Air flow rate detection device
Patent Information
- Application Number
- PCT/JP2025/012080
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025012080_01102026_PF_FP_ABST
Abstract
Description
Air flow rate detection device
[0001] The present invention relates to an air flow rate detection device.
[0002] In internal combustion engines, the mixing ratio of air and gasoline in the engine is important from the perspective of improving fuel efficiency, and the mechanism is such that the ECU controls the mixing ratio based on the intake air amount measured by a thermal air flow meter. Currently, studies are being conducted to improve the reliability and process capability of such air flow meters. For example, studies are being conducted on a resin coating method for connection terminals to improve the reliability of packaged components in air flow meters.
[0003] However, with the resin filled in current connection terminals, the resin does not flow around to the back surface of the connection terminals, resulting in the problem of unsealed areas.
[0004] Patent Document 1 below describes a technique for improving the efficiency of the resin sealing process, which addresses the efficiency degradation of the resin sealing process caused by uneven height of components. The technique allows adjusting the package height by forming a hole in a substrate to align the heights of the package and other components. The document describes the following technical feature: "At least one of a partition wall 238 partitioning a first region R2 including a first support 208 and a first connection wiring 272 and a second region R3 including a second support 206 and a second connection wiring 276, or a partition wall 237 partitioning the first region R2 and a third region R1 including a third connection wiring 277 is provided. The circuit board 207 is fixed to a housing by the partition walls 237 and 238, the first region R2, the second region R3 and the third region R1 are sealed with a sealing material 281, and the height of the sealing material is made different in at least one of between the first region R2 and the second region R3, or between the first region R2 and the third region R1."
[0005] Patent Document 2 below describes a method for preventing galvanic corrosion by resin sealing around the connection terminals, while suppressing an increase in the number of parts and an increase in the size of the device, and suppressing a decrease in the accuracy of airflow measurement due to external sound pressure. It includes a damping member 157 disposed between a thermal flow sensor 151 and a lead frame 154. The thermal flow sensor has a semiconductor substrate 151a, a thin film portion 151d formed on the surface side of the semiconductor substrate and exposed from the resin sealing portion 155, a flow detection portion 151b, and a recess 151c. The lead frame has a through hole 154a communicating with the opening of the recess and a ventilation groove 154b formed along the back surface and communicating with the through hole. The passage forming member 156 forms a ventilation passage 158 that connects the recess to the outside together with the through hole and the ventilation groove, and the portion that closes the through hole is exposed from the resin sealing portion. The technology is described as having a damping member and multiple communication holes 157a set to an opening ratio β such that the resistance coefficient K for the gas flowing between the ventilation passage and the recess is less than 2.76.
[0006] Japanese Patent Publication No. 2020-112433 Japanese Patent Publication No. 2023-165043
[0007] The technology described in Patent Document 1 provides an air flow rate measuring device that can mount electronic components and sensing components with connection terminals of different heights, and that can achieve both a component sealing function and a function of exposing the sensing part. Furthermore, the height is adjusted by providing a notch in the substrate to house the chip package.
[0008] The technology described in Patent Document 2 provides an airflow measuring device that suppresses an increase in the number of parts and the size of the device, and suppresses a decrease in the accuracy of airflow measurement due to external sound pressure. In addition, the connection terminals of the chip package are resin-sealed.
[0009] However, with both technologies, there is a concern that high-viscosity resins may not adequately seal the connection terminal due to insufficient resin flow to the back. Therefore, it is believed that there is room for improvement in the technology described in the document regarding resin sealing to the back of the connection terminal.
[0010] In view of the above circumstances, the object of the present invention is to provide an air flow detection device that blocks corrosive gases and moisture to prevent electrolytic corrosion of connection terminals.
[0011] A brief overview of some of the representative inventions disclosed herein is as follows: One of the ideas of the present invention is an airflow detection device comprising a housing having a sub-passage and a circuit chamber, a circuit board housed in the circuit chamber, and a chip package disposed on the circuit board, wherein the chip package has a package body with its tip portion disposed in the sub-passage and its base portion disposed in the circuit chamber, and a connection terminal protruding from the base portion of the package body and connected to the circuit board, and the circuit board has an opening formed therein that penetrates the circuit board and opens at a position opposite to the boundary portion between the tip portion and the base portion of the package body, and a sealing resin material is filled and disposed in the opening and the gap between the package body and the circuit board opposite the opening.
[0012] According to the airflow detection device of the present invention, since sealing resin material is filled in the opening and the gap between the package body and the circuit board facing the opening, communication between the sub-passage and the circuit chamber through the gap between the package body and the circuit board can be blocked. Therefore, it is possible to prevent corrosive gases and moisture from flowing from the sub-passage into the circuit chamber and coming into contact with the connection terminals.
[0013] Further features related to the present invention will become apparent from the description herein and the accompanying drawings. Problems, configurations, and effects not described above will be revealed by the following description of embodiments.
[0014] A schematic diagram of an internal combustion engine control system using an electronic control device according to the first embodiment. A front view of the air flow detection device according to the first embodiment. A right side view of the air flow detection device according to the first embodiment. A rear view of the air flow detection device according to the first embodiment with the cover removed. A front view of the circuit board of the air flow detection device according to the first embodiment. A cross-sectional diagram of the package of the air flow detection device according to the first embodiment, showing the cross-section VI-VI in Figure 5. A front view of a conventional circuit board. A diagram showing the circuit chamber sealing structure of a conventional circuit board. A diagram showing the problems of the conventional resin sealing structure of connection terminals, showing the cross-section VIIC-VIIC in Figure 7B. A diagram showing the problems of the conventional resin sealing structure of connection terminals, showing the cross-section VIID-VIID in Figure 7B. A rear view of the circuit board of the air flow detection device according to the first embodiment. A diagram showing the resin filling structure into the circuit board opening of the air flow detection device according to the first embodiment, showing the cross-section VIIIB-VIIIB in Figure 8A. An enlarged view of the main part of Figure 8A. A diagram showing the cross-section VIIIID-VIID in Figure 8C. Figure 13A shows the substrate mounting process of the air flow detection device according to the first embodiment. Figure 13A shows the definition of the filling resin width, which is an indicator of the communication prevention effect. Figure 14 shows the resin viscosity sensitivity of the filling resin width. Figure 15 shows an example of the circuit board opening of the air flow detection device according to the second embodiment. Figure 16 shows an example of the circuit board opening of the air flow detection device according to the second embodiment. Figure 11A shows the cross section XIC-XIC of the resin filling structure. Figure 12A shows the cross section XIIB-XIIB of the resin filling structure. Figure 13A shows an example of the circuit board opening of the air flow detection device according to the third embodiment.
[0015] The embodiments of the present invention will be described in detail below with reference to the drawings. In all drawings used to illustrate the embodiments, the same reference numerals will be used for identical components, and repeated descriptions will be omitted. The present invention is not to be construed as being limited to the embodiments described below. It will be easily understood by those skilled in the art that the specific configuration can be modified without departing from the idea or spirit of the present invention.
[0016] In this specification, the designations "First," "Second," "Third," etc., are used to identify components and do not necessarily limit their number or order. Furthermore, the numbers used to identify components are used context by context, and a number used in one context does not necessarily indicate the same component in another context. Moreover, this does not prevent a component identified by one number from also performing the function of a component identified by another number.
[0017] The positions, sizes, shapes, and ranges of each component shown in drawings, etc., may not represent the actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings, etc. In this specification, components expressed in the singular form are to include plural forms unless otherwise clearly indicated in the context.
[0018] In the following embodiments, the example is given where the circuit board of the electronic control device is a sensor board, but the configuration is not limited to this, and other boards may be used. The electronic control device of this embodiment is shown as being used in a thermal air flow meter 20 for automobiles, and can be particularly effective in operating environments with harsh temperature conditions, such as automobiles.
[0019] <First Embodiment> <Internal Combustion Engine Control System Configuration> Figure 1 is a schematic diagram of an internal combustion engine control system using an electronic control device according to the first embodiment. The internal combustion engine control system 1 is a control system for an internal combustion engine in which air, which is the gas to be measured 2, is drawn in from an air cleaner 21, based on the operation of an internal combustion engine 10 which is equipped with an engine cylinder 11 and an engine piston 12.
[0020] The gas to be measured 2, which is drawn in from the air cleaner 21, is guided to the combustion chamber 11a of the engine cylinder 11 via the intake body 22, the throttle body 23, and the intake manifold 24.
[0021] The gas to be measured 2, which is introduced into the combustion chamber 11a, has its physical quantity detected by the thermal air flow meter 20 in the main flow path 22a. Based on this physical quantity, it is mixed with the fuel supplied from the fuel injection valve 14, and the resulting mixture is introduced into the combustion chamber 11a. The thermal air flow meter 20 in this embodiment corresponds to the air flow detection device in the claims.
[0022] The fuel-air mixture introduced into the combustion chamber 11a is ignited by the spark plug 13, causing it to burn explosively and generate mechanical energy. The resulting gas is then guided from the exhaust valve 16 to the exhaust pipe 16a and discharged outside the vehicle as exhaust gas 3.
[0023] The flow rate of the measured gas 2 introduced into the combustion chamber 11a is controlled by a throttle valve 25 whose opening degree changes based on the operation of the accelerator pedal. Furthermore, the amount of fuel supplied is controlled based on the flow rate of the measured gas 2 introduced into the combustion chamber 11a. Therefore, the driver can change the opening degree of the throttle valve 25 by operating the accelerator pedal, thereby controlling the flow rate of the measured gas 2 introduced into the combustion chamber 11a and changing the mechanical energy generated by the internal combustion engine.
[0024] The thermal air flow meter 20 is a sensor device that detects the airflow rate of an internal combustion engine. The thermal air flow meter 20 detects physical quantities such as flow rate, temperature, humidity, and pressure of the gas to be measured 2, which is taken in from the air cleaner 21 and flows through the main flow path 22a (in this embodiment, the flow path within the intake body 22), and outputs these physical quantities as electrical signals to the control device 4.
[0025] Furthermore, the throttle angle sensor 26 is a sensor that detects the opening degree of the throttle valve 25 and inputs it as an electrical signal to the control device 4. In addition, the rotation angle sensor 17 is a sensor that inputs detected values as electrical signals to the control device 4 in order to detect the position and state of the engine piston 12, intake valve 15, and exhaust valve 16 of the internal combustion engine, as well as the rotational speed of the internal combustion engine. Furthermore, the oxygen sensor 28 is a sensor that inputs detected values as electrical signals to the control device 4 in order to detect the state of the fuel-air mixture ratio from the state of the exhaust gas 3.
[0026] The control device 4 is a device that calculates the fuel injection amount and ignition timing based on the detection values of the thermal air flow meter 20, throttle angle sensor 26, rotation angle sensor 17, and oxygen sensor 28. Based on the calculation results of the control device 4, the amount of fuel supplied from the fuel injection valve 14 and the ignition timing of ignition by the spark plug 13 are controlled. Furthermore, in order to control the rotational speed of the internal combustion engine in idle operation, the control device 4 controls the amount of air bypassing the throttle valve 25 by the idle air control valve 27 in the idle operation state of the internal combustion engine. Therefore, the fuel supply amount and ignition timing, which are the main control quantities of the internal combustion engine, are calculated based on the detection value of the thermal air flow meter 20.
[0027] <Thermal Air Flow Meter 20> Figure 2 is a front view of the thermal air flow meter 20 according to this embodiment, Figure 3 is a right side view of the thermal air flow meter 20 according to this embodiment, and Figure 4 is a rear view of the thermal air flow meter according to this embodiment with the cover 120 removed. Hereinafter, the gas to be measured 2 flows through the main flow path 22a in one direction of the arrow, and the upstream and downstream sides will be described with reference to the direction of the arrow.
[0028] The thermal air flow meter 20 has a flange portion 111 which is a part for fixing to the intake body 22, a connector portion 112 which is a part for electrically connecting to external equipment, and a measuring portion 113 which is a part for measuring the physical quantity of the gas to be measured 2.
[0029] The flange portion 111 is, for example, a plate-like portion that is roughly rectangular in shape when viewed from above, made of a predetermined plate thickness, and has a pair of fixing holes at the diagonal corners. A through hole is provided in the center of the fixing holes, and the thermal air flow meter 20 is fixed to the intake body 22 by a screw inserted into the through hole.
[0030] As shown in Figure 3, the connector section 112 is provided on the upper part of the flange section 111 and includes, for example, a plurality (four in this embodiment) of external input / output terminals 147 and a correction terminal 148. The plurality of external input / output terminals 147 include terminals for outputting physical quantities such as flow rate and temperature, which are measurement results of the thermal air flow meter 20, and power supply terminals for supplying DC power for the thermal air flow meter 20 to operate. The correction terminal 148 is a terminal used to store correction values in the thermal air flow meter 20.
[0031] As shown in Figure 4, the housing 100 is provided with a sub-channel groove 150 that connects the sub-channel inlet 131, the first outlet 132, and the second outlet 133, and a circuit chamber 101. The circuit chamber 101 also houses a circuit board 300 that is fixed in the recess 135.
[0032] The sub-channel groove 150 is a groove for allowing the gas to be measured 2 to pass through the measurement unit 113 in order to detect its physical quantity. The sub-channel groove 150 comprises a first sub-channel groove 151 that connects the sub-channel inlet 131 and the first outlet 132, and a second sub-channel groove 152 that branches off from the first sub-channel groove 151, bypasses upward, then bends downward to connect with the second outlet 133.
[0033] <Circuit Board Mounting> Figure 5 is a front view of the circuit board of the air flow detection device according to this embodiment. The thermal air flow meter 20 comprises a circuit board 300 on which conductors to which electronic components are connected are arranged, and a solder resist 3000 formed on the surface of the circuit board 300 to protect the wiring layer. Electronic components mounted on the circuit board 300 include, for example, a flow sensor 140, a temperature sensor 160, a pressure sensor 170, and a humidity sensor 180. The flow sensor 140 has a chip package equipped with a sensor device that detects the air flow rate of an internal combustion engine.
[0034] The temperature sensor 160 is, for example, a chip-type temperature sensor mounted on the circuit board 300. The temperature sensor 160 is positioned at the tip of an extension 301 of the circuit board 300 that extends toward the tip of the measurement unit 113 in the protruding direction of the measurement unit 113, as shown in Figure 5. The temperature sensor 160 is positioned in the temperature measurement passage 190 of the measurement unit 113 shown in Figures 2 and 4, and measures the temperature of the gas to be measured 2 that is taken into the temperature measurement passage 190 from the main passage 22.
[0035] The pressure sensor 170 is mounted on the surface of the circuit board 300 and positioned within the circuit chamber 101, as shown in Figures 4 and 5. The circuit chamber 101 communicates with the folded portion of the second sub-passage 134e, which curves in a U-shape near the flange portion 111. This makes it possible to measure the pressure of the gas to be measured 2 taken into the sub-passage 134 using the pressure sensor 170 located in the circuit chamber 101.
[0036] The humidity sensor 180 is mounted on the surface of the circuit board 300, for example, as shown in Figure 4, and is located in a partitioned area on the tip side of the measurement unit 113, closer to the circuit chamber 101. This partitioned area is connected, for example, to the second sub-passage 134e of the sub-passage 134. As a result, the humidity sensor 180 detects the humidity of the gas to be measured 2 taken into the sub-passage 134.
[0037] <Chip Package> Figure 6 is a cross-sectional view of the package configuration of the air flow detection device according to the first embodiment, and shows the cross section VI-VI in Figure 5. Figure 6 shows the cross-sectional configuration of the flow sensor (chip package) 140 mounted on the substrate.
[0038] The chip package 140 has a package body 1401 in which the tip portion 1013 is positioned in the second sub-passage 134e and the base portion 1014 is positioned in the circuit chamber 101, and connection terminals 1012 that protrude from the base portion 1014 of the package body 1401 and are connected to the circuit board 300. As shown in Figure 5, the tip portion 1013 of the package body 1401 is wider than the base portion 1014, and multiple connection terminals 1012 are provided so as to protrude in directions away from each other from both side edges of the base portion 1014 of the package body 1401.
[0039] As shown in Figure 6, the chip package 140 is mounted upside down on the circuit board 300 so that the sensor device 1003 faces the circuit board 300, and a sub-passage 1002 is formed between the circuit board 300 and the diaphragm portion 1001. The sub-passage 1002 is in communication with the diaphragm portion 1001 of the sensor device 1003, and the velocity of the air flowing through this sub-passage 1002 can be detected by the diaphragm portion 1001 of the sensor device 1003.
[0040] The chip package 140 consists of a sensor device 1003 for detecting airflow, an LSI 1004 for performing correction processing of the sensor signal, a lead frame 1005 for sending the sensor signal from the LSI 1004 outside the package 140, a plate 1007 having ventilation holes 1006 to relieve stress caused by the difference in thermal expansion between the sensor device 1004 and the lead frame 1005, and a mold resin 1008 for covering the components.
[0041] Furthermore, an opening 1010 is provided to prevent the problem of electrolytic corrosion that occurs when the sub-passage 1002 and the connection terminal 1012 of the chip package 140 communicate through the gap 1009 formed between the circuit board 300 and the lower surface of the package body 1401 after the chip package 140 is mounted, and the opening 1010 is filled with sealing resin material 1011c.
[0042] <Resin sealing structure for connection terminal portion> Before describing the configuration of the present embodiment, first, the necessity of resin sealing for the connection terminal portion and conventional problems will be described. FIGS. 7A to 7D are diagrams showing a connection terminal sealing structure and a circuit chamber sealing structure of a conventional air flow rate detection device. FIG. 7A is a front view of a conventional circuit board, FIG. 7B is a diagram showing a circuit chamber sealing structure of a conventional circuit board, and FIGS. 7C and 7D are diagrams showing problems of a conventional resin sealing structure for connection terminals. FIG. 7C is a view showing a section VIIC-VIIC of FIG. 7B, and FIG. 7D is a view showing a section VIID-VIID of FIG. 7B.
[0043] Generally, the measured gas 2 guided to the combustion chamber 11a shown in FIG. 1 contains corrosive gas and moisture. Therefore, as shown in FIG. 7B, it is necessary to seal the periphery of the connection terminal 1012 with a sealing resin material 1011b to prevent electrolytic corrosion of the connection terminal 1012 and short circuit between terminals. In parallel with the prevention of such electrolytic corrosion of the connection terminals 1012 / short circuit between terminals, it is necessary to adopt a sealed structure to prevent communication between the circuit chamber 101 and the auxiliary passage 1002 (the gas 2 to be measured). As shown in FIG. 7D, the conventional method includes a method of covering the side surface and upper surface of the package body 1401 of the chip package 140 along the auxiliary passage 1002 with a sealing resin material 1011a, and the gap 1009 between the surface of the circuit board 300 and the lower surface of the package body 1401 is, as shown in FIGS. 7B and 7C, formed by a combination of a method of covering the base end portion of the package body with the sealing resin material 1011b so as to surround it in a U-shape, thereby constituting the sealing structure of the circuit chamber 101.
[0044] However, as shown in FIG. 7A, in the chip package 140 having a plurality of connection terminals 1012, even if resin is applied from above the terminals with a nozzle, the space between the terminals is narrow. Therefore, when the viscosity of the resin is high, the resin does not spread well on the back surfaces of the terminals, and an ideal sealed state as shown in FIG. 7C cannot be achieved, resulting in a problem that the back surfaces of the terminals cannot be sealed. If the back surfaces of the terminals cannot be sealed, the connection terminals 1012 may be exposed to corrosive gas and moisture that have flowed into the circuit chamber from the auxiliary passage 1002 through the gap 1009.
[0045] Therefore, in the present embodiment, instead of a method of directly resin-sealing the connection terminals, a method of preventing corrosive gas or the like from wrapping around to the connection terminals so as to indirectly obtain a sealing effect is proposed.
[0046] (Structure of the Invention: Slit Substrate, Resin Filled Cross-section) FIGS. 8A to 8D are diagrams showing a package cross-sectional configuration of an air flow rate detection device according to a first embodiment. FIG. 8A is a rear view of a circuit board of the air flow rate detection device according to the first embodiment, FIG. 8B is a diagram showing a resin filling structure into a circuit board opening of the air flow rate detection device according to the first embodiment, showing the VIIIB-VIIIB cross-section of FIG. 8A, FIG. 8C is an enlarged view of a main part of FIG. 8A, and FIG. 8D is a diagram showing the VIIID-VIIID cross-section of FIG. 8C.
[0047] A mounting structure of a chip package 140 on a circuit board 300 includes the chip package 140, the circuit board 300, an opening 1010 of the circuit board 300 (width: 1 mm, length: 8.3 mm), a secondary passage 1002 formed by the circuit board 300 and a sensor device 1003 in the chip package 140, a gap 1009 formed by the circuit board 300 and the lower surface of a package main body 1401 (height: about 0.1 mm), and a sealing resin material 1011c filled into the opening 1010 of the circuit board 300. The opening 1010 is arranged between the secondary passage 1002 (tip end 1013) of the chip package 140 and the connection terminal 1012 (base end 1014).
[0048] Further, FIGS. 8C and 8D show a sealing structure for preventing communication between the secondary passage 1002 and the circuit chamber 101. In the present embodiment, the method of covering the side surface and top surface of the package cross-section along the passage with the sealing resin material 1011a is adopted in the same manner as in the conventional art, and the sealing method on the gap 1009 side of the lower surface of the package main body 1401 is modified.
[0049] Specifically, an opening 1010 is provided in the circuit board 300, and the lower surface of the package body 1401 is covered with sealing resin material 1011a and 1011c, which fills the opening 1010, thereby creating a sealed structure for the circuit chamber 101 that allows the package cross-section to be covered without any gaps by sealing resin material 1011a and 1011c. In this embodiment, sealing resin material 1011b, which surrounds the base end of the package body in a U-shape, is combined with sealing resin materials 1011a and 1011c.
[0050] The circuit board 300 has an opening 1010 that penetrates the circuit board 300 and opens at a position opposite to the boundary between the tip portion 1013 and the base portion 1014 of the package body 1401. The opening 1010 and the gap 1009 between the package body 1404 and the circuit board 300 opposite the opening 1010 are filled with a sealing resin material 1011c.
[0051] The opening 1010 is positioned along the boundary between the tip 1013 and base 1014 of the package body 1401, and as shown in Figure 8D, it has a length that extends laterally beyond the base 1014 of the package body 1401. The opening 1010 is formed by a slit hole that extends along the boundary. The sealing resin material 1011c is filled through the opening 1010 and, in cooperation with the sealing resin material 1011a, surrounds the package body 1401 circumferentially along the boundary. This configuration makes it possible to block communication between the sub-passage 1002 and the circuit chamber via the conventional gap 1009. Therefore, it is possible to prevent corrosive gases and moisture from flowing from the sub-passage 1002 into the circuit chamber 101 and coming into contact with the connection terminal 1012.
[0052] Figure 9 shows the mounting process for the circuit board 300 in this embodiment. First, solder paste is printed on one side (for example, side B) of the circuit board 300, then components including the chip package 140 are mounted, and the components are soldered together by reflow soldering. After that, the same process is performed on the other side of the circuit board 300 (S101: PWB_ASSY process). Through this process, components are mounted on both the front (side A) and back (side B) of the circuit board 300.
[0053] Next, sealing resin material 1011 is filled into the opening 1010 on the back surface of the circuit board 300 (the side without the chip package 140) so as to cover the entire opening 1010 (S102: resin filling step). As a result, the sealing resin material 1011c is filled into the opening 1010 and the gap 1009 opposite the opening 1010. Then, the circuit board 300 with the sealing resin material 1011c filled into the opening 1010 is placed in a curing oven and the resin is cured by maintaining a high temperature (S103: resin curing step). Finally, a visual inspection is performed to determine whether the cured sealing resin material 1011 satisfies the predetermined specifications (S104: inspection step).
[0054] As described above, after mounting components onto the circuit board, the sealing resin material 1011c is applied to the opening 1010 of the circuit board 300 with the chip package 140 facing downwards and the circuit board 300 facing upwards, so that the sealing resin material 1011c is tightly packed against the lower surface of the package body 1401 visible through the opening 1010. This resin filling divides the gap 1009 between the lower surface of the package body 1401 and the circuit board 300 near the opening 1010 of the circuit board 300 into the sub-passage 1002 side (tip end 1013 side) and the connection terminal 1012 side (base end 1014 side), thus preventing communication between the sub-passage 1002 and the connection terminal 1012 of the chip package 140.
[0055] Here, we confirm the effect of preventing communication between the sub-passage 1002 and the chip package connection terminal 1012 by filling the opening 1010 of the circuit board with sealing resin material 1011. Figures 10A and 10B show the effect of preventing communication between the sub-passage of the air flow detection device according to the first embodiment and the gap on the bottom surface of the package, and are diagrams showing the effect of preventing communication between the sub-passage 1002 and the chip package connection terminal 1012. Figure 10A is a diagram showing the definition of the filling resin width, which is an indicator of the communication prevention effect, and Figure 10B is a diagram showing the resin viscosity sensitivity of the filling resin width.
[0056] In this embodiment, the resin-filled structure is divided by a sealing resin material 1011c near the opening 1010 of the circuit board 300, more specifically, at a position opposite to the boundary between the tip 1013 and base 1014 of the package body 1401, in the gap 1009 between the lower surface of the package body 1401 and the circuit board 300. The sealing resin material 1011c applied from the opening 1010 spreads from the opening 1010 into the gap 1009 formed between the lower surface of the package body 1401 and the circuit board 300, forming a resin spread 1011d on the tip 1013 side and a resin spread 1011e on the base 1014 side of the package body 1401. The resin spread width (filling resin width) W between these resin spreads 1011d and 1011e was evaluated as an indicator of the communication prevention effect.
[0057] Figure 10B shows the results of measuring the minimum value of the filled resin width W after peeling off the chip package 140 following the completion of the resin filling process S102. The result shows that the lower the resin viscosity, the wider the filled resin width W becomes, and the filled resin width W is not interrupted at the bottom surface of the package body 1401, indicating that the package tip end 1013 side and the package base end end 1014 side can be separated by the sealing resin material 1011c at least by the opening width (1.0 mm).
[0058] In other words, by positioning the opening 1010 (width: 1 mm, length: 8.3 mm) opposite the boundary between the tip 1013 and base 1014 of the package body 1401, and filling the gap 1009 (height: approximately 0.1 mm) formed by the circuit board 300 and the bottom surface of the package body 1401 with sealing resin material 1011 from the opening 1010, the gap 1009 between the bottom surface of the package body 1401 and the circuit board 300 can be divided by the sealing resin material 1011 into the sub-passage (tip 1013) side and the connection terminal (base 1014) side near the opening 1010 of the circuit board 300, thereby preventing galvanic corrosion of the connection terminal due to corrosive gases, etc.
[0059] <Effects> As described above, the circuit board opening (width: 1 mm, length: 8.3 mm) is positioned opposite to the boundary between the tip 1013 and base 1014 of the package body 1401, and the sealing resin material 1011c is filled into the gap 1009 (height: approximately 0.1 mm) between the circuit board 300 and the bottom surface of the package body 1401 from the opening 1010. This configuration allows the gap 1009 between the bottom surface of the package body 1401 and the circuit board to be divided by the sealing resin material 1011c near the opening 1010 of the circuit board 400 on the side of the sub-passage (tip) and the side of the connection terminal (base), thereby preventing galvanic corrosion of the connection terminal due to corrosive gases, etc.
[0060] <Second Embodiment> (Opening Shape Variation 1) The second embodiment is described below. This embodiment describes an air flow detection device in which the circuit board opening shape of the first embodiment has been changed. Furthermore, since it is assumed to be the same internal combustion engine control system configuration as the first embodiment, its explanation will be omitted.
[0061] <Circuit board opening shape> Figures 11A and 11B show an example of the shape of the opening 2010 of the circuit board 300 of the air flow detection device according to the second embodiment, and Figure 11C shows the cross section XIC-XIC of Figure 11A showing the resin-filled structure. The same reference numerals are used for components similar to those in the first embodiment, and their detailed explanation is omitted.
[0062] In this embodiment, the opening 2010 of the circuit board 300 is either the two slit shapes (width: 1.0 mm, length: 4.0 mm) shown in Figure 11A, or the seven circular shapes (diameter: 1.0 mm) shown in Figure 11B, and is positioned opposite to the boundary between the tip portion 1013 and the base portion 1014 of the package body 1401, similar to the first embodiment.
[0063] The opening 2010a is formed by at least one slit hole extending along the boundary portion, and in the example shown in Figure 11A, two slit holes are arranged in a row. The opening 2010b is composed of multiple circular holes, and in the example shown in Figure 11B, multiple circular holes are arranged in a row along the boundary portion.
[0064] Furthermore, similar to the first embodiment, after mounting components on the circuit board 300, the chip package 140 is placed downwards and the circuit board 300 is placed upwards, and the sealing resin material 1011c is filled into the opening 2010 of the circuit board 300, continuing until the lower surface of the package body 1401 visible from the opening 2010 is in close contact with the sealing resin material 1011c. This resin filling causes the gap 1009 between the lower surface of the package body 1401 and the circuit board 300 to be divided near the opening 2010 of the circuit board 300 into a sub-passage (tip 1013) side and a connection terminal (base 1014) side, as shown in Figure 11C, thus preventing communication between the previously communicating sub-passage 1002 and the connection terminal 1012 of the chip package 140.
[0065] <Effects> As described above, even if the opening shape is made into multiple slit shapes (width: 1 mm, length: 4.0 mm) or multiple circular shapes (diameter: 1.0 mm), by positioning the opening 2010 at a position opposite to the boundary between the tip 1013 and base 1014 of the package body 1401, and filling the gap 1009 (height: approximately 0.1 mm) formed by the circuit board 300 and the bottom surface of the package body 1401 with sealing resin material 1011c from the opening 2010, the gap 1009 between the bottom surface of the package body 1401 and the circuit board 300 can be divided by the sealing resin material 1011c on the side of the sub-passage 1002 and the side of the connection terminal 1012 near the opening 4010 of the circuit board 300, which has the effect of preventing galvanic corrosion of the connection terminal due to corrosive gases, etc.
[0066] <Third Embodiment> (Opening Shape Variation 2) The third embodiment is described below. This embodiment describes an air flow detection device in which the circuit board opening shape of the first embodiment has been changed. Furthermore, since it is assumed to be the same internal combustion engine control system configuration as the first embodiment, its explanation will be omitted.
[0067] <Circuit board opening shape> Figure 12A shows an example of a circuit board opening of the air flow detection device according to the third embodiment, and Figure 12B shows a cross section XIIB-XIIB of Figure 12A showing the resin-filled structure. Components similar to those in the first embodiment are denoted by the same reference numerals, and their detailed explanation is omitted.
[0068] The opening 3010 of the circuit board 300 in this embodiment is a circular hole having a single circular shape (diameter: 1.0 mm) as shown in Figure 12A, and, similar to the first embodiment, is positioned opposite to the boundary portion between the tip portion 1013 and the base portion 1014 of the package body 1401.
[0069] Furthermore, similar to the first embodiment, after mounting components on the circuit board 300, the chip package 140 is placed downwards and the circuit board 300 is placed upwards, and the sealing resin material 1011c is filled into the opening 3010 of the circuit board 300 until the lower surface of the package body 1401 visible through the opening 3010 is in close contact with the sealing resin material 1011c.
[0070] By adjusting the filling amount, the wet material spreads through the gap 1009 between the bottom surface of the package body 1401 and the package width direction by capillary action, spreading along the boundary between the tip 1013 and the base 1014 of the package body 1401, extending to a position laterally than the base 1014 of the package body 1401, and filling the entire width of the package.
[0071] As a result of this resin filling, as shown in Figure 12B, the gap 1009 between the lower surface of the package body 1401 and the circuit board 300 is divided near the opening 3010 of the circuit board 300 into a sub-passage (tip 1013) side and a connection terminal (base 1014) side, thereby preventing communication between the previously connected sub-passage 1002 and the connection terminal 1012 of the chip package 140.
[0072] <Effects> As described above, the shape of the opening 3010 is a circular hole having a single circular shape (diameter: 1.0 mm), and the opening 3010 is positioned opposite the boundary between the tip portion 1013 and the base portion 1014 of the package body 1401. By filling the gap (height: approximately 0.1 mm) formed by the circuit board 300 and the lower surface of the package body 1401 with resin from the opening 3010, the gap portion 1009 between the lower surface of the package body 1401 and the circuit board 300 can be divided by the sealing resin material 1011c on the side of the sub-passage 1002 and the side of the connection terminal 1012 near the opening 3010 of the circuit board 300, which has the effect of preventing galvanic corrosion of the connection terminal 1012 due to corrosive gases, etc.
[0073] <Fourth Embodiment> The fourth embodiment is described below. This embodiment describes an air flow detection device in which the resist configuration of the circuit board of the first embodiment has been changed. Furthermore, since it is assumed to have the same internal combustion engine control system configuration as the first embodiment, its explanation will be omitted.
[0074] <Circuit Board Resist Modification Structure> Figure 13A shows the resin filling structure into the circuit board opening of the air flow detection device according to the fourth embodiment, and Figure 13B is an enlarged view of the area around the resin filling section shown in Figure 13A. Figures 14A to 14C show the effect of preventing resin flow into the sub-passage of the air flow detection device according to the fourth embodiment. Figure 14A shows the solder resist coating area and the exposed area of the substrate surface on the circuit board, Figure 14B shows the filling resin width, which is an index for measuring the resin leakage prevention effect, and Figure 14C shows the resin dam pattern sensitivity of the resin spread. Components similar to those in the first embodiment are denoted by the same reference numerals, and their detailed explanation is omitted.
[0075] A distinctive feature of this embodiment is that, as shown in Figures 13B and 14A, an exposed area 4016 not covered by the solder resist 3000 is provided on the surface of the circuit board 300 and around the opening 4010, and the sealing resin material 1011c is accumulated in this exposed area 4016, thereby controlling the range over which the sealing resin material 1011c flows out, and in particular preventing it from flowing into the sub-passage 1002, thereby enabling stabilization of the flow characteristics.
[0076] Since the exposed area 4016 on the surface of the circuit board 300, where the opening 4010 is provided, is not covered with solder resist 3000, a resin dam portion 4017 is formed that can hold resin equivalent to the thickness of the resist, thereby preventing inflow into the sub-passage 1002 when filling the sealing resin material 1011c from the opening 4010.
[0077] The mounting structure of the chip package 140 on the circuit board 300 in this embodiment consists of the chip package 140, the circuit board 300, an opening 4010 (width: 1 mm, length: 8.3 mm) in the circuit board 300, a sub-passage 1002 formed by the circuit board 300 and the sensor device 1003 inside the chip package 140, a gap 1009 (height: approximately 0.1 mm) formed by the circuit board 300 and the lower surface of the package body 1401, and a sealing resin material 1011c that fills the opening 4010 of the circuit board 300.
[0078] The circuit board 300 has a slit-shaped opening 4010 positioned opposite the boundary between the tip 1013 and base 1014 of the package body 1401. The gap 1009 between the bottom surface of the package body 1401 and the circuit board 300 is divided near the opening 4010 of the circuit board 300 into a side passage (tip 1013) and a connection terminal (base 1014) by filling the opening 4010 with sealing resin material 1011c.
[0079] As shown in Figure 13B, the circuit board 300 has a covered area 4015 on its surface that is covered with solder resist and an exposed area 4016 that is not covered with solder resist. The exposed area 4016 is provided at a position opposite to the boundary between the tip 1013 and the base 1014 of the package body 1401. The exposed area 4016 only needs to be provided on the surface of the circuit board 300 on the side of the sub-passage leading from the opening 4010 to the tip 1013 of the package body 1401, but in this embodiment, the exposed area 4016 is also provided at a peripheral position including the opening 4010, that is, on the surface on the circuit chamber side leading from the opening 4010 towards the base 1014 of the package body 1401.
[0080] The resin dam portion 4017 is constructed by providing an exposed area 4016 in the gap portion 1009 and in the portion between the lower surface of the package body 1401 on the sub-passage 1002 side and the circuit board 300. In this embodiment, the resin dam portion 4017 is constructed by shortening the solder resist covering area 4015, which is located in the gap portion 1009 between the lower surface of the package body 1401 on the sub-passage (tip portion 1013) side and the circuit board 300, toward the sub-passage 1002 side (L = 1.5 mm), thereby providing an exposed area 4016 that is not covered by the solder resist 3000, as shown in Figure 14A. In other words, the resin dam portion 4017 is constructed by providing the exposed area 4016 on the surface of the circuit board 300 on the sub-passage 1002 side, extending from the opening 4010 toward the tip portion of the package body 1401.
[0081] By providing such a resin dam section 4017, it is possible to store a volume of sealing resin material 1011c equivalent to the thickness of the solder resist 3000, thereby suppressing the spreading of the resin when the sealing resin material 1011c is filled into the opening 4010 and preventing resin leakage into the sub-passage 1002.
[0082] Here, we confirm the effect of the resin dam section 4017 in preventing resin leakage by preventing the sealing resin material 1011c from flowing through the gap 1009 between the lower surface of the package body 1401 on the side of the sub-passage 1002 and the circuit board 300 and leaking into the sub-passage 1002.
[0083] In this embodiment, the resin-filled structure is such that the gap 1009 between the lower surface of the package body 1401 and the circuit board 300 is divided near the opening 4010 of the circuit board 300 by the sealing resin material 1011c into a sub-passage side (tip 1013) and a connection terminal side (base 1014). The sealing resin material 1011c filled from the opening 4010 of the circuit board 300 spreads from the opening 4010 into the gap 1009 formed between the lower surface of the package body 1401 and the circuit board 300. The sensitivity of this wetting spread resin dam pattern was evaluated using the resin spread width of the sealing resin material 1011c as an indicator of the resin leakage prevention effect.
[0084] Figure 14C shows the results of measuring the resin spread width of the sealing resin material 1011c after peeling off the chip package 140 following the completion of the resin filling process. The results are summarized for a low viscosity (20 Pa·s) sealing resin material that exhibits a relatively large degree of resin spread. When the resist-free length (width at the leading edge of the exposed area) L is short, the resin spread width is 3.5 mm or more, which leads to resin leakage into the sub-passage. It can be seen that resin spread can be suppressed by setting the resist-free length L to be longer (increasing the resin dam volume). Furthermore, it can be seen that the resist-free length that can suppress resin flow is 1.1 mm or more.
[0085] In other words, by positioning the opening 4010 (width: 1 mm, length: 8.3 mm) between the sub-passage (tip portion 1013) and the connection terminal end (base portion 1014) of the chip package 140, and filling the gap 1009 (height: approximately 0.1 mm) formed by the circuit board 300 and the lower surface of the package body 1401 with sealing resin material 1011c from the opening 4010, the gap 1009 between the lower surface of the package body 1401 and the circuit board 300 can be divided by the sealing resin material 1011c near the opening 4010 of the circuit board 300 into the sub-passage side (tip portion 1013) and the connection terminal side (base portion 1014), thereby preventing galvanic corrosion of the connection terminal 1012 due to corrosive gases, etc.
[0086] Furthermore, the gap 1009 between the bottom surface of the package body 1401 and the circuit board 300 is divided into a sub-passage side (tip 1013) and a connection terminal side (base 1014) near the opening 4010 of the circuit board 300 by filling with sealing resin material 1011c. At this time, the area 4015 covered by solder resist 3000 for protecting the wiring layer configured on the circuit board 300, which is located in the gap 1009 between the bottom surface of the package body 1401 and the circuit board 300 on the sub-passage 1002 side, is shortened to the sub-passage 1002 side, and a resin dam portion 4017 (L = 1.5 mm) is formed by the exposed area 4016 where there is no solder resist 3000, thereby allowing a volume of sealing resin material 1011c equivalent to the thickness of the solder resist 3000 to be stored, suppressing the spreading of the resin when filling with sealing resin material 1011c and preventing leakage of sealing resin material 1011c into the sub-passage 1002.
[0087] <Effects> As described above, by positioning the opening 4010 (width: 1 mm, length: 8.3 mm) of the circuit board 300 at a position opposite to the boundary between the tip 1013 and base 1014 of the package body 1401, and by filling the gap 1009 (height: approximately 0.1 mm) between the circuit board 300 and the lower surface of the package body 1401 with sealing resin material 1011c from the opening 4010, the same effects as in the first embodiment are obtained. Furthermore, by providing an exposed area 4016 without resist in the gap 1009 and between the lower surface of the package body 1401 on the sub-passage 1002 side and the circuit board 300, a resin dam (L = 1.5 mm) can be formed, allowing a volume of resin equivalent to the thickness of the resist to be stored, suppressing the spreading of resin when filling with sealing resin material 1011c, and preventing resin leakage into the sub-passage 1002.
[0088] The present invention is not limited to the embodiments described above, and various modifications are included. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace parts of the configuration of each embodiment with the configuration of another embodiment.
[0089] 1...Internal combustion engine control system, 20...Thermal air flow meter (air flow detection device), 140...Chip package, 300...Circuit board, 1002...Sub-passage, 1008...Molding resin, 1009...Gap, 1010, 2010, 3010, 4010...Opening, 1011a, 1011b, 1011c...Sealing resin material, 1012...Connection terminal, 1013...Tip, 1014...Base, 1401...Package body, 3000...Solder resist, 4015...Covered area, 4015...Covered area, 4016...Exposed area
Claims
1. An airflow detection device comprising: a housing having a sub-passage and a circuit chamber; a circuit board housed in the circuit chamber; and a chip package disposed on the circuit board, wherein the chip package has a package body with its tip portion disposed in the sub-passage and its base portion disposed in the circuit chamber; and a connection terminal protruding from the base portion of the package body and connected to the circuit board; and the circuit board has an opening formed therein that penetrates the circuit board and opens at a position opposite to the boundary portion between the tip portion and the base portion of the package body; and a sealing resin material is filled and disposed in the opening and the gap between the package body and the circuit board opposite the opening.
2. The air flow detection device according to claim 1, characterized in that the circuit board has a covered area on its surface that is covered with solder resist and an exposed area that is not covered with solder resist, and the exposed area is provided at the opposing position.
3. The air flow detection device according to claim 1, characterized in that the opening is arranged along the boundary portion and has a length that extends to a position laterally than the base end of the package body.
4. The air flow detection device according to claim 1, characterized in that the opening is formed by at least one slit hole extending along the boundary portion.
5. The air flow detection device according to claim 1, characterized in that the opening is formed by a plurality of circular holes arranged in a row along the boundary portion.
6. The air flow detection device according to claim 1, characterized in that the sealing resin material is arranged to surround the package body circumferentially along the boundary portion.
7. The air flow detection device according to claim 2, characterized in that the exposed area is provided on the surface of the circuit board on the sub-passage side extending from the opening toward the tip of the package body.