JP2006185966A - Electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable electronic device with high accuracy so as not to vary the frequency characteristics of a SAW chip even in the addition of heat load to the device without including environmental pollutants. <P>SOLUTION: In the electronic device, an annular metal layer 7 is formed in an upper surface periphery over all the circumferences, while forming an input-and-output electrode 5 in the upper surface central part of a ceramic substrate 4. An element of input-and-output electrodes 2 formed in the undersurface central part of an electronic circuit element 1 at input-and-output electrodes 5, while carrying out flip chip junction via a jointing material 8. An element annular metal layer 3 formed in the annular metal layer 7 at the undersurface periphery of electronic circuit element 1 is joined over all the circumferences via a sealing material 9. The jointing material 8 and the sealing material 9 are constituted of the solder which makes a tin-silver alloy a main ingredient or makes a tin-silver-copper a main ingredient by containing gold, nickel and cobalt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to hermetic sealing of an electronic device in which an electronic circuit element is flip-chip bonded onto a ceramic substrate.

  A surface acoustic wave device used as a high frequency filter for a cellular phone or the like is a comb-like electrode on the surface of a piezoelectric single crystal chip (hereinafter referred to as SAW chip) such as lithium tantalate (LiTaO3) or lithium niobate (LiNbO3). A pair is formed and mounted on a package substrate, and the input / output electrodes of the package substrate are electrically connected to the comb-shaped electrode pair.

  Usually, a SAW chip is die-bonded to a ceramic package substrate with a chip surface on which surface acoustic waves propagate, that is, a surface on which a comb-like electrode pair is formed, and an element input / output electrode connected to the comb-like electrode pair and its package substrate These input / output electrodes are electrically connected by bonding with a metal wire mainly composed of aluminum (Al) or gold (Au). Thereafter, the surface acoustic wave device is constructed by hermetically sealing with a metallic cap.

  However, in recent years, there has been a strong demand for miniaturization of parts such as mobile phones, and surface acoustic wave devices have been miniaturized by omitting wire bonding regions by flip-chip connecting a SAW chip to a package substrate.

  When bonding a semiconductor chip to a substrate using solder as in Patent Document 1 below, the high-temperature solder that has been used in the past is designated as an environmental pollutant and contains lead. When an electronic device using tin-lead (Sn—Pb) solder is disposed or left outdoors and exposed to wind and rain, there is a risk that lead will dissolve in the environment and pollute the environment. For this reason, in recent years, there has been a demand for a bonding material containing no lead in the growing global environmental protection movement.

Therefore, in Patent Document 2 below, an electronic device in which an electronic circuit element is flip-chip connected to a substrate as a structure that can be hermetically sealed includes an element input / output electrode of the electronic circuit element and an input / output electrode of a ceramic substrate. The gap is bonded with gold-tin (Au-Sn) or conductive glass, and the peripheral portion of the electronic circuit element and the substrate facing it are bonded and sealed by the same connection method as the input / output electrodes. A featured electronic device structure has been proposed.
JP-A-4-29311 JP 2004-214469 A

However, in general, the thermal expansion coefficient of the substrate material (for example, the thermal expansion coefficient of alumina ceramics is about 7 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of the electronic circuit element (for example, the thermal expansion coefficient of lithium tantalate depends on the crystal orientation). Although there is a large gap between 1.6 × 10 ^{−6 to} 4.1 × 10 ⁻⁶ / ° C., if a thermal load such as a thermal shock is applied to such a flip chip package device, the junction is Stress is applied. Conventionally, it has been joined with a soft lead-tin (Pb-Sn) alloy that relieves stress, but because it contains lead, which is an environmentally hazardous substance, a gold-tin (Au-Sn) alloy that does not contain lead is used. May be used.

  However, when the electronic circuit element and the substrate are flip-chip bonded with a hard material such as an Au—Sn alloy, the stress cannot be relieved, and the element input / output electrodes of the electronic circuit element generally weaker than the substrate material In this case, stress due to the difference in thermal expansion coefficient is applied as it is, and there is a problem that the frequency characteristics of the SAW chip are shifted due to distortion applied to the electronic circuit element.

  If the substrate material is made of a weak strength glass epoxy substrate or the like, no distortion is applied to the electronic circuit element, but the airtightness is lowered and the long-term reliability of the electronic device is lowered.

  As described above, the conventional flip chip package has a problem of adverse effects on the environment and frequency characteristics. Therefore, the electronic device of the present invention has been completed in view of the above-mentioned problems, and its purpose is high accuracy that does not contain environmental pollutants and does not shift the frequency characteristics of the SAW chip even when a thermal load is applied to the device. And development of highly reliable electronic devices.

  In the electronic device according to the present invention, an input / output electrode is formed at the center of the upper surface of the ceramic substrate, and an annular metal layer is formed on the outer periphery of the upper surface, and the input / output electrode is formed at the center of the lower surface of the electronic circuit element. An electronic device in which element input / output electrodes are flip-chip bonded via a bonding material, and an annular metal layer formed on the outer peripheral portion of the lower surface of the electronic circuit element is bonded to the annular metal layer over the entire circumference via a sealing material. The bonding material and the sealing material are formed of a solder containing a tin-silver alloy as a main component or a solder containing a tin-silver-copper alloy as a main component containing gold, nickel and cobalt. It is characterized by that.

  The electronic device of the present invention is preferably characterized in that the content of gold contained in the sealing material is lower than the content of gold contained in the bonding material.

  The electronic device of the present invention is preferably characterized in that the content of nickel contained in the sealing material is lower than the content of nickel contained in the bonding material.

  The electronic device of the present invention is preferably characterized in that the content of cobalt contained in the sealing material is lower than the content of cobalt contained in the bonding material.

  The electronic device of the present invention is an element in which an input / output electrode is formed at the center of the upper surface of the ceramic substrate and an annular metal layer is formed on the entire periphery of the upper surface, and the input / output electrode is formed at the center of the lower surface of the electronic circuit element. An electronic device in which an input / output electrode is flip-chip bonded via a bonding material and an annular metal layer formed on the lower peripheral portion of the electronic circuit element is bonded to the annular metal layer over the entire circumference via a sealing material, Because the bonding material and the sealing material are made of solder containing tin-silver alloy as the main component or solder containing tin-silver-copper alloy as the main component, containing gold, nickel and cobalt. The stress generated by the difference in the thermal expansion coefficient between the electronic circuit element and the ceramic substrate when the electrode part and the sealing part are joined is absorbed by the plastic deformation of the joining solder. Reflow at the time of board mounting is achieved by forming Sn—Au alloy, Sn—Ni alloy, and Sn—Co alloy in the solder. Even if a temperature of about 250 ° C. is applied, the airtightness of the bonded solder is not broken and the electronic device is excellent in heat resistance.

  In the electronic device of the present invention, preferably, the content of gold contained in the sealing material is lower than the content of gold contained in the bonding material, so that the sealing material contains gold compared to the bonding material. Therefore, the sealing material is more excellent in fluidity and adhesion, and becomes an electronic device with higher adhesion strength.

  In the electronic device of the present invention, preferably, the content of nickel contained in the sealing material is lower than the content of nickel contained in the bonding material, so that the sealing material contains nickel compared to the bonding material. Since the effect of increasing the hardness due to this is small, the sealing material is softer and more excellent in fatigue resistance, so that an electronic device with higher thermal shock reliability is obtained.

  In the electronic device of the present invention, preferably, the content of cobalt contained in the sealing material is lower than the content of cobalt contained in the bonding material, so that the sealing material contains cobalt compared to the bonding material. Since the effect of increasing the hardness due to this is small, the sealing material is softer and more excellent in fatigue resistance, so that an electronic device with higher thermal shock reliability is obtained.

  Next, an electronic device according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of an electronic device of the present invention, and FIG. 2 is an enlarged view of a sealing portion of the electronic device of the present invention. 1 is an electronic circuit element, 2 is an element input / output electrode of the electronic circuit element 1, and 3 is an element annular metal layer formed in an annular shape around the entire circumference of the electronic circuit element. 4 is a ceramic substrate, 5 is an input / output electrode formed on the surface of the ceramic substrate 4, 6 is an external electrode for board mounting, and 7 is an annular metal layer formed in an annular shape around the entire circumference of the ceramic substrate. .

  8 is a bonding material for bonding the element input / output electrode 2 and the input / output electrode 5, and 9 is a sealing material for bonding the element annular metal layer 3 and the annular metal layer 7.

The element input / output electrode 2 formed on the surface of the electronic circuit element 1 includes an adhesion metal layer 2a made of Ti, Cr, Ta, Nb, Ni—Cr alloy, Ta ₂ N, etc. from the electronic circuit element 1 side, Pt, Pd, It comprises a diffusion preventing layer 2b made of Rh, Ru, Ni, Ni—Cr alloy, Ti—W alloy, Ni—Co alloy or the like, and a main conductor layer 2c made of Au, Cu, Ni, Ag or the like.

An element annular metal layer 3 formed annularly on the outer periphery of the electronic circuit element 1 is an adhesion metal layer made of Ti, Cr, Ta, Nb, Ni—Cr alloy, Ta ₂ N, or the like from the electronic circuit element 1 side. 3a, a diffusion preventing layer 3b made of Pt, Pd, Rh, Ru, Ni, Ni—Cr alloy, Ti—W alloy, Ni—Co alloy or the like, and a main conductor layer 3c made of Au, Cu, Ni, Ag or the like. ing.

  The input / output electrodes 5 formed on the surface of the ceramic substrate 4 are made of a metal layer 5a made of W or Mo—Mn, a base metal layer 5b made of Ni, Ni—Cr alloy, Ni—Co alloy, or the like from the ceramic substrate 4 side. The main conductor layer 5c.

  An annular metal layer 7 formed in an annular shape on the outer periphery of the ceramic substrate 4 is a base metal layer made of a metallized layer 7a of W or Mo—Mn, Ni, Ni—Cr alloy, Ni—Co alloy or the like from the ceramic substrate 4 side. 7b, a main conductor layer 7c made of Au.

When the electronic circuit element 1 is a SAW filter, for example, a SAW chip such as lithium tantalate (LiTaO ₃ ) or lithium niobate (LiNbO ₃ ) is cut and polished into a thin plate shape, and then comb teeth for forming the SAW filter are used. The pattern / element input / output electrode 2 and element annular metal layer 3 are formed in a desired shape by a photolithography method or the like by forming an adhesion metal layer, a diffusion prevention layer, and a main conductor layer by a conventionally known vacuum deposition method or sputtering method. And cut it into pieces.

  The adhesion metal layers 2a and 3a are for improving adhesion with the electronic circuit element 1, and the thickness is preferably in the range of 0.01 to 0.5 μm. When the thickness of the adhesion metal layers 2a and 3a is less than 0.01 μm, the adhesion strength with the electronic circuit element 1 tends to decrease, and when the thickness exceeds 0.5 μm, the film stress becomes large and peels from the electronic circuit element 1. It tends to be easier.

  The diffusion preventing layers 2b and 3b are used for soldering when the element input / output electrode 2 and the element annular metal layer 3 are connected to the input / output electrode 5 and the annular metal layer 7 of the ceramic substrate 4 through a brazing material such as solder. It is for preventing diffusion, and the thickness is preferably in the range of 0.5 to 2 μm. When the thickness of the diffusion preventing layers 2b and 3b is less than 0.5 μm, the brazing material tends to diffuse into the adhesion metal layers 2a and 3a, and the adhesion with the insulating substrate 2 tends to be lowered, and when the thickness exceeds 2 μm, The film stress of the diffusion preventing layers 2b and 3b becomes large and tends to be easily peeled off from the adhesion metal layers 2a and 3a.

  The main conductor layers 2c and 3c are soldered when the element input / output electrode 2 and element annular metal layer 3 are connected to the input / output electrode 5 and annular metal layer 7 of the ceramic substrate 4 through a brazing material such as solder. In order to improve the wettability with the brazing filler metal, the thickness is preferably in the range of 0.1 to 0.5 μm. When the thickness of the main conductor layers 2c and 3c is less than 0.1 μm, the wettability with a soldering material such as solder tends to decrease. When the thickness exceeds 0.5 μm, the film stress increases and the diffusion preventing layer 18 There is a tendency to peel easily.

The ceramic substrate 4 is, for example, alumina (Al ₂ O ₃ ) ceramics, mullite (3Al ₂ O ₃ .2SiO ₂ ) ceramics, aluminum nitride (AlN) ceramics, silicon carbide (SiC) ceramics, silicon nitride (Si ₃ N ₄ ). Inorganic materials such as ceramics are used.

  For example, if the ceramic substrate 4 is made of alumina ceramic, a suitable organic binder, solvent, plasticizer, dispersant, etc. are added to and mixed with the aluminum oxide raw material powder to produce a slurry, Conventionally known sheet forming methods such as the doctor blade method and the calender roll method are adopted to form into a sheet shape to obtain ceramic green sheets (also called ceramic green sheets), and then electrically connected to these ceramic green sheets. In order to carry out, a well-known screen printing method using a metal paste obtained by adding a suitable organic solvent, solvent, plasticizer, etc. to refractory metal powder such as tungsten, molybdenum, manganese, etc. for metallized wiring layers and through conductors Etc., and by stacking a plurality of them as necessary, a high temperature of about 1600 ° C. In the production by firing.

  The metallized layers 5a and 7a are formed by depositing a base metal layer 5a or 7b having excellent corrosion resistance such as nickel on the exposed outer surface to a thickness of 1 to 20 μm by a plating method, and corrosion resistance such as gold. If the main conductor layers 5a and 7c having excellent conductivity and good conductivity are deposited to a thickness of 0.1 to 2 μm by plating, the metallized layer 7a is effectively prevented from oxidative corrosion and metallized wiring. When the layer 5 is brazed to the wiring conductor of the external electric circuit board via a brazing material such as solder, the brazing strength can be strengthened.

  Cream solder mainly composed of tin-silver alloy or cream solder mainly composed of tin-silver-copper alloy is applied to the input / output electrodes 5 and the annular metal layer 7 of the ceramic substrate 4 by a conventionally known screen printing method or the like. Then, the bonding material 8 and the sealing material 9 are formed by melting and bonding by heating. When the same solder is used for the bonding material 8 and the sealing material 9, they may be applied and formed at a time.

  The solder mainly composed of the tin-silver alloy and the solder mainly composed of a tin-silver-copper alloy according to the present invention is a tin-silver alloy content of 50% by mass or more, or a tin-silver-copper alloy. This means solder with a content of 50% by mass or more.

  Then, the input / output electrode 2 and the element annular metal layer 3 of the electronic circuit element 1 are heated and joined to the input / output electrode 5 and the annular metal layer 7 of the ceramic substrate through the bonding material 8 and the sealing material 9, respectively. The bonding material 8 and the sealing material 9 are electronic devices formed of solder containing tin-silver alloy as a main component or solder containing tin-silver-copper alloy as a main component containing gold, nickel and cobalt. It becomes.

  The gold content in the bonding material 8 is preferably 0.1 to 15% by mass of gold when the entire bonding material 8 is 100% by mass. If the gold content is less than 0.1% by mass, the surfaces of the element input / output electrode 2 and the input / output electrode 5 are likely to be oxidized, and the bonding material 8 is poorly wetted. . When the amount of gold exceeds 15% by mass, a large amount of gold-tin alloy having a high melting point is generated in the bonding material 8, so that the fluidity tends to deteriorate and the reliability of bonding tends to decrease.

  As for the gold content rate in the sealing material 9, 0.1-10 mass% of gold is preferable when the sealing material 9 whole is 100 mass%. When the gold content is less than 0.1% by mass, the surface of the element annular metal layer 3 or the annular metal layer 7 is likely to be oxidized, and the sealing material 9 is poorly wetted. Tend. When the amount of gold exceeds 10% by mass, a lot of gold-tin alloy having a high melting point is generated in the sealing material 9, so that the fluidity is deteriorated and the reliability of hermetic sealing tends to be lowered.

  When the gold content in the sealing material 9 is 20 to 60% compared to the gold content in the bonding material 8, the gold content in the sealing material 9 is higher than that in the gold-tin alloy generated in the bonding material 8. Since the amount of the gold-tin alloy produced in the second layer is less fluid, the sealing material 9 is more fluid than the bonding material 8, so that it is difficult for the bonding material 8 to be subjected to a load such as a thermal shock. This is more preferable because the hermetic seal reliability is higher.

  The nickel content in the bonding material 8 is preferably 0.05 to 20% by mass of nickel when the entire bonding material 8 is 100% by mass. When nickel is less than 0.05% by mass, there is little generation of a nickel-tin alloy having a high melting point in the bonding material 8, and thus the heat resistance of bonding tends not to be sufficiently improved. When nickel exceeds 20% by mass, a large amount of nickel-tin alloy having a high melting point is generated in the bonding material 8, so that the fluidity tends to deteriorate and the reliability of bonding tends to decrease.

  The nickel content in the sealing material 9 is preferably 0.05 to 15% by mass of nickel when the entire sealing material 9 is 100% by mass. When nickel is less than 0.05% by mass, there is a tendency that the heat resistance of the hermetic seal does not sufficiently increase because there is little formation of a nickel-tin alloy having a high melting point in the sealing material 9. When nickel exceeds 15% by mass, a large amount of nickel-tin alloy having a high melting point is generated in the sealing material 9, so that the fluidity is deteriorated and the reliability of hermetic sealing tends to be lowered.

  When the nickel content in the sealing material 9 is 20 to 60% compared to the nickel content in the bonding material 8, the nickel content in the sealing material 9 is greater than the nickel-tin alloy produced in the bonding material 8. Since the amount of the nickel-tin alloy produced in the metal is small and the fluidity of the sealing material 9 is higher than that of the bonding material 8, it is difficult for the bonding material 8 to be subjected to a load such as a thermal shock. This is more preferable because the hermetic seal reliability is higher.

  The cobalt content in the bonding material 8 is preferably 0.01 to 3% by mass of cobalt when the entire bonding material 8 is 100% by mass. When cobalt is less than 0.01% by mass, since there is little production of a cobalt-tin alloy having a high melting point in the bonding material 8, there is a tendency that the heat resistance of the bonding does not sufficiently increase. When cobalt exceeds 3 mass%, a lot of cobalt-tin alloy having a high melting point is generated in the bonding material 8, so that the fluidity is deteriorated and the reliability of bonding tends to be lowered.

  As for the cobalt content rate in the sealing material 9, when the whole sealing material 9 shall be 100 mass%, 0.01-2 mass% of cobalt is preferable. When cobalt is less than 0.01% by mass, the heat resistance of the hermetic seal tends not to be sufficiently improved because there is little production of a cobalt-tin alloy having a high melting point in the sealing material 9. When cobalt exceeds 2 mass%, a lot of cobalt-tin alloy having a high melting point is generated in the sealing material 9, so that the fluidity is deteriorated and the reliability of hermetic sealing tends to be lowered.

  Compared to the cobalt content in the bonding material 8, the cobalt content in the sealing material 9 is 20 to 60%. In the sealing material 9 than the cobalt-tin alloy produced in the bonding material 8. Since the amount of the cobalt-tin alloy produced in the metal is small, the fluidity of the sealing material 9 is higher than that of the bonding material 8, so that it is difficult to apply a load such as a thermal shock to the bonding material 8. This is more preferable because the hermetic seal reliability is higher.

  Here, cream solder was used, but the plate-like solder was punched into a frame or circle, placed on the annular metal layer 7 or the input / output electrode 5, and the electronic circuit element 1 was placed thereon and heated to join. May be.

  Further, the element input / output electrode 2 and the element annular metal layer 3 of the electronic circuit element 1 may be formed in a separate process from that for forming the comb pattern. When formed in a separate process, it can be made by changing the metal layer composition and metal of the element input / output electrode 2 and the element annular metal layer 3, and the diffusion preventing layer of the element annular metal layer 3 and the gold, nickel, cobalt of the main conductor layer By changing the ratio and thickness, the contents of gold, nickel, cobalt, etc. in the bonding material 8 and the sealing material 9 of the completed electronic device can be manipulated. Moreover, when it is created in a separate process, it is possible to form the adhesion metal layer so as to be completely covered with the diffusion prevention layer or the main conductor layer as shown in FIG. be able to.

  In addition, the main conductor layers 2c, 3c, 5c, and 7c may be completely diffused into the solder, and in this case, the configuration near the bonding material 8 may be without the main conductor layer as shown in FIG. There is.

  In order to control the content of gold, nickel, cobalt, etc. in the bonding material 8 and the sealing material 9 of the electronic device, the element input / output electrode 2 and the element annular metal layer 3 of the electronic circuit element 1 It is possible to operate by changing the areas of the input / output electrodes 5 and the annular metal layer 7 of the ceramic substrate 4, and it is possible to provide an electronic device according to the required reliability.

It is sectional drawing which shows an example of embodiment of the electronic device of this invention. It is an expanded sectional view of the sealing part of the electronic device of the present invention. It is an expanded sectional view of the sealing part of the other example of the electronic device of this invention. It is an expanded sectional view of the sealing part of the other example of the electronic device of this invention.

Explanation of symbols

1: Electronic circuit element 2: Element input / output electrode 3: Element annular metal layer 4: Ceramic substrate 5: Input / output electrode 7: Ring metal layer 8: Bonding material 9: Sealing agent

Claims (4)

An input / output electrode is formed at the center of the upper surface of the ceramic substrate, and an annular metal layer is formed around the entire periphery of the upper surface, and an element input / output electrode formed at the center of the lower surface of the electronic circuit element is bonded to the input / output electrode. And an electronic device in which the annular metal layer formed on the outer peripheral portion of the lower surface of the electronic circuit element is joined to the entire circumference of the annular metal layer through a sealing material, the bonding material and An electronic device, wherein the sealing material is formed of a solder containing a tin-silver alloy as a main component or a solder containing a tin-silver-copper alloy as a main component and containing gold, nickel and cobalt. The electronic device according to claim 1, wherein a content ratio of gold contained in the sealing material is lower than a content ratio of gold contained in the bonding material. The electronic device according to claim 1, wherein a content ratio of nickel contained in the sealing material is lower than a content ratio of nickel contained in the bonding material. 4. The electronic device according to claim 1, wherein a content ratio of cobalt contained in the sealing material is set lower than a content ratio of cobalt contained in the bonding material. 5.

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