Injection molding method for capacitive sensor, bluetooth capacitive sensor, vehicle door handle, and vehicle

Abstract

The present application relates to the field of injection molding, and discloses an injection molding method for a capacitive sensor. The sensor is formed by at least two times of injection molding. According to the method, the sensor is at least divided into a PCBA board, an inner molded body and an outer molded body from inside to outside; the PCBA board comprises a capacitor area, and the capacitor area is configured to protrude from the plane where the PCBA board is located; the inner molded body has positioning supporting points. During injection molding, the inner molded body is first formed by means of injection molding, wherein the inner molded body covers the area of the PCBA board other than the capacitor area and other than the positioning supporting points of the inner molded body; and then the outer molded body is formed by means of injection molding, wherein the outer molded body completely covers the remaining area which is not covered by the inner molded body, and the inner molded body. By means of the design of two times of low-pressure injection molding, the material of the first injection molding is effectively combined with the material of the second injection molding, and it is verified by means of actual measurement that the present application can pass 300-hour 60°C water soaking verification and meets IPX9K waterproof requirements.

Description

Injection molding method of capacitive sensor, Bluetooth capacitive sensor, handlebar and vehicle

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on June 30, 2023, with application number 202310794386.7 and invention name “Injection molding method of capacitive sensor, Bluetooth capacitive sensor, handlebar and vehicle”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of injection molding, specifically to low-pressure injection molding, including an injection molding method of a capacitive sensor, especially to a Bluetooth capacitive sensor and a handlebar for a Bluetooth capacitive sensor, and also specifically to a vehicle including a handlebar with a Bluetooth capacitive sensor. Background Art

[0003] In the current digital key industry, door handles are an optimal placement option for Bluetooth signals due to their location near the center of the vehicle and their plastic cover. However, to meet requirements for wind resistance and styling, more and more automakers are opting for concealed door handles. Concealed handles offer limited space for sensors, typically measuring only 18-20mm wide and 7-8mm thick. Bluetooth capacitive sensors typically require six functional lines: power, ground, Controller Area Network High (CANH) and CAN Low (CANL), a capacitor hard line, and left and right identification pins. Current waterproof connectors on the market struggle to meet these dimensions, so a cable-swinging arrangement is often used. However, the unique design of the handlebars makes it difficult to provide adequate drainage. This creates gaps in the handlebar cover, often with a removal port. Water can enter through these gaps and the removal port, accumulating inside the door handle cavity and potentially penetrating the electronic components within the handle, significantly increasing the waterproofing challenge.

[0004] However, the Bluetooth capacitive sensors placed on door handles mainly use two processes: potting and low-pressure injection molding for waterproofing. Some use laser welding plus dispensing or dispensing. If the dispensing solution is used, it is difficult to form a good combination between the wiring harness and the housing through dispensing. In addition, the hidden door handle has a lot of movement, including linear push-out, unfolding, and manual side pulling, which will cause the wiring harness to move. After the wiring harness moves repeatedly, it is easy for the dispensing seal to be poor and cause water to enter. If the glue solution is used, a higher level of waterproofing can be achieved under the premise of proper material selection and matching. However, due to the complexity of the glue filling process, it is easy to generate trapped air and form bubbles in evenly distributed thicker and smaller locations. Capacitive touch has strict consistency requirements on the dielectric constant of the touch area medium, and does not allow bubbles to appear in a large range of lines. Therefore, it is generally necessary to cooperate with vacuum equipment to achieve the effect of removing bubbles. The process is complex and the cost is high.

[0005] Low-pressure injection molding is an injection molding technology that heats thermoplastic plastic material to a molten state and then injects it into the mold through an injection molding machine to form the desired product under a certain pressure.

[0006] Although the low-pressure injection molding process is simple and quick to form, it is limited by the bonding properties of the materials. When a plastic shell plus low-pressure injection molding solution is used, actual tests show that it cannot pass higher-level waterproof tests than IPX7 in the International Protection Marking (IEC 60529), such as IPX8 and IPX9K.

[0007] Therefore, in order to overcome the above problems, the applicant designed a method of injection molding a capacitive sensor through two low-pressure injection molding processes. Technical issues

[0008] One of the purposes of the embodiments of the present application is to provide an injection molding method for a capacitive sensor, a Bluetooth capacitive sensor, a handlebar, and a vehicle, which can achieve an effective combination of the first injection molding and the second injection molding materials based on the design of low-pressure injection molding for the capacitive sensor. Actual measurements have verified that it can pass 300 hours of 60°C water immersion verification and meet the IPX9K level waterproof requirements. Technical Solutions

[0009] The purpose of this application is to solve the above technical problems, and the technical solutions adopted are:

[0010] In a first aspect, the present application provides an injection molding method for a capacitive sensor, which undergoes at least two injection moldings. The method divides the capacitive sensor from the inside to the outside into at least three parts: a PCBA board, an inner mold, and an outer mold, wherein the PCBA board has a capacitor area, and the capacitor area is configured to protrude from the plane where the PCBA board is located. The inner mold has a positioning support point. During injection molding, the inner mold is first injected, and the inner mold covers all areas of the PCBA board except the capacitor area and the positioning support point. Then, the outer mold is injected, and the outer mold completely covers the remaining area not covered by the inner mold and the inner mold.

[0011] The low-pressure injection molding process is simple, environmentally friendly, and highly efficient. It can also prevent bubbles from forming in the capacitor area, effectively ensuring touch consistency.

[0012] Door handles remain a preferred placement for digital keys. However, hidden door handles inherently lack water protection and are prone to water accumulation, placing higher demands on the sensor's waterproof design. Furthermore, the integrated capacitive touch function demands high consistency, preventing the formation of large bubbles. This design, based on a low-pressure injection molding process, optimizes its waterproof performance, employing a two-shot low-pressure injection molding process to effectively combine the materials of the first and second injections.

[0013] The present application utilizes secondary low-pressure injection molding, combined with two injection moldings of inner mold and outer mold. The same material is used for both moldings. After the inner mold is injected, it is placed in the mold of the outer mold for injection molding again. Under the action of high temperature and pressure of the mold, excellent bonding is formed. It is measured that the inner and outer molds can withstand a tensile force of more than 300N without cracking.

[0014] In some embodiments, the inner mold has an inwardly recessed portion forming a groove site. After the inner mold is injection-molded, the groove site of the inner mold causes at least a portion of the PCBA board to be exposed.

[0015] Moreover, the length between the exposed portion of the PCBA board and the positioning support point is more than 3 mm.

[0016] The exposed areas are support ribs, known as support ribs. Their primary function is to create a gap between the PCBA and the inner mold cavity to facilitate glue injection. The presence of the support ribs allows the glue to fully fill the gap between the PCBA and the inner mold cavity, ensuring quality and precision in glue injection.

[0017] Furthermore, more and denser support ribs can effectively reduce strain on the PCBA. Strain is the deformation of a material under load. Excessive strain can cause problems such as cracking or deformation on the PCBA. Therefore, increasing the number and density of support ribs can improve the strength and stability of the PCBA and reduce the effects of strain.

[0018] After the inner mold is injected, the outer mold is immediately injected. This provides some protection against static electricity, preventing damage to the PCBA during the injection molding process. Static electricity is often destructive to electronic components, so when handling PCBAs, care must be taken to prevent the generation and conduction of static electricity to ensure product quality and reliability.

[0019] Improve the reliability, operating temperature control, maintenance efficiency and anti-interference ability of electronic equipment, thereby improving product quality and performance.

[0020] In some embodiments, the positioning support points are configured as outwardly extending parts, wherein there are at least two positioning support points evenly arranged, and the distance between the two positioning support points is within 50 mm.

[0021] By evenly distributing at least two positioning support points, the PCBA board is better positioned and used for positioning and fixing the second injection molding on the outer mold. This reduces the shaking and displacement of the PCBA board, improves the stability of the entire electronic device, and reduces instability caused by transportation or mechanical vibration.

[0022] By setting two or more positioning support points, better alignment guidance can be provided during the installation process. Operators can use the positioning support points to ensure that the PCBA board is correctly placed and aligned with other components or connectors. This can improve assembly accuracy and efficiency, reducing assembly errors and adjustment steps.

[0023] Evenly spaced positioning support points provide balanced force distribution, reducing local stress concentration on the PCBA board. This helps reduce the risk of board deformation and improves the durability and long-term reliability of the PCBA board.

[0024] Enhance the stability, assembly accuracy, durability, and maintenance convenience of electronic equipment. Help improve product quality, reduce the risk of failure, and simplify production and maintenance processes.

[0025] In some embodiments, the positioning support point is a convex point protruding outward, and the convex point is configured as a hemispherical point shape, forming a point contact with the inner cavity surface of the outer mold core.

[0026] The inner mold support positioning design is a hemispherical point, which forms point contact with the inner cavity surface of the outer mold core, so that the inner mold has as little contact with the outside world as possible. After the outer mold is injected, the inner mold is only in contact with the outside world at the support positioning point, reducing the risk of water ingress.

[0027] The use of hemispherical positioning support points can provide more precise positioning. The hemispherical bumps can provide a stable positioning position when forming point contact with the inner cavity surface of the outer mold core, ensuring accurate positioning and alignment of the PCBA board.

[0028] The hemispherical dot shape provides uniform contact pressure distribution. This helps optimize force transmission and dispersion, reducing the risk of stress concentration on the PCBA board. By properly distributing force, localized stress concentration can be reduced, improving the durability and reliability of the PCBA board.

[0029] Using hemispherical bumps increases the contact area of ​​the positioning support points. This improves the PCBA's ability to resist shock and vibration. The hemispherical bumps absorb and disperse external vibration energy, reducing impact on the PCBA and protecting the integrity of electronic components.

[0030] The hemispherical point shape enables precise positioning, optimizes force transmission, and enhances vibration resistance, helping to improve assembly quality and protect the integrity of the PCBA board.

[0031] Preferably, the gap between the capacitor area and the inner cavity surface of the inner mold is within 0.2 mm.

[0032] Preferably, the gap between the capacitor area and the inner cavity surface of the mold core of the outer mold is between 0.9 mm and 1 mm.

[0033] The incremental value of capacitive touch is inversely proportional to the sensing distance, which should be minimized. Since low-pressure injection molding has a minimum wall thickness requirement of approximately 0.9mm, the capacitor area should be within 0.2mm of the inner cavity of the inner mold to prevent the rubber from flowing into this area. The outer mold completely wraps the capacitor area, and the inner cavity of the outer mold should be 0.9mm-1mm away from the capacitor area. The wall thickness here is relatively thin, so a vent insert should be made to avoid trapped air, which may lead to incomplete injection and leakage from the inner mold, resulting in water ingress.

[0034] Furthermore, it effectively reduces movement and vibration of the capacitor during installation and use. This prevents collisions, damage, and unstable contact, thereby improving its reliability and service life. Appropriate gap distances provide isolation and shielding, reducing the impact of external electromagnetic interference on the capacitor.

[0035] Improve assembly accuracy and consistency. Appropriate gap distance helps accurately place the capacitor and make it fit tightly with the inner cavity surface of the mold core, improving the assembly accuracy and reliability of the PCBA board.

[0036] It can also provide appropriate space to optimize heat dissipation. Appropriate gap distance can promote air flow, improve heat dissipation efficiency, effectively reduce capacitor temperature, and extend its life and performance stability.

[0037] In a second aspect, the present application provides a Bluetooth capacitive sensor, which is injection molded using the above method.

[0038] In a third aspect, the present application provides a handlebar comprising a housing and the aforementioned Bluetooth capacitive sensor.

[0039] In a fourth aspect, the present application provides a vehicle comprising a vehicle body and the handlebar. Beneficial effects

[0040] The first aspect of the present application provides a method for injection molding a capacitive sensor. The capacitive sensor, which has undergone at least two injection molding processes, is divided into at least three parts, from the inside out, including a PCBA board, an inner mold, and an outer mold. The PCBA board has a capacitor area configured to protrude from the plane of the PCBA board. The inner mold has positioning support points. During injection molding, the inner mold is first injected, and the inner mold covers all areas of the PCBA board except the capacitor area and the inner mold support positioning points. The outer mold is then injected, and the outer mold completely covers the remaining areas not covered by the inner mold and the inner mold. The design of two low-pressure injection moldings is used to effectively combine the materials of the first and second injection molding processes. Actual measurements have verified that it can pass 300 hours of 60°C water immersion verification and IPX9K waterproof requirements.

[0041] It can be understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] FIG1 is an exploded view of a capacitive sensor provided by some embodiments of the present application;

[0044] FIG2 is a diagram of a sample capacitive sensor applied to a handlebar provided by some embodiments of the present application;

[0045] FIG3 is a schematic diagram of an inner mold after the first injection molding provided by some embodiments of the present application;

[0046] FIG4 is an enlarged view of point A in FIG3 ;

[0047] FIG5 is an experimental diagram of step 1 of the IPX9K test of the sample;

[0048] FIG6 is an experimental diagram of step 2 of the IPX9K test of the sample;

[0049] FIG7 is an experimental diagram of step 3 of the IPX9K test of the sample;

[0050] FIG8 is an experimental diagram of step 4 of the IPX9K test of the sample;

[0051] In the figure: PCBA board 1, inner mold 2, outer mold 3, capacitor area 4, positioning support point 5, slot point 6, PCBA board exposed part 7, silicone pad 8, sample 9. Modes for Carrying Out the Invention

[0052] The following further illustrates the present application in conjunction with the accompanying drawings and implementation methods. The positional relationship described in the text is consistent with the positional relationship direction of the accompanying drawings themselves. It is only for the convenience of description and does not limit the structure of the present application.

[0053] In this embodiment, a two-stage low-pressure injection molding process is employed. The PCBA board 1 has a protruding capacitor area 4, known as a capacitor pad, for soldering capacitors, as shown in Figure 1. First, the inner mold 2 is injection-molded, covering the PCBA board. The extended portion of the outer surface of the injection-molded inner mold has a positioning support point 5, designed in a hemispherical shape, forming point contact with the inner cavity surface of the outer mold core. Alternatively, a conical shape or other shape can be employed. Simultaneously, the inner mold forms an inwardly recessed portion, known as a slot point 6. The structure of the inner mold is shown in Figure 3. The slot point allows the PCBA board to be exposed. As shown in Figure 4, the inner mold 2 presses against the exposed portion 7 of the PCBA board. The inner mold covers all areas of the PCBA board except the capacitor area and the positioning support point. The glue thickness on both sides of the inner mold PCBA board is evenly distributed to prevent warping and damage caused by uneven shrinkage of the glue after injection molding. The outer mold 3 is then injection-molded, completely covering the remaining area not covered by the inner mold and the inner mold. A silicone pad 8 is also provided on the outer surface of the outer mold 3, corresponding to the capacitor area 4.

[0054] Specifically, two positioning support points 5 are set on both sides of the inner mold, with a distance of L1 = 50mm between them. While the positioning support points 5 are evenly distributed on the upper surface of the inner mold as shown in Figure 3, symmetrical and corresponding positioning support points can be set on other sides of the inner mold, such as the upper and lower surfaces. The distance between the exposed portion of the PCBA and the positioning support points shown in Figure 3 is L2 = 3mm.

[0055] In addition, the process requirements of this example stipulate that the gap between the capacitor area and the inner cavity of the inner mold is 0.2 mm, and the gap between the capacitor area and the inner cavity of the outer mold is 0.9 mm.

[0056] The PCBA board was first connected to the PVC-SR and PVC wiring harness, and then two low-pressure injection moldings were performed, first injecting the inner mold and then the outer mold, to form sample 9 as shown in Figure 2.

[0057] The above samples are now subjected to the following two waterproof tests.

[0058] Experiment 1, IPX9K test, rain spray test, determines the waterproof ability of the sample.

[0059] In the IPX9K test, the device is exposed to high-pressure water jets to simulate harsh environmental conditions, such as extreme rain or water pressure encountered during cleaning. During the test, the water jet is sprayed at high speed and at different angles to ensure that the device can effectively prevent water penetration.

[0060] Experimental steps (as described in Figures 5-8):

[0061] Step 1: Confirm the appearance of the prototype before the experiment: sample appearance inspection, sample function inspection.

[0062] Step 2: Place the samples into the IPX9K rain test chamber.

[0063] Step 3: Set the spray flow, pressure, time, angle, etc. and conduct the experiment.

[0064] Step 4: Confirm the appearance of the prototype after the experiment: sample appearance inspection, sample function inspection.

[0065] Table 1 IPX9K test results

[0066] Experiment 2, high temperature water test.

[0067] The waterproof performance of the samples was tested by soaking them in water at 60° for different lengths of time.

[0068] Sample Status: Model A: Overmolded, PCBA without conformal coating; Model B: Overmolded, PCBA with conformal coating. "Without conformal coating" means no waterproof, dustproof, or moisture-proof coatings were used during the PCBA manufacturing process. Conformal coating is a special coating commonly used to protect electronic devices from water, dust, and humidity.

[0069] Test conditions:

[0070] 1. Test after soaking in salt water for 1 hour.

[0071] 2. No electricity, soak in water at 60 degrees Celsius for 30 days, tested every day. (Only some days are shown in the table)

[0072] Table 2 Test data results of Model A

[0073] Table 3 Test data results of Model B

[0074] Actual tests have verified that it can pass the IPX9K waterproof requirement and 300 hours of 60°C water immersion verification.

[0075] The present application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present application.

Claims

1. A method for injection molding a capacitive sensor, characterized in that: The capacitive sensor is subjected to at least two injection moldings, and the method divides the capacitive sensor into at least three parts from the inside to the outside, namely, an assembled printed circuit board (PCBA), an inner mold, and an outer mold, wherein the PCBA board has a capacitor area, the capacitor area is configured to protrude from the plane where the PCBA board is located, and the inner mold has a positioning support point; During injection molding, the inner mold is firstly injected, and the inner mold covers all areas of the PCBA board except the capacitor area and the positioning support points. Then the outer mold is injected, and the outer mold completely covers the remaining area not covered by the inner mold and the inner mold.

2. The method for injection molding a capacitive sensor according to claim 1, characterized in that: The inner mold has an inwardly recessed portion to form a groove point. When the inner mold is injection-molded, the groove point of the inner mold causes at least a portion of the PCBA board to be exposed.

3. The method for injection molding a capacitive sensor according to claim 2, characterized in that: The distance between the exposed part of the PCBA board and the positioning support point is more than 3 mm.

4. The method for injection molding a capacitive sensor according to claim 3, characterized in that: The exposed portion of the PCBA board is used as a supporting rib to form a gap between the PCBA board and the mold cavity of the inner mold to facilitate glue injection.

5. The method for injection molding a capacitive sensor according to claim 1, characterized in that: The positioning support points are configured as outwardly extending parts, wherein at least two positioning support points are evenly arranged, and the distance between every two positioning support points is within 50 mm.

6. The method for injection molding a capacitive sensor according to claim 5, characterized in that: Two positioning support points are arranged on both side edges of the inner mold, and the positioning support points are evenly arranged on the upper surface of the inner mold.

7. The method for injection molding a capacitive sensor according to claim 6, characterized in that: The positioning support point is a convex point protruding outward, and the convex point forms a point contact with the inner cavity surface of the mold core of the outer mold.

8. The method for injection molding a capacitive sensor according to claim 7, characterized in that: The convex point is configured in any one of a hemispherical point shape and a cone shape.

9. The method for injection molding a capacitive sensor according to claim 1, characterized in that: The gap between the capacitor area and the inner cavity surface of the inner mold is within 0.2 mm.

10. The method for injection molding a capacitive sensor according to claim 1, characterized in that: The gap distance between the capacitor area and the inner cavity surface of the mold core of the outer mold is between 0.9mm and 1mm.

11. The method for injection molding a capacitive sensor according to claim 1, characterized in that: A silicone pad is provided on the outer surface of the outer mold at a position corresponding to the capacitor area.

12. The method for injection molding a capacitive sensor according to any one of claims 1 to 11, characterized in that: The PCBA board is sprayed with a coating material, and the coating material is used to protect the PCBA board from erosion by water, dust and a humid environment.

13. A Bluetooth capacitive sensor, characterized in that: The method is injection molded according to any one of claims 1 to 12.

14. A handlebar, characterized in that: The device comprises a housing and the Bluetooth capacitive sensor as claimed in claim 13.

15. A vehicle, characterized in that: The vehicle comprises a vehicle body and the handlebar as claimed in claim 14.

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