Patent Publication Number: US-2020294876-A1

Title: Electronic device having product information and method for reading the product information

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an electronic device having a product information part and a method for reading the product information and, more particularly, to a configuration for safeguarding a product information part of an electronic device. 
     2. Related Art 
     In electronic devices, product information of the electronic device is formed for the purpose of post-manufacturing examination of causes of defects and the like. JP Laid-Open Patent Application No. H05-96895 discloses an IC card in which an IC module is incorporated. The IC module has a substrate on which an IC chip is mounted, and on the substrate, a product information part is formed that displays product information such as the lot number, version number and the like of the IC module. The product information part is formed of a material through which x-rays cannot penetrate. Specifically, the product information part is formed by etching a conductive material. The IC module is covered by molded resin for protection. When confirming the product information, the IC card is irradiated with x-rays. 
     OVERVIEW OF THE INVENTION 
     When forming the product information part of a metal material, it is necessary to protect the product information part from corrosion. The molded resin prevents the product information part from being directly exposed to the outside environment and protects the product information part. However, molded resins may contain components that corrode metal, such as halogen elements. Consequently, if the product information part is in prolonged contact with the molded resin, the product information part corrodes, and identification of the product information with x-rays may become impossible. 
     It is an object of the present invention to provide an electronic device in which corrosion of the product information part is unlikely to occur. 
     The electronic device of the present invention has a function part, a first product information part made of metal, molded resin that covers the function part and the first product information part, and a barrier layer interposed between the first product information part and the molded resin. 
     With this configuration, it is possible to prevent the resin from directly contacting the first product information part, so corrosion of the first product information part by the resin is unlikely to occur. Accordingly, with the present invention, it is possible to provide an electronic device in which corrosion of the product information part is unlikely to occur. 
     The above-described and other objectives, characteristics and advantages of the present application are described in detail below with reference to the attached drawings that exemplify the present application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross-sectional view of a magnetic sensor according to a first embodiment of the present invention. 
         FIG. 2  is a partial enlarged view of  FIG. 1 . 
         FIGS. 3A and 3B  are plan views along line A-A in  FIG. 1 . 
         FIGS. 4A and 4B  are partial side cross-sectional views showing a variation of the magnetic sensor according to the first embodiment. 
         FIGS. 5A-5C  are summary diagrams showing processes for forming a passivation film for the magnetic sensor shown in  FIG. 1 . 
         FIGS. 6A and 6B  are side cross-sectional views of a magnetic sensor according to a second embodiment of the present invention. 
         FIGS. 7A and 7B  are side cross-sectional views of a magnetic sensor according to a third embodiment of the present invention. 
         FIGS. 8A and 8B  are side cross-sectional views of a magnetic sensor according to a fourth embodiment of the present invention. 
         FIG. 9A  is a side cross-sectional view of a magnetic sensor according to a fifth embodiment of the present invention. 
         FIG. 9B  is a plan view along line A-A in  FIG. 9A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Below, some embodiments of the present invention are described. The embodiments described below relate to a magnetic sensor, but the present invention can also be applied to other electronic devices having product information parts. The product information is primarily ID information such as the product name, manufacturing number, lot number and the like of that product, but may also be the manufacturing date, manufacturing plant, manufacturing country or the like and may also be various kinds of identification information necessary in manufacturing procedures, such as wafer identification number or the like. In the description below and the drawings, the direction in which the silicon substrate  4 , the function part  3  and the barrier layer  8  are layered, or the direction orthogonal to the information formation surface  6 A of the first product information part  6 , is called the Z direction. 
     First Embodiment 
       FIG. 1  shows a side cross-sectional view of a magnetic sensor  1  according to a first embodiment of the present invention.  FIG. 2  shows an enlarged view of the vicinity of a first product information part  6 . The magnetic sensor  1  includes a sensor unit  2  provided with a silicon substrate  4  and a function part  3  formed on the silicon substrate  4 . The sensor unit  2  is covered by molded resin  11  except for the bottom part of the silicon substrate  4 . The molded resin  11  includes a resin material such as epoxy resin or the like, and a filler made from inorganic materials such as silica or the like. The resin material in general has a high coefficient of thermal expansion, but the coefficient of thermal expansion of the filler is small. Through this, the coefficient of thermal expansion of the entire molded resin  11  is suppressed, and excessive stress is less likely to applied to the function part  3 . 
     The function part  3  means the part necessary for accomplishing the inherent functions of the magnetic sensor  1 , and, for example, includes a magnetic field detection element  3 A, a wiring layer  3 B connected to the magnetic field detection element  3 A, and the like. As the magnetic field detection element  3 A, a Hall&#39;s element, a magnetoresistive element such as, AMR element, TMR element, GMR element or the like can be preferably used. The function part  3  is covered by an insulating film  5  such as Al 2 O 3  or the like. On the top surface of the insulating film  5 , a first product information part  6  made of metal is formed. The first product information part  6  is made of a metal layer formed in a shape such that the identification information is identifiable or visible. The top surface of the first product information part  6  is an information formation surface  6 A on which the identification information is formed. The first product information part  6  can be formed of an arbitrary material with low x-ray permeability, and, in particular, is preferably formed of a metal with lower x-ray permeability per unit thickness than Al. As this kind of metal, metals with higher specific gravity than Al can be cited, such as Au, W or the like. In this embodiment, the first product information part  6  is formed of Au in consideration of the manufacturing process. The thickness H 1  of the first product information part  6  is preferably about 1˜10 μm to ensure visibility at the time of x-ray irradiation. 
     Electrode layers  7  connected to the wiring layer  3 B are formed on the top surface of the insulating film  5  opposite to the silicon substrate  4 . The electrode layers  7  are made of the same metal (Au) as the first product information part  6  and is positioned at the same distance as the first product information part  6  from the silicon substrate  4 . In addition, the thickness of the electrode layers  7  is the same as the thickness of the first product information part  6 . Consequently, the electrode layers  7  and the first product information part  6  can be formed together in the same process. For example, the resist is provided with openings, which are at the portion where the electrode layers  7  are formed and the portion where the first product information part  6  is formed, and the electrode layers  7  and the first product information part  6  can be formed by plating using resist as a mask. 
       FIGS. 3A and 3B  show plan views along line A-A in  FIG. 1 , that is, the information formation surface  6 A of the first product information part  6 . The first product information part  6  includes a three-dimensional pattern showing at least one of characters, symbols and figures. The characters include at least one of numbers and alphabetic letters but may also include other characters such as Greek letters. The figures include circles, quadrangles and lines but may also include a set of dots such as a QR code, or the like, or a set of lines such as a bar code, or the like. The section recognized as the identification information may be positive or negative. In  FIGS. 3A and 3B , the hatched portions indicate the Au layer.  FIG. 3A  shows the positive-type identification information and, for example, the three lines configuring the letter “A” are formed by protrusions.  FIG. 3B  shows negative-type identification information and, for example, the three lines configuring the letter “A” are formed by indentations and penetration parts provided in the Au layer. The three-dimensional pattern can be formed by a commonly known method such as sputtering of the metal layer. 
     The thickness of the first product information part  6  and the thickness of the electrode layers  7  (dimension in the Z direction) may mutually differ. Referring to  FIG. 4A , the first product information part  6  is thinner than the electrode layers  7 . In this embodiment, it is easy to secure a sufficient thickness of a passivation film  8  so that pinholes caused by unevenness of the first product information part  6  are unlikely to occur in the passivation film  8 . Consequently, the efficacy of protecting the first product information part  6  from the molded resin  11  is further improved. Referring to  FIG. 4B , the first product information part  6  is thicker than the electrode layers  7 . In this embodiment, it is easy to increase the height of the protrusion and the depth of the indentations or penetration parts of the first product information part  6 , so the contrast of the identification information when imaged by x-rays is improved. 
     The first product information part  6  is covered by the passivation film  8  made of Sift, SiN, PI or the like. The passivation film  8  configures the barrier layer for the first product information part  6 . As shown in  FIG. 2 , the passivation film  8  also fills in gaps  6 B in the first product information part  6 . The gaps  6 B in the first product information part  6  are spaces between adjacent letters or adjacent numbers, or spaces inside letters or numbers, when the product information is the positive-type, and are the indentations and penetrating holes configuring the letters or numbers in the case of the negative-type. The passivation film  8  has an opening  8 A that exposes the electrode layers  7 , at a position facing the electrode layers  7 . The electrode layers  7  are electrically connected to an external electrode terminal  10  by a wire  9 . The resin material of the molded resin  11  in some cases contains halogen elements such as Cl, and halogen elements can cause corrosion of metal. In this embodiment, the first product information part  6  is positioned between the function part  3  and the passivation film  8 . In other words, the passivation film  8  is interposed between the first product information part  6  and the molded resin  11 . As a result, direct contact with the resin material by the first product information part  6  is prevented, so corrosion of the first product information part  6  is unlikely to occur. In addition, before the resin hardens, the filler F flowing inside the resin contacts with the passivation film  8  and can damage the passivation film  8  (see  FIG. 2 ). To ensure the soundness of the passivation film  8 , the film thickness H 2  of the passivation film  8  is preferably 0.5 μm or greater. 
     The passivation film  8  can be formed by a method using resist and photolithography. First, as shown in  FIG. 5A , the function part  3  and the insulating film  5  are formed on the silicon substrate  4 , and the first product information part  6  and the electrode layers  7  are formed through plating or sputtering on top of the insulating film  5 . As described above, since the first product information part  6  and the electrode layers  7  are made of Au, they can be simultaneously formed in the same process. Furthermore, the first product information part  6  and the electrode layers  7  are covered by an inorganic film  108  that becomes the passivation film  8 . The top surface of the inorganic film  108  is flattened through polishing. Next, as shown in  FIG. 5B , a resist  12  is formed on top of the inorganic film  108 , and an opening  12 A is formed through photolithography at the position in the resist  12  where the electrode layers  7  are formed. Next, as shown in  FIG. 5C , the inorganic film  108  above the electrode layers  7  are removed and the electrode layers  7  are exposed through milling via the opening  12 A in the resist  12 . Through this, the passivation film  8  covering the first product information part  6  and exposing the electrode layers  7  are formed, and the sensor unit  2  is finished. Furthermore, the magnetic sensor  1  is formed by electrically connecting the electrode layers  7  to the external electrode terminal  10  by the wire  9  and covering the sensor unit  2  with molded resin  11 . 
     When a problem occurs in the magnetic sensor  1 , x-rays are irradiated from outside the molded resin  11 , and the product information included in the first product information part  6  is read. The x-rays are irradiated on the magnetic sensor  1  in the Z direction, and the captured images are recorded in a light-receiving part (photosensitive part) provided on the opposite side of the magnetic sensor from the x-ray irradiation device. When the product information is the positive type, the product information is displayed as black on the image, and when the product information is the negative type, the product information is displayed as gray on the image. The manufacturing number and manufacturing lot included in the product information is beneficial information for investigating causes and planning countermeasures. Normally, the magnetic sensor is used as one part of another product, so it may be difficult to remove the magnetic sensor for inspection. In addition, it may also be difficult to remove the molded resin covering the magnetic sensor. Conventionally, when product information is recorded inside a magnetic sensor, direct verification of the product information was accomplished by removing the magnetic sensor and the molded resin. However, this may damage the function part or change the stress state applied to the function part, and the cause may not be properly determined. In this embodiment, it is possible to read the product information by irradiating x-rays from outside, so the above-described problems do not arise. 
     Second Embodiment 
       FIG. 6A  shows a side cross-sectional view of the magnetic sensor  1  according to a second embodiment of the present invention. This embodiment is the same as the first embodiment except that, in addition to the first product information part  6 , a second product information part  13  is also provided. The second product information part  13  is provided between the silicon substrate  4  and the first product information part  6 , and the insulating film  5  covers the function part  3  and the second product information part  13 . That is, a second barrier layer for the second product information part  13  is formed by the insulating film  5 . The second product information part  13  can have the same configuration as the first product information part  6 . The second product information part  13  is preferably formed of the same metal layer as the wiring layer  3 B and provided at a position equidistant from the silicon substrate  4  with the wiring layer  3 B. Through this, the wiring layer  3 B and the second product information part  13  are arranged at the same level with respect to the silicon substrate  4 , and the wiring layer  3 B and the second product information part  13  can be formed in the same process. However, the position where the second product information part  13  is provided is not limited as long as this position is inside the insulating film  5 .  FIG. 6B  shows a variation of this embodiment. The second product information part  13  is provided on the silicon substrate  4 , and the insulating film  5  covers the function part  3  and the second product information part  13 . 
     Product information the second product information part  13  has is not particularly limited. However, the second product information part  13  is formed at an earlier stage of the manufacturing process than the first product information part  6 , so there are cases in which the second product information part  13  is more beneficial than the first product information part  6 . For example, when confirming wafer identification information and the like midway through the manufacturing procedure, even at early stages of the manufacturing procedure, it is possible to refer to the second product information part  13 . In particular, in the example shown in  FIG. 6B , the product information is formed at the earliest stage, so it is most beneficial for production management. To mutually identify the first product information part  6  and the second product information part  13 , preferably, the first product information part  6  and the second product information part  13  are provided in positions that do not mutually overlap when viewed from the Z direction. X-rays are irradiated to penetrate the magnetic sensor  1 , so the accuracy of the x-ray image is not heavily influenced by the second product information part  13  in the Z direction position. 
     Third Embodiment 
       FIG. 7A  is a side cross-sectional view of the magnetic sensor  1  according to a third embodiment of the present invention. This embodiment is the same as the first embodiment, except that the first product information part  6  is covered by the insulating film  5  that covers the function part  3 . In this embodiment, the barrier layer is configured by the insulating film  5 . Similar to the second embodiment, the first product information part  6  is preferably formed by the same metal layer as the wiring layer  3 B and provided at a position equidistant from the silicon substrate  4  with the wiring layer  3 B. Through this, the wiring layer  3 B and the first product information part  6  are arranged at the same level relative to the silicon substrate  4 , and the wiring layer  3 B and the first product information part  6  can be formed in the same process. Although omitted from the drawing, an element such as a coil or the like may be provided between the first product information part  6  and the passivation film  8 .  FIG. 7B  shows a variation of this embodiment. The first product information part  6  is provided on the silicon substrate  4 , and the insulating film  5  covers the function part  3  and the first product information part  6 . This embodiment, like the second embodiment, is beneficial for manufacturing management because the first product information part  6  is formed at an early stage of the manufacturing process compared to the first embodiment. 
     Fourth Embodiment 
       FIG. 8A  shows a side cross-sectional view of the magnetic sensor  1  according to a fourth embodiment of the present invention. This embodiment is the same as the first embodiment except that the sensor unit  2  is connected to a lead frame  14 . The sensor unit  2  is attached to the lead frame  14  positioned diagonally downward. The configuration of the sensor unit  2  is not limited to the first embodiment and may have the configuration of the second or third embodiment. The lead frame  14  has a relatively thick metal element such as a metal layer, and thus, when the sensor unit  2  is irradiated with x-rays, the first product information part  6  may overlap with the metal element of the lead frame  14 , and the product information may not be read. Consequently, in this embodiment, the mutual positions are adjusted so that the lead frame  14  does not overlap with the first product information part  6  when viewed from the Z direction. Beside the lead frame  14 , metal elements that potentially interfere with the first product information part  6  and prevent reading of the product information may be provided inside the sensor unit  2 . Such metal elements also preferably do not overlap with the first product information part  6  when viewed from the Z direction. 
       FIG. 8B  shows a variation of this embodiment. In this variation, the sensor unit  2  is connected to a circuit  21  such as an application specific integrated circuit (ASIC) or the like, and the circuit  21  is supported by a PCB substrate  22 . The sensor unit  2  is connected to the circuit  21  and the PCB substrate  22 . The PCB substrate  22  is mounted on a PCB substrate  15  via solder balls  16 . In this configuration, there is a possibility that the solder balls  16 , for example, could prevent reading of the product information. Similarly, there is a possibility that metal elements such as wiring or the like provided in the PCB substrates  15  and  22  could prevent reading of the product information. In the embodiment shown in  FIGS. 8A and 8B , when the thickness of the electrical connection section and the metal elements in the Z direction is 40 μm or more, there is a high possibility that reading of the product information will become difficult, depending on the irradiation energy of the x-rays. The first product information part  6  is preferably provided at the position without overlapping with these kinds of electrical connection sections and metal elements when viewed from the Z direction. 
     Fifth Embodiment 
       FIG. 9A  shows a side cross-sectional view of the magnetic sensor  1  according to a fifth embodiment of the present invention. This embodiment is the same as the first embodiment except that the first product information part  6  doubles as a magnetic shield. A pair of magnetic shields  17  to shield an external magnetic field is provided on both sides of the magnetic field detection element  3 A.  FIG. 9B  is a plan view along line A-A in  FIG. 9A . The magnetic shield  17  is made of a soft magnetic material such as NiFe or the like, and the product information is formed on the soft magnetic material. The product information is formed by at least one of indentations, penetration holes or protrusions provided on the soft magnetic material. Supplementary identification information  18  used in the manufacturing process can also be provided in the vicinity of the magnetic shield  17 . With this embodiment, a relatively large magnetic shield  17  is used as the first product information part  6 , so largely displaying the identification information is possible, and visibility at the time of x-ray irradiation improves. Several preferred embodiments of the present invention were described in detail, but it is to be understood that various alterations and variations are possible without departing from the gist or scope of the attached claims.