JP2006229632A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an SAW device whose reliability and mass productivity is improved, where an SAW chip flip-chip mounted through a conductor bump on a mounting substrate is sealed with resin from the outer surface of the SAW chip to the upper face of the mounting substrate and an air-tight space is formed between the SAW chip and the mounting substrate. <P>SOLUTION: This surface acoustic wave device is provided with an SAW chip 1 where an IDT electrode 3 and a connection pad 4 are arranged on a piezoelectric substrate 2, and a dam 21 constituted of a metal or an alloy is formed in an outer periphery excluding an SAW exciting section and a mounting substrate 11 equipped with an external electrode terminal 13 for surface mounting at the bottom section of an insulating substrate 12 and a wiring pattern 14 conducted to the external electrode terminal 13, and connected to a connection pad. The connection pad 4 and the wiring pattern 14 are flip-flop mounted through a conductor bump 22 and are sealed with sealing resin 31 from the outer surface of the SAW chip 1 to the upper face of the mounting substrate 11. The dam 21 is formed so as not to be brought into contact with the mounting substrate 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a surface acoustic wave chip is flip-chip mounted on a mounting substrate via a conductor bump, resin-sealed from the outer surface of the surface acoustic wave chip to the upper surface of the mounting substrate, and an airtight space between the mounting substrate and the SAW chip. The present invention relates to a surface-mount type surface acoustic wave device in which is formed.

  As a small packaging technology called CSP (Chip Size Package) is generalized in semiconductor parts, surface acoustic wave (hereinafter referred to as SAW) devices can be easily downsized and batch-type manufacturing can be performed. From the viewpoint of improving productivity by a method, a production method using CSP technology has been introduced. In addition, the CSP technique mainly uses a sealing method mainly using a resin.

  Hereinafter, the prior art of the SAW device using the CSP technology will be described. FIG. 9 shows a SAW device disclosed in Japanese Patent Application Laid-Open No. 2004-64599. In the SAW chip 101, an IDT electrode 103 for exciting SAW and a connection pad 104 are arranged on a piezoelectric substrate 102, and an annular outer peripheral electrode 105 is provided so as to surround the IDT electrode 103 and the connection pad 104. The mounting substrate 111 captures the external terminal electrode 113 for surface mounting at the bottom of the insulating substrate 112, the wiring pattern 114 that is electrically connected to the external terminal electrode 113 and connected to the connection pad 104, and the wiring pattern 114. And an annular outer peripheral pattern 115 provided as described above. Then, the connection pad 104 and the wiring pattern 114 are flip-chip mounted via the conductor bump 122, and the outer peripheral electrode 105 and the outer peripheral pattern 115 are connected by the bonding member 121, and the upper surface of the mounting substrate 111 is connected from the outer surface of the SAW chip 101. And is sealed with a sealing resin 131 to form an airtight space 123 between the SAW chip and the mounting substrate. Note that an alloy material such as Sn—Sb solder, Sn—Ag—Cu solder, Sn—Pb solder, or Sn—Au solder is used for the bonding member 121 and the conductor bump 122.

  The SAW device hermetic space 123 is formed by connecting the outer peripheral electrode 105 and the outer peripheral pattern 115 with a bonding member 121. Thereby, the penetration of the sealing resin 131 into the airtight space 123 can be prevented. Further, by connecting the bonding member 121 made of an alloy material to the outer peripheral electrode 105 of the SAW chip 101, it can be used as a low resistance wiring electrode.

Next, FIG. 10 shows a structure to which the SAW device disclosed in Japanese Patent Laid-Open No. 5-55303 is applied. The structure of the SAW chip and the mounting substrate is the same as that shown in FIG. The difference from FIG. 9 is that a resinous dam 124 is provided on the outer peripheral electrode 105 of the SAW chip 101 and that the dam 124 is not in contact with the outer peripheral pattern 115 of the mounting substrate 111. The dam 124 uses a resin having higher heat resistance than the sealing resin 131. Thereby, it is possible to prevent the resinous dam 124 from being melted by heat when the sealing resin 131 is heated and cured, and to prevent the sealing resin 131 from entering the hermetic space 123.
JP 2004-64599 A JP-A-5-55303 JP 2004-129092 A JP 2004-363770 A

  By the way, when a SAW chip is flip-chip mounted on a mounting substrate via a conductor bump, a temperature change is applied, and stress is generated in the conductor bump and its joint due to a difference in thermal expansion coefficient between the mounting substrate and the SAW chip. It has been known. When the temperature change is repeated, the stress generated in the conductor bump and its joint is also repeatedly generated, which causes the characteristic fluctuation and characteristic deterioration of the SAW device. In addition, when a sudden temperature change is applied over a long period of time, the conductor bump and its joint may break. In order to improve this, it is necessary to make the distance between the conductor bumps as small as possible. Even if the same temperature change is applied, the smaller the distance between the conductor bumps, the smaller the stress becomes, so that it is possible to prevent breakage of the conductor bump and its joint.

  FIG. 11 is a perspective view of the SAW chip used in FIG. Only the bonding member 121 and the conductor bump 122 are shown on the SAW chip 101, and other illustrations are omitted. In the SAW device of FIG. 9, there is a bonding member in addition to the conductor bump as a conductor connecting the mounting substrate and the SAW chip. Also in this bonding member, the stress caused by the difference in thermal expansion coefficient between the mounting substrate and the SAW chip. Occurs. Here, in the SAW chip 101, the distance between both ends of the lateral conductor bump 122 is X1, the distance between both ends of the longitudinal conductor bump 122 is Y1, and the distance between both ends of the lateral bonding member 121 is X2. When the distance between both ends of the bonding member 121 is Y2, the temperature of the bonding member 121 arranged on the outer side (closer to the end face of the SAW chip) than the conductor bump 122 is changed due to the relationship of X1 <X2 and Y1 <Y2. When stress is applied, the stress generated is large, and there is a risk that the resin may enter the airtight space due to breakage of the joining member and the joining portion. In order to improve this, it is necessary to reduce the dimensions X2 and Y2 of the joining member 121 as much as possible. However, if the dimensions of the joining member 121 are reduced, the airtight space is reduced, and filter function parts such as IDT electrodes and reflectors. It becomes difficult to arrange in the airtight space.

  Further, the SAW device of FIG. 9 has a drawback that the degree of freedom of wiring is extremely low. That is, in the SAW device of FIG. 9, there is no problem even if the outer peripheral electrode and the outer peripheral pattern are connected by a joining member made of solder when both the outer peripheral electrode of the SAW chip and the outer peripheral pattern of the mounting substrate are ground patterns. However, when the outer peripheral electrode of the SAW chip is a ground pattern and the signal line pattern is arranged on the mounting substrate directly below the outer peripheral electrode, the problem is that the ground pattern and the signal line pattern are short-circuited by the joining member. There is. Therefore, it is necessary to arrange the outer peripheral electrode of the SAW chip and the outer peripheral pattern of the mounting substrate so that they can be short-circuited to each other, such as ground patterns or signal line patterns. The drawbacks described above are similarly caused even when an alloy or metal other than solder is used for the conductor bump and the joining member.

  On the other hand, in the SAW device of FIG. 10, since the dam is not in contact with the mounting substrate, stress due to the difference in thermal expansion coefficient between the mounting substrate and the SAW chip does not occur in the dam portion. In addition, the presence or absence of the outer peripheral pattern of the mounting substrate can be arbitrarily determined, and there is an advantage that an arbitrary wiring pattern can be provided on the mounting substrate immediately below the outer peripheral electrode of the SAW chip.

  However, in the SAW device of FIG. 9, it was possible to use a bonding member made of an alloy material to connect the outer peripheral electrode of the SAW chip as a low-resistance wiring electrode. However, the dam of FIG. Therefore, there is a drawback that the outer peripheral electrode of the SAW chip is not low resistance. Also, according to the experiments by the inventors of the present application, the resinous dam is effective in preventing the sealing resin from entering the airtight space because the sealing resin is pressurized during the heating of the resin sealing. This is only the case where there is no accompanying, for example, when the sealing resin is heated and pressurized during resin sealing, such as the method disclosed in Japanese Patent Application Laid-Open No. 2004-129092 and Japanese Patent Application Laid-Open No. 2004-363770. Even if the resin dam is formed using a resin having higher heat resistance than the sealing resin, the resin dam is significantly deformed. The inventor of the present application confirmed by experiment that the sealing resin would enter the airtight space due to the significant deformation of the resin dam.

  In order to solve the problems described above, in the present invention, a SAW chip is flip-chip mounted on a mounting substrate via a conductor bump, and resin-sealed from the outer surface of the SAW chip to the upper surface of the mounting substrate. In a surface-mount SAW device in which an airtight space is formed between chips, the resin is prevented from entering the airtight space in the resin sealing step, and stress caused by a difference in thermal expansion coefficient between the mounting substrate and the SAW chip. An object of the present invention is to realize a SAW device in which the connection strength between the SAW chip and the mounting substrate is increased by reducing the above, and the degree of freedom of wiring is increased.

  In order to solve the above problems, the invention according to claim 1 of the SAW device according to the present invention comprises an insulating substrate, an external terminal electrode for surface mounting disposed at the bottom of the insulating substrate, and an upper portion of the insulating substrate. A mounting substrate having a wiring pattern disposed and electrically connected to the external terminal electrode; a piezoelectric substrate; an IDT electrode formed on one surface of the piezoelectric substrate; and a connection pad connected to the wiring pattern via a conductor bump. A surface acoustic wave (SAW) chip comprising: the SAW chip and the mounting board are flip-chip mounted, and the IDT electrode and the mounting board are coated and formed from the outer surface of the SAW chip to the upper surface of the mounting board. And a sealing resin that forms an airtight space between the sealing resin and the outer periphery of the SAW chip excluding the SAW excitation portion. W provided a dam made of a metal or alloy for preventing flowing into the excitation portion, and characterized in that said mounting substrate with said dam is not in contact.

  The invention described in claim 2 is characterized in that the dam is provided so as not to contact the end face of the SAW chip.

  The invention according to claim 3 is characterized in that the distance of the dam from the end face of the SAW chip is large at the four corners of the SAW chip.

The invention described in claim 4 is characterized in that the dam is made of a metal or an alloy having a melting point higher than 400 ° C.

  The invention according to claim 5 is characterized in that the dam is made of Al or an alloy containing Al as a main component.

  The invention described in claim 6 is characterized in that the cross-sectional shape of the dam is substantially rectangular.

In the invention described in claim 7, the dam is formed by a dry film forming method such as vapor deposition, sputtering, or ion plating, and the pattern formation of the dam is by a lift-off method. It is characterized by.

  The invention according to claim 8 is characterized in that the sealing resin is a resin containing a filler, and an interval between the dam and the mounting substrate is smaller than an average size of the filler.

  The invention described in claim 9 is characterized in that the dam is covered with an insulating film.

  According to the first aspect of the present invention, since the dam made of a metal or an alloy is provided on the outer periphery excluding the SAW excitation portion of the SAW chip and the dam is prevented from contacting the mounting substrate, the sealing resin is used for the SAW excitation. In addition to preventing intrusion into the portion, the stress due to the difference in thermal expansion coefficient between the SAW chip and the mounting substrate can be reduced, and characteristic fluctuations and characteristic deterioration caused by breakage of the joint portion between the SAW chip and the mounting substrate can be prevented. Can be prevented. In addition, since the dam is formed of a metal or an alloy, the dam is not deformed by heating and pressurizing the sealing resin in the resin sealing step, and a highly reliable SAW device can be realized.

  According to the invention described in claim 2, by providing the dam so as not to contact the end face of the SAW chip, metal does not adhere to the dicing blade at the time of dicing, and machinability is not deteriorated. A SAW device with excellent mass productivity can be realized.

  According to the third aspect of the present invention, the mounting angle when the SAW chip is flip-chip mounted on the mounting substrate is controlled by increasing the distance from the end face of the SAW chip at the four corners of the SAW chip. Since it is not necessary, the production efficiency can be increased.

  According to the invention described in claim 4, by forming the dam from a metal or alloy having a melting point higher than 400 ° C., the dam shape is deformed by heat applied when flip-chip mounting the SAW chip on the mounting substrate. Therefore, a highly reliable SAW device can be realized.

  According to the invention described in claim 5, since the dam is formed from Al or an alloy containing Al as a main component, it is inexpensive and easy to form a film, so that a SAW device excellent in mass productivity is realized. it can.

  According to the sixth aspect of the present invention, since the cross-sectional shape of the dam is substantially rectangular, it is possible to enhance the effect of preventing resin intrusion into the airtight space during resin sealing. An excellent SAW device can be realized.

  According to the invention described in claim 7, by forming the dam by a dry film formation method such as vapor deposition, sputtering, ion plating, and the like, and performing pattern formation of the dam using a lift-off method, Impurities can be prevented from adhering to the surface of the metal film or alloy film, and it is no longer necessary to carry out a cleaning process after film formation, which was necessary in the wet film forming method, and a dam can be formed with high accuracy. Manufacturing efficiency can be increased.

  According to the eighth aspect of the present invention, the sealing resin is a resin containing a filler, and the distance between the dam and the mounting substrate is smaller than the average size of the filler, whereby the airtight space in the resin sealing step is reduced. The effect of suppressing the intrusion of the sealing resin can be remarkably improved, and the mechanical strength and moisture resistance of the sealing resin can be improved.

  According to the invention described in claim 9, by covering the dam with an insulating film, it is possible to prevent a short circuit accident due to metal powder that occurs when the gap between the SAW chip and the mounting substrate is reduced. An excellent SAW device can be realized.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 shows a SAW device according to a first embodiment of the present invention. In a SAW chip 1, an IDT electrode 3 and a connection pad 4 for exciting SAW are arranged on a piezoelectric substrate 2, and SAW excitation is performed. A dam 21 made of metal or alloy is provided on the outer peripheral portion excluding the portion. The mounting substrate 11 includes an external terminal electrode 13 for surface mounting and a wiring pattern 14 that is electrically connected to the external terminal electrode 13 and connected to the connection pad 4 at the bottom of the insulating substrate 12. Then, the connection pads 4 of the SAW chip 1 and the wiring pattern 14 of the mounting substrate 11 are flip-chip mounted via the conductor bumps 22 and sealed with a sealing resin 31 from the outer surface of the SAW chip 1 to the upper surface of the mounting substrate 11. An airtight space 23 is formed between the SAW chip 1 and the mounting substrate 11. The dam 21 is not in contact with the mounting substrate 11, and the lower surface of the dam 21 and the mounting substrate 11 are separated by a gap G. The dam 21 prevents the resin from entering the airtight space 23 during the resin sealing process.

  In the SAW device of the present invention, since the dam does not contact the mounting substrate, stress due to the difference in thermal expansion coefficient between the mounting substrate and the SAW chip does not occur in the dam portion. Strictly speaking, the dam in FIG. 1 is connected to the mounting substrate through a sealing resin and a gap, but the sealing resin has a lower elastic modulus than a dam made of a metal or an alloy, so that the dam is lower than the SAW device of FIG. The stress caused by the difference in the coefficient of thermal expansion between the mounting substrate and the SAW chip is reduced. Furthermore, if the gap G between the dam and the mounting substrate is made small, the intrusion of the sealing resin that enters under the dam becomes small, so that the stress generated in the dam can be made extremely small.

Further, in the conventional SAW device of FIG. 9, it is necessary to reduce the dimension of the hermetic space as much as possible in order to reduce the stress caused by the difference in thermal expansion coefficient between the mounting substrate and the SAW chip. However, the SAW device of the present invention has a stress caused by the difference in thermal expansion coefficient between the mounting substrate and the SAW chip without reducing the airtight space. Since it can be made small, filter function parts, such as IDT and a reflector, can be easily arrange | positioned in airtight space. In addition, since the dam does not contact the mounting substrate, for example, even when the dam is connected to the ground connection pad and used as a ground electrode, it is not always necessary to arrange the ground wiring pattern on the implementation substrate directly below the dam. And a signal wiring pattern can be provided. Thus, the SAW device of the present invention is advantageous in that the degree of freedom in filter design and wiring is higher than that of the SAW device in FIG.

Furthermore, the dam of the SAW device of the present invention is formed of a metal or an alloy, and the SAW chip is thicker than the connection pad formed on the SAW chip, the wiring electrode connecting the connection pad and the IDT electrode, etc. It can be used as a low resistance wiring electrode. For example, when the dam is connected to the ground connection pad, the dam can be used as a low-resistance ground electrode, which is effective in reducing the loss of the SAW device. In addition, when the dam is formed of a resin as in the conventional SAW device of FIG. 10, if the sealing resin is heated and pressurized during the resin sealing process, the resin dam significantly deforms and the function of the dam is increased. Although the SAW device of the present invention has a dam formed from a metal or an alloy, the dam is not deformed by heating and pressurizing the sealing resin during the resin sealing process. . Therefore, as compared with the SAW device of FIG. 10, the SAW device of the present invention can reliably prevent the resin from entering the airtight space during the resin sealing process.

  The dam may be provided on the mounting substrate side, but in order to form a dam made of a metal or an alloy with high dimensional accuracy on the wiring substrate base material in which a plurality of mounting substrates are connected together, It is necessary to form a resist pattern by a photolithography technique corresponding to the dam pattern on the wiring board base material. Compared to resist patterns with high dimensional accuracy, the wiring pattern on the wiring board base material has poor dimensional accuracy, and it is difficult to accurately match the wiring pattern and dam pattern over the entire wiring board base material. Not suitable for wiring. Therefore, the dam is preferably formed on the SAW chip side.

  The gap G between the dam and the mounting substrate is preferably narrow in order to reduce the amount of sealing resin entering the airtight space. As a method of narrowing the gap G, in addition to increasing the thickness of the dam, the gap G may be narrowed by providing an outer peripheral pattern 15 on the mounting substrate 11 directly below the dam 21 as shown in FIG. As the material of the outer peripheral pattern 15, an insulator such as alumina coat or glass coat can be applied, but the same material as the wiring pattern 14, for example, a metallized pattern made of W or Mo is subjected to Ni plating and Au plating, and the outer peripheral pattern If 15 is formed, an outer peripheral pattern can be formed without increasing the manufacturing process of the mounting substrate.

  Moreover, it is preferable that the dam is provided so as not to contact the peripheral edge of the SAW chip. The reason will be described below. 3 and 4 are views showing the state of the piezoelectric substrate before and after dicing. FIG. 3A is a plan view of the piezoelectric substrate before dicing, FIG. 3B is a cross-sectional view of the piezoelectric substrate before dicing, and FIG. ) Shows a cross-sectional view of the piezoelectric substrate after dicing. Illustration of conductor bumps, IDT electrodes, connection pads and the like formed on the piezoelectric substrate is omitted. When a dam 21 made of a metal or alloy is formed on the piezoelectric substrate 2 so as to cover the dicing margin as shown in FIGS. 3A and 3B and dicing is performed, a SAW chip as shown in FIG. A dam is formed in contact with the end face of 1. However, if the cutting allowance of the piezoelectric substrate is covered with a metal film, the metal adheres to the dicing blade during dicing and the machinability deteriorates, the piezoelectric substrate breaks during dicing, or the dicing blade is not cracked. May occur. On the other hand, as shown in FIGS. 4 (a) and 4 (b), if a dam 21 made of metal or alloy is formed on the piezoelectric substrate 2 so as not to be in contact with the cutting allowance, dicing is performed at the time of dicing. There is no adhesion of metal to the metal, and machinability is not deteriorated. For this reason, the dam is preferably provided inside the piezoelectric substrate so as not to contact the end face of the SAW chip.

  As described above, in the SAW device according to the first embodiment of the present invention, the SAW chip is flip-chip mounted on the mounting substrate via the conductor bump, and the resin sealing is performed from the outer surface of the SAW chip to the upper surface of the mounting substrate. In a surface mount type SAW device in which an airtight space is formed between the SAW chip and the mounting substrate, a dam made of metal or alloy is provided on the outer periphery excluding the SAW excitation portion of the SAW chip, and the dam contacts the mounting substrate. As a result, the stress caused by the difference in thermal expansion coefficient between the mounting substrate and the SAW chip generated in the dam portion becomes extremely small. As a result, the joint portion between the mounting substrate and the SAW chip can be prevented from breaking, and the airtight space can be increased, so that the degree of freedom of wiring can be increased. Further, since the dam is made of a metal or an alloy, its shape is not changed by heating and pressurization of the sealing resin at the time of resin sealing, so that the dam is excellent in reliability. Further, by providing the dam on the inner side of the piezoelectric substrate so as not to contact the end face of the SAW chip, it is possible to prevent a defective product from being generated in the dicing process.

  Next, a SAW device according to a second embodiment of the present invention will be described. FIG. 5 shows a plan view of a SAW chip 41 of a SAW device according to the second embodiment of the present invention. On the piezoelectric substrate 42, two two-stage cascaded primary-third-order dual mode SAW filters used in the RF circuit are formed. The input side is an unbalanced circuit and the output side is a balanced circuit. Yes. The first SAW filter 51 has three IDT electrodes arranged close to each other along the propagation direction of the surface wave, and a first electrode group 52 and a second electrode group 53 in which reflectors are formed on both sides of the IDT electrode. Are connected in cascade to form a filter. Similarly to the first SAW filter 51, the second SAW filter 61 has three IDT electrodes arranged close to each other along the propagation direction of the surface wave, and a third SAW filter 61 in which reflectors are formed on both sides of the IDT electrode. A filter is formed by cascading the electrode group 62 and the fourth electrode group 63. The conductor pads 54 of the first SAW filter 51 and the conductor pads 64 of the second SAW filter 61 are used as unbalanced input terminals, and the conductor pads 55 and 56 of the first SAW filter 51 and the second SAW filter 61 The conductor pads 65, 66 are used as balanced output terminals, and the conductor pads 57, 58, 59, 67 are grounded. Then, an octagonal dam 43 is formed so as to surround the first to fourth electrode groups on the piezoelectric substrate, the wiring pattern, and the metal pad. Although not shown, after the dam is formed, the SAW chip and the mounting substrate are flip-chip mounted via conductor bumps in the same manner as in the first embodiment, and resin sealing is performed from the outer surface of the SAW chip to the upper surface of the mounting substrate. In addition, an airtight space is formed between the SAW chip and the mounting substrate. The thickness of the dam is adjusted so as not to contact the mounting substrate.

The feature of this embodiment is that the dam shape is octagonal so that dams are not arranged at the four corners of the piezoelectric substrate. That is, considering the case where the dam is formed up to the four corners of the piezoelectric substrate as shown in FIG. 6, the dam is mounted when the SAW chip is tilted in the directions of arrows φ and θ as shown in FIG. It hits the substrate, causing problems such as deterioration of the mounting strength of the SAW chip and breakage of the SAW chip. In particular, the smaller the gap G between the dam provided on the SAW chip and the mounting substrate, the more likely the dam will hit the mounting substrate. For this reason, if the dams are not arranged at the four corners of the SAW chip, even if the SAW chip is slightly inclined in the directions of the arrows φ and θ as shown in FIG. You wo n’t win.

  As described above, according to the SAW device according to the second embodiment of the present invention, the dams provided on the SAW chip are not arranged at the four corners of the piezoelectric substrate. There is no need to control, and manufacturing efficiency can be increased. In FIG. 5, the dam shape is an octagon, but may be a polygon, a circle, an ellipse or the like that is an octagon or more as long as the dam is not disposed at the four corners of the SAW chip. When the dam shape is a polygon, at least one of the vertices may be rounded with an arc.

  In the first and second embodiments described above, Sn-Ag-Cu solder or Au is generally used for the conductor bumps that connect the SAW chip and the mounting substrate. When the conductor bump is Sn-Ag-Cu solder, the peak temperature when the SAW chip is flip-chip mounted on the mounting substrate is 260 ° C. or less, and when the conductor bump is Au, the SAW chip is thermocompression bonded. When flip-chip mounting is performed by a method (thermocompression method not using ultrasonic waves), heating is usually performed at 300 ° C. to 350 ° C. and a maximum of 400 ° C. Accordingly, the metal material or alloy material used for the dam needs to have a melting point higher than at least 400 ° C. so that the dam is not deformed by heating during flip chip mounting. For example, when the material of the dam is Sn—Ag—Cu solder having a melting point of 217 ° C., the dam is melted together when the conductor bump is melted when the SAW chip is flip-chip mounted on the mounting substrate. The dam once melted is solidified by cooling, but its cross-sectional shape is rounded like the dam 71 in FIG. The cross-sectional shape of the dam is substantially rectangular as shown in FIGS. 1 and 2, and the effect of preventing the infiltration of the sealing resin into the airtight space during resin sealing is higher. As shown in FIG. If the cross-sectional shape is rounded, the sealing resin easily enters the airtight space during resin sealing, and reliability is impaired.

  Examples of the metal having a melting point higher than 400 ° C. include Al, Au, Ag, Cu, Ni, Ti, Cr, Ta, Mo, and W, and are applicable to dams. Among these, Al, which is an inexpensive metal that can be easily formed and processed, is most preferable as a material for the dam.

  Preferably, the dam is formed by a dry film formation method such as vapor deposition, sputtering, or ion plating, and the dam pattern is formed by a lift-off method. When a metal film or alloy film serving as a dam is formed using a wet film forming method such as electroplating or electroless plating, impurities are attached to the surface of the metal film or alloy film. If a SAW device is configured with impurities on the surface of the metal film or alloy film, dams, connection pads, IDT electrodes and the like are corroded, and the performance of the SAW device is significantly deteriorated. In order to prevent this, it is necessary to insert a cleaning step after film formation by the wet film formation method, but there is a problem that the number of manufacturing steps increases. In addition, the wet film forming method has a large variation in film thickness, and when the gap G between the SAW chip and the mounting substrate is reduced, a location where the dam and the mounting substrate are brought into contact with each other and the gap G is locally increased. The part which becomes will also occur at the same time. Furthermore, it is difficult to deposit Al, which is preferable as a dam material, by the wet film formation method.

  For the above reasons, if a metal film or alloy film that becomes a dam is formed using a dry film forming method such as vapor deposition, sputtering, or ion plating, the surface of the metal film or alloy film is hardly contaminated. Therefore, it is not necessary to carry out a cleaning step after film formation, which is necessary in the wet film formation method. Further, since the dry film formation method has a smaller variation in film thickness than the wet film formation method, the variation in the gap G in FIGS. 1 and 2 can be reduced. In addition, if a dry film forming method is used, it is possible to easily form an Al film, which was difficult with the wet film forming method.

  Further, when a printing method is used as a dam pattern forming method, it is difficult to form a fine dam pattern. According to the photolithography technique, a resist pattern corresponding to a fine dam pattern can be formed. Since the dam needs to be formed after the formation of the connection pad and the IDT electrode, the metal film or alloy film to be the dam is formed by using a lift-off method that can be selectively formed only at the location where the dam is formed. It is good to form.

  The reason for forming the dam after the formation of the connection pad and the IDT electrode is that the film thickness of the dam is thicker than that of the connection pad and the IDT electrode. If the connection pad and IDT electrode are formed after the dam is formed, the resist cannot be applied with a uniform film thickness in the photolithography process of the connection pad and IDT electrode, and the finished dimensions of the connection pad and IDT electrode vary. It will occur. Therefore, it is necessary to form the dam after the connection pad and the IDT electrode are formed.

The metal film or alloy film forming the dam may be a single layer or a laminated film. For example, when a dam composed of an Al vacuum deposition film is formed on a LiTaO ₃ substrate by a lift-off method, the LiTaO ₃ and Al dam are in close contact with each other when the resist pattern is not changed during the vacuum deposition of Al. Therefore, at least one metal film or alloy film (hereinafter referred to as an adhesion film) that improves adhesion may be provided between the Al dam and LiTaO ₃ . If this adhesion film has the same film structure as the connection pad or IDT electrode, the adhesion film can be formed without increasing the number of manufacturing steps, and the adhesion film can be formed simultaneously with the connection pad or IDT electrode. .

  By the way, for the purpose of controlling the thermal expansion coefficient of the sealing resin and improving the mechanical strength and moisture resistance, the sealing resin may contain fillers such as spherical silica. It has been found that by suppressing the gap G in FIG. 1 and FIG. 2 to be smaller than the average size of the filler, the effect of suppressing the intrusion of the sealing resin into the airtight space in the resin sealing process can be remarkably improved. In FIG. 2, the thickness of the connection pad is 1 μm, the thickness of the conductor bump is 22 μm, the thickness of the dam made of Al is 18 μm, the gap G is 5 μm, and an epoxy resin containing spherical silica having an average particle diameter of 15 μm as a sealing resin. When a SAW device was manufactured by a resin sealing method involving heating and pressurization of a resin sheet, which is disclosed in Patent Document 3 and Patent Document 4, using the resin sheet, the intrusion of the sealing resin into the airtight space is It did not occur at all. On the other hand, when a similar SAW device was manufactured with the thickness of the dam made of Al being 5 μm and the gap G being 18 μm, the infiltration of the sealing resin into the airtight space occurred. When various samples were manufactured using the dam thickness and the gap G as experimental parameters, when the gap G was larger than the average particle diameter of the spherical silica contained in the sealing resin, the sealing resin entered the hermetic space. Occurrence occurred frequently, and as the gap G was further increased, the amount of sealing resin invaded. From the above, it was confirmed that the gap G needs to be smaller than the average size of the filler contained in the sealing resin.

  In the SAW device of the present invention described above, if the dam made of metal or alloy is covered with an insulating film, the metal powder of the dam and the wiring pattern or the dam and the outer peripheral pattern generated when the gap G in FIGS. It is possible to prevent a short circuit accident due to. The insulating film provided on the dam surface is, for example, silicon oxide, silicon nitride, or alumina. Examples of the method for forming the insulating film provided on the surface of the dam include a sputtering method, a CVD method, and an anodic oxidation method.

1 shows a cross-sectional view of a SAW device according to a first embodiment of the present invention. Sectional drawing of the modification of the SAW device which concerns on 1st Example of this invention is shown. It is explanatory drawing at the time of forming a dam so that it may touch the end surface of a SAW chip, A top view of a piezoelectric substrate before dicing is shown in (a), A sectional view is shown in (b), A sectional view of a piezoelectric substrate after dicing Is shown in (c). It is explanatory drawing at the time of forming a dam so that it may not contact the end surface of a SAW chip, The top view of the piezoelectric substrate before dicing is shown to (a), sectional drawing is shown to (b), The cross section of the piezoelectric substrate after dicing The figure is shown in (c). The top view of the SAW chip of the SAW device concerning the 2nd example of the present invention is shown. The top view of a SAW chip at the time of forming a dam to the four corners of a SAW chip is shown. It is a figure explaining the mounting angle at the time of flip-chip mounting the SAW chip after dam formation on a mounting substrate. Sectional drawing of the SAW device after flip-chip mounting when a solder with a low melting point is used for the dam material is shown. A sectional view of a SAW device indicated in patent documents 1 is shown. A cross-sectional view of a SAW device described in Patent Document 2 is shown. The perspective view of the SAW chip of the SAW device described in patent document 1 is shown.

Explanation of symbols

1, 41: SAW chip 2, 42: Piezoelectric substrate 3: IDT electrode 4: Connection pad 11: Mounting substrate 12: Insulating substrate 13: External terminal electrode 14: Wiring pattern 15: Peripheral patterns 21, 43, 71: Dam 22: Conductor bump 23: Airtight space 31: Sealing resin 51: First SAW filter 52: First electrode group 53: Second electrode group 54, 64: Unbalanced input terminals 55, 56, 65, 66: Balanced output Terminals 57, 58, 59, 67: Ground terminal 61: Second SAW filter 62: Third electrode group 63: Fourth electrode group

Claims (9)

A mounting substrate comprising: an insulating substrate; an external terminal electrode for surface mounting disposed at the bottom of the insulating substrate; and a wiring pattern disposed on the insulating substrate and electrically connected to the external terminal electrode;
A surface acoustic wave (SAW) chip comprising a piezoelectric substrate, an IDT electrode formed on one surface of the piezoelectric substrate, and a connection pad connected to the wiring pattern via a conductor bump;
A sealing resin that forms an airtight space between the IDT electrode and the mounting substrate by being coated from the outer surface of the SAW chip to the upper surface of the mounting substrate in a state where the SAW chip and the mounting substrate are flip-chip mounted; In a SAW device with
A dam made of a metal or an alloy for preventing the sealing resin from flowing into the SAW excitation portion is provided on the outer peripheral portion excluding the SAW excitation portion of the SAW chip, and the dam and the mounting substrate are in contact with each other. SAW device characterized by not.   The SAW device according to claim 1, wherein the dam is provided so as not to contact an end face of the SAW chip.   3. The SAW device according to claim 1, wherein a distance of the dam from the end face of the SAW chip is increased at four corners of the SAW chip. 4. The SAW device according to any one of claims 1 to 3, wherein the dam is made of a metal or an alloy having a melting point higher than 400 ° C.   The SAW device according to claim 1, wherein the dam is made of Al or an alloy containing Al as a main component.   The SAW device according to any one of claims 1 to 5, wherein a cross-sectional shape of the dam is substantially rectangular. The dam is formed by a dry film formation method such as vapor deposition, sputtering, or ion plating, and the pattern formation of the dam is by a lift-off method. The SAW device according to 1.   The SAW device according to claim 1, wherein the sealing resin is a resin containing a filler, and an interval between the dam and the mounting substrate is smaller than an average size of the filler. The SAW device according to claim 1, wherein the dam is covered with an insulating film.

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