Semiconductor package

Abstract

To provide a semiconductor package capable of preventing dew condensation.SOLUTION: A semiconductor package 10 includes a pressure sensor 1 and a pressure introduction part 2, and is directly mounted to an exhaust pipe through the pressure introduction part 2. The pressure sensor 1 includes a case body 11 with a lead frame 13 inserted and molded. The case body 11 includes a pressure detection chamber 12 therein into which a pressure sensor chip 21 is housed. The pressure introduction part 2 and the pressure detection chamber 12 are not directly connected, but spatially connected via first and second passages 31, 32 formed inside a lower face 11a of the case body 11. The first passage 31 is formed in a vicinity of the lead frame 13 inserted and molded to the case body 11. An exhaust gas flowing from the exhaust pipe to the pressure introduction part 2 flows into the first passage 31 from a closed port end 2a of the pressure introduction part 2 as a pressure medium 4, and is transmitted to the pressure detection chamber 12 via a vicinity of the lead frame 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to semiconductor packages. [Background technology]

[0002] Patent Document 1 listed below describes a pressure sensor used to measure intake pressure and exhaust pressure of an internal combustion engine, which includes an outer case containing a pressure measurement chamber into which a gas to be measured is introduced, a sensor chip facing the pressure measurement chamber, a sensor support having a support surface that supports the sensor chip, a heat-retaining chamber facing the back surface opposite the support surface of the sensor support, and a gas passage that connects the heat-retaining chamber and the pressure measurement chamber.The technology describes that the sensor chip is kept warm from both main surfaces by the gas to be measured that is introduced from the pressure measurement chamber through the gas passage into the heat-retaining chamber, thereby suppressing condensation around the sensor chip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 212800 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned Patent Document 1, only the space enclosed by the exterior case cover can be heated, and the temperature of the connector pin, which functions as a heat sink to dissipate heat generated in the sensor chip to the outside, is lower than the temperature of the components inside the exterior case. As a result, water vapor in the gas being measured naturally cools near the connection between the connection terminal of the sensor support and the connector pin, causing condensation inside the pressure measurement chamber. This condensation corrodes the connection terminal and wire of the sensor support, which may result in disconnection or short circuit.

[0005] An object of this disclosure is to provide a semiconductor package that can suppress condensation. [Means for solving the problem]

[0006] A semiconductor package according to one aspect of the present disclosure is a semiconductor package that detects the pressure of gas flowing through a pipe, and is as follows: A case body has a pressure detection chamber to which a pressure medium is transmitted. A pressure sensor chip is housed in the pressure detection chamber and converts the pressure received from the pressure medium into an electrical signal. A lead frame is insert-molded into the case body and electrically connected to the pressure sensor chip. A pressure introduction portion protrudes to the outside from the underside of the case body and is spatially connected to the pipe. The gas that serves as the pressure medium flows into the pressure introduction portion from the pipe. The pressure introduction portion has a closed end that is closed at the underside of the case body and an open end that is spatially continuous with the pipe. A passage is formed inside the underside of the case body, extending from the closed end of the pressure introduction portion through the vicinity of the lead frame to the pressure detection chamber, connecting the pressure detection chamber and the pressure introduction portion. [Effects of the Invention]

[0007] The semiconductor package according to the present disclosure has the effect of suppressing condensation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically showing the structure of a semiconductor package according to a first embodiment. [Figure 2] 2 is a plan view schematically showing the layout of the inside of the case body of FIG. 1 as viewed from the lid side. [Figure 3] FIG. 10 is a cross-sectional view schematically showing the structure of a semiconductor package according to a second embodiment. [Figure 4] FIG. 1 is a cross-sectional view schematically illustrating the structure of a semiconductor package according to a reference example. [Figure 5] 5 is a plan view showing a schematic layout of the inside of the case body of FIG. 4 as seen from the lid side. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Summary of Embodiments of the Present Disclosure> (1) A semiconductor package according to one aspect of this disclosure is a semiconductor package that detects the pressure of gas flowing through a pipe, and is as follows: A case body has a pressure detection chamber to which a pressure medium is transmitted. A pressure sensor chip is housed in the pressure detection chamber and converts the pressure received from the pressure medium into an electrical signal. A lead frame is insert-molded into the case body and electrically connected to the pressure sensor chip. A pressure introduction portion protrudes to the outside from the bottom surface of the case body and is spatially connected to the pipe. The gas that serves as the pressure medium flows into the pressure introduction portion from the pipe. The pressure introduction portion has a closed end that is closed at the bottom surface of the case body and an open end that is spatially continuous with the pipe. A passage is formed inside the bottom surface of the case body, extending from the closed end of the pressure introduction portion through the vicinity of the lead frame to the pressure detection chamber, connecting the pressure detection chamber to the pressure introduction portion.

[0010] According to the disclosure above, the lead frame can be actively heated, which makes it possible to make the temperature of the lead frame higher than the temperature of the pressure sensor chip, thereby suppressing condensation near the metal member that forms the electrical connection between the lead frame and the pressure sensor chip, even if the pressure medium contains water vapor.

[0011] (2) Furthermore, in the semiconductor package according to this disclosure, in the above-mentioned (1), the case body may have a space different from the pressure detection chamber, and the passage may reach the pressure detection chamber from the closed end of the pressure introduction portion through the space.

[0012] According to the disclosure above, the space in the case body other than the pressure detection chamber can be used as a space for natural cooling of the pressure medium or for heat transfer to the lead frame.

[0013] (3) Furthermore, in the semiconductor package according to this disclosure, in the above-mentioned (2), the passage may have a first passage that communicates with the pressure introduction portion and the space via the vicinity of the lead frame, and a second passage that communicates with the space and the pressure detection chamber.

[0014] According to the disclosure above, heat is diffused from the pressure medium that flows into a space other than the pressure detection chamber of the case body to the outside via the outer walls (side and top surfaces) of the case body, facilitating natural cooling of the pressure medium. This reduces the amount of water vapor in the pressure medium before it reaches the pressure detection chamber, thereby suppressing condensation in the pressure detection chamber.

[0015] (4) In the semiconductor package according to the present disclosure, in the above-mentioned (2) or (3), the space may be surrounded by a top surface of the case body.

[0016] According to the disclosure above, heat can be diffused from the pressure medium in a space different from the pressure detection chamber of the case body to the outside via the top surface of the case body.

[0017] (5) In the semiconductor package according to the present disclosure, in the above-mentioned (3), the second passage may be formed near a side surface of the case body.

[0018] According to the disclosure above, heat can be diffused from the pressure medium in the second passage to the outside via the side surface of the case body.

[0019] (6) In the semiconductor package according to the present disclosure, in the above-mentioned (1), the space may be formed inside the lower surface of the case body near the lead frame, and the passage may have a first passage communicating between the pressure introducing portion and the space, and a second passage communicating between the space and the pressure detection chamber.

[0020] According to the disclosure above, the lead frame can be actively heated by the pressure medium flowing into a space different from the pressure detection chamber of the case body.

[0021] (7) In the semiconductor package according to the present disclosure, in the above-mentioned (6), the space may face the lead frame in a direction perpendicular to the bottom surface of the case body.

[0022] According to the disclosure above, the lead frame is likely to be heated by the pressure medium that has flowed into a space different from the pressure detection chamber of the case body.

[0023] <Findings underlying this disclosure> As a semiconductor package of a reference example, the structure of an on-board sensor package for measuring exhaust pressure of an internal combustion engine (engine) will be described. FIG. 4 is a cross-sectional view schematically showing the structure of the semiconductor package of the reference example. FIG. 5 is a plan view schematically showing the layout of the inside of the case body of FIG. 4 as seen from the lid side. The semiconductor package 110 of the reference example shown in FIGS. 4 and 5 is an on-board sensor package that includes a pressure sensor 101 and a pressure introducing portion 102 and is attached to piping (exhaust pipe: not shown) of an engine exhaust system. The pressure sensor 101 has a pressure sensor chip 121 mounted in a pressure detection chamber 112 inside the case body 111.

[0024] The pressure introducing portion 102 is a resin pipe (resin piping) integrally molded with the case body 111, and connects the pressure detection chamber 112 and the exhaust pipe. The pressure introducing portion 102 is a passage for the pressure medium 104 that is transmitted to the pressure detection chamber 112. One open end 102a of the pressure introducing portion 102 communicates with the pressure detection chamber 112 on the underside 111a of the case body 111 (the surface on the exhaust pipe side). The other open end 102b of the pressure introducing portion 102 is inserted into a hole formed in the exhaust pipe of the engine, so that the semiconductor package 110 is directly attached to the exhaust pipe. The pressure introducing portion 102 connects the pressure detection chamber 112 and the exhaust pipe in a straight line over the shortest distance in space.

[0025] The case body 111 is a resin molded product in which the lead frame 113 is insert-molded. The case body 111 has a generally concave cross-sectional shape that is partially open, and the partially open portion is closed by the lid 115. The internal space of the case body 111 (the space surrounded by the inner walls (bottom surface 111a and side surfaces) of the case body 111 and the lid 115 (top surface)) is spatially separated by the storage container body 122 into the pressure detection chamber 112 and the wiring chamber 114. The pressure detection chamber 112 is spatially connected to the exhaust pipe in a straight line by the pressure introducing part 102. The wiring chamber 114 is an enclosed space that is shielded from the outside air by the case body 111 and the lid 115, and is shielded from the pressure medium 104 by the storage container body 122.

[0026] The lead frame 113 is provided for each predetermined external connection. One end 113a of the lead frame 113 is exposed to the space inside the case body 111, and the other end 113b protrudes from a side surface (a surface substantially perpendicular to the bottom surface 111a) 111c of the case body 111 into a connecting portion 111d of the case body 111. A storage container body 122 is arranged inside the case body 111 so as to close one open end 102a of the pressure introducing portion 102. The storage container body 122 has a partially open, substantially concave cross-sectional shape, and is supported by a support portion 111b on the bottom surface 111a of the case body 111 with the partially open portion facing the pressure introducing portion 102.

[0027] The space inside the storage container body 122 (the space surrounded by the inner wall of the storage container body 122) is the pressure detection chamber 112. The storage container body 122 spatially separates the pressure detection chamber 112 from another space inside the case body 111 (the space outside the storage container body 122: hereinafter referred to as the wiring chamber) 114. One ends 113a, 123a of the lead frames 113, 123 are connected to each other inside the wiring chamber 114. As described above, the pressure medium 104 does not flow into the wiring chamber 114, so the lead frames 113, 123 do not need to be sealed with the sealing material 116 at the portions exposed to the wiring chamber 114.

[0028] The storage container body 122 is a resin molded product in which a lead frame 123 is insert-molded. One end 123a of the lead frame 123 is exposed to the wiring chamber 114, and the other end 123b is exposed to the pressure detection chamber 112. A recess (hereinafter referred to as a sensor mounting portion) 124 for accommodating the pressure sensor chip 121 is formed inside the storage container body 122. The pressure sensor chip 121 is die-bonded to the bottom surface 124a of the sensor mounting portion 124 via a base member 125 and an adhesive layer 126, and is electrically connected to the other end 123b of the lead frame 123 by a bonding wire 127.

[0029] The pressure sensor chip 121 is an epitaxially resistive semiconductor IC (Integrated Circuit) that utilizes the epitaxial resistance effect of diffused resistors formed inside a silicon (Si) semiconductor, and is a surface-sensitive pressure-receiving type semiconductor IC (Integrated Circuit) in which the gauge surface (circuit surface on which a strain gauge is provided) side is the pressure-receiving surface for the pressure medium 104. The pressure sensor chip 121 has a diaphragm 121a that faces one open end 102a of the pressure introducing portion 102, and a recess 121b on the back surface that is closed by a base member 125. The pressure sensor chip 121, bonding wires 127, and the other end 123b of the lead frame 123 are sealed with a gel-like sealing material 128.

[0030] The operation of the semiconductor package 110 of the reference example will now be described. When the engine is running, combustion gases generated in the engine cylinders during the combustion and expansion stroke of the engine are discharged as exhaust gases through the exhaust pipe to the outside of the vehicle during the exhaust stroke. At this time, part of the exhaust gas flows from the exhaust pipe into the pressure introducing portion 102 and is transmitted to the pressure detection chamber 112 of the pressure sensor 101 as the pressure medium 104. The pressure sensor 101 outputs, as an electrical signal, to an external circuit via the lead frames 123 and 113.

[0031] The airtightness between the pressure introducing part 102 and the exhaust pipe is increased by an O-ring 103 that seals the gap between the pressure introducing part 102 and the exhaust pipe, so that the pressure medium 104 that flows from the exhaust pipe into the pressure introducing part 102 reaches the pressure detection chamber 112 and is transmitted to the pressure sensor chip 121 without leaking to the outside. The path of the pressure medium 104 from the exhaust pipe to the pressure detection chamber 112 is always spatially continuous, and no member is provided that shields the pressure sensor chip 121 from the pressure medium 104. For this reason, the thermal energy generated in the combustion stroke of the engine is transmitted from the pressure medium 104 to the pressure sensor chip 121 with almost no loss.

[0032] Because the pressure detection chamber 112 and the exhaust pipe are spatially connected in a straight line by the pressure introduction part 102, the pressure medium 104 reaches the pressure sensor chip 121 without being cooled down much. The pressure sensor chip 121 receives the most thermal energy from the pressure medium 104 and becomes the hottest of all the components of the pressure sensor 101. On the other hand, the lead frame 113 is made of a metal material and has high thermal conductivity. When connected to an external circuit, the lead frame 113 functions as a heat sink that receives heat generated in the pressure sensor chip 121 from the lead frame 123 and releases it to the outside, so it cools down more easily than other components of the pressure sensor 101.

[0033] Since the temperature of the lead frame 123 is lower than the temperature of the pressure sensor chip 121, the temperature of the sealing material 128 is lower at the portion 142 that seals the lead frame 123 than at the portion 141 that seals the pressure sensor chip 121 (the portion where the pressure medium 104 is closest to the pressure sensor chip 121). The pressure medium 104 contains water vapor that is generated when a fuel (such as gasoline) is burned, and this water vapor permeates the sealing material 128, cools naturally in the relatively low-temperature portion 142 of the sealing material 128, condenses, and is discharged as condensed water. For this reason, this condensation may corrode the lead frame 123 and cause the bonding wire 127 to break or short-circuit.

[0034] One of the problems to be solved in this embodiment is to suppress condensation inside the pressure detection chamber.

[0035] Preferred embodiments of the semiconductor package according to this disclosure will be described in detail below with reference to the accompanying drawings. In the following description of the embodiments and the accompanying drawings, like components are designated by like reference numerals, and duplicated descriptions will be omitted.

[0036] (Details of the first embodiment) A semiconductor package according to an embodiment that solves the above-mentioned problems will be described below. FIG. 1 is a cross-sectional view that schematically shows the structure of a semiconductor package according to a first embodiment. In FIG. 1, the flow of pressure medium 4 is indicated by thick arrows (the same applies to FIG. 3). FIG. 2 is a plan view that schematically shows the layout of the inside of the case body of FIG. 1 as viewed from the lid side. FIG. 2 shows the underside of wiring chamber 14 of case body 11 (underside 11a of case body 11 and the top surface of pressure detection chamber 12) and components arranged on the underside of wiring chamber 14. In FIG. 2, connecting portion 11d for external connection of case body 11 is not shown.

[0037] 1 and 2, a semiconductor package 10 according to an embodiment includes a pressure sensor 1 and a pressure introducing portion 2, and is an in-vehicle sensor package for pressure measurement that is attached to the piping of an internal combustion engine (engine). The semiconductor package 10 is attached, for example, to the piping of the engine's exhaust system (exhaust pipe; not shown). The semiconductor package 10 is useful when gas that is hotter and more humid than the outside air is used as the pressure medium 4, and is particularly suited to measuring the pressure of exhaust gas (exhaust pressure measurement). The semiconductor package 10 may be attached not only to the exhaust pipe of a vehicle, but also to other piping through which gas that is hotter and more humid than the outside air flows (for example, piping for a supercharger).

[0038] The pressure sensor 1 has a pressure sensor chip (semiconductor substrate) 21 mounted in a pressure detection chamber 12 inside a case body 11, and outputs the pressure received by the pressure sensor chip 21 as an electrical signal to an external circuit (not shown) via a lead frame 13. The pressure sensor 1 is supplied with voltage from a power supply IC (not shown) of an ECU (Engine Control Unit) for engine control, or from a power supply IC (not shown) of an ECU (Electronic Control Unit) for controlling the driving performance, safety, and environmental friendliness of the vehicle, and is controlled by the ECU.

[0039] The case body 11 (including the connecting portion 11d), the container body 22 (described later), the pressure introducing portion 2, and the exhaust pipe are made of a high-performance resin, known as a super engineering plastic, such as PPS (Poly Phenylene Sulfide), which has excellent heat resistance, mechanical strength, durability (chemical resistance and abrasion resistance), non-flammability, electrical insulation, and processability. This makes it possible to suppress corrosion caused by exhaust gases and reduce the weight of the engine exhaust system compared to when these engine exhaust system components are made of metal. The lead frames 13 and 23 are primarily made of, for example, phosphor bronze.

[0040] The case body 11 is a resin molded product in which the lead frame 13 is insert-molded, and has, for example, a substantially rectangular planar shape. The case body 11 has a partially open, substantially concave cross-sectional shape, and the partially open portion is closed by a lid 15. The internal space of the case body 11 (the space surrounded by the inner walls (bottom surface 11a and side surfaces) and top surface (lid 15) of the case body 11) is partitioned into a pressure detection chamber 12 and a wiring chamber 14 by a storage container body 22, which will be described later. The pressure detection chamber 12 and the wiring chamber 14 are shielded from the outside air by the case body 11. The pressure detection chamber 12 is spatially connected to the pressure introducing portion 2 via the wiring chamber 14, but is not directly connected to the pressure introducing portion 2.

[0041] The wiring chamber 14 is the space between the lid 15 and the top surface of the pressure detection chamber 12 inside the case body 11 (the space outside the storage container body 22). The lead frames 13 and 23 are exposed in the wiring chamber 14. One ends 13a and 23a of the lead frames 13 and 23 are connected to each other inside the wiring chamber 14. It is preferable that the entire portions of the lead frame 13 and the lead frame 23 connected to the lead frame 13 that are exposed in the wiring chamber 14 are sealed with a general gel-like sealant 16. The sealant 16 functions as a cap film that ensures the airtightness of the lead frames 13 and 23 inside the wiring chamber 14.

[0042] A support portion 11b that supports the storage container body 22 is provided on the inner wall of the lower surface 11a (the surface on the exhaust pipe side) of the case body 11. The support portion 11b is a recess formed on the inner wall of the lower surface 11a of the case body 11. As will be described later, the open end of the side surface of the storage container body 22 is fitted into the support portion 11b. In addition, first and second passages 31 and 32 are provided on the lower surface 11a of the case body 11. The first and second passages 31 and 32 are passages for the pressure medium 4 that is transmitted to the pressure detection chamber 12, and spatially connect the pressure introducing portion 2 and the pressure detection chamber 12. The planar shape, width, and number of the first and second passages 31 and 32 can be set as appropriate.

[0043] Specifically, the first passage 31 is a through-hole that passes through the underside 11a of the case body 11 from one end (closed end) 2a of the pressure introducing portion 2 near the lead frame 13 (i.e., near the sealing material 16) to reach the wiring chamber 14, and connects the wiring chamber 14 to the pressure introducing portion 2. The lead frames 13, 23 can be actively heated by heat dissipation from the pressure medium 4 flowing through the first passage 31. It is only necessary to first allow the pressure medium 4 flowing through the pressure introducing portion 2 to flow near the lead frame 13, and the path of the first passage 31 from the closed end 2a of the pressure introducing portion 2 to the wiring chamber 14 can be set appropriately. The first passage 31 may meander inside the underside 11a of the case body 11 so as to face the lead frame 13.

[0044] The second passage 32 is a through-hole that snakes through the inside of the lower surface 11a of the case body 11, reaching from the wiring chamber 14 to the pressure detection chamber 12, and connects the wiring chamber 14 to the pressure detection chamber 12. Within the wiring chamber 14, heat is dissipated from the pressure medium 4 through the lid 15 of the case body 11 to the outside air, and the pressure medium 4 is naturally cooled. The second passage 32 is preferably provided near the side surface 11c (a surface approximately perpendicular to the lower surface 11a) of the case body 11. Within the second passage 32, heat is more easily dissipated from the pressure medium 4 through the side surface 11c of the case body 11 to the outside air, and the pressure medium 4 is further naturally cooled on its way from the wiring chamber 14 to the pressure detection chamber 12.

[0045] The first and second passages 31 and 32 are formed in spaces that cannot accommodate components due to design within the plane of the bottom surface 11a of the case body 11. For example, as shown in Fig. 2, the case body 11 has a substantially rectangular planar shape that allows necessary components (such as the storage container body 22 and the lead frames 13 and 23) to fit almost exactly on the inner wall of the bottom surface 11a. Therefore, the space on the bottom surface 11a of the case body 11 is, for example, a gap between the side surface 11c of the case body 11 and the components inside the case body 11, and is assumed to be a gap between the inner wall of the side surface 11c of the case body 11 and the lead frames 13 and 23, or between adjacent unsealed lead frames 23.

[0046] A connector portion 11d for external connection of the case body 11 protrudes to the outside from a side surface 11c of the case body 11. The connector portion 11d of the case body 11 is a plug that fits into a socket of a connector portion of a cable (harness: not shown) for wiring inside the engine compartment, and has lead frames 13 (three in FIG. 2) therein as plug pins (terminals) for predetermined external connections. The external connections of the lead frames 13 include, for example, a wiring connection for supplying voltage from a power supply IC of the ECU to the pressure sensor chip 21, a wiring connection for inputting a control signal from the ECU to the pressure sensor chip 21, and a wiring connection for external output from the pressure sensor chip 21.

[0047] By appropriately setting the thickness of the lower surface 11a of the case body 11, the lengths of the first and second passages 31, 32 can be appropriately set. Furthermore, by appropriately setting the thickness of the lower surface 11a of the case body 11, even if the pressure introducing portion 2 faces the pressure detection chamber 12 via the lower surface 11a of the case body 11, it is possible to prevent the pressure detection chamber 12 from being heated by the pressure medium 4 in the pressure introducing portion 2. The case body 11 can be made into an existing integrally molded product by forming the first and second passages 31, 32 therein, and can have substantially the same shape as an existing integrally molded product. Therefore, existing components can be used for the lead frame 13 and the internal components of the case body 11.

[0048] One end 13a of the lead frame 13 is exposed in the wiring chamber 14, and the other end 13b protrudes from the side surface 11c of the case body 11 into the connecting portion 11d of the case body 11. Inside the case body 11, a storage container body 22 is arranged on the inner wall of the bottom surface 11a of the case body 11. The storage container body 22 has a partially open, generally concave cross-sectional shape. The storage container body 22 is supported by the bottom surface 11a of the case body 11 with the partially open portion (the side opposite the bottom surface) facing the bottom surface 11a of the case body 11, and the open end of the side surface (the surface generally perpendicular to the bottom surface) fitting into the support portion 11b of the bottom surface 11a of the case body 11.

[0049] The space inside the storage container body 22 (the space surrounded by the inner wall of the storage container body 22) is the pressure detection chamber 12. The storage container body 22 is a resin molded product in which a lead frame 23 is insert-molded. One end 23a of the lead frame 23 is exposed to the wiring chamber 14, and the other end 23b is exposed to the pressure detection chamber 12. Different lead frames 23 are connected to the respective lead frames 13 of the case body 11 within the wiring chamber 14. A recess (sensor mounting portion) 24 for accommodating the pressure sensor chip 21 is formed on the top surface of the pressure detection chamber 12 (the bottom surface of the storage container body 22) so as to face the pressure detection chamber 12. The sensor mounting portion 24 has, for example, a substantially circular planar shape.

[0050] The pressure sensor chip 21 is an epitaxially resistive semiconductor IC that utilizes the epitaxial effect of a diffused resistor (gauge resistor) formed inside a silicon (Si) semiconductor and is a surface-sensitive pressure-receiving type semiconductor IC in which the gauge surface (circuit surface on which a strain gauge is provided) serves as the pressure-receiving surface for the pressure medium 4 to be detected. The pressure sensor chip 21 has a diaphragm structure in which the thickness of the central portion is made thinner than the thickness of the peripheral portion by forming a recess 21b by etching the central portion from the back side. The pressure sensor chip 21 includes a diaphragm (pressure-receiving portion) 21a that deflects when pressure is applied, a strain gauge (not shown), and a calculation circuit portion (not shown) for amplifying and correcting the output of the strain gauge. The diaphragm 21a has, for example, a substantially circular planar shape.

[0051] The strain gauge is made of a material (Si semiconductor) having a piezo-resistive effect, and is composed of multiple gauge resistors (not shown) of approximately the same shape and resistance value that are bridge-connected, and is provided on the front surface side of the pressure sensor chip 21 facing the diaphragm 21a. Each gauge resistor is electrically connected to the lead frame 13 via a surface electrode (not shown) on the front surface of the pressure sensor chip 21 and a bonding wire 27. The strain of the diaphragm 21a caused by pressure from the pressure medium 4 is converted by the strain gauge into an electrical signal whose magnitude is proportional to the pressure (a potential difference generated across the bridge of the gauge resistors in proportion to the pressure), and the signal is output to an external circuit via the lead frame 13.

[0052] The pressure sensor chip 21 is bonded at its outer periphery on its back surface to one surface of the base member 25, for example, by electrostatic bonding (anodic bonding), so that the base member 25 covers the recess 21b on the back surface. The other surface of the base member 25 is die-bonded (fixed) to the bottom surface 24a of the sensor mounting portion 24 via an adhesive layer 26. The pressure sensor chip 21 and the base member 25 are disposed away from the side wall of the sensor mounting portion 24. The base member 25 is, for example, a glass substrate made of heat-resistant glass. The pressure sensor chip 21, the bonding wires 27, and the other end 23b of the lead frame 23 are sealed with a general gel-like sealant 28.

[0053] The pressure introducing part 2 is a hollow cylindrical resin pipe (resin piping) with a smaller diameter than the exhaust pipe, and connects the first passage 31 and the exhaust pipe. The pressure introducing part 2 is integrally molded with the case body 11 and protrudes to the outside from the lower surface 11a of the case body 11. The pressure introducing part 2 is spatially connected to the pressure detection chamber 12 via the first passage 31, the wiring chamber 14, and the second passage 32. One end (hereinafter referred to as the closed end) 2a of the pressure introducing part 2 is closed by the lower surface 11a of the case body 11 so as not to be directly connected to the pressure detection chamber 12. The closed end 2a of the pressure introducing part 2 may face the pressure detection chamber 12 via the lower surface 11a of the case body 11.

[0054] The semiconductor package 10 is attached directly to the exhaust pipe by inserting the other open end 2b of the pressure introducing portion 2 into a mounting hole formed in the curved surface (side surface) of the exhaust pipe. When the engine is running (while the vehicle is running or idling), exhaust gas flows into the pressure introducing portion 2 as the pressure medium 4. The pressure introducing portion 2 is a passage for the pressure medium 4 that is transmitted to the pressure detection chamber 12, and is always spatially continuous with the exhaust pipe. The pressure introducing portion 2 is short, and the pressure sensor 1 and the exhaust pipe are located relatively close to each other. The pressure introducing portion 2 extends in a straight line from the portion of the underside 11a of the case body 11 that faces the pressure detection chamber 12 toward the exhaust pipe.

[0055] The exhaust pipe is a hollow, cylindrical resin pipe through which exhaust gas (combustion gas) flows during the engine's exhaust stroke, connecting the engine cylinder (not shown) to the outside (outside the vehicle). When the engine is running, exhaust gas constantly flows from the exhaust pipe into the pressure introducing part 2, and is transmitted to the pressure detection chamber 12 as a pressure medium 4 through the pressure introducing part 2, first passage 31, wiring chamber 14, and second passage 32. An O-ring 3 is provided on the outer periphery of the pressure introducing part 2 to seal the gap at the joint between the exhaust pipe and the pressure introducing part 2. This O-ring 3 maintains airtightness between the exhaust pipe and the pressure introducing part 2.

[0056] The operation of the semiconductor package 10 according to the embodiment will be described. When the engine is running, air is drawn into the engine, and combustion gases generated in the engine cylinders during the combustion and expansion stroke of the engine flow into the exhaust pipe as exhaust gas during the exhaust stroke and are discharged outside the vehicle. A portion of the exhaust gas flows from the exhaust pipe as the pressure medium 4 into the pressure introducing portion 2, and from the pressure introducing portion 2, it passes through the first passage 31 in the lower surface 11a of the case body 11, the wiring chamber 14 of the case body 11, and the second passage 32 in the lower surface 11a of the case body 11, and reaches the pressure detection chamber 12.

[0057] Heat is dissipated from the pressure medium 4 that has flowed into the first passage 31 to the lead frame 13 via the thin resin portion (the underside 11a of the case body 11) between the first passage 31 and the lead frame 13. This makes it possible to actively heat the lead frame 13 and the lead frame 23 connected to this lead frame 13. The pressure medium 4 then flows into the wiring chamber 14 and the second passage 32, and heat is dissipated from the pressure medium 4 to the outside air via the lid 15 (and further via the side surface 11c of the case body 11), allowing the pressure medium 4 to cool naturally.

[0058] The naturally cooled pressure medium 4 flows into the pressure detection chamber 12 and is transferred to the pressure sensor chip 21. As a result, the temperature of the sealing material 28 in the pressure detection chamber 12 becomes higher at the portion 42 that seals the lead frame 23 than at the portion 41 that seals the pressure sensor chip 21 (the portion where the pressure medium 4 is closest to the pressure sensor chip 21). This makes it possible to prevent water vapor in the pressure medium 4 from condensing at the portion 42 that seals the lead frame 23, thereby preventing corrosion of the lead frame 23 and breakage or short circuit of the bonding wires 27.

[0059] Furthermore, as the pressure medium 4 is naturally cooled, the water vapor in the pressure medium 4 condenses and is discharged as condensed water. As described above, the pressure medium 4 is naturally cooled within the wiring chamber 14 (and further within the second passage 32), and therefore the water vapor in the pressure medium 4 condenses before the pressure medium 4 reaches the pressure detection chamber 12, thereby reducing (dehumidifying) the amount of water vapor in the pressure medium 4. As the pressure medium 4 with a reduced amount of water vapor flows into the pressure detection chamber 12, condensation within the pressure detection chamber 12 can be suppressed.

[0060] The pressure medium 4 that reaches the pressure detection chamber 12 is transmitted to the pressure sensor chip 21. The pressure sensor 1 outputs the amount of change in the resistance value of the strain gauge, which changes in response to the pressure from the pressure medium 4 applied to the diaphragm 21a of the pressure sensor chip 21, as an electrical signal to an external circuit. The longer the path of the pressure medium 4, the slower the response speed of the pressure sensor 1. However, because the passage of the pressure medium 4 from the exhaust pipe to the pressure detection chamber 12 is kept airtight, the measurement accuracy of the pressure sensor 1 is about the same as that of the pressure sensor 101 of the reference example (see Figures 4 and 5).

[0061] As described above, according to the first embodiment, the pressure introduction portion and the pressure detection chamber are not directly connected, but are spatially connected via first and second passages formed inside the lower surface of the case body of the pressure sensor. The first passage is formed near the lead frame, which is insert-molded into the case body. High-temperature, high-humidity exhaust gas flowing into the pressure introduction portion from the exhaust pipe flows as a pressure medium from the closed end of the pressure introduction portion into the first passage and is transmitted to the pressure detection chamber via the vicinity of the lead frame. The lead frame can be actively heated by the pressure medium flowing through the first passage. This allows the temperature of the lead frame to be higher than the temperature of the pressure sensor chip.

[0062] Furthermore, the pressure medium is naturally cooled as it passes through spaces (wiring chamber and second passage) different from the pressure detection chamber inside the case body before reaching the pressure detection chamber, reducing the amount of water vapor in the pressure medium. As the naturally cooled pressure medium flows into the pressure detection chamber and is transferred to the pressure sensor chip, the temperature of the sealant in the pressure detection chamber becomes higher in the area sealing the lead frame than in the area sealing the pressure sensor chip. This prevents condensation in the area sealing the lead frame, thereby preventing lead frame corrosion and bonding wire breakage and short circuits. Furthermore, as the pressure medium is naturally cooled, the amount of water vapor in the pressure medium decreases, preventing condensation in the pressure detection chamber.

[0063] (Details of the second embodiment) A semiconductor package according to a second embodiment that solves the above-mentioned problems will be described below. Fig. 3 is a cross-sectional view that schematically shows the structure of the semiconductor package according to the second embodiment. A semiconductor package 50 according to the second embodiment differs from the semiconductor package 10 according to the first embodiment in that, instead of the first and second passages 31 and 32 (see Figs. 1 and 2), the semiconductor package 50 has first and second passages 51 and 52 that serve as passages for a pressure medium 54 and a space 53 for heat transfer. The first and second passages 51 and 52 and the space 53 for heat transfer are formed inside the lower surface 11a of the case body 11 at positions close to the pressure introducing portion 2, the lead frame 13, and the pressure detection chamber 12.

[0064] Specifically, the first passage 51 is a through hole that reaches the heat transfer space 53 from the closed end 2a of the pressure introducing portion 2, and connects the space 53 to the pressure introducing portion 2. The first passage 51 is preferably formed over the shortest distance from the closed end 2a of the pressure introducing portion 2 to the space 53. The second passage 52 is a through hole that reaches the heat transfer space 53 to the pressure detection chamber 12, and connects the space 53 to the pressure detection chamber 12. The second passage 52 is preferably formed over the shortest distance from the space 53 to the pressure detection chamber 12. The first and second passages 51, 52 may snake inside the lower surface 11a of the case body 11 so as to face the lead frame 13.

[0065] The heat transfer space 53 is formed in the lower surface 11a of the case body 11 at a position close to the lead frame 13. The heat transfer space 53 should face the lead frame 13 in a direction perpendicular to the lower surface 11a of the case body 11 (preferably, face all of the lead frames 13). Heat is dissipated from the pressure medium 54 that flows into the space 53 from the pressure introducing portion 2 via the first passage 51 to the lead frame 13 via the thin resin portion (the lower surface 11a of the case body 11) between the space 53 and the lead frame 13 to the lead frame 13. Therefore, the lead frame 13, 23 can be actively heated by the pressure medium 54 in the space 53.

[0066] In the second embodiment, the internal space of the case body 11 (the space surrounded by the inner wall of the case body 11 and the lid body 15) is spatially separated into the pressure detection chamber 12 and the wiring chamber 14 by the storage container body 22. The pressure detection chamber 12 and the wiring chamber 14 are shielded from the outside air by the case body 11. The pressure detection chamber 12 is spatially connected to the pressure introducing section 2 via a space 53 in the lower surface 11a of the case body 11, but is not directly connected to the pressure introducing section 2. The wiring chamber 14 is an enclosed space that is shielded from the outside air by the case body 11 and the lid body 15, and is shielded from the pressure medium 54 by the storage container body 22.

[0067] That is, when the engine is running, part of the exhaust gas flows as pressure medium 54 from the exhaust pipe through pressure introducing section 2, first passage 51 on the underside 11a of case body 11, space 53, and second passage 52 to reach pressure detection chamber 12. As in the first embodiment, pressure medium 54 flowing into space 53 actively heats lead frames 13, 23. Thereafter, pressure medium 54 is naturally cooled before being transferred to pressure sensor chip 21. Therefore, as in the first embodiment, the temperature of sealing material 28 in pressure detection chamber 12 is higher at portion 42 sealing lead frame 23 than at portion 41 sealing pressure sensor chip 21.

[0068] As explained above, according to the second embodiment, the same effect as that of the first embodiment can be obtained even when the pressure medium reaches the pressure detection chamber from the pressure introduction part through the heat transfer space in the underside of the case body.

[0069] The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Industrial Applicability]

[0070] As described above, the semiconductor package according to the present disclosure is useful as a semiconductor package for pressure measurement purposes attached to piping, and is particularly suitable for attaching to piping (exhaust pipe) in the exhaust system of an internal combustion engine (engine) to measure exhaust pressure. [Explanation of symbols]

[0071] 1,101 pressure sensors 2,102 Pressure introduction section 2a Closed end of pressure inlet 2b, 102a, 102b Open end of pressure introduction section 3,103 O-rings 4,54,104 Pressure medium 10,50,110 Semiconductor Package 11,111 Case body 11a, 111a Bottom of the case body 11b, 111b Support part on the bottom surface of the case body 11c,111c Side of the case body 11d,111d Case body connector 12,112 Pressure detection chamber 13,23,113,123 Lead frame 14,114 Wiring compartment in case body 15,115 Case body lid 16,28,116,128 Encapsulants 21,121 Pressure Sensor Chip 21a, 121a Pressure sensor chip diaphragm 21b, 121b Recess on the back of the pressure sensor chip 22,122 Pressure sensor chip storage container body 24,124 Sensor mounting part of the container body 24a, 124a Bottom of the sensor mounting area 25,125 Base material 26,126 Adhesive layer 27,127 Bonding Wire 31, 32, 51, 52 Pressure medium passage 41,141 The part of the sealing material that seals the pressure sensor chip (thin circled parts are empty) 42,142 The part that seals the lead frame of the sealing material (each part is not shown in the thin line circle) 53 Heat Transfer Space

Claims

1. A semiconductor package for detecting the pressure of gas flowing through a pipe, a case body having a pressure detection chamber to which a pressure medium is transmitted; a pressure sensor chip accommodated in the pressure detection chamber and converting the pressure received from the pressure medium into an electrical signal; a lead frame that is insert-molded into the case body and electrically connected to the pressure sensor chip; a pressure introducing portion that protrudes from the lower surface of the case body to the outside and is spatially connected to the piping, and into which the gas that serves as the pressure medium flows from the piping; Equipped with the pressure introducing portion has a closed end closed by the lower surface of the case body and an open end spatially continuous with the piping, a passage formed inside the lower surface of the case body, the passage extending from the closed end of the pressure introduction portion to the pressure detection chamber via the vicinity of the lead frame, and connecting the pressure detection chamber to the pressure introduction portion.

2. the case body has a space different from the pressure detection chamber, 2. The semiconductor package according to claim 1, wherein the passage extends from the closed end of the pressure introduction portion through the space to the pressure detection chamber.

3. The passageway is a first passage communicating with the pressure introducing portion and the space via a vicinity of the lead frame; 3. The semiconductor package according to claim 2, further comprising a second passage that connects the space with the pressure detection chamber.

4. 4. The semiconductor package according to claim 3, wherein the space is surrounded by a top surface of the case body.

5. 4. The semiconductor package according to claim 3, wherein the second passage is formed near a side surface of the case body.

6. the space is formed inside the lower surface of the case body and near the lead frame; The passageway is a first passage communicating with the pressure introducing portion and the space; 2. The semiconductor package according to claim 1, further comprising a second passage that connects the space with the pressure detection chamber.

7. 7. The semiconductor package according to claim 6, wherein the space faces the lead frame in a direction perpendicular to the bottom surface of the case body.

8. 8. The semiconductor package according to claim 1, wherein the piping is an engine piping.

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