Electronic device

ABSTRACT

An electronic device includes a wiring substrate, an electronic component mounted on the wiring substrate by soldering, and a case fixed to the wiring substrate so as to cover the electronic component. The case is fixed to the wiring substrate via soldering, and the case and the electronic component are adhered to each other with an adhesive resin supplied through an opening provided in the upper surface of the case. The adhesive resin is applied so as not to contact the wiring substrate such that interface separation does not occur between the adhesive resin and the wiring substrate even when the solder for mounting the electronic component on the wiring substrate is melted and expanded in a solder reflow process. As a result, the generation of short circuiting between terminal electrodes of the electronic component, which is caused by the solder flowing in the portion of the interface separation, is prevented.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a perspective view showing an electronic device of a first preferred embodiment according to the present invention, and FIG. 2 is a cross-sectional view taken along the line II—II in FIG. .

The electronic device shown in FIG. 1 is used, for example, as a high-frequency electronic device such as an RF device in a mobile phone or a wireless communication device.

The electronic device includes a wiring substrate . Although not shown in detail in FIG. 1, the wiring substrate is, for example, a multilayer ceramic electronic substrate including passive elements, such as capacitors, inductors, resistors, filters, and delay lines, and wire conductors. As shown in FIG. 1, on the end surfaces at the periphery of the wiring substrate , several terminal electrodes are provided, and on the top surface of the wiring substrate , several conductive lands and are provided.

On the top surface of the wiring substrate , several surface mount electronic components , , , and are mounted via soldering. Among the electronic components mounted on the wiring substrate , only the typical components are shown in the figure.

The electronic component shown in FIG. 2 is an IC chip component, such as a radio frequency IC (RFIC), a baseband (BB) IC, or a memory, and is soldered to the wiring substrate via several solder bumps . In addition, the electronic components and shown in FIG. and the electronic component shown in FIG. 2 are surface mount chip components, such as capacitors, inductors, or quartz oscillators. In FIGS. 1 and 2, solder fillets used for soldering these electronic components to are shown.

In addition, on the bottom surface of the wiring substrate , electronic components may be mounted whenever necessary. In this case, in the bottom surface of the wiring substrate , a cavity (recess portion) is provided, and the electronic components may be mounted in the cavity.

A case is fixed to the wiring substrate so as to cover the electronic components to described above. The case is made of metal. In this preferred embodiment, the case is preferably formed by processing a metal plate and includes a top wall , four sidewalls , and four foot-portions . Notches and are provided at both sides of each of the foot-portions and are used to facilitate forming the foot-portions .

The foot-portions of the case are used for fixing the case to the wiring substrate . That is, the foot-portions are soldered to the conductive lands provided on the wiring substrate with solder , and hence the case is fixed to the wiring substrate .

The sidewalls of the case are each configured such that the height thereof does not reach the upper surface of the wiring substrate . In particular, as shown in FIG. 2, when the electronic component is disposed between the sidewalls and the wiring substrate , each of the sidewalls and the electronic component have a space provided therebetween. The reasons for this are as follows.

When the foot-portions of the case are soldered to the conductive lands with the solder by a reflow solder process, the solder is melted in the reflow solder process, and as a result, the case may move along the surface of the wiring substrate . When the space is not provided, the sidewall and the electronic component are brought into contact with each other. When the solder is solidified such that the case is fixed to the wiring substrate , the electronic component may be scratched, and breakage or chipping thereof may occur. In addition, when the case is placed on the electronic component , the soldering strength between the case and the wiring substrate may be decreased. The space prevents the problems described above.

When the electronic device is a high-frequency device, the dimensions and shape of the sidewall , and in particular, the dimension of the space is designed such that electromagnetic waves in currently used frequency bands will not leak, and such that sufficient shielding properties are ensured.

Furthermore, in the electronic device , as shown in FIG. 2, the electronic component and the case are adhered to each other with an adhesive resin . As shown in FIG. 2 the adhesive resin is applied, for example, onto only the top surface of the electronic component , so as not to reach the wiring substrate . In this step, as long as the adhesive resin does not reach the wiring substrate , the adhesive resin may be applied so as to extend onto the side surfaces of the electronic component .

The adhesive resin is applied after the electronic components to are mounted on the wiring substrate and after the case is fixed thereto. Hence, in the top wall of the case , an opening is provided for easily supplying the adhesive resin from the outside. Accordingly, the adhesive resin is supplied in an uncured state in the case through the opening , for example, by a dispenser. As the adhesive resin , a thermosetting resin such as an epoxy resin is used and is cured by heating. The viscosity of the adhesive resin in an uncured state is selected such that the adhesive resin easily flows through the relatively small opening and spreads along the top surface of the electronic component , but does not flow down along the side surfaces thereof.

As the adhesive resin described above, for example, a material having the following composition and properties (viscosity and thixotropic index) is preferably used.

(Composition)

As shown in FIG. 2, the opening is preferably sealed with the adhesive resin . This prevents foreign materials from intruding into the case through the opening .

In addition, the opening is preferably provided at a position spaced from the center of the top wall of the case toward the peripheral side thereof. Hence, an area in which marking of a tradename or other suitable mark is performed, for example, by laser is provided on the top wall of the case .

In addition, by providing the opening at a position other than the center of the top wall , this opening can be used as a mark indicating the directionality of the electronic device . In this case, when the adhesive resin includes a pigment such as carbon, the opening is colored in black or other suitable color by the adhesive resin , the difference in color tone between the opening and the adhesive resin is more visible.

In this preferred embodiment, under the opening , the electronic component is preferably provided. However, it is not necessary that the center of the top surface of the electronic component be aligned with the opening , and even when the electronic component is mounted on the center of the wiring substrate , the arrangement of which is different from that shown in the figure, the position of the opening is preferably shifted from the center of the top wall .

In addition, when the electronic component is an IC chip component, resin packaging is generally performed thereon. When the electronic component has a top surface including at least a resin portion, as described above, since the adhesive resin is applied to this resin portion for adhesion, the adhesion strength between the adhesive resin and the electronic component is further improved.

As shown in the FIG. 1, when a plurality of electronic components, i.e., the electronic components to , is mounted on the wiring substrate , and the areas of the top surfaces of the electronic components to are different from each other, the adhesive resin is preferably applied on the top surface of the electronic component having the largest top surface area. As a result, the adhesive resin is less likely to flow down along the side surfaces of the electronic component .

In addition, as shown in the FIG. 1, when the plurality of the electronic components to have different heights, the adhesive resin is preferably applied to the top surface of the electronic component having the greatest height. As a result, even when the amount of adhesive resin is small, the electronic component and the case are securely adhered to each other. In addition, when the amount of the adhesive resin is reduced, the adhesive resin is less likely to flow down along the side surfaces of the electronic component .

As described above, according to the first preferred embodiment described with reference to FIGS. 1 and 2, by adhering the electronic component and the case to each other with the adhesive resin , the fixing strength of the case to the wiring substrate is greatly improved. Accordingly, the case is much less likely to fall off of the wiring substrate , due to impact caused by, for example, dropping a product provided with this electronic device .

In addition, by providing the adhesive resin , the gaps between the case and the electronic component and the wiring substrate are maintained constant, and for example, in a property inspection step and selection step for the electronic device , and in a step of mounting and soldering the electronic device onto a mounting substrate such as a motherboard, variations of the gaps are minimized and prevented, thereby preventing variations in the properties of the electronic device .

Since the adhesive resin does not contact the wiring substrate , when this electronic device is mounted on an appropriate motherboard by a solder reflow process or other suitable soldering method, the movement of melted solder generated when the solder bumps are remelted is not restricted by the adhesive resin , and as a result, electrical short circuiting generated between different terminals of the electronic component , which is caused by the restriction of the movement of the solder as described above, is prevented.

In addition, fixing of the case to the wiring substrate is performed by the adhesive resin adhering the electronic component to the case and by the solder bonding the foot-portions to the wiring substrate . Accordingly, even when the bonding strength between the foot-portions and the wiring substrate is decreased, since a fixing strength equal to or greater than a predetermined strength is ensured for the case , the areas of the bonding portion between the foot-portions and the conductive lands are decreased. As a result, the area at which circuit elements other than the conductive lands are disposed is increased, and hence miniaturization of the electronic device is achieved.

In addition, since the opening is provided in the case , after the electronic components to are mounted on the wiring substrate , and the case is fixed thereto, the adhesive resin is applied. Accordingly, before a step of applying the adhesive resin , when the electronic device is rejected as defective, the expensive electronic component , such as an IC chip component, can be removed from the wiring substrate for reuse.

FIG. 3 is a view showing an electronic device la of a second preferred embodiment according to the present invention and is a view corresponding to that in FIG. . In FIG. 3, the same reference numerals of the elements in FIG. 2 designate the equivalent elements, and descriptions thereof are omitted.

In FIG. 3, two electronic components and are mounted on the wiring substrate . The electronic components and are, for example, surface-mounted chip components, such as capacitors, inductors, or quartz oscillators. Solder fillets shown in FIG. 3 are used to solder the electronic component and to the conductive lands provided on the wiring substrate .

In this preferred embodiment, the adhesive resin is applied across a plurality of electronic components, such as, the two electronic components and , and the rest of the structure is substantially equivalent to that in the first preferred embodiment.

As shown in FIG. 3, since the adhesive resin is applied across the electronic components and , the positional relationship therebetween is fixed. Hence, in a solder reflow process in which this electronic device la is mounted on a surface mounting substrate, such as a motherboard, even when the solder which forms the solder fillets is melted, the electronic components and are prevented from moving independently, and as a result, variations in the properties of the electronic device la are prevented from occurring.

In addition, since the two electronic components and are mechanically integrated, even when one of the electronic components and has a weak bonding strength to the wiring substrate , the electronic components and are prevented from falling from the wiring substrate and being damaged by external impact due to the fall, bending, or other external forces on the electronic device.

FIG. 4 is view showing an electronic device of a third preferred embodiment according to the present invention and is a view corresponding to that in FIG. . In FIG. 4, the same reference numerals of the elements in FIG. 2 designate the equivalent elements, and descriptions thereof are omitted.

In FIG. 4, two electronic components and mounted on the wiring substrate are shown. One electronic component is an IC chip component similar to the electronic component shown in FIG. 2, and is soldered to the conductive lands provided on the wiring substrate with several solder bumps provided therebetween. The other electronic component is a chip component which surface-mounted similar to the electronic component or shown in FIG. 3. A solder fillet is shown in FIG. . The electronic component is soldered to conductive lands formed on the wiring substrate via the solder fillet .

In this preferred embodiment, the adhesive resin is applied across a plurality of electronic components, such as the two electronic components and . The rest of the structure is substantially equivalent to that in the second preferred embodiment described above, and the same advantages are achieved.

In addition, in this preferred embodiment, since the electronic components and , which are mechanically integrated, each have a relatively large planar area, a reinforcing structure for increasing the bending strength of the wiring substrate is provided. Hence, damage such as breakage of the wiring substrate , which is caused by impact applied thereto due to a fall, bending, or other external force on the electronic device , is reliably prevented.

Furthermore, according to this preferred embodiment, the following effects are also achieved.

When the solder bumps provided for the electronic component are made of eutectic solder, and the electronic device is mounted on an appropriate motherboard by a solder reflow process, the solder bumps may be melted such that the electronic component moves with respect to the wiring substrate , and in the worst case, electrical short circuiting may occur by solder between adjacent conductive lands connected to the respective solder bumps .

However, when high temperature solder is used for the solder fillet for soldering the other electronic component to the wiring substrate , the solder fillet does not melt, and hence the electronic component reliably maintains its position with respect to the wiring substrate . As a result, the electronic component fixed to the electronic component with the adhesive resin is reliably maintained in its position with respect to the wiring substrate .

FIG. 5 is a view showing an electronic device of a fourth preferred embodiment according to the present invention and is a view corresponding to that in FIG. . In FIG. 5, the same reference numerals of the elements in FIG. 2 designate the equivalent elements, and descriptions thereof are omitted.

In FIG. 5, two electronic components and mounted on the wiring substrate are shown. One electronic component is an IC chip component similar to the electronic component shown in FIG. 4, and is soldered to the conductive lands provided on the wiring substrate with several solder bumps provided therebetween. The other electronic component is a chip component to be surface-mounted similar to the electronic component shown in FIG. 4. A solder fillet is shown in FIG. . The electronic component is soldered to conductive lands formed on the wiring substrate via the solder fillet .

In this preferred embodiment, the adhesive resin is supplied through the opening provided in the top wall of the case so as to adhere the electronic component to the case . In addition, before the case is provided on the wiring substrate , an adhesive resin is applied across the two electronic components and . These adhesive resins and are applied so as not to contact the wiring substrate .

In this preferred embodiment, the adhesive resins and have compositions that are different from each other. More particularly, compared to the adhesive resin , the adhesive resin in an uncured state preferably has a low viscosity and a small thixotropic index. Thus, the adhesive resin easily spreads along the top surface of the electronic component , and the adhesive resin is unlikely to flow down to the wiring substrate . For example, the viscosity and the thixotropic index of the adhesive resin are both preferably at least twice those of the adhesive resin .

The adhesive resin is preferably made of a material having the particular composition and properties described above (viscosity and thixotropic index), and the adhesive resin is preferably made of a material having the following composition and properties (viscosity and thixotropic index).

(Composition)

According to this fourth preferred embodiment, similar advantages to those of the second and the third preferred embodiments are obtained, and when the compositions of the adhesive resins and are different from each other, the adhesive resins and having favorable properties are obtained.

FIGS. 6A and 6B are views schematically showing an electronic device of a fifth preferred embodiment according to the present invention, FIG. 6A is a cross-sectional view of the electronic device , and FIG. 6B is a plan view thereof. In order to easily compare the electronic device shown in FIG. 6 to a related electronic device shown in FIG. 8, the basic structure of the electronic device is the same as that of the electronic device .

As shown in FIGS. 6A and 6B, the electronic device includes a wiring substrate . Although not shown in detail in the figure, the wiring substrate may be a multilayer ceramic substrate including ceramic layers laminated to each other and including passive elements, such as capacitors, inductors, resistors, filters, or delay lines, and wiring conductors. In addition, although not shown in the figures, several terminal electrodes to be connected to a motherboard on which the electronic device is mounted are provided on a peripheral side surface of the wiring substrate or on the bottom surface thereof, and on the top surface of the wiring substrate , several conductive lands are provided.

On the top surface of the wiring substrate , at least two electronic components and are mounted by soldering.

The electronic component is preferably an IC chip component, such as an RFIC, baseband (BB) IC, or memory, and is soldered to conductive lands provided on the wiring substrate with several solder bumps provided therebetween. The other electronic component is preferably a chip component to be surface-mounted, such as a capacitor, inductor, or quartz oscillator, and is soldered to conductive lands formed on the wiring substrate with a solder fillet formed by soldering.

In this electronic device , among a plurality of the electronic components mounted on the wiring substrate , the electronic component shown in the figure has the largest planar area, and the electronic component has the second largest planar area.

In this preferred embodiment, the two electronic components and are adhered to each other with an adhesive resin . As can be seen in detail in FIG. 6A, this adhesive resin is applied onto the top surfaces of the electronic components and so as not to contact the wiring substrate .

The adhesive resin may extend to at least one side surface of the electronic components and , but not so as to contact the wiring substrate . Even when applied so as to extend to at least one side surface of the electronic components and as described above, for example, the adhesive resin preferably does not contact the solder fillet formed on the side surfaces of the electronic component . As a result, the movement of melted solder generated by remelt of the solder fillet is not restricted by the adhesive resin , and hence, the generation of short circuiting by solder due to the restriction of the move of this melted solder is prevented.

The adhesive resin in an uncured state is supplied across the electronic components and , for example, by a dispenser and is then cured by heating.

As the adhesive resin , for example, a thermosetting resin such as an epoxy resin is used, and in order to prevent the resin from flowing down to the wiring substrate , in more particular, a material having the composition and properties (viscosity and thixotropic index) similar to those of the adhesive resin is preferably used.

As described above, according to the fifth preferred embodiment, since the two electronic components and are mechanically integrated, even when one of the electronic components and has a weak bonding strength to the wiring substrate , the electronic components and are prevented from falling from the wiring substrate and being damaged by impact applied thereto from the outside due to a fall, bending, or other external force on the electronic device .

In addition, the mechanically integrated electronic components and provide a reinforcing structure in order to increase the bending strength of the wiring substrate . Accordingly, the wiring substrate is prevented from being damaged, for example, broken by impact applied thereto due to a fall, bending, or other external force on the electronic device .

The advantages described above are increasingly obtained when the planar areas of the electronic components and are increased. Hence, as in this preferred embodiment, the adhesive resin is preferably applied across the electronic component having the largest planar area and the electronic component having the second largest planar area.

Furthermore, according to this preferred embodiment, as is the third preferred embodiment shown in FIG. 4 described above, when the solder bumps of the electronic component are made, for example, of eutectic solder, and when high temperature solder is used for the solder fillet for soldering the electronic component to the wiring substrate , in a solder reflow process for mounting the electronic device on a motherboard, this solder fillet is prevented from being remelted even when the solder bumps are remelted. Hence, since the position of the electronic component with respect to the wiring substrate is reliably maintained, the position of the electronic component , which is fixed to the electronic component with the adhesive resin applied therebetween, is also be reliably maintained with respect to the wiring substrate . Accordingly, short circuiting between the conductive lands adjacent to each other connected to the solder bumps caused by solder, which is generated by the movement of the electronic component with respect to the wiring substrate , is reliably prevented.

In addition, since the adhesive resin is applied so as not to contact the wiring substrate , when this electronic device is mounted on an appropriate motherboard by a solder reflow process, the movement of the melted solder generated when the solder bumps and the solder fillet are remelted is not restricted by the adhesive resin , and hence short circuiting between different terminals of the electronic components and caused by the solder, which is generated by the restriction of the movement of melted solder, is prevented.

FIGS. 7A and 7B are views each schematically showing an electronic device of a sixth preferred embodiment according to the present invention, FIG. 7A is a cross-sectional view of the electronic device , and FIG. 7B is a plan view thereof.

As shown in FIGS. 7A and 7B, the electronic device includes a wiring substrate , and on the top surface of the wiring substrate , at least a first, a second, and a third electronic component , , and are provided, in which the second and the third electronic components and are disposed at two opposed sides of the first electronic component .

The first electronic component is, for example, an IC chip component and is soldered to the conductive lands provided on the wiring substrate with several solder bumps provided therebetween. The second and the third electronic components and are chip components, such as capacitors, inductors, or quartz oscillators, and are soldered to the wiring substrate with solder fillets and , respectively, which are provided therebetween and are formed by soldering.

In this sixth preferred embodiment, the first electronic component and the second electronic component are adhered to each other with an adhesive resin , and in addition, the first electronic component and the third electronic component are adhered to each other with an adhesive resin .

The adhesive resins and are preferably made of a material having the equivalent composition and properties (viscosity and thixotropic index) to those of the adhesive resin described above.

The rest of the structure is similar to that in the fifth preferred embodiment described above, and hence description thereof is omitted.

In this sixth preferred embodiment, the same advantages as those in the fifth preferred embodiment are obtained, and since the three electronic components to are adhered to each other with the adhesive resins and , the total planar area of the electronic components to is greater than that of the electronic components and described above. Thus, the mechanical strength of the electronic device is increased as compared to that in the fifth preferred embodiment.

Heretofore, the present invention has been described with reference to several preferred embodiments, and within the spirit and the scope of the present invention, various modifications may be further performed.

For example, the case shown in FIGS. 1 to is preferably made of a metal. However, the present invention may be applied to an electronic device provided with a resin case.

In addition, the case is fixed to the wiring substrate preferably via soldering using the solder . However, in addition to a soldering method, for example, the case may be fixed to the wiring substrate with claws engaged therewith.

The size, shape, and number of openings provided in the case may be optionally changed.

In addition, when the case is not provided with the opening, the adhesive resin may be applied before the case is provided on the wiring substrate, and the electronic component and the case may be adhered to each other by fixing the case to the wiring substrate.

In addition, as long as it is primarily composed of a resin component, the adhesive resin may include a pigment such as carbon, a curing agent, and other suitable additives as described above.

The electronic components to , , , , , , , , , and to are preferably bump (ball) grid array electronic components each provided with solder bumps or surface-mountable electronic components each provided with electrodes at the end portions thereof. Alternatively, land grid array electronic components or electronic components provided with input/output terminals at side surfaces thereof may also be used.

In addition, the number of the electronic components adhered to each other with the adhesive resin and mounted on the wiring substrate is preferably two to three in the preferred embodiments shown in the figures. However, the number of the electronic components may be four or more.

As has thus been described, according to preferred embodiments of the present invention, since the first and the second units provided on the wiring substrate are mechanically integrated, even when one of the first and the second units has a weak bonding strength to the wiring substrate, these units are prevented from being damaged or falling from the wiring substrate by impact applied thereto.

The first and the second units that are mechanically integrated as described above advantageously define a reinforcing structure which improves the bending strength of the wiring substrate. Accordingly, damage, such as breakage, to the wiring substrate caused by impact applied thereto due to a fall or bending is effectively prevented. In addition, when being reinforced, the wiring substrate is unlikely to be bent, and hence units, which are not adhered with an adhesive resin, do not fall from the wiring substrate and are not damaged.

In preferred embodiments of the present invention, when the first unit includes an electronic component mounted on the wiring substrate via soldering, the second unit includes a case fixed to the wiring substrate so as to cover the electronic component, and the adhesive resin is applied on the top surface of the electronic component and the bottom surface of the top wall of the case, since the electronic component and the case are adhered to each other with the adhesive resin, the fixing strength of fixing the case to the wiring substrate is greatly improved. Accordingly, even when impact due to a fall or other external force is applied, the case is unlikely to fall or be removed from the wiring substrate.

In addition, with the adhesive resin applied between the electronic component and the case, each of the gaps between the case and the electronic component and the wiring substrate are maintained constant, and the change in characteristics caused by a change in the gaps described above is prevented.

In addition, according to preferred embodiments of the present invention, since the adhesive resin is applied so as not to contact the wiring substrate, even when heat applied in a solder reflow process is conducted to the solder used for mounting the electronic component on the wiring substrate, and this solder is melted, the solder is prevented from easily flowing so as to cause short circuiting between terminal electrodes of the electronic component. That is, when the adhesive resin is applied so as to contact the wiring substrate and cover the electronic component, the solder for mounting the electronic component is melted and expanded in a solder reflow process, stress is applied to the resin covering the electronic component, and as a result, interface separation occurs between the resin and the wiring substrate. When interface separation occurs, the solder flows in the portion at which the interface separation occurs and causes short circuiting between different terminal electrodes of the electronic component mounted on the wiring substrate. In contrast, in preferred embodiments of the present invention, when the adhesive resin is applied so as not to contact the wiring substrate, the problems described above are prevented.

In addition, since the adhesive resin is applied inside the case, the flatness of the top surface of the case is not deteriorated. Accordingly, in addition to the improvement in mechanical strength, when the electronic device of preferred embodiments of the present invention is mounted on a motherboard, holding of the electronic component can be reliably performed, for example, by vacuum chuck, and hence the reliability of a mounting step is greatly improved.

In preferred embodiments of the present invention, when the opening for supplying the adhesive resin from the outside is provided in the top wall of the case, after the case is fixed to the wiring substrate, the adhesive resin is easily supplied between the electronic component and the case. Accordingly, if an electronic device is rejected as a defective before the adhesive resin is supplied, the electronic component can be removed from the wiring substrate for reuse, and in particular, an expensive electronic component such as an IC chip component can be advantageously reused.

When the opening described above is sealed with the adhesive resin, foreign materials are prevented from intruding into the case through the opening. In particular, in the case in which a tightly sealed space is formed inside the case, when the opening is sealed with the adhesive resin, the sealing properties do not deteriorate. In addition, when the opening is sealed with the adhesive resin, a suction position for a suction nozzle of a mounting machine is freely selected in a mounting step without any restrictions on the position of the opening.

When the opening is provided at a position shifted from the center of the top wall of the case toward the peripheral side thereof, a relatively large area at the central portion of the case can be used for marking, and in addition, the opening can be used as a mark to indicate the directionality of the device. In this case, when the adhesive resin includes a pigment such as carbon, the opening is colored such that the difference in color from the case is more visible, and as a result, the mark described above is more effectively obtained.

When the adhesive resin is applied across a plurality of electronic components, the positional relationship of the electronic components is ensured, and for example, in a solder reflow process, even when solder for mounting the electronic component is melted, the individual electronic components are prevented from moving independently, and as a result, changes in the properties of the electronic device are minimized.

When the top surface of the electronic component has at least a resin portion, and the adhesive resin is applied on this resin portion for adhesion, and the adhesion strength between the adhesive resin and the electronic component is greatly improved.

When the case is made of metal, the shielding effect is obtained by the case. Accordingly, in particular, the present invention is advantageously applied to a high-frequency electronic device. In addition, since the case made of metal can be fixed to the wiring substrate by soldering, specifically designed portions such as claws used for fixing and an assembly step thereof are not required, and hence reduction in component cost and assembly cost is achieved.

In the case in which a third unit is disposed between the sidewall of the case and the wiring substrate, when a space is provided between the sidewall and the third unit, the case is prevented from contacting the third unit even if the fixing position of the case is undesirably shifted, and hence the third unit is prevented from being damaged. In addition, the fixing strength of fixing the case to the wiring substrate is not decreased.

When the adhesive resin is applied to the top surface of the electronic component, which has the largest area, the adhesive resin in an uncured state is prevented from flowing down along a side surface of the electronic component, and hence the adhesive resin is more easily prevented from contacting the wiring substrate.

When the adhesive resin is applied to the top surface of an electronic component which has the largest height, the electronic component and the case are adhered to each other even with a small amount of the adhesive resin, and hence the adhesive resin in an uncured state is more easily prevented from flowing down along a side surface of the electronic component.

In addition, according to the electronic device of preferred embodiments of the present invention, where the first and the second electronic components are provided, in which the first electronic component is adhered to the case with the first adhesive resin, and in which the first electronic component and the second electronic component are adhered to each other with the second adhesive resin, when a material having a low viscosity and a low thixotropic index in an uncured state is used as the first adhesive resin as compared to those of the second adhesive resin, the first adhesive resin is likely to smoothly spread along the top surface of the first electronic component, and the second adhesive resin is reliably prevented from flowing down to the wiring substrate.

According to preferred embodiments of the present invention, where the first and the second units are the first and the second electronic components mounted on the wiring substrate via soldering, and the electronic device of the present invention is mounted on an appropriate motherboard by a solder reflow process, even when the solder connecting the electronic component and the wiring substrate is melted, this electronic component is prevented from moving by the other electronic component adhered thereto with the adhesive resin. In addition, short circuiting caused by the solder due to the movement of the electronic component as described above is effectively prevented.

In preferred embodiments of the present invention, when one of the first and the second electronic components adhered to each other with the adhesive resin is an IC chip component having the largest area of electronic components mounted on the wiring substrate, the mechanical strength of the electronic device described above is more effectively improved. In addition, when the other electronic component adhered to the electronic component having the largest plane area as described above has the second largest plane area of the electronic components mounted on the wiring substrate, the effect described above is further improved.

In addition, when the first, the second, and the third electronic components are provided, the second and the third electronic components being disposed at two opposed sides of the first electronic component, and the first electronic component is adhered to the second and the third components with the adhesive resins, the entire planar area of the first to the third electronic components is relatively increased, and hence the effect of improving the mechanical strength of the electronic device is further improved.

In preferred embodiments of the present invention, in addition to the first and the second electronic components adhered to each other by the adhesive resin, when the case fixed to the wiring substrate to cover the above electronic components is further provided, and the adhesive resin is also applied to this case, since the electronics components mechanically integrated with the adhesive resin is also integrated with the case, the effect of improving the mechanical strength of the electronic device is further improved.

It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an electronic device of a first preferred embodiment according to the present invention;

FIG. 2 is a cross-sectional view taken along the line II—II in FIG. 1;

FIG. 3 is a cross-sectional view showing an electronic device of a second preferred embodiment according to the present invention, the view corresponding to that in FIG. 2;

FIG. 4 is a cross-sectional view showing an electronic device of a third preferred embodiment according to the present invention, the view corresponding to that in FIG. 2;

FIG. 5 is a cross-sectional view showing an electronic device of a fourth preferred embodiment according to the present invention, the view corresponding to that in FIG. 2;

FIG. 6A is a cross-sectional view schematically showing an electronic device of a fifth preferred embodiment according to the present invention;

FIG. 6B is a plan view schematically showing the electronic device of the fifth preferred embodiment according to the present invention;

FIG. 7A is a cross-sectional view schematically showing an electronic device of a sixth preferred embodiment according to the present invention;

FIG. 7B is a plan view schematically showing the electronic device of the sixth preferred embodiment according to the present invention; and

FIG. 8 is a cross-sectional view schematically showing a conventional electronic device.

CLAIMS

1. An electronic device comprising: a wiring substrate; a first unit and a second unit which are mounted on the wiring substrate; the first unit includes at least one surface mount electronic component which is mounted on the wiring substrate via solder; the second unit includes a case which is fixed to the wiring substrate so as to cover the at least one surface mount electronic component; an adhesive resin which adheres the first unit to the second unit; a third unit disposed between wiring substrate and a bottom surface of a sidewall of the case; wherein the adhesive resin is not in contact with the surface of the wiring substrate; the adhesive resin is provided between the top surface of the at least one surface mount electronic component and the bottom surface of the top wall of the case; and a space is provided between the bottom surface of the sidewall of the case and the third unit.

2. An electronic device according to claim 1, wherein the top wall of the case is provided with an opening for supplying the adhesive resin from outside.

3. An electronic device according to claim 2, wherein the opening is sealed with the adhesive resin.

4. An electronic device according to claim 2, wherein the opening is provided at a position shifted from the center of the top wall of the case.

5. An electronic device according to claim 1, wherein the first unit includes a plurality of the electronic components, and the adhesive resin is provided across said plurality of the electronic components.

6. An electronic device according to claim 1, wherein the top surface of the at least one surface mount electronic component includes at least one resin portion, and the adhesive resin is provided on at least one resin portion.

7. An electronic device according to claim 1, wherein the case is made of a metal.

8. An electronic device according to claim 7, wherein the case is fixed to the wiring substrate with solder.

9. An electronic device according to claim 1, further comprising a plurality of electronic components, wherein top surfaces of the electronic components have areas that are different from each other, and the adhesive resin is provided on at least the top surface of one of the electronic components having the largest area.

10. An electronic device according to claim 1, further comprising a plurality of electronic components, wherein the plurality of electronic components have heights that are different from each other, and the adhesive resin is provided on at least the top surface of one of the electronic components having the largest height.

11. An electronic device according to claim 1, wherein the at least one surface mount electronic component includes a first electronic component and a second electronic component, the adhesive resin includes a first adhesive resin for adhering the first electronic component to the case and a second adhesive resin for adhering the first electronic component to the second electronic component, and the first adhesive resin and the second adhesive resin have compositions that are different from each other.

12. An electronic device according to claim 11, wherein the first adhesive resin, in an uncured state, has a lower viscosity and a lower thixotropic index as compared to those of the second adhesive resin.

13. An electronic device according to claim 1, wherein the first unit includes a first surface mount electronic component, the second unit includes a second surface mount electronic component, and the first and the second surface mount electronic components are mounted on the wiring substrate with solder.

14. An electronic device according to claim 13, wherein one of the first electronic component and the second electronic component adhered thereto with the adhesive resin has the largest planar area of the electronic components mounted on the wiring substrate.

15. An electronic device according to claim 14, wherein the electronic component having the largest planar area is an IC chip component.

16. An electronic device according to claim 14, wherein the other electronic component adhered to the electronic component having the largest planar area has the second largest planar area of the electronic components mounted on the wiring substrate.

17. An electronic device according to claim 13, wherein one of the first and the second units further includes a third surface mount electronic component mounted on the wiring substrate via soldering, the second and the third electronic components are arranged at two opposed sides of the first electronic component opposing each other, and the first electronic component is adhered to the second and the third electronic components with the adhesive resin.

18. An electronic device according to claim 13, further comprising a case fixed to the wiring substrate so as to cover the first and the second electronic components, wherein the adhesive resin is adhered to the case.

19. An electronic device according to claim 18, wherein the case has a top wall provided with an opening for supplying the adhesive resin from the outside.

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