Pad structure, pressure sensor and preparation method, exhaust gas recirculation system and vehicle

Abstract

The application provides a pad structure, a pressure sensor and a preparation method, an exhaust gas recirculation system and a vehicle, and relates to the technical field of vehicles.The pad structure comprises a pad base body, the pad base body comprises a base material layer, a nickel plating layer and a gold plating layer arranged on the base material layer in sequence, the surface of the gold plating layer of the pad base body is divided into a bonding area and a non-bonding area, the bonding area is used for being connected with a bonding wire, the non-bonding area is used for being connected with a protective glue, a plurality of grooves are formed in the non-bonding area, the distance from the surface of the gold plating layer away from the nickel plating layer to the groove bottom is greater than or equal to the thickness of the gold plating layer and less than or equal to the sum of the thicknesses of the gold plating layer and the nickel plating layer.The pad structure has a gold-plated bonding surface and a nickel-exposed non-bonding surface, can enhance the corrosion performance and welding strength of the pad structure, and can improve the adhesion of the protective glue and the surface of the pad plating layer.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and more specifically, to a pad structure, a pressure sensor and its preparation method, an exhaust gas recirculation system, and a vehicle. Background Technology

[0002] In recent years, with increasingly stringent emission standards, exhaust gas recirculation (EGR) technology has been gradually applied to gasoline engines, becoming a trend in the automotive industry. Gasoline engine exhaust contains a certain amount of unburned fuel vapor and corrosive combustion products. The EGR system can introduce a portion of the exhaust gas into the combustion chamber, allowing the fuel vapor that would otherwise be released into the atmosphere to mix with fresh air and re-combust. This saves fuel and reduces exhaust pollutants. However, automotive exhaust is hot and contains large amounts of hydrocarbons, water, nitrogen oxides, sulfides, and other corrosive elements. After mixing with fresh air, it needs to be cooled by a cooler, easily producing condensation in the intake system. This leads to a rapid increase in hydrocarbon and water vapor concentrations in the intake system. Therefore, gasoline engines install multiple pressure sensors or differential pressure sensors in the intake system to detect gas pressure at different locations, measure exhaust gas flow and air-fuel mixture flow, and ultimately precisely control the fuel injection quantity to achieve the optimal air-fuel ratio. Therefore, during the exhaust gas recirculation process of automobiles, these pressure sensors come into contact with the exhaust gases, and high concentrations of hydrocarbons, humidity, and corrosive substances can have a significant impact on the pressure sensors.

[0003] The structure of a pressure sensor includes components such as a circuit board, a pressure chip, solder pads, and bonding wires. The pressure chip, as a pressure-sensitive element, is the core component in manufacturing the pressure sensor. The pressure chip is fixed to the circuit board and connected to it via bonding wires. Solder pads are small metal sheets used for soldering the bonding wires. In related technologies, the pressure sensor also uses silicone rubber to cover the surfaces of the pressure chip, solder pads, and bonding wires to protect these components from corrosion, oxidation, and external damage. However, in exhaust gas recirculation (EGR) applications, automotive exhaust contains high concentrations of nitrogen oxides, sulfides, halogens, hydrocarbons, and other humid and corrosive substances. Ordinary silicone rubber is not oil-resistant, has weak corrosion resistance, and insufficient chemical stability, making it unable to resist the corrosion of high concentrations of humid and corrosive substances. This makes the protective rubber surface easily oxidized and corroded, leading to the peeling of the protective rubber from the solder pad surface, and subsequently, problems such as bonding wire breakage. This causes pressure sensor performance failure, resulting in a high failure rate. Ultimately, this prevents the electronic control unit from measuring the intake system gas pressure in real time, severely affecting the power, economy, and emission performance of gasoline engines. Summary of the Invention

[0004] The problem this invention aims to solve is that the bonding force between the solder pads and the protective adhesive in pressure sensors is not strong, which easily leads to the peeling of the protective adhesive from the solder pads, resulting in the breakage of the bonding wires and causing the pressure sensor to fail.

[0005] To address the aforementioned problems, a first aspect of the present invention provides a pad structure, comprising: a pad substrate, the pad substrate including a substrate layer and a nickel plating layer and a gold plating layer sequentially disposed on the substrate layer, wherein the surface of the gold plating layer away from the nickel plating layer is divided into a bonding region and a non-bonding region, the bonding region being used for connection with bonding wires, the non-bonding region being used for connection with protective adhesive, the non-bonding region forming a plurality of grooves, and the distance from the surface of the gold plating layer away from the nickel plating layer to the bottom of the grooves being greater than or equal to the thickness of the gold plating layer, and less than or equal to the sum of the thicknesses of the gold plating layer and the nickel plating layer.

[0006] Preferably, the plurality of grooves are arranged in an array on the surface of the gold plating layer away from the nickel plating layer.

[0007] Preferably, the cross-sectional size of the groove gradually decreases along the direction from the gold plating layer toward the nickel plating layer.

[0008] Preferably, the groove is an arc-shaped groove.

[0009] The advantages of the pad structure of this invention compared to the prior art are as follows:

[0010] The pad structure of this invention enhances corrosion resistance by depositing a gold plating layer on the surface of the pad substrate. Simultaneously, the surface of the gold plating layer is divided into two regions: a bonding region and a non-bonding region. Multiple grooves are formed on the non-bonding region, creating an alternating surface that increases its roughness and improves the bonding strength between the pad structure and other components. For example, when the pad structure is used in a pressure sensor, the surface of the pad structure is covered with a protective adhesive. Since the non-bonding region is used to connect with the protective adhesive, and the increased roughness of the non-bonding region improves the adhesion between the pad structure and the protective adhesive, thereby reducing the risk of the protective adhesive peeling off the pad structure. Furthermore, since the distance from the surface of the gold plating layer away from the nickel plating layer to the bottom of the groove (i.e., the depth of the groove) is greater than or equal to the thickness of the gold plating layer, or in other words, the groove can just penetrate the gold plating layer or extend into the nickel plating layer, the groove area will expose at least part of the nickel plating layer of the pad substrate. The nickel plating layer will form strong hydrogen bonds with other components in contact with the inner wall of the groove, such as the protective adhesive, thus ensuring a strong bond between the nickel plating layer and the protective adhesive. This improves the adhesion between the pad structure and the protective adhesive, reducing the risk of protective adhesive peeling. Simultaneously, the depth of the groove will not exceed the sum of the thicknesses of the gold and nickel plating layers, meaning it will not expose the substrate layer of the pad substrate. Therefore, the protective adhesive used to cover the pad structure will inevitably connect with the exposed nickel plating layer within the groove to ensure the bonding strength between the pad structure and the protective adhesive, without damaging the substrate layer of the pad substrate and affecting the strength of the pad substrate itself.

[0011] A second aspect of the present invention provides a pressure sensor, comprising a substrate, a pressure chip, a pad structure as described above, and a protective adhesive, wherein the pressure chip is disposed on the substrate, the pad structure is disposed on the substrate and the pressure chip respectively, and the protective adhesive is disposed on the substrate and covers the surfaces of the pressure chip and the pad structure.

[0012] Preferably, the pressure sensor further includes bonding wires for connecting the pad structure on the substrate and the pad structure on the pressure chip, and the bonding wires are connected to the bonding area of ​​the pad structure.

[0013] Preferably, the pressure sensor further includes a waterproof and breathable membrane covering the surface of the protective adhesive, the waterproof and breathable membrane comprising an expanded polytetrafluoroethylene microporous membrane.

[0014] The advantages of the pressure sensor of the present invention compared with the prior art are as follows:

[0015] The pressure sensor of this invention, due to its pad structure with gold-plated bonding surface and exposed nickel non-bonded surface, not only has strong chemical corrosion resistance and anti-fouling performance, but also enhances the corrosion resistance and welding strength of the pad structure while improving the adhesion between the protective adhesive and the pad plating surface. This makes the pressure sensor of this invention more widely applicable, and it can be used in harsh environments with high oxidation, high corrosion, high hydrocarbons and high humidity. Moreover, it has a simple structure, low cost, and is easy to operate and mass-produce.

[0016] A third aspect of the present invention provides a method for manufacturing a pressure sensor, used to manufacture the pressure sensor as described above, comprising:

[0017] A nickel plating layer is formed by plating nickel on the surface of the substrate layer, and a gold plating layer is formed by plating gold on the surface of the nickel plating layer to obtain the pad substrate.

[0018] The surface of the gold plating layer away from the nickel plating layer is divided into a bonding region and a non-bonding region. A laser is used to remove the gold plating layer or remove the gold plating layer and at least part of the nickel plating layer in the non-bonding region to form a groove, thereby obtaining a pad structure.

[0019] The substrate and the pad structure are integrally formed, and the pressure chip is integrally formed with the pad structure, and the pressure chip is mounted on the substrate;

[0020] The bonding wires connect the pressure chip and the pad structure on the substrate;

[0021] A protective adhesive is applied to the surfaces of the pressure chip, the pad structure, and the bonding wires.

[0022] A waterproof and breathable membrane is bonded to the surface of the protective adhesive to obtain a pressure sensor.

[0023] The advantages of the pressure sensor manufacturing method of the present invention compared with the prior art are as follows:

[0024] This invention employs a laser removal process to form multiple grooves on the gold-plated surface of the pad substrate, resulting in a non-bonded surface with alternating concave and convex areas. This enhances the adhesion between the pad structure and the protective adhesive, reduces the risk of the protective adhesive peeling off the pad structure, and improves the stability of the pressure sensor. Other advantages are the same as those of the pressure sensor compared to existing technologies, and will not be elaborated further here.

[0025] A fourth aspect of the present invention provides an exhaust gas recirculation system, including the pressure sensor described above.

[0026] A fifth aspect of the present invention provides a vehicle including the exhaust gas recirculation system described above.

[0027] The advantages of the exhaust gas recirculation system and vehicle of the present invention compared to the prior art are the same as the advantages of pressure sensors compared to the prior art, and will not be repeated here. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the surface of the pad structure in an embodiment of the present invention;

[0029] Figure 2 This is a cross-sectional schematic diagram of the pad structure in an embodiment of the present invention;

[0030] Figure 3 This is a cross-sectional schematic diagram of the pad structure covered by protective adhesive in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of forming a groove using a laser removal process in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the surface of the pad structure after laser removal process in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the pressure sensor structure in an embodiment of the present invention;

[0034] Figure 7 for Figure 6 Enlarged view of the partial structure of the solder pads and protective adhesive;

[0035] Figure 8 This is a schematic diagram of the test group in the laser roughening effect verification experiment of this invention embodiment;

[0036] Figure 9 The results of the tensile force test in the laser roughening effect verification experiment in this embodiment of the invention are shown.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Pad substrate; 11. Substrate layer; 12. Nickel plating layer; 13. Gold plating layer; 2. Protective adhesive; 3. Pressure chip; 4. Chip pad; 5. Waterproof and breathable membrane; 6. Bonding wire; 7. Terminal pad; 10. Bonding area; 20. Non-bonding area; 201. Groove. Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] To meet vehicle emission standards, exhaust gas recirculation has become a trend, leading some car engines to be equipped with exhaust gas recirculation (EGR) systems. During EGR, exhaust gases are mixed with air and cooled, which can cause condensation in the intake system, increasing the concentration of hydrocarbons and water vapor. Therefore, pressure or differential pressure sensors are installed in the intake system to detect gas pressure at different locations, measuring exhaust gas flow and mixed gas flow to control fuel injection and achieve the optimal air-fuel ratio. However, the high humidity and corrosive substances in exhaust gases can adversely affect the sensors, potentially causing them to malfunction. Therefore, related technologies typically use silicone rubber for protection, aluminum wire bonding between the pressure chip 3 and the pads, and the pad substrate is made of copper alloy, plated with nickel and then aluminum. However, on the one hand, high concentrations of hydrocarbons can expand the protective rubber, making it easier for exhaust gases to penetrate into the protective rubber, which in turn corrodes the protective rubber, pads, and bonding wires 6. This breaks the intermolecular forces between the rubber molecules and the pad plating, weakening the adhesion between the protective rubber and the pad plating, causing the rubber to peel off from the pad surface, generating a large number of bubbles, and further causing the bonding wires 6 to break. On the other hand, since the pressure chip 3 and the pads are bonded with aluminum wires, the aluminum wires are easily oxidized and corroded by automobile exhaust, resulting in increased stress on the aluminum wires and breakage, thus hindering signal transmission. Furthermore, the pads are plated with aluminum, which is easily oxidized by corrosive gases, causing the bonding wires 6 to detach and affecting sensor performance.

[0041] Please see Figure 1 , Figure 2 As shown, an embodiment of the present invention provides a pad structure comprising: a pad substrate 1, the pad substrate 1 including a substrate layer 11 and a nickel plating layer 12 and a gold plating layer 13 sequentially disposed on the substrate layer 11; the surface of the gold plating layer 13 away from the nickel plating layer 12 is divided into a bonding region 10 and a non-bonding region 20; the bonding region 10 is used to connect with a bonding wire 6; the non-bonding region 20 is used to connect with a protective adhesive 2; the non-bonding region 20 forms a plurality of grooves 201; the distance from the surface of the gold plating layer 13 away from the nickel plating layer 12 to the bottom of the groove 201 is greater than or equal to the thickness of the gold plating layer 13, and less than or equal to the sum of the thicknesses of the gold plating layer 13 and the nickel plating layer 12.

[0042] In this embodiment, the pad substrate 1 consists of a substrate layer 11 and a nickel layer and a gold layer sequentially electroplated on its surface. Because gold has relatively stable chemical properties and is not easily oxidized, it can resist corrosive substances in exhaust gases. Therefore, the corrosion resistance of the gold plating layer 13 is better than that of the aluminum plating in related designs. Thus, in this embodiment, the pad structure, by gold plating the surface of the pad substrate 1, reduces the risk of pad corrosion even after corrosive gases enter the protective adhesive 2.

[0043] However, considering that gold is a low-adhesion material and has weak intermolecular forces with the protective adhesive 2 (such as rubber), exhibiting weak van der Waals forces, when the pad structure is used in a pressure sensor, the high concentration of hydrocarbons in the exhaust gas causes the rubber to swell, making it easy for moisture to penetrate. When moisture penetrates the rubber, water molecules easily break the intermolecular forces (weak van der Waals forces) between the rubber and gold, reducing the adhesion between the rubber and the gold plating layer 13, and posing a risk of rubber peeling.

[0044] Therefore, in this embodiment, multiple grooves 201 are formed on the surface of the gold plating layer 13 away from the nickel plating layer 12, thereby obtaining a non-bonding region 20 containing the grooves 201. The distance between the bottom of the groove 201 and the surface of the gold plating layer 13 away from the nickel plating layer 12 (hereinafter also referred to as the depth of the groove 201) is greater than or equal to the thickness of the gold plating layer 13, and less than or equal to the sum of the thicknesses of the gold plating layer 13 and the nickel plating layer 12, so that the groove 201 area exposes at least a portion of the nickel plating layer 12 of the pad substrate 1. For example, multiple grooves 201 can be obtained by removing the surface of the gold plating layer 13 of the pad substrate 1 at multiple points through a removal process. Due to the removal of the gold plating layer 13, the nickel plating layer 12 will be exposed, while the grooves 201 are still filled with the gold plating layer 13. This makes the non-bonding region 20 a region with alternating concave and convex areas, thereby enhancing the surface roughness of the pad substrate 1. When the pad structure is applied to, for example, a pressure sensor, the protective adhesive 2 covers the surface of the pad structure. Since the protective adhesive 2 is a flexible material with a certain degree of adhesion, increasing the roughness of the pad substrate 1 is beneficial to increasing the bonding force between the protective rubber and the pad structure. Furthermore, since the area of ​​the groove 201 that contacts the rubber is exposed nickel, and there are strong hydrogen bonds between nickel and the rubber surface, the nickel plating layer 12 is firmly bonded to the rubber. Even if moisture penetration occurs, the hydrogen bonds can still be maintained, thereby increasing the adhesion between the pad substrate 1 and the rubber.

[0045] In this embodiment, the pad structure enhances corrosion resistance by providing a gold-plated layer 13 on the surface of the pad substrate 1. Simultaneously, a non-bonded area 20 with grooves 201 is provided to increase the roughness of the non-bonded area 20. By controlling the depth of the grooves 201, the protective adhesive 2 used to cover the pad structure can contact the exposed nickel-plated layer 12 within the groove 201 area. This utilizes the hydrogen bonds generated between the nickel-plated layer 12 and the rubber to improve the adhesion between the protective rubber and the surface of the pad plating, thus solving the problem of protective rubber peeling.

[0046] For example, a groove 201 can be formed by removing at least the gold plating layer 13 from the surface of the pad substrate 1. When only the gold plating layer 13 is removed from the surface of the pad substrate 1, the depth of the groove 201 is equal to the thickness of the gold plating layer 13. When the gold plating layer 13 and at least partially the nickel plating layer 12 are removed from the surface of the pad substrate 1, the depth of the groove 201 is greater than the thickness of the gold plating layer 13. Simultaneously, the depth of the groove 201 is controlled to be less than or equal to the sum of the thicknesses of the gold plating layer 13 and the nickel plating layer 12, thereby avoiding damage to the substrate layer 11 at the bottom of the pad substrate 1 after completely removing the nickel plating layer 12. Therefore, in this example, the groove 201 area exposes both the gold layer on the sidewalls and the nickel layer on the bottom wall, and the exposed bottom wall can be either the surface of the nickel plating layer 12 or the internal nickel layer of the nickel plating layer 12 (e.g., ...). Figure 4 As shown, this increases the roughness of the inner wall of the groove 201, which in turn helps to improve the bonding force between the pad structure and the protective rubber covering it when it is applied to the pressure sensor.

[0047] In some embodiments, the plurality of grooves 201 are arranged in an array on the surface of the gold plating layer 13 away from the nickel plating layer 12.

[0048] like Figure 1 As shown, the surface of the pad substrate 1 is divided into a bonding region 10 and a non-bonding region 20. In the non-bonding region 20, multiple grooves 201 are arrayed, thereby forming an alternating surface of unevenness on the non-bonding region 20, increasing the roughness of the non-bonding region 20. Of course, the multiple grooves 201 can also be distributed in other specific shapes. The uniform or non-uniform spacing between the multiple grooves 201, as well as the distribution density of the grooves 201, can all be designed according to actual needs.

[0049] In some embodiments, the cross-sectional size of the groove 201 gradually decreases along the direction from the gold plating layer 13 toward the nickel plating layer 12.

[0050] like Figure 2 As shown, the substrate layer 11, nickel plating layer 12, and gold plating layer 13 are arranged sequentially from bottom to top, gradually decreasing the cross-section of the groove 201 from top to bottom, making the groove 201 wedge-shaped or approximately wedge-shaped overall. Thus, as... Figure 3 As shown, when the pad structure is used, for example, in a pressure sensor, its surface is covered with protective rubber, which fills the groove 201. Since the groove 201 has different widths at the top and bottom, it helps to enhance the bonding strength between the protective rubber and the pad structure, further reducing the risk of rubber peeling.

[0051] In some embodiments, the vertical cross-sectional shape of the groove 201 includes one of V-shape, U-shape, "︺" shape and semi-circle; and / or, the cross-sectional shape of the groove 201 includes one of circle, ellipse and polygon.

[0052] This embodiment exemplarily discloses several forms of the groove 201, for example, Figure 1 The groove 201 shown has an elliptical cross-sectional shape. However, the cross-sectional shape of the groove 201 can also be a circle, rectangle, or other polygonal shapes. For example... Figure 2 The vertical cross-sectional shape of the groove 201 shown is semi-circular, indicating that the groove 201 is approximately spherical. Furthermore, the vertical cross-sectional shape of the groove 201 can also be V-shaped, U-shaped, or “︺”-shaped. A V-shaped groove 201 can be understood as an inverted triangular groove; a U-shaped groove 201 can be understood as a rectangular groove; and a “︺”-shaped groove 201 can be understood as an inverted trapezoidal groove. It should be noted that the vertical cross-section of the groove 201 refers to the cross-section formed by vertically cutting the pad substrate 1, while the horizontal cross-section refers to the cross-section formed by horizontally cutting the pad substrate 1.

[0053] In some embodiments, the groove 201 is an arc-shaped groove. In this embodiment, the groove 201 is set as an arc-shaped groove to avoid stress concentration at the sharp corners of the inner wall of the groove 201, which would reduce the strength of the pad substrate 1.

[0054] In some embodiments, the thickness of the nickel plating layer 12 is 2-3 μm, and the thickness of the gold plating layer 13 is 0.1-0.25 μm. Setting the thicknesses of the nickel plating layer 12 and the gold plating layer 13 within these ranges ensures that the pad structure has good corrosion resistance. Simultaneously, when the pad structure is applied, for example, in a pressure sensor, it also ensures that the gold plating layer 13 has sufficient thickness for bonding with the bonding wire 6.

[0055] An embodiment of the present invention provides a method for preparing a pad structure, used to prepare the pad structure as described above, comprising:

[0056] Nickel plating is performed on the surface of substrate layer 11 to form nickel plating layer 12, and gold plating is performed on the surface of nickel plating layer 12 to form gold plating layer 13, thereby obtaining pad substrate 1;

[0057] The surface of the gold plating layer 13 away from the nickel plating layer 12 is divided into a bonding region 10 and a non-bonding region 20. The gold plating layer 13 or at least part of the nickel plating layer 12 is removed in the non-bonding region 20 by laser to form a groove 201, thereby obtaining a pad structure.

[0058] In this embodiment, the substrate layer 11 can be made of copper alloy. First, a nickel layer 12 and a gold layer are electroplated to obtain the pad substrate 1. Then, a laser removal process is used to remove the gold plating layer 13 from the surface of the pad substrate 1 to form a groove 201, resulting in a non-bonding area 20 (e.g., ...). Figure 4 As shown in the figure, the area where the gold plating layer 13 was not removed by laser is the bonding area 10. Figure 4In the diagram, the two thick arrows at the top indicate that the gold plating layer 13 on the surface of the pad substrate 1 is removed using a laser roughening process. It should be noted that because laser roughening in the non-bonding area 20 is performed through multi-point removal—that is, not completely removing gold plating from an entire area, but removing it at multiple points—a rough surface with alternating concave and convex surfaces is formed. Therefore, some areas in the non-bonding area 20 where the gold plating layer 13 was not removed by laser roughening also exist. However, these are areas between adjacent grooves 201, and these areas are not the bonding area 10 described in this embodiment. Figure 1 As shown, the central rectangular area on the surface of the pad substrate 1 is the bonding area 10, and the area outside the bonding area 10 is roughened by laser multi-point gold removal and becomes the non-bonding area 20. Figure 5 The image shows the surface of the pad structure plating. The rectangular area in the middle is the unroughened bonding area 10, and the area outside the bonding area 10 is the laser-roughened non-bonded area 20. It can be seen that the two areas are significantly different.

[0059] Please see Figure 6 As shown, this embodiment of the invention also provides a pressure sensor, including a substrate, a pressure chip 3, a pad structure as described above, and a protective adhesive 2. The pressure chip 3 is disposed on the substrate, the pad structure is disposed on the substrate and the pressure chip 3 respectively, and the protective adhesive 2 is disposed on the substrate and covers the surfaces of the pressure chip 3 and the pad structure.

[0060] like Figure 6 The diagram shows the internal structure of a pressure sensor. The upward arrows indicate that air, water, fuel vapor, particulate matter, etc., are dispersed on the surface of the pressure sensor. The pressure sensor includes a substrate, a pressure chip 3, pad structures, and protective adhesive 2. The pressure chip 3 is mounted on the substrate, for example, by adhesive. The substrate can be made of plastic. The pressure chip 3 senses changes in the pressure of the external medium and outputs a voltage signal. The surface of the pressure chip 3 has pad structures, and the substrate also has pad structures. These pad structures are used for soldering bonding wires 6. Protective adhesive 2 covers the surfaces of the pressure chip 3 and the pad structures. If bonding wires 6 are soldered to the pads, protective adhesive 2 also covers the surface of the bonding wires 6.

[0061] In this embodiment, the pressure sensor has pad structures with non-bonded areas 20 and bonded areas 10 on the substrate and pressure chip 3, respectively, and a protective adhesive 2 is applied to the surface of the pads. Since the non-bonded areas 20 have an uneven surface formed by laser roughening, increasing roughness, and the protective adhesive 2 is a gel-like substance with adhesiveness and flexibility, it can increase the bonding strength with the pad substrate 1 and reduce the risk of adhesive 2 peeling off. Simultaneously, the bonding areas 10 with a gold-plated layer 13 are retained on the pad substrate 1. The strong stability of the gold-plated layer 13 improves the corrosion resistance of the pad substrate 1, thereby enhancing the stability of the sensor.

[0062] In some of these implementations, such as Figure 6 , Figure 7 As shown, the pressure sensor also includes a bonding wire 6, which is used to connect the substrate and two pad structures on the pressure chip 3, and the bonding wire 6 is connected to the bonding area 10 of the pad structure.

[0063] In the structure of the pressure sensor, pads are set on the substrate and the pressure chip 3 respectively. For easy distinction, as shown... Figure 6 As shown, the pad structure set on the substrate is called terminal pad 7, and the pad structure set on the pressure chip 3 is called chip pad 4. The terminal pad 7 and the chip pad 4 are connected by bonding wire 6, thereby realizing the electrical interconnection between the substrate and the chip. Figure 7 In the diagram, “4 / 7” indicates that the pad can be either a terminal pad 7 or a chip pad 4. The two dashed lines point to an enlarged schematic diagram of the pad substrate 1, indicating that the pad substrate 1 is composed of a copper alloy substrate layer 11, a nickel plating layer 12, and a gold plating layer 13.

[0064] In a preferred embodiment, the bonding wire 6 is a gold wire. This embodiment uses gold wire instead of aluminum wire because, firstly, gold wire is softer and less prone to oxidation; secondly, since the bonding wire 6 is gold wire and is connected to the bonding area 10 of the pad structure, and the surface of the bonding area 10 of the pad structure is a gold-plated layer 13, the gold wire and the gold-plated layer 13 are welded together using the same material. During welding, the gold wire and the gold-plated layer 13 can be fused together without creating a joint surface, thereby ensuring high welding strength and bonding force between the bonding wire 6 and the pad structure.

[0065] This embodiment improves the mechanical properties and oxidation resistance of the bonding wire 6 by improving the material of the bonding wire 6. At the same time, the same material welding between the bonding wire 6 and the pad structure also improves the welding strength between the bonding wire 6 and the pad structure, reducing the risk of the bonding wire 6 peeling off from the pad.

[0066] In a preferred embodiment, the central area of ​​the surface of the pad substrate 1 is the bonding area 10, which is used for soldering with gold wires. Its surface is gold-plated to ensure high soldering strength. Furthermore, the bonding area 10 needs to completely cover the solder for gold wire soldering. Its shape is preferably rectangular, and its area accounts for approximately 40% of the total pad area, with a maximum not exceeding 50%, otherwise the adhesion to the protective rubber will be reduced. The area surrounding the pad substrate 1, i.e., outside the bonding area 10, is designed as a laser-roughened non-bonding area 20. A laser removal process is used to remove gold and roughen the surface of the area surrounding the pad. Preferably, a femtosecond removal process is used to remove the gold plating material from the surface of the area surrounding the pad at multiple points, forming multi-point distributed femtosecond pits. This exposes the nickel layer under the gold plating layer 13, allowing it to contact the rubber. Strong hydrogen bonds exist between the nickel and the rubber surface, enabling the nickel plating to bond firmly with the rubber. Even if moisture penetrates, the hydrogen bonds can still be maintained. Meanwhile, the multi-point femtosecond pits create an uneven surface on the pads, increasing their roughness. The nickel plating and the roughened surface together improve the adhesion between the protective rubber and the pad plating, thus solving the problem of protective rubber peeling. The femtosecond pulses are ultra-strong and ultra-short, ensuring smooth edges of the femtosecond pits, improving anti-coking properties, and allowing for precise control over the size and shape of the femtosecond pits. The diameter of the femtosecond pits is approximately 100 μm, and the depth is 1-1.5 μm.

[0067] In some embodiments, the protective adhesive 2 uses a silicone-crosslinked perfluoropolyether material instead of ordinary silicone rubber. The silicone-crosslinked perfluoropolyether material has higher chemical robustness and can effectively resist exhaust gas corrosion and humidity effects. This embodiment improves the protective rubber material's resistance to oil, water, and exhaust gas corrosion by modifying its properties.

[0068] In some embodiments, the pressure sensor further includes a waterproof and breathable membrane 5 covering the surface of the protective adhesive 2, the waterproof and breathable membrane 5 comprising expanded polytetrafluoroethylene microporous membrane.

[0069] Because automobile exhaust contains a large amount of corrosive substances such as nitrogen oxides, sulfides, and halogens, the protective adhesive 2 material, made of ordinary silicone rubber, is not oil-resistant and has weak corrosion resistance, making it unable to resist the corrosion of exhaust gases. Once corroded, the protective rubber cannot accurately transmit external pressure, leading to pressure signal drift and excessive accuracy. In this embodiment, a waterproof and breathable membrane 5 is also covered on the surface of the protective adhesive 2. The waterproof and breathable membrane 5 is an oleophobic expanded polytetrafluoroethylene microporous membrane with excellent chemical stability and corrosion resistance. It forms an integral part with the protective adhesive 2, both transmitting pressure and preventing the ingress of water, foreign matter, etc. from the external gas. Furthermore, because the protective adhesive 2 has strong adhesion, the waterproof and breathable membrane 5 can be directly bonded to its surface.

[0070] The waterproof and breathable membrane 5 is made by mixing a dispersion resin and an olefin material and then extruding it as a paste. The olefin material is volatile, and when it volatilizes, it creates micropores. Utilizing the plasticity of polytetrafluoroethylene (PTFE), the density or porosity of the microporous membrane is adjusted by longitudinal or biaxial stretching. Because the pore size is larger than the diameter of an air molecule but much smaller than the diameter of a water molecule, the microporous membrane allows gas to pass through while blocking water. Expanded PTFE has natural hydrophobic and oleophobic properties, preventing not only water penetration but also blocking low surface tension liquids such as oil, detergents, and alcohol. Water and low surface tension liquids do not penetrate; instead, they slide off to the outside of the sensor due to gravity. Therefore, the waterproof and breathable membrane 5, as the first point of contact with the measured medium, acts as the first barrier, filtering and blocking large water molecules, fuel particles, impurities, and other foreign matter, reducing the contamination and corrosion of the protective rubber, bonding wires 6, solder pads, and pressure chip 3 by exhaust gases.

[0071] Since particles and oil stains are also corrosive to the protective adhesive 2, the waterproof and breathable membrane 5 can prevent large particles or oil stains in the air from contacting the protective adhesive 2. Furthermore, high concentrations of hydrocarbons and water vapor in exhaust gases can cause the protective adhesive 2 to expand, increasing the internal pores and making it easier for impurities and corrosive substances to enter, further corroding it. When corrosive substances come into contact with the bottom of the protective adhesive 2, they can easily contact the pad structure and bonding wires 6, causing corrosion to them. Therefore, in this embodiment, by covering the surface of the protective adhesive 2 with a waterproof and breathable membrane 5, it serves two purposes: firstly, to waterproof the adhesive 2 and prevent its expansion from causing more corrosive substances to enter; and secondly, to remove oil stains and large particles that the protective adhesive 2 cannot withstand.

[0072] Therefore, the pressure sensor in this embodiment has two protective barriers. The first protective barrier is a waterproof and breathable membrane 5, which is in direct contact with the gas being measured. It allows the gas to pass through while preventing the entry of large water molecules and oily liquids. It can also block particulate matter in the exhaust gas, protecting internal components such as rubber, bonding wires 6, solder pads, and pressure chip 3 from contamination and corrosion by large molecular foreign matter. The protective adhesive 2 serves as the second barrier and is made of a silicon-crosslinked perfluoropolyether material with high heat resistance and chemical stability. It has high resistance to highly corrosive acids, alkalis, oxidants, etc., and can resist corrosive gases in the exhaust gas that are not filtered out by the waterproof and breathable membrane 5. Preferably, the protective rubber is 3-4 mm thick, the waterproof and breathable membrane 5 is about 0.1 mm thick, the porosity is 60%-70%, and the average pore size is 0.05-0.1 μm.

[0073] In this embodiment, by improving the materials of the bonding wire 6 and the protective rubber, adding a waterproof and breathable membrane 5, and proposing a femtosecond roughened pad plating structure, the pressure sensor can withstand pollutants such as water molecules, corrosive particles, and dust in the exhaust gas environment. This improves the corrosion resistance of the pressure sensor's protective rubber and bonding wire 6, while also enhancing the adhesion between the protective rubber and the pad plating surface. Ultimately, this solves problems such as corrosion of the protective rubber, peeling of the protective rubber from the pad, and breakage of the bonding wire 6. The pressure sensor of this embodiment has strong chemical corrosion resistance and anti-fouling properties. While enhancing the corrosion resistance and welding strength of the pad structure, it also improves the adhesion between the protective rubber and the pad plating surface, making the pressure sensor of this embodiment more widely applicable. It can be used in harsh environments with high oxidation, high corrosion, high hydrocarbons, and high humidity. Moreover, it has a simple structure, low cost, and is easy to manufacture, facilitating mass production.

[0074] This invention also provides a method for fabricating a pressure sensor, comprising:

[0075] Prepare the pad structure; integrally injection mold the plastic substrate and the pad structure; apply adhesive to the substrate and mount the pressure chip 3, preferably with an adhesive application amount of 40 mg; cure the adhesive, preferably at a temperature of 150℃ and a curing time of 1 h; perform gold wire bonding, preferably with a bonding time of 40 ms and a bonding frequency of 65 kHz; apply protective adhesive 2 to the surfaces of the pressure chip 3, the pad structure, and the bonding wires 6, preferably with an adhesive application amount of 30 mg; bond a waterproof and breathable membrane 5 to the surface of the protective adhesive 2; cure the protective adhesive 2, preferably at a curing temperature of 150℃ and a curing time of 1 h.

[0076] The preparation steps of the pad structure are as follows: the pad substrate is cut and bent to form a substrate layer 11; nickel is plated on the surface of the substrate layer 11 to form a nickel plating layer 12; gold is plated on the surface of the nickel plating layer 12 to form a gold plating layer 13; laser roughening is performed on part of the gold plating layer 13 to form a non-bonding area 20, and the rest is a bonding area 10, thereby obtaining the pad structure.

[0077] This invention also provides an exhaust gas recirculation system, including the pressure sensor described above. Exhaust gas recirculation introduces a portion of the vehicle's exhaust gas into the combustion chamber to reduce the peak combustion temperature and suppress NO. X The exhaust gas recirculation system includes an intake manifold, an exhaust manifold, and a gas intake manifold. Pressure sensors are typically installed in the intake system and are connected to the engine's ECU via communication lines to detect gas pressure and send signals.

[0078] This invention also provides a vehicle including the exhaust gas recirculation system described above.

[0079] Example of effect:

[0080] To verify the effect of laser roughening in this embodiment on enhancing the adhesion between the protective rubber and the solder pad surface, a set of tensile force comparison tests were conducted in this embodiment. For example... Figure 8 As shown, a pair of pads are bonded together with rubber to form a test group. The "4 / 7" marking in the figure indicates that the pad can be either a terminal pad 7 or a chip pad 4. The left and right arrows in the figure indicate the direction of tensile force, representing the tensile strength test performed on this test group. If the surface of the pad in contact with the rubber is a gold-plated layer 13, the test group is called a gold-plated terminal. If the surface of the pad in contact with the rubber is a surface with grooves 201 after laser gold removal roughening treatment, the test group is called a laser-roughened terminal.

[0081] During testing, four sets of gold-plated terminals (with gold plating layer 13 on the pad surface) and four sets of laser-roughened terminals (with laser gold removal roughening on the pad surface) were selected as test samples for a damp heat steady-state test, maintaining a temperature of 85℃ and a humidity of 85%RH for 50 hours. Tensile strength tests were performed on the samples at 0h, 5h, 20h, and 50h during the test.

[0082] Test results show that under dry conditions, the tensile strength of both laser-roughened and gold-plated samples is around 8N, with little difference between the two; under humid conditions, such as... Figure 9 As shown, the tensile strength of the laser-roughened sample remained around 8N, with no significant decrease. However, the tensile strength of the gold-plated sample dropped sharply to around 4N at the beginning of the test, and then gradually decreased over time. This indicates that a higher tensile strength signifies a stronger bond between the pad and the rubber. For the laser-roughened sample (i.e., the pads roughened by laser gold removal), after adhering to the rubber, it requires approximately 8N to break, and the difference in tensile strength between humid and dry environments is minimal, indicating a tight bond and strong adhesion between the rubber and the pad, with a very low risk of rubber peeling. For the gold-plated pads, after adhering to the rubber, separating them requires approximately 8N in a dry environment, but the tensile strength drops sharply in a humid environment, and continues to decrease slowly over time. This shows that under humid conditions, the bond between the rubber and the gold plating layer 13 is significantly reduced, making it easy for the rubber to peel off from the gold plating layer 13.

[0083] Furthermore, observation of the fracture surfaces of each sample revealed that the gold-plated pads fractured at the boundary between the rubber and the pad surface, resembling peeling. However, after laser roughening of the pad surface, the fracture occurred in the middle of the rubber, without any rubber peeling. This indicates that the bonding force between the pad and rubber after laser roughening was too strong; even when the sample was finally broken with a force of approximately 8N, the rubber itself was the one that broke. This demonstrates that in a humid environment, the fracture force between rubber and the laser-roughened surface is greater than that between the gold-plated surface. This further verifies that in this embodiment, after plating nickel and gold layers on the pad surface, laser roughening is performed to remove the gold layer 13, exposing the nickel layer bonded to the rubber, which improves the adhesion between the rubber and the pad surface.

[0084] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A pad structure, characterized in that, The device includes a pad substrate (1), which includes a substrate layer (11) and a nickel plating layer (12) and a gold plating layer (13) sequentially disposed on the substrate layer (11). The surface of the gold plating layer (13) away from the nickel plating layer (12) is divided into a bonding area (10) and a non-bonding area (20). The bonding area (10) is used to connect with a bonding wire (6), and the non-bonding area (20) is used to connect with a protective adhesive (2). The non-bonding area (20) forms a plurality of grooves (201). The distance from the surface of the gold plating layer (13) away from the nickel plating layer (12) to the bottom of the groove (201) is greater than or equal to the thickness of the gold plating layer (13) and less than or equal to the sum of the thicknesses of the gold plating layer (13) and the nickel plating layer (12).

2. The pad structure according to claim 1, characterized in that, The plurality of grooves (201) are arranged in an array on the surface of the gold plating layer (13) away from the nickel plating layer (12).

3. The pad structure according to claim 1, characterized in that, Along the direction from the gold plating layer (13) toward the nickel plating layer (12), the cross-sectional size of the groove (201) gradually decreases.

4. The pad structure according to claim 1, characterized in that, The groove (201) is an arc-shaped groove.

5. A pressure sensor, characterized in that, The device includes a substrate, a pressure chip (3), a pad structure as described in any one of claims 1-4, and a protective adhesive (2). The pressure chip (3) is disposed on the substrate, the pad structure is disposed on the substrate and the pressure chip (3), and the protective adhesive (2) is disposed on the substrate and covers the surfaces of the pressure chip (3) and the pad structure.

6. The pressure sensor according to claim 5, characterized in that, It also includes bonding wires (6), which are used to connect the pad structure on the substrate and the pad structure on the pressure chip (3), and the bonding wires (6) are connected to the bonding area (10) of the pad structure.

7. The pressure sensor according to claim 5, characterized in that, It also includes a waterproof and breathable membrane (5), which covers the surface of the protective adhesive (2), and the waterproof and breathable membrane (5) includes an expanded polytetrafluoroethylene microporous membrane.

8. A method for manufacturing a pressure sensor, characterized in that, For manufacturing a pressure sensor as described in any one of claims 5-7, comprising: Nickel plating is performed on the surface of the substrate layer (11) to form a nickel plating layer (12), and gold plating is performed on the surface of the nickel plating layer (12) to form a gold plating layer (13), thereby obtaining the pad substrate (1). The surface of the gold plating layer (13) away from the nickel plating layer (12) is divided into a bonding area (10) and a non-bonding area (20). The gold plating layer (13) or the gold plating layer (13) and at least part of the nickel plating layer (12) are removed in the non-bonding area (20) by laser to form a groove (201) to obtain a pad structure. The substrate and the pad structure are integrally formed, and the pressure chip (3) is integrally formed with the pad structure, and the pressure chip (3) is mounted on the substrate; The bonding wire (6) connects the pressure chip (3) and the pad structure on the substrate; Protective adhesive (2) is applied to the surfaces of the pressure chip (3), the pad structure and the bonding wire (6); A waterproof and breathable membrane (5) is bonded to the surface of the protective adhesive (2) to obtain a pressure sensor.

9. A waste gas recirculation system, characterized in that, Including the pressure sensor as described in any one of claims 5-7.

10. A vehicle, characterized in that, Including the exhaust gas recirculation system as described in claim 9.

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