1. Field of the Invention
The present invention relates to an apparatus, such as a piezoelectric resonance device, having an electronic component located on a surface of a package member with a space provided between the electronic component and the package member.
2. Description of the Related Art
Some electronic devices require that a portion thereof does not contact a printed circuit board or substrate when mounted on the printed circuit board or substrate or the like. For instance, in a piezoelectric resonator, a resonating section thereof must be arranged such that a sufficient space between the resonating section and the printed circuit substrate is provided in order to prevent interference with the oscillation of the resonating section. In case of an exothermic electronic component, it is necessary to mount the electronic component such that a sufficient space between the printed circuit board or substrate and the component is provided in order to prevent heat from conducting to the printed circuit board or substrate and other nearby elements.
Various structures have been proposed for a piezoelectric resonator in order to create such a space.
FIG. 17 is a partially cutaway section view showing one example of a prior art structure for mounting a piezoelectric resonator.
As seen in FIG. 17, electrode lands 52a and 52b are located on a substrate 51. A piezoelectric resonator 53 is mounted in contact with the electrode lands 52a and 52b. The piezoelectric resonator 53 has a structure in which a terminal electrode 53b is located at one end of a piezoelectric plate 53a and a terminal electrode 53c is located at the other end. It is noted that a resonance electrode not shown is connected to the terminal electrodes 53b and 53c. 
The terminal electrodes 53b and 53c are connected to the electrode lands 52a and 52b via conductive adhesives 54a and 54b applied so as to have a certain thickness to prevent interference with the oscillation of a resonating section of the resonator 53.
That is, a gap 55 is created between the piezoelectric resonator 53 and an upper surface 51a of the substrate 51 by increasing a thickness of the conductive adhesives 54a and 54b. 
However, because the conductive adhesives 54a and 54b are liquid when they are applied, the conductive adhesive material is liable to flow along the upper surface 51a toward the center of the piezoelectric resonator 53 as shown by arrows A1 and A2 in FIG. 17. As a result, the resonating section is joined to the upper surface 51a of the substrate 51 via the conductive adhesive in the mounting structure, thereby degrading the resonating characteristics of the resonator 53. In addition, because the conductive adhesives 54a, 54b flow and extend along the upper surface 51a, the vertical dimension of the gap 55 is reduced and cannot be accurately or reliably provided.
Further, because the liquid conductive adhesives 54a and 54b are hardened after the application, the size and vertical dimension of the space 55 varies. Often, the resonating section of the resonator 53 contacts the upper surface 51a of the substrate 51, thereby damaging the resonating characteristics of the resonator 53.
In order to eliminate the aforementioned problems, there has been proposed a mounting structure in which spacers 56a and 56b are interposed between the terminal electrodes 53b and 53c and the electrode lands 52a and 52b as shown in FIG. 18. The spacers 56a and 56b are made of an electrically conductive material such as metal and are joined to the terminal electrodes 53b and 53c as well as the electrode lands 52a and 52b via conductive adhesive or solder. A space 55A is defined between the piezoelectric resonator 53 and the upper surface 51a of the substrate 51 by the vertical dimension of the spacers 56a and 56b. 
However, this structure requires preparation of spacers 56a and 56b having a very accurate size and shape and also requires a difficult and time-consuming process of applying the spacers 56a and 56b to mount the piezoelectric resonator 53.
Meanwhile, there has been disclosed a small package structure for storing a piezoelectric resonator and the like in Japanese Patent Laid-Open No. Hei. 5-83074. FIGS. 19a and 19b are a partially cutaway plan view and a section view, respectively, showing the package structure of this prior art device.
The electronic component 61 includes an insulating substrate 62 and a cap 63. A piezoelectric resonator 64 is stored within the package. Further, through hole electrodes 65a-65c are formed so as to extend through the substrate 62. The through hole electrodes 65a-65c are constructed by creating through holes extending through the substrate 62 and by applying an electrode material on the inner peripheral surfaces of the through holes. The inner peripheral surfaces of the through holes and the electrodes extend to the upper and lower surfaces so as to form flange-like portions.
The piezoelectric resonator 64 is joined to the through hole electrodes 65a-65c via conductive adhesives 66a-66c. The conductive adhesives 66a-66c are disposed in the through hole electrodes 65a-65c and are joined to the flange-like portion at the upper surface of the substrate 62 of the through hole electrodes 65a-65c. 
It is thought that the electronic component 61 allows an area outside of the cap 63 to be reduced so that the device can be miniaturized because the piezoelectric resonator 64 is led to the outside via the through hole electrodes 65a-65c. 
However, because the piezoelectric resonator 64 is joined to the through hole electrodes 65a-65c via the conductive adhesives 66a-66c in the electronic component 61, oscillation of the resonating section is damaged by the conductive adhesives 66a-66c which flow and spread during application thereof similar to the case of the mounting structure 51 shown in FIG. 17. In addition, similar to the prior art device shown in FIG. 17, the prior art device in FIG. 19(b) experiences a problem of not being able to reliably provide an accurate vertical dimension of the gap between the resonator 64 and the substrate 62, which problem is caused by the upper portions of the electrodes 65a-65c and the adhesives 66a-66c extending along and spreading out along the upper surface of the substrate 62.
As described above, there have been problems with degrading resonance characteristics caused by the mounting structure 51 shown in FIG. 17 and by the electronic component 61 shown in FIG. 19 because the space having a sufficient size or vertical dimension cannot be reliably provided due to the fluidity and spreading of the conductive adhesive.
Further, the mounting structure shown in FIG. 18 has had problems with the manufacturing and assembly process being complicated and costly because the spacers 56a and 56b have to be used.
To overcome the problems described above, the preferred embodiments of the present invention provide an apparatus including an electronic component which is arranged and constructed to be fixed firmly to a package member with a space being reliably provided therebetween and to allow the component to be easily manufactured.
The preferred embodiments of the present invention provide an electronic component including a package member; a via hole electrode provided so as to extend through the package member and to protrude from a first surface of the package member; an electronic component located on the first surface of the package member with a space defined therebetween; the space between the electronic component and the first surface of the package member being determined by a protruding portion of the via hole electrode extending from the surface of the package member; and a joining member joining the electronic component with the via hole electrode.
It is noted that the via hole electrode described in the present specification is intended to mean a solid electrode in which an electrode material is filled completely within a through hole as described later.
It is also noted that the via hole electrode does not extend along an upper or first surface of the substrate or package member as in the prior art. Instead, the via hole electrode extends vertically upwardly from the first surface of the substrate or package.
Also, the via hole electrode is a completely solid member having a rod-shaped configuration such that the rod-shaped member extends through the via hole and has an upper, rounded portion which extends vertically from the upper surface of the substrate or package member in a direction that is substantially perpendicular to the upper surface of the substrate or package member so as to support the resonator and to provide an accurate vertical dimension of the gap between the resonator and the package member.
With the structure of the preferred embodiments of the present invention as described above, a space having a desired size or vertical dimension can be reliably provided between the electronic component and the package member. Accordingly, it becomes possible to provide an electronic component such as a piezoelectric resonator which is mounted on the package member while reliably providing a sufficient space therebetween so that oscillation of the resonating section of the resonator is not hindered.
In addition, although the desired space in the prior art devices could not be obtained due to the fluidity and spreading of the adhesive during application thereof in which the space between the electronic component and the package member is created by the conductive adhesive, a space having a sufficient vertical dimension is reliably provided in the preferred embodiments of the present invention because of the shape and arrangement of the via hole electrodes and protruding portions of the via hole electrodes. Further, because the preferred embodiments of the present invention do not require an extra member such as a spacer to create the space having the desired vertical dimension, the electronic component of the preferred embodiments of the present invention is much easier and less expensive to manufacture. In addition, the rod-shaped, solid via hole electrode filling the via holes in the substrate in the preferred embodiments of the present invention allow for significantly less adhesive to be used as compared to the prior art devices in which adhesive spread along the upper surface of the substrate and in some devices, the adhesive spread into the via holes. Thus, even if the adhesive used in the preferred embodiments of the present invention spreads along the upper surface of the substrate, the gap between the resonator and the substrate is accurately and reliably provided with an exact vertical dimension because of the rod-shaped, solid via hole electrodes.
In the above described apparatus, the electronic component may be a piezoelectric resonator.
With the structure of the preferred embodiments of the present invention, an electronic component having excellent resonance characteristics is obtained.
In the above described electronic component, the via hole electrode may be exposed at a second surface of the package member wherein the first and the second surfaces of the package member are opposed to each other.
By the above-described structure, the electronic component at the upper surface (the first surface) of the package member may be electrically connected with the lower surface (the second surface) of the package member by using the via hole electrodes. Accordingly, this arrangement allows the electronic component which can be readily mounted on the package member surface to be obtained by forming connecting electrodes and terminal electrodes on the lower surface of the package member.
In the above described electronic component, the package member may comprise a ceramic substrate and a plurality of internal electrodes may be provided in the package member so as to form at least one capacitor, and the via hole electrode may be electrically connected to the capacitor.
With the above described structure, an electronic apparatus includes a complex type package structure having a circuit in which the capacitors are connected to the electronic component mounted on the package member.
In the above described electronic component, the package member may comprise a ceramic substrate, a plurality of cutaways may be provided on a side of the ceramic substrate, and a plurality of external electrodes may be provided in the plurality of cutaways.
With the above described structure, it becomes possible to form the external electrodes readily by using the same method as that used for forming the via hole electrodes and to provide a smaller electronic component as compared to the external electrode using the through hole electrodes.
According to another preferred embodiment of the present invention, a method of forming the apparatus includes the steps of laminating a plurality of ceramic green sheets on a support film to obtain a ceramic green sheet laminate, forming through holes through the ceramic green sheet laminate at positions where via hole electrodes are to be located, applying conductive material into the through holes so as to fill the through holes and to be located on the upper surface of the ceramic green sheet laminate to form via hole electrodes, and sintering the ceramic green sheet laminate to form a substrate and so as to form protrusion portions of the via hole electrodes which protrude upward from the upper surface of the substrate.
The via hole electrodes that are formed by the above process are solid and substantially rod-shaped. The via hole electrodes formed by the above process fill the via holes with the solid, rod-shaped configuration. The protruding portions are formed because a coefficient of thermal contraction of the ceramics, during cooling after the sintering, is higher as compared to a coefficient of thermal contraction of the electrode material.
As a result of the protruding portions of the via hole electrodes, a gap having a sufficient size or vertical dimension can be reliably created below the piezoelectric resonator and the substrate.
In a further preferred embodiment, the method includes the step of setting the coefficient of thermal contraction of the ceramics to be higher than the coefficient of thermal contraction of the electrode material filled in the through holes by about 1% to about 20%. With this desired range, the size of the gap is accurately and reliably achieved.