JP5764355B2 - Electronic component and manufacturing method thereof - Google Patents

Description

  The present invention relates to a surface mount electronic component and a method for manufacturing the same.

  Electronic parts such as quartz resonators are used as reference oscillation sources for electronic devices, clock sources for microcomputers, and the like.

  The crystal resonator is mainly a surface-mount electronic component configured by enclosing a crystal resonator element in a small surface-mount package that is hollow and hermetically sealed in a vacuum.

  As a conventional small-sized surface-mounted package that is hermetically sealed in a hollow state, a surface-mounted package in which a lid made of glass or metal is bonded to a container made of a brittle material such as ceramics, glass, or crystallized glass has been manufactured.

  In a crystal resonator using such a package, a glass or metal lid is bonded to a substrate with a bonding material, and the external electrode and the internal electrode are connected by a through electrode. The internal electrode is connected to the quartz crystal resonator element by a connecting material. The substrate is made of ceramic, glass, crystallized glass, or the like.

  In the case of ceramics, it is common to perform electroplating on a thick film conductor, but glass, crystallized glass, and the like cannot perform a high temperature process using a thick film conductor. Moreover, since glass and crystal glass are brittle and easily chipped, electroplating by barrel plating cannot be used. For this reason, the external electrode is generally formed by sputtering with a three-layer structure of Cr, Ni, and Au (Patent Document 1). FIG. 6 shows the structure of the three-layered external electrode in detail.

  The external electrode is selected from a base metal layer 12 selected from Cr, Ti, etc., which has good adhesion to the substrate 1 made of glass or the like, and Ni, Pt, etc. that are connected to the solder on the base electrode layer 12 And a protective metal layer 14 formed of Au, Ag, Sn, etc., which prevents the solder metal layer 13 from being oxidized on the solder metal layer 13 and quickly dissolves in the solder during soldering. Consists of

  At this time, a Cr-Ni-Au three-layer structure is most often used as an external electrode. In this case, Ni can be firmly joined by forming an intermetallic compound by alloying with Sn in the solder.

  In such a crystal resonator, the external electrode is connected and fixed to the land of the circuit board of the electronic device by solder and mounted on the electronic device together with the circuit board.

Special Table 2007-528591

  By the way, in the case of the electrode in which the soldering metal layer is formed of Ni, Ni forms an intermetallic compound with Sn or Cu constituting the solder, but there is a problem that this intermetallic compound is brittle. Further, at this time, the interface between the solder and the external electrode becomes an irregular shape, and the electronic component is easily broken by an impact such as dropping. There is also a problem that the electronic component is detached from the circuit board of the electronic device.

  In particular, lead-free solders with a high Sn content are prone to the above problems because the formation and growth of intermetallic compounds are remarkable.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the impact resistance of an external electrode in an electronic component.

  An electronic component according to the present invention, comprising: a substrate formed of a brittle material; a package including the substrate; an electronic element placed on the package; and an external electrode formed on the substrate. The external electrode includes a base metal layer formed on the substrate, a solder metal layer formed on the base metal layer, and a protective metal layer formed on the solder metal layer. The soldering metal layer is formed of an alloy of Ni and Co, and the amount of Co added is in the range of 0.01 wt% to 5 wt%.

  Thereby, the intermetallic compound formed in the joint surface of a solder and an external electrode can be knocked. Further, the joint surface between the solder and the external electrode can be formed in a smooth and dense structure. Thereby, the impact resistance of the electronic component can be improved.

  In addition, when the amount of Co added is in the range of 0.01% to 5% by weight, an intermetallic compound of Sn and a material containing Ni as a main component and also containing Co is formed at the interface with the solder. Can do. This intermetallic compound can be made thicker than the intermetallic compound of Sn and Ni or Sn and Co. Further, the joint surface between the solder and the external electrode can be formed in a smooth and dense structure. In addition, the formation of Ni at the interface of the intermetallic compound between the one containing Co as the main component and the metal constituting the solder suppresses the formation of the Ni intermetallic compound and suppresses the reduction in impact resistance. It is effective in suppressing the decrease in bonding force between Cr and Ni.

  In the electronic component according to the present invention, the base metal layer is Cr, Ti, or an alloy of Cr and Ti.

  Thereby, it is possible to improve the adhesion between the solder, particularly Sn as its main component, and the substrate 1 formed of a nonmetallic inorganic material without causing a reaction or dissolution near the soldering temperature.

  In the electronic component according to the present invention, the soldering metal layer is an alloy containing a metal constituting the base metal layer.

  Thus, by forming the solder metal layer from an alloy with the metal constituting the base metal layer, diffusion of the metal of the base metal layer into the solder metal layer is suppressed, and the base metal layer and the substrate Decrease in adhesion can be reduced. Moreover, reaction with solder can also be reduced.

  In the electronic component according to the present invention, the solder metal layer is an alloy further containing at least one metal selected from Mo, W, and Ta.

  Thereby, reaction with the solder of a Ni-Co alloy can be reduced. Moreover, the effect which makes a thermal expansion coefficient small and approximates the thermal expansion coefficient of glass is acquired. Therefore, Mo, W, and Ta do not form an intermetallic compound of Sn and Ni and suppress formation of an intermetallic compound of soldered metal at a temperature near the soldering temperature, that is, about 300 ° C. or less, like Cr and Ti. it can.

  In the electronic component according to the present invention, the thickness of the soldering metal layer is in a range of 0.1 μm to 0.6 μm.

  By setting the thickness, the film stress can be reduced, and the destruction of the external electrode 4 due to impact, stress or the like can be suppressed.

  In the electronic component according to the present invention, the substrate is soda glass. As a result, the cost of the package can be reduced.

  In the electronic component according to the present invention, the electronic element is a crystal vibrating piece.

  Further, in the method of manufacturing an electronic component according to the present invention, a substrate formed of a brittle material, a package including the substrate, an electronic element installed in the package, an external electrode formed on the substrate, In the method of manufacturing an electronic component, the step of forming a base metal layer on a substrate, the amount of Co added is in the range of 0.01 wt% to 5 wt%, and the solder is an alloy of Ni and Co The method includes the steps of forming an external electrode by a step of forming a solder metal layer on the base metal layer by sputtering and a step of forming a protective metal layer on the solder metal layer.

  According to the present invention, the intermetallic compound formed on the joint surface between the solder and the external electrode can be sticked. Further, the joint surface between the solder and the external electrode can be formed in a smooth and dense structure. Thereby, the impact resistance of the electronic component can be improved.

It is sectional drawing of the external electrode structure of the electronic component which concerns on this invention. It is sectional drawing of the electronic component which concerns on this invention. It is sectional drawing which shows the state which mounted the electronic component which concerns on this invention to the circuit board. It is sectional drawing of the electronic component which concerns on this invention.

  Below, the electronic component which concerns on 1st embodiment of this invention is demonstrated in detail using FIGS. 1-3.

  FIG. 1 is a view showing a cross section of an external electrode of an electronic component according to the present invention. FIG. 2 is a view showing a cross section of an electronic component including the external electrode of FIG. FIG. 3 is a view showing a cross section of the electronic component shown in FIG. 2 mounted on a circuit board. In the present invention, the electronic component is a surface-mount type electronic component.

  In the present embodiment, the electronic element 8 is a crystal vibrating piece, and the electronic component 100 is a crystal resonator.

  As shown in FIG. 2, the electronic component 100 includes a substrate 1 made of a brittle material, a package including the substrate 1, an electronic element 8 installed in the package, and an external electrode 4 formed on the substrate 1. And.

  In the present embodiment, the substrate 1 and the lid 2 constitute an electronic component package having a hollow structure inside. Further, the substrate 1 and the lid 2 are bonded via the bonding portion 3.

  The substrate 1 is made of a brittle material such as silicon or glass. In the case where the substrate 1 is silicon, it is used as a packaging material for micro parts mainly composed of etching called MEMS. In this case, since silicon as a package is processed by being integrated with electronic elements, mechanism elements, and the like to be mounted, silicon having particularly good process compatibility is used. On the other hand, when the substrate 1 is made of glass, it is used as an inexpensive substrate material for packages such as a crystal resonator and a SAW element.

  The lid 2 is made of ceramic, silicon, other inorganic single crystals, glass, metal, alloy, or the like.

  When the substrate 1 or the lid 2 is formed of glass, the cost can be reduced by using a thin soda glass manufactured by a float method. Soda glass is also called soda lime glass, and is glass mainly composed of silica (SiO 2), calcium carbonate, and sodium carbonate. Further, soda glass can be manufactured at low cost by a float method in which molten glass is poured onto a molten Sn bath. In addition, the float method makes it easy to produce a thin soda glass with good smoothness. Further, this soda glass has good polishing properties, and a smooth thin glass plate having a thickness of 0.2 mm to 0.5 mm can be obtained relatively easily. Further, soda glass has a thermal expansion coefficient close to that of a crystal resonator and is advantageous in terms of vibration characteristics. Further, by using glass for the substrate 1, fine adjustment of the frequency of the crystal resonator can be performed from the outside by a laser.

  The electronic element 8 is installed on the substrate 1 via the internal electrode 6 and the connection portion 7. The internal electrode 6 is electrically connected to the external electrode 4 through the through electrode 5. Note that the electronic element 8 is not necessarily installed on the substrate, and may be installed on the lid 2. At that time, the external electrode 4 is electrically connected by the lead-out electrode.

  The through electrode 5 has a structure in which a metal rod 15 such as a FeNi alloy, a Kovar alloy, a FeNiCr alloy, or a jumet wire is sealed with a glass frit 16. The through electrode 5 may be a thick film electrode obtained by filling a through hole with a thick film paste made of a metal or alloy such as Ag, AgPd, or AgPt and a glass frit that seals the metal or alloy.

  As this glass frit, lead-free low-melting glass, for example, lead-free low-melting glass whose working temperature is lowered by using bismuth oxide or the like is used, but this lead-free low-melting glass is very unstable and does not use a solution. Sputtering is convenient. Note that a conductive resin or the like can also be used for the through electrode 5 when vacuum sealing is not particularly required.

  A method for manufacturing the electronic component 100 according to the present invention will be described below.

  The electronic component 100 according to the present invention performs a process of forming the through electrode 5 in the through hole formed in the substrate 1.

  Next, a process of forming the internal electrode 6 on the substrate 1 is performed. The internal electrode 6 can be formed by plating, sputtering, or the like.

  Next, a step of installing the electronic element 8 on the internal electrode 6 is performed. The electronic element 8 uses an organic conductive adhesive as the connecting portion 7, uses Au-20 wt% Sn or other high-temperature solder as the connecting portion 7, and uses an Au bump as the connecting portion 7 for ultrasonic bonding. It connects with the internal electrode 6 by using it, or connecting it using a bump as the connection part 7.

  Thereafter, a lid 2 is placed on the substrate 1 to perform a process of forming a package. At this time, a hollow portion that is blocked from outside air is formed between the lid 2 and the portion of the substrate 1 where the electronic element 8 is provided. In this step, when the lid 2 is glass, the bonding to the substrate 1 can be anodic bonding or laser bonding for directly melting the glass. Further, the lid 2 and the substrate 1 can be joined by interposing a low melting point glass or the like as the joining portion 3 therebetween. Further, the lid 2 and the substrate 1 can be joined by laser joining with a laser light absorbing material as the joining portion 3. Further, a high temperature solder such as Au-20 wt% Sn solder can be used for the joint portion 3. Further, heating / pressure bonding can be performed using an organic resin for the bonding portion 3. When the lid 2 is a metal, welding with a brazing material is possible.

  In addition, in order to form the recessed part for forming space in the lid | cover 2, glass press molding can be utilized. Moreover, a recessed part can also be formed using an etching. Moreover, a recessed part can also be formed using sandblasting. Further, the lid 2 can be formed by forming a side wall by a thick film method. Further, there is a method such as bonding a glass preform as a side wall of the lid 2. The concave portion may be formed on the substrate 1 instead of the lid 2.

  Next, the process of forming the external electrode 4 on the surface opposite to the surface on which the internal electrode 6 is formed of the substrate 1 is performed. Thereby, the electronic component 100 can be formed.

  As shown in FIG. 3, the electronic component 100 formed as described above is connected to the land 10 on the electronic circuit board 11 by bonding the external electrode 4 and the solder 9. At this time, Pb-free solder can be used as the solder 9. In addition, the manufacturing method demonstrated is an example and is not limited to this.

  Hereinafter, the external electrode 4 will be described in detail with reference to FIG.

  In FIG. 1, the external electrode 4 includes a base metal layer 12 formed on the through electrode 5, a solder metal layer 13 formed on the base electrode 12, and a protective metal formed on the solder metal layer 13. Layer 14.

  The base metal layer 12 is Cr, Ti, or Cr which does not react or dissolve with solder, particularly Sn as its main component, near the soldering temperature and has good adhesion to the substrate 1 formed of a nonmetallic inorganic material. And an alloy of Ti. Since Cr is used for an excitation electrode of a crystal resonator element in a crystal resonator, it is compatible with the process and is particularly preferable.

  The thickness of the base metal layer 12 is preferably 0.01 μm or more and 0.3 μm or less. When the base metal layer 12 is 0.01 μm or less, there is a possibility that the adhesion to the glass is lowered due to diffusion with the soldering metal or the like. Moreover, when the base metal layer 12 is 0.3 micrometer or more, there exists a possibility that adhesiveness with glass may fall by film | membrane stress.

  Further, the soldering metal layer 13 is selected from an alloy that forms an intermetallic compound with Sn, contains Ni as a main component dissolved in Sn, and contains Co.

  The amount of Co added is in the range of 0.01% to 5% by weight. Hereinafter, in the present invention, the addition amount or content is all in weight percent.

  Even if the amount of Co added is less than 0.01% by weight or more than 5% by weight, the intermetallic compound has a smooth structure and does not provide a good characteristic.

  Therefore, when the addition amount of Co is in the range of 0.01 wt% to 5 wt%, the formed intermetallic compound may be sticky compared to the intermetallic compound of Sn and Ni or Sn and Co. it can. Further, the joint surface between the solder and the external electrode can be formed in a smooth and dense structure. In addition, the formation at the interface of the intermetallic compound between the main component of Ni, containing Co, and the metal constituting the solder 9 suppresses the formation of the intermetallic compound of Ni and suppresses the reduction in impact resistance. In addition, the suppression of decrease in bonding strength between Cr and Ni is improved.

  More preferably, the soldering metal layer 15 is formed of an alloy containing a metal constituting the base metal layer 12.

  The base metal layer 12 is made of Cr, Ti, or an alloy of Cr and Ti. That is, the soldering metal layer 13 is formed of a Ni—Co—Cr alloy or a Ni—Co—Ti alloy.

  Thus, by forming the soldering metal layer 13 from an alloy with the metal constituting the base metal layer 12, diffusion of the metal of the base metal layer 12 to the soldering metal layer 13 is suppressed, and the base metal layer Decrease in adhesion between the substrate 12 and the substrate 1 can be reduced. Moreover, reaction with solder can also be reduced.

  Further, the content of the metal constituting the base metal layer 12 of the soldering metal layer 13 is preferably in the range of 5 wt% to 40 wt%. When the content of the metal constituting the base metal layer 12 of the soldering metal layer 13 is less than 5%, the above effect is difficult to obtain, and when it is more than 40%, the bonding strength with the solder is lowered.

  The soldering metal layer 13 is an alloy containing at least one kind of metal among Mo, W, and Ta. That is, the soldering metal layer 13 is added with at least one kind of metal among Mo, W and Ta.

  Thereby, reaction with the solder of a Ni-Co alloy can be reduced. Moreover, the effect which makes a thermal expansion coefficient small and approximates the thermal expansion coefficient of glass is acquired.

  That is, like Cr and Ti, Mo, W, and Ta do not form an intermetallic compound of Sn and Ni at a temperature near the soldering temperature, that is, about 300 ° C. or less, and suppress formation of an intermetallic compound of a soldering metal. Note that the soldering metal layer 13 may be an alloy that does not include the metal constituting the base metal layer 12 and includes only at least one kind of metal among Mo, W, and Ta.

  The soda glass has a thermal expansion coefficient of 8 to 9 ppm / ° C., Cr of 6.2 ppm / ° C., and Ti of 8.4 ppm / ° C.

  On the other hand, Ni and Co have a coefficient of thermal expansion of 13.7 ppm / ° C. and 12.3 ppm / ° C., respectively, and have a larger coefficient of thermal expansion than that of glass or the metal of the base metal layer 12.

  Here, Mo, W, and Ta all have a thermal expansion coefficient of 5 ppm / ° C. or less. By alloying these metals with Ni to form the soldering metal layer 13, the thermal expansion coefficient of the soldering metal layer 13 can be close to that of the substrate 1 and the base metal layer 12.

  Moreover, in the soldering metal layer 13, adding at least one or more kinds of metals among Mo, W, and Ta as an alloy component can reduce the magnetism of the Ni—Co alloy. Therefore, it is convenient when the soldering metal layer 13 is formed by sputtering.

  Moreover, in the soldering metal layer 13, it is preferable that the total amount of addition of at least one of the metals constituting the base metal layer and Mo, W, and Ta is 50% or less. When it exceeds 50%, the bonding strength with the solder is lowered.

  Moreover, in the soldering metal layer 13, the addition amounts of Mo, W, and Ta are preferably 20% or less, 30% or less, and 22% or less, respectively. Within the above range, it is possible to have appropriate solder joint strength.

  As described above, when Cr, Ti, Mo, W, Ta having an effect of reducing the reaction between the soldering metal layer 13 and the solder is added to the soldering metal layer 13, the thickness of the soldering metal layer 13 is reduced. The thickness can be made thinner than when the above metal is not added. Specifically, the thickness can be 0.1 μm to 0.6 μm. Accordingly, the film stress can be reduced, and the destruction of the external electrode 4 due to impact, stress or the like can be suppressed.

  At this time, if the thickness of the soldering metal layer 13 is less than 0.1 μm, it also affects the base metal, and the adhesive strength between the substrate of the package and the base metal tends to be low. On the other hand, as the thickness of the soldering metal layer 13 increases, the soldering strength during soldering improves. However, it almost saturates near 0.5 μm, and when it becomes thicker than 0.6 μm, the film stress is large, and it tends to break down due to thermal stress, impact, or the like.

  Therefore, in this case, the thickness of the soldering metal layer 13 is preferably in the range of 0.1 μm to 0.6 μm.

  Lead-free solders with a high Sn content tend to form brittle intermetallic compounds by the reaction of Sn and Ni. Therefore, the growth of the intermetallic compound tends to make the shape uneven at the interface, which tends to adversely affect the mechanical properties.

  In the present invention, the tendency of the soldering metal layer 13 is greatly suppressed by forming Ni—Co alloy and further alloying with Cr, Mo, W, and Ta.

  Therefore, Ni—Co, for example, Cr constituting the base metal layer 12, and Ni—Co—Cr—W alloy obtained by alloying W, for example, are used as the soldering metal layer 13.

  As a result, it is possible to form the external electrode 4 that suppresses problems such as problems due to the generation of intermetallic compounds, problems due to film stress, diffusion of the base metal, and erosion due to Sn of the soldering electrodes.

  Also, a protective metal layer 14 on the solder metal layer 13 is formed to prevent oxidation and ensure wetting with the solder.

  The protective metal layer 14 is made of Au, Ag, or Sn, which is easily dissolved in Sn and difficult to oxidize, and particularly stable Au is preferable.

  In the case of Au, the thickness of the protective metal layer 14 is preferably 0.01 μm or more and 0.5 μm or less.

  In the case of Au, if it becomes thinner than 0.01 μm, the protective effect is insufficient, and the solderability is greatly reduced. On the other hand, when the thickness is 0.5 μm or more, it causes a void that increases the viscosity at the time of melting the solder.

  When the protective metal layer 14 is Sn, electroless plating or the like can be used. The thickness is preferably 0.1 μm or more and 2.0 μm or less. In the case of Sn, voids do not occur even when the thickness is increased. However, in the case of 2.0 μm or more, the film stress becomes large.

  A method for manufacturing the external electrode 4 will be described below.

  First, a step of forming the base metal layer 12 on the surface of the substrate 1 opposite to the surface on which the internal electrodes are formed is performed. The base metal layer 12 is formed by sputtering.

  Next, the process of forming the soldering metal layer 13 on the base metal layer 12 is performed. The soldering metal layer 13 is formed by sputtering.

  Next, the process of forming the protective metal layer 14 on the soldering metal layer 13 is performed.

  The protective metal layer 14 can be formed by sputtering.

  Sputtering also has the advantage that a metal layer can be formed even on a non-conductive material such as glass, and there is no use of a solution such as plating, and there is no reaction with glass.

  Sputtering has better adhesion than vapor deposition and the like, and it is relatively easy to control the composition of metal alloys having different melting points.

  The pattern formation by sputtering includes a photolithography method and a mask method, but the mask method is simple when strict accuracy is not particularly required.

  The protective metal layer 14 may be formed by electroless plating instead of sputtering, but sputtering is preferred.

  In the crystal resonator, Cr and Au formed by sputtering are used as the excitation electrode on which the crystal vibrating piece is formed. Therefore, it is convenient in terms of process to use Cr and Au as the external electrodes. In addition, the manufacturing method demonstrated is an example and is not limited to this.

  The electronic component of the present invention prepared by the above method was particularly superior in drop impact resistance to the external electrode having a Cr—Ni—Au structure.

  FIG. 4 is a cross-sectional view of an electronic component according to the third embodiment of the present invention. In addition, description is abbreviate | omitted about the structure similar to 1st embodiment.

  Unlike the first embodiment, this embodiment is different from the first embodiment in that an electronic element 17 such as an optical sensor is connected to the internal electrode 6 on the substrate 1 by wire bonding 18, and the electronic element 17 is sealed instead of a lid. However, it is different in that it is sealed with a sealing agent 19 such as glass.

  In this case, a surface mount package form in which a side wall is formed on a substrate and a resin or glass is filled, or a surface mount electronic component in a package form in which a chip-like electronic element is mounted on a substrate and resin-encapsulated or resin-coated is used. The present invention is also applicable.

  In the above description, the crystal resonator on which a crystal resonator element is mounted is described as an example of the electronic component 100. However, a semiconductor such as a SAW filter, a light receiving / light emitting device, an IC chip, an acceleration sensor, a pressure sensor, other MEMS sensors, or an optical component. Of course, the present invention can also be applied to an electronic component or a composite component having a surface mount package in which an electronic element composed of a plurality of chips and elements such as a high-frequency component and a multi-chip module is sealed. It is. In this case, the hermetic sealing is not necessarily a vacuum, and may be a sealing for completely blocking moisture.

  In this case, this is also applicable to surface-mount electronic components in the form of a surface-mount package in which a side wall is formed on a substrate and filled with resin or glass, or in the form of a package in which a chip-like electronic element is mounted on a base and sealed with resin or coated with resin. The invention is applicable.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lid 3 Bonding material 4 External electrode 5 Through electrode 6 Internal electrode 7 Connection part 8 Electronic element 9 Solder 10 Land 11 Circuit board 12 Base metal layer 13 Solder metal layer 14 Protective metal layer 15 Metal rod 16 Glass frit 17 Electronic element 18 Wire bonding 19 Sealant 100 Electronic component

Claims (6)

In an electronic component comprising a substrate formed of a brittle material, a package having the substrate, an electronic element installed in the package, and an external electrode formed on the substrate,
The external electrode includes a base metal layer formed on the substrate, a solder metal layer formed on the base metal layer, and a protective metal layer formed on the solder metal layer,
The soldering metal layer is formed of an alloy of Ni and Co, and the amount of Co added is in the range of 0.01 wt% to 5 wt%,
The base metal layer is formed of Cr, Ti, or an alloy of Cr and Ti,
The soldering metal layer is an alloy further including a metal constituting the base metal layer, and the content of the metal is in the range of 5% by weight to 40% by weight.   The electronic component according to claim 1, wherein the soldering metal layer is an alloy further including at least one metal selected from Mo, W, and Ta.   3. The soldering metal layer, wherein a total addition amount of at least one kind of metal constituting the base metal layer and Mo, W, or Ta is 50% or less. Electronic components described in   4. The electronic component according to claim 2, wherein a thickness of the soldering metal layer is in a range of 0.1 μm to 0.6 μm.   The electronic component according to any one of claims 1 to 4, wherein the substrate is soda glass.   The electronic component according to claim 1, wherein the electronic element is a crystal vibrating piece.

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