JP2004135192A - Surface-mount saw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent resin having high fluidity from entering an airtight space, to cause interference on SAW (surface acoustic wave) propagation, when screen-printing or coating using a dispenser of highly fluid resin with thixotropic ratio of 4.5 or larger, in order to seal a SAW chip outer surface with resin, by making the space between an SAW chip lower surface and a wiring board upper surface airtight. <P>SOLUTION: A surface-mount SAW device 1 comprises a wiring board 2, an SAW chip, and sealing resin 20. The SAW chip is equipped with an IDT (interdigital transducer) electrode 17 formed in a lower surface of a piezoelectric substrate 18, and a plurality of connecting pads 16 arranged on the piezoelectric substrate lower surface so that the IDT electrode is surrounded, and flip-chip mounted via a conductor bumped 10 on each land 5. The sealing resin 20 is filled in a ring fashion, between the wiring board and a cuff section of the SAW chip 15 so that an airtight space S is formed between an SAW chip lower surface and a wiring board upper surface. A resin capture annular groove 25, for surrounding each land, is formed on the insulating substrate upper surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface acoustic wave device having a structure in which a surface acoustic wave chip is mounted on a wiring board using bumps and then the surface acoustic wave chip is sealed with a resin. TECHNICAL FIELD The present invention relates to a surface-mount type surface acoustic wave device that solves a problem that occurs when sealing is performed by using a highly conductive resin.
[0002]
[Prior art]
A surface acoustic wave device (SAW device) has a configuration in which IDT (interdigital transducer) electrodes composed of comb-shaped electrode fingers are arranged on a piezoelectric substrate such as quartz, and for example, by applying a high-frequency electric field to the IDT electrodes. A filter characteristic is obtained by exciting a surface acoustic wave and converting the surface acoustic wave into a high-frequency electric field by a piezoelectric action.
WO 97/02596 discloses a surface mount type SAW device having a structure as shown in FIG. The SAW device 101 includes a wiring substrate 102 including an insulating substrate 103, a surface mounting external electrode 104 provided on the bottom of the insulating substrate 103, and a wiring pattern 105 provided on the upper surface of the insulating substrate 103; A SAW chip 115 composed of a piezoelectric substrate 118 provided on its lower surface with connection pads 116 electrically and mechanically connected via conductor bumps 110 and IDT electrodes 117, and a wiring substrate 101 including an upper surface of a wiring pattern 105; And a resin 120 that covers and integrates the side and top surfaces of the SAW chip 115. The resin 120 is formed by screen printing or the like so as to secure an airtight space S for propagation of the SAW, which is not filled with the resin, between the lower surface of the SAW chip 115 and the upper surface of the wiring board 102.
When the SAW device 101 has a small vertical and horizontal dimension of several mm, the SAW device 101 is mass-produced by batch processing using a large-area wiring board base material in which a plurality of wiring boards 102 are connected in a sheet shape. After flip chip mounting of the SAW chip 115 on each individual region on the material, the resin 120 is coated by screen printing using a predetermined mask or application by a dispenser. At this time, the resin 120 is filled in the valley between the SAW chips 115 to hermetically seal the space between the skirt of the SAW chip 115 and the upper surface of the wiring board, while being in close contact with the outer surface of the SAW chip. Since it needs to be coated, it needs to be printed in a liquid having a high fluidity. Specifically, the sealing resin 120 is applied to and filled in the gap between the skirt portion of the SAW chip and the wiring board by screen printing in a liquid state or filling with a dispenser. It is necessary to cover the entire outer surface of the removed SAW chip. At this time, when considering the ease of spreading the liquid resin when applying with a squeegee when printing with a mask, the workability at the time of extrusion with a dispenser, the adhesion to the object to be coated, etc., the fluidity is high. Low resin 120 is preferred. Specifically, printing using a resin 120 having a thixo ratio of 4.5 or less, which indicates the ratio between the resistance pressure of the liquid resin during low rotation and the resistance pressure of the liquid resin during high rotation, and filling with a dispenser are preferable.
However, the liquid resin 120 having a thixotropy ratio of 4.5 or less tends to enter an airtight space from a gap between the lower surface of the SAW chip and the upper surface of the wiring board, and when adhered to the IDT electrode 117, is a factor that hinders normal SAW propagation. Become.
[Patent Document 1] WO97 / 02596
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and in a SAW device having a structure in which a SAW chip is mounted face down via bumps on a wiring pattern on a wiring board for surface mounting, the lower surface of the SAW chip and the wiring board In order to seal the outer surface of the SAW chip with a resin while sealing the space between the upper surface and the upper surface, when a resin having a high thixotropy of 4.5 or more having high fluidity is coated by screen printing or coating with a dispenser, the flow is reduced. It is an object of the present invention to provide a surface-mount SAW device in which highly liquid resin is prevented from entering an airtight space and hindering SAW propagation.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes the following means.
A surface mounting type SAW device according to claim 1, wherein a wiring board comprising an insulating substrate, a surface mounting external electrode provided on a bottom portion of the insulating substrate, and a plurality of lands provided on an upper surface of the insulating substrate; A piezoelectric substrate, an IDT electrode formed on the lower surface of the piezoelectric substrate, and a plurality of connection pads arranged on the lower surface of the piezoelectric substrate so as to surround the IDT electrode and mounted on each of the lands via flip-chip via a conductive bump And a sealing resin that is annularly filled between the wiring board and the foot of the SAW chip so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring board. In the surface mount type SAW device provided, a resin capture annular groove surrounding each of the lands is formed on the upper surface of the insulating substrate.
When covering the outer surface of the SAW chip mounted face down on the wiring board with an insulating resin, it is necessary to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring board with the resin. It is necessary to strictly prevent a part of the resin from entering the airtight space and attaching to the IDT electrode. On the other hand, in order to coat the resin with a printing or dispenser, it is necessary to use a liquid resin having a sufficient fluidity, for example, a resin having a thixo ratio of 4.5 or less. It easily enters the inside, and the adhesion to the IDT electrode easily occurs.
In the present invention, a resin capture ring for preventing excess liquid resin from flowing toward the airtight space side by receiving a part of the resin that seals the space between the SAW chip bottom portion and the upper surface of the wiring board. Since the groove is formed on the insulating substrate, the above problem can be solved.
[0005]
According to a second aspect of the present invention, in the first aspect, an annular protrusion serving as a resin damming means is formed on the upper surface of the insulating substrate on the inner diameter side or the outer diameter side of the resin capture annular groove, and the upper surface of the annular protrusion is the SAW. It is characterized in that it faces the lower surface of the chip in a non-contact manner. In order to prevent the liquid resin from flowing into the airtight space side, an annular protrusion is provided outside the land on the insulating substrate, while preventing the liquid resin from moving over the annular protrusion and flowing inward. In addition, an annular groove is provided inside or outside the annular projection to capture excess resin and prevent intrusion into the inside of the annular projection.
According to a third aspect of the present invention, there is provided a wiring board including an insulating substrate, a surface mounting external electrode provided on a bottom portion of the insulating substrate, and a plurality of lands provided on an upper surface of the insulating substrate; a piezoelectric substrate; A SAW chip comprising: an IDT electrode formed on the lower surface; and a plurality of connection pads that are arranged on the lower surface of the piezoelectric substrate so as to surround the IDT electrode and are flip-chip mounted on the lands via conductive bumps. A sealing resin that is annularly filled between the wiring board and the foot of the SAW chip so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring board. , An upper surface of the insulating substrate includes a central recess provided with each of the lands on an inner bottom surface, and an annular outer wall surrounding the central recess. At least a part of the upper surface of the annular outer wall includes the SA. Characterized in that a positional relationship facing the chip bottom surface without contacting.
When the upper surface portion of the insulating substrate on which the land is provided is locally formed as a concave portion, and the liquid resin filled between the upper surface of the insulating substrate located outside the concave portion and the skirt portion of the SAW chip attempts to move to the airtight space side. In this method, this is trapped in a concave portion to prevent adhesion to the IDT electrode.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIGS. 1A and 1B are longitudinal sectional views of a surface-mount type surface acoustic wave device (hereinafter, referred to as a SAW device) according to an embodiment of the present invention, and FIG. It is a perspective view.
The SAW device 1 has a configuration in which a SAW chip 15 is mounted on a wiring board 2, and the outer surface of the SAW chip 15 is further covered with a sealing resin 20.
The wiring board 2 includes a flat insulating substrate 3 made of ceramic or the like, an external electrode 4 for surface mounting provided on the bottom of the insulating substrate 3, and an external electrode provided on the upper surface of the insulating substrate 3 via an internal conductor 6. And a plurality of lands (wiring patterns) 5 electrically connected to the lands 4.
The SAW chip 15 has connection pads 16 and IDT electrodes 17 electrically and mechanically connected to the lands 5 provided on the upper surface of the insulating substrate 3 via the conductive bumps 10 on the lower surface of a piezoelectric substrate 18 made of quartz or the like. Have. The connection pad 16 is arranged so as to surround the outer periphery of the IDT electrode 17. The IDT electrode 17 can obtain a filter characteristic by exciting a surface acoustic wave by applying a high frequency electric field and converting the surface acoustic wave into a high frequency electric field by a piezoelectric reaction. The IDT electrode 17 and the connection pad 16 are formed on the main surface of the piezoelectric substrate 18 by a fine processing technique such as photoetching.
The sealing resin 20 is coated over the outer surface except for the lower surface of the SAW chip 15 and the upper surface of the wiring substrate by screen printing or filling using a dispenser, thereby fixing the SAW chip 15 on the wiring substrate 2, and By filling the space between the bottom of the chip 15 (the outer peripheral edge of the lower surface) and the upper surface of the wiring substrate, an airtight space S is formed between the lower surface of the SAW chip 15 and the upper surface of the wiring substrate 2. As the sealing resin 20, a resin having a thixotropic ratio in a liquid state of 4.5 or less and having high fluidity suitable for printing, dispensing, and the like is used.
[0007]
A characteristic configuration of this embodiment is that a resin capture annular groove 25 surrounding each land 5 is formed on the upper surface of the insulating substrate 3 facing the lower surface of the SAW chip.
In the example of FIG. 1A, the resin capturing annular groove 25 is arranged on the upper surface of the insulating substrate 3 not facing the lower surface of the SAW chip 15, and in the example of FIG. 15 is disposed on the upper surface of the insulating substrate facing the lower surface. In any case, the liquid resin having high fluidity filled in the skirt of the SAW chip by printing from above or by the dispenser infiltrates into the hermetic space S due to a capillary phenomenon and adheres to the IDT electrode 17. An annular resin capture groove 25 is formed outside the land 5 so as to prevent the occurrence. That is, by adhering a part of the liquid resin that is going to enter the airtight space S from the space between the bottom of the SAW chip 15 and the upper surface of the wiring board into the annular groove 25, the adhesion to the IDT electrode 17 is prevented. I try to prevent it.
In addition, as shown by a dotted line in FIG. 1B, a resin capturing annular groove 25 a may be arranged inside the land 5. Alternatively, the resin capturing annular grooves 25, 25a may be provided on both the outside and the inside of the land 5, respectively.
[0008]
Next, FIGS. 2A and 2B are longitudinal cross-sectional views of SAW devices according to other embodiments of the present invention, respectively. The SAW device 1 according to these embodiments has the resin trap shown in FIG. A characteristic feature is that an annular projection 30 as a resin damping means is disposed inside or outside the annular groove 25, respectively.
First, the SAW device shown in FIG. 2A has an annular projection on the insulating substrate 3 inside the resin capturing annular groove 25 and corresponding to a position outside the land 5 with the upper surface not in contact with the lower surface of the SAW chip. 30 is provided. The annular projection 30 plays a role of damping the liquid resin 20 supplied by the printing or the dispenser when the liquid resin 20 tries to enter the airtight space S from the gap between the skirt portion of the SAW chip 15 and the upper surface of the wiring board. Fulfill. However, a case is conceivable in which the liquid resin infiltrates inside due to a capillary phenomenon from a minute gap between the upper surface of the annular protrusion 30 and the lower surface of the SAW chip 15. A resin trapping annular groove 25 is formed on the outside, and a portion of the liquid resin is trapped in the annular groove 25 in advance to prevent excess resin from moving over the annular projection 30 and moving inward.
In the embodiment shown in FIG. 2B, such a resin capturing annular groove 25 is arranged inside the annular projection 30. In this embodiment, when the liquid resin 20 intrudes from the gap between the upper surface of the annular protrusion 30 and the lower surface of the SAW chip 15, the liquid resin flowing down along the inner wall of the annular protrusion 30 is trapped by the resin capture ring. By reliably capturing by the groove 25, it is possible to further prevent intrusion into the inside and adhesion to the IDT electrode 17.
[0009]
Next, FIG. 3 is a longitudinal sectional view of a SAW device according to another embodiment of the present invention. A SAW device 1 according to this embodiment has a center having an upper surface of an insulating substrate 3 and lands 5 on an inner bottom surface. The configuration is characterized in that the concave portion 35 is provided, and at least a part of the upper surface 3a of the insulating substrate surrounding the central concave portion 35 has a positional relationship in which it faces the lower surface of the SAW chip 15 in a non-contact manner.
Since the land 5 is disposed on the inner bottom surface of the central recess 35, a conductor bump 10 having a larger diameter than usual is selected.
In this embodiment, even if the liquid resin 20 applied or filled by the printing or the dispenser penetrates inward from the gap between the skirt of the SAW chip 15 and the upper surface of the wiring board, the liquid resin 20 is surely kept in the central recess 35. , And are prevented from adhering to the IDT electrode 17. As long as the resin 20 does not adhere to the IDT electrode 17, the resin 20 adheres to the land 5 or the bump 10 without any problem in the function of the SAW device. On the other hand, the gap between the skirt portion of the SAW chip and the upper surface of the wiring board is securely sealed by the resin 20, so that the hermetic space S can be formed.
In particular, since the upper surface 3a of the insulating substrate, which corresponds to the periphery of the central recess 35, faces (overlaps) the lower surface of the SAW chip 15, the gap between the bottom of the SAW chip 15 and the upper surface of the wiring substrate is sealed. While the amount of resin required for this purpose can be sufficiently ensured, excess liquid resin that tends to penetrate inward can flow into the central recess 35.
[0010]
In the case where the SAW device 1 shown in each of the above embodiments is mass-produced by batch processing, a plurality of wiring boards having the resin capturing annular grooves 25 and 25a, the annular protrusion 30, or the central recess 35 as described above are required. A wiring board base material connected in a sheet shape is used. That is, the SAW chip 15 is flip-chip mounted on each wiring board piece constituting a wiring board base material (not shown), and then the liquid sealing resin 20 is screen-printed or applied by a dispenser to form each piece. It is supplied to the outer surface of the SAW chip and the valley between each SAW chip. At this time, even if the liquid resin attempts to infiltrate the airtight space S side beyond the bump 10 due to a variation in the amount of resin supplied to the valley between the SAW chips, the resin capturing annular grooves 25, 25a, the annular protrusion 30, or the center. The concave portions 35 exhibit their respective resin capturing functions, resin damping functions, and the like, thereby preventing the progress of the resin and preventing the resin from adhering to the IDT electrode.
After the resin is cured, the wiring board base material is diced into individual pieces, whereby individual SAW devices 1 are completed.
In each of the above embodiments, the sealing resin 20 is filled between the skirt portion of the SAW chip 15 and the wiring board to form an airtight space S, and the side and top surfaces of the SAW chip are covered with resin. However, the side surface or the upper surface of the SAW chip 15 does not necessarily have to be covered with the sealing resin 20.
[0011]
【The invention's effect】
As described above, according to the present invention, in order to seal the outer surface of the SAW chip with resin while sealing the space between the lower surface of the SAW chip provided with the IDT electrode and the upper surface of the wiring board, the thixotropy is 4.5 or more. When a resin having high fluidity is coated by screen printing or coating with a dispenser, it is possible to prevent the liquid resin having high fluidity from entering the airtight space and hindering SAW propagation.
That is, according to the surface mount type SAW device according to the first aspect of the present invention, by receiving a part of the resin that seals the space between the bottom of the SAW chip and the upper surface of the wiring board, the excess liquid resin is airtight. Since the resin capture annular groove for preventing the resin from flowing toward the space is formed on the insulating substrate, it is possible to prevent the liquid resin from adhering to the IDT electrode.
According to the invention of claim 2, while the annular projection is provided outside the land on the insulating substrate, the inside of the annular projection is prevented in order to prevent the liquid resin moving over the annular projection and flowing inward. Alternatively, an annular groove is provided on the outside to capture excess resin and prevent intrusion into the inside of the annular projection, so that the liquid resin can be prevented from flowing into the airtight space.
According to the third aspect of the present invention, the upper surface portion of the insulating substrate provided with the land is locally formed as a concave portion, and the liquid resin filled between the upper surface of the insulating substrate located outside the concave portion and the bottom portion of the SAW chip is formed. When an attempt is made to move to the airtight space side, this can be trapped in the recessed portion and the adhesion to the IDT electrode can be prevented.
[Brief description of the drawings]
1A and 1B are longitudinal sectional views of a surface-mounted surface acoustic wave device according to an embodiment of the present invention, and FIG. 1C is a perspective view of a wiring board.
FIGS. 2A and 2B are longitudinal sectional views of a SAW device according to another embodiment of the present invention, respectively.
FIG. 3 is a longitudinal sectional view of a SAW device according to another embodiment of the present invention.
FIG. 4 is a longitudinal sectional view of a conventional SAW device.
[Explanation of symbols]
Reference Signs List 1 surface acoustic wave device (SAW device), 2 wiring substrate, 3 insulating substrate, 4 external electrodes, 5 wiring pattern, 5a exposed area, 6 internal conductor, 10 conductor bump, 15 SAW (surface acoustic wave) chip, 16 connection pad , 17 IDT electrode, 18 piezoelectric substrate, 20 sealing resin, 25, 25a resin capturing annular groove, 30 annular projection, 35 central recess.

Claims (3)

An insulating substrate, an external electrode for surface mounting provided on the bottom of the insulating substrate, and a wiring board including a plurality of lands provided on an upper surface of the insulating substrate;
A piezoelectric substrate, an IDT electrode formed on the lower surface of the piezoelectric substrate, and a plurality of connection pads arranged on the lower surface of the piezoelectric substrate so as to surround the IDT electrode and mounted on each of the lands via flip-chip via a conductive bump A SAW chip comprising:
A sealing resin that is annularly filled between the wiring substrate and the bottom of the SAW chip so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring substrate;
In a surface mount type SAW device provided with
A surface mounting type SAW device, wherein a resin capturing annular groove surrounding each land is formed on the upper surface of the insulating substrate. On the upper surface of the insulating substrate on the inner diameter side or outer diameter side of the resin capturing annular groove, an annular projection as a resin damping means is formed, and the upper surface of the annular projection faces the lower surface of the SAW chip in a non-contact manner. The surface mount SAW device according to claim 1, wherein: An insulating substrate, an external electrode for surface mounting provided on the bottom of the insulating substrate, and a wiring board including a plurality of lands provided on an upper surface of the insulating substrate;
A piezoelectric substrate, an IDT electrode formed on the lower surface of the piezoelectric substrate, and a plurality of connection pads arranged on the lower surface of the piezoelectric substrate so as to surround the IDT electrode and mounted on each of the lands via flip-chip via a conductive bump A SAW chip comprising:
A sealing resin that is annularly filled between the wiring substrate and the bottom of the SAW chip so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring substrate;
In a surface mount type SAW device provided with
On the upper surface of the insulating substrate, a central recess provided with each land on the inner bottom surface, and an annular outer wall surrounding the central recess,
A surface-mounted SAW device, wherein at least a part of the upper surface of the annular outer wall faces the lower surface of the SAW chip in a non-contact manner.

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