JP2015211111A - Junction structure for electronic device and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a junction structure for an electronic device excellent in the bond strength and heat resistance.SOLUTION: A junction structure for an electronic device includes a first metal layer 11 containing nickel, and a second metal layer 12 formed on the first metal layer 11 and containing gold, tin and nickel. When the content of gold in the second metal layer 12 is x mass% for the whole second metal layer 12, and the content of tin in the second metal layer 12 is y mass% for the whole second metal layer 12, the y/x is 0.8-5.0.

Description

  The present invention relates to a bonding structure for an electronic device and an electronic device including the bonding structure.

  A method of joining members constituting an electronic device via an AuSn brazing material is known (see, for example, Patent Document 1). “Braze material” means an alloy having a melting point lower than that of a member to be joined (such as a substrate or a conductor layer). In joining using an AuSn brazing material, an Au plating layer is formed in advance on both surfaces of a pair of members to be joined. Then, by heating and melting the AuSn brazing material sandwiched between the pair of Au plating layers, a joining structure is formed between the members, and the members are electrically connected. In this joining method, the Au plating layer improves the wettability of the AuSn brazing material to the member surface.

JP 2005-262317 A

  In the conventional bonding method using the AuSn brazing material, the interface (bonding interface) between the AuSn brazing layer formed from the AuSn brazing material and the adjacent Au layer (layer derived from the Au plating layer) Voids (bubbles) or cracks are likely to occur. When a shearing force is applied to a bonded structure in which voids or cracks are formed at the bonded interface, the bonded structure is easily damaged at the bonded interface. That is, it is difficult to achieve a sufficient bonding strength between members in a bonding structure formed using a conventional AuSn brazing material. Therefore, when an impact such as dropping is applied to an electronic device having a conventional joining structure, the joining structure is easily broken and the electrical connection between members is broken.

  In addition, since the conventional bonding structure includes AuSn eutectic, the melting point of the conventional bonding structure is low and is about 278 ° C. Therefore, in the manufacturing process of an electronic device that requires the joining (heating process) of two or more members using a brazing material, the joining structure formed by the primary joining is melted again during the secondary joining. In addition, the electrical connection between the members via the joint structure may be broken. That is, the conventional joint structure is inferior in heat resistance.

  This invention is made | formed in view of the said situation, and it aims at providing the junction structure for electronic devices excellent in joining strength and heat resistance, and an electronic device provided with the said joining structure.

  A bonding structure for an electronic device according to one aspect of the present invention includes a first metal layer containing nickel, and a second metal layer formed on the first metal layer and containing gold, tin, and nickel, The gold content in the second metal layer is x mass% with respect to the entire second metal layer, and the tin content in the second metal layer is y mass% with respect to the entire second metal layer. In some cases, y / x is between 0.8 and 5.0.

  In the junction structure for an electronic device according to one aspect of the present invention, the content of nickel in the second metal layer may be 5 to 25% by mass with respect to the entire second metal layer.

  In the junction structure for an electronic device according to one aspect of the present invention, the second metal layer may contain palladium.

  In the junction structure for an electronic device according to one aspect of the present invention, a portion A in which the content of palladium is larger than the content of other elements may be present in the second metal layer.

  In the junction structure for an electronic device according to one aspect of the present invention, the site A may be located at the center of the second metal layer in a direction perpendicular to the interface between the first metal layer and the second metal layer. .

  The electronic device which concerns on 1 side of this invention is equipped with the said junction structure.

  According to the present invention, there are provided a bonding structure for an electronic device excellent in bonding strength and heat resistance, and an electronic device including the bonding structure.

It is a schematic diagram of the cross section of the electronic device which concerns on one Embodiment of this invention. It is a schematic diagram of the cross section of the junction structure which concerns on one Embodiment of this invention. FIG. 3A and FIG. 3B are schematic views showing a method for manufacturing a junction structure according to an embodiment of the present invention, and are diagrams showing a method for manufacturing when the junction structure does not contain palladium. . FIG. 4A and FIG. 4B are schematic views showing a method for manufacturing a junction structure according to an embodiment of the present invention, and are diagrams showing a method for manufacturing when the junction structure contains palladium.

  Hereinafter, preferred embodiments according to the present invention will be described with reference to the drawings as the case may be. However, the present invention is not limited to the following embodiments. In the drawings, the same or equivalent elements are given the same reference numerals. 1-4 are only schematic diagrams, and the shape and aspect ratio of the junction structure and the electronic device are not limited to those shown in FIGS.

(Junction structure and electronic device)
FIG. 1 shows a cross section of an electronic device 100 (module) of this embodiment. The cross section is a cross section in a direction perpendicular to the surfaces of the first substrate 40 and the second substrate 60 (a direction in which the substrates face each other). The electronic device 100 of this embodiment may include the first substrate 40, the second substrate 60, the chip 90, and the bonding structure 10. The bonding structure 10 is located between the first substrate 40 and the second substrate 60, bonds the first substrate 40 and the second substrate 60, and electrically connects them. The bonding structure 10 is located between the second substrate 60 and the chip 90, bonds the second substrate 60 and the chip 90, and electrically connects them. Note that the electronic device 100 may include a pair of electronic components joined by the joining structure 10.

  The first substrate 40 and the second substrate 60 may be substrates made of an inorganic material such as Si or ceramic. Moreover, the 1st board | substrate 40 and the 2nd board | substrate 60 may be a board | substrate (for example, motherboard) comprised from organic compounds, such as resin. However, the first substrate 40 and the second substrate 60 may be made of an inorganic material having a melting point higher than the heating temperature required for forming the bonding structure 10. This is because the first substrate 40 and the second substrate 60 made of an inorganic material having a high melting point are not easily melted and damaged by the heating necessary for forming the bonding structure 10. The chip 90 may be an electronic component such as a semiconductor element.

  FIG. 2 shows a cross section of the bonding structure 10 for the electronic device 100 according to the present embodiment. The cross section is a cross section in a direction perpendicular to the surfaces of the first substrate 40 and the second substrate 60 (a direction in which the substrates face each other). A first conductor layer 15 is formed on the first substrate 40. The bonding structure 10 includes a first metal layer 11 stacked on the first conductor layer 15 and a second metal layer 12 stacked on the first metal layer 11. The first metal layer 11 includes nickel (Ni). The first metal layer 11 may be made of only nickel. The second metal layer 12 includes gold (Au), tin (Sn), and nickel. The second metal layer 12 may be made of gold, tin, and nickel. The bonding structure 10 may include a third metal layer 13 stacked on the second metal layer 12. A second conductor layer 14 may be formed on the third metal layer 13. The metal included in the third metal layer 13 may be, for example, nickel or titanium (Ti). The first conductor layer 15 and the second conductor layer 14 may be made of a material having excellent electrical conductivity such as gold, silver (Ag), copper (Cu), or aluminum (Al). By providing the first conductor layer 15 and the second conductor layer 14, electrical conductivity between the first substrate 40 and the second substrate 60 is increased. Further, a seed layer 16 made of titanium or the like may be provided between the first conductor layer 15 and the first substrate 40. The seed layer 16 improves the adhesion between the first conductor layer 15 and the first substrate 40. A seed layer 17 made of titanium or the like may be provided between the second conductor layer 14 and the second substrate 60. The seed layer 17 improves the adhesion between the second conductor layer 14 and the second substrate 60.

  The gold content in the second metal layer 12 is x mass% with respect to the entire second metal layer 12, and the tin content in the second metal layer 12 is with respect to the entire second metal layer 12. When y% by mass, y / x is 0.8 to 5.0. y / x may be 0.8 to 4.8. When y / x is in the above range, the second metal layer 12 contains a larger amount of tin than the conventional AuSn brazing filler metal. Therefore, excess tin in the second metal layer 12 is not only gold but also nickel. And form intermetallic compounds. That is, the second metal layer 12 includes not only an intermetallic compound (or alloy) composed of tin and gold, but also an intermetallic compound (or alloy) composed of tin and nickel. Alternatively, the second metal layer 12 includes an intermetallic compound (or alloy) composed of tin, gold, and nickel. As a result, the second metal layer 12 has a higher melting point than a layer composed of AuSn eutectic (conventional AuSn brazing layer). Therefore, the heat resistance of the joint structure 10 according to the present embodiment is improved as compared with the conventional joint structure. Moreover, since the composition of the 1st metal layer 11 and the 2nd metal layer 12 is continuous in the point containing nickel, the 1st metal layer 11 and the 2nd metal layer 12 are joined firmly. Therefore, the bonding structure 10 according to the present embodiment is excellent in bonding strength.

  Since the bonding structure 10 of the present embodiment is excellent in heat resistance, the bonding structure 10 formed by primary bonding in the manufacturing process of an electronic device that requires bonding (heating process) between two or more members, It is difficult to melt again during the secondary joining, and the electrical connection between the members via the joining structure 10 is difficult to break.

  The content of nickel in the second metal layer 12 may be 5 to 25% by mass or 6 to 24% by mass with respect to the entire second metal layer 12. When the content of nickel in the second metal layer 12 is in the above range, the bonding strength of the bonding structure 10 tends to be improved, and the heat resistance of the bonding structure 10 tends to be improved.

  The second metal layer 12 may contain palladium (Pd). The second metal layer 12 may be made of gold, tin, nickel, and palladium. The second metal layer 12 may include an intermetallic compound (or alloy) composed of palladium and at least one metal selected from the group consisting of tin, gold, and nickel. When the second metal layer 12 contains palladium or an intermetallic compound (or alloy) containing palladium and tin, the melting point of the second metal layer 12 is further increased, and the heat resistance of the bonding structure 10 tends to be further improved. is there. Although content of palladium in the 2nd metal layer 12 is not specifically limited, it is 3.0-35.0 mass% with respect to the whole 2nd metal layer 12, 3.3-34.7 mass%, 6.7. It may be -34.7 mass% or 17.0-34.7 mass%. When the content of palladium in the second metal layer 12 is in the above range, the melting point of the second metal layer 12 tends to increase, and the heat resistance of the bonding structure 10 tends to improve.

  When the 2nd metal layer 12 contains palladium, y / x is 1.0-5.0, 1.3-4.8, 3.0-5.0, 3.1-4.8, or 3 .1 to 3.5. When the 2nd metal layer 12 does not contain palladium, y / x may be 0.8-3.0, or 0.8-2.9.

  When the 2nd metal layer 12 contains palladium, the site | part A where content of palladium is larger than content of another element may exist in the 2nd metal layer 12. FIG. In this case, the melting point of the second metal layer 12 tends to increase, and the heat resistance of the bonding structure 10 tends to improve.

  The part A may be located at the center C of the second metal layer 12 in the direction perpendicular to the interface B between the first metal layer 11 and the second metal layer 12. In this case, the melting point of the second metal layer 12 tends to increase, and the heat resistance of the bonding structure 10 tends to improve.

  Although nickel content in the 1st metal layer 11 is not specifically limited, About 60-100 mass% may be sufficient with respect to the 1st metal layer 11 whole. The first metal layer 11 may contain phosphorus (P), sulfur (S), carbon (C), or the like. When these elements are included in the first metal layer 11, the hardness of the first metal layer 11 tends to be improved, and the bonding strength of the bonding structure 10 tends to be improved.

  The third metal layer 13 may contain nickel. When the third metal layer 13 contains nickel, since the composition of the second metal layer 12 and the third metal layer 13 is continuous in that it contains nickel, the second metal layer 12 and the third metal layer 13 are It is firmly joined. Therefore, the joining strength of the joining structure 10 tends to be improved. When the third metal layer 13 includes nickel, the composition of the third metal layer 13 may be substantially the same as the composition of the first metal layer 11.

  The content (unit: mass%) of each element at an arbitrary position in the bonding structure 10 is measured, for example, by the following method. First, the bonding structure 10 is cut along the stacking direction (direction perpendicular to the interface B between the first metal layer 11 and the second metal layer 12). The content of each element is specified by analyzing the exposed cross section of the bonding structure 10 by a method such as energy dispersive X-ray spectroscopy (EDS) or Auger electron spectroscopy (AES). The gold content x and the tin content y are the contents of gold and tin measured at a plurality of locations (for example, 3 locations or 5 locations) arbitrarily selected from the cross section of the second metal layer 12. Calculated by averaging.

  Although the thickness of the 1st metal layer 11 is not specifically limited, What is necessary is just about 0.1-5 micrometers.

  Although the thickness of the 2nd metal layer 12 is not specifically limited, What is necessary is just about 0.1-5 micrometers.

  Although the thickness of the 3rd metal layer 13 is not specifically limited, What is necessary is just about 0.1-5 micrometers.

  Although the thickness of the 1st conductor layer 15 is not specifically limited, What is necessary is just about 1-50 micrometers.

  Although the thickness of the 2nd conductor layer 14 is not specifically limited, What is necessary is just about 1-50 micrometers.

  The thickness of each layer with which the joining structure 10 is provided is measured by the following method, for example. First, the joining structure 10 is cut along the stacking direction. The cross section of the exposed bonding structure 10 is observed with a magnification of about 100,000 times using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM). And the thickness of each layer is calculated by averaging the thickness of each layer measured in the some place (for example, 3 places or 5 places) arbitrarily selected from the cross section.

(Method of manufacturing a joint structure)
A method for manufacturing the joint structure 10 of this embodiment will be described below. The manufacturing method of the joining structure 10 provided with the 2nd metal layer 12 which does not contain palladium among the manufacturing methods of the joining structure 10 of this embodiment is described as a "1st manufacturing method" below. Hereinafter, a method for manufacturing the joint structure 10 including the second metal layer 12 containing palladium is referred to as a “second manufacturing method”.

  As shown in FIGS. 3A and 3B, the first manufacturing method of the bonding structure 10 includes the step of forming the first precursor structure 21 on the surface of the first substrate 40, and the second substrate 60. Forming a second precursor structure 22 on the surface of the first precursor structure 22 and joining the first precursor structure 21 and the second precursor structure 22.

  As shown in FIGS. 4A and 4B, the second manufacturing method of the bonding structure 10 includes the step of forming the first precursor structure 21 on the surface of the first substrate 40, and the second substrate 60. Forming a second precursor structure 28 on the surface thereof, and joining the first precursor structure 21 and the second precursor structure 28.

<First manufacturing method>
[Step of Forming First Precursor Structure 21]
First, the first manufacturing method will be described. FIG. 3B schematically shows a cross section of the first precursor structure 21 formed on the first substrate 40. The first precursor structure 21 is formed on the seed layer 16 formed on the first substrate 40, the first conductor layer 15 formed on the seed layer 16, and the first conductor layer 15. A nickel layer 23 (first base layer) containing as a component and a tin layer 24 (first surface layer) formed on the nickel layer 23 and containing tin as a main component are provided. The first precursor structure 21 is formed by the following method.

  The seed layer 16 and the first conductor layer 15 are formed on the first substrate 40. The seed layer 16 and the first conductor layer 15 may be formed by sputtering, chemical vapor deposition, plating, or the like. The material constituting the seed layer 16 may be titanium or chromium, for example. The seed layer 16 improves the adhesion between the first substrate 40 and the first conductor layer 15. The first conductor layer 15 may be formed directly on the surface of the first substrate 40 without the seed layer 16 interposed. The metal which comprises the 1st conductor layer 15 may be a metal excellent in electrical conductivity, such as copper, gold | metal | money, silver, or aluminum, for example. The first conductor layer 15 may be patterned using a resist film. At the time before peeling the resist film and the seed layer 16 from the surface of the first substrate 40 (excluding the portion where the first conductor layer 15 is formed), each layer described later is formed by either electrolytic plating or electroless plating. May be. After peeling off the resist film and the seed layer 16 from the surface of the first substrate 40, electroless plating that allows easy adjustment of the position and shape of each layer may be used.

  After pre-treating the first conductor layer 15 as necessary, a nickel layer 23 (first base layer) is formed on the first conductor layer 15. When the first conductor layer 15 is made of gold, silver, copper, or an alloy mainly containing these, as a pretreatment of the first conductor layer 15, degreasing, pickling, activation treatment, and the like may be performed. When the first conductor layer 15 is made of aluminum or an aluminum alloy, degreasing, pickling, zincate treatment, or the like may be performed as pretreatment of the first conductor layer 15.

  The formation method of the nickel layer 23 should just be electroless nickel plating or electrolytic nickel plating, for example. In electroless nickel plating, for example, the nickel layer 23 is formed from a plating solution containing a nickel salt, a complexing agent, and a reducing agent. In order to improve the workability of the electroless nickel plating (bath stability, nickel deposition rate), a plating solution containing hypophosphorous acid as a reducing agent may be used. The temperature of the electroless nickel plating solution may be 50 to 95 ° C. or 60 to 90 ° C., for example. The electroless nickel plating solution may contain phosphorus. The pH of the electroless nickel plating solution may be about 4.0 to 6.0. The pH may be adjusted using, for example, dilute sulfuric acid or ammonia.

In electrolytic nickel plating, for example, a plating solution containing nickel sulfate, nickel chloride and boric acid may be used. Moreover, the electrolytic nickel plating solution may contain phosphorus. In this case, the pH of the plating solution may be 4.5 to 5.5, for example. The temperature of a plating solution should just be 40-60 degreeC, for example. Current density during plating may be, for example, 1~7A / dm ^2.

  A tin layer 24 (first surface layer) is formed on the nickel layer 23. The tin layer 24 can be formed by, for example, reduced electroless tin plating or electrolytic tin plating.

  In reducing electroless tin plating, for example, a plating solution containing a tin compound, an organic complexing agent, an organic sulfur compound, an antioxidant, and a reducing agent (titanium compound) may be used. The temperature of a plating solution should just be 40-90 degreeC or 50-80 degreeC, for example.

  In electrolytic tin plating, a ferrostan method, a halogen method, an alkali method, or the like may be employed. In the ferrostan method and the halogen method, an acidic bath is used. In the ferrostan method, tin phenol sulfonate is used. In the halogen method, stannous chloride is used. In the alkaline method, a plating solution containing sodium stannate as a main component is used. In addition, a plating solution containing stannous sulfate or tin borofluoride as a main component may be used.

  Through the above steps, the first precursor structure 21 in which the seed layer 16, the first conductor layer 15, the nickel layer 23 (first underlayer), and the tin layer 24 (first surface layer) are sequentially laminated is formed on the first substrate 40. Formed.

[Step of Forming Second Precursor Structure 22]
FIG. 3A schematically shows a cross section of the second precursor structure 22 formed on the second substrate 60. The second precursor structure 22 is formed on the seed layer 17 provided on the second substrate 60, the second conductor layer 14 formed on the seed layer 17, and the second conductor layer 14, and is formed of nickel or titanium. A layer containing the metal such as the main component (second base layer 27) and a gold layer 25 (second surface layer) formed on the second base layer 27 and containing gold as the main component. The second conductor layer 14 may be formed directly on the surface of the first substrate 40 without the seed layer 17 interposed. The gold layer 25 may be formed on the second conductor layer 14 without providing the second base layer 27.

  The seed layer 17 and the second conductor layer 14 are formed on the second substrate 60. The seed layer 17 and the second conductor layer 14 may be formed by the same method as that for the first precursor structure 21.

  A pretreatment is performed on the second conductor layer 14 as necessary, and then a second underlayer 27 is formed on the second conductor layer 14. The method for forming the second underlayer 27 may be electroless plating or electrolytic plating. When the second underlayer 27 contains nickel as a main component, the second underlayer 27 may be formed by the same formation method as the nickel layer 23 of the first precursor structure 21.

  A gold layer 25 (second surface layer) is formed on the second underlayer 27. The formation method of the gold layer 25 may be, for example, electroless gold plating or electrolytic gold plating. For example, in electroless gold plating, the second underlayer 27 may be immersed in an electroless gold plating solution. Thereby, the gold layer 25 is formed on the surface of the second underlayer 27. The thickness and composition of the gold layer 25 can be freely controlled by the type of electroless gold plating solution, the temperature and pH of the plating solution, the time during which the second underlayer 27 is immersed in the plating solution, and the like. A commercially available electroless gold plating solution may be used as the electroless gold plating solution.

  Through the above steps, the second precursor structure 22 in which the seed layer 17, the second conductor layer 14, the second underlayer 27, and the gold layer 25 (second surface layer) are sequentially stacked is formed on the second substrate 60. .

[Joint Step of First Precursor Structure 21 and Second Precursor Structure 22]
The second substrate 60 is placed on the first substrate 40 so that the tin layer 24 (first surface layer) of the first precursor structure 21 and the gold layer 25 (second surface layer) of the second precursor structure 22 face each other. Place.

  The first precursor structure 21 and the second precursor structure 22 are pressure bonded while heating. By heating, the tin layer 24 having a low melting point is melted before the gold layer 25, and the molten tin layer 24 wets the entire surface of the gold layer 25 and spreads over the entire surface of the gold layer 25. Further, a part of the nickel layer 23 moves (diffuses) into the molten tin layer 24. In addition, the molten tin layer 24 is easy to promote the movement (diffusion) of nickel as compared with the molten conventional AuSn brazing material. Next, the molten tin layer 24, the gold layer 25, and the nickel that has moved into the tin layer 24 are mixed. By cooling these metals, the nickel layer 23 becomes the first metal layer 11, and the second metal layer 12 containing gold, tin, and nickel is formed on the first metal layer 11. Since the molten tin layer 24 wets the entire surface of the gold layer 25 without unevenness and spreads over the entire surface of the gold layer 25, the occurrence of voids and cracks in the bonded structure 10 is suppressed. Since a part of the nickel layer 23 moves (diffuses) into the molten tin layer 24, the composition of the first metal layer 11 and the second metal layer 12 is continuous in that it contains nickel. The second underlayer 27 becomes the third metal layer 13 and is formed on the second metal layer 12. When the second underlayer 27 contains nickel, a part of nickel in the second underlayer 27 may be diffused and mixed with the second metal layer 12 in the bonding step. As a result, the composition of the second metal layer 12 and the third metal layer 13 is continuous in that it contains nickel.

  In the present embodiment, if the nickel layer 23 is not present, the tin atoms constituting the tin layer 24 are excessively moved (diffused) toward the first conductor layer 15 in the joining step, thereby forming the first conductor layer 15. May react with the atoms to form a brittle tin alloy. However, in this embodiment, the nickel layer 23 suppresses the movement of tin from the tin layer 24 to the first conductor layer 15 and suppresses the reaction in which a brittle tin alloy is generated. By suppressing the formation of a brittle tin alloy, the joint strength of the joint structure 10 is improved. As in the case of the nickel layer 23, the second underlayer 27 also suppresses the movement of tin from the tin layer 24 to the second conductor layer 14 and suppresses the reaction between the atoms constituting the second conductor layer 14 and tin. And suppresses the formation of brittle tin alloys.

  Through the steps described above, the bonding structure 10 is formed, and the first substrate 40 and the second substrate 60 are bonded via the bonding structure 10.

  In the manufacture of a joining structure using a conventional AuSn brazing material, a layer made of AuSn brazing material (AuSn brazing layer) is formed instead of the tin layer 24 of the first precursor structure 21. The wettability of the molten AuSn brazing layer is inferior to that of the tin layer 24 melted at the same temperature. Therefore, conventionally, it has been necessary to provide a gold layer in which the AuSn-based brazing material easily spreads between the first underlayer of the first precursor structure and the AuSn-based brazing layer. That is, in the joining using the conventional AuSn brazing material, it was necessary to provide a gold layer on both of the pair of members to be joined. On the other hand, in the present embodiment, since the first precursor structure 21 has the tin layer 24 instead of the conventional AuSn-based brazing layer, the first precursor structure 21 does not need to have a gold layer. That is, in the present embodiment, the bonding structure 10 having excellent bonding strength can be manufactured by providing the gold layer 25 only on one of the members (second precursor structure 22). Therefore, in this embodiment, the amount of gold necessary for manufacturing the joint structure is reduced, and the manufacturing cost of the joint structure is reduced.

The composition and thickness of the first metal layer 11, the composition and thickness of the second metal layer 12, and the composition and thickness of the third metal layer 13 are freely controlled by the following conditions.
Composition, thickness and plating method of the nickel layer 23 (first underlayer).
Composition, thickness and plating method of the tin layer 24 (first surface layer).
Composition, thickness and plating method of the gold layer 25 (second surface layer).
Composition, thickness and plating method of the second underlayer 27.
Heating temperature and heating time in the joining process.

  When the thickness of the tin layer 24 (first surface layer) in the first precursor structure 21 is T1, and the thickness of the gold layer 25 (second surface layer) in the second precursor structure 22 is T2, T1 / T2 May be, for example, 2.0 to 13.0. By adjusting T1 / T2 to the above range, y / x can be controlled to 0.8 to 5.0 or 0.8 to 4.8. In the first manufacturing method, T1 / T2 may be 2.0 to 8.0. In this case, y / x can be controlled to 0.8 to 3.0 or 0.8 to 2.9.

  The thickness T1 of the tin layer 24 (first surface layer) in the first precursor structure 21 may be about 0.1 to 5 μm, for example.

  The thickness T2 of the gold layer 25 (second surface layer) in the second precursor structure 22 may be about 0.1 to 1 μm, for example. Since gold is expensive, the manufacturing cost of the joint structure 10 is suppressed as the gold layer 25 is thinner.

  Although the thickness of the nickel layer 23 in the 1st precursor structure 21 is not specifically limited, What is necessary is just about 0.1-5 micrometers.

  The thickness of the second underlayer 27 in the second precursor structure 22 is not particularly limited, but may be about 0.1 to 5 μm.

  The thickness of each layer provided in the first precursor structure 21 and the second precursor structure 22 is measured using, for example, fluorescent X-ray analysis (XRF). For example, when measuring the thickness T1 of the tin layer 24 (first surface layer) of the first precursor structure 21, the thickness of the tin layer 24 at a plurality of locations (for example, three locations) arbitrarily selected from the surface of the tin layer 24 The thickness is measured using a fluorescent X-ray film thickness meter. By averaging the thickness of the tin layer 24 at each location, the thickness T1 of the tin layer 24 (first surface layer) is calculated. For example, when measuring the thickness T2 of the gold layer 25 (second surface layer) of the second precursor structure 22, the thickness of the gold layer 25 at a plurality of locations (for example, three locations) arbitrarily selected from the surface of the gold layer 25. The thickness is measured using a fluorescent X-ray film thickness meter. By averaging the thickness of the gold layer 25 at each location, the thickness T2 of the gold layer 25 (second surface layer) is calculated.

  The joining process of the 1st precursor structure 21 and the 2nd precursor structure 22 should just heat the 1st precursor structure 21 and the 2nd precursor structure 22 using a flip chip bonder or a reflow furnace. For example, what is necessary is just to heat the 1st precursor structure 21 and the 2nd precursor structure 22 at 280-400 degreeC. For example, the first precursor structure 21 and the second precursor structure 22 may be heated for 0.1 to 120 seconds. When the heating temperature and the heating time are within these ranges, the tin layer 24 is easily melted, and the bonding structure 10 having excellent bonding strength is easily formed.

<Second production method>
[Step of Forming First Precursor Structure 21]
Below, a 2nd manufacturing method is demonstrated. Description of matters common to the first manufacturing method and the second manufacturing method is omitted. FIG. 4B schematically shows a cross section of the first precursor structure 21 formed on the first substrate 40. The first precursor structure 21 in the second manufacturing method may be the same as the first precursor structure 21 in the first manufacturing method. The method for forming the first precursor structure 21 in the second manufacturing method may be the same as the method for forming the first precursor structure 21 in the first manufacturing method.

[Step of Forming Second Precursor Structure 28]
FIG. 4A schematically shows a cross section of the second precursor structure 28 formed on the second substrate 60. The second precursor structure 28 is formed on the seed layer 17 provided on the second substrate 60, the second conductor layer 14 formed on the seed layer 17, and the second conductor layer 14. Formed on the second underlayer 27, a palladium layer 26 (intermediate layer) containing palladium as a main component, and a palladium layer 26. And a gold layer 25 (second surface layer) containing gold as a main component. The second conductor layer 14 may be formed directly on the surface of the first substrate 40 without the seed layer 17 interposed. The palladium layer 26 may be formed on the second conductor layer 14 without providing the second base layer 27.

  A seed layer 17, a second conductor layer 14, and a second underlayer 27 are formed on the second substrate 60. The composition and formation method of the seed layer 17 in the second manufacturing method may be the same as the seed layer 17 formed in the first manufacturing method. The composition and formation method of the second conductor layer 14 in the second manufacturing method may be the same as those of the second conductor layer 14 formed in the first manufacturing method. The composition and formation method of the second underlayer 27 in the second manufacturing method may be the same as those of the second underlayer 27 formed in the first manufacturing method.

  A palladium layer 26 (intermediate layer) is formed on the second underlayer 27. The method for forming the palladium layer 26 may be, for example, electroless palladium plating or electrolytic palladium plating. For example, in electroless palladium plating, the second underlayer 27 is immersed in an electroless palladium plating solution. Thereby, the palladium layer 26 is formed on the surface of the second underlayer 27. The thickness and composition of the palladium layer 26 can be freely controlled by the type of electroless palladium plating solution, temperature, pH, time for immersing the second underlayer 27 in the plating solution, and the like. A commercially available electroless palladium plating solution may be used as the electroless palladium plating solution.

  After the formation of the palladium layer 26, a gold layer 25 (second surface layer) is formed on the palladium layer 26 (intermediate layer) in the same manner as in the first manufacturing method. Through the above steps, the second precursor structure 28 is formed. Note that the palladium layer 26 may be formed on the gold layer 25 after the gold layer 25 is formed on the second underlayer 27.

[Joint Step of First Precursor Structure 21 and Second Precursor Structure 28]
The second substrate 60 is placed on the first substrate 40 so that the tin layer 24 of the first precursor structure 21 and the gold layer 25 of the second precursor structure 28 face each other.

  The first precursor structure 21 and the second precursor structure 28 are pressure bonded while heating. By heating, the tin layer 24 having a low melting point is melted before the gold layer 25, and the molten tin layer 24 wets the entire surface of the gold layer 25 and spreads over the entire surface of the gold layer 25. Further, a part of the nickel layer 23 moves (diffuses) into the molten tin layer 24. In addition, the molten tin layer 24 is easy to promote the movement (diffusion) of nickel as compared with the molten conventional AuSn brazing material. Next, the molten tin layer 24, the gold layer 25, the palladium layer 26, and the nickel that has moved into the tin layer 24 are mixed. By cooling these metals, the nickel layer 23 becomes the first metal layer 11, and the second metal layer 12 containing gold, tin, nickel, and palladium is formed on the first metal layer 11. Since the molten tin layer 24 wets the entire surface of the gold layer 25 without unevenness and spreads over the entire surface of the gold layer 25, the occurrence of voids and cracks in the bonded structure 10 is suppressed. Since a part of the nickel layer 23 moves (diffuses) into the molten tin layer 24, the composition of the first metal layer 11 and the second metal layer 12 is continuous in that it contains nickel. The second underlayer 27 becomes the third metal layer 13 and is formed on the second metal layer 12. When the second underlayer 27 contains nickel, a part of nickel in the second underlayer 27 may be diffused and mixed with the second metal layer 12 in the bonding step. As a result, the composition of the second metal layer 12 and the third metal layer 13 is continuous in that it contains nickel.

  In the joining step, a part A in which the content of palladium is larger than the content of other elements may be formed inside the second metal layer 12 (for example, the center C of the second metal layer 12). The cause of the formation of site A is not always clear. As a result of the high affinity between tin and palladium, the movement (diffusion) of palladium is promoted with the mixing of molten tin layer 24, gold layer 25, nickel moved into tin layer 24 and palladium layer 26, It is presumed that the portion A is formed inside the second metal layer 12 (for example, the center of the second metal layer 12).

  Through the steps described above, the bonding structure 10 is formed, and the first substrate 40 and the second substrate 60 are bonded via the bonding structure 10.

In the bonding structure 10, the composition and thickness of the first metal layer 11, the composition and thickness of the second metal layer 12, and the composition and thickness of the third metal layer 13 are freely controlled by the following conditions. .
Composition, thickness and plating method of the nickel layer 23 (first underlayer).
Composition, thickness and plating method of the tin layer 24 (first surface layer).
Composition, thickness and plating method of the gold layer 25 (second surface layer).
Composition, thickness and plating method of the palladium layer 26 (intermediate layer).
Composition, thickness and plating method of the second underlayer 27.
Heating temperature and heating time in the joining process.

  T1 / T2 may be, for example, 2.0 to 13.0. In the second manufacturing method, T1 / T2 may be 3.6 to 13.0. In this case, y / x can be controlled to 1.0 to 5.0 or 1.3 to 4.8. In the second manufacturing method, T1 / T2 may be 8.0 to 13.0. In this case, y / x can be controlled to 3.0 to 5.0, or 3.1 to 4.8.

  When the thickness of the palladium layer 26 (intermediate layer) in the second precursor structure 28 is T3, T3 / T2 may be, for example, 0.1 to 4.0.

  The thickness T3 of the palladium layer 26 (intermediate layer) in the second precursor structure 28 is not particularly limited, but may be about 0.1 to 1 μm.

  The thickness T3 of the palladium layer 26 (intermediate layer) included in the second precursor structure 28 is measured using, for example, fluorescent X-ray analysis (XRF). For example, before the gold layer 25 is formed on the palladium layer 26, the thickness of the palladium layer 26 at a plurality of locations (for example, three or five locations) arbitrarily selected from the surface of the palladium layer 26 is expressed by fluorescent X-rays. Measure using a film thickness meter. By averaging the thickness of the palladium layer 26 at each location, the thickness T3 of the palladium layer 26 is calculated.

  As mentioned above, although one suitable embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment.

  For example, the nickel layer 23 (first base layer), the tin layer 24 (first surface layer), and the second base layer 27 may be formed by sputtering or chemical vapor deposition instead of electroless plating or electrolytic plating. The gold layer 25 (second surface layer) and the palladium layer 26 (intermediate layer) may be formed by sputtering or chemical vapor deposition instead of electroless plating or electrolytic plating.

  The substrate and the electronic component may be bonded by the bonding structure 10 or the electronic components may be bonded by the bonding structure 10 by the same method as in the present embodiment.

  Hereinafter, although the content of the present invention is explained in detail using an example and a comparative example, the present invention is not limited to the following examples.

Example 1
[Formation process of first precursor structure]
A silicon substrate was prepared as the first substrate. The dimension of the first substrate was 10 × 10 mm, and the thickness of the first substrate was 0.6 mm. A seed layer made of titanium was formed on the surface (bonded portion) of the first substrate, and then a first conductor layer made of copper was formed on the seed layer by electrolytic copper plating. At this time, the dimension and thickness of the first conductor layer were adjusted by patterning using a resist film. The thickness of the first conductor layer was 5 μm, and the dimensions of the conductor layer were 100 × 100 μm. An acidic electrolytic copper plating solution containing copper sulfate was used as a plating solution for electrolytic copper plating.

  The resist film and the seed layer were peeled from the surface of the first substrate (excluding the portion where the first conductor layer was formed). A nickel layer (first underlayer) was formed on the surface of the first conductor layer by electrolytic nickel plating. The thickness of the nickel layer (first base layer) was adjusted to the values shown in Table 1 below. As the plating solution for electrolytic nickel plating, a weakly acidic electrolytic nickel plating solution containing nickel sulfate was used.

  A tin layer (first surface layer) was formed on the surface of the nickel layer by electrolytic tin plating. Through the above steps, the first precursor structure was formed on the first substrate. The thickness T1 of the tin layer (first surface layer) was adjusted to the values shown in Table 1 below. An acidic electrolytic tin plating solution containing stannous sulfate was used as a plating solution for electrolytic tin plating.

[Formation process of second precursor structure]
A silicon substrate was prepared as the second substrate. The dimension of the second substrate was 0.2 × 0.2 mm, and the thickness of the second substrate was 0.6 mm. Next, a seed layer made of titanium and a second conductor layer made of copper were formed on the bonded portion of the second substrate by the above method. The dimension and thickness of the second conductor layer were adjusted by patterning using a resist film. The thickness of the second conductor layer was 5 μm, and the dimension of the second conductor layer was 100 × 100 μm.

  The resist film and the seed layer were peeled from the surface of the second substrate (excluding the portion where the second conductor layer was formed). A nickel layer (second underlayer) was formed on the surface of the second conductor layer by the same electrolytic nickel plating as in the case of the first underlayer. The thickness of the nickel layer (second base layer) was adjusted to the values shown in Table 1 below.

  A gold layer (second surface layer) was formed on the surface of the nickel layer (second base layer) by electrolytic gold plating. The thickness T2 of the gold layer (second surface layer) was adjusted to the value shown in Table 1 below. As the plating solution for electrolytic gold plating, a weakly acidic electrolytic gold plating solution containing potassium gold cyanide was used. Through the above steps, the second precursor structure was formed on the second substrate.

[Joint Step of First Precursor Structure and Second Precursor Structure]
The second substrate was placed on the first substrate so that the tin layer (first surface layer) having the first precursor structure and the gold layer (second surface layer) having the second precursor structure were opposed to each other. The first precursor structure and the second precursor structure were heated at 300 ° C. for 60 seconds in a nitrogen atmosphere, whereby both were pressure-bonded and rapidly cooled. A flip chip bonder was used for the thermocompression bonding. The bonded structure of Example 1 was manufactured through the above steps.

(Example 2)
The junction structure of Example 2 was produced in the same manner as in Example 1 except that the thickness T2 of the gold layer (second surface layer) of the second precursor structure was adjusted to the value shown in Table 1 below.

(Example 3)
In Example 3, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 1 below.

  In the production of the second precursor structure of Example 3, a nickel layer (second base layer) containing phosphorus was formed by electroless nickel plating instead of electrolytic nickel plating. In electroless nickel plating, an electroless nickel plating solution containing hypophosphite ions (reducing agent) was used.

  In the production of the second precursor structure of Example 3, a gold layer (second surface layer) was formed by electroless gold plating instead of electrolytic gold plating. As a plating solution for electroless gold plating, an electroless gold plating solution containing formalin (reducing agent) was used. The thickness T2 of the gold layer (second surface layer) was adjusted to the value shown in Table 1 below.

  A joined structure of Example 3 was produced in the same manner as in Example 1 except for the above items.

Example 4
A joined structure of Example 4 was produced in the same manner as in Example 3 except that the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 1 below.

(Example 5)
A joined structure of Example 5 was produced in the same manner as in Example 3 except that the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 1 below.

(Comparative Example 1)
In Comparative Example 1, a seed layer formed on the first substrate, a first conductor layer formed on the seed layer, a gold layer (first base layer) formed on the first conductor layer 15, A first precursor structure composed of an AuS brazing layer (first surface layer) formed on the gold layer was formed.

  That is, in the production of the first precursor structure of Comparative Example 1, a gold layer was formed as the first underlayer instead of the nickel layer. The gold layer was formed by electrolytic gold plating similar to the second surface layer of Example 1. The thickness of the gold layer (first base layer) was adjusted to the values shown in Table 1 below.

  In the production of the first precursor structure of Comparative Example 1, an AuSn brazing layer made of an AuSn brazing material was formed as the first surface layer instead of the tin layer. The AuSn brazing layer was formed by sputtering. The gold content in the AuSn brazing layer was adjusted to 79% by mass, and the tin content in the AuSn brazing layer was adjusted to 21% by mass. The thickness T1 of the AuSn brazing layer (first surface layer) was adjusted to the values shown in Table 1 below.

  A joined structure of Comparative Example 1 was produced in the same manner as in Example 3 except for the above items.

(Comparative Example 2)
In Comparative Example 2, the gold content in the AuSn brazing layer was adjusted to 66% by mass, and the tin content in the AuSn brazing layer was adjusted to 34% by mass. An attempt was made to produce a joint structure of Comparative Example 2 by the same method as Comparative Example 1 except that the composition of the AuSn brazing layer was changed. However, in Comparative Example 2, even when the first precursor structure and the second precursor structure were heated at 300 ° C. for 60 seconds in a nitrogen atmosphere, the structures were not joined. That is, the joint structure of Comparative Example 2 could not be formed. The inventors speculate that this is because the AuSn brazing layer of Comparative Example 2 was too high in melting point, and thus the AuSn brazing layer did not melt even when heated at 300 ° C. for 60 seconds. .

  Tables 1 and 2 below show T1 / T2 of Examples 1 to 5, respectively. Examples 1 to 5 Each T1 is the thickness of a tin layer (first surface layer) included in the first precursor structure. Examples 1-5 Each T2 is the thickness of the gold layer (2nd surface layer) with which a 2nd precursor structure is provided.

  The methods for forming the first underlayer, the first surface layer, the second surface layer, and the second underlayer of Examples 1 to 5 and Comparative Examples 1 and 2 described above are summarized in Table 2 below.

<Analysis of structure and composition of bonding structure>
Each joining structure of Examples 1-5 and Comparative Example 1 was cut along the stacking direction of each joining structure. The cross section in the lamination direction of each joining structure was observed with SEM. The composition of each cross section was analyzed by EDS.

  In each of the first to fifth embodiments, the first metal layer laminated on the first conductor layer, the second metal layer laminated on the first metal layer, and the second metal layer are laminated. And a third metal layer. It was confirmed that the 1st conductor layer of the 1st substrate and the 2nd conductor layer of the 2nd substrate were joined via each joined structure of Examples 1-5. In each joint structure of Examples 1 to 5, it was confirmed that the first metal layer and the third metal layer contain nickel, and the second metal layer contains gold, tin and nickel. Examples 3 to 5 Each third metal layer was confirmed to contain phosphorus in addition to nickel.

  The joining structure of Comparative Example 1 includes a first metal layer laminated on the first conductor layer, a second metal layer laminated on the first metal layer, and a third metal laminated on the second metal layer. And a layer. With the joint structure of Comparative Example 1, it was confirmed that the first conductor layer of the first substrate and the second conductor layer of the second substrate were joined. The first metal layer of Comparative Example 1 was confirmed to contain gold. It was confirmed that the 2nd metal layer of comparative example 1 contained gold, tin, and nickel, and gold and tin in the 2nd metal layer formed AuSn eutectic. It was confirmed that the 3rd metal layer of comparative example 1 contains nickel and phosphorus.

  Examples 1 to 5 and Comparative Example 1 Nickel, tin, and gold, respectively, belong to the cross section of each second metal layer and are arranged in substantially parallel to the interface between the first metal layer and the second metal layer. The content of was measured. The content of each element at five locations was averaged. Examples 1 to 5 and Comparative Example 1 The average values of the contents of the respective elements in the second metal layers are shown in Table 3 below. Y in the following Table 3 means an average value of tin content in the second metal layer. X in the following Table 3 means an average value of the gold content in the second metal layer. The y / x of each of Examples 1 to 5 and Comparative Example 1 was calculated. Each y / x is shown in Table 3 below.

<Evaluation of structural defects>
The presence or absence of structural defects (cracks and voids) in the cross section of each bonded structure was confirmed based on photographs of the cross sections in the stacking direction of the bonded structures of Examples 1 to 5 and Comparative Example 1 taken by SEM. The presence or absence of structural defects in the cross section of each joint structure is shown in Table 3 below. As shown in Table 3, there were no cracks or voids in the cross sections of the bonded structures of Examples 1 to 5. On the other hand, it was confirmed that the cross section of the joint structure of Comparative Example 1 had cracks and voids.

<Evaluation of bonding strength>
Examples 1 to 5 and Comparative Example 1 The joint strength (shear strength) of each joint structure was evaluated by the following method. A shear tester was used for the evaluation of the bonding strength.

  The first substrate bonded to the bonding structure was fixed. A shear force substantially parallel to the surface of the second substrate was applied to the second substrate bonded to the bonding structure. When the shearing force was increased, the shearing force (maximum strength of the joining structure) at the time when the joining structure was broken was measured. A large shearing force at the time when the joint structure is destroyed means that the joint structure is excellent in joint strength. The evaluation results of the bonding strength are shown in Table 3 below. “A” described in Table 3 means that the shearing force at the time when the bonded structure was destroyed was 100 gf or more. “B” described in Table 3 means that the shearing force at the time when the bonded structure was destroyed was less than 100 gf. “C” described in Table 3 means that the bonding structure was not formed even when the first precursor structure and the second precursor structure were heated at 300 ° C. for 60 seconds in a nitrogen atmosphere.

<Evaluation of heat resistance>
Examples 1-5 and Comparative Example 1 The heat resistance of each joint structure was evaluated by the following tests 1-3.

  In Test 1, the bonded structure was heated at 300 ° C. for 1 minute in a state where the first substrate bonded to the second substrate via the bonded structure was vertically fixed. The amount of movement of the second substrate in the vertical direction accompanying this heating (the amount of deviation due to its own weight) was measured. A large amount of movement means that the joining structure (or the second metal layer) is easily melted and the joining structure is inferior in heat resistance.

  In Test 2, the bonded structure was heated at 330 ° C. for 1 minute in a state where the first substrate bonded to the second substrate through the bonded structure was vertically fixed. The amount of movement in the vertical direction of the second substrate accompanying this heating was measured.

  In Test 3, the bonded structure was heated at 360 ° C. for 1 minute in a state where the first substrate bonded to the second substrate through the bonded structure was vertically fixed. The amount of movement in the vertical direction of the second substrate accompanying this heating was measured.

  The results of Tests 1 to 3 are shown in Table 3 below. “Pass” described in Table 3 means that the amount of movement of the second substrate in the vertical direction was less than 1 μm. “Fail” described in Table 3 means that the amount of movement of the second substrate in the vertical direction is 1 μm or more. “B” described in the grade column of Table 3 means that the result of Test 1 was “pass” and the results of Tests 2 and 3 were “fail”. “C” described in the grade column of Table 3 means that the results of tests 1 to 3 were “fail”.

  As shown in Table 3, it was confirmed that y / x of Examples 1 to 5 was in the range of 0.8 to 5.0. The heat resistance of the bonding structures of Examples 1 to 5 confirmed that the bonding strength of the bonding structures of Examples 1 to 5 is superior to the bonding strength of the bonding structure of Comparative Example 1 is that of the bonding structure of Comparative Example 1. It was confirmed that it was superior to heat resistance.

(Example 6)
[Formation process of first precursor structure]
A first precursor structure of Example 6 was formed on the first substrate in the same manner as in Example 1 except that the thickness of the tin layer (first surface layer) was adjusted to the values shown in Table 4 below.

[Formation process of second precursor structure]
A silicon substrate was prepared as the second substrate. The dimension of the second substrate was 0.2 × 0.2 mm, and the thickness of the second substrate was 0.6 mm. Next, a seed layer made of titanium and a second conductor layer made of copper were formed on the bonded portion of the second substrate by the above method. The dimension and thickness of the second conductor layer were adjusted by patterning using a resist film. The thickness of the conductor layer was 5 μm, and the dimension of the conductor layer was 100 × 100 μm.

  The resist film and the seed layer were peeled from the surface of the second substrate (excluding the portion where the conductor layer was formed). A nickel layer (second base layer) containing phosphorus was formed on the surface of the second conductor layer by electroless nickel plating. The thickness of the nickel layer (second base layer) was adjusted to the values shown in Table 1 below. As a plating solution for electroless nickel plating, an electroless nickel plating solution containing hypophosphite ions (reducing agent) was used.

  A palladium layer (intermediate layer) containing phosphorus was formed on the surface of the nickel layer (second underlayer) by electroless palladium plating. The thickness T3 of the palladium layer (intermediate layer) was adjusted to the values shown in Table 4 below. As a plating solution for electroless palladium plating, an electroless palladium plating solution containing disodium phosphite (reducing agent) was used.

  A gold layer (second surface layer) was formed on the surface of the palladium layer (intermediate layer) by electroless gold plating. The thickness T2 of the gold layer (second surface layer) was adjusted to the values shown in Table 4 below. In electroless gold plating, the same plating solution as that used for forming the gold layer of Example 3 was used. Through the above steps, the second precursor structure was formed on the second substrate.

[Joint Step of First Precursor Structure and Second Precursor Structure]
The second substrate was placed on the first substrate so that the tin layer (first surface layer) having the first precursor structure and the gold layer (second surface layer) having the second precursor structure were opposed to each other. By heating the first precursor structure and the second precursor structure at 300 ° C. for 60 seconds in a nitrogen atmosphere, both were pressure-bonded and rapidly cooled. A flip chip bonder was used for the thermocompression bonding. Through the above steps, the junction structure of Example 6 was produced.

(Example 7)
In Example 7, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the values shown in Table 4 below. In Example 7, the thickness T3 of the palladium layer (intermediate layer) of the second precursor structure was adjusted to the values shown in Table 4 below. Except for these matters, the joint structure of Example 7 was produced in the same manner as in Example 6.

(Example 8)
A junction structure of Example 8 was produced in the same manner as Example 7 except that the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 4 below.

Example 9
A joined structure of Example 9 was produced in the same manner as in Example 7 except that the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 4 below.

(Example 10)
In Example 10, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the values shown in Table 4 below. In Example 10, the thickness T3 of the palladium layer (intermediate layer) of the second precursor structure was adjusted to the values shown in Table 4 below. Except for these, the junction structure of Example 10 was produced in the same manner as in Example 6.

(Example 11)
In Example 11, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the values shown in Table 4 below. In Example 11, the thickness T3 of the palladium layer (intermediate layer) of the second precursor structure was adjusted to the values shown in Table 4 below. Except for these, the junction structure of Example 11 was produced in the same manner as in Example 6.

(Example 12)
In Example 12, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 4 below.

  In the production of the second precursor structure of Example 12, a nickel layer (second base layer) was formed by electrolytic nickel plating instead of electroless nickel plating. In electrolytic nickel plating, the same plating solution as that used for forming the nickel layer (first underlayer) in Example 1 was used.

  In the production of the second precursor structure of Example 12, a palladium layer (intermediate layer) was formed by electrolytic palladium plating instead of electroless palladium plating. An acidic electrolytic palladium plating solution containing palladium chloride was used as a plating solution for electrolytic palladium plating. The thickness T3 of the palladium layer (intermediate layer) was adjusted to the values shown in Table 4 below.

  In the production of the second precursor structure of Example 12, a gold layer (second surface layer) was formed by electrolytic gold plating instead of electroless gold plating. In the electrolytic gold plating, the same plating solution as that used for forming the gold layer (second surface layer) of Example 1 was used. The thickness T3 of the gold layer (second surface layer) was adjusted to the values shown in Table 4 below.

  A junction structure of Example 12 was produced in the same manner as in Example 6 except for the above items.

(Example 13)
In Example 13, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the values shown in Table 4 below. In Example 13, the thickness T3 of the palladium layer (intermediate layer) of the second precursor structure was adjusted to the values shown in Table 4 below. A junction structure of Example 13 was produced in the same manner as in Example 12 except for these matters.

(Example 14)
In Example 14, the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the values shown in Table 4 below. In Example 14, the thickness T2 of the gold layer (second surface layer) of the second precursor structure was adjusted to the value shown in Table 4 below. A junction structure of Example 14 was produced in the same manner as in Example 13 except for these matters.

(Comparative Example 3)
A joined structure of Comparative Example 3 was produced in the same manner as in Example 1 except that the thickness T1 of the tin layer (first surface layer) of the first precursor structure was adjusted to the value shown in Table 4 below.

(Comparative Example 4)
In Comparative Example 4, the thickness T1 of the tin layer (first surface layer) having the first precursor structure was adjusted to the values shown in Table 4 below. In Comparative Example 4, the thickness T2 of the gold layer (second surface layer) having the second precursor structure was adjusted to a value shown in Table 4 below. Except for these matters, the joint structure of Comparative Example 4 was produced in the same manner as in Example 13.

(Comparative Example 5)
A first precursor structure of Comparative Example 5 was produced in the same manner as Comparative Example 1 except that the thickness of the AuSn brazing layer (first surface layer) was adjusted to the values shown in Table 4 below. In Comparative Example 5, a second precursor structure similar to Comparative Example 4 was produced. The second substrate was placed on the first substrate so that the AuSn-based brazing layer (first surface layer) having the first precursor structure and the gold layer (second surface layer) having the second precursor structure were opposed to each other. By heating the first precursor structure and the second precursor structure at 300 ° C. for 60 seconds in a nitrogen atmosphere, both were pressure-bonded and rapidly cooled. A flip chip bonder was used for the thermocompression bonding. The bonded structure of Comparative Example 5 was produced through the above steps.

  The T1 / T2 of Examples 6 to 14 and Comparative Examples 3 and 4 are shown in Table 4 below. Examples 6-14 and Comparative Examples 3 and 4 T1 is the thickness of the tin layer (first surface layer) included in the first precursor structure. Examples 6 to 14 and Comparative Examples 3 and 4 T2 is the thickness of the gold layer (second surface layer) included in the second precursor structure.

  Examples 6 to 14 and Comparative Examples 3 and 4 show T3 / T2 in Table 4 below.

  Examples 6 to 14 and Comparative Examples 3 to 5 show the formation methods of the first underlayer, the first surface layer, the second surface layer, the intermediate layer, and the second underlayer in Table 5 below.

<Analysis of structure and composition of bonding structure>
The structures and compositions of the junction structures of Examples 6 to 14, Comparative Examples, and 3 to 5 were analyzed in the same manner as Example 1 and the like.

  Examples 6 to 14 and Comparative Examples 3 to 5 each have a first metal layer laminated on the first conductor layer, a second metal layer laminated on the first metal layer, and a second bonding structure. And a third metal layer laminated on the metal layer. The first conductor layer formed on the first substrate and the second conductor layer formed on the second substrate are joined by the joining structures of Examples 6 to 14 and Comparative Examples 3 to 5 respectively. It was confirmed that

  In the junction structures of Examples 6 to 14, it was confirmed that the first metal layer and the third metal layer contain nickel, and the second metal layer contains gold, tin, nickel, and palladium. Examples 6 to 11 Each third metal layer was confirmed to contain phosphorus in addition to nickel.

  In the joint structures of Examples 3 and 4, it was confirmed that the first metal layer and the third metal layer contain nickel. It was confirmed that the second metal layer of Comparative Example 3 contained gold, tin, and nickel and did not contain palladium. It was confirmed that the 2nd metal layer of comparative example 4 contained gold, tin, nickel, and palladium. It was confirmed that the gold and tin in the second metal layers of Comparative Examples 3 and 4 formed AuSn eutectic.

  The first metal layer of Comparative Example 5 was confirmed to contain gold. It was confirmed that the 2nd metal layer of comparative example 5 contained gold, tin, nickel, and palladium, and gold and tin in the 2nd metal layer formed AuSn eutectic. It was confirmed that the 3rd metal layer of comparative example 5 contains nickel.

Examples 6 to 14 and Comparative Examples and 3 to 5 The contents of nickel, palladium, tin, and gold were measured at the following three portions a1, a2, and a3 belonging to the cross section of each second metal layer. . The measurement results are shown in Table 6 below.
Part a1: A part located near the interface between the second metal layer and the third metal layer.
Part a2: A part located between the part a1 and the part a3, and the distance from the part a1 is equal to the distance from the part a3. That is, a portion located at the center of the second metal layer in the direction perpendicular to the interface between the first metal layer and the second metal layer.
Part a3: A part located in the vicinity of the interface between the first metal layer and the second metal layer.

  The content of each element in the parts a1, a2, and a3 was averaged. The average values of the contents of the respective elements in the second metal layers of Examples 6 to 14 and Comparative Examples and 3 to 5 are shown in Table 7 below. Z in the following Table 7 means an average value of the content of palladium in the second metal layer. The y / x of each of Examples 6 to 14 and Comparative Examples and 3 to 5 was calculated. Each y / x is shown in Table 3 below. The z / x values of Examples 6 to 14 and Comparative Examples and 3 to 5 were calculated. Each z / x is shown in Table 3 below.

<Evaluation of structural defects>
Based on the photograph of the cross section in the lamination direction of each joining structure of Examples 6-14 and Comparative Examples 3-5 photographed by SEM, the presence or absence of structural defects (cracks and voids) in the section of each joining structure was confirmed. The presence or absence of structural defects in the cross section of each joint structure is shown in Table 7 below. As shown in Table 7, there were no cracks or voids in the cross sections of the bonded structures of Examples 6 to 14 and Comparative Examples 3 and 4. On the other hand, it was confirmed that the cross section of the joint structure of Comparative Example 5 had cracks and voids.

<Evaluation of bonding strength>
In the same manner as in Example 1 and the like, the joint strengths of the joint structures of Examples 6 to 14 and Comparative Examples 3 to 5 were evaluated. The evaluation results of the bonding strength are shown in Table 7 below.

<Evaluation of heat resistance>
By the method similar to Example 1 etc., the heat resistance of each junction structure of Examples 6-14 and Comparative Examples 3-5 was evaluated by Tests 1-3. The results of Tests 1 to 3 are shown in Table 7 below. “A” described in the grade column of Table 7 means that the results of tests 1 and 2 were “pass” and the result of test 3 was “fail”. “A +” described in the grade column of Table 7 means that the results of tests 1 to 3 were “pass”.

  As shown in Table 7, in Examples 6 to 14, it was confirmed that y / x was in the range of 0.8 to 5.0.

  It was confirmed that the bonding strengths of Examples 6 to 14 and Comparative Examples 3 and 4 were superior to those of Comparative Example 5.

  It was confirmed that the heat resistance of the joining structures of Examples 6 to 14 was superior to the heat resistance of the joining structures of Comparative Examples 3 to 5. It was confirmed that the heat resistance of the joining structures of Examples 6, 10 and 11 in which y / x is in the range of 3.1 to 3.5 is superior to the heat resistance of the joining structures of other examples. It was done. Among the second metal layers of Examples 6, 10 and 11, it was confirmed that the second metal layer of Examples 6 and 10 includes a portion A in which the content of palladium is larger than the content of other elements. . It was confirmed that the part A of Examples 6 and 10 was located at the center (part a2) of the second metal layer in the direction perpendicular to the interface between the first metal layer and the second metal layer.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture an electronic device provided with the joining structure excellent in joining strength and heat resistance.

  DESCRIPTION OF SYMBOLS 10 ... Joining structure, 11 ... 1st metal layer, 12 ... 2nd metal layer, 13 ... 3rd metal layer, 14 ... 2nd conductor layer, 15 ... 1st conductor layer, 16, 17 ... Seed layer, 21 ... 1st 1 precursor structure, 22, 28 ... 2nd precursor structure, 23 ... nickel layer (first underlayer), 24 ... tin layer (first surface layer), 25 ... gold layer (second surface layer), 26 ... palladium layer (Intermediate layer), 27 ... second underlayer, 40 ... first substrate, 60 ... second substrate, 90 ... chip (electronic component), 100 ... electronic device, A ... the content of palladium is the content of other elements Larger than B, B: interface between the first metal layer and the second metal layer, C: center of the second metal layer.

Claims (6)

A first metal layer comprising nickel;
A second metal layer formed on the first metal layer and comprising gold, tin and nickel;
With
The gold content in the second metal layer is x mass% with respect to the entire second metal layer,
When the content of tin in the second metal layer is y% by mass with respect to the entire second metal layer,
y / x is 0.8 to 5.0,
Bonding structure for electronic devices. The content of nickel in the second metal layer is 5 to 25% by mass with respect to the entire second metal layer.
The junction structure for an electronic device according to claim 1. The second metal layer includes palladium;
The junction structure for electronic devices according to claim 1 or 2. Site A where the content of palladium is larger than the content of other elements is present in the second metal layer.
The junction structure for an electronic device according to claim 3. The portion A is located at the center of the second metal layer in a direction perpendicular to the interface between the first metal layer and the second metal layer;
The joining structure for an electronic device according to claim 4. Comprising the joining structure according to any one of claims 1 to 5,
Electronic devices.

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