Abstract:
The present invention provides piezoelectric surface mount devices in which the area of the mounting terminals is reduced, leading to reduction of manufacturing cost. A piezoelectric device comprises a package base ( 120 ) including a bottom surface having a long edge and a short edge and a pair of mounting terminals formed on respective short edges of the package base. The pair of mounting terminals are separated by a predetermined longitudinal distance (X 3 ) and are arranged as close as possible to the longitudinal center line of the package base. The predetermined distance is sufficient to prevent electrical short when mounting the piezoelectric device onto the printed substrate. The maximum width (Z 2 ) of each mounting terminal measured in a direction parallel with the short edges of the package base is less than one half the width of the short edge (Z 1 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Japan Patent Application No. 2011-025685, filed on Feb. 9, 2011, in the Japan Patent Office, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to piezoelectric devices having a mounting terminal with reduced surface area. 
     DESCRIPTION OF THE RELATED ART 
     A conventional surface-mountable piezoelectric device comprises a piezoelectric vibrating piece that vibrates when electrically energized. Respective mounting terminals are formed on a bottom surface of surface-mountable piezoelectric devices, and the devices are mounted onto a printed substrate by bonding the mounting terminal and the printed substrate using solder. The hardened solder may crack when exposed under significant temperature change. 
     Conventionally, cracks formed on solder have been prevented by increasing the size (surface area) of the mounting terminals of the piezoelectric devices. For example, Japan Unexamined Patent Document No. 2004-64701 discloses a piezoelectric device, in which the bonding strength between a surface mount device and substrate is increased by increasing the area of the mounting terminal to one half of the area of the bottom surface of the quartz-crystal vibrating device. 
     However, according to Japan Unexamined Patent Document No. 2004-64701, in order to make the surface area of the mounting terminals relatively large, significant amounts of electrode forming materials are required to manufacture the mounting terminals. Since expensive materials such as gold are used in the manufacture of piezoelectric devices, increasing the size of the mounting terminals can be costly. 
     It is therefore the purpose of the present invention to provide piezoelectric devices in which the area of the mounting terminals is reduced, leading to a corresponding reduction of manufacturing cost and prevention of solder cracks. 
     SUMMARY 
     A first aspect of the present disclosure relates to a piezoelectric device mounted onto a printed substrate using solder. The piezoelectric device comprises a piezoelectric vibrating piece having a pair of excitation electrodes and a package base including a generally rectangular bottom surface having side edges parallel with a longitudinal centerline (hereafter “long edge”), end edges perpendicular to the side edges and bisected by the longitudinal center line (hereafter “short edge”) and a pair of mounting terminals formed on the bottom surface of the package base adjacent to each short edge. The pair of mounting terminals is electrically connected to the pair of excitation electrodes and the piezoelectric device is mounted onto the printed substrate. The pair of mounting terminals is situated in a predetermined configuration as close as possible in the longitudinal direction while maintaining a separation between the terminals in a longitudinal direction to prevent electrical short when mounting the piezoelectric device onto the printed substrate. The maximum width of the mounting terminal measured parallel with the short edges of the package base is less than a half of the width of the short edge. 
     A second aspect of the present disclosure pertains to piezoelectric devices. In its second aspect, the predetermined distance between the mounting terminals in the first aspect is between 0.5 mm to 1.0 mm. 
     A third aspect of the present disclosure pertains to piezoelectric devices. In its third aspect, the pair of mounting terminals in the first aspect or second aspect is symmetrical to a straight line that passes through a centerline in the short edge and parallel to the long edge (bisecting the piezoelectric device and the mounting terminals). 
     A fourth aspect of the present disclosure pertains to piezoelectric devices. In its fourth aspect, the pair of mounting terminals in the first to third aspects, each of the mounting terminals comprising a respective first edge, which is an edge of the mounting terminal formed on the short edges of the bottom surface of the package base, and a respective second edge having different length than the first edge and parallel to the first edge; wherein the respective second edges of the pair of mounting terminals are separated by a predetermined distance, and the first edge or the second edge of the mounting terminals have a length equal to the maximum width of the mounting terminal, measured parallel with the short edges of the package base. 
     A fifth aspect of the present disclosure pertains to piezoelectric devices. In its fifth aspect, the mounting terminals of the fourth aspect have trapezoid profile. 
     A sixth aspect of the present disclosure pertains to piezoelectric devices. In its sixth aspect, the profiles of the mounting terminals in the fourth aspect have the shape of two rectangles arranged on the center line of the package base and in contact with each other. A first rectangle extends from a first edge at the short edge of the package base to a third edge longitudinally spaced from the first edge and parallel therewith. A second rectangle extends from a second edge longitudinally spaced from the third edge to a fourth edge overlapping with the third edge. 
     A seventh aspect of the present disclosure pertains to piezoelectric devices. In its seventh aspect, each of the pair of mounting terminals in the first to third aspects comprise a respective first edge, which is an edge of each mounting terminal formed at the short edge of the bottom surface of the package base, and a respective second edge that is parallel to the first edge; wherein the second edges of the pair mounting terminals are separated by a predetermined longitudinal distance, and the first edge or the second edge are shorter than the maximum width of the mounting terminals measured parallel with the short edges of the package base. 
     An eighth aspect of the present disclosure pertains to piezoelectric devices. In its eighth aspect, the pair of mounting terminals in the first to third aspects comprises respective first points, which are the closest points to the other mounting terminals, and respective second points and respective third points are formed on respective edge portions at the maximum width of the mounting terminals measured parallel with the short edges of the package base. Each point is connected to the other points by a straight line or curved line to define the shape of the mounting terminals. A straight line may connect the first point and the second point, and the first point and the third point. Alternatively, a curved line may connect the second point and the third point by passing through the first point in arch manner. 
     According to the present invention, the piezoelectric devices are provided, in which the area of the mounting terminals is made smaller, leading to reduction of manufacturing cost and prevention of solder cracks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a piezoelectric device  100 . 
         FIG. 2A  is a cross-sectional view of the piezoelectric device  100  of  FIG. 1  bonded to a printed substrate  160 . 
         FIG. 2B  is a plan view of the bottom surface of the package base  120  of the piezoelectric device of  FIGS. 1 and 2 . 
         FIG. 3A  is a plan view of a half of the bottom surface of an alternative package base  120   a  of the piezoelectric device  100   a  taken along the −X-axis side. 
         FIG. 3B  is a plan view of a half of the bottom surface of an alternative package base  120   b  of the piezoelectric device  100   b  taken along the −X-axis side. 
         FIG. 3C  is a plan view of a half of the bottom surface of an alternative package base  120   c  of the piezoelectric device  100   c  taken along the −X-axis side. 
         FIG. 3D  is a graph showing the result of the thermo-shock cycle test of the piezoelectric devices illustrated in  FIGS. 3A-3C . 
         FIG. 4A  is a plan view of the bottom surface of an alternative package base  220   a.    
         FIG. 4B  is a plan view of the bottom surface of an alternative package base  220   b.    
         FIG. 4C  is a plan view of the bottom surface of an alternative package base  220   c.    
         FIG. 5A  is a plan view of the bottom surface of an alternative package base  320   a.    
         FIG. 5B  is a plan view of the bottom surface of an alternative package base  320   b.    
         FIG. 5C  is a plan view of the bottom surface of an alternative package base  320   c.    
         FIG. 6A  is a plan view of the bottom surface of an alternative package base  420   a.    
         FIG. 6B  is a plan view of the bottom surface of an alternative package base  420   b.    
         FIG. 7A  is a plan view of the bottom surface of an alternative package base  520   a.    
         FIG. 7B  is a plan view of the bottom surface of an alternative package base  520   b.    
         FIG. 8A  is a plan view of the bottom surface of an alternative package base  620   a.    
         FIG. 8B  is a plan view of the bottom surface of an alternative package base  620   b.    
     
    
    
     DETAILED DESCRIPTION 
     Various representative embodiments are described below with reference to the respective drawings. It will be understood that the scope of the disclosure is not limited to the described embodiments, unless otherwise stated. 
     First Embodiment 
     Configuration of the Piezoelectric Device  100   
       FIG. 1  is an exploded perspective view of a piezoelectric device  100 . The piezoelectric device  100  comprises a piezoelectric vibrating piece  130 , a package lid  110  and a package base  120 . The piezoelectric vibrating piece  130  is fabricated from an AT-cut quartz-crystal material, for example. An AT-cut quartz-crystal material has a principal surface (in the YZ plane) that is tilted by 35° 15′ about the Y-axis of a crystal-coordinate system (XYZ) in the direction of the Y-axis from the Z-axis around the X-axis. Thus, in the following description, new axes tilted with respect to the axial directions of the quartz-crystal material are denoted as the Y′-axis and Z′-axis, respectively. Therefore, in the piezoelectric device  100 , the longitudinal direction of the piezoelectric device is the X-axis direction, the height direction is the Y′-axis direction, and the direction that is perpendicular to the X-axis direction and Y′-axis direction is the Z′-axis direction. 
     In the piezoelectric device  100 , the piezoelectric vibrating piece  130  is mounted on top of the +Y′-axis surface of the package base  120 . The piezoelectric device  100  is formed by bonding together the package lid  110  and the package base  120  so as to hermetically seal the piezoelectric vibrating piece  130 . 
     In the piezoelectric vibrating piece  130 , the excitation electrodes  131  are situated on both principal surfaces (+Y′-axis and −Y′-axis surfaces). The extraction electrodes  132  are extracted from respective excitation electrodes  131  in the −X-axis direction. The extraction electrode  132  connected to the excitation electrode  131  formed on the −Y′-axis direction is extracted to the −Z′-axis edges on the −X-axis side of the −Y′-axis surface. Also, the extraction electrode  132  connected to the excitation electrode  131  formed on the +Y′-axis surface is extracted to the +Z′-axis edges on the −X-axis side of the −Y′-axis surface. The electrodes, such as the excitation electrodes  131  and extraction electrodes  132  formed on the piezoelectric vibrating piece  130  comprise a chromium layer (Cr) on the piezoelectric vibrating piece  130 , followed by overlaying layer of gold (Au). 
     A recess portion  111  is situated on the −Y′-axis surface of the package lid  110 . A bonding surface  112  is formed on the periphery of the recess portion  111 . The package lid  110  is bonded to the package base  120  via the bonding surface  112 . 
     A recess portion  121  is situated on the +Y′-axis surface of the package base  120 . A bonding surface  122  is formed on the periphery of the recess portion  121 . On the recess portion  121 , a pair of connection electrodes  123  is formed that is electrically connected to the extraction electrode  132  of the piezoelectric vibrating piece  130 . A pair of mounting terminals  124  is situated mainly on the −Y′-axis surface of the package base  120 . The pair of connection electrodes  123  and the pair of mounting terminals  124  are electrically connected with each other via a through-hole electrode  125  (see  FIG. 2A ) that extends through the package base  120 . The package base  120  is fabricated from, for example, ceramics. Also, the connection electrodes  123 , mounting terminals  124  and through-hole electrodes  125  are fabricated from tungsten, for example, nickel is formed on top of tungsten as a foundation layer, and overlaying layer of gold is formed thereon. 
       FIG. 2A  is a cross-sectional view of the piezoelectric device  100  bonded to a printed substrate  160 , such as a printed circuit (PC) board. The cross-sectional view of the piezoelectric device  100  in  FIG. 2A  is taken along A-A line. The piezoelectric vibrating piece  130  is bonded to the package base  120  using the electrically conductive adhesive  141 . Also, the extraction electrodes  132  of the piezoelectric vibrating piece  130  are electrically connected to the connecting electrodes  123  situated on the package base  120  via the electrically conductive adhesive  141 . The package lid  110  and package base  120  are bonded together using sealing material  142  formed between the bonding surface  112  and bonding surface  122 . Respective printed substrate electrodes  161  are formed on a printed substrate  160 . The piezoelectric device  100  is bonded to the printed substrate  160  by bonding together the mounting terminal  124  and the printed substrate  161  using solder  143 . The mounting terminals  124  of the piezoelectric device  100  comprise respective bottom surface terminals  126 , situated on the −Y′-axis surface of the package base  120 , and respective side surface terminals  129  situated on both +X-axis and −X-axis surfaces of the package base  120 . The formation of the solder  143  can be easily checked by forming respective side surface terminals  129 , since the solder  143  is formed so as to cover the side surface terminals  129  formed on respective side surfaces of the package base  120 . 
       FIG. 2B  is a plan view of the package base  120 , which is generally rectangular and has a length X 1  and a width Z 1 . The long edges of the package base  120  extend in the X-axis direction and the short edges of the package base extend in the Z′-axis direction Therefore, if the longitudinal length of the package base  120  is denoted as X 1 , and the width is denoted as Z 1 , the length X 1  is longer than the width Z 1 . The length X 1  may be, for example, 8.0 mm and the width Z 1  is 4.5 mm. The pair of mounting terminals  124  formed on the package base  120  is formed so as to align in the X-axis direction along a longitudinal center line AX 1  of the package base  120 . Each bottom surface terminal  126 , which is the mounting terminal  124  on the bottom surface of the package base  120  has a rectangular profile having a long edge in the X-axis direction and a short edge in the Z′-axis direction. Whenever the maximum width of a bottom surface terminal  126  in the short edge direction is denoted as Z 2 , the maximum width in the long edge direction is denoted as X 2  and the distance between two bottom surface terminals  126  is denoted as X 3 , the bottom surface terminals  126  of the package base  120  are situated so that the maximum dimensions are 3.575 mm in the long edge direction X 2 , 2.25 mm in the short edge direction Z 2 , and 0.6 mm X 3  between a pair of bottom surface terminals  126 . Also in the bottom surface terminals  126 , the edge of the bottom surface terminal  126  adjacent the edge of the package base  120  in the longitudinal direction (the short edge of the package base) is denoted as the first edge  127  and the edge of the bottom surface terminal  126  parallel to and longitudinally spaced from the first edge  127  is denoted as the second edge  128 . In this case, the two second edges  128  of the bottom surface terminals  126  are separated from each other by a distance X 3 . The width of the edge terminal  129  in the Z′-axis direction is the same width as the first edge  127 . Further, the pair of mounting terminals  124  is formed symmetric to the longitudinal centerline AX 1 , which extends through the center of the short edges of the package base  120 . Formation mounting terminals  124  symmetric to the centerline AX 1  avoids tilting of the piezoelectric device  100  to the Z′-axis direction while mounting the piezoelectric device  100  onto a printed substrate  160 . The term “symmetric” as used in the context of this application means that the longitudinal centerline AX 1  of the package base  120  bisects the mounting terminals  124 . 
     Thermo-Shock Cycle Test 
     Whenever abrupt change in temperature (thermal shock) occurs, the solder  143 , which bonds the piezoelectric device  100  and the printed substrate  160 , is stressed and can crack (including chips and cracks). This crack occurs between the +X-axis and −X-axis edges (dotted line  150  in  FIG. 2 ) of the solder  143 . When the crack extends through the solder in the X-axis direction, it can form an electrical disconnection between the mounting terminal  124  of the piezoelectric device  100  and the printed substrate electrode  161  of the printed substrate  160 . The percentage of the solder crack refers to the percentage of the crack in the X-axis direction on the solder  143  over the total length of the solder  143  in the X-axis direction. As described below, an experiment was performed to determine the resistance of a piezoelectric device against thermal shock, by continuously applying heat shock, such as abrupt change in temperature, to the piezoelectric device mounted onto a printed circuit board. 
     In the thermal shock cycle test, the piezoelectric device mounted onto a printed substrate was kept under the −40 degrees (Celsius) for five minutes, and then kept above 125 degrees (Celsius) for five minutes. The cycle was repeated for several times to determine the percentage of solder crack. The thermal shock cycle test was done for three different types of piezoelectric devices having different maximum width Z 2  of the mounting terminal  124  in the short edge direction. The printed substrate used for thermal-shock cycle test is glass epoxy substrate, and lead-free solder is used. Also the thickness of the solder when the piezoelectric device is mounted onto a printed substrate is 150 μm. 
       FIGS. 3A to 3C  show a half of the bottom surface of the package base after the thermo-shock cycle test. Each piezoelectric device used in the thermo-shock cycle test has different maximum width Z 2  in the short edge direction of the mounting terminal  124  than the piezoelectric device  100 . Aside from the maximum width being different, other components are similar to each other.  FIG. 3A  is a plan view of a half of the package base  120   a  of the piezoelectric device  100   a  taken along the −X-axis side. The maximum width Z 2   a  of the mounting terminal  124   a  of the package base  120   a  in the short edge direction is 4.3 mm.  FIG. 3B  is a plan view of a half of the package base  120   b  of the piezoelectric device  100   b  taken along the −X-axis side. The maximum width Z 2   b  of the short edge direction of the mounting terminal  124   b  situated on the package base  120   b  is 2.0 mm.  FIG. 3C  is a plan view of a half of the package base  120   c  of the piezoelectric device  100   c  taken along the −X-axis side. The maximum width Z 2   c  of the mounting terminal  124   c  of the package base  120   c  in the short edge direction is 1.4 mm. 
       FIG. 3D  is a graph showing the result of the thermo-shock cycle test of the piezoelectric device. The vertical axis indicates the percentage of the solder crack, and the horizontal axis indicates the number of thermo-shock cycle. In the vertical axis indicating the percentage of the solder crack, 100% refers to the condition where the crack fully extends through the X-axis direction of the solder  143 . Also, target percentage of the solder crack in condition for use is 85% or lower. The graph shows the percentage of solder crack and its error range of each piezoelectric device at 500-times, 1,000-times and 1,500-times. For the purpose of viewing the result at ease, the result of the thermo-shock cycle test of the piezoelectric device  100   b  is indicated on the 450-times, 950-times and 1,450-times axes and the result of the piezoelectric device  100   c  is indicated on the 550-times, 1,050-times and 1,550-times axes respectively, even though each cycles were counted at 500-times, 1,000-times and 1,500-times. Also, the marks on the drawings indicate the average of the solder crack at each thermo-shock cycles. 
     An average of the percentage of solder crack of the piezoelectric device  100   a  is 0.8% at 500-times, 2.1% at 1,000-times and 10.3% at 1,500-times. An average of the percentage of solder crack of the piezoelectric device  100   b  is 0.6% at 500-times, 3.3% at 1,000-times and 20.3% at 1,500-times. An average of the percentage of solder crack of the piezoelectric device  100   c  is 0.3% at 500-times, 2.8% at 1,000-times and 21.9% at 1,500-times. Also, in the piezoelectric device having long distance X 3  between each mounting terminals, the percentage of solder crack reaches nearly 100% when the thermo-shock cycle reaches 1,000-times. Also, the percentage of solder crack permissible as a product is set at 85%. 
     In the piezoelectric device  100   a , an area of the mounting terminal  124   a  situated on the bottom surface of the package base  120   a  is formed relatively wide, and thus the percentage of solder crack is relatively low. 
     In the mounting terminal  124   b  of the piezoelectric device  100   b , the percentage of solder crack is similar to the number that of the piezoelectric device  100   a , which indicates low percentage of solder crack. Although the percentage of solder crack increases at the thermo-shock cycle of 1,500-times, the number is still lower than 85%, therefore the percentage of the solder crack is permissible as a product. Similar to the piezoelectric device  100   b , in the piezoelectric device  100   c , the percentage of solder crack is similar to the number that of the piezoelectric device  100   a  at 1,000-times, and also indicates low percentage of solder crack at the thermo-shock cycle of 1,500-times. 
     According to the result shown in  FIG. 3D , considering the formation of the mounting terminal, if the distance X 3  between the mounting terminals is as narrow as possible, the percentage of the solder crack does not increase in a major way even if width of the mounting terminal in the short edge direction is formed narrow. Also, from the viewpoint of decreasing the usage amount of the electrode materials, the maximum width Z 2  of the mounting terminal in the short edge direction is preferred to be less than a half of the width Z 1  of the short edge direction of the package base. Here, the amount of usage of the electrode materials is cut down to more than a half than that of forming the maximum width Z 2  of the mounting terminal in the short edge direction to the same length as the width Z 1  of the package base in the short edge direction. Also, although the distance X 3  between each electrode is set at 0.6 mm, the distance X 3  falls preferably between 0.5 mm to 1.0 mm. If the distance X 3  is shorter than 0.5 mm, the solder bonding each mounting terminal may connect to each other, thus causing electrical short. If the distance X 3  is longer than 1.0 mm, the percentage of solder cracks increases. 
     Second Embodiment 
     The result from the thermo-shock cycle test in the first embodiment shows that the percentage of solder cracks does not increase significantly even if the maximum width Z 2  of the mounting terminal in the short edge direction is relatively narrow. Therefore, amount of the electrode materials can be decreased by forming the maximum width Z 1  of the package base in the short edge direction much narrower than the maximum width Z 2  of one mounting terminal in the short edge direction. On the other hand, if the maximum width Z 2  of the mounting terminal in the short edge direction is formed too narrow, the bonding strength between the piezoelectric device and the printed substrate may become too narrow. Therefore, it is desired to form the maximum width Z 2  of the mounting terminal in the short edge direction at a certain size, and mount the piezoelectric device in a stable manner. In the following embodiments, mounting terminals having different profiles are explained, in which the bonding strength between the piezoelectric device and the printed substrate is maintained and the amount of electrode materials is decreased. Also in the following embodiments, the length X 1  of the package base in the long edge direction, the width Z 1  of the package base in the short edge direction, the maximum length X 2  of the bottom surface terminal in the longitudinal direction, the maximum width Z 2  of the bottom surface electrode in the short edge direction, and the distance X 3  between bottom surface terminals in the longitudinal direction refer to the same reference numerals as the piezoelectric device  100 . In the second embodiment, a package base having first and second edges  127 ,  128  of different length and having trapezoid profile is explained. 
       FIG. 4A  is a plan view of the package base  220   a . The package base  220   a  comprises a pair of mounting terminals  224   a , and each mounting terminal is constituted of a bottom surface terminal  226   a  and a side surface terminal  229   a . The bottom surface terminal  226   a  is trapezoid-shaped, in which the width of the first edge  227   a  is less than the width of the second edge  228   a . Also, the width of the second edge  228   a  of the bottom surface terminal  226   a  is the maximum width Z 2  of the bottom surface terminal  226   a  in the short edge direction. Further, the width of the side surface electrode  229   a  in the Z′-axis direction is the same width as the first edge  227   a . In the package base  220   a , an area of the mounting terminal  224   a  is small, thus reducing the amount of electrode materials. Also, the maximum width Z 2  of the bottom surface electrode  226   a  in the short edge direction provides an area for bonding the solder. 
       FIG. 4B  is a plan view of the package base  220   b . The package base  220   b  comprises a pair of mounting terminals  224   b , and each mounting terminal is constituted of a bottom surface terminal  226   b  and a side surface terminal  229   b . The bottom surface terminal  226   b  is trapezoid-shaped, in which the width of the first edge  227   b  is greater than the width of the second edge  228   b . Also, the width of the first edge  227   b  of the bottom surface terminal  226   b  is the maximum width Z 2  of the bottom surface terminal  226   b  in the short edge direction. Further, the width of the side surface electrode  229   a  in the Z′-axis direction is the same width as the first edge  227   b . In the package base  220   b , area of the mounting terminal  224   b  is small, and thus reduces the amount of electrode materials. Also, area for bonding the solder  143  can be obtained by acquiring the maximum width Z 2  of the bottom surface terminal  226   b  in the short edge direction. Further, the formation of the solder  143  can be easily checked visually by forming the side surface electrode  229   b  in the Z′-axis direction in a wide manner. 
       FIG. 4C  is a plan view of the package base  220   c . The package base  220   c  comprises a pair of mounting terminals  224   c , and each mounting terminal is constituted of a bottom surface terminal  226   c  and a side surface terminal  229   c . Regarding the pair of mounting terminals  224   c , the bottom surface terminal  226   c  of the −X-axis direction and the bottom surface terminal  226   c  of the +X-axis direction are formed as an identical shape. Therefore, length of the first edge  227   c  of the bottom surface terminal  226   c  in the −X-axis direction and length of the second edge  228   c  of the bottom surface terminal  226   c  in the +X-axis direction equals to the maximum width Z 2  of the short edge direction. Thus, the −X-axis direction of the package base  220  is bonded stronger than rest of the part of the package base  220   c  since the maximum width Z 2  of each bottom surface terminal  226   c  is formed on the −X-axis edge. Since the piezoelectric vibrating piece  130  (see  FIG. 2A ) is bonded to the connecting terminal  123  on the −X-axis side of the package base  220   c , the center of the piezoelectric device leans toward the −X-axis direction to a certain degree. Also, the vibration generated in the piezoelectric vibrating piece  130  reaches to the −X-axis edge of the package base  220   c  through the electrically conductive adhesive  141 . In some cases, the package base  220   c  is preferred to be bonded stronger to the −X-axis side of the printed substrate  160 . The package base  220   c  can be used effective in such case. 
     Third Embodiment 
     In the third embodiment, the package bases, comprising mounting terminals including a first rectangular profile and a second rectangular profile, are explained. The first rectangular profile and the second rectangular profile have different widths in the short edge direction, and respective rectangular profiles are combined together to form a mounting terminal as shown in  FIGS. 5A-5C . 
       FIG. 5A  is a plan view of the package base  320   a . The package base  320   c  comprises a pair of mounting terminals  324   a , and each mounting terminal is constituted of a bottom surface terminal  326   a  and the side surface terminal  329   a . The bottom surface terminal  326   a  of the package base  320   a  is formed by joining two rectangular profiles. Two rectangular profiles are denoted as a first rectangular profile  351   a  and a second rectangular profile  352   a , respectively. Each bottom surface terminal  326   a  situated on the package base  320   a  comprises the respective first edges  327   a  for forming the first profile  351   a  and the respective second edges  328   a  for forming the second profile  352   a . Also, when an edge of the first rectangular profile  351   a  opposing the first edge  327   a  is denoted as a third edge  357   a , and the edge of the second rectangular profile  352   a  facing the second edge  352   a  is denoted as a fourth edge  358   a , the bottom surface terminal  326   a  of the mounting terminal  324   a  and a fourth edge  358   a  overlap with each other. In the package base  320   a , the second edge  328   a  is formed as the maximum width Z 2  in the short edge direction. By forming the width of the first rectangular profile  351   a  in the short edge direction less than the width of the second rectangular profile, the amount of electrode materials can be reduced, and the area for bonding the solder  143  can be acquired by forming the width of the second rectangular profile  352   a  in the short edge direction at the maximum width Z 2 . 
       FIG. 5B  is a plan view of the package base  320   b . The package base  320   b  comprises a pair of mounting terminals  324   b , and each mounting terminal is constituted of a respective bottom surface terminal  326   b  and side surface terminal  329   b . The bottom surface terminal  326   b  of each mounting surface terminal  324   b  situated on the bottom surface of the package base  320   b  is formed by combining the first rectangular profile  351   b  and the second rectangular profile  352   b . The first rectangular profiles  351   b  of each bottom surface terminal  326   b  comprise the first edges  327   b , which constitutes one edge of the first rectangular profile  351   b  and connects to the side surface terminal  329   b , and third edges  357   b  opposing the respective first edges  327   b . The second rectangular profiles  352   b  of each bottom surface terminal  326   b  comprise the second edges  328   b  and the fourth edges  358   b  opposing the respective second edges  328   b  as their edges. Also, each bottom surface terminal  326   b  is formed by overlapping of the third edge  357   b  and the fourth edge  358   b . On the package base  320   a , the amount of electrode materials can be reduced by forming width of the second rectangular profile  351   b  narrow, and the area for bonding the solder  143  can be obtained by creating width of the first rectangular profile  351   b  in the short edge direction as the maximum width Z 2 . Also, formation of the solder  143  can be visually checked by forming the width of the first edge  327   b  as the maximum width Z 2  and forming the width of the side surface electrode  329   b  in the Z′-axis direction as Z 2 . 
       FIG. 5C  is a plan view of the package base  320   c . A pair of mounting terminals  324   c  constituted of respective bottom surface terminal  326   c  and side surface terminal  329   c  is formed on the package base  320   c.    
     The bottom surface terminal  326   c  of each mounting surface terminal  324   c  formed on the bottom surface of the package base  320   c  is formed by combining the first rectangular profile  351   c  and the second rectangular profile  352   c . The bottom surface terminal  326   c  situated on the −X-axis direction comprises a first edge  327   c , which constitutes one edge of the first rectangular profile  351   c  and connects to the side surface terminal  329   c  situated on the −X-axis direction, and a third edge  357   c  opposing the first edge  327   c . The bottom surface terminal  326   c  also comprises a second edge  328   c , which constitutes one edge of the second rectangular profile  352   c , and a fourth edge  358   c  opposing the second edge  328   c . Also, the bottom surface terminal  326   c  situated on the +X-axis direction comprises a first edge  327   c , which constitutes one edge of the second rectangular profile  352   c  and connects to the side surface terminal  329   c  on the +X-axis direction, and a third edge  357   c  opposing the first edge  327   c . The bottom surface terminal  326   c  also comprises a second edge  328   c , which constitutes one edge of the first rectangular profile  351   c , and a fourth edge  358   c  opposing the second edge  328   c . Also, each bottom surface terminal  326   c  is formed by overlapping of the third edge  357   c  and the fourth edge  358   c . Thus, the bottom surface terminal  326   c  situated on the −X-axis direction and the bottom surface terminal  326   c  situated on the +X-axis direction have similar profiles, the first edge  327   c  on the bottom surface terminal  326   c  on the −X-axis direction and the second edge  328   c  on the bottom surface terminal  326   c  on the +X-axis direction have same length, and the second edge  328   c  of the bottom surface terminal  326   c  on the −X-axis direction and the first edge  327   c  on the second surface terminal  326   c  on the +X-axis direction have the same length. On the package base  320   c , the bottom surface terminal  326   c  in the −X-axis direction tends to be bonded stronger, since the maximum width Z 2  of each bottom surface terminal  326   c  in the short edge direction is situated on the −X-axis direction. Thus, the package base  320   c  can be used effectively whenever the −X-axis direction is preferred to be bonded stronger to the printed substrate  160 . 
     Fourth Embodiment 
     In the fourth embodiment, the package bases are explained comprising mounting terminals having the maximum width Z 2  on different positions than the first edge or the second edge. 
       FIG. 6A  is a plan view of the package base  420   a . On the package base  420   a , a pair of mounting terminals  424   a  is situated, and each mounting terminal  424   a  is constituted of respective bottom surface terminal  426   a  and the side surface terminal  429   a . The bottom surface terminal  426   a  of each mounting terminal  424   a  formed on the bottom surface of the package base  420   a  comprises a first edge  427   a  and a second edge  428   a . Also, the maximum width Z 2  of the bottom surface terminals  426   a  in the short edge direction is situated at a different position than the first edge  427   a  or the second edge  428   a . On the package base  420   a , amount of the electrode materials can be reduced since the area of the mounting terminal  424   a  is small. Also, the area for soldering can be acquired by obtaining the maximum width Z 2  of the bottom surface terminal  426   a  in the short edge direction. Also, by displacing positions of the maximum width Z 2  in the short edge direction toward the −X-axis or +X-axis directions, the position for forming the strongest bonding to the printed substrate  160  of the package base  420   a  can be adjusted. 
       FIG. 6B  is a plan view of the package base  420   b . The package base  420   b  comprises a pair of mounting terminals  424   b , and each mounting terminal  424   b  is constituted of the bottom surface terminal  426   b  and the side surface terminal  429   b . The bottom surface terminal  426   b  situated on each mounting terminal  424   b  of the bottom surface of the package base  420   b  includes the first edge  427   b  and the second edge  428   b . Also, respective rectangular profile regions  450  are formed on the bottom surface terminal  426   b , in which the maximum width Z 2  is formed at a different position than the first edge  427   b  or the second edge  428   b . On the package base  420   b , the amount of electrode materials can be reduced since the area of the mounting terminal  424   b  is formed small. Also, the area for forming the solder  143  can be acquired by obtaining a rectangular region  450  having the maximum width Z 2  of the bottom surface terminal  426   b  in the short edge direction. Also, by displacing positions of the rectangular region  450  toward the −X-axis or +X-axis directions, the position for forming the strongest bonding to the printed substrate  160  of the package base  420   b  can be adjusted. 
     Although length of the first edge and the second edge are shown as same length in the package base  420   a  and  420   b , the length of the first edge or the second edge can be different. Also, although the mounting terminal on the −X-axis and the mounting terminal on the +X-axis are formed symmetrical to the straight line AX 2  that passes through the centerline of the package base and is parallel to the short edge, it does not need to be symmetrical as shown in  FIG. 4C . 
     Fifth Embodiment 
     In the fifth embodiment, the package bases having mounting terminals are explained. The mounting terminals comprise the respective first points, which are situated closest to the other mounting terminal, and the second points and third points are situated on both edges of the mounting terminal at the maximum width in the short edge direction. An outer periphery of the mounting terminals is connected either by respective straight lines or by respective curved lines. Each straight line connects between the first point and the second point, and between the first point and the third point, and each curved line connects the second point and the third point by passing through the first point. 
       FIG. 7A  is a plan view of a package base  520   a . The package base  520   a  comprises a pair of mounting terminals  524   a , each mounting terminal  524   a  is constituted of the bottom surface terminal  526   a  and the side surface terminal  529   a . The bottom surface terminal  526   a  of each mounting terminal  524   a  formed on the bottom surface of the package base  520   a  comprises respective first points  551   a  situated in a closest position to the other bottom surface terminal  526   a , respective second points  552   a  and respective third points  553   a  situated on both edge portions of the maximum width Z 2  of the bottom surface terminal  526   a  along the short edge direction. Thus, two first points  551   a  of each bottom surface terminal  526   a  are separated by a distance X 3 . Also an outer periphery of the bottom surface terminal  526   a  includes the first point  551   a  that is connected to both second point  552   a  and third point  553   a . Regarding the package base  520   a , the amount of electrode materials is reduced although the distance X 3  between each bottom surface electrodes  526   a  and the maximum width Z 2  in the short edge direction are maintained. 
       FIG. 7B  is a plan view of the package base  520   b . The package base  520   b  comprises a pair of mounting terminals  524   b  constituted of the respective bottom surface terminals  526   b  and the respective side surface terminals  529   b . The bottom surface terminals  526   b  of each mounting terminal  524   b  situated on the bottom surface of the package base  520   b  comprises the respective first points  551   b  situated in a closest position to the other bottom surface terminal  526   b , the second points  552   b  and the third points  553   b  formed on both edge portions at the maximum width Z 2  of the bottom surface terminal  526   b  along the short edge direction. Thus, two first points  551   b  of each bottom surface terminals  526   b  are separated by a distance X 3 . Also, on the outer periphery of the bottom surface terminal  526   b , the second point  552   b  and the third point  553   b  are connected by a curved line passing through the first point  551  in arch manner. Regarding the package base  520   b , the amount of electrode materials is reduced although the distance X 3  between each bottom surface electrodes  526   a  and the maximum width Z 2  in the short edge direction are maintained. 
     Sixth Embodiment 
     In the sixth embodiment, a package base including mounting terminals having the maximum width Z 2  formed on the first edge and the second edge, and at least one width of the other regions in the short edge direction is formed smaller than the maximum width Z 2 . 
       FIG. 8A  is a plan view of the package base  620   a . The package base  620   a  comprises a pair of mounting terminals  624   a  constituted of the respective bottom surface terminals  626   a  and the respective side surface terminals  629   a . Each bottom surface terminal  626   a  comprises respective first edges  627   a  and respective second edges  628   a , and the width of each edge is the maximum width Z 2  in the short edge direction. Also, between respective first edges  627   a  and second edges  628   a , rectangular regions  650   a  are formed having shorter width in the short edge direction than the maximum width Z 2 . The bottom surface terminals  626   a  of the package base  620   a  have a small area, and thus reduce the amount of electrode materials. Also, by obtaining a large width of the first edge  627   a  and the second edge  628   a  where the cracks are likely to occur, the bonding strength of the solder around the first edge  627   a  and the second edge  628   a  can be strengthened, and thus increases resistance against cracks. 
       FIG. 8B  is a plan view of the package base  620   b . The package base  620   b  comprises a pair of mounting terminals  624   b  constituted of the respective bottom surface terminals  626   b  and the respective side surface terminals  629   b . Each bottom surface terminal  626   b  comprises the respective first edges  627   b  and the respective second edges  628   b , and the width of each edge is the maximum width Z 2  of the mounting terminals in the short edge direction. Also, between respective first edges  627   b  and second edges  628   b , rectangular regions  650   b  are formed having shorter width in the short edge direction than the maximum width Z 2 . The bottom surface terminals  626   b  of the package base  620   b  have small area, and thus reduce the amount of electrode materials. Also, by obtaining a large width of the first edge  627   b  and the second edge  628   b , the bonding strength of the solder around the first edge  627   b  and the second edge  628   b  can be strengthened, and thus increases resistance against cracks. 
     INDUSTRIAL APPLICABILITY 
     As mentioned above, although optimal embodiments of the present disclosure were explained in detail, it will be understood by a person skilled in the art that the disclosure encompasses various alterations and modifications to the embodiments, within the technical scope of the disclosure. 
     For example, although embodiments were explained using an AT-cut quartz-crystal material as an example of the piezoelectric vibrating piece, it will be understood that the embodiments can be applied with equal facility to BT-cut piezoelectric material that vibrates in a thickness-shear mode. Also, the embodiments can be applied with equal facility to tuning-fork type quartz-crystal vibrating piece. Further, the piezoelectric vibrating piece can be made with equal facility of other piezoelectric materials such as lithium tantalite, lithium niobate, and piezoelectric materials comprising the piezoelectric ceramics. 
     Also, although the embodiments were explained based on the piezoelectric device in which the package base and the package lid are stacked together, the embodiments can be applied with equal facility to the piezoelectric vibrating piece stacked together in three-pieces, having a vibrating portion comprising an excitation electrode and a frame portion surrounding the vibrating portion, and is bonded to both principal surfaces of the frame portion of the piezoelectric device.