Electronic component and manufacturing method for the same

An electronic component includes a piezoelectric element and at least a pair of lead terminals having cup-shaped holder portions attached to hold both ends of the piezoelectric element. The cup-shaped holder portions and the electrodes disposed at both end portions of the piezoelectric element are electrically and mechanically connected by a conductive joining material. The lead terminals are made of a conductive wire, and one end portion of the lead terminals is bent outwards at an angle of about 90 degrees and flat portions are defined by press extending the portions on the tip side from the bending points that extend substantially parallel to the lead portions, and the cup-shaped holder portions are formed by bending the flat portions inwards.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 show one example of an electronic component including lead terminals according to a preferred embodiment of the present invention. This electronic component is preferably a resonator including a built-in capacitor to be used in, for example, a Colpitts oscillator circuit, and preferably includes a piezoelectric element 1 , a capacitor element 2 , and three lead terminals 10 , 11 , and 12 and has a construction where these elements are integrally sealed with a packaging resin 6 . The piezoelectric element 1 is preferably an energy trap thickness shear vibration mode element, which includes a strip-shaped piezoelectric ceramic substrate, an electrode arranged to extend to the middle portion from one end side of the front surface of the substrate, and an electrode arranged to extend to the middle portion from the other end of the back surface of the substrate, and in which both electrodes face each other with the piezoelectric substrate located therebetween in the middle portion. In the capacitor element 2 , a pair of electrodes are disposed at both end portions in the length direction on one main surface of a dielectric substrate made of a material such as ceramics, or other suitable material, and an electrode partially facing the above electrodes is disposed in the middle portion in the length direction on the other main surface. The piezoelectric element 1 and the capacitor element 2 have a publicly known construction, respectively, as described in, for example, Japanese Examined Patent Application Publication No. 5-33847, and the detailed description thereof is omitted here. As shown in FIG. 3 , the lead terminals 10 , 11 , and 12 are preferably made of a conductive wire. Here, a round lead wire of about 0.48 mm in diameter, that is, a wire preferably made of a low-carbon steel on the surface of which copper is plated and molten solder is further plated, is preferably used. The tip portion of the lead terminals 10 and 12 on both sides is bent outwards at an angle of about 90 degrees, flat portions are formed by press extending the portions on the tip side from the bending points extended substantially parallel to the lead portions 10 a and 12 a , and cup-shaped holder portions 10 b and 12 b are formed by bending these flat portions inwards. The width of the above flat portions is preferably about 0.8 to about 1.0 mm and the thickness is preferably about 0.15 to about 0.2 mm. Furthermore, the lead terminal 11 in the middle is bent so as to have a step-like configuration (in the side direction) in the transverse direction of the electronic component, and a flat portion 11 c is formed by press extending the tip of the bent portion 11 b such that the flat portion 11 c extends upwards. In the middle portions 10 a and 12 a of the lead terminals 10 and 12 on both sides, bent stopper portions 10 c and 12 c are provided to control the stop position when the terminals 10 , 12 are inserted into a circuit board. Furthermore, slightly rolled portions 10 d and 12 d are formed in the portions on the tip side from the stopper portions 10 c and 12 c , that is, in the portions constituting the upper end portion of the lead portions 10 a to 12 a and to be covered by the packaging resin 6 . These portions 10 d to 12 d are provided in order to prevent solder and soldering flax from entering the inside of the packaging resin 6 when the electronic component is mounted. As clearly understood from the side view in FIG. 3 , bending portions 10 e and 12 e bent in the same direction as the bending portion 11 b of the lead wire 11 in the middle are provided at the locations right before the cup-shaped holder portions 10 b and 12 b of the lead terminals 10 and 12 on both sides. Because of the bending portions 10 e and 12 e , the piezoelectric element 1 held by the cup-shaped holding portions 10 b and 12 b is located very close to the lead terminal 11 in the middle and the bottom surface of the piezoelectric element 1 is supported by the bending portion 11 b of the lead terminal 11 . In the same way, the bottom surface of the capacitor element 2 is also supported by the bending portion 11 b of the lead terminal 11 in the middle. Therefore, in the stage before soldering, the position of the piezoelectric element 1 and the capacitor element 2 is positionally stabilized and soldering is made easy. Both end portions of the piezoelectric element 1 are held by the cup-shaped holder portions 10 b and 12 b of the lead terminals 10 and 12 , the piezoelectric element 1 is mechanically fixed by pouring a conductive joining material such as solder into the cup-shaped holder portions 10 b and 12 b , and the electrodes located at both end portions of the piezoelectric element 1 are simultaneously electrically connected to the cup-shaped holder portions 10 b and 12 b. The capacitor element 2 is held between the cup-shaped holder portions 10 b and 12 b and the tip portion 11 b of the lead terminal 11 in the middle and is electrically and mechanically connected to the holder portions 10 b and 12 b by the above-mentioned conductive joining materials 3 and 4 and is also connected to the lead terminal 11 by another conductive joining material 5 . After the piezoelectric element 1 and the capacitor element 2 are fixed to the three lead terminals 10 to 12 , the vibrating portion (central portion) of the piezoelectric element 1 is preferably coated with wax and its surroundings are coated with the packaging resin 6 , and then a cavity 7 is defined to surround the vibrating portion of the piezoelectric element 1 by causing the wax to be absorbed when the packaging resin 6 is hardened. As shown in FIG. 3, a plurality of groups of the lead portions 10 a to 12 a of the lead terminals 10 and 12 as a set of three is welded and fixed to a long hoop material with a fixed distance therebetween. When the manufacture of the electronic component is finished, the lead terminals 10 and 12 are separated from the hoop material, but during a series of processes such as forming the lead terminals 10 to 12 , soldering the piezoelectric element 1 and the capacitor element 2 , coating of wax, sealing by the packaging resin, and other processes, the lead terminals 10 and 12 are transported in the manufacturing line while they are fixed to the hoop material 13 . At that time, pilot holes 14 are formed in the hoop material 13 with a fixed distance therebetween in order to position the hoop material correctly. Next, one example of a method for forming the lead terminals 10 and 12 shown in FIG. 3 is described based on FIGS. 4 and 5 . FIG. 4 is a flow chart for forming lead terminals by using dies, and FIG. 5 shows the change of shape of the lead terminals. In FIGS. 4 and 5 , A shows a process for preparing a pair of lead wires 10 A and 12 A. Here, a lead wire having a substantially square section is used, but a substantially round lead wire may be used. B shows a process for bending the tip portion of the lead wires 10 A and 12 A outwards at an angle of about 90 degrees by using supporting dies 20 and bending dies 21 . C shows a process for forming flat portions 10 f and 12 f by press extending the portions including the bending point on the tip side of the lead wires 10 A and 12 A which are bent at an angle of about 90 degrees, so as to be extended substantially parallel to the lead portions 10 a and 12 a using a pair of press extending dies 22 and 23 . D shows a process for bending the rolled flat portions 10 f and 12 f at an angle of about 90 degrees towards the thickness direction at the location about one third away from the tip of the flat portions 10 f and 12 f by using bending dies 26 while the rolled flat portions 10 f and 12 f are held between a pair of dies 24 and 25 . E shows a process for bending the flat portions 10 f and 12 f at an angle of about 45 degrees towards the thickness direction at the location about two thirds away from the tip of the flat portions 10 f and 12 f by bending dies 29 while the flat portions 10 f and 12 f are held between a pair of dies 27 and 28 . Through the above processes, as shown in E of FIG. 5 , the cup-shaped holder portions 10 b and 12 b facing each other are disposed at the tip portions of a pair of the lead terminals 10 and 12 . When the holder portions 10 b and 12 b are formed by bending the flat portions 10 e and 12 e in the thickness direction twice as described above, the number of processes is reduced and the dies also become simple. In the above-described preferred embodiment, an electronic component in which a piezoelectric element and a capacitor element are fixed to three lead terminals is described, but an electronic component in which a piezoelectric element is fixed between two lead terminals and no capacitor element is provided may also be produced. Furthermore, regarding the lead terminals, each respective one end portion is bent outwards at an angle of about 90 degrees and the flat portion is formed by press extending the portion including the bending point on the tip side, but the flat portion may be formed by the portion excluding the bending point on the tip side. Moreover, the sequence for forming the lead terminals is not limited to that shown in FIGS. 4 and 5 , and after the tip portion of the lead wires is rolled flat, the lead wires are bent outwards at an angle of about 90 degrees at the portion which is not rolled and then the flat portion may be formed to be cup-shaped. As clearly understood from the above description, according to the first preferred embodiment of the present invention, the cup-shaped holder portions are preferably formed by using a conductive wire material and the holder portions have a configuration that encloses the end portions of a piezoelectric element. Therefore, when compared with lead wires with a V-shaped receiving groove, the holder portions have an excellent holding function for the piezoelectric element and it is easy to apply solder inside. As a result, the reliability of conductivity to the electrodes of the piezoelectric element is greatly increased. Furthermore, even if the piezoelectric element has a different width and thickness, since the inner width and depth of the cup-shaped holder portions can be freely changed by simply changing the bending location of the lead wires, the cup-shaped holder portions can be applied to various types of piezoelectric elements resulting in low cost. Furthermore, when compared with pressed terminals prepared by stamping dies, since the lead terminal itself is made of a single lead wire, the material loss is extremely low. Moreover, since the lead terminal is made of a lead wire, it is easily cut in an automatic insertion machine and the life of the cutting edge can be greatly prolonged. Furthermore, when a manufacturing method according to a second preferred embodiment of the present invention is used, an electronic component according to the first preferred embodiment of the present invention can be manufactured simply and at low cost. While preferred embodiments of the invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.