JP2010245266A - Electronic component and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component which has superior airtight sealing properties and shock resistance, and a method of manufacturing the same. <P>SOLUTION: The electronic component is constituted by metallizing first joining portions 50 and second joining portions 60 as mutual joining surfaces of a vibration base 20, a first substrate 30 and a second substrate 40 as two or more members to be joined, and joining the joining surfaces sandwiching solder materials, wherein the solder materials are In, and the joining portions are formed of eutectic alloy by the metallization and diffusion with In. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic component such as a piezoelectric vibrator used in an electronic device or the like, and more particularly to an electronic component formed by hermetically bonding and sealing a plurality of base materials using a metal alloy and a manufacturing method thereof.

  Conventionally, there is a eutectic alloy of Sn (tin) and Pb (lead) as a solder material used for mounting electronic components. This eutectic solder has a composition of 62Sn-38Pb (wt%), and has a melting temperature of eutectic point of 183 degrees and is used for mounting electronic components for reflow. However, when an electronic device using such a eutectic alloy is discarded, there has been a problem of soil contamination and water pollution in which harmful lead is eluted by acid rain into groundwater or rivers and contaminates.

  Therefore, in recent years, Au—Sn eutectic alloys have attracted attention as lead-free solder from the viewpoint of environmental protection. 80Au-20Sn eutectic alloy (wt%) has an eutectic composition with a melting point of 280 degrees, does not contain harmful substances such as lead, can be heat-treated at a relatively low temperature, and has excellent corrosion resistance. Widely used in the field of electronic equipment.

  As shown in FIG. 10, the crystal resonator 100 disclosed in Patent Document 1 includes a plate-shaped resonator substrate 120, a base substrate 130, and a lid substrate 140, and the resonator substrate 120, the base substrate 130, and the lid substrate 140. Are laminated by eutectic bonding of a eutectic alloy layer (Au—Sn eutectic alloy) 150 made of gold and tin and hermetically sealed.

  However, as shown in the equilibrium diagram of Au and Sn in FIG. 11 (Metal Data Book edited by the Japan Institute of Metals, published by Maruzen Co., Ltd. Publishing Division), the composition ratio of the eutectic point A of the Au—Sn eutectic alloy. Since (wt%) is Au: Sn = 80: 20 as described above, there is a problem that the content of gold, which is more expensive than tin, is high, and the cost of the material is high.

  Further, in general, an electronic component such as a crystal resonator is surface-mounted on a printed wiring board together with other circuit components and incorporated into an equipment device, or is subjected to a heat treatment again for repair and disassembly of the equipment device. For example, the electronic component is surface-mounted and soldered to a printed wiring board for an apparatus device together with other circuit components, and then commercialized through a heat treatment process by reflow. In this case, at the reflow temperature, it is necessary that the electronic component does not fall off and each joining portion of the electronic component does not melt.

  Therefore, as proposed in Cited Document 1, when an Au—Sn eutectic alloy is used as the brazing material, the eutectic alloy composed of the Au—Sn eutectic alloy is used when the temperature is higher than the temperature of about 280 degrees which is the eutectic point. Since the crystal alloy layer 150 is melted, the hermetic reliability of the internal space of the hermetically sealed crystal unit 100 may be deteriorated.

  When mounting a quartz resonator on a printed wiring board by the reflow method, there has been a technical limitation that the reflow furnace cannot be set to a temperature higher than the eutectic point temperature of the Au—Sn eutectic alloy. .

  Alternatively, in Patent Documents 3 to 5, after temporarily melting and liquefying a metal brazing material or an insert metal disposed between two terminal electrodes to be joined, the metal brazing material is put into the metal of the terminal electrode. A method of bonding by diffusion and isothermal solidification, a so-called liquid phase diffusion bonding method (hereinafter referred to as TLP (Transient Liquid Phase) bonding) has been proposed. That is, when joining each electrode (Au layer) provided on two substrates, an Sn layer which is a low melting point metal is provided as a metal brazing material on at least one of the electrodes to form a laminated film, When the Sn is melted and diffused into the metal layer (Au layer) to form an Au—Sn eutectic alloy to join the two electrodes, the melting point of Sn is about 232 ° C. It is necessary to heat at a temperature of at least 232 degrees. Therefore, considering the thermal strain and internal stress due to the difference in the thermal expansion coefficient of the substrate and the electrode part, the heating temperature for the substrate is preferably as low as possible. Since the stress generated at the bonding interface can be reduced as much as possible, it may be advantageous to stabilize the bonding site.

  When an Au—Sn eutectic alloy is formed and bonded, as shown in FIG. 12, a Cr layer (chromium layer) is used as an underlayer in order to improve the adhesion between the vibrator substrate 1 and the substrate 2 and the Au layer. ) 3 and then an Au layer (gold layer) 4 is formed. Here, since the composition ratio of the Au—Sn eutectic alloy is 80:20 as described above, the thickness of the Sn layer 5 formed on the Au layer 4 of the substrate 2 is thinner than that of the Au layer 4. turn into. Therefore, the Sn layer 5 naturally diffuses into the lower Au layer 4 just by allowing it to stand at room temperature before bonding, and the eutectic reaction proceeds. That is, since the Sn layer 5 is originally thin, all of Sn diffuses into the lower Au, causing a problem that Sn disappears. Therefore, in the laminated structure of Au and Sn, after the Sn layer 5 is formed on the Au layer 4, the bonding must be started immediately. Therefore, it is desirable that the composition of the eutectic metal has a higher content of the metal to be melted and diffused.

  Further, in Patent Document 1, bonding between the vibrator substrate 120 and the base substrate 130 (hereinafter referred to as first bonding) and bonding between the vibrator substrate 120 and the lid substrate 140 (hereinafter referred to as second bonding). When the same metal brazing material such as Au—Sn eutectic alloy is used for the first and second bonding, the first and second bonding must be performed simultaneously.

  That is, when the first bonding is performed under the same bonding conditions (the melting point of the metal brazing material is the same) and then the second bonding is performed, the second bonding is performed as described above. At this time, there is a possibility that the joint portion where the first joining is performed is melted and the hermeticity of the vibrator package is lowered.

  For this reason, since it is necessary to perform the first and second bondings simultaneously, the vibrator substrate is formed by applying a metal brazing material to both surfaces of the frame portion 121 of the vibrator substrate 120 of the intermediate layer by screen printing or the like using a mask. The base substrate 130 and the lid substrate 140 are bonded to both surfaces of the frame portion 121 of 120, respectively. Alternatively, a metal brazing material may be applied to the outer peripheral edge of the base substrate 130 and the lid substrate 140 facing the frame portion 121 of the vibrator substrate 120 of the intermediate layer by screen printing using a mask in a frame shape or the like. There is a problem in that the lid substrate 140 has to be bonded to both surfaces of the vibrator substrate 120, there is a difficulty in securing the bonding position accuracy and fixing each member.

  On the other hand, the piezoelectric vibration device disclosed in Patent Document 2 as shown in FIG. 13 has a piezoelectric diaphragm 160 with a frame, a first case 162 joined to the top and bottom of the piezoelectric diaphragm 160 with a frame, In the bonding of the second case 163 and the framed piezoelectric diaphragm 160, a bonding material used for bonding the first case 162 and the framed piezoelectric diaphragm 160 (see FIG. It has been proposed to use a bonding material having a melting point lower than that of the metal brazing material. According to this, when the second case 163 and the framed piezoelectric diaphragm 160 are joined, the framed piezoelectric diaphragm 160 and the first case 162 that have already been joined, Since it cannot be heated to a temperature equal to the melting point of the bonding material used for bonding, the bonded portion between the first case 162 and the piezoelectric diaphragm 160 with the frame is melted to reduce the airtightness. It is possible to join without adverse effects such as.

JP 2001-267875 A JP 2007-243681 A Japanese Patent No. 4136844 Republished WO2005 / 086211 JP 2007-19360 A

  However, a metal brazing material used for joining 164 (first joining) between the first case 162 and the frame-attached piezoelectric diaphragm 160 and joining between the second case 163 and the frame-attached piezoelectric diaphragm 160. Since the metal brazing material used for 165 (second joining) is different, the thermal expansion coefficient and the rigidity of the metal brazing material are different, and the first case 162 and the second case 163 joined up and down. It is expected that the thermal strain and internal stress generated at the bonding interface between the frame and the framed piezoelectric diaphragm 160 are unevenly distributed. For this reason, there is a possibility that the vibration characteristics of the piezoelectric vibration device are deteriorated and cracks are generated at the bonding interface between the vibrator substrate and the case. Furthermore, since the types of the metal brazing material are different between the first bonding 164 and the second bonding 165, the bonding conditions are different, and the bonding process is complicated due to a change in setting, etc., so that the productivity is deteriorated. There was a problem that.

  Therefore, the present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an electronic component excellent in hermetic sealing and impact resistance and a method for manufacturing the same.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Application Example 1] The electronic component of the present invention is an electronic component in which two or more members to be joined are subjected to metal metallization on each joint surface, and the joint surface is joined with a brazing material interposed therebetween, The brazing material is In and the joint is a eutectic alloy formed by diffusion of the metal metallization and the In.

  The eutectic point of the Au—In eutectic alloy is about 500 degrees, and the electronic component can be mounted on a printed wiring board or the like by using reflow without adversely affecting the eutectic alloy. In addition, the melting point of In is 156 degrees, and it can be melted at a temperature lower than the melting point of conventional Sn (232 degrees) and diffused into Au to form a eutectic alloy, so that bonding can be performed. It is possible to reduce thermal strain and internal stress due to the difference in thermal expansion coefficient.

[Application Example 2] The electronic device according to Application Example 1, wherein the electronic device includes two members to be joined, one of which is a container that houses an electronic element, and the other is a lid that seals the opening of the container. parts.
According to this, the eutectic point of the Au—In eutectic alloy is about 500 degrees, and there is no fear of deterioration of hermeticity, and a highly accurate electronic component having a two-layer structure can be obtained.

  Application Example 3 The first application member includes three members to be bonded, the first member to be bonded is an electronic element layer, and the second and third members to be bonded hold the upper and lower surfaces of the electronic element layer. The electronic component according to Application Example 1, wherein the electronic component is a case and a second case.

  According to this, since the eutectic bond formed in the first bonding is higher than the bonding temperature, the first bonding is dissolved by heating when a subsequent process such as heat treatment such as second bonding or reflow is performed. Therefore, there is no risk of deterioration of airtightness, and a highly accurate electronic component having a three-layer structure can be obtained.

Application Example 4 The electronic component according to any one of Application Examples 1 to 3, wherein at least a surface layer of the metal metallization is Au.
According to this, the eutectic point of the Au—In eutectic alloy is about 500 degrees, and the electronic component can be mounted on a printed wiring board or the like by using reflow without adversely affecting the eutectic alloy.

Application Example 5 The electronic component according to Application Example 4, wherein the eutectic alloy has an In content ratio of 36.8 to 53.8 wt%.
According to this, since a dense structure in which the crystal grains of the Au—In eutectic alloy are extremely small can be realized, it is possible to significantly improve the bonding reliability.

Application Example 6 The electron according to Application Example 4 or 5, wherein the composition ratio of Au and In constituting the eutectic alloy is Au: In = 46.2: 53.8 (wt%). parts.
According to this, since the crystal grains of the Au—In eutectic alloy are extremely small and a dense structure can be realized, the bonding reliability can be highly stabilized.

Application Example 7] The electronic component according to any one example of Application Example 4 to 6 wherein the eutectic alloy is characterized in that it is a Au-In _2.
According to this, the eutectic alloy can be most crystallized and stabilized.

  Application Example 8 An electronic component manufacturing method according to the present invention is the electronic component manufacturing method according to any one of Application Examples 1 to 7, wherein the metal metallization of any one of the facing members to be bonded is performed. A step of forming a layer made of a brazing material on the surface layer, a step of making a laminated body in which the bonding surfaces of the members to be joined are opposed to each other, and heating and pressurizing the laminated body at a temperature at which the brazing material melts, A step of bonding the bonding surfaces to each other by diffusing the brazing material into the metallized layer.

  According to this, in the process of forming a 2nd junction part, it can carry out on the same material and the same conditions as a 1st junction part. Further, the oscillation frequency of the vibrating body can be adjusted before the second substrate is bonded. Further, since the eutectic bond formed in the first bonding is higher than the bonding temperature, when the subsequent process such as the second bonding or heat treatment such as reflow is performed, the first bonding is not dissolved by heating and is airtight. This makes it possible to manufacture highly accurate electronic components.

It is the disassembled perspective view which looked at the piezoelectric vibrator which is one Example of the electronic component which concerns on this invention from diagonally upward of the 1st board | substrate. It is the disassembled perspective view seen from the slanting lower part of the 2nd board | substrate of a piezoelectric vibrator. It is sectional drawing of the modification of a piezoelectric vibrator. It is explanatory drawing of the manufacturing method of the piezoelectric vibrator which concerns on this invention, Comprising: (a) is sectional drawing of the arrangement state before joining of a 1st junction part, (b) is explanatory drawing of frequency adjustment, (c) is lamination | stacking. It is sectional drawing of a body. It is the elements on larger scale which showed the process which forms Au-In eutectic alloy. It is an equilibrium state diagram of Au and In. It is a figure of the Au-In eutectic alloy formed by TLP joining. It is an equilibrium state diagram of Au and In. It is explanatory drawing of the modification of the electronic component which concerns on this invention, Comprising: (a) is sectional drawing which shows a 1st modification, (b) is sectional drawing which shows a 2nd modification. It is a structure schematic diagram of the conventional crystal oscillator. It is an equilibrium state diagram of Au and Sn. It is the elements on larger scale of the Au-Sn junction cross section. It is the structure schematic of the conventional piezoelectric vibration device.

Embodiments of an electronic component and a method for manufacturing the same according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view of a piezoelectric vibrator, which is an embodiment of an electronic component according to the present invention, viewed obliquely from above a first substrate. FIG. 2 is an exploded perspective view of the piezoelectric vibrator as viewed from obliquely below the second substrate.

The piezoelectric vibrator 10 according to the present invention includes a vibrating body substrate 20, a first substrate 30, a second substrate 40, a first joint portion 50, and a second joint portion 60 as main components.
A vibrating body substrate 20 (electronic element layer) serving as a member to be joined includes a vibrating body 21 and a frame body 22 that surrounds the vibrating body 21 with a predetermined distance from the outer periphery of the vibrating body 21. The vibrating body 21 and the frame body 22 are integrally formed via connecting portions 23A and 23B. Note that the vibrating body 21 of the present embodiment is formed thinner than the frame body 22, and the connecting portions 23A and 23B are formed in a tapered shape. A projecting portion 24 is formed on the frame located diagonally to the connecting portion 23A. A pair of connection electrodes 25 </ b> A and 25 </ b> B are formed on the back surface (second substrate 40 side) of the connecting portion 23 </ b> A and the protruding portion 24. A pair of excitation electrodes 26 </ b> A and 26 </ b> B are formed on the front and back surfaces of the vibrating body 21 so as to face each other. Excitation electrodes 26A and 26B are electrically connected to connection electrodes 25A and 25B formed diagonally on the back surface of the vibration substrate through routing electrodes 27A and 27B, respectively.

  The vibrator substrate 20 according to the embodiment will be described by using a flat AT-cut quartz substrate as an example, but the vibrator substrate 20 may be made of lithium tantalate, lithium niobate, lead zirconate titanate, etc. in addition to quartz. It is possible to apply a piezoelectric material, a semiconductor material such as a silicon semiconductor, or other insulator materials.

  For the first and second substrates 30 and 40 (first and second cases) to be bonded members, quartz, glass, or a ceramic substrate can be used as the material. The first and second substrates 30 and 40 are preferably made of the same material as that of the vibrator substrate 20 in order to avoid thermal distortion and internal stress due to a difference in thermal expansion coefficient. The first substrate 30 is a flat substrate that covers the upper surface of the vibrating body substrate 20. The second substrate 40 is a flat substrate that supports the lower surface of the vibrator substrate 20. In the second substrate 40, through holes 42 </ b> A and 42 </ b> B are formed at positions facing the connection electrodes 25 </ b> A and 25 </ b> B formed on the lower surface of the vibration substrate 20. The through holes 42A and 42B have a metal coating formed therein. External electrodes 44 </ b> A and 44 </ b> B are formed on the lower surface of the second substrate 40. The external electrodes 44A and 44B are electrically connected to the connection electrodes 25A and 25B through the through holes 42A and 42B.

  The first and second bonding portions 50 and 60 are Au layers constituting metal metallization as a bonding metal film in order to form an Au—In eutectic alloy using TLP bonding, and at least one of the bonding portions Has a laminated structure in which an In layer as a brazing material is laminated on the surface of the Au layer. An Au-In eutectic alloy is formed by heating In at approximately 156 degrees or more, which is the melting point of In, causing In to melt and diffusing the In into Au to cause a eutectic reaction. Can do. The eutectic point of the Au—In eutectic alloy formed at this time is about 500 degrees.

  Here, in an Au—Sn eutectic alloy that has been applied as a conventional eutectic alloy, the eutectic reaction between Au and Sn is performed by heating at about 232 ° C. or higher, which is the melting point of Sn, and melting and diffusing into the Au layer. As a result, an Au—Sn eutectic alloy having a eutectic point of 280 degrees was formed. As described above, when a piezoelectric vibrator such as a crystal vibrator is mounted on a printed wiring board by the reflow method, if the reflow furnace is set to a temperature higher than the eutectic point temperature of the Au—Sn eutectic alloy, Au—Sn. The eutectic alloy will melt. For this reason, there existed the problem of the technical restrictions that a reflow furnace (200 degree | times-300 degree | times) cannot be set to the temperature higher than the temperature of the eutectic point of Au-Sn eutectic alloy. However, in the piezoelectric vibrator of this embodiment, the melting point of the Au—In eutectic alloy formed in the first and second joints 50 and 60 is about 500 degrees, which is higher than the temperature of the reflow furnace. Therefore, the piezoelectric vibrator can be mounted on the printed wiring board by using reflow without adversely affecting the Au—In eutectic alloy. In addition, since In has a melting point of 156 degrees, it can be melted at a temperature lower than the melting point of Sn (232 degrees) and diffused into Au to form a eutectic alloy, so that bonding can be performed. It is possible to reduce thermal strain and internal stress due to the difference in thermal expansion coefficient.

  The first bonding portion 50 is a eutectic alloy (Au—In) film formed between the vibrating body substrate 20 and the first substrate 30. The second bonding portion 60 is a film of a eutectic alloy (Au—In) that is the same quality as the first bonding portion 50 formed between the vibrating body substrate 20 and the second substrate 40.

  FIG. 3 is a cross-sectional view of a modification of the piezoelectric vibrator. As illustrated, in the piezoelectric vibrator 10a, the vibrating body 21 and the frame body 22 of the vibration plate substrate 20 are formed to have the same plate thickness, and the first and second substrates 30 and 40 have a concave surface facing the vibrating body 21. It is good also as a structure which forms and forms cavity space.

  Next, a method for manufacturing a piezoelectric vibrator having the above configuration will be described. 4A and 4B are views for explaining a method of manufacturing a piezoelectric vibrator according to the present invention, in which FIG. 4A is a cross-sectional view of the arrangement state of the first joint before joining, FIG. 4B is an explanatory view of frequency adjustment, c) shows a cross-sectional view of the laminate. As shown in the drawing, the manufacturing method of the present embodiment will be described with a manufacturing example in units of wafers. A plurality of vibrator substrates 20 are arranged and arranged on a vibrator substrate wafer (mother wafer) 200. The shape and electrodes of the vibrator substrate 20 on the vibrator substrate wafer 200 are formed by using a photolithography technique and an etching technique or a sand blast method. Similarly, a plurality of first and second substrates 30 and 40 as shown in FIGS. 1 and 2 are arranged in alignment on the first and second substrate wafers 300 and 400, respectively, and the shape and electrodes are photolithography. It is formed using a technique and an etching technique or a sandblasting method.

  First and second bonding portions 50 and 60 are formed at bonding portions of the vibration substrate wafer 200 and the first and second substrate wafers 300 and 400. The first and second joint portions 50 and 60 according to the present embodiment use Au—In eutectic alloy.

  Here, when an Au—In eutectic alloy is formed at the joint between the vibrator substrate wafer 200 and the first and second substrate wafers 300 and 400, a high melting point (1064 degrees) metal Au layer is formed on the first and second Au layers. A low-melting-point metal In layer is formed on the surface of the Au layer formed on at least one of the substrates. By forming the Au layer on both substrates, TLP bonding between Au and In can be promoted. In addition, the manufacturing process can be reduced by forming the In film on one of the substrates.

  FIG. 5 is a partially enlarged view showing a process of forming an Au—In eutectic alloy. In this embodiment, the composition ratio (wt%) of the Au—In eutectic alloy is Au: In = 59: 41, which is the composition ratio of the eutectic point. The vibrating body substrate 20 is subjected to a plurality of processes including a photolithography technique, an etching technique, a sandblasting method, and the like, and the vibrating body 21 and a frame body 22 that surrounds the vibrating body 21 with a predetermined interval from the outer periphery of the vibrating body 21. Further, the excitation electrodes 26A and 26B and the routing electrodes 27A and 27B must be formed. Therefore, the structure is formed on the first and second substrate wafers 300 and 400 having a simple structure as compared with the vibration substrate wafer 200. It is desirable to do.

  In order to improve the adhesion of the Au layer, first, the Cr layer 51 having high adhesion with the quartz substrate is formed on the first and second substrate wafers 300 and 400 in order to form the first and second bonding portions 50 and 60. Thereafter, the Au layer 52 is formed on the Cr layer 51 having high adhesion with Au.

  The Au layer 53 formed on the front and back surfaces of the frame body 22 of the vibration body substrate wafer 200 (vibration body substrate 20) is formed along the rectangular frame body 22, and first, a Cr layer 54 as a base layer is formed, and then A laminated structure in which the Au layer 53 is formed. The Au layer 53 is formed at a predetermined interval so as not to short-circuit the connection electrodes 25A and 25B and the routing electrodes 27A and 27B.

Next, the In layer 55 is formed on the Au layer 52 of the first and second substrates 30 and 40.
As shown in FIG. 4A, the vibrator substrate wafer 200 and the first substrate wafer 300 are bonded by TLP bonding. Specifically, when the laminated surfaces are formed by superimposing the bonding surfaces of both wafers, the first bonding portion 50 is formed from the top, as shown in FIG. 5, with a Cr layer 51, an Au layer 52, an In layer 55, an Au layer 53, A laminated structure of the Cr layer 54 is obtained. Then, by heating and pressing at a temperature equal to or higher than the melting point (about 156 degrees) of the In layer 55, for example, 200 degrees, the In layer 55 between the Au layers 52 and 53 is melted, and In is diffused into the Au layers 52 and 53. Thus, eutectic reaction is caused to form Au-In which is a eutectic alloy. At this time, since the In layer 55 of the Au layer 52 is eutectic alloyed by diffusion, there is no Au − between the Cr layer 54 on the vibrator substrate wafer 200 and the Cr layer 51 on the first substrate wafer 300. Only In eutectic alloys exist.

Next, the inventor of the present application paid attention to the bonding reliability and tried diligently to study the optimal composition ratio of the Au—In eutectic alloy from the viewpoint of bonding strength.
FIG. 6 is published in the academic paper “GOLD-INDIUM TRANSIENT LIQUID PHASE (TLP) WAFER BONDING FOR MEMS VACCUM PACKAGING (MEMS 2008, Tucson, AZ, USA, January 13-17, In). FIG. As shown in the state diagram, in the vicinity of the eutectic point of 500 degrees, there are triclinic Au—In having a eutectic structure and cubic Au—In ₂ having a eutectic structure. Au—In is in the hypoeutectic composition region with respect to the eutectic point, and Au—In ₂ is in the hypereutectic composition region with respect to the eutectic point. From this phase diagram, it can be seen that the melting point of Au—In is 509 degrees and the melting point of Au—In ₂ is 540.7 degrees. As for the composition ratio at each melting point, Au—In is Au: In = 63.2: 36.8 wt%, and Au—In ₂ is Au: In = 46.2: 53.8 wt%.

Next, the eutectic alloy formed by TLP bonding was analyzed. FIG. 7 is a view of an Au—In eutectic alloy formed by TLP bonding.
As shown in the figure, according to the SEM analysis, a solid phase composed of Au—In ₂ and a solid phase composed of Au—In are mixed in the joint, and from the result of cross-sectional observation, Au—In ₂ is more Au— It has been found that the crystal grains have a very small and dense structure compared to In.

  If the composition ratio is not optimally controlled in the process of forming the eutectic alloy, an Au-In eutectic alloy consisting of two solid phases will be formed in this way, so phase separation occurs and bonding occurs. I faced a new problem that there was a risk of the part peeling off.

Therefore, as a result of repeated experimentation and evaluation analysis, the inventor of the present application has found that the content ratio of In in the Au—In eutectic alloy in order to obtain Au—In ₂ having a very small crystal grain and a dense structure or a solid phase close thereto. Was conceived to be at least 41 and 55 wt%.

Here, a case where In is out of the range of 41 to 55 wt% will be considered.
In the state diagram of FIG. 6, components Ca (components of Au—In eutectic alloy), Cb (components of Au—In ₂ eutectic alloy), Cc (components of temperature T1), C0 (Ca and Cb) of each composition ratio. ) And C1 (region having a higher In composition than Cb), the ratio of phases in the molten state is examined.

In the component C0 in A in the figure, the Au—In phase and the Au—In ₂ phase are mixed at the following ratio.
_{Au-In: Au-In 2} = (Cb-C0) :( C0-Ca)
Therefore, the ratio of Au-an In _2-phase increases if the alloy close to the composition ratio of Au-In _2.

In the component C1 in B in the figure, the ratio of the In liquid phase to the In solid phase at the temperature T1 is as follows.
In liquid phase: In solid phase = (Cc-C1): (C1-Cb)
In this case, the Au—In phase and the Au—In ₂ phase are mixed at the above ratio.

Here, since the atomic weights of Au and In are 197 for Au and 114.8 for In, respectively, the weight concentration (%) of In in each of Au—In and Au—In ₂ is calculated as follows. The
Ratio of In to Au-In = 11.4 / (197 + 114.8) = 36.8%
Ratio of In to Au—In ₂ = (114.8 × 2) / (197 + 114.8 × 2) = 53.8%

Therefore, since the eutectic alloy in the component Cb is Au—In ₂ , the composition ratio is Au: In = 46.2: 53.8.
It becomes. Here, in the equilibrium diagram shown in FIG. 6, when the In composition ratio is 53.8% or more, the solid phase and the liquid phase are mixed at 156 degrees or more, that is, the melting occurs at 156 degrees or more. Will exist.

On the other hand, when it becomes 40 wt% or less, the solid phase of Au—In ₂ is considerably reduced, and the solid phase of Au—In occupies most.
On the other hand, since the eutectic alloy in the component Ca is Au—In, the composition ratio of In is 36.8% as described above.

FIG. 8 is an equilibrium diagram of Au and In published in Seizo Nagasaki and Satoshi Hirabayashi, “Binary Alloy Phase Diagrams”, Agne Technical Center. When the In ratio decreases from 36% and the Au ratio increases, the Au ₇ -In ₃ phase exists particularly at a composition ratio of Au: In = 80: 20, so the In ratio is 36 If it falls below%, it becomes a region where Au—In phase and Au ₇ -In ₃ coexist, and it becomes a region where there is almost no Au—In ₂ phase.

That is, when Au is diffused into 100% In and alloying proceeds while gradually increasing the composition ratio of Au, an Au—In ₂ phase is first formed. As the diffusion further proceeds, an Au—In phase is formed. As the diffusion further proceeds, an Au ₇ -In ₃ phase is formed.

Therefore, if the In ratio decreases from 36.8%, the Au ₇ -In ₃ phase ratio increases.
Therefore, if Au remains in the joint, diffusion proceeds and a eutectic alloy phase is formed while changing the composition ratio. Therefore, the diffusion of Au and In with the composition ratio of Au—In ₂ phase. there will be completed and the Au-an in _2-phase at a high alloy phase than the composition ratio of the ratio of Au in the (alloy phase on the left side of the Au-an in ₂ in the figure) may be so as not to be formed. That is, the composition ratio may be adjusted so that an Au—In ₂ eutectic alloy phase is formed when all of Au diffuses. The composition ratio at this time is Au: In = 46.2: 53.8 wt%.

Therefore, by making the content ratio of In in the Au—In eutectic alloy at least 36.8 or more and 53.8 wt% or less, it is possible to realize a dense structure with extremely small crystal grains, thereby significantly improving the bonding reliability. It became possible to make it.
More preferably, as the eutectic alloy of Au and In, Au—In ₂ having a composition ratio of Au and In of 46.2: 53.8 wt% was found to be preferable because it is crystallinely stable.

  Next, as shown in FIG. 4B, the oscillation frequency of the vibrator substrate 20 is adjusted. Specifically, the mask 500 is arranged so that the excitation electrode 26 is exposed from the surface to which the second substrate wafer 400 is bonded. Then, the frequency is adjusted while monitoring the excitation electrode 26 by reducing the metal film by ion etching or adding mass by vapor deposition.

  Next, as shown in FIG. 4C, after adjusting the frequency, the vibrator substrate wafer 200 and the second substrate wafer 400 are bonded. Specifically, when the laminated surface is formed by superimposing the bonding surfaces of the two wafers, the second bonding portion 60 is similar to the first bonding portion 50 in that the Cr layer 54, the Au layer 53, the In layer 55, and the Au layer 52 from above. , A layered structure of Cr layers 51 is formed.

  The eutectic alloy of the second bonding portion 60 is formed by heating and pressing under the same conditions as the first substrate wafer 300, that is, at, for example, 200 degrees, which is about 156 degrees or more that is the melting point of the In layer 55. Moreover, the joining of the 2nd junction part 60 is airtightly sealed, for example by vacuum sealing or inert gas atmosphere. At this time, since the eutectic point of the first joint portion 50 is about 500 degrees due to the Au—In eutectic alloy, the first joint portion 50 is not melted by heating to melt the In layer 55 of the second joint portion 60.

When the laminated body of wafers laminated by such eutectic bonding is cut (diced) as shown by a dotted line in the figure, the piezoelectric vibrator 10 is obtained.
According to such an electronic component manufacturing method of the present invention, the step of forming the second joint can be performed under the same material and under the same conditions as the first joint. Further, the oscillation frequency of the vibrating body can be adjusted before the second substrate is bonded. Furthermore, since the first joint portion formed by the eutectic alloy formed by the first joining is higher than the joining temperature, the first joint portion is heated by the second joint or heat treatment such as reflow. Does not dissolve, there is no risk of airtight deterioration, and high-precision electronic parts can be manufactured.

  The eutectic alloy constituting the first and second joints may have a eutectic point higher than the heating temperature of heat treatment such as reflow of electronic parts. An Ag—In eutectic alloy (eutectic point of about 880 degrees), a Cu—In eutectic alloy (eutectic point of about 650 degrees), or the like can be applied.

  As described above, the electronic component formed by bonding using the Au—In eutectic alloy according to the present invention has a three-layer structure in which the upper and lower surfaces of the vibration substrate 20 are sandwiched between the first substrate 30 and the second substrate 40, respectively. Although the piezoelectric vibrator 10 has been described, the present invention can be applied to an electronic component as shown in FIG.

FIG. 9 is an explanatory view of a modification of the electronic component according to the present invention, in which (a) is a sectional view showing a first modification, and (b) is a sectional view showing a second modification.
As shown in the first modification of FIG. 9A, a frame-shaped sealing surface of a concave package (container) 72 in which a chip component (electronic element) such as a crystal resonator 70 is mounted is made of metal or glass. When sealing hermetically with a lid 74 made of quartz or the like, the sealing surface may be joined by forming an Au—In eutectic alloy 76.

  Further, as shown in the second modification of FIG. 9B, the frame-shaped sealing surface of the concave package 72 on which a plurality of chip parts 77a, 77b and the like are mounted is formed by a lid 74 made of metal, glass, crystal or the like. Needless to say, the sealing surface may be joined by forming the Au—In eutectic alloy 76 when sealing hermetically.

DESCRIPTION OF SYMBOLS 1 ......... Vibration body substrate, 2 ......... Board, 3 ......... Cr layer, 4 ......... Au layer, 5 ...... Sn layer, 10 ......... Piezoelectric vibrator, 20 ...... Vibration body substrate , 21... Vibrating body, 22... Frame, 23... Connecting part, 24... Projecting part, 25... Connection electrode, 26 ... Excitation electrode, 27. 30 ......... First substrate, 40 ......... Second substrate, 42 ......... Through hole, 44 ......... External electrode, 50 ...... First junction, 51 ......... Cr layer, 52 ......... Au layer, 53... Au layer, 54... Cr layer, 55... In layer, 60... ... Lid, 76 ......... Au-In eutectic alloy, 77 ......... Chip component, 100 ......... Quartz crystal, 120 ......... Vibrator substrate, 121 ...... Frame, 130 ... , ... Lid substrate, 150 ......... Eutectic alloy, 160 ......... Piezoelectric diaphragm with frame, 162 ......... First case, 163 ......... Second case, 164 ......... Bonding, 165... Bonding, 200... Vibrating substrate wafer, 300... First substrate wafer, 400 ... Second substrate wafer, 500.

Claims (8)

An electronic component formed by joining two or more members to be joined together with metal metallization on each joint surface, and joining the joint surfaces with a brazing material interposed therebetween,
The brazing material is In;
An electronic component, wherein the joint is a eutectic alloy formed by diffusion of the metal metallization and the In.   2. The electronic component according to claim 1, wherein the electronic component comprises two members to be joined, one being a container for accommodating an electronic element and the other being a lid for sealing an opening of the container.   The first case and the second case are composed of three members to be bonded, the first member to be bonded is an electronic element layer, and the second and third members to be bonded hold the upper and lower surfaces of the electronic element layer, respectively. The electronic component according to claim 1, wherein the electronic component is a case.   The electronic component according to any one of claims 1 to 3, wherein at least a surface layer of the metal metallization is Au.   5. The electronic component according to claim 4, wherein the eutectic alloy has an In content ratio of 36.8 to 53.8 wt%.   6. The electronic component according to claim 4, wherein a composition ratio of Au and In constituting the eutectic alloy is Au: In = 46.2: 53.8 (wt%). The electronic component according to claim 4, wherein the eutectic alloy is Au—In ₂ . A method for manufacturing an electronic component according to any one of claims 1 to 7,
Forming a layer made of brazing material on the surface of the metal metallization of any one of the facing members to be joined;
A step of making a laminate in which the joining surfaces of the members to be joined are opposed to each other, and
Heating and pressurizing the laminate at a temperature at which the brazing material melts, and diffusing the brazing material into the metallized layer, thereby joining the joint surfaces to each other;
The manufacturing method of the electronic component characterized by including.