Abstract:
A physical value detecting apparatus includes a housing having a concave portion; a physical value detecting device housed in the concave portion and having a substantially rectangular shape for converting a physical value into an electric signal and outputting the electric signal; a device for taking out a signal from the physical value detecting device; an adhesive member for adhering the physical value detecting device to the concave portion; and a positioning device provided on an inner wall of the concave portion for positioning the physical value detecting device. The concave portion supports the physical value detecting device at a bottom thereof via the adhesive member without contacting corner parts of the physical value detecting device.

Description:
Background of the Invention and Related Art Statement  
       [0001]     The present invention relates to a physical value detecting apparatus using a housing in which a semiconductor device is housed, and a housing in which a semiconductor sensor device is housed for converting pressure and acceleration into electric signals and outputting the electric signals.  
         [0002]     A semiconductor pressure sensor chip having a piezo resistance effect is generally used in a pressure detecting apparatus for measuring an engine intake pressure of an automobile. The principle of the semiconductor pressure sensor is well known. The semiconductor pressure sensor is constructed such that a bridge circuit of a plurality of semiconductor distortion gauges is formed on a diaphragm made of a material having a piezo resistance effect (such as single-crystal silicon). An electric signal is obtained from a change in gauge resistance of the semiconductor distortion gauges of the bridge circuit according to deformation of the diaphragm.  
         [0003]      FIG. 10  is a view showing such a pressure detecting apparatus, and  FIG. 11  is a sectional view taken along line  11 - 11  in  FIG. 10 . A pressure detecting apparatus  100  is constructed such that a sensor device  1  comprised of a base  11  made of glass, silicon, or the like, and a semiconductor pressure sensor chip  12  provided with a diaphragm  13  mounted on the base  11  is mounted in a concave portion  3  of a resin housing  2  formed of an injection molded thermosetting resin such as epoxy resin or a thermoplastic resin such as PPS (polyphenylene sulfide). Conventionally, an adhesive is disposed in the concave portion  3  of the resin housing  2 , and the base  11  of the sensor device  1  is die-bonded with the adhesive. Then, lead terminals (lead frames)  5  for lead-out passing through the resin housing  2  and integrated with the resin housing  2  with an insertion molding are electrically connected to the semiconductor pressure sensor chip  12  with bonding wires  6 .  
         [0004]     The semiconductor pressure sensor chip  12  is joined to the base  11  so as to reduce stress applied from the resin housing  2 . Further, a gel protective member  7  is used as a protective member for protecting a surface of the semiconductor pressure sensor chip  12  and the bonding wires  6  from contaminants included in a medium whose pressure is measured and for transmitting measured pressure to the semiconductor pressure sensor chip  12 .  
         [0005]     Further, a resin cap  8  formed of a material same as that of the resin housing  2  with the injection molding and having a pressure lead-in pipe  81  connected to a space to be measured is attached to the resin housing  2  to form a pressure detecting chamber  9 . Pressure of the medium to be measured guided through the pressure lead-in pipe  81  is led into the pressure detecting chamber  9 , and a change in the pressure in the pressure detecting chamber  9  is detected as a signal output from the sensor device  1  (refer to Japanese Patent Publication (Kokai) No. 2002-310836).  
         [0006]     FIGS.  12  to  15  are enlarged views showing the concave portion  3  formed in the resin housing  2  in which the sensor device  1  of the pressure detecting apparatus  100  shown in  FIG. 10  is housed.  FIG. 12  is a plan view thereof,  FIG. 13 ( a ) is a sectional view taken along line  13 ( a )- 13 ( a ) in  FIG. 12 , and FIG.  13 ( b ) is a sectional view taken along line  13 ( b )- 13 ( b ) in  FIG. 12 . For the sake of explanation, the bonding wires  6  are shown in  FIG. 12  and  FIG. 13 ( a ).  FIG. 14  is an enlarged view of a circled area in  FIG. 13 ( b ).  
         [0007]     In the pressure detecting apparatus  100  described above, the concave portion  3  is formed to have an opening with an optimum dimension relative to the sensor device  1  so that the sensor device  1  can operates accurately and reliably, and also be made small. When the opening of the concave portion  3  is too small, the resin housing  2  may be deformed due to external stress from the resin cap  81  or thermal stress caused by an environmental temperature, thereby affecting and changing characteristics of the sensor device  1 .  
         [0008]     In particular, when positioning parts  31  protruding from the resin housing  2  at locations corresponding to corner parts  14  of the sensor device  1  are provided for preventing the sensor device  1  from being displaced in a direction θ, the corner parts  14  are located close to the positioning parts  31  and may contact with the positioning parts  31 . Further, the positioning parts  31  and the corner parts  14  shown in  FIGS. 12 and 13  make it difficult to insert the sensor device  1  into the concave portion  3  when the sensor device  1  is adhered to the concave portion  3 .  
         [0009]     Further, if a large amount of adhesive  4  is used for adhering the sensor device  1  to the resin housing  2 , the adhesive  4  overflowing from a bottom of the sensor device  1  enters a space between the sensor device  1  and the base  11 , so that a climbing part  41  is formed in the space between the sensor device  1  and the base  11 . In this case, the deformation of the resin housing  2  is likely to affect and change the characteristics of the sensor device.  
         [0010]      FIG. 15  is a sectional view similar to  FIG. 13 ( b ). As shown in  FIG. 15 , the bottom of the concave portion  3  of the resin housing  2  may have a saucer-shape with the injection molding due to a surface sink  42 . When the bottom has such a variation in height, the resin housing  2  may contact the bottom of the sensor device at the corner parts  14 , so that the deformation of the resin housing  2  affects and changes the characteristics of the sensor device. When the variation becomes greater than 10 μm, this problem is especially prominent. The problems described above are common in an apparatus such as an acceleration detecting apparatus as well as the pressure detecting apparatus, in which a physical value is converted into an electric signal.  
         [0011]     In view of the problems described above, an object of the present invention is to provide a physical value detecting apparatus, in which a physical value is converted into an electric signal to be output. The physical value detecting apparatus is less susceptible to external stress or stress caused by deformation of a housing.  
         [0012]     Further objects and advantages of the invention will be apparent from the following description of the invention.  
       SUMMARY OF THE INVENTION  
       [0013]     To attain the objects described above, according to the present invention, a physical value detecting apparatus includes a housing having a concave portion; physical value detecting means housed in the concave portion and having a substantially rectangular shape for converting a physical value into an electric signal and outputting the electric signal; means for taking out a signal from the physical value detecting means; adhesive means for adhering the physical value detecting means to the concave portion; and positioning means provided on an inner wall of the concave portion for positioning the physical value detecting means. The concave portion supports the physical value detecting means at a bottom thereof via the adhesive means without contacting eight corner parts of the physical value detecting means.  
         [0014]     According to the present invention, a physical value detecting apparatus includes a housing having a concave portion; physical value detecting means housed in the concave portion and having a substantially rectangular shape for converting a physical value into an electric signal and outputting the electric signal; means for taking out a signal from the physical value detecting means; adhesive means for adhering the physical value detecting means to the concave portion; positioning means provided on an inner wall of the concave portion for positioning the physical value detecting means; relief parts provided on the concave portion at locations facing corner parts of the physical value detecting means so that a distance between the positioning means and the physical value detecting means is smaller than a distance between the concave portion and the corner parts of the physical value detecting means; and concaved parts formed at bottoms of the relief parts and having bottoms lower than a bottom of the concave.  
         [0015]     According to the present invention, a physical value detecting apparatus includes a housing having a concave portion; physical value detecting means housed in the concave portion and having a substantially rectangular shape for converting a physical value into an electric signal and outputting the electric signal; means for taking out a signal from the physical value detecting means; adhesive means for adhering the physical value detecting means to the concave portion; positioning means provided on an inner wall of the concave portion for positioning the physical value detecting means; and relief parts provided on the concave portion at locations facing corner parts of the physical value detecting means so that a distance between the positioning means and the physical value detecting means is smaller than a distance between the concave portion and the corner parts of the physical value detecting means.  
         [0016]     In the present invention, the positioning means are preferably formed on two inner walls between the relief parts at locations adjacent to the relief parts. The positioning means are preferably formed of two inner walls adjacent to the relief parts. The relief parts are preferably formed in a circular arc shape. The positioning means is preferably integrated with the housing. The physical value detecting means preferably comprises a semiconductor type sensor using a piezo resistance effect.  
         [0017]     According to the present invention, a housing of a physical value detecting apparatus includes a concave portion for housing physical value detecting means with a substantially rectangular shape in which a physical value is converted into an electric signal and the electric signal is output; positioning means provided on an inner wall of the concave portion; relief parts provided in the concave portion at locations facing corners of the physical value detecting means and at a distance from the physical value detecting means longer than a distance between the positioning means and the physical value detecting means when the physical value detecting means is housed; and concaved parts formed at bottoms of the relief parts and having bottoms lower than a bottom of the concave.  
         [0018]     In the present invention, the relief parts and the concaved parts are provided at four corners of the concave portion, and the positioning parts are provided for allowing the sensor device to displace during wire bonding. Accordingly, it is possible to provide the physical value detecting means with required initial characteristics and reliability in which the sensor device is less susceptible to stress from the resin housing.  
         [0019]     Further, since the concaved parts are provided, the bottoms of the corner parts of the sensor device do not contact or are not close to the resin housing even if a surface sink is formed at the bottom of the concave portion of the resin housing, thereby reducing the effects of the resin housing on the characteristics of the sensor device. Further, since an excess amount of the adhesive stays at areas provided in the depth direction of the resin housing, the adhesive overflowing from the bottom of the sensor chip does not enter a space between the resin housing and the sensor device, thereby reducing the effects of deformation of the resin housing on the characteristics of the sensor chip while a sufficient contact area between the resin housing and the sensor chip is ensured.  
         [0020]     As a result, it is possible to provide physical value detecting apparatuses with required initial characteristics and reliability in a large quantity with a uniform shape. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a plan view showing an essential part of a pressure detecting apparatus according to a first embodiment of the present invention;  
         [0022]      FIG. 2 ( a ) and  2 ( b ) are sectional views of the pressure detecting apparatus shown in  FIG. 1 , in which  FIG. 2 ( a ) is a sectional view taken along line  2 ( a )- 2 ( a ) in  FIG. 1 , and  FIG. 2 ( b ) is a sectional view taken along line  2 ( b )- 2 ( b ) in  FIG. 1 ;  
         [0023]      FIG. 3  is a sectional view similar to  FIG. 2 ( a );  
         [0024]      FIG. 4  is a plan view showing an essential part of a pressure detecting apparatus according to a second embodiment of the present invention;  
         [0025]      FIG. 5 ( a ) and  5 ( b ) are sectional views of the pressure detecting apparatus according to a third embodiment of the present invention, in which  FIG. 5 ( a ) is a sectional view similar to  FIG. 2 ( a ), and  FIG. 5 ( b ) is a sectional view similar to  FIG. 2 ( b );  
         [0026]      FIG. 6  is a plan view showing an essential part of a pressure detecting apparatus according to a fourth embodiment of the present invention;  
         [0027]      FIG. 7  is a perspective view showing an essential part of a pressure detecting apparatus according to a fifth embodiment of the present invention;  
         [0028]      FIG. 8  is a view showing a direction in which load is applied;  
         [0029]     FIGS.  9 ( a ) and  9 ( b ) are charts showing variations in an output voltage of a pressure detecting apparatus, wherein  FIG. 9 ( a ) is a chart of the pressure detecting apparatus according to the first embodiment of the present invention,  FIG. 9 ( b ) is a chart of a conventional pressure detecting apparatus;  
         [0030]      FIG. 10  is a plan view showing a conventional pressure detecting apparatus;  
         [0031]      FIG. 11  is a sectional view taken along line  11 - 11  in  FIG. 10 ;  
         [0032]      FIG. 12  is a plan view showing an essential part of a conventional pressure detecting apparatus;  
         [0033]     FIGS.  13 ( a ) and  13 ( b ) are sectional views of the conventional pressure detecting apparatus shown in  FIG. 12 , in which  FIG. 13 ( a ) is a sectional view taken along line  13 ( a )- 13 ( a ) in  FIG. 12 , and  FIG. 13 ( b ) is a sectional view taken along line  13 ( b )- 13 ( b ) in  FIG. 12 ;  
         [0034]      FIG. 14  is an enlarged view of a circled area shown in  FIG. 13 ; and  
         [0035]      FIG. 15  is a sectional view similar to  FIG. 13 ( a ). 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0036]     Hereunder, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the present invention is applied to a pressure detecting apparatus. However, the present invention is not limited to the pressure detecting apparatus, and may be applied to other physical value detecting apparatuses in which a physical value is converted into an electric signal to be output.  
         [0037]     A first embodiment of the present invention will be described with reference to FIGS.  1  to  3 .  FIG. 1  is a plan view showing essential parts of a pressure detecting apparatus according to the first embodiment of the invention.  FIG. 2 ( a ) is a sectional view taken along line  2 ( a )- 2 ( a ) in  FIG. 1 , and  FIG. 2 ( b ) is a sectional view taken along line  2 ( b )- 2 ( b ) in FIG.  1 . For the convenience of explanation, bonding wires  6  are shown in  FIGS. 1 and 2 ( b ).  FIG. 3  is a sectional view similar to  FIG. 2 ( a ).  
         [0038]      FIG. 1  is a plan view mainly showing a concave portion  3  of a pressure detecting apparatus  100  below lead terminals  5  and bonding wires  6  similar to the conventional apparatus shown in  FIG. 10 . The pressure detecting apparatus  100  is different from the conventional pressure detecting apparatus  100  shown in  FIG. 12  in that relief parts  32  are provided at four corners of the concave portion  3  corresponding to corner parts  14  of a sensor device  1 . Further, concaved parts  33  are provided in a bottom of the resin housing  2  at bottoms of the relief parts  32 . Accordingly, positioning parts  31  are located in the vicinity of the relief parts  32 . The sensor device  1  is attached to the bottom of the concave portion  3  using an adhesive with a function of reducing stress from the resin housing  2  to the sensor device  1 . The adhesive typically has Young&#39;s modulus of about 2 to 50 kgf/cm 2 , and includes, for example, silicon rubber adhesive.  
         [0039]     The relief parts  32  are formed such that a distance between the corner parts  14  of the sensor device  1  and the concave portion  3  is longer than a shortest distance between side parts  15  of the sensor device  1  and the concave portion  3 . It is preferred that the shortest distance between the side parts  15  and the concave portion  3  is 0.0 to 0.4 mm so as to inhibit displacement of the sensor device  1 . The distance between the corner parts  14  and the concave portion  3  is only required to be longer than the shortest distance between the side parts  15  of the sensor device  1  and the concave portion  3 . It is preferred that the distance between the corner parts  14  of the sensor device  1  and the concave portion  3  is made longer as possible to reduce stress as far as the resin housing  2  has a necessary strength and dimension. Further, it is preferred that the relief parts  32  are formed in an arc shape about the respective corner parts  14  when the sensor device  1  is disposed at a desired location, so that the distance between the corner parts  14  and the concave portion  3  is uniformed and stress is reduced uniformly.  
         [0040]     It is preferred that each of the concaved parts  33  formed at the bottoms of the relief parts  32  has a depth of about 0.05 to 0.2 mm. When the concaved parts  33  have a depth less than 0.05 mm, it is difficult to prevent the adhesive from climbing due to a variation in an amount of the adhesive. When the concaved parts  33  have a depth greater than 0.2 mm, the resin housing  2  may lose stiffness. A molding die of the resin housing  2  may include the relief parts  32 , so that the relief parts  32  can be formed when the resin housing  2  is formed. With the relief parts  32 , it is possible to provide a space between the resin housing  2  and the corner parts  14  of the sensor device  1 , i.e. a portion most susceptible to stress from the resin housing  2 , thereby stabilizing characteristics of the sensor device  1 .  
         [0041]     The positioning parts  31  are made of a material same as that of the resin housing  2 , and a molding die of the resin housing  2  includes the positioning parts  31 , so that the positioning parts  31  are formed when the resin housing  2  is formed. Further, the concave portion  3  may have a slope  34  inclined toward an opening edge of the concave portion  3 , so that the sensor device  1  is easily housed in the concave portion  3 .  
         [0042]     As shown in  FIG. 3 , the concaved parts  33  are formed in the bottom of the resin housing  2  at the bottoms of the relief parts  32 . Accordingly, even if a dimension is changed due to a resin surface sink  42  at the bottom of the concave portion  3  after the resin housing  2  is molded, it is possible to prevent the bottoms of the corner parts  14  of the sensor device  1  from becoming close to the resin housing  2 , thereby reducing an effect of deformation of the resin housing  2  on the characteristics of the sensor device  1 .  
         [0043]     When the sensor device  1  is attached to the resin housing  2  using the adhesive  4 , even if an excessive amount of the adhesive  4  is applied, due to the concaved parts  33  in the concave portion  3 , the adhesive  4  overflowing from the bottom of the sensor device  1  does not enter a space between the resin housing  2  and the base  11  of the sensor device  1 , thereby reducing the effect of the deformation of the resin housing  2  on the characteristics of the sensor device  1 . Further, the concaved parts  33  can also reduce external stress and stress caused by deformation of the resin housing  2 , thereby reducing a change in the characteristics of the sensor device  1 .  
         [0044]     A second embodiment of the present invention will be described with reference to  FIG. 4 .  FIG. 4  is a plan view showing an essential part of a pressure detecting apparatus according to the second embodiment, and showing parts same as those shown in the plan view in  FIG. 1 .  
         [0045]     As shown in  FIG. 4 , the relief parts  32  are provided at four corners of the concave portion  3  corresponding to the corner parts  14  of the sensor device  14  as shown in  FIG. 1 . A sectional view taken along line  2 ( a )- 2 ( a ) in  FIG. 4  and a sectional view taken along line  2 ( b )- 2 ( b ) in  FIG. 4  are the same as the sectional views in FIGS.  2 ( a ) and  2 ( b ), respectively. Further, the side parts  15  of the concave portion  3  serve as positioning parts in the sensor device  1 . It is preferred that the distance between the side parts  15  of the concave portion  3  and the sensor device  1  is 0.0 to 0.4 mm as in the first embodiment. In the present embodiment, the same effects as in the first embodiment can be obtained.  
         [0046]     A third embodiment of the present invention will be described with reference to FIGS.  5 ( a ) and  5 ( b ).  FIG. 5 ( a ) is a sectional view same as that taken along line  2 ( a )- 2 ( a ) in  FIG. 1 , and  FIG. 5 ( b ) is a sectional view same as that taken along  2 ( b )- 2 ( b ) in  FIG. 1 . The third embodiment is different from the first embodiment in that the concaved parts  33  are not provided. In the third embodiment, the relief parts  32  are provided at four corners of the concave portion  3  corresponding to the corner parts  14  of the sensor device  14 , as in the first embodiment. As in the first embodiment, there is a sufficient space between the resin housing  2  and the corner parts  14  of the sensor device  1 , i.e. the portion most susceptible to the stress from the resin housing  2 , thereby stabilizing the characteristics of the sensor device  1 .  
         [0047]     A fourth embodiment of the present invention will be described with reference to  FIG. 6 .  FIG. 6  is a plan view showing an essential part of a pressure detecting apparatus according to the fourth embodiment. The fourth embodiment is different from the first embodiment in that a plurality of relief parts  32  is provided at the side parts  15  of the concave portion  3 . With the plurality of relief parts  32  formed in the concave portion  3 , there is a sufficient space between the resin housing  2  and the corner parts  14  and the side parts  15  at four sides of the sensor device  1 , i.e. the portion most susceptible to the stress from the resin housing  2 , thereby stabilizing the characteristics of the sensor device  1 . The plurality of relief parts  32  may be provided at the side part  15  on one side of the concave portion  3 .  
         [0048]     A fifth embodiment of the present invention will be described with reference to  FIG. 7 .  FIG. 7  is a perspective view showing an essential part of a pressure detecting apparatus according to the fifth embodiment. The lead terminals  5  are molded in the resin housing  2  with insertion molding, and the positioning parts  31  are provided for positioning the sensor device  1  (not shown) and have the relief parts  32  at both sides thereof. The concaved parts  33  (not shown) are also provided. Reorganization surfaces  35  are formed for recognizing a height of the lead terminals  5  or the like during wire bonding.  
         [0049]     In the embodiments described above, the relief parts  32  are formed in an arc shape, and the present invention is not limited to the arc shape. Further, the sensor device  1  is constructed such that the semiconductor pressure sensor chip  12  is connected to the base  11 , and the effects of the present invention can be obtained even if the sensor device  1  is comprised only of the semiconductor pressure sensor chip  12 .  
         [0050]     The resin housing for the sensor device is made of a thermosetting resin such as epoxy resin, or a thermoplastic resin such as PPS (polyphenylene sulfide), thereby making it possible to produce the resin housing in a large scale by transfer molding or injection molding.  
         [0051]     As an example 1, the pressure detecting apparatus shown in  FIG. 1  was fabricated. The sensor device  1  was constructed such that the base  11  made of glass was joined to the semiconductor sensor chip  12  using anode junction technique, and had a rectangular shape with a side of 4.1 mm. A distance between the opposed positioning parts  31  was 4.25 mm. The relief parts  32  were formed such that the distance from the corner parts  14  was 0.22 mm when the sensor device  1  was disposed at a desired location. The concaved parts  33  had a depth of 0.11 mm from the bottom of the concave portion  3 . Silicon adhesive with Young&#39;s modulus of 3.9 kgf/cm 2  was used as the adhesive  4 .  
         [0052]     In the pressure detecting apparatus fabricated as above, the corner parts  14  did not contact the concave portion  3  even if the distance between the positioning parts  31  and the sensor device  1  was 0.0 mm. As a comparative example, a pressure detecting apparatus was formed with a structure same as that of the pressure detecting apparatus according to the first embodiment except that the relief parts  32  were not provided.  
         [0053]      FIG. 8  is a view showing a direction in which load was applied to the examples. FIGS.  9 ( a ) and  9 ( b ) are charts showing variations in an output voltage from the pressure detecting apparatus when the side load was applied to the pressure detecting apparatus. The results were based on experiments conducted on three pressure detecting apparatuses of the example 1 and three pressure detecting apparatuses of the comparative examples. In the pressure detecting apparatuses of the example 1, it was found that the sensor output was almost unchanged up to 8 kg/cm 2 .  
         [0054]     According to the present invention, it is possible to reduce the effect of the stress from the resin housing on the sensor chip when the sensor chip is properly positioned. As a result, the pressure detecting apparatus with required initial characteristics and reliability can be provided.  
         [0055]     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.