# Patent

## Title
Electronic device, electronic apparatus mounted with electronic device, article equipped with electronic device and method of producing electronic device

## Abstract

An electronic device includes: a base; a conductor pattern formed on the base; and a circuit chip electrically connected to the conductor pattern. The electronic device further includes a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes layers stacked in the thickness direction of the base. The lowermost layer of the layers is closest to the base and softer than the layer that is at least one of the remaining layers. The electronic device further includes a sealing member which fills an inside of the reinforcing member while covering the top of the circuit chip, thereby sealing the circuit chip on the base.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation application of PCT/JP2007/056078, filed on Mar. 23, 2007.


TECHNICAL FIELD
The present invention is related to an electronic device, an electronic apparatus mounted with the electronic device, an article equipped with the electronic device and a method of producing the electronic device.
BACKGROUND ART
Conventionally, there is widely known an electronic device having a base such as a printed wiring board and a circuit chip mounted on the base. This type of electronic device is used to control an electronic apparatus by being disposed within this electronic apparatus, or is used independently to exchange information with an external device. As an example of such an electronic device, there is known a RFID (Radio_Frequency_IDentification) tag that exchanges information with an external device represented by a reader/writer in a non-contact manner using radio waves. There are various types of RFID tags. As one type of RFID tag, there is proposed a tag having a structure in which a conductor pattern for radio communications and an IC chip are mounted on a base made of a plastic, a piece of paper, etc (see, for example, Japanese Laid-open Patent Publication No. 2001-156110). It has been conceived to use this type of RFID tag in such a manner that the RFID tag is adhered to an article to identify the article by exchanging information about the article with an external device.
FIG. 1 is a schematic cross-sectional diagram of an example of a conventional RFID tag.
A RFID tag 90 illustrated in FIG. 1 includes: a base 91 made of a flexible PET film or the like; an antenna 92 made of a conductor pattern and formed on the base 91; and a circuit chip 93 disposed on the antenna 92. In this circuit chip 93, a circuit for exchanging information with an external device through the antenna 92 is incorporated. The circuit chip 93 has connecting terminals 93a formed under the circuit chip 93, which are electrically connected to the antenna 92 by soldering or the like. Further, the circuit chip 93 is secured onto the base 91 with an adhesive 94. On the base 91 of the RFID tag 90, there are also provided: a potting compound 95 covering the circuit chip 93; and a ring-shaped reinforcing member 96 disposed to surround the circuit chip 93. There is also provided a covering member 97 that covers the entire tag main body including the base 91, the antenna 92, the circuit chip 93, the potting compound 95 and the reinforcing member 96. The potting compound 95 includes an inner portion 95a filling the inside of the reinforcing member 96 shaped like a ring. The inner portion 95a covers the top of the circuit chip 93 and seals the circuit chip 93 on the base 91.
There are cases where the RFID tag 90 receives a strong external force when the RFID tag 90 is used by being attached to an article made of a flexible material, such as clothing, and the RFID tag 90 is bent while being washed. As for the RFID tag 90, since the RFID tag 90 is provided with the potting compound 95 and the reinforcing member 96 disposed around the circuit chip 93 to protect the circuit chip 93, a crack in the circuit chip 93 per se is prevented even when the RFID tag 90 is bent.
DISCLOSURE OF INVENTION
In the RFID tag 90 however, although the circuit chip 93 of the RFID tag 90 is protected, a peripheral part of the reinforcing member 96 may be damaged. For example, when a bending stress is applied to the base 91, the applied stress may concentrate on an exposed part (a part surrounded by a circle indicated with a dashed line as illustrated in FIG. 1) of the antenna 92 outside the reinforcing member 96, thereby breaking the antenna 92.
A problem due to such a damage of a peripheral portion of the reinforcing member 96 is not limited to RFID tags and is common to electronic devices provided with a flexible base mounted with a circuit chip.
In view of the above circumstances, it is an object of the present invention to provide: an electronic device in which a bending stress applied to a circuit chip is reduced and breaking of a conductor pattern is avoided; an electronic apparatus mounted with the electronic device; an article equipped with the electronic device; and a method of producing the electronic device.
An electronic device of the present invention achieving the above object includes:
a base;
a conductor pattern formed on the base;
a circuit chip electrically connected to the conductor pattern;
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers; and
a sealing member which fills an inside of the reinforcing member while covering a top of the circuit chip, thereby sealing the circuit chip on the base.
In the electronic device of the present invention, the sealing member has such a structure that the sealing member covers the top of the circuit chip by filling the inside of the reinforcing member in the shape of a ring, thereby sealing the circuit chip on the base. Therefore, a stress is unlikely to be applied to the circuit chip even when the base is bent, which prevents cracking and peeling of the circuit chip. Further, the reinforcing member has the lowermost layer that is close to the conductor pattern and soft. Therefore, a stress applied when the electronic device is bent is dispersed in the other layers without concentrating on the lowermost layer, preventing the conductor pattern from breaking.
In the electronic device according to the present invention, preferably, the lowermost layer is made of an elastomer.
When the lowermost layer is made of an elastomer, a stress applied by bending is received with flexibility because the elastomer is flexible.
In the electronic device according to the present invention, the electronic device may be a RFID tag that causes the conductor pattern to function as a communications antenna and causes the circuit chip to carry out wireless communications via the conductor pattern.
An RFID tag used in the state of being attached to an article or a card is frequently bent. Therefore, the electronic device of the present invention is preferably applied to the RFID tag.
An electronic apparatus of the present invention achieving the above object includes:
an electronic device; and
an apparatus main section driven by an operation of the electronic device,
wherein the electronic device includes:
a base,
a conductor pattern formed on the base,
a circuit chip electrically connected to the conductor pattern,
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, and
a sealing member which fills an inside of the reinforcing member while covering a top of the circuit chip, thereby sealing the circuit chip on the base.
In the electronic apparatus of the present invention, a break in the conductor pattern is prevented even when, for example, the electronic apparatus itself is bent or the electronic device is bent for repair or maintenance. Therefore, the reliability of the electronic apparatus is improved.
An article of the present invention achieving the above object includes:
an electronic device; and
an object equipped with the electronic device,
wherein the electronic device includes:
a base,
a conductor pattern formed on the base,
a circuit chip electrically connected to the conductor pattern,
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, and
a sealing member which fills an inside of the reinforcing member while covering a top of the circuit chip, thereby sealing the circuit chip on the base.
For example, there are cases where an article equipped with the electronic device such as a RFID tag is bent together with the electronic device. Even in such a situation, cracking and peeling of the circuit chip as well as a break in the conductor pattern are prevented.
A method of producing an electronic device according to the present invention achieving the above object is a method including:
connecting a circuit chip to a conductor pattern formed on a base;
applying an adhesive to cover a top of the circuit chip with the adhesive;
disposing a reinforcing member whose outer shape is like a ring and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, so that the circuit chip is surrounded by the reinforcing member on the base and an inside of the reinforcing member is filled with the adhesive; and
curing the adhesive thereby sealing the circuit chip on the base with the adhesive and fixing the reinforcing member on the base.
In the method of producing the electronic device according to the present invention, the reinforcing member including two or more layers is disposed on the base to surround the circuit chip and moreover, the adhesive in the state of filling the inside of the reinforcing member is cured. As a result, there is produced an electronic device in which a stress is distributed to two or more layers.
As described above, according to the present invention, a concentration of a bending stress on the circuit chip as well as a concentration of a stress on the conductor pattern are avoided.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic cross-sectional diagram of an example of a conventional RFID tag.
FIG. 2 is a cross-sectional view of a RFID tag that is an embodiment of the present invention.
FIG. 3 is a plan view of the RFID tag that is the embodiment of the present invention.
FIG. 4 is a diagram for describing a method of producing the RFID tag illustrated in FIG. 2 and FIG. 3.
FIG. 5 is a diagram for describing a method of producing clothing to which the RFID tag is attached.
FIG. 6 is a schematic diagram of a printed circuit board device that is an embodiment of the present invention and an electronic desk calculator where the printed circuit board device is implemented.



BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 2 and FIG. 3 are a cross-sectional view and a plan view, respectively, of a RFID tag that is a first embodiment of the electronic device of the present invention. Incidentally, a central part of the RFID tag illustrated in FIG. 2 is made larger than that illustrated in FIG. 3 so that the structure may be readily viewed.
The RFID tag 10 illustrated in FIG. 2 and FIG. 3 has a reinforcing member whose structure is different from that of the RFID tag 90 illustrated in FIG. 1. Otherwise, the RFID tag 10 illustrated in FIG. 2 and FIG. 3 is the same as the RFID tag 90 illustrated in FIG. 1. To be more specific, an antenna 12 is formed on a flexible base 11 and a circuit chip 13 is mounted on the base 11, and the circuit chip 13 is fixed with an adhesive 14. Provided also on the base 11 are a potting compound 15 that covers the top of the circuit chip 13 and a ring-shaped reinforcing member 16 disposed to surround the circuit chip 13. Further, the entire device including the base 11, the antenna 12, the circuit chip 13, the potting compound 15 and the reinforcing member 16 is covered with a covering member 17. Incidentally, the covering member 17 is not illustrated in FIG. 3 so that the internal structure may be readily viewed.
The reinforcing member 16 has a ring-like outer shape and also has a two-layer structure including a lower layer 16a and an upper layer 16b stacked in the thickness direction of the base 11. The lower layer 16a and the upper layer 16b of the reinforcing member 16 are made of different types of resin materials. The material of the lower layer 16a is softer than the material of the upper layer 16b. Acryl (PMAA), for example, may be adopted as the material of the upper layer 16b, but other materials such as polyacetal (POM) and polyphenylene sulfide (PPS) may be employed. As the material of the lower layer 16a, for example, an elastomer such as rubber softer than the material of the upper layer 16b may be adopted, but other materials such as polypropylene (PP), ABS resin (ABS) and polyvinyl chloride (PVC) may be employed. The lower layer 16a and the upper layer 16b may be made of materials which include the same type of resin as the main component and whose softness are adjusted according to the types and added amounts of additives. Nevertheless, it is preferable to employ an elastomer in view of providing the lower layer 16a with flexibility.
The potting compound 15 is divided into an inner portion 15a that fills the inside of the reinforcing member 16 and an outer portion 15b that surrounds the reinforcing member 16 from outside. The inner portion 15a of the potting compound 15 filling the inside of the reinforcing member 16 covers the top of the circuit chip 13 and seals the circuit chip 13 on the base 11.
The antenna 12 is an example of the conductor pattern according to the present invention, and the inner portion 15a of the potting compound 15 is an example of the reinforcing member according to the present invention. Further, the lower layer 16a is an example of the lowermost layer according to the present invention.
In the RFID tag 10, the reinforcing member 16 disposed to surround the circuit chip has the lower layer 16a and the upper layer 16b, and the lower layer 16a close to and disposed right under the antenna 12 is softer than the upper layer 16b. Therefore, even when the RFID tag 10 is bent, a concentration of a stress applied to the lower layer 16a is suppressed and a break in the antenna 12 is prevented. Further, the RFID tag 10 has such a structure that: the circuit chip 13 is surrounded by the reinforcing member 16; the top of the circuit chip 13 is covered by the inner portion 15a of the potting compound 15, which portion fills the inside of the reinforcing member 16; and the circuit chip 13 is sealed by both the inner portion 15a and the base 11. This structure prevents a concentration of the stress on the circuit chip 13 as well as cracking, peeling etc. of the circuit chip 13.
Next, a method of producing the RFID tag will be described.
FIG. 4 is a diagram for describing the method of producing the RFID tag illustrated in FIG. 2 and FIG. 3.
FIG. 4 illustrates a sequence of processes for producing the RFID tag in parts (a) through (e).
In order to obtain the RFID tag 10, first, the circuit chip 13 is connected to the antenna 12 formed on the base 11 in a connection process illustrated in part (a) of FIG. 4.
Subsequently, in an adhesive application process illustrated in part (b) of FIG. 4, a liquid potting compound 15p made of a thermosetting resin material is applied to cover the top of the circuit chip 13. The liquid potting compound 15p is also applied around the circuit chip 13.
Next, in a reinforcing-member arrangement process illustrated in parts (c) and (d) of FIG. 4, the reinforcing member 16 shaped like a ring and including the lower layer 16a and the upper layer 16b is disposed on the base 11 after being aligned to surround the circuit chip 13. In this reinforcing-member arrangement process, the reinforcing member 16 is disposed in such a position that the lower layer 16a is directed toward the base 11. When the reinforcing member 16 is disposed to sink into the liquid potting compound 15p, the potting compound 15p is divided into two parts to be respectively in two locations; the inner side and the outer side of the reinforcing member 16. Subsequently, as illustrated in part (d), the liquid potting compound 15p is cured by being heated. As a result, the inner portion 15a is formed in the inside of the upper layer 16b. 
Next, in a covering process illustrated in part (e) of FIG. 4, the front side and the back side of the base 11 are covered with the covering member 17. The adhesion of the covering member 17 is achieved by heating and pressurizing the covering member 17. Upon completion of the covering process, the RFID tag 10 illustrated in FIG. 2 is obtained.
Next, as an example of applications for the RFID tag described above, there will be described clothing to which the RFID tag 10 is attached. This clothing is an embodiment of the article to which the electronic device of the present invention is attached.
FIG. 5 is a diagram for describing a method of producing the clothing to which the RFID tag is attached.
For example, the RFID tag 10 illustrated in FIG. 2 and FIG. 3 is fixed to a tag 5a of clothing 5 as illustrated in FIG. 5 with adhesion or the like. In the RFID tag 10 attached to the clothing 5, information representing attributes of the clothing 5 is stored. For example, attribute information about the clothing 5 such as a JAN code is transmitted from an information writing device 6 to the RFID tag 10 through wireless communications, and then the attribute information is stored in the circuit chip 13 (see FIG. 2).
In the above-described embodiment, the RFID tag has been described as an example of the electronic device. However, the electronic device of the present invention is not limited to the RFID tag and may be applied, for example, to a printed circuit board device where a circuit chip mounted on a flexible base is provided.
FIG. 6 is a schematic diagram of a printed circuit board device that is an embodiment of the present invention and an electronic desk calculator where the printed circuit board device is implemented.
An electronic desk calculator 7 illustrated in FIG. 6 has a calculator main section 71 and a printed circuit board device 75 implemented on the calculator main section 71. The printed circuit board device 75 has a structure similar to that of the RFID tag 10 illustrated in FIG. 2 and FIG. 3. In other words, a circuit chip 76 is mounted on a flexible printed circuit 77 (FPC 77) serving as a base. Further, although illustration is omitted, the printed circuit board device 75 has such a structure that: a reinforcing member having an upper layer and a lower softer than the upper layer which are stacked in the thickness direction of the base is placed on the FPC 77 to surround the circuit chip; and a sealing member covers the top of the circuit chip 76 and fills the inside of the reinforcing member, so that the circuit chip 76 is sealed by the FPC 77. However, the printed circuit board device 75 has features different from the RFID tag 10 illustrated in FIG. 2, which are: the circuit chip of the printed circuit board device 75 has the function of controlling the calculator main section 71; and a wiring pattern for transmitting signals between the circuit chip 76 and the calculator main section 71 is formed instead of an antenna. The calculator main section 71 is provided with a display section 71a for providing various types of displays and operation keys 71b, which are driven based on the operations of the circuit chip 76. In the electronic desk calculator 7 mounted with the printed circuit board device 75, a break in the wiring pattern on the printed circuit board device 75 is prevented even when the calculator main section 71 is bent.
Incidentally, there has been described the case in which the calculator main section 71 of the electronic desk calculator 7 is bent. However, the present invention is not limited to this case and may be applied, for example, to a case of an electronic apparatus having a main unit with a hard case where an electronic device in the state of being bent is disposed. Alternatively, the present invention may be applied to a case of an electronic apparatus with an electronic device that is prone to warp when removed for repair or maintenance. Also, the present invention is not limited to the electronic desk calculator and may be applied to various types of electronic apparatus such as a portable telephone on which an electronic device with a flexible base mounted with a circuit chip is implemented.
Further, the embodiments each having two layers have been described above, but the present invention is not limited to these embodiments and may have three or more layers.
Furthermore, although the embodiments each having a covering member have been described above, the electronic device of the present invention is not limited to these embodiments and may have no covering member.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

## Claims

1. An electronic device, comprising:
a base;
a conductor pattern formed on the base;
a circuit chip electrically connected to the conductor pattern;
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers; and
a sealing member including an inner portion and an outer portion, wherein the inner portion fills an inside of the reinforcing member while covering a top of the circuit chip to seal the circuit chip on the base, and the outer portion has a lower height than the reinforcing member to surround the reinforcing member from outside.

2. The electronic device according to claim 1, wherein the lowermost layer is made of an elastomer.

3. The electronic device according to claim 1, wherein the electronic device is a RFID tag that causes the conductor pattern to function as a communications antenna and causes the circuit chip to carry out wireless communications via the conductor pattern.

4. An electronic apparatus, comprising:
an electronic device; and
an apparatus main section driven by an operation of the electronic device,
wherein the electronic device comprises:
a base,
a conductor pattern formed on the base,
a circuit chip electrically connected to the conductor pattern,
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, and
a sealing member including an inner portion and an outer portion, wherein the inner portion fills an inside of the reinforcing member while covering a top of the circuit chip to seal the circuit chip on the base, and the outer portion has a lower height than the reinforcing member to surround the reinforcing member from outside.

5. An article, comprising:
an electronic device; and
an object equipped with the electronic device,
wherein the electronic device comprises:
a base,
a conductor pattern formed on the base,
a circuit chip electrically connected to the conductor pattern,
a reinforcing member which is disposed on the base to surround the circuit chip, whose outer shape is like a ring, and which includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, and
a sealing member including an inner portion and an outer portion, wherein the inner portion fills an inside of the reinforcing member while covering a top of the circuit chip to seal the circuit chip on the base, and the outer portion has a lower height than the reinforcing member to surround the reinforcing member from outside.

6. A method of producing an electronic device, the method comprising:
connecting a circuit chip to a conductor pattern formed on a base;
applying an adhesive to cover a top of the circuit chip with the adhesive;
disposing a reinforcing member onto the adhesive, wherein an outer shape of the reinforcing member is like a ring, and includes a plurality of layers stacked in a thickness direction of the base, the plurality of layers including a lowermost layer that is closest to the base and softer than at least any one of the remaining layers among the plurality of layers, so that the circuit chip is surrounded by the reinforcing member on the base, wherein an inside of the reinforcing member is filled with an inner portion of the adhesive, and an outer portion of the adhesive has a lower height than the reinforcing member to surround the reinforcing member from outside; and
curing the adhesive thereby sealing the circuit chip on the base with the adhesive and fixing the reinforcing member on the base.