WO2013005555A1 - Metal-bonded structure and method for manufacturing same - Google Patents

Metal-bonded structure and method for manufacturing same Download PDF

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Publication number
WO2013005555A1
WO2013005555A1 PCT/JP2012/065324 JP2012065324W WO2013005555A1 WO 2013005555 A1 WO2013005555 A1 WO 2013005555A1 JP 2012065324 W JP2012065324 W JP 2012065324W WO 2013005555 A1 WO2013005555 A1 WO 2013005555A1
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WIPO (PCT)
Prior art keywords
copper
nickel
bonding
interface
joining
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PCT/JP2012/065324
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French (fr)
Japanese (ja)
Inventor
藤原　伸一
吉田　勇
山下　志郎
拓人 山口
小山　洋
英次 坂本
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株式会社日立製作所
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Publication of WO2013005555A1 publication Critical patent/WO2013005555A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/10—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating making use of vibrations, e.g. ultrasonic welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/22—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded
    • B23K20/233—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
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    • B23K2103/12—Copper or alloys thereof
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    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a bonded structure of copper and nickel and an ultrasonic bonding method.
  • Copper is a ductile material with excellent thermal and electrical conductivity, and is widely used for wiring materials.
  • nickel is harder than copper and has excellent oxidation resistance, and can maintain oxidation resistance up to about 500 ° C. even in air. Therefore, it is widely used for corrosion-resistant plating.
  • Wiring of printed circuit boards is known as a composite of copper and nickel, and nickel is formed on the copper wiring by a plating process, and a structure that suppresses surface oxidation with a thin gold layer to ensure solder wettability It has become.
  • the melting point of copper is 1085 ° C. and the melting point of nickel is 1455 ° C., so it is necessary to heat to at least 1085 ° C. or higher.
  • the coefficient of linear expansion of copper is 17.0 ppm / ° C and the coefficient of linear expansion of nickel is 13.3 ppm / ° C, so there is a concern that cracks may occur in the joint during the cooling process.
  • ultrasonic bonding for solid-phase metal bonding is promising.
  • the metal surfaces are rubbed together by applying ultrasonic waves in a state where the metals in contact with each other are pressurized, and the contaminated layer such as an oxide film on each metal surface is mechanically removed, and the new metal surface is removed.
  • This ultrasonic bonding is applied to gold wires and gold or aluminum pads for semiconductor devices, aluminum wires and aluminum or copper pads for power devices, copper wire harnesses for automobiles, etc. Limited to aluminum and copper. This is because, in ultrasonic bonding, the hardness difference between the bonding metals and the surface contamination layer greatly affect the bonding reliability, so that it is difficult to sufficiently bond the metals having different hardness differences.
  • Patent Document 1 a 3 micron thick copper plated member is formed on a 25 micron thick amorphous alloy thin body and a 3 micron nickel plated member is applied to a 500 micron thick copper plate.
  • An example in which members are ultrasonically bonded is given.
  • Patent Document 2 is an invention in which a bonding interface thin film is formed and ultrasonic bonding is performed in bonding a semiconductor element and a copper lead frame, and nickel is cited as an example of the bonding interface thin film.
  • Patent Document 1 and Patent Document 2 are examples of ultrasonic bonding of thin-film nickel and copper of several microns, and detailed bonding conditions and bonding methods. Is not listed.
  • the bondability is greatly influenced by the hardness of the base material on which the thin film nickel is formed, it is difficult to perform the bonding stably, and the load and ultrasonic wave
  • the bonding power such as the amplitude is increased, the thin film nickel is broken, and there is a possibility that the base material and copper are joined.
  • FIG. 12 is a cross-sectional observation result of a bonded portion when 1 mm thick copper was ultrasonically bonded onto a 1 mm thick copper plate plated with 5 ⁇ m nickel.
  • the initial load was 110 N
  • the maximum load was 230 N
  • the bonding time was 0.7 seconds
  • the ultrasonic tool amplitude was 22 microns
  • the ultrasonic frequency was 30 kHz.
  • FIG. 12 when attempting to join copper to the thin film nickel formed on the copper base material, it can be confirmed that the thin film nickel breaks and that a portion where the copper base material and copper are directly joined is generated. .
  • the present invention is characterized in that, in the joining between nickel and copper, the particle size in the vicinity of the joining interface between nickel and copper is refined and ultrasonic joining is performed.
  • the bonded body is excellent in electric conduction and heat conduction, and since the bonding temperature is low and the bonding temperature is low, the stress generated at the interface after bonding is reduced.
  • the bonding temperature is low and the bonding temperature is low, the stress generated at the interface after bonding is reduced.
  • no compound is formed at the interface, and since no compound is formed, there is an effect that a decrease in reliability is unlikely to occur under a heat load condition after joining.
  • FIG. 1 is a perspective view before and after ultrasonic bonding of a nickel plate and a copper plate in a bonding experiment of the present invention.
  • 1 is nickel
  • 2 is copper
  • 3 is an ultrasonic tool indentation
  • 10 is an ultrasonic tool
  • 11 is an ultrasonic tool tip protrusion.
  • the nickel 1 may be nickel or a nickel alloy containing nickel as a main component.
  • the copper 2 may be copper or a copper alloy containing copper as a main component.
  • nickel 1 and copper 2 are drawn in a plate shape, but the shape of the member is not defined as long as the non-joint surfaces such as a disk shape, a column shape, and a cube are copper and nickel, respectively.
  • the nickel 1 may be a composite of two or more layers in which nickel is formed on a metal such as copper, aluminum or iron, or an inorganic material such as ceramic or glass, as long as nickel is present on the bonding surface.
  • the copper 2 may be a composite of two or more layers in which copper is formed on a metal such as aluminum, iron, zinc, silver, gold, or an inorganic material such as ceramic, as long as copper is present on the bonding surface.
  • nickel 1 was nickel with a purity of 99.9%
  • copper 2 was C1020R pure copper with a hardness of 1 / 2H
  • both nickel 1 and copper 2 were 10 mm wide, 25 mm deep, and 0.5 mm thick.
  • a piece was used.
  • the surface roughness Ry of nickel 1 and copper 2 was 0.5 microns or less.
  • the bonded surface of the test piece was cleaned with isopropyl alcohol, and then ultrasonic bonding was performed with the ultrasonic tool 10 having a protrusion at the tip of the ultrasonic tool.
  • the ultrasonic tool 10 has a pressing area of 2 mm ⁇ 2 mm. After the ultrasonic bonding, a bonded body having the ultrasonic tool indentation 3 on the copper 2 is completed.
  • nickel 1 is shown below and copper 2 is shown on the ultrasonic tool 10 side, but vibration may be applied from the nickel 1 side.
  • FIG. 2 is a schematic cross-sectional view of a bonded portion after ultrasonic bonding in the bonding experiment of the present invention.
  • 1 is nickel
  • 2 is copper
  • 3 is an ultrasonic tool indentation
  • 4 is a copper / nickel joint.
  • FIG. 2 is a schematic cross-sectional view of the joint portion including the ultrasonic tool indent 3 of FIG.
  • the materials for nickel 1 and copper 2 are the same as those described with reference to FIG.
  • an ultrasonic tool impression 3 is formed on the copper 2
  • a copper / nickel joint 4 is formed at the interface between the nickel 1 and the copper 2 immediately below the ultrasonic tool impression 3, and the nickel 1 and the copper 2.
  • Copper and nickel are a combination that does not form a compound called a total solid solution. Therefore, even when a thermal load is applied in an actual use environment or the like, a compound that tends to decrease reliability is not formed. Therefore, when reliability is ensured by initial bonding, long-term reliability is easily ensured.
  • FIG. 3 shows the experimental conditions and tensile strength based on the L9 orthogonal table used in the joining experiment of the present invention.
  • initial load 10,30,50N (2.5MPa, 7.5MPa, 12.5MPa), maximum load 70,100,120N (17.5MPa, 25MPa, 30MPa), welding time 0.3,0.5,0.8 seconds, ultrasonic tool amplitude 10.7
  • the bonding strength was evaluated by a tensile test under each condition at 16.2, 21.5 microns.
  • the initial load is a load for starting application of ultrasonic waves, and the ultrasonic frequency is 30 kHz. As shown in Fig. 3, it is confirmed that the joint can be joined with a tensile strength of 70 N even under the No.
  • FIG. 4 is an observation result of the joint interface between nickel and copper after joining in the joining experiment of the present invention.
  • the test piece of FIG. 4 was bonded under the conditions of an initial load of 30 N, a maximum load of 120 N, a bonding time of 0.8 seconds, and an ultrasonic tool amplitude of 21.5 microns.
  • the interface between copper and nickel is bonded almost without voids, and no compound layer is seen at the bonded interface.
  • FIG. 5 is an electron backscatter diffraction image of the copper base material before bonding. From FIG. 5, it can be seen that the grain size of copper before bonding is approximately 12 microns.
  • FIG. 6 is an electron backscatter diffraction image of the nickel base material before bonding. It can be seen from FIG. 6 that the particle size of nickel before joining is approximately 18 microns.
  • FIG. 7 is an electron backscatter diffraction image of the bonded interface between copper and nickel after bonding.
  • FIG. 7 shows that the copper in the vicinity of the copper-nickel interface has a crystal grain size of 2.9 microns, which is 24% smaller than the base material grain size of 12 microns.
  • the particle size of copper which is about 50 microns away from the bonding interface, is 14 microns and can be regarded as equivalent to the base material particle size.
  • the nickel particle size in the vicinity of the copper-nickel interface is 12 microns, showing that the initial nickel particle size is reduced from 18 microns to 67%.
  • this joint is a joint with excellent electrical and thermal conductivity because copper and nickel can be directly metal-bonded without using solder or conductive resin. It is a solid-phase bonding only in ascending, and the bonding temperature is lower than the bonding method in which the metal is melted and bonded, so the stress generated at the interface after bonding is reduced, and in the joining of all-solid-solution copper and nickel For this reason, no compound is formed at the interface, and no compound is formed at the bonding interface, so that a decrease in reliability is unlikely to occur in a use environment after bonding.
  • FIG. 8 is a graph showing changes in tensile strength after a 200 ° C. holding heat treatment and a -40 / 125 ° C. temperature cycle test in the joining experiment of the present invention.
  • FIG. 8 shows the tensile strength measured by heat-treating a test piece bonded under the conditions of an initial load of 30 N, a maximum load of 120 N, a bonding time of 0.8 seconds, and an ultrasonic tool amplitude of 21.5 microns. As shown in FIG.
  • FIG. 9 is an example when an ultrasonic bonded body of copper and nickel is applied to a power module
  • FIG. 10 is a cross-sectional view of the power module AA in FIG. 21 is a base with cooling fins
  • 22 is an insulating substrate
  • 23 is wiring on the substrate
  • 24 is a semiconductor element
  • 25 is a lead for external connection
  • 26 is solder.
  • the on-substrate wiring 23 and the semiconductor element 24 are electrically connected by a metal wire.
  • the on-substrate wiring 23 has a structure in which the outermost surface is mainly nickel or nickel.
  • gold, silver, tin, or tin-based solder having a thickness of 1 micron or less may be formed on the outermost surface of the on-substrate wiring 23.
  • the external connection lead 25 is configured such that the surface on the substrate wiring 23 side is mainly composed of copper or copper.
  • the on-substrate wiring 23 and the external connection lead 25 are ultrasonically connected.
  • gold, silver, tin, or tin-based solder is formed on the surface of the wiring 23 on the substrate, the gold, silver, tin, or tin-based solder is broken by ultrasonic bonding to bond copper and nickel. .
  • the substrate wiring 23 and the semiconductor element 24 are often joined with solder. Therefore, considering the wettability of solder and the suppression of the growth of the interface compound after bonding, the surface layer of the on-substrate wiring 23 may have a structure in which gold of 1 micron or less is formed on nickel.
  • the lead for external connection 25 allows a large current to flow, copper is mainly used as the base material. Therefore, the connection between the lead for external connection 25 and the wiring 23 on the substrate is made of copper and nickel (gold having a thickness of 1 micron or less). In some cases, the bonding can be performed by applying the ultrasonic bonding of the present invention.
  • the semiconductor element 24 and the external connection lead 25 can be bonded to the on-substrate wiring 23 without adding a new process.
  • the advantage of applying this bonding is that copper and nickel can be directly metal-bonded without using solder or conductive resin, so that lead / substrate wiring bonding with excellent electrical and thermal conductivity is possible.
  • the part is a solid-phase bonding with only a temperature rise due to frictional heat at the bonding interface, and the bonding temperature is lower than the bonding method in which the metal is melted and bonded, so the stress generated at the interface after bonding is small, and it is against the substrate
  • the heat load is also small, and since the solid solution is a joint of solid solution copper and nickel, no compound is formed at the interface, and the reliability is unlikely to deteriorate in the use environment after joining.
  • FIG. 11 is a cross-sectional view of a copper bump and nickel layer joint, which is a second application example of the present invention.
  • 30 is a semiconductor element
  • 31 is a semiconductor electrode
  • 32 is a copper bump
  • 40 is a substrate
  • 41 is a wiring on the substrate
  • 42 is a nickel layer
  • 50 is an underfill.
  • the copper bump 32 has a configuration in which the outermost surface of the copper bump 32 on the nickel layer 42 side is mainly composed of copper or copper
  • the bump itself may be formed of a composite.
  • the nickel layer 42 is configured such that the outermost surface of the nickel layer 42 on the copper bump 32 side is mainly composed of nickel or nickel.
  • the substrate 40 may be a resin substrate, a ceramic substrate, a silicon substrate, or the like.
  • the on-substrate wiring 41 is a configuration generally used in each substrate.
  • the on-substrate wiring 41 may be copper.
  • a bonding structure in which the copper bump 32 is ultrasonically connected to the on-substrate wiring 42 is formed, and can be widely applied to flip chip bonding and the like. After ultrasonic bonding of the copper bump 32 and the nickel layer 42, the outer periphery is sealed with an underfill 50 to complete this structure.
  • the advantage of applying this bonding is that copper and nickel can be directly metal-bonded without using solder or conductive resin, making it possible to perform bump bonding with excellent electrical and thermal conductivity.
  • This is solid-phase bonding that only raises the temperature due to frictional heat, and the bonding temperature is lower than the bonding method in which solder is melted and bonded, so the stress generated at the interface after bonding is small, and the thermal load on the substrate It is also possible to suppress warping of the substrate and package, and because it is a solid-solid copper-nickel joint, no compound is formed at the interface, and reliability is unlikely to occur in the use environment after joining, and it is a hard bump Therefore, a gap between the semiconductor element and the substrate can be secured.
  • the bonding between the semiconductor element 30 and the substrate 40 has been described as an example, but the present invention can be similarly applied to the bonding between the package and the substrate.

Abstract

In the present invention, ultrasonic bonding between a nickel member and a copper member is performed under the conditions where the diameter of crystal grains close to the copper-nickel interface between the copper member and the nickel member is reduced.

Description

金属接合構造とその製造方法Metal junction structure and manufacturing method thereof
　本発明は銅とニッケルの接合構造体および超音波接合方法に関する。 The present invention relates to a bonded structure of copper and nickel and an ultrasonic bonding method.
　銅は熱伝導性や電気伝導性に優れた延性材料であり、配線材料をはじめとして広く使用されている。一方、ニッケルは銅より硬く耐酸化性に優れる特長を有しており、空気中でも500℃程度までは耐酸化性を維持できる。そのため、耐食性めっきなどに広く使われている。銅とニッケルの複合体としてはプリント基板の配線が知られており、銅配線上にニッケルをめっきプロセスにて形成し、はんだぬれ性を確保するための金薄層を有する表面酸化を抑制した構成となっている。 Copper is a ductile material with excellent thermal and electrical conductivity, and is widely used for wiring materials. On the other hand, nickel is harder than copper and has excellent oxidation resistance, and can maintain oxidation resistance up to about 500 ° C. even in air. Therefore, it is widely used for corrosion-resistant plating. Wiring of printed circuit boards is known as a composite of copper and nickel, and nickel is formed on the copper wiring by a plating process, and a structure that suppresses surface oxidation with a thin gold layer to ensure solder wettability It has become.
　上述のめっきプロセスで銅とニッケルの複合体を形成する場合、銅配線上に数十ミクロン厚以上のニッケルを形成するためには長時間めっきを行う必要があり、また形成できる厚みにも限界があり、厚みが厚くなるにつれてニッケルの膜質もばらついてくる。そのため、100ミクロンを超えるような厚みの銅とニッケルの複合体をめっきプロセスで形成するのは非常に困難である。 When forming a composite of copper and nickel by the above-described plating process, it is necessary to perform plating for a long time in order to form nickel of several tens of microns or more on the copper wiring, and there is a limit to the thickness that can be formed. Yes, the film quality of nickel varies as the thickness increases. Therefore, it is very difficult to form a composite of copper and nickel having a thickness exceeding 100 microns by a plating process.
　また、いずれか一方の金属を溶融させて接合を試みる場合、銅の融点が1085℃、ニッケルの融点が1455℃であるため、少なくとも1085℃以上に加熱する必要がある。仮に接合できた場合でも、銅の線膨張係数は17.0ppm/℃、ニッケルの線膨張係数は13.3ppm/℃と差があるため、冷却過程で接合部に亀裂が発生することが懸念される。 Also, when attempting to join by melting one of the metals, the melting point of copper is 1085 ° C. and the melting point of nickel is 1455 ° C., so it is necessary to heat to at least 1085 ° C. or higher. Even if it can be joined, the coefficient of linear expansion of copper is 17.0 ppm / ° C and the coefficient of linear expansion of nickel is 13.3 ppm / ° C, so there is a concern that cracks may occur in the joint during the cooling process.
　これらの課題を解決する接合方法として、金属同士を固相接合する超音波接合が有力である。超音波接合は接触させた金属同士を加圧した状態で超音波を印加することにより金属表面を擦り合わせ、各々の金属表面の酸化膜等の汚染層を機械的に除去し、金属の新生面を露出・接触させることで接合するといわれている金属接合方法である。この超音波接合は、半導体デバイスの金ワイヤと金もしくはアルミニウムのパッド、パワーデバイスのアルミニウムワイヤとアルミニウムもしくは銅パッド、自動車等の銅製ワイヤハーネスの接合などに適用されているが、接合対象は金、アルミニウム、銅などに限られている。これは、超音波接合では接合金属間の硬度差や表面汚染層が接合信頼性に大きく影響することため、硬度差の異なる金属では十分な接合が難しいという背景がある。 As a bonding method for solving these problems, ultrasonic bonding for solid-phase metal bonding is promising. In ultrasonic bonding, the metal surfaces are rubbed together by applying ultrasonic waves in a state where the metals in contact with each other are pressurized, and the contaminated layer such as an oxide film on each metal surface is mechanically removed, and the new metal surface is removed. It is a metal joining method that is said to be joined by exposure and contact. This ultrasonic bonding is applied to gold wires and gold or aluminum pads for semiconductor devices, aluminum wires and aluminum or copper pads for power devices, copper wire harnesses for automobiles, etc. Limited to aluminum and copper. This is because, in ultrasonic bonding, the hardness difference between the bonding metals and the surface contamination layer greatly affect the bonding reliability, so that it is difficult to sufficiently bond the metals having different hardness differences.
　銅とニッケルの超音波接合に関して、特許文献１では厚さ25ミクロンの非晶質合金薄体上に3ミクロン厚の銅めっきをした部材と、500ミクロン厚の銅板に3ミクロンのニッケルめっきをした部材を超音波接合した例が挙げられている。特許文献２では半導体素子と銅リードフレームの接合において接合界面薄膜を形成し超音波接合する発明であり、接合界面薄膜の一例としてニッケルが挙げられている。 Regarding ultrasonic bonding of copper and nickel, in Patent Document 1, a 3 micron thick copper plated member is formed on a 25 micron thick amorphous alloy thin body and a 3 micron nickel plated member is applied to a 500 micron thick copper plate. An example in which members are ultrasonically bonded is given. Patent Document 2 is an invention in which a bonding interface thin film is formed and ultrasonic bonding is performed in bonding a semiconductor element and a copper lead frame, and nickel is cited as an example of the bonding interface thin film.
特開昭62-167040号公報JP 62-167040 A 特開2009-38139号公報JP 2009-38139 JP
　上記の通り、銅とニッケルの超音波接合については記載されているが、特許文献１および特許文献２ともに数ミクロンの薄膜ニッケルと銅の超音波接合例であり、また詳細な接合条件や接合方法は記載されていない。薄膜ニッケルの超音波接合の場合は、薄膜ニッケルが形成されている母材の硬さに接合性が大きく左右されるため、接合を安定して実施することが困難であり、また荷重や超音波振幅などの接合パワーを大きくすると薄膜ニッケルが破断し、母材と銅の接合体となる可能性がある。母材と銅の接合体となった場合は実使用環境下で化合物が成長するなどの界面形態の変化が生じ、信頼性低下の可能性がある。また、バルク材のニッケルと銅の接合の場合は、バルクのニッケルの硬度が支配的となるため、母材硬度に依存する薄膜ニッケルと銅の接合とは異なる接合条件となる。 As described above, although ultrasonic bonding of copper and nickel is described, both Patent Document 1 and Patent Document 2 are examples of ultrasonic bonding of thin-film nickel and copper of several microns, and detailed bonding conditions and bonding methods. Is not listed. In the case of ultrasonic bonding of thin film nickel, since the bondability is greatly influenced by the hardness of the base material on which the thin film nickel is formed, it is difficult to perform the bonding stably, and the load and ultrasonic wave When the bonding power such as the amplitude is increased, the thin film nickel is broken, and there is a possibility that the base material and copper are joined. When it becomes a joined body of a base material and copper, the change of the interface form such as the growth of the compound occurs under the actual use environment, and there is a possibility that the reliability is lowered. Further, in the case of joining nickel and copper as bulk materials, since the hardness of bulk nickel is dominant, the joining conditions differ from joining of thin film nickel and copper depending on the base material hardness.
　図１２は5ミクロンのニッケルめっきを施した１mm厚の銅板上に1mm厚の銅を超音波接合した際の接合部断面観察結果である。本接合実験では初期荷重110N、最高荷重230N、接合時間0.7秒、超音波ツール振幅22ミクロン、超音波周波数は30kHzで行った。図１２に示すように銅母材上に形成した薄膜ニッケルへ銅の接合を試みた場合、薄膜ニッケルの破断が発生し、銅母材と銅が直接接合される箇所が発生することが確認できる。 FIG. 12 is a cross-sectional observation result of a bonded portion when 1 mm thick copper was ultrasonically bonded onto a 1 mm thick copper plate plated with 5 μm nickel. In this bonding experiment, the initial load was 110 N, the maximum load was 230 N, the bonding time was 0.7 seconds, the ultrasonic tool amplitude was 22 microns, and the ultrasonic frequency was 30 kHz. As shown in FIG. 12, when attempting to join copper to the thin film nickel formed on the copper base material, it can be confirmed that the thin film nickel breaks and that a portion where the copper base material and copper are directly joined is generated. .
　本発明は、ニッケルまと銅との接合において、ニッケルと銅との接合界面近傍の粒径を微細化させ、超音波接合したことを特徴とする。 The present invention is characterized in that, in the joining between nickel and copper, the particle size in the vicinity of the joining interface between nickel and copper is refined and ultrasonic joining is performed.
　本発明によれば、銅とニッケルを直接接合できるため電気伝導や熱伝導に優れた接合体であること、固相接合であり接合温度が低いため接合後の界面に発生する応力が小さくなること、全率固溶系の銅とニッケルの接合であるため界面に化合物が形成されないこと、化合物が形成されないため接合後の熱負荷条件下で信頼性低下が発生しにくいという効果を奏する。 According to the present invention, since copper and nickel can be directly bonded, the bonded body is excellent in electric conduction and heat conduction, and since the bonding temperature is low and the bonding temperature is low, the stress generated at the interface after bonding is reduced. In addition, since it is a joint of all-solid-solution copper and nickel, no compound is formed at the interface, and since no compound is formed, there is an effect that a decrease in reliability is unlikely to occur under a heat load condition after joining.
本発明の接合実験におけるニッケル板と銅板の超音波接合前後の斜視図である。It is a perspective view before and behind ultrasonic joining of a nickel plate and a copper plate in the joining experiment of the present invention. 本発明の接合実験における超音波接合後の接合部断面模式図である。It is a junction cross-sectional schematic diagram after ultrasonic bonding in the bonding experiment of the present invention. 本発明の接合実験で用いたL9直交表に基づく実験条件と引張り強さである。It is an experimental condition and tensile strength based on the L9 orthogonal table used in the joining experiment of the present invention. 本発明の接合実験における接合後のニッケルと銅の接合界面の観察結果である。It is an observation result of the joint interface of nickel and copper after joining in the joining experiment of the present invention. 本発明の接合実験における接合前の銅母材の電子後方散乱回折像である。It is an electron backscattering diffraction image of the copper base material before joining in the joining experiment of this invention. 本発明の接合実験における接合前のニッケル母材の電子後方散乱回折像である。It is an electron backscattering diffraction image of the nickel base material before joining in the joining experiment of this invention. 本発明の接合実験における接合後の銅とニッケル接合部近傍の電子後方散乱回折像である。It is an electron backscattering diffraction image of the copper-nickel joint vicinity after joining in the joining experiment of this invention. 本発明の接合実験における200℃保持熱処理と-40/125℃温度サイクル試験後の引張り強度の変化グラフである。It is a change graph of the tensile strength after a 200 degreeC holding heat treatment and a -40/125 degreeC temperature cycle test in the joining experiment of this invention. 本発明の第一の適用例であるパワーモジュールの外観図である。It is an external view of the power module which is the 1st application example of this invention. 本発明の第一の適用例であるパワーモジュールの断面図（図９中A断面）である。It is sectional drawing (A cross section in FIG. 9) of the power module which is the 1st application example of this invention. 本発明の第二の適用例である銅バンプとニッケル層接合部の断面図である。It is sectional drawing of the copper bump and nickel layer junction which is the 2nd application example of this invention. ニッケルめっき付銅板と銅を超音波接合した場合の接合部断面観察結果である。It is a junction cross-section observation result at the time of ultrasonically bonding a copper plate with nickel plating and copper.
　以下、本発明実施の形態を説明する。 Hereinafter, embodiments of the present invention will be described.
　図１は本発明の接合実験におけるニッケル板と銅板の超音波接合前後の斜視図である。１はニッケル、２は銅、３は超音波ツール圧痕、１０は超音波ツール、１１は超音波ツール先端突起である。ニッケル１はニッケルもしくはニッケルを主成分とするニッケル合金であればよい。銅２は銅もしくは銅を主成分とする銅合金であればよい。図１において、ニッケル１および銅２は板状に描画したが、円盤状や柱状、立方体など、非接合体面がそれぞれ銅とニッケルであれば部材お形状は規定しない。すなわち、ニッケル１は接合面にニッケルが存在すれば、銅やアルミニウム、鉄などの金属や、セラミックやガラスなどの無機物上にニッケルが形成された2層以上の複合体でもよい。同様に銅２は接合面に銅が存在すれば、アルミニウムや鉄、亜鉛、銀、金などの金属やセラミックなどの無機物上に銅が形成された2層以上の複合体でもよい。 FIG. 1 is a perspective view before and after ultrasonic bonding of a nickel plate and a copper plate in a bonding experiment of the present invention. 1 is nickel, 2 is copper, 3 is an ultrasonic tool indentation, 10 is an ultrasonic tool, and 11 is an ultrasonic tool tip protrusion. The nickel 1 may be nickel or a nickel alloy containing nickel as a main component. The copper 2 may be copper or a copper alloy containing copper as a main component. In FIG. 1, nickel 1 and copper 2 are drawn in a plate shape, but the shape of the member is not defined as long as the non-joint surfaces such as a disk shape, a column shape, and a cube are copper and nickel, respectively. That is, the nickel 1 may be a composite of two or more layers in which nickel is formed on a metal such as copper, aluminum or iron, or an inorganic material such as ceramic or glass, as long as nickel is present on the bonding surface. Similarly, the copper 2 may be a composite of two or more layers in which copper is formed on a metal such as aluminum, iron, zinc, silver, gold, or an inorganic material such as ceramic, as long as copper is present on the bonding surface.
　今回の実験では、ニッケル１は純度９９．９％のニッケルを、銅２はC1020R　硬度1/2Hの純銅を用い、ニッケル１および銅２ともに幅10mm×奥行25mm×厚さ0.5mmの板状試験片を用いた。ニッケル１および銅２の表面粗さRyは0.5ミクロン以下であった。試験片の接合面をイソプロピルアルコールで洗浄後、超音波ツール先端に突起を有する超音波ツール１０にて、超音波接合を行った。超音波ツール１０は加圧面積2mm×2mmである。超音波接合後は超音波ツール圧痕３を銅２上に有する接合体が完成する。図１においては、ニッケル１を下に、銅２を超音波ツール１０側に図示したが、ニッケル１側から加振してもかまわない。 In this experiment, nickel 1 was nickel with a purity of 99.9%, copper 2 was C1020R pure copper with a hardness of 1 / 2H, and both nickel 1 and copper 2 were 10 mm wide, 25 mm deep, and 0.5 mm thick. A piece was used. The surface roughness Ry of nickel 1 and copper 2 was 0.5 microns or less. The bonded surface of the test piece was cleaned with isopropyl alcohol, and then ultrasonic bonding was performed with the ultrasonic tool 10 having a protrusion at the tip of the ultrasonic tool. The ultrasonic tool 10 has a pressing area of 2 mm × 2 mm. After the ultrasonic bonding, a bonded body having the ultrasonic tool indentation 3 on the copper 2 is completed. In FIG. 1, nickel 1 is shown below and copper 2 is shown on the ultrasonic tool 10 side, but vibration may be applied from the nickel 1 side.
　図２は本発明の接合実験における超音波接合後の接合部断面模式図である。１はニッケル、２は銅、３は超音波ツール圧痕、４は銅/ニッケル接合部である。図２は図１の超音波ツール圧痕３を含むような接合部断面模式図である。ニッケル１および銅２の材質については図１の説明と同様であるため省略する。図２に示すように、銅２上に超音波ツール圧痕３が形成され、超音波ツール圧痕３直下のニッケル１と銅２の界面で銅/ニッケル接合部４が形成されてニッケル１と銅２は金属接合される。銅とニッケルは全率固溶体と呼ばれる化合物を形成しない組み合わせである。そのため、実使用環境等で熱負荷がかかった場合でも信頼性を低下させる要因になりやすい化合物が形成されないため初期接合で信頼性が確保された場合、長期信頼性を確保しやすい。 FIG. 2 is a schematic cross-sectional view of a bonded portion after ultrasonic bonding in the bonding experiment of the present invention. 1 is nickel, 2 is copper, 3 is an ultrasonic tool indentation, and 4 is a copper / nickel joint. FIG. 2 is a schematic cross-sectional view of the joint portion including the ultrasonic tool indent 3 of FIG. The materials for nickel 1 and copper 2 are the same as those described with reference to FIG. As shown in FIG. 2, an ultrasonic tool impression 3 is formed on the copper 2, and a copper / nickel joint 4 is formed at the interface between the nickel 1 and the copper 2 immediately below the ultrasonic tool impression 3, and the nickel 1 and the copper 2. Are metal bonded. Copper and nickel are a combination that does not form a compound called a total solid solution. Therefore, even when a thermal load is applied in an actual use environment or the like, a compound that tends to decrease reliability is not formed. Therefore, when reliability is ensured by initial bonding, long-term reliability is easily ensured.
　図３に本発明の接合実験で用いたL9直交表に基づく実験条件と引張り強さを示す。本接合実験では初期荷重10,30,50N（2.5MPa,7.5MPa,12.5MPa）、最高荷重70,100,120N（17.5MPa,25MPa,30MPa）、接合時間0.3,0.5,0.8秒、超音波ツール振幅10.7,16.2,21.5ミクロンとし、各条件で接合強さを引張試験で評価した。なお、初期荷重は超音波の印加を開始する荷重、超音波周波数は30kHzである。図３に示すように、最も接合条件の低いNo.1の条件（初期荷重10N、最高荷重70N、接合時間0.3秒、超音波ツール振幅10.7ミクロン）においても、引張り強さ70Nで接合できることが確認された。図３より、接合時に荷重を増加させ（初期荷重より最高荷重を大きくする）、超音波接合時の銅２の変形による接合面積の増加に合わせて荷重を増やすことにより、接合が可能となった。すなわち、初期荷重を2.5～12.5MPa,最高荷重を17.5～30MPa,また、接合時間を0.3～0.8秒、超音波ツール振幅を10.7～21.5ミクロンでは、銅とニッケルは超音波接合が可能である。 FIG. 3 shows the experimental conditions and tensile strength based on the L9 orthogonal table used in the joining experiment of the present invention. In this joining experiment, initial load 10,30,50N (2.5MPa, 7.5MPa, 12.5MPa), maximum load 70,100,120N (17.5MPa, 25MPa, 30MPa), welding time 0.3,0.5,0.8 seconds, ultrasonic tool amplitude 10.7, The bonding strength was evaluated by a tensile test under each condition at 16.2, 21.5 microns. The initial load is a load for starting application of ultrasonic waves, and the ultrasonic frequency is 30 kHz. As shown in Fig. 3, it is confirmed that the joint can be joined with a tensile strength of 70 N even under the No. 1 condition with the lowest joining conditions (initial load 10 N, maximum load 70 N, joining time 0.3 seconds, ultrasonic tool amplitude 10.7 microns). It was done. From FIG. 3, it was possible to join by increasing the load at the time of bonding (increasing the maximum load from the initial load) and increasing the load in accordance with the increase in the bonding area due to deformation of copper 2 during ultrasonic bonding. . That is, when the initial load is 2.5 to 12.5 MPa, the maximum load is 17.5 to 30 MPa, the bonding time is 0.3 to 0.8 seconds, and the ultrasonic tool amplitude is 10.7 to 21.5 microns, copper and nickel can be ultrasonically bonded.
　図４は本発明の接合実験における接合後のニッケルと銅の接合界面の観察結果である。図４の試験片は初期荷重30N、最高荷重120N、接合時間0.8秒、超音波ツール振幅21.5ミクロンの条件で接合を行った。図４に示すように、銅とニッケルの界面はほぼボイドなく接合されており、接合界面に化合物層もみられない。また、銅側の結晶粒がニッケル側に比べて微細化していることがわかる。 FIG. 4 is an observation result of the joint interface between nickel and copper after joining in the joining experiment of the present invention. The test piece of FIG. 4 was bonded under the conditions of an initial load of 30 N, a maximum load of 120 N, a bonding time of 0.8 seconds, and an ultrasonic tool amplitude of 21.5 microns. As shown in FIG. 4, the interface between copper and nickel is bonded almost without voids, and no compound layer is seen at the bonded interface. Moreover, it turns out that the crystal grain of the copper side is refined | miniaturized compared with the nickel side.
　図５は接合前の銅母材の電子後方散乱回折像である。図５より、接合前の銅の粒径はおよそ12ミクロンであることがわかる。図６は接合前のニッケル母材の電子後方散乱回折像である。図６より接合前のニッケルの粒径はおよそ18ミクロンであることがわかる。 FIG. 5 is an electron backscatter diffraction image of the copper base material before bonding. From FIG. 5, it can be seen that the grain size of copper before bonding is approximately 12 microns. FIG. 6 is an electron backscatter diffraction image of the nickel base material before bonding. It can be seen from FIG. 6 that the particle size of nickel before joining is approximately 18 microns.
　図７は接合後の銅とニッケルの接合界面の電子後方散乱回折像である。図７から銅とニッケルの接合界面近傍の銅は結晶粒径が2.9ミクロンと、母材粒径の12ミクロンと比較して24％に微細化していることがわかる。しかし、接合界面から50ミクロン程度はなれた銅の粒径は14ミクロンであり、母材粒径と同等とみなすことができる。一方、銅とニッケル界面近傍のニッケル粒径は12ミクロンであり、初期のニッケル粒径18ミクロンから67％と微細化していることがわかる。これらより、ニッケルと銅の超音波接合においては、荷重と超音波の印加により接合界面のニッケルおよび銅（特に銅）が微細化し、酸化膜等の表面汚染膜を除去することで接合が行われていると考えられる。この結晶粒微細化は銅とニッケル界面近傍で塑性流動が生じている可能性がある。 FIG. 7 is an electron backscatter diffraction image of the bonded interface between copper and nickel after bonding. FIG. 7 shows that the copper in the vicinity of the copper-nickel interface has a crystal grain size of 2.9 microns, which is 24% smaller than the base material grain size of 12 microns. However, the particle size of copper, which is about 50 microns away from the bonding interface, is 14 microns and can be regarded as equivalent to the base material particle size. On the other hand, the nickel particle size in the vicinity of the copper-nickel interface is 12 microns, showing that the initial nickel particle size is reduced from 18 microns to 67%. As a result, in ultrasonic bonding of nickel and copper, the application of load and ultrasonic waves refines nickel and copper (especially copper) at the bonding interface, and bonding is performed by removing surface contamination films such as oxide films. It is thought that. This grain refinement may cause plastic flow near the interface between copper and nickel.
　従来は、銅（モース硬度3）は柔らかいため、超音波を印加しても硬いニッケル（モース硬度4）の酸化膜等の表面汚染膜を破ることができず、銅とニッケルとは超音波接合に向いていないと考えられていた。しかし今回の実験では、界面近傍の銅が微粒子化することにより、塑性流動が起き、銅およびニッケルの表面汚染膜を破ることができたと考えられる。銅側では、表面の結晶粒径は、内部の結晶粒径の半分よりも小さくとなっているが、ニッケル側では、表面の表面の結晶粒径は、内部の結晶粒径の半分よりも大きい。 Conventionally, copper (Mohs hardness 3) is soft, so even if ultrasonic waves are applied, it is not possible to break surface contamination films such as hard nickel (Mohs hardness 4) oxide film, and copper and nickel are ultrasonically bonded. It was thought that it was not suitable for. However, in this experiment, it is thought that plastic flow occurred due to the fine particles of copper in the vicinity of the interface, and the surface contamination film of copper and nickel could be broken. On the copper side, the crystal grain size of the surface is smaller than half of the internal crystal grain size, but on the nickel side, the crystal grain size of the surface surface is larger than half of the internal crystal grain size. .
　このように、バルクの銅とニッケルは接合界面近傍の金属粒、特に銅を微細化させる荷重・保持時間・超音波振幅条件で接合すると接合が可能であることを本実験で明らかにした。よってニッケルが１～10ミクロン程度と薄い場合でも、接合界面近傍の金属粒、特に銅側を微細化できる接合条件であれば本実験と同様な接合が実現できる。 Thus, it was clarified in this experiment that bulk copper and nickel can be bonded if they are bonded under the conditions of load, holding time, and ultrasonic amplitude that make metal particles near the bonding interface, particularly copper finer. Therefore, even when nickel is as thin as about 1 to 10 microns, the same bonding as in this experiment can be realized if the bonding conditions are such that the metal grains near the bonding interface, particularly the copper side, can be made finer.
　本接合体の特長は、銅とニッケルをはんだや導電性樹脂などを用いずに直接金属接合できるため電気伝導や熱伝導に優れた接合体であること、接合部は接合界面の摩擦熱による温度上昇のみの固相接合であり、金属を溶融させて接合する接合方法に比べて接合温度が低いため接合後の界面に発生する応力が小さくなること、全率固溶系の銅とニッケルの接合であるため界面に化合物が形成されないこと、接合界面に化合物が形成されないため接合後の使用環境下で信頼性低下が発生しにくいことである。 The feature of this joint is that it is a joint with excellent electrical and thermal conductivity because copper and nickel can be directly metal-bonded without using solder or conductive resin. It is a solid-phase bonding only in ascending, and the bonding temperature is lower than the bonding method in which the metal is melted and bonded, so the stress generated at the interface after bonding is reduced, and in the joining of all-solid-solution copper and nickel For this reason, no compound is formed at the interface, and no compound is formed at the bonding interface, so that a decrease in reliability is unlikely to occur in a use environment after bonding.
　既述のように、使用環境下における信頼性低下は発生しにくいと考えられたため、200℃の高温放置および-40/125℃温度サイクル試験後の引張強度の評価を行った。図８は本発明の接合実験における200℃保持熱処理と-40/125℃温度サイクル試験後の引張り強度の変化グラフである。なお図８は初期荷重30N、最高荷重120N、接合時間0.8秒、超音波ツール振幅21.5ミクロンの条件で接合を行った試験片を熱処理し、引張強度を測定したものである。図８に示すように200℃保持熱処理1000時間および-40/125℃温度サイクル試験1000サイクル行った後でも引張強度の変化はみられない。使用環境を想定した信頼性試験で強度低下が見られなかったことから、銅とニッケルの接合構造体は初期接合で良好な接合ができた場合は、信頼性低下が発生しにくいことが確認できた。また、200℃保持熱処理1000時間および-40/125℃温度サイクル試験1000サイクル行った後の各々のサンプルの接合部断面を観察したところ、初期接合と同様な良好な接合界面が確認され、化合物の形成もみられなかった。 As described above, since it was considered that the reliability degradation under the usage environment is unlikely to occur, the tensile strength after the high temperature standing test at 200 ° C. and the -40 / 125 ° C. temperature cycle test was evaluated. FIG. 8 is a graph showing changes in tensile strength after a 200 ° C. holding heat treatment and a -40 / 125 ° C. temperature cycle test in the joining experiment of the present invention. FIG. 8 shows the tensile strength measured by heat-treating a test piece bonded under the conditions of an initial load of 30 N, a maximum load of 120 N, a bonding time of 0.8 seconds, and an ultrasonic tool amplitude of 21.5 microns. As shown in FIG. 8, no change in tensile strength is observed even after 1000 hours of 200 ° C. heat treatment and 1000 cycles of the -40 / 125 ° C. temperature cycle test. Since no drop in strength was observed in the reliability test assuming the use environment, it was confirmed that the copper-nickel joint structure was less likely to cause a drop in reliability when it was able to achieve a good initial bond. It was. In addition, observation of the cross-section of each sample after carrying out 1000 ° C. holding heat treatment for 1000 hours and -40 / 125 ° C. temperature cycle test for 1000 cycles revealed a good bonding interface similar to that of initial bonding, There was no formation.
　図９は銅とニッケルの超音波接合体をパワーモジュールに適用した際の実施例、図１０は図９中A-Aのパワーモジュールの断面図である。２１は冷却フィン付ベース、２２は絶縁基板、２３は基板上配線、２４は半導体素子、２５は外部接続用リード、２６ははんだである。図９および図１０には示していないが、基板上配線２３と半導体素子２４は金属ワイヤによって電気的に接続されている。基板上配線２３は最表面がニッケルもしくはニッケルを主成分とする構成とする。ただし、基板上配線２３の最表面に１ミクロン厚以下の金や銀や錫、錫系はんだが形成されていてもかまわない。また外部接続用リード２５は基板上配線２３側の面が銅もしくは銅を主成分とする構成とする。基板上配線２３と外部接続用リード２５とが、超音波接続されている。基板上配線２３の表面に金や銀や錫、錫系はんだが形成されている場合には、超音波接合により、金や銀や錫、錫系はんだが破れて、銅とニッケルが接合される。 FIG. 9 is an example when an ultrasonic bonded body of copper and nickel is applied to a power module, and FIG. 10 is a cross-sectional view of the power module AA in FIG. 21 is a base with cooling fins, 22 is an insulating substrate, 23 is wiring on the substrate, 24 is a semiconductor element, 25 is a lead for external connection, and 26 is solder. Although not shown in FIGS. 9 and 10, the on-substrate wiring 23 and the semiconductor element 24 are electrically connected by a metal wire. The on-substrate wiring 23 has a structure in which the outermost surface is mainly nickel or nickel. However, gold, silver, tin, or tin-based solder having a thickness of 1 micron or less may be formed on the outermost surface of the on-substrate wiring 23. Further, the external connection lead 25 is configured such that the surface on the substrate wiring 23 side is mainly composed of copper or copper. The on-substrate wiring 23 and the external connection lead 25 are ultrasonically connected. When gold, silver, tin, or tin-based solder is formed on the surface of the wiring 23 on the substrate, the gold, silver, tin, or tin-based solder is broken by ultrasonic bonding to bond copper and nickel. .
　基板上配線２３と半導体素子２４ははんだで接合される場合が多い。そのため、はんだのぬれ性や接合後の界面化合物の成長抑制を考慮すると、基板上配線２３の表層はニッケル上に１ミクロン以下の金が形成された構造となる可能性がある。一方外部接続用リード２５は大電流を流すため母材は銅が用いられるのが主流であるため、外部接続用リード２５と基板上配線２３の接合は銅とニッケル（１ミクロン厚以下の金がある場合あり）の接合となり、本発明の超音波接合を適用することで接合することが可能となる。これにより、基板上配線２３上に新たなプロセスを付加することなく半導体素子２４と外部接続用リード２５を接合することができる。また、外部接続用リード２５を他の部材にはんだで接続するために、表面に金や銀や錫、錫系はんだを形成した場合も、同様である。本接合を適用した場合の利点は、銅とニッケルをはんだや導電性樹脂などを用いずに直接金属接合できるため電気伝導や熱伝導に優れたリード/基板上配線接合が可能となること、接合部は接合界面の摩擦熱による温度上昇のみの固相接合であり、金属を溶融させて接合する接合方法に比べて接合温度が低いため接合後の界面に発生する応力が小さく、また基板へ対する熱負荷も小さいこと、全率固溶系の銅とニッケルの接合であるため界面に化合物が形成されず接合後の使用環境下で信頼性低下が発生しにくいことである。 The substrate wiring 23 and the semiconductor element 24 are often joined with solder. Therefore, considering the wettability of solder and the suppression of the growth of the interface compound after bonding, the surface layer of the on-substrate wiring 23 may have a structure in which gold of 1 micron or less is formed on nickel. On the other hand, since the lead for external connection 25 allows a large current to flow, copper is mainly used as the base material. Therefore, the connection between the lead for external connection 25 and the wiring 23 on the substrate is made of copper and nickel (gold having a thickness of 1 micron or less). In some cases, the bonding can be performed by applying the ultrasonic bonding of the present invention. As a result, the semiconductor element 24 and the external connection lead 25 can be bonded to the on-substrate wiring 23 without adding a new process. The same applies to the case where gold, silver, tin, or tin-based solder is formed on the surface in order to connect the external connection leads 25 to other members with solder. The advantage of applying this bonding is that copper and nickel can be directly metal-bonded without using solder or conductive resin, so that lead / substrate wiring bonding with excellent electrical and thermal conductivity is possible. The part is a solid-phase bonding with only a temperature rise due to frictional heat at the bonding interface, and the bonding temperature is lower than the bonding method in which the metal is melted and bonded, so the stress generated at the interface after bonding is small, and it is against the substrate The heat load is also small, and since the solid solution is a joint of solid solution copper and nickel, no compound is formed at the interface, and the reliability is unlikely to deteriorate in the use environment after joining.
　図１１は本発明の第二の適用例である銅バンプとニッケル層接合部の断面図である。３０は半導体素子、３１は半導体電極、３２は銅バンプ、４０は基板、４１は基板上配線、４２はニッケル層、５０はアンダーフィルである。銅バンプ３２はニッケル層４２側の銅バンプ３２の最表面が銅もしくは銅を主成分とする構成であれば、バンプ自体は複合体で形成されていてもかまわない。例えば、ニッケルバンプの外周に銅が形成されている構造などが挙げられる。ニッケル層４２は銅バンプ３２側のニッケル層４２の最表面がニッケルもしくはニッケルを主成分とする構成とする。ただし、ニッケル層４２の最表面に１ミクロン厚以下の金が形成されていてもかまわない。基板４０は樹脂基板、セラミック基板、シリコン基板などであればよい。基板上配線４１は各基板で一般的に使用されている構成であり、例えば樹脂基板の場合であれば基板上配線４１は銅が挙げられる。本適用例では、基板上配線４２上に銅バンプ３２を超音波接続する接合構造となり、フリップチップ接合などに広く適用することができる。銅バンプ３２とニッケル層４２を超音波接合後、外周をアンダーフィル５０で封止することで本構造が完成する。 FIG. 11 is a cross-sectional view of a copper bump and nickel layer joint, which is a second application example of the present invention. 30 is a semiconductor element, 31 is a semiconductor electrode, 32 is a copper bump, 40 is a substrate, 41 is a wiring on the substrate, 42 is a nickel layer, and 50 is an underfill. As long as the copper bump 32 has a configuration in which the outermost surface of the copper bump 32 on the nickel layer 42 side is mainly composed of copper or copper, the bump itself may be formed of a composite. For example, a structure in which copper is formed on the outer periphery of a nickel bump can be given. The nickel layer 42 is configured such that the outermost surface of the nickel layer 42 on the copper bump 32 side is mainly composed of nickel or nickel. However, gold having a thickness of 1 micron or less may be formed on the outermost surface of the nickel layer 42. The substrate 40 may be a resin substrate, a ceramic substrate, a silicon substrate, or the like. The on-substrate wiring 41 is a configuration generally used in each substrate. For example, in the case of a resin substrate, the on-substrate wiring 41 may be copper. In this application example, a bonding structure in which the copper bump 32 is ultrasonically connected to the on-substrate wiring 42 is formed, and can be widely applied to flip chip bonding and the like. After ultrasonic bonding of the copper bump 32 and the nickel layer 42, the outer periphery is sealed with an underfill 50 to complete this structure.
　本接合を適用した場合の利点は、銅とニッケルをはんだや導電性樹脂などを用いずに直接金属接合できるため電気伝導や熱伝導に優れたバンプ接合が可能となること、接合部は接合界面の摩擦熱による温度上昇のみの固相接合であり、はんだなどを溶融させて接合する接合方法に比べて接合温度が低いため接合後の界面に発生する応力が小さく、また基板へ対する熱負荷や、基板やパッケージの反りも抑制できること、全率固溶系の銅とニッケルの接合であるため界面に化合物が形成されず接合後の使用環境下で信頼性低下が発生しにくいこと、硬質バンプであるため半導体素子と基板間のギャップを確保することができることである。本実施例では半導体素子３０と基板４０の接合を例にとって記載したが、パッケージと基板間の接合においても同様に適用可能である。 The advantage of applying this bonding is that copper and nickel can be directly metal-bonded without using solder or conductive resin, making it possible to perform bump bonding with excellent electrical and thermal conductivity. This is solid-phase bonding that only raises the temperature due to frictional heat, and the bonding temperature is lower than the bonding method in which solder is melted and bonded, so the stress generated at the interface after bonding is small, and the thermal load on the substrate It is also possible to suppress warping of the substrate and package, and because it is a solid-solid copper-nickel joint, no compound is formed at the interface, and reliability is unlikely to occur in the use environment after joining, and it is a hard bump Therefore, a gap between the semiconductor element and the substrate can be secured. In the present embodiment, the bonding between the semiconductor element 30 and the substrate 40 has been described as an example, but the present invention can be similarly applied to the bonding between the package and the substrate.
１　ニッケル
２　銅
３　超音波ツール圧痕
４　銅/ニッケル接合部
１０　超音波ツール
１１　超音波ツール先端突起
２１　冷却フィン付ベース
２２　絶縁基板
２３　基板上配線
２４　半導体素子
２５　外部接続用リード
２６　はんだ
３０　半導体素子
３１　半導体電極
３２　銅バンプ
４０　基板
４１　基板上配線
４２　ニッケル層
５０　アンダーフィル 1 Nickel 2 Copper 3 Ultrasonic Tool Indentation 4 Copper / Nickel Joint 10 Ultrasonic Tool 11 Ultrasonic Tool Tip Projection 21 Base with Cooling Fin 22 Insulating Substrate 23 On-Substrate Wiring 24 Semiconductor Element 25 External Connection Lead 26 Solder 30 Semiconductor Element 31 Semiconductor electrode 32 Copper bump 40 Substrate 41 On-substrate wiring 42 Nickel layer 50 Underfill

Claims (8)

  1. 　ニッケル部材と銅部材とを超音波接合する接合構造の製造方法において、
    　前記銅部材の銅－ニッケル界面付近の結晶粒径を小さくし、その後に、前記銅部材と前記ニッケル部材とを、前記銅－ニッケル界面で接合することを特徴とする接合構造の製造方法。     In the manufacturing method of the joining structure that ultrasonically joins the nickel member and the copper member,
    A method for producing a joint structure, wherein the crystal grain size in the vicinity of a copper-nickel interface of the copper member is reduced, and then the copper member and the nickel member are joined at the copper-nickel interface.
  2. 　請求項１において、
    　前記銅部材は、銅または銅を主成分とする合金であり、
    　前記ニッケル部材は、ニッケルまたはニッケルを主成分とする合金であることを特徴とする接合構造の製造方法。     In claim 1,
    The copper member is copper or an alloy containing copper as a main component,
    The method for manufacturing a joint structure, wherein the nickel member is nickel or an alloy containing nickel as a main component.
  3. 　請求項１または２において、
    　初期荷重が2.5～12.5MPa、最高荷重が17.5～30MPaの荷重をかけながら接合することを
    特徴とする接合構造の製造方法。     In claim 1 or 2,
    A method of manufacturing a joint structure, characterized by joining while applying an initial load of 2.5 to 12.5 MPa and a maximum load of 17.5 to 30 MPa.
  4. 　請求項１乃至３のいずれかにおいて、
    　前記銅部材内の、超音波接合により微細化された前記界面近傍の粒径が微細化前の粒径の５０％以下であることを特徴とする接合構造の製造方法。     In any one of Claims 1 thru | or 3,
    A method for manufacturing a joint structure, wherein the grain size near the interface refined by ultrasonic joining in the copper member is 50% or less of the grain size before refinement.
  5. 　請求項１乃至４のいずれかにおいて、
    　前記ニッケル部材または銅部材は、その表面に、はんだを用いて他の部材を接続するための金、銀、錫または錫系はんだが形成されおり、
    　当該ニッケル部材または銅部材の表面の金、銀、錫または錫系はんだを破って、前記超音波によるニッケル部材と銅部材との接合が行われることを特徴とする接合構造の製造方法。     In any one of Claims 1 thru | or 4,
    The nickel member or the copper member is formed with gold, silver, tin or tin-based solder for connecting other members using solder on the surface thereof,
    A method for producing a joint structure, wherein the nickel member and the copper member are joined by ultrasonic waves by breaking gold, silver, tin or tin-based solder on the surface of the nickel member or copper member.
  6. 　ニッケル部材と銅部材とが接合された接合構造において、
    　前記銅部材の銅－ニッケル界面付近の結晶粒径が、前記銅部材内部の結晶粒径の５０％以下であることを特徴とする接合構造。     In the joint structure in which the nickel member and the copper member are joined,
    A bonding structure, wherein a crystal grain size in the vicinity of a copper-nickel interface of the copper member is 50% or less of a crystal grain size inside the copper member.
  7. 　請求項６において、
    　前記ニッケル部材の銅－ニッケル界面付近の結晶粒径が、前記ニッケル部材内部の結晶粒径の５０～１００％であることを特徴とする接合構造。     In claim 6,
    A joining structure, wherein a crystal grain size in the vicinity of a copper-nickel interface of the nickel member is 50 to 100% of a crystal grain size inside the nickel member.
  8. 　請求項６または７において、
    　前記銅部材は、銅または銅を主成分とする合金であり、
    　前記ニッケル部材は、ニッケルまたはニッケルを主成分とする合金であることを特徴とする接合構造。     In claim 6 or 7,
    The copper member is copper or an alloy containing copper as a main component,
    The nickel structure is nickel or an alloy containing nickel as a main component.
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