JP2005184309A - Surface acoustic wave device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized surface acoustic wave device with high reliability. <P>SOLUTION: A surface acoustic wave element 13 face-down mounted on a mount board 11 by metallic bumps 12 is covered by a resin film 14 and the mount face of the mount board 11 and the resin film 14 are closely adhered, and the thickness of the resin film 14 in contact with side faces of the surface acoustic wave element 13 is formed thinner than the thickness of the resin film 14 in contact with the rear side of the surface acoustic wave element 13 to thereby improve the reliability. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave device particularly used for a mobile phone or the like and a method for manufacturing the same.

  Conventionally, such a surface acoustic wave filter has a configuration as shown in FIG.

  The surface acoustic wave element 3 is mounted face down on the mounting surface of the mounting substrate 1 with gold bumps 2, covered with a resin film 4, and further covered with a metal film 5, thereby forming a surface acoustic wave filter. I was getting.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 2001-176955

  However, in the above configuration, the internal air expands due to the temperature at which the surface acoustic wave filter is soldered to the substrate, and the bump connection is broken by pushing up the surface acoustic wave element, or the edge portion of the resin film is There are problems that the metal film cannot be sufficiently covered, resulting in poor airtightness, and that the surface acoustic wave element generates heat and is destroyed when large electric power is applied to the filter.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above conventional problems and to provide a surface acoustic wave device having a small size and high reliability.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, there is provided a mounting surface of the mounting substrate in which a surface acoustic wave element is face-down mounted on a mounting surface of the mounting substrate, and the surface acoustic wave element and its periphery are mostly resin films. In the surface acoustic wave device in which the resin film is in close contact, the thickness of the resin film in contact with the side surface of the surface acoustic wave element is thinner than the thickness of the resin film in contact with the back surface of the surface acoustic wave element. The resin film exerts a force that presses the surface acoustic wave element toward the mounting substrate, and the effect that the bump connection is not easily broken even during heating such as soldering can be obtained.

  According to a second aspect of the present invention, a surface acoustic wave element is mounted face-down on a mounting surface of a mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film, and an elastic body is used to surround the surface acoustic wave element. By holding down, the mounting surface of the mounting substrate and the resin film are brought into close contact with each other while the resin film is stretched, and the thickness of the resin film in contact with the side surface of the surface acoustic wave element is determined by the thickness of the resin film in contact with the back surface of the surface acoustic wave element. It has a structure that is thinner than the thickness, which makes it possible for the resin film to press the surface acoustic wave element toward the mounting board, and the bump connection is difficult to break even during heating such as soldering. can get.

  According to a third aspect of the present invention, a surface acoustic wave element is mounted face-down on a mounting surface of a mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film, and the mounting surface of the mounting substrate and the resin film are covered. In the surface acoustic wave device in which the resin film and the mounting surface of the mounting substrate are covered with a metal film, the cross section of the end portion of the resin film forms an acute angle. The metal film can sufficiently cover the edge portion, and the effect of improving airtightness can be obtained.

  According to a fourth aspect of the present invention, a surface acoustic wave element is mounted face-down on a mounting surface of a mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film, and the mounting surface of the mounting substrate and the resin film are covered. And a part of the resin film in close contact with the mounting surface is removed so that the cross section of the end of the resin film around the surface acoustic wave element forms an acute angle, and then the mounting surface of the resin film and the mounting substrate Are covered with a metal film, whereby the edge portion of the resin film can be sufficiently covered by the metal film, and the air-tightness can be improved.

  According to a fifth aspect of the present invention, a surface acoustic wave element is mounted face down on a mounting surface of a mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film, and the mounting surface of the mounting substrate and the resin film are covered. In the surface acoustic wave device in which the resin film and the mounting surface of the mounting substrate are covered with a metal film, after removing a part of the resin film in contact with the back surface of the surface acoustic wave element, the resin film and the mounting substrate The mounting surface is covered with a metal film, so that the effect of effectively releasing heat generated by the surface acoustic wave element can be obtained.

  The surface acoustic wave device of the present invention improves the durability to heat such as soldering, improves the moisture resistance by improving the airtightness, and improves the reliability by reducing the influence of self-heating. There is an effect that can be.

(Embodiment 1)
Hereinafter, the first and second aspects of the present invention will be described with reference to the first embodiment.

  FIG. 1 is a cross-sectional view of a surface acoustic wave device according to Embodiment 1 of the present invention, and FIG. 2 is a diagram for explaining a manufacturing method.

  In FIG. 1, a surface acoustic wave element 13 made of lithium tantalate face down mounted on a mounting board 11 made of alumina with metal bumps 12 made of high-temperature solder is covered with a resin film 14 mainly composed of polyimide. The mounting surface of the mounting substrate 11 and the resin film 14 are brought into close contact with each other. The thickness of the resin film 14 in contact with the side surface of the surface acoustic wave element 13 is t1, and the thickness of the resin film 14 in contact with the back surface of the surface acoustic wave element 13 is. Let t2 be t1 <t2. By doing so, since the resin film 14 presses the surface acoustic wave element 13 toward the mounting substrate 11, the connection of the metal bumps 12 is not easily broken even when a thermal stress such as soldering is applied. Become.

  Next, the manufacturing method will be described. In FIG. 2 (A), the surface acoustic wave element 13 is mounted face-down on the mounting surface of the mounting substrate 11 at equal intervals, covered with a resin film 14, and heat is applied from above to the elastic surface made of hard rubber. By pressing the periphery of the surface acoustic wave element 13 with the body 15 while stretching the resin film 14, the mounting surface of the mounting substrate 11 and the resin film 14 are brought into close contact with each other, as shown in FIG. By dicing this, a surface acoustic wave device is obtained. Here, the surface acoustic wave element 13 having a thickness of about 0.35 mm and a chip size of about 2.0 mm × 1.6 mm was mounted on the mounting substrate 11 with an interval of about 0.8 mm. Since solder is used as the metal bumps 12, the mounting accuracy can be increased by the self-alignment effect. As the resin film 14, a film having a thickness of about 0.05 mm mainly composed of polyimide was used. From above, the resin film 14 is mounted by providing a relief at a portion corresponding to the surface acoustic wave element 13 and holding it with the elastic body 15 having a width of about 0.7 mm while the whole is heated to about 90 ° C. The substrate 11 was brought into close contact with the mounting surface. Here, the thickness t1 of the resin film 14 in contact with the side surface of the surface acoustic wave element 13 was set to about 70% of the thickness t2 of the resin film 14 in contact with the back surface of the surface acoustic wave element 13. If t1 is about 50% or less of t2, the resin film 14 is easily broken, and conversely if it is larger than about 90%, the effect of pressing the surface acoustic wave element 13 is reduced, so about 50% to 90%. Is desirable.

(Embodiment 2)
The invention according to claims 3 and 4 of the present invention will be described below using the second embodiment.

  FIG. 3 is a cross-sectional view of a surface acoustic wave device according to Embodiment 2 of the present invention, and FIG. 4 is a diagram for explaining a manufacturing method.

  In FIG. 3, the surface of the surface acoustic wave element 13 mounted on the mounting substrate 11 with the metal bumps 12 is covered with a resin film 14 so that the mounting surface of the mounting substrate 11 and the resin film 14 are in close contact with each other. Is covered with a metal film 16 made of titanium and nickel, and the angle R of the cross section of the end portion of the resin film 14 forms an acute angle. By doing in this way, the resin film 14 and its periphery are completely formed. It can be covered with the metal film 16, and reliability such as moisture resistance can be improved.

  Next, the manufacturing method will be described. In FIG. 4A, the surface acoustic wave element 13 is mounted face-down on the mounting substrate 11 and covered with the resin film 14. The steps up to here are performed in the same manner as in the first embodiment. Next, the resin film 14 brought into intimate contact with the mounting surface of the mounting substrate 11 is irradiated with a condensed carbon dioxide laser light, and a part of the resin film 14 is removed. At this time, irradiation is performed while changing the focal point of the laser beam so that the cross section of the remaining end portion of the resin film 14 forms about 45 °. Next, as shown in FIG. 4B, the entire mounting surface is deposited by sputtering as a metal film 16 with a thickness of about 0.1 μm titanium and about 5 μm nickel. By dicing this, a surface acoustic wave device is obtained. By doing in this way, the resin film 14 and its periphery can be completely covered with the metal film 16, and reliability, such as moisture resistance, can be improved.

  In order to further improve the reliability, it is desirable to make the metal film 16 thicker by plating after the metal film 16 is formed.

(Embodiment 3)
The invention described in claims 5 and 6 of the present invention will be described below using the third embodiment.

  FIG. 5 is a sectional view of a surface acoustic wave device according to Embodiment 3 of the present invention.

  First, in the same manner as in the first embodiment, the surface acoustic wave element 13 is face-down mounted on the mounting substrate 11 and covered with the resin film 14, but a part of the resin film 14 in contact with the back surface of the surface acoustic wave element 13 is used. In this way, the metal film 16 is in direct contact with the back surface of the surface acoustic wave element 13, so that a large electric power is applied to the surface acoustic wave device. Even if heat is generated, the heat can be released through the metal film 16, so that the power durability is improved, which is particularly effective for a surface acoustic wave duplexer.

  As a method of removing a part of the resin film 14 in a portion in contact with the back surface of the surface acoustic wave element 13, it can be carried out with almost no increase in man-hours by performing the same method as the method described in the second embodiment.

  Further, by providing a conductive layer on the back surface of the surface acoustic wave element 13 in advance, heat dissipation can be further improved.

  Furthermore, by connecting the metal film 16 to the ground, heat dissipation can be further improved, and the shielding effect can be enhanced.

  The surface acoustic wave device according to the present invention can improve reliability such as solder heat resistance, moisture resistance, and power resistance, and can also be applied to the communication field such as a mobile phone and the video field such as a television.

Sectional drawing of the surface acoustic wave device in Embodiment 1 of this invention The figure for demonstrating the manufacturing method of the surface acoustic wave device in Embodiment 1 of this invention Sectional drawing of the surface acoustic wave device in Embodiment 2 of this invention The figure for demonstrating the manufacturing method of the surface acoustic wave device in Embodiment 2 of this invention Sectional drawing of the surface acoustic wave device in Embodiment 3 of this invention Sectional view of a conventional surface acoustic wave device

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Mounting substrate 12 Metal bump 13 Surface acoustic wave element 14 Resin film 15 Elastic body 16 Metal film

Claims (6)

The mounting substrate, the surface acoustic wave element face-down mounted on the mounting surface, and a resin film covering the periphery thereof, and the thickness of the resin film in contact with the side surface of the surface acoustic wave element is the thickness of the surface acoustic wave element A surface acoustic wave device thinner than the thickness of the resin film in contact with the back surface. The surface acoustic wave element is mounted face down on the mounting surface of the mounting board, the surface acoustic wave element and its surroundings are covered with a resin film of a predetermined thickness, and the mounting surface of the mounting board and the resin film are in close contact with each other. A method for manufacturing a surface acoustic wave device, wherein a thickness of the resin film in contact with a side surface of the surface acoustic wave element is smaller than a thickness of the resin film in contact with a back surface of the surface acoustic wave element. A mounting substrate, a surface acoustic wave element face-down mounted on the mounting surface, a resin film covering the periphery thereof, and a metal film covering the resin film and the mounting surface of the mounting substrate, the mounting surface of the mounting substrate And a surface acoustic wave device in which the cross section of the end of the resin film forms an acute angle. A surface acoustic wave element is mounted face-down on the mounting surface of the mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film having a predetermined thickness, and the mounting surface of the mounting substrate and the resin film are adhered to each other, In the surface acoustic wave device in which the resin film and the mounting surface of the mounting substrate are covered with a metal film, the mounting surface of the mounting substrate and the cross section of the end portion of the resin film around the surface acoustic wave element form an acute angle. A method for producing a surface acoustic wave device in which a part of the resin film in close contact with the mounting surface is removed, and then the resin film and the mounting surface of the mounting substrate are covered with a metal film. A surface acoustic wave element is mounted face-down on the mounting surface of the mounting substrate, the surface acoustic wave element and its periphery are covered with a resin film having a predetermined thickness, and the mounting surface of the mounting substrate and the resin film are adhered to each other, In the surface acoustic wave device in which the resin film and the mounting surface of the mounting substrate are covered with a metal film, after removing a part of the resin film in contact with the back surface of the surface acoustic wave element, the resin film and the mounting substrate A method of manufacturing a surface acoustic wave device in which a mounting surface is covered with a metal film. The method for manufacturing a surface acoustic wave device according to claim 5, wherein a conductive layer is formed on the back surface of the surface acoustic wave element.

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