JP2013065997A - Surface acoustic wave device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device which is extremely small and easily manufactured.SOLUTION: A surface acoustic wave device 11 of this invention comprises: a piezoelectric substrate 12; multiple interdigital electrodes 13 provided on a surface of the piezoelectric substrate 12; wiring 14 connecting with the multiple interdigital electrodes; an element cover 16 which is provided on the piezoelectric substrate and covers the interdigital electrodes through a space 15; a first connection electrode 17 ranging from an area on the wiring to an upper surface of the element cover through a side surface of the element cover; a sealing resin 19 covering the piezoelectric substrate, the element cover, and the first connection electrode; and an external terminal 20 provided on a surface of the sealing resin; and a second connection electrode 18 which penetrates through the sealing resin and connects the first connection electrode with the external electrode.

Description

  The present invention relates to a surface acoustic wave device and a method for manufacturing the same.

  FIG. 6 schematically shows a cross section of a conventional surface acoustic wave device 1.

  In FIG. 6, the surface acoustic wave device 1 includes a comb-shaped electrode 3, a wiring 4, a side wall 5 surrounding the comb-shaped electrode 3, and a space 6 excited by the comb-shaped electrode 3 surrounded by the side wall 5. A lid 7 that is provided on the upper surface of the side wall 5 and covers the space 6 from above, a sealing resin 8 that seals from above the lid 7, a connection electrode 9 that penetrates the sealing resin 8, and a connection electrode 9 and a terminal electrode 10 provided on the upper surface of the substrate.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2001-185976 A

  However, the above-described conventional surface acoustic wave device 1 has a problem that it has a complicated structure and thus requires a complicated manufacturing process and is not easy to manufacture.

  An object of the present invention is to provide a surface acoustic wave device that is extremely small and can be easily manufactured.

  In order to achieve the above object, the present invention provides a piezoelectric substrate, a plurality of comb-shaped electrodes provided on the surface of the piezoelectric substrate, wirings connected to the plurality of comb-shaped electrodes, and the piezoelectric substrate. An element cover that covers the comb-shaped electrode through a space, a first connection electrode that extends from above the wiring to a top surface of the element cover via a side surface of the element cover, the piezoelectric substrate, and the element A sealing resin covering the cover and the first connection electrode; an external terminal provided on the surface of the sealing resin; and the first connection electrode and the external terminal penetrating the sealing resin. And a second connection electrode to be connected.

  Further, the present invention provides a process for forming a plurality of comb-shaped electrodes and wirings connected to the comb-shaped electrodes on the upper surface of the piezoelectric substrate, and the photosensitive resin of the laminated film formed by laminating a base film and a photosensitive resin. A step of forming a recess by pressing a mold on the surface, and bonding the photosensitive resin to the surface of the piezoelectric substrate so that the recess forms a space on the comb-shaped electrode on the upper surface of the piezoelectric substrate, An element cover is formed by obtaining a laminate of the piezoelectric substrate and the laminate film, exposing the photosensitive resin, and peeling the base film from the laminate and developing the photosensitive resin. And a process for performing.

  By having the above configuration, the surface acoustic wave device of the present invention has an effect that it is extremely small and can be easily manufactured.

Sectional drawing which shows typically the surface acoustic wave apparatus in one embodiment of this invention Cross-sectional view of relevant parts schematically showing the surface acoustic wave device (A)-(c) Manufacturing process figure which showed the manufacturing method of the surface acoustic wave apparatus typically (A)-(c) Manufacturing process figure which showed the manufacturing method of the surface acoustic wave apparatus typically (A)-(c) Manufacturing process figure which showed the manufacturing method of the surface acoustic wave apparatus typically Sectional drawing which shows the conventional surface acoustic wave apparatus typically

  A surface acoustic wave device according to an embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view schematically showing a surface acoustic wave device according to an embodiment of the present invention, and FIG.

  In FIG. 1, the surface acoustic wave device 11 includes a piezoelectric substrate 12, a comb electrode 13, a wiring 14, a space 15, an element cover 16, a first connection electrode 17, a second connection electrode 18, A sealing resin 19 and an external terminal 20 are provided.

  The piezoelectric substrate 12 is made of single-crystal lithium tantalate with rotational Y-cut X propagation, and has a thickness of about 100 to 350 μm.

  The comb-shaped electrode 13 is made of a metal mainly composed of aluminum formed on the surface of the piezoelectric substrate 12, and a surface acoustic wave is excited on the surface of the piezoelectric substrate 12 by applying a voltage to the comb-shaped electrode 13. A protective film made of a dielectric material such as silicon oxide is formed on the surface of the comb electrode 13 as necessary.

  The wiring 14 is made of a conductor formed on the surface of the piezoelectric substrate 12 and is electrically connected to the comb-shaped electrode 13.

  The space 15 is a sealed cavity provided above the comb-shaped electrode 13 for exciting the surface acoustic wave.

  The element cover 16 covers and seals the comb-shaped electrode 13 through the space 15, and is made of a single body obtained by curing a photosensitive epoxy resin or a photosensitive polyimide resin.

  A protective film made of a dielectric material such as silicon oxide or another bonding member may be provided at the interface between the element cover 16 and the piezoelectric substrate 12 and the interface between the element cover 16 and the wiring 14, but other bonding members may be used. Alternatively, the element cover 16 may be joined directly.

  An outer peripheral side surface of the element cover 16 is an outer side surface 21, and a side surface facing the space 15 of the element cover 16 is an inner side surface 22. In the element cover 16, a portion surrounding the space 15 in the horizontal direction is the side wall portion 23, and a portion covering the space 15 and a portion extending in the horizontal direction are the top plate portion 24.

  As shown in FIG. 2, when the angle formed by the outer surface 21 of the element cover 16 and the piezoelectric substrate 12 is A degrees, and the angle formed by the inner surface 22 of the element cover 16 and the piezoelectric substrate 12 is B degrees. A <90 ° <B and A <180 ° -B. As shown in FIG. 2, C <D, where C is the thickness of the side wall 23 of the element cover 16 and D is the thickness of the element cover 16 in the top plate 24. Further, when the thickness in the horizontal direction of the boundary between the side wall portion 23 and the top plate portion 24 is E, D <E.

  The first connection electrode 17 is a conductor that extends from the upper surface of the wiring 14 to the upper surface of the element cover 16 via the outer surface 21 of the element cover 16, and is formed by electrolytic copper plating.

  The second connection electrode 18 is a conductor that penetrates the sealing resin 19 and connects the first connection electrode 17 and the external terminal 20, and is formed by electrolytic copper plating, electroless copper plating, or filling with a conductive paste. It is a thing. The second connection electrode 18 can improve the strength of the surface acoustic wave device 11 by penetrating the sealing resin 19 above the side wall portion 23 of the element cover 16.

  The sealing resin 19 is obtained by curing a thermosetting epoxy resin that seals the element cover 16 and the first connection electrode 17 on the piezoelectric substrate 12 and contains a filler such as silica. It is a thing.

  The external terminal 20 is a conductor provided on the upper surface of the second connection electrode 18 and the upper surface of the sealing resin 19 around it, and electrically connects the surface acoustic wave device 11 to an external printed board (not shown). It is a terminal electrode.

  The surface acoustic wave device 11 configured as described above is called a wafer level CSP, and can realize an extremely small size having an occupied area equivalent to that of the piezoelectric substrate 12 on which the surface acoustic wave element is formed. .

  In the surface acoustic wave device 11 according to the present invention, the angle formed between the outer surface 21 of the element cover 16 and the piezoelectric substrate 12 is A degrees, and the angle formed between the inner surface 22 of the element cover 16 and the piezoelectric substrate 12 is B. In this case, A <90 ° <B and A <180 ° -B. In this way, by making the inclination angle of the outer surface 21 smaller than the inclination angle of the inner surface 22, the disconnection of the first connection electrode 17 formed along the outer surface 21 is prevented, and the connection is ensured. In addition, the inclination angle of the inner side surface 22 can be made more vertical, the area occupied by the inclined portion of the inner side surface 22 can be reduced, and the surface acoustic wave device 11 can be downsized. be able to.

  In the surface acoustic wave device 11 of the present invention, the inclination of the outer surface 21 is a forward inclination (0 ° <A <90 °) and the inclination of the inner surface 22 is a reverse inclination (90 ° <B <180 °). Thus, the distance between the outer surface 21 and the inner surface 22 can be secured while maintaining the inclination angle of the outer surface 21, and the strength of the element cover 16 can be maintained with a small occupied area. . That is, if both the outer side surface 21 and the inner side surface 22 are forwardly inclined, the side wall 23 between the outer side surface 21 and the inner side surface 22 does not secure a large area on the bottom surface. The area cannot be secured. In one embodiment of the present invention, the outer surface 21 is inclined forward (0 ° <A <90 °), and the inner surface 22 is inclined backward (90 ° <B <180 °). The side wall portion 23 between the outer side surface 21 and the inner side surface 22 can ensure a sufficient cross-sectional area at the upper portion without requiring a large cross-sectional area at the bottom surface, and can maintain mechanical strength. Is.

  The surface acoustic wave device 11 of the present invention secures the strength of the top plate portion 24 by making the thickness D of the top plate portion 24 of the element cover 16 thicker than the thickness C of the side wall portion 23 of the element cover 16. Since the contact with the comb electrode 13 due to the bending of the top plate portion 24 can be prevented, the characteristics of the surface acoustic wave device 11 can be stabilized.

  Further, in the surface acoustic wave device 11 of the present invention, not only the top plate portion 24 above the space 15 but also the thickness D of the top plate portion 24 above the side wall portion 23 is made thicker than the thickness C of the side wall portion 23. As a result, the mechanical strength of the element cover 16 can be made stronger, and the characteristics of the surface acoustic wave device 11 can be stabilized.

  In the surface acoustic wave device 11 of the present invention, the horizontal thickness E of the boundary between the side wall portion 23 and the top plate portion 24 of the element cover 16 is made larger than the thickness D of the top plate portion 24 of the element cover 16. As a result, the mechanical strength of the element cover 16 can be made stronger, and the characteristics of the surface acoustic wave device 11 can be stabilized.

  In particular, when sealing the transfer mold or the like after mounting the surface acoustic wave device 11 on a printed circuit board, the resin injection pressure of the transfer mold is applied to the upper surface of the surface acoustic wave device 11 and the top plate portion 24 bends. However, by making the thickness D of the top plate portion 24 thicker than the thickness C of the side wall portion 23, the deflection of the top plate portion 24 can be suppressed, and the surface acoustic wave device 11 problems can be suppressed.

  Further, when the transfer mold or the like is resin-sealed after the surface acoustic wave device 11 is mounted on the printed board, the thickness D of the top plate portion 24 above the side wall portion 23 is made thicker than the thickness C of the side wall portion 23. Thus, the stress acting in the direction of peeling the first connection electrode 17 and the element cover 16 caused by resin sealing can be relaxed, and the reliability of the surface acoustic wave device 11 can be improved.

  Further, when the transfer mold or the like is resin-sealed after the surface acoustic wave device 11 is mounted on the printed circuit board, the horizontal thickness E between the side wall portion 23 and the top plate portion 24 is thicker than the thickness D of the top plate portion 24. By doing so, the stress acting in the direction of peeling the first connection electrode 17 and the element cover 16 caused by resin sealing can be relaxed, and the reliability of the surface acoustic wave device 11 can be improved.

  Furthermore, the surface acoustic wave device 11 according to the present invention includes a first connection electrode 17 made of electrolytic copper plating on the outer surface 21 and the upper surface of the element cover 16 having an inclination angle A on the outer periphery and the wiring 14 around the element cover 16. As a result, the mechanical strength of the element cover 16 can be ensured, and the characteristics of the surface acoustic wave device 11 can be stabilized.

  In addition, the surface acoustic wave device 11 of the present invention can easily ensure the airtightness of the space 15 by configuring the element cover 16 as a single body having no joint between the side wall portion and the top plate portion. Can do.

  Further, the surface acoustic wave device 11 of the present invention improves the reliability of the surface acoustic wave device 11 because the second connection electrode 18 penetrates the sealing resin 19 in the upper part of the side wall portion 23 of the element cover 16. be able to. That is, when a reliability test such as a heat cycle is performed after the surface acoustic wave device 11 is mounted on the printed circuit board, a stress in the tensile direction is applied to the external terminal 20 due to the difference in linear expansion coefficient between the printed circuit board and the surface acoustic wave device 11. It takes. At this time, if the wiring 14 on the piezoelectric substrate 12 and the external terminal 20 are connected by a vertical columnar connection electrode, the stress reaches the piezoelectric substrate 12 through the external terminal 20, and the external terminal 20 is disconnected or on the piezoelectric substrate 12. Disconnection between the wiring 14 and the connection electrode occurs. On the other hand, when forming the 2nd connection electrode 18 on the side wall part 23 of the resin-made element covers 16, the 1st connection electrode 17 which passed through the deformation | transformation of the resin which comprises the side wall part 23, and the outer surface 21 is provided. Since the stress can be absorbed by the deformation, stable reliability can be ensured. Further, by providing the second connection electrode 18 on the upper portion of the side wall portion 23 of the element cover 16, the side wall portion 23 of the element cover 16 is fixed to the printed board via the external terminal 20 and the second connection electrode 18. In addition, since the shape change of the element cover 16 can be suppressed, the reliability of the surface acoustic wave device 11 can be improved.

  Next, a method for manufacturing the surface acoustic wave device 11 according to one embodiment of the present invention will be described with reference to the drawings.

  3 (a) to 3 (c), 4 (a) to (c), and 5 (a) to 5 (c) schematically show the manufacturing process of the surface acoustic wave device 11 according to the embodiment of the present invention. It is the manufacturing process figure shown.

  First, as shown in FIG. 3A, a laminated film 27 is prepared in which an uncured polyimide-based photosensitive resin 26 is laminated on a transparent resin base film 25.

  Next, as shown in FIG. 3B, a depression 29 is formed by pressing the laminated film 27 on the mold 28 on the mold 28 side, and the photosensitive resin 26 is primarily cured.

  Next, a metal thin film is formed on the surface of the piezoelectric substrate 12, and a plurality of comb-shaped electrodes 13 and wirings 14 are pattern-formed by using a photolithography technique as shown in FIG.

  Next, the concave portion 29 of the laminated film 27 is faced to the piezoelectric substrate 12 and pressed from the back surface to join the laminated film 27 to the upper surface of the piezoelectric substrate 12, and as shown in FIG. A laminate of the piezoelectric substrate 12 is obtained. Here, a sealed space 15 for exciting the comb electrode 13 is formed by the recess 29.

  Next, the photosensitive resin 26 is exposed from above the laminated film 27 using an exposure mask, then the base film 25 is peeled from the laminated body of the laminated film 27 and the piezoelectric substrate 12, and the photosensitive resin 26 is developed. Next, by secondary curing, an element cover 16 is formed on the upper surface of the piezoelectric substrate 12 as shown in FIG. By this step, the outer surface 21 of the element cover 16 is formed by photolithography.

  Next, as shown in FIG. 4C, the first connection electrode 17 extending from the wiring 14 on the upper surface of the piezoelectric substrate 12 to the upper surface of the element cover 16 via the outer surface 21 of the element cover 16 is electroplated. To form.

  Next, as shown in FIG. 5A, sealing is performed from above the piezoelectric substrate 12 with a thermosetting sealing resin 19.

  Next, as shown in FIG. 5B, a through hole 30 is formed from the upper surface of the sealing resin 19 to the first connection electrode 17 on the element cover 16.

  Next, as shown in FIG. 5C, the second connection electrode 18 filling the inside of the through hole 30, the outer surface covering the upper surface of the second connection electrode 18 and the upper surface of the sealing resin 19 around it. Terminal 20 is formed.

  As described above, in the surface acoustic wave device 11 of the present invention, the element cover 16 is formed of an integral product of a cured product of a photosensitive resin, and the concave portion 29 is formed by the mold 28, so that one-time photolithography The element cover 16 can be formed by a process, and the conventional photolithography process required two or more times to form the element cover. However, the manufacturing process can be greatly reduced, and the surface acoustic wave device can be easily formed. 11 can be manufactured.

  Further, since the surface acoustic wave device 11 of the present invention is bonded to the upper surface of the piezoelectric substrate 12 by pressing the photosensitive resin 26 before secondary curing from the back surface, it depends on the presence or absence of the wiring 14 on the piezoelectric substrate 12. It can absorb unevenness.

  Further, since the surface acoustic wave device 11 of the present invention is bonded to the upper surface of the piezoelectric substrate 12 by pressing the photosensitive resin 26 before secondary curing from the back surface, the upper surface of the element cover 16 becomes flat, and the outer peripheral portion Since the element cover 16 having a sufficient thickness can be formed, the mechanical strength at the outer periphery of the element cover 16 can be ensured, and the highly reliable surface acoustic wave device 11 can be obtained.

  In addition, the surface acoustic wave device 11 of the present invention presses the photosensitive resin 26 before the secondary curing, directly adheres to the upper surface of the piezoelectric substrate 12, and has a sufficient bonding force by performing the secondary curing in the subsequent process. Therefore, there is no need for a separate process using another adhesive member, and man-hours and members can be reduced.

  The surface acoustic wave device according to the present invention is useful in a high-frequency filter, a duplexer, a duplexer, etc. used mainly in mobile communication equipment.

DESCRIPTION OF SYMBOLS 11 Surface acoustic wave apparatus 12 Piezoelectric substrate 13 Comb electrode 14 Wiring 15 Space 16 Element cover 17 1st connection electrode 18 2nd connection electrode 19 Sealing resin 20 External terminal 21 Outer side surface 22 Inner side surface 23 Side wall part 24 Top plate part 25 Base film 26 Photosensitive resin 27 Laminated film 28 Mold 29 Recess

Claims (8)

Piezoelectric substrate, a plurality of comb electrodes provided on the surface of the piezoelectric substrate, wiring connected to the plurality of comb electrodes, and provided on the piezoelectric substrate and covering the comb electrodes through a space An element cover, a first connection electrode that extends from above the wiring via the side surface of the element cover to the upper surface of the element cover, and a seal that covers the piezoelectric substrate, the element cover, and the first connection electrode. Elasticity provided with a stop resin, an external terminal provided on the surface of the sealing resin, and a second connection electrode that penetrates the sealing resin and connects the first connection electrode and the external terminal Surface wave device. The surface acoustic wave device according to claim 1, wherein the second connection electrode penetrates the sealing resin above a side wall portion of the element cover. When the angle formed between the outer surface of the element cover and the piezoelectric substrate is A degrees and the angle formed between the inner surface of the element cover and the piezoelectric substrate is B degrees,
A <90 ° <B, A <180 ° -B
The surface acoustic wave device according to claim 1, wherein: The surface acoustic wave device according to claim 1, wherein the thickness of the top plate portion of the element cover is larger than the thickness of the side wall portion of the element cover. The surface acoustic wave device according to claim 1, wherein a thickness in a horizontal direction of a boundary between the side wall portion and the top plate portion of the element cover is larger than a thickness of the top plate portion of the element cover. The surface acoustic wave device according to claim 1, wherein the element cover is made of an integral body of a cured photosensitive resin. A step of forming a plurality of comb-shaped electrodes and wiring connected to the comb-shaped electrodes on the upper surface of the piezoelectric substrate, and pressing the mold against the surface of the photosensitive resin of the laminated film formed by laminating the base film and the photosensitive resin Forming the recesses, and laminating the photosensitive resin on the surface of the piezoelectric substrate so that the recesses form a space on the comb-shaped electrode on the upper surface of the piezoelectric substrate. A step of obtaining a laminate with a film, a step of exposing the photosensitive resin, and a step of forming an element cover by peeling the base film from the laminate and developing the photosensitive resin. A method of manufacturing a surface acoustic wave device. Forming a first connection electrode from above the wiring to the upper surface of the element cover via a side surface of the element cover; and an upper surface of the piezoelectric substrate, the element cover, and the first connection electrode. A step of covering with the sealing resin, a step of penetrating the sealing resin and forming a hole from the upper surface of the sealing resin to the first connection electrode, and the first connection electrode via the hole The method further comprises: forming a second connection electrode extending from the upper surface of the sealing resin to the upper surface of the sealing resin; and forming an external terminal connected to the second connection electrode on the upper surface of the sealing resin. A method for producing a surface acoustic wave device according to claim 7.

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