

[0039] Then, leads are made on the pads of the MEMS sensor sample to connect electrical signals. These leads can be, for example, aluminum wires or gold wires.

[0040] Next, a special adhesive material and removable glue are applied to the uncoated areas (i.e., areas that do not require coating) to seal the gaps. For example, masking tape and red glue can be used, with the red glue acting as a sealant.

[0041] Finally, the MEMS sensor sample is placed into the packaging system (i.e., the parylene coating system), and parylene raw material is added for packaging to obtain the parylene coating. The parylene raw material is gradually heated under preset temperature conditions, and then rises into gaseous molecules. The gaseous molecules are decomposed into monomer molecules in the pyrolysis chamber at 680°C and pressure below 0.026 torr, and then deposited and polymerized into a thin film layer in the deposition chamber.

[0042] During the process, the indoor temperature is 40±5℃, and the packaging system is configured as a vacuum environment with the pressure value controlled below 0.026 torr.

[0043] According to embodiments of the present invention, a sealed MEMS sensor sample is placed into a packaging system, and parylene is added for encapsulation to obtain a parylene coating. Specifically, this can be divided into the following three cases:

[0044] In some embodiments, parylene C powder can be added separately for encapsulation to obtain a parylene C coating.

[0045] The poly(p-xylene) C powder was gradually heated at 60℃ to 100℃ to obtain a poly(p-xylene) C coating. During the gradual heating process, the temperature increased by 2℃ every 20 minutes.

[0046] As a preferred embodiment, the parylene C powder can be gradually heated at 80°C to obtain a parylene C coating.

[0047] In some embodiments, parylene F powder can be added separately for encapsulation to obtain a parylene F coating.

[0048] The parylene F powder was gradually heated at 40℃ to 80℃ to obtain a parylene F coating. During the gradual heating process, the temperature increased by 2℃ every 30 minutes.

[0049] As a preferred embodiment, the parylene F powder can be gradually heated at 60°C to obtain a parylene F coating.

[0050] In some embodiments, parylene C powder and parylene F powder mixed in a preset ratio can also be added for encapsulation to obtain a parylene CF copolymer film coating. For example, parylene C powder and parylene F powder are mixed in a certain ratio, wherein the mixing ratio is C. x :F y Where 1≤x≤10, 1≤y≤10. By adjusting the mixing ratio of parylene C powder and parylene F powder, the properties of the coating can be optimized for different application requirements.

[0051] The mixture of parylene C powder and parylene F powder is gradually heated at 60℃ to 100℃ to obtain a parylene CF copolymer film coating. During the gradual heating process, the temperature rises by 2℃ every 20 minutes.

[0052] As a preferred embodiment, the mixing ratio of parylene C powder and parylene F can be 1:5, and the mixture is gradually heated at 80°C to obtain a parylene C1F5 copolymer film coating.

[0053] The parylene composite coating encapsulation method for implantable micro MEMS sensors provided in this invention uses smaller and more precise parylene raw materials (such as C powder, F powder, and mixtures of C powder and F powder) for encapsulation, achieving an ultra-thin encapsulation structure that meets the volume requirements of implantable micro MEMS sensors.

[0054] According to an embodiment of the present invention, considering the technical problem of the excessive size of existing MEMS sensor packaging structures, the thickness of the parylene coating can be set to 0.5μm-10μm.

[0055] According to an embodiment of the present invention, during the process of placing the sealed MEMS sensor sample into the packaging system and adding parylene raw material for packaging, a coupling agent may also be added, wherein the coupling agent is used to improve the adhesion of the parylene coating.

[0056] In this embodiment, for example, A-174 coupling agent can be added to parylene C powder to obtain a parylene C+A174 coating to increase adhesion. The thickness of the coupling agent can be 500nm-1000nm.

[0057] The parylene composite coating encapsulation method for implantable micro MEMS sensors provided in this invention effectively enhances the adhesion of the parylene coating by introducing a coupling agent, thus solving the technical problem of low thermal stability of the parylene coating.

[0058] Figure 2 The schematic diagram illustrates a method for encapsulating a parylene composite coating for an implantable micro MEMS sensor according to an embodiment of the present invention.

[0059] like Figure 2 As shown, the principle of the parylene composite coating encapsulation method for implantable micro MEMS sensors in this embodiment of the invention mainly includes:

[0060] Cleaning, wire bonding, and coating deposition of MEMS sensor samples.

[0061] Regarding the cleaning process of MEMS sensor samples, for example, lint-free cloths and alcohol from the production area can be used to clean the surface of the MEMS sensor samples.

[0062] Regarding the wire bonding process for MEMS sensor samples, aluminum and gold wires can be used to connect electrical signals. The main purposes of connecting electrical signals include the following three aspects:

[0063] Firstly, it enables external signal reading, transmitting the electrical signals collected by MEMS sensors to external instruments or systems for data processing and monitoring.

[0064] Secondly, it facilitates the packaging process. During the subsequent coating and packaging process, the lead wires protect the pads and electrical connections from being covered by the coating, ensuring the integrity of signal transmission.

[0065] Third, it supports sensor function testing. Functional verification can be performed through these leads before packaging to ensure that the sensor performance meets the requirements.

[0066] Regarding the deposition coating treatment of MEMS sensor samples, for example, parylene raw materials (C powder, F powder, and mixtures of C powder and F powder) can be gradually heated under preset temperature conditions, rising into gaseous molecules. The gaseous molecules are then decomposed into monomer molecules in a pyrolysis chamber at 680°C and a pressure below 0.026 torr, and deposited and polymerized into a thin film layer in a deposition chamber.

[0067] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or pairings fall within the scope of this invention.

[0068] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A poly-para-xylylene composite coating encapsulation method for an implantable micro MEMS sensor, characterized in that, The method includes: Obtain a MEMS sensor sample and clean the MEMS sensor sample. Wires are connected to the pads of the cleaned MEMS sensor sample to form a conductive path, enabling electrical signals to be transmitted from the inside of the MEMS sensor sample to the outside. The uncoated areas of the MEMS sensor sample are sealed. The sealed MEMS sensor sample is placed into the packaging system, and parylene is added for encapsulation to obtain a parylene coating. The packaging system is configured as a vacuum environment.

2. The method according to claim 1, characterized in that, The step of placing the sealed MEMS sensor sample into the packaging system, adding parylene raw material for packaging, and obtaining a parylene coating includes: The sealed MEMS sensor sample was placed into the packaging system, and parylene C powder was added for packaging to obtain a parylene C coating. The parylene C powder is gradually heated at 60°C to 100°C to obtain the parylene C coating.

3. The method according to claim 1, characterized in that, The step of placing the sealed MEMS sensor sample into the packaging system, adding parylene raw material for packaging, and obtaining a parylene coating includes: The sealed MEMS sensor sample was placed into the packaging system, and parylene F powder was added for packaging to obtain a parylene F coating. The parylene F powder is gradually heated at 40°C to 80°C to obtain the parylene F coating.

4. The method according to claim 1, characterized in that, The step of placing the sealed MEMS sensor sample into the packaging system, adding parylene raw material for packaging, and obtaining a parylene coating includes: The sealed MEMS sensor sample was placed into the packaging system, and parylene C powder and parylene F powder mixed in a preset ratio were added for packaging to obtain a parylene CF copolymer film coating. The mixture of parylene C powder and parylene F powder is gradually heated at 60°C to 100°C to obtain the parylene CF copolymer film coating.

5. The method according to any one of claims 1 to 4, characterized in that, The step of placing the sealed MEMS sensor sample into the packaging system, adding parylene raw material for packaging, and obtaining a parylene coating further includes: The sealed MEMS sensor sample is placed into the packaging system, and a coupling agent is added for encapsulation. The coupling agent is used to improve the adhesion of the parylene coating.

6. The method according to claim 5, characterized in that, The thickness of the coupling agent is 500nm-1000nm.

7. The method according to claim 5, characterized in that, The thickness of the parylene coating is 0.5 μm-10 μm.

8. The method according to claim 1, characterized in that, The cleaning process for the MEMS sensor sample includes: The surface of the MEMS sensor sample was cleaned using a lint-free cloth and alcohol.

9. The method according to claim 1, characterized in that, The conductors include aluminum wire and gold wire.

10. The method according to claim 1, characterized in that, The pressure value of the vacuum environment is less than 0.026 torr.

Images