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Physical quantity sensor, lead frame, and manufacturing method thereforPhysical quantity sensor, lead frame, and manufacturing method therefor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060278027, Physical quantity sensor, lead frame, and manufacturing method therefor. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This is a divisional of co-pending patent application Ser. No. 11/220,816, filed Sep. 8, 2005, which is hereby incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to physical quantity sensors for detecting physical quantities such as magnetism, pressure, and acceleration as well as bearing and direction of magnetism and gravitation. The present invention also relates to lead frames used for physical quantity sensors and to manufacturing methods for manufacturing physical quantity sensors using lead frames. [0004] This application claims priority on Japanese Patent Applications Nos. 2004-263881 and 2004-374105, the contents of which are incorporated herein by reference. [0005] 2. Description of the Related Art [0006] Recently, portable terminal devices such as portable telephones (e.g., cellular phones) have been equipped with GPS functions (where GPS stands for "Global Positioning System") for detecting user's positional information, which is displayed on the screen of a display. GPS functions can be associated with other functions for precisely detecting geomagnetism and acceleration, whereby it is possible to detect bearings (or azimuths), directions, and movements within the three-dimensional space surrounding portable terminal devices held by users. [0007] In order for portable terminal devices to have the aforementioned functions, it is necessary to incorporate physical quantity sensors such as magnetic sensors and acceleration sensors into portable terminal devices. In order to realize detection of bearing and acceleration within the three-dimensional space, it is necessary to use physical quantity sensor chips, which are incorporated into portable terminal devices and whose bases should be inclined by prescribed angles. [0008] Various types of physical quantity sensors having the aforementioned functions have been developed. One type of known physical quantity sensor is a magnetic sensor, which detects magnetism but whose base is not inclined. This magnetic sensor is constituted by a first magnetic sensor chip, which is mounted on the surface of a substrate and is sensitive to magnetic factors of an external magnetic field lying in two directions (i.e., X-axis and Y-axis directions), which cross each other at a right angle therebetween along the surface of the substrate, and a second magnetic sensor chip, which is mounted on the surface of the substrate and is sensitive to a magnetic factor of the external magnetic field lying in a direction (i.e., a Z-axis direction) vertically perpendicular to the surface of the substrate. That is, the magnetic sensor measures geomagnetism factors as vectors in the three-dimensional space with reference to magnetic factors that are respectively detected by a pair of the magnetic sensor chips. [0009] The aforementioned magnetic sensor is set up in such a way that the second magnetic sensor chip vertically stands on the surface of the substrate. This increases the total thickness (i.e., the height lying in the Z-axis direction) of the magnetic sensor. As the total thickness should be reduced to as small as possible, it is preferable to use the foregoing types of physical quantity sensors whose bases are inclined, which are disclosed in Japanese Unexamined Patent Publication No. 2004-125778, Japanese Unexamined Patent Publication No. 2004-128473, Japanese Unexamined Patent Publication No. 2002-156204, and Japanese Unexamined Patent Publication No. H09-292408, for example. [0010] Physical quantity sensors in which physical quantity sensor chips are inclined have an outstanding advantage in that the total thickness thereof can be reduced while securing satisfactory sensitivity. For example, Japanese Unexamined Patent Publication No. H09-292408 discloses an acceleration sensor (or a physical quantity sensor) having a one-sided beam structure in which an acceleration sensor chip (or a physical quantity sensor chip) is inclined in advance with respect to a substrate; hence, even when a sensor package is mounted on the surface of the substrate, it is possible to secure a high sensitivity in a prescribed axial direction matching the inclined direction and to reduce a sensitivity in other axial directions including directions lying along the surface of the substrate. [0011] As described above, physical quantity sensors in which physical quantity sensor chips are inclined to each other may realize mainstream technology in the future because they can reduce the total thickness to as small as possible, and they have various advantages due to inclination of chips. [0012] FIG. 12 shows an example of a physical quantity sensor (or a magnetic sensor) in which physical quantity sensor chips are inclined to each other. Specifically, a magnetic sensor 50 of FIG. 12 is constituted by a pair of magnetic sensor chips (or physical quantity sensor chips) 51 and 52, a plurality of leads 53 for electrically connecting the magnetic sensor chips 51 and 52 to an external device, and a resin mold package 54 for integrally fixing them. The magnetic sensor chips 51 and 52 are each inclined with respect to a lower surface (or a bottom) 54a of the resin mold package 54. [0013] In a manufacturing method of the magnetic sensor 50, the magnetic sensor chips 51 and 52 are respectively bonded onto stages 55 and 56; then, wiring using wires 57 is performed with respect to the magnetic sensor chips 51 and 52 and the leads 53. After the completion of the wiring, the stages 55 and 56 are subjected to inclination. [0014] In the magnetic sensor 50, substantially the same length is set to the wires 57 irrespective of distances between the leads 53 and surfaces 51a and 52a of the magnetic sensor chips 51 and 52. Herein, bonding is basically performed with reference to short distances lying between the leads 53 and the surfaces 51a and 52a of the magnetic sensor chips 51 and 52. In that case, when the stages 55 and 56 are subjected to inclination, any unwanted load is applied to wires used for relatively long distances between them. This may unexpectedly break the wires 57 and may likely cause separation of the wires 57 from the surfaces 51a and 52a of the magnetic sensor chips 51 and 52. In contrast, when bonding is basically performed with reference to long distances lying between the leads 53 and the surfaces 51a and 52a of the magnetic sensor chips 51 and 52, the wires 57 may be loosened and may come into contact with each other so as to cause a short-circuit, wherein the wires 57 are likely to be exposed onto the surface of the resin mold package 54. SUMMARY OF THE INVENTION [0015] It is an object of the present invention to provide a physical quantity sensor and a manufacturing method therefor, wherein leads are not easily broken and are not easily separated from surfaces of physical quantity sensor chips. [0016] It is another object of the present invention to provide a physical quantity sensor, a lead frame therefore, and a manufacturing method therefore, wherein it is possible to easily avoid the occurrence of electric connection failure between leads and physical quantity sensor chips. [0017] In a first aspect of the present invention, a physical quantity sensor is constituted by a plurality of leads whose base portions are arranged in a same plane, and at least one physical quantity sensor chip in which a plurality of electrode pads (or bonding pads) are formed and which is inclined to the plane, wherein the electrode pads are disposed in an inclination direction of the physical quantity sensor chip and are respectively connected to the leads via wires whose lengths substantially match distances between the electrode pads and the leads. As the electrode pads and the leads are connected together using the wires whose lengths substantially match the distances therebetween, a long distance is wired with a relatively long wire, and a short distance is wired with a relatively short wire; hence, it is possible to reduce load applied to the wires. [0018] In the above, tip ends of the leads, which are subjected to wire bonding, have different heights substantially matching heights of the electrode pads on the physical quantity sensor that is inclined. This makes it possible for the wires to have appropriate lengths; hence, it is possible to efficiently perform wire bonding. [0019] A manufacturing method of the physical quantity sensor includes a lead frame forming step for forming a lead frame including a frame portion, at least one stage being surrounded by the leads, and a plurality of interconnection portions for interconnecting the stage to the frame portion, a bonding step for bonding the physical quantity sensor chip onto the stage, a wire bonding step for performing wire bonding to connect the leads to the electrode pads on the physical quantity sensor chip mounted on the stage by use of the wires whose lengths substantially match the distances between the electrode pads and the leads, and a physical quantity sensor chip inclining step for inclining the stage together with the physical quantity sensor chip at a prescribed angle to the frame portion while deforming interconnection portions. Herein, before the physical quantity sensor chip is bonded onto the stage that is inclined, the lengths of the wires are appropriately controlled in response to the distances between the electrode pads and the leads; hence, it is possible to reduce load applied to the wires when the stage is inclined together with the physical quantity sensor chip. In addition, the wire bonding is performed using the wires in a moving direction of the electrode pads on the physical quantity sensor chip that is inclined. This makes it possible to reduce stress applied to the wires in advance; that is, the physical quantity sensor chip moves in a bonding direction of the wires when the physical quantity sensor chip is inclined; hence, it is possible to reliably prevent the wires from being unexpectedly broken. [0020] In the above, the physical quantity sensor chip can be inclined together with the stage before the wire bonding, wherein it is possible to additionally introduce a lead processing step in which the leads are processed such that the heights of the tip ends thereof are changed in conformity with the positions of the electrode pads as the physical quantity sensor chip is inclined. In other words, before the stage is actually inclined, the heights of the tip ends of the leads are changed in advance in response to the positions of the electrode pads attached onto the physical quantity sensor chip that is to be inclined. In such a wire bonding manner, it is possible to reduce stress applied to the wires before the inclination of the physical quantity sensor chip. [0021] The manufacturing method can be partially modified to include a lead frame forming step for forming a lead frame including a frame portion, at least one stage surrounded by the leads, and a plurality of interconnection portions for interconnecting the stage to the frame portion, a bonding step for bonding the physical quantity sensor chip onto the stage, a physical quantity sensor chip inclining step for inclining the stage together with the physical quantity sensor chip at a prescribed angle to the frame portion while deforming the interconnection portions, and a wire bonding step for performing wire bonding to connect the leads to the electrode pads on the physical quantity sensor chip mounted on the stage by use of the wires whose lengths substantially match the distances between the electrode pads and the leads. As the wire bonding is performed after the inclination of the physical quantity sensor chip, it is possible to provide the wires having appropriate lengths. In addition, it is possible to additionally introduce a lead processing step, in which the leads are processed such that the heights of the tip ends thereof are changed in response to the positions of the electrode pads on the physical quantity sensor chip that is inclined, between the lead frame forming step and the physical quantity sensor chip inclining step. That is, the leads are processed; then, the physical quantity sensor chip is inclined; then, the wire bonding is performed using the wires with respect to the leads whose heights substantially match the positions of the electrode pads. This reduces the distances between the electrode pads and the leads as well as the lengths of the wires; hence, it is possible to control the wires having appropriate lengths, and it is possible to reliably prevent the wires from being unexpectedly broken. Furthermore, it is possible to avoid the occurrence of separation of the wires from the electrode pads. [0022] In a second aspect of the present invention, a lead frame comprises at least one stage for mounting a physical sensor chip thereon, a frame having a plurality of leads that are arranged around the stage, and a plurality of interconnection portions for interconnecting the stage to the frame, wherein base portions of the leads that are separated from the stage are disposed substantially in a prescribed plane, the stage is inclined with respect to the prescribed plane, and the tip ends of the leads are disposed along the surface of the stage. In the manufacturing, the physical quantity sensor chip is mounted on the surface of the stage; then, wire bonding is performed such that the tip ends of the leads are electrically connected to bonding pads formed on the surface of the physical quantity sensor chip via wires. Thereafter, an assembly of the lead frame and physical quantity sensor chip is held between metal molds having cavities (i.e., resin forming spaces), into which a melted resin is injected, thus forming a resin mold package for integrally fixing the lead frame and physical quantity sensor chip. Continue reading about Physical quantity sensor, lead frame, and manufacturing method therefor... Full patent description for Physical quantity sensor, lead frame, and manufacturing method therefor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Physical quantity sensor, lead frame, and manufacturing method therefor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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