Electronic component device and package substrate

In an electronic component device, an ESD protection element including a cavity portion and a pair of opposed discharge electrodes is disposed inside a package substrate. A composite portion made of a composite material including a metal material and an insulating material is disposed on a bottom of the cavity portion. The package substrate including the ESD protection element disposed therein reduces the size of the electronic component device and reliably prevents damage to and malfunctioning of the electronic component device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic component device and, more specifically, to an electronic component device in which an electronic component element is mounted on a package substrate that includes an ESD protection element therein. The present invention also relates to a package substrate that includes an ESD protection element therein.

2. Description of the Related Art

For an electronic component device having a precision structure and functioning with high precision, such as an IC device or a SAW device, an important issue is taking measures against electro-static discharge (ESD) and preventing damage to and malfunctioning of the electronic component device if a charged object comes into contact with or is close to the electronic component device.

Traditionally, for example, in an IC device, an IC element itself may include the ESD protection function. However, a problem arises in that it is difficult to further incorporate the ESD protection function into an IC element having high-density functions and also a problem arises in that, even when such incorporation is achieved, it is impossible to provide a sufficiently robust ESD protection function.

In an IC device disclosed in Japanese Unexamined Patent Application Publication No. 10-41458, as illustrated inFIG. 6, an ESD protection component103arranged separately from an IC element102is mounted on a substrate101. Specifically, a branch line104bis branched from a signal line104ainside the substrate101, another end of the branch line104bis extended to the surface of the substrate101, and that end is connected to the ESD protection component103.

In this IC device, for example, if an excessive voltage caused by static electricity is applied to a terminal105, the static electricity is discharged in the ESD protection component103and guided to the ground side, and thus, the IC element102is not damaged and no malfunction occurs.

However, the method described in Japanese Unexamined Patent Application Publication No. 10-41458 requires that, in addition to the IC element102, the ESD protection component103be mounted on the surface of the substrate101, and thus, the substrate101must have a relatively large surface area. This raises a problem in that the size of the IC device is increased. In addition, a problem arises in that the cost is increased because the ESD protection component103, which is a separate component, is used.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention provide, in an electronic component device, a package substrate on which an electronic component element is mounted and that includes an ESD protection element therein. Preferably, the ESD protection element includes at least a cavity portion disposed inside the package substrate and a pair of opposed discharge electrodes disposed inside the cavity portion, and the ESD protection element is located between a signal line disposed inside the package substrate and a ground electrode disposed on a surface of the package substrate.

The ESD protection element may preferably further include a composite portion disposed on a bottom of the cavity portion, the composite portion being made of a composite material including a metal material and an insulating material, the insulating material defining the package substrate, and the pair of discharge electrodes may be disposed on the composite portion. With this configuration, the thermal coefficient of expansion of the composite portion is between that of the discharged electrodes and that of the package substrate, and the difference between the thermal coefficient of expansion of the discharged electrodes and that of the package substrate can be reduced by the composite portion. Thus, separation of the discharged electrodes from the package substrate and changes in characteristics over time are prevented or minimized. In addition, adjustment of the type and quantity of the metal material included in the composite portion enables adjustment of the discharge inception voltage.

The ground electrode for the ESD protection element disposed on the surface of the package substrate may preferably be configured as a ground electrode dedicated to the ESD protection element, the ground electrode being separate from a ground electrode of the electronic component element. With this configuration, because static electricity discharged in the ESD protection element and guided to the ground side can be prevented from being delivered to the electronic component element, the advantageous effects of protecting the electronic component element against ESD are improved.

In the electronic component device of various preferred embodiments of the present invention, the ESD protection element is included inside the package substrate on which the electronic component element is mounted. Thus, unlike traditional electronic component devices, it is not necessary to mount an ESD protection component on the surface of the substrate in addition to the electronic component element, and this eliminates the need to use a substrate having a large surface area. This enables miniaturization of the electronic component device.

In addition, because an additional ESD protection component is not included or required, the cost of the electronic component device is reduced.

Moreover, because the ESD protection function is not incorporated in an electronic component element itself, such as an IC element, a sufficiently robust ESD protection function is achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments are described below with reference to the drawings.

First Preferred Embodiment

FIGS. 1 and 2illustrate an electronic component device according to a first preferred embodiment of the present invention.FIG. 1is a cross-sectional view of the electronic component device, andFIG. 2is a main-portion cross-sectional view that illustrates an ESD protection element portion of the electronic component device.

InFIGS. 1 and 2, reference numeral1represents a package substrate, and an ESD protection element2is disposed therein. The package substrate1is insulative, and a ceramic, for example, is preferably used in the package substrate1in the first preferred embodiment. Any suitable material other than a ceramic may be used in the package substrate1, such as a resin, for example.

As illustrated inFIG. 2, the ESD protection element2preferably includes a cavity portion3that is disposed inside the package substrate1, a composite portion4made of a composite material preferably including an insulating material4a(for example, ceramic in the present preferred embodiment) defining the package substrate1and a metal material4b, for example, and a pair of opposed discharge electrodes5aand5bdisposed on the composite portion4. Any suitable kind of the material may be used as the metal material4b. In the present preferred embodiment, copper, for example, is preferably used. Any material may be used for the discharge electrodes5aand5b. In the present preferred embodiment, copper, for example, is preferably used, as in the case of the metal material4b.

Because the composite portion4is preferably made of the material including the insulating material4aand the metal material4b, the composite portion4has a thermal coefficient of expansion between that of the discharge electrodes5aand5band that of the package substrate1, and thus, performs the function of reducing the difference between the thermal coefficient of expansion of the discharge electrodes5aand5band that of the package substrate1. As a result, if heat is applied during the formation of the package substrate1by firing, during mounting of a completed electronic component device on a printed circuit board of an electronic apparatus by reflow soldering, or during use of an electronic apparatus, the composite portion4reduces the occurrence of separation of the discharge electrodes5aand5bfrom the package substrate1. Accordingly, changes in characteristics, including a discharge inception voltage, over time are effectively prevented or minimized.

Adjusting the kind and quantity of the metal material4bincluded in the composite portion4enables adjustment of the discharge inception voltage. Specifically, the discharge inception voltage decreases with an increase in the conductivity of the metal material and with an increase in the quantity of the metal material.

The cavity portion3of the ESD protection element2may preferably be filled with a rare gas, such as argon or neon, for example. If such a rare gas is provided therein, the discharge inception voltage can be reduced. In the present preferred embodiment, the cavity portion3preferably is not filled with a rare gas.

In the electronic component device according to the present preferred embodiment, a signal line6, an ESD protection element ground line7, and an electronic component element ground line8are preferably disposed inside the package substrate1, and an input/output electrode9and a common ground electrode10common to the electronic component element and the ESD protection element2are preferably disposed on the lower surface of the package substrate1. The ESD protection element2is located between the signal line6and the common ground electrode10. Any suitable number of ESD protection elements2may be used depending on the necessity.

Preferably, a ground pad11and a wiring pad12are disposed on the upper surface of the package substrate1, an IC element13defining the electronic component element is mounted on the ground pad11, and the wiring pad12and the IC element13are connected by a wire bond14disposed therebetween. The upper surface of the package substrate1is preferably sealed with a sealing resin15.

If a charged object comes into contact with or comes close to the electronic component device having the above-described structure according to the present preferred embodiment and an excessive voltage caused by static electricity is applied to the signal line6, the static electricity is discharged in the ESD protection element2and transferred to the common ground electrode10, and the IC element13is not damaged and no malfunction occurs in the IC element13. Typically, the ESD protection element2is in an electrically open state and does not allow electricity to flow therethrough.

Next, a non-limiting example of a method of producing an electronic device according to the present preferred embodiment is described. One of the unique features of preferred embodiments of the present invention is that the package substrate1includes the ESD protection element2, so a method of producing the package substrate1will be described below.

The package substrate1is produced by stacking and firing of a plurality of ceramic green sheets.

First, insulating ceramic powder of a predetermined composition is mixed with a solvent, a binder, and/or other material to form a slurry, the slurry is shaped into thin films using a doctor blade, and ceramic green sheets are formed.

Copper powder having a predetermined particle diameter is mixed with a solvent, a binder, and/or other material and an electrode paste is formed.

The ceramic powder used in the ceramic green sheets and the copper powder used in the electrode paste are mixed together with a predetermined mixture ratio, the mixture is further mixed with a solvent, a binder, and/or other material, and a composite paste is formed.

Next, holes for forming via holes that are to become the signal line6, the ESD protection element ground line7, and the electronic component element ground line8are formed in the ceramic green sheets. The locations and the number of the holes vary among the ceramic green sheets. The holes in the ceramic green sheets are filled with the electrode paste.

Next, the composite paste for forming the composite portion4is applied on the ceramic green sheet on which the ESD protection element2is to be formed so as to have a predetermined shape, the electrode paste for forming the discharge electrodes5aand5bis applied thereon so as to have a predetermined shape, and a resin paste for forming the cavity portion3, the resin paste being formulated to disappear when fired, is applied on the composite paste and the electrode paste.

Then, a predetermined number of the ceramic green sheets, including the ceramic green sheet on which the ESD protection element2is to be formed and the other ceramic green sheets, are stacked in a predetermined order, the stacked ceramic green sheets are pressed and bonded, and an unfired ceramic laminate is formed.

Then, a conductive paste for forming the input/output electrode9, the common ground electrode10, the ground pad11, and the wiring pad12is applied on the upper surface and the lower surface of the ceramic laminate so as to have a predetermined shape. The conductive paste may not be applied at this stage, but alternatively, may be applied in advance to a ceramic green sheet that will be in the uppermost or lowermost position in the ceramic laminate.

Then, the ceramic laminate is fired with a predetermined profile, and the package substrate1is produced. The ESD protection element2including the cavity portion3, the composite portion4, and the discharge electrodes5aand5bis disposed inside the package substrate1. In the foregoing description, a case of producing a single package substrate1is described. Alternatively, a plurality of package substrates may be produced at a time from a large ceramic laminate. In this case, before or after firing, the large ceramic laminate is cut into pieces having the size of each package substrate.

Finally, the IC element13is mounted on the package substrate1by a widely used method, the wire bond14is applied, and the sealing resin15is formed on the upper surface of the package substrate1, on which the IC element13is mounted. In this manner, the electronic component device according to the present preferred embodiment is completed.

Second Preferred Embodiment

FIG. 3illustrates an electronic component device according to a second preferred embodiment of the present invention.FIG. 3is a cross-sectional view of the electronic component device.

In the electronic component device according to the second preferred embodiment, the common ground electrode10(seeFIG. 1) disposed on the lower surface of the package substrate1is preferably replaced with individual ground electrodes, i.e., a ground electrode20dedicated to the ESD protection element and a ground electrode21dedicated to the electronic component element. The remaining configuration is the same or substantially the same as that in the first preferred embodiment.

The electronic component device according to the second preferred embodiment prevents static electricity discharged in the ESD protection element2and guided to the ground side from being delivered to the electronic component element (IC element13). Thus, the advantageous effects of protecting the electronic component element against ESD are improved.

Third Preferred Embodiment

FIG. 4illustrates an electronic component device according to a third preferred embodiment of the present invention.FIG. 4is a cross-sectional view of the electronic component device.

In the electronic device according to the third preferred embodiment, an IC element23as the electronic component element is preferably flip-chip mounted on the ground pad11and the wiring pad12of the package substrate1using solder bumps. The remaining configuration is the same or substantially the same as that in the first preferred embodiment.

Fourth Preferred Embodiment

FIG. 5illustrates an electronic component device according to a fourth preferred embodiment of the present invention.FIG. 5is a cross-sectional view of the electronic component device.

In the electronic device according to the fourth preferred embodiment, a SAW element33as the electronic component element is preferably mounted on the package substrate1, and the wiring pad12of the package substrate1and a pad electrode33aof the SAW element33are preferably connected with a wire bond24disposed therebetween. InFIG. 5, reference numeral33brepresents an IDT electrode disposed on the surface of the SAW element33.

In the electronic device according to the fourth preferred embodiment, the upper surface of the package substrate1, on which the SAW element33is mounted, is preferably sealed not with a sealing resin but with a top cover25.

According to preferred embodiments of the present invention, even in a SAW device, in which ESD is a problem, as in the case of an IC device, the electronic component element is protected against ESD.