RFID tag and manufacturing method thereof

• US 8,248,240 B2
• Filed: 07/29/2008
• Issued: 08/21/2012
• Est. Priority Date: 09/28/2007
• Status: Expired due to Fees

• Current Assignee: Fujitsu Frontech Limited (Fujitsu Limited), Fujitsu Limited
• Original Assignee: Fujitsu Frontech Limited (Fujitsu Limited), Fujitsu Limited
• Inventors: Baba, Shunji, Hashimoto, Shigeru, Sugimura, Yoshiyasu, Nogami, Satoru, Osaki, Noritsugu
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Wang, Jack
• Application Number:
  US12/181,631
• Publication Number:
  US 20090085747A1
• Time in Patent Office: 1,484 Days
• Field of Search: 340/572.8, 235/492, 235/435
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/07724 the record carrier being at least partially made by a molding process molding in general B29C45/14
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/0775 arrangements for connecting the integrated circuit to the antenna
• CPC Class Codes: H05K 2201/10689 Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• CPC Class Codes: H05K 2201/10719 Land grid array [LGA]
• CPC Class Codes: H05K 2201/10977 Encapsulated connections applying non-metallic protective coatings for encapsulating mounted components H05K3/284
• CPC Class Codes: H05K 3/305 Affixing by adhesive
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

An RFID tag includes an inlay which has a base, an antenna formed on the base, and an IC chip. The IC chip is enclosed in a surface mount package and soldered to the antenna and carries out radio communication through the antenna. The RFID tag further includes underfill that fills a gap between the base and the surface mount package, and a sheath protecting material enclosing the entire inlay.

Claims

1. An RFID tag comprising:

an inlay which includes a base, an antenna formed on the base, an IC chip which is enclosed in a surface mount package and soldered to the antenna and which carries out radio communication through the antenna, and underfill which fills a gap between the base and the surface mount package; and

a sheath protecting material enclosing the entire inlay,

wherein where a thermal expansion coefficient of the surface mount package is defined as α

1,

a thermal expansion coefficient of the underfill is defined as α

2,

a thermal expansion coefficient of the base is defined as α

3, and

a thermal expansion coefficient of the sheath protecting material is defined as α

4, relations α

1<

α

2 and α

4<

α

3 are satisfied.

2. The RFID tag according to claim 1, wherein the surface mount package is rectangular in shape as viewed from above, the surface mount package is provided with a plurality of leads projecting from sides of the rectangular shape, the antenna and the IC chip enclosed in the surface mount package are connected with each other through any of the leads except those which are adjacent to corners at which two sides of the rectangular shape are in contact.

3. The RFID tag according to claim 1, wherein the surface mount package is rectangular in shape as viewed from above, connection terminals are arranged on a bottom surface of the surface mount package, the antenna and the IC chip enclosed in the surface mount package are connected with each other through any of the connection terminals except those which are adjacent to corners at which two sides of the rectangular shape are in contact.

4. A method of manufacturing an RFID tag comprising an inlay which includes a base, an antenna formed on the base, an IC chip which is enclosed in a surface mount package and soldered to the antenna and which carries out radio communication through the antenna, and underfill which fills a gap between the base and the surface mount package, and a sheath protecting material enclosing the entire inlay, the method comprising the steps of:

printing a soldering paste on a portion of the base on which the antenna is formed, the portion being where the surface mount package is to be soldered;

aligning and mounting the surface mount package on the base;

connecting the surface mount package to the antenna on the base by soldering reflow;

injecting underfill into a gap between the base and the surface mount package;

hardening the underfill, thereby completing the inlay;

disposing a resin lower member which has a recess into which the inlay is fitted and which corresponds to a lower portion of the sheath protecting material, together with the inlay fitted into the recess of the lower member, into a mold having a gap corresponding to an outer shape of the sheath protecting material; and

molding the sheath protecting material by flowing resin corresponding to an upper portion of the sheath protecting material into the gap in the mold, thereby molding the upper portion and fusing the upper portion and the lower member together,

wherein where a thermal expansion coefficient of the surface mount package is defined as α

1,

a thermal expansion coefficient of the underfill is defined as α

2,

a thermal expansion coefficient of the base is defined as α

3, and

a thermal expansion coefficient of the sheath protecting material is defined as α

4, relations α

1<

α

2 and α

4<

α

3 are satisfied.