JP7037843B1 - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent formation of a closed void which causes flux to remain around a solder bump. A surface acoustic wave device 1 has a piezoelectric substrate 2, an electrode pattern 3, a wall body 4, and a roof body 5. The roof body 5 and the wall body 4 are provided with a through hole 8 for a solder bump 7 for electrically connecting the electrode pattern 3 to the outside. The passage hole 8 is formed between the expanded hole portion 8a located in the roof body 5 and the reduced hole portion 8b having a smaller cross-sectional area than the expanded hole portion 8a located in the wall body 4. It is equipped with a step 8c. The expanded hole portion 8a is a distance from the central axis between a plurality of outer wall portions 8aa that increase the distance from the central axis by spacing them in a direction that orbits the central axis of the passing hole 8 and adjacent outer wall portions 8aa. Has an inner side wall portion smaller than the outer wall portion 8aa. [Selection diagram] Fig. 1

Description

The present invention relates to the improvement of surface acoustic wave devices.

There is a surface acoustic wave device with a WLP (Wafer Level Package) structure. The structure is shown in FIG. In a surface acoustic wave device having a WLP structure, a roof body 102 made of synthetic resin is supported on the one side of a piezoelectric substrate 100 having an electrode pattern including a comb-shaped electrode on one side via a wall body 101 made of synthetic resin. An internal space 103 (air cavity) is formed between these three parties.

The roof body 102 and the wall body 101 are formed with a passage hole 105 for solder bumps 104 for electrically connecting the electrode pattern to the outside. The passage hole 105 includes an expanded hole portion 105a located in the roof body 102 and a reduced hole portion 105b having a smaller cross-sectional area than the expanded hole portion 105a located in the wall body 101. It is provided with a step 106 formed in.

Here, the solder bumps are spheroidized by a reflow process after the cream solder is adhered to the one surface of the piezoelectric substrate 100 by printing through the through holes 105. That is, since the synthetic resin and the cream solder do not have an affinity with each other, the cream solder melted by the reflow process aggregates spherically due to the surface tension of the wall body 102 made of the synthetic resin in contact with the hole opening of the expanded hole portion 105a.

However, in the conventional surface acoustic wave device having a WLP structure, the expanded hole portion 105a has a simple circular shape as the cross-sectional contour shape of the expanded hole portion 105a in the direction orthogonal to the central axis of the passing hole 105. Met. Therefore, in the conventional surface acoustic wave device having a WLP structure, a closed void 107 is formed between the portion where the solder bump 104 and the hole opening of the expanded hole portion 105a are in contact with each other and the step 106. It was something that would end up.

The flux contained in the cream solder should be removed by a cleaning treatment after the reflow treatment, but since the void 107 is closed in the conventional surface acoustic wave device having a WLP structure, the flux in the void 107 is closed. It had a problem that the residue could not be removed.

The main problem to be solved by the present invention is to prevent the formation of closed voids that cause flux to remain around the solder bumps provided in this type of surface acoustic wave device.

In order to achieve the above object, in the present invention, a surface acoustic wave device is placed on one surface of a piezoelectric substrate having an electrode pattern including a comb-shaped electrode on one surface via a wall body made of synthetic resin. A surface acoustic wave device that supports a roof body made of synthetic resin and forms an internal space between these three parties.
A hole for passing a solder bump for electrically connecting the electrode pattern penetrating the roof body and the wall body to the outside is provided.
The passage hole has an expanded portion located in the roof body, a reduced hole portion having a smaller cross-sectional area than the expanded hole portion located in the wall body, and a step formed between both portions. I have
The expanded hole portion includes two or more outer wall portions that are spaced apart in a direction around the central axis of the passing hole to increase the distance from the central axis, and the central axis is between adjacent outer wall portions. It is assumed that it serves as an inner side wall portion that makes the distance from the outer wall portion smaller than that of the outer wall portion.

One aspect of the present invention is to form a groove along the central axis in the expanded hole portion so that the groove bottom side of the groove becomes the outer wall portion.

Further, a plurality of the grooves are formed as the inner side wall portion between the adjacent grooves in the direction of orbiting the central axis, and the inner side wall portion is formed into a virtual circular arc centered on the central axis. Forming along the line is one of the aspects of the present invention.

Further, the cross-sectional contour shape of the expanded hole portion in the direction orthogonal to the central axis is located on the side portion formed along the side of the virtual quadrangle centered on the central axis and on the corner side of the quadrangle. At the same time, it is formed so as to have a corner portion formed substantially along a virtual line segment that intersects the side portion at an angle of substantially 45 degrees, and the side portion constitutes the inner side wall portion. It is one of the aspects of the present invention that the corner portion constitutes the outer wall portion.

Further, it is one of the aspects of the present invention to make the thickness of the roof body thicker than the thickness of the wall body.

According to the present invention, the voids formed around the solder bumps provided in this type of surface acoustic wave device can be opened, and the flux remaining in the voids can be cleaned after the reflow treatment. It can be properly removed by processing.

Further, in constructing a module including a wiring board on which the surface acoustic wave device according to the present invention is mounted and a mold resin covering the mounting side of the wiring board, the mold resin can be allowed to enter the voids. Therefore, the present invention has the feature of improving the mechanical stability of the module thus configured.

FIG. 1 is a cross-sectional configuration diagram of a surface acoustic wave device (first example) according to an embodiment of the present invention. FIG. 2 is a plan view showing the formed portion of the passage hole of the solder bump of the first example, omitting the description of the solder bump. FIG. 3 is a cross-sectional configuration diagram at the position taken along the line AA in FIG. FIG. 4 is a cross-sectional configuration diagram taken along the line BB in FIG. FIG. 5 is a cross-sectional configuration diagram showing a step of providing a solder bump in the first example, and proceeds in the order of FIGS. (A), (b), and (c). FIG. 6 is a cross-sectional configuration diagram showing a process of generating a module configured by including the first example, and proceeds in the order of FIGS. (A), (b), (c), and (d). .. FIG. 7 is a plan view showing a portion where a passage hole for a solder bump of a surface acoustic wave device (second example) according to an embodiment of the present invention is formed, omitting the description of the solder bump. FIG. 8 is a plan view showing a portion where a passage hole for a solder bump of a surface acoustic wave device (third example) according to an embodiment of the present invention is formed, omitting the description of the solder bump. FIG. 9 is a cross-sectional configuration diagram of a surface acoustic wave device having a conventional WLP structure.

Hereinafter, the surface acoustic wave device 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 8. The surface acoustic wave device 1 according to this embodiment has a WLP (Wafer Level Package) structure.

The cross-sectional structure is shown in FIG. In the surface acoustic wave device 1 having a WLP structure, a roof made of synthetic resin is placed on the one side 2a of the piezoelectric substrate 2 in which an electrode pattern 3 including a comb-shaped electrode is formed on one side 2a via a wall body 4 made of synthetic resin. The body 5 is supported to form an internal space 6 (air cavity) between these three parties.

The piezoelectric substrate 2 typically has a quadrangular plate shape. In the WLP structure, the internal space 6 on the electrode pattern 3 is formed on the one surface 2a of the piezoelectric substrate 2 so as to surround the electrode pattern 3, and then the roof body 4 is formed on the wall body 4. It is formed by forming 5. In the illustrated example, the roof body 5 is formed so as to form a plate in which the outer peripheral portion is integrated with the protruding end of the wall body 4 from the piezoelectric substrate 2. The surface acoustic wave device 1 is formed so that the end surface 4a of the wall body 4 and the end surface 5a of the roof body 5 are positioned on a virtual plane including the end surface 2b along the thickness direction of the piezoelectric substrate 2. Has been done.

The roof body 5 and the wall body 4 are formed with through holes 8 for solder bumps 7 for electrically connecting the electrode pattern 3 to the outside. The passage hole 8 has the terminal portion 3a of the electrode pattern 3 positioned at the bottom of the hole and penetrates the roof body 5 and the wall body 4 in a direction orthogonal to one surface 2a of the piezoelectric substrate 2. A plurality of passing holes 8 are typically formed with a space between the passing holes 8 and the adjacent passing holes 8 in the direction of orbiting the internal space 6.

Each of the passing holes 8 has an expanded hole portion 8a located in the roof body 5 and a central axis x (passing hole 8 of the passing hole 8) of the passing hole 8 rather than the expanded hole portion 8a located in the wall body 4. It is provided with a reduced hole portion 8b that reduces the spatial cross-sectional area in the hole in a direction orthogonal to the continuous direction of the passing hole 8 passing through the center, and a step 8c formed between both portions 8a and 8b. .. The step 8c is formed so as to orbit the central axis x of the passing hole 8. The cross-sectional contour shape of the expanded hole portion 8a in the direction orthogonal to the central axis x is uniform at any position of the expanded hole portion 8a, and the cross-sectional contour shape of the reduced hole portion 8b in the direction orthogonal to the central axis x. Is uniform at any position of the reduced hole portion 8b.

Solder bumps 7 are formed in each of the passing holes 8. Each solder bump 7 has a base portion 7a located in the contracted hole portion 8b, a lower portion 7ba formed on the step 8c and located in the expanded hole portion 8a, and an upper portion protruding outward from the hole opening 8d of the through hole 8. It is provided with a spherical portion 7b provided with 7bb. FIG. 5 shows a main part of the solder bump 7 forming process.

First, a wall body 4 and a roof body 5 having passing holes 8 at predetermined positions are formed on the piezoelectric substrate 2 (step 1 / FIG. 5A).
Next, the cream solder 9 is attached to the one side 2a of the piezoelectric substrate 2 by printing through the through hole 8 (step 2 / FIG. 5 (b)).
After that, the solder bump 7 is formed by the cream solder 9 melted by the reflow process (step 3 / FIG. 5 (c)). The melted cream solder 9 aggregates in a spherical shape in contact with the hole 8d of the passage hole 8 of the wall body 4 made of synthetic resin, that is, in contact with the hole of the expanded hole portion 8a to form the spherical portion 7b.

In this embodiment, as shown in FIGS. 2, 7, and 8, the expanded hole portion 8a orbits the central axis x of the passing hole 8 (see FIG. 5A). The two or more outer wall portions 8aa that increase the distance from the central axis x at intervals are provided, and the distance from the central axis x is made smaller than the outer wall portion 8aa between the adjacent outer wall portions 8aa. The structure is such that the inner side wall portion is 8ab.

In this way, the solder bump 7 is formed in contact with the inner side wall portion 8ab, and the open gap 10 is formed between the solder bump 7 formed on the step 8c and the outer wall portion 8aa. be able to.
As a result, the flux remaining in the void 10 can be appropriately removed by the cleaning treatment after the reflow treatment.
Further, when the cream solder 9 is attached to the one side surface 2a of the piezoelectric substrate 2 through the through hole 8 by printing, air can be released from the gap 10 and the cream solder 9 can be printed appropriately and smoothly. It becomes.
Further, in constructing a module 11 (composite component) including a wiring board 11b on which the surface acoustic wave device 1 is mounted and a mold resin 11a covering the mounting side of the wiring board 11b, a mold is formed in the gap 10. The resin 11a can be inserted therein, and therefore has a feature of improving the mechanical stability of the module 11 thus configured.

The main part of the manufacturing process of the module 11 is shown in FIG.
First, the cream solder 9 is attached to the terminal portion 11c (see FIG. 6A) of the wiring board 11b by printing (step 1 / FIG. 6B).
Next, in a state where the solder bump 7 of the surface acoustic wave device 1 corresponding to the terminal portion 11c of step 1 is positioned, a reflow process is performed to electrically connect the solder bump 7 and the terminal portion 11c. (Step 2 / FIGS. 6 (b) to 6 (c)).
Finally, the mounting side of the wiring board 11b is covered with the mold resin 11a so that the surface acoustic wave device 1 is embedded in the mold resin 11a (step 3 / FIG. 6D).

If the cross-sectional contour shape of the expanded hole portion 8a is a simple circular shape, a closed void 10 is formed between the portion where the solder bump 7 and the hole opening of the expanded hole portion 8a are in contact with each other and the step 8c. I will let you. On the other hand, in the surface acoustic wave device 1 according to this embodiment, the cream solder 9 melted by the reflow process is formed in the hole 8d of the passage hole 8 of the wall body 4 made of synthetic resin, that is, the hole of the widened portion 8a. Of these, since the spherical portion 7b is formed by aggregating in a spherical shape in contact with the portion formed by the inner side wall portion 8ab, the space between the spherical portion 7b and the outer wall portion 8a of the expanded hole portion 8a is formed. The void 10 can be formed in the open state.

1 to 6 show a groove 12 formed along the central axis x in the expanded hole portion 8a, that is, in the hole wall of the passing hole 8 in the expanded hole portion 8a, and the bottom side of the groove 12 of the groove 12 is formed. A first example is shown in which the outer side wall portion is 8aa. In this first example, a plurality of the grooves 12 are formed as the inner side wall portion 8ab between the grooves 12 adjacent to each other in the direction around the central axis x, and the inner side wall portion 8ab is used as the central axis x. It is formed along the arc of a virtual circle centered on. The cross-sectional contour shape of the groove 12 in the direction orthogonal to the central axis x is a semicircular arc shape. Substantially the same distance is formed between the grooves 12 adjacent to each other in the direction around the central axis x at any position. Further, in this first example, the groove 12 is positioned at each position facing the central axis x at any position in the direction of orbiting the central axis x.
As a result, in this first example, in a state where the inner side wall portion 8ab is linearly in contact with the spherical portion 7b of the solder bump 7, the adjacent inner side wall portions 8ab are opened in the direction around the central axis x. It is possible to form the soldered void 10.
For example, the maximum diameter L1 (see FIG. 4) of the spherical portion 7b of the solder bump 7 is 100 μm, the reduced diameter portion is a circular hole, the hole diameter L2 (see FIG. 2) is 80 μm, and the central axis x of the expanded hole portion 8a. The distance L3 (see FIG. 3) between the inner side wall portions 8ab located at the opposite position with the center axis x in between is 90 μm, and the distance L4 (see FIG. 4) between the outer wall portions 8aa at the opposite positions with the central axis x of the expanded hole portion 8a sandwiched. (See) is set to 110 μm, and an open portion of a gap 10 of 10 μm can be formed between the spherical portion 7b and the outer wall portion 8a of the expanded hole portion 8a.

FIG. 7 shows a second example in which the groove 12 is formed so as to include a pair of groove side walls 12b and a groove bottom wall 12a intersecting the groove side walls 12b. Since the other configurations of this second example are substantially the same as those of the first example, the description thereof will be omitted.

FIG. 8 is formed so that the cross-sectional contour shape of the expanded hole portion 8a in the direction orthogonal to the central axis x is along the side of a virtual quadrangle y (see FIG. 8) centered on the central axis x. It is formed so as to have a side portion 13 and a corner portion 14 located at a corner of the quadrangle y, the side portion 13 constitutes the inner side wall portion 8ab, and the corner portion 14 constitutes the outer wall portion 8aa. The third example is shown. In the illustrated example, the intersection of the two diagonal lines of the virtual quadrangle y is set to be the center of the central axis x. Further, the corner portion 14 is formed so as to substantially follow a virtual line segment z (see FIG. 8) that intersects the side portion 13 at an angle of substantially 45 degrees, and is orthogonal to the central axis x. The cross-sectional contour shape of the expanded hole portion 8a in the direction is substantially octagonal.
As a result, in this third example, in a state where the spherical portions 7b of the solder bumps 7 are in dot contact with the inner side wall portions 8ab at the four locations, the contact portions adjacent to each other in the direction of orbiting the central axis x. It is possible to form the open voids 10 in each of the solders.

Further, in the embodiment described above, the roof body 5 (orthogonal to one surface 2a of the piezoelectric element) is orthogonal to the thickness of the wall body 4 (dimension of the wall body 4 in the direction orthogonal to one surface 2a of the piezoelectric element). The thickness of the facing roof body 5) is made thicker. In this case, as described above, when the cream solder 9 is adhered (step 2 / FIG. 5 (b)) on the one side surface 2a of the piezoelectric substrate 2 by printing through the through hole 8, the expanded hole portion is formed. It becomes easy to increase the amount of the cream solder 9 in 8a.

As a matter of course, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the object of the present invention.

1 Surface Acoustic Wave Device 2 Surface Acoustic Wave Device 2 One Side 2b End Face 3 Electrode Pattern 3a Terminal Part 4 Wall Body 4a End Face 5 Roof Body 5a End Face 6 Internal Space 7 Solder Bump 7a Base 7b Spherical Part 7ba Bottom 7bb Top 8 Passing Hole 8a 8aa Outer side wall part 8ab Inner side wall part 8b Shrink hole part 8c Step 8d Hole mouth 9 Cream solder 10 Void 11 Module 11a Mold resin 11b Wiring board 11c Terminal part 12 Groove 12a Groove bottom wall 12b Groove side wall 13 Side part 14 Corner part x Central axis y virtual rectangle z virtual line segment

Claims (5)

A roof body made of synthetic resin is supported on the one side of the piezoelectric substrate having an electrode pattern including a comb-shaped electrode on one side via a wall body made of synthetic resin, and an internal space is formed between these three parties. Surface acoustic wave device
A hole for passing a solder bump for electrically connecting the electrode pattern penetrating the roof body and the wall body to the outside is provided.
The passage hole has an expanded portion located in the roof body, a reduced hole portion having a smaller cross-sectional area than the expanded hole portion located in the wall body, and a step formed between both portions. I have
The expanded hole portion includes two or more outer wall portions that are spaced apart in a direction around the central axis of the passing hole to increase the distance from the central axis, and the central axis is between adjacent outer wall portions. A surface acoustic wave device that serves as an inner side wall portion that makes the distance from the outer wall portion smaller than that of the outer wall portion. The surface acoustic wave device according to claim 1, wherein a groove is formed in the expanded hole portion along the central axis so that the groove bottom side of the groove becomes the outer wall portion. A plurality of the grooves are formed as the inner side wall portion between the adjacent grooves in the direction rotating around the central axis, and the inner side wall portion is formed along the arc of a virtual circle centered on the central axis. The surface acoustic wave device according to claim 2, which is formed in. The cross-sectional contour shape of the expanded hole portion in the direction orthogonal to the central axis is located on the side portion formed along the side of the virtual quadrangle centered on the central axis and on the corner side of the quadrangle. It is formed so as to have a corner portion formed substantially along a virtual line segment that intersects the side portion at an angle of substantially 45 degrees, and the side portion constitutes the inner side wall portion. The surface elastic wave device according to claim 1, wherein the corner portion constitutes the outer wall portion. The surface acoustic wave device according to any one of claims 1 to 4, wherein the thickness of the roof body is made thicker than the thickness of the wall body.

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