JP2016166417A - Production method of electric conduction particles, anisotropic conductive adhesive, and parts mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing deformations of particles in the case where an insulator film is formed on the surfaces of metal particles, and capable of keeping a high connection reliability while retaining the insulation between electrodes at the time of connecting a substrate and a member to be connected.SOLUTION: An insulating film 12 is formed on the surfaces 11 of metal particles 10 of a metal of a low melting point by a sputtering method while applying the vibrations in an atmosphere containing oxygen, thereby to produce conductive particles 1. The conductive particles 1 are dispersed into a resin component to form an anisotropic conductive adhesive, which are then arranged and depressed between electrodes, so that the molten metal particles 10 are solidified to connect the electrodes electrically.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing conductive particles in which an insulating film is formed on the surface of soft metal particles by physical vapor deposition, an anisotropic conductive adhesive containing the conductive particles, and a component mounting method.

  Anisotropic conductive adhesive (ACA) is used as a connection material for connecting an electronic component having a large number of electrodes to a substrate or the like.

  Anisotropic conductive adhesives include printed wiring boards, glass substrates for LCD (liquid crystal display), flexible printed circuits (FPC), IC (integrated circuit), LSI (large-scale integration) When connecting an electronic component (connected member) such as a semiconductor element or a package, electrical connection and mechanical fixation are performed so that the conductive state between the opposing electrodes is maintained and insulation between adjacent electrodes is maintained. Connection material to be performed (anisotropic conductive connection).

  Conductive particles are blended in the anisotropic conductive adhesive, and various particles have been proposed and used from the viewpoint of improving connection reliability and lowering the resistance of connection points. Examples of the conductive particles include metal particles such as tin (Sn), lead (Pb), silver (Ag), aluminum (Al), and nickel (Ni), solder alloy particles, inorganic fine particles such as glass and ceramics, heat Disclosed are particles in which a metal thin film is coated on resin particles such as a curable resin.

  In particular, since high reliability is easily obtained by contact connection, many studies have been made on anisotropic conductive adhesives containing solder alloy particles capable of metal bonding as conductive particles (for example, Patent Document 1). , 2). The solder alloy particles have a melting point lower than that of the metal material to be connected, and are designed to join metals by melting and flowing and then solidifying.

  By the way, although the conventional solder alloy particles contain lead, in recent years, the demand for lead-free solder is increasing from the viewpoint of the adverse effect of lead on the human body and the environment. Currently, for lead-free solder, lead-free solder alloys with tin as the main component have been developed, and zinc (Zn), bismuth (Bi), indium (In), silver, copper (Cu), etc. are included as alternatives to lead. It is. The solder alloy particles are produced by an atomizing method or the like that obtains particles having a certain particle diameter by spraying a molten alloy containing a component replacing lead from a predetermined nozzle.

JP 2006-108523 A JP2013-124330A JP-A-7-105716

  In recent years, as represented by a liquid crystal display device or the like, with the miniaturization and high performance of a device, higher definition of a circuit that is an object of anisotropic conductive connection is progressing. Along with this, with the increasing demand for fine pitches between circuits, there is a concern about the occurrence of short circuits during connection.

  In order to satisfy the demand for fine pitch, etc., particles having an insulating layer formed on the surface of metal particles are used as insulating conductive particles blended in the anisotropic conductive adhesive. A typical example is a conductive particle in which an insulating resin layer is formed on the surface of a metal particle by hybridization (see, for example, Patent Document 3).

  However, in a physico-mechanical method represented by hybridization, when an insulating layer is formed on the surface of a soft metal particle (soft metal particle) having a low melting point such as a solder alloy particle, the particle is deformed and can be put to practical use. It becomes difficult. Further, Patent Document 3 does not disclose or suggest any method for forming the insulating layer on the surface of the soft metal particle by suppressing the deformation of the particle.

  The present invention has been proposed in view of such circumstances, and in the case where an insulating film is formed on the surface of a soft, low-melting metal particle, the deformation of the particle is suppressed, and the substrate, the connected member, An object of the present invention is to provide a method for producing conductive particles capable of ensuring insulation between electrodes at the time of connection and maintaining high connection reliability, and an anisotropic conductive adhesive containing the conductive particles. To do.

In order to achieve the above-described object, the present invention introduces a sputtering gas into a vacuum chamber in which a sputtering target is arranged, and sputters the sputtering rig target to form a thin film on the surface of low melting point metal particles. A method for producing conductive particles for forming particles, wherein a plurality of the metal particles are arranged in a vibration container, and the target is sputtered while vibrating the metal particles to vibrate the metal particles. In the method for producing conductive particles, an insulating film is formed on a surface, and the conductive particles in which the metal particles are covered with the insulating film are formed.
The present invention also relates to a method for producing conductive particles, wherein before the formation of the insulating film is started, the pressure in the vacuum chamber is greater than 9 × 10 ⁻⁵ Pa and greater than 2 × 10 ⁻² Pa. Is a method for producing conductive particles with a low pressure.
Moreover, this invention is a manufacturing method of the particle | grains for electroconductivity, Comprising: A solder alloy is used for the said metal particle, It is a manufacturing method of the particle | grains for electroconductivity characterized by the above-mentioned.
The present invention is also a method for producing conductive particles, wherein the insulating film has a thickness in a range of more than 2 nm and less than 500 nm.
The present invention is also a method for producing conductive particles, wherein the insulating film is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. This is a method for producing conductive particles.
The present invention is also a method for producing conductive particles, wherein the sputtering target made of metal is used, and oxygen gas is contained in the sputtering gas.
The present invention is also an anisotropic conductive adhesive having a resin component having adhesiveness and a plurality of conductive particles dispersed in the resin component, wherein the conductive particles are made of a low melting point metal. An anisotropic film comprising metal particles and an insulating film covering the metal particles, wherein the insulating film is formed on a surface of the metal particles by a sputtering method while applying vibration in an atmosphere containing oxygen. Conductive adhesive.
Moreover, this invention is an anisotropic conductive adhesive, Comprising: The said low melting metal is an anisotropic conductive adhesive characterized by being a solder alloy.
Further, the present invention is an anisotropic conductive adhesive, wherein the thickness of the insulating film is a value in the range of thicker than 2 nm and thinner than 500 nm.
Further, the present invention is an anisotropic conductive adhesive, wherein the insulating film is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. It is an anisotropic conductive adhesive.
Moreover, this invention is an anisotropic conductive adhesive, Comprising: The average particle diameter of the said metal particle is an anisotropic conductive adhesive made into the value of the range of 1 micrometer or more and 20 micrometers or less.
Further, the present invention provides an arrangement step of disposing an anisotropic conductive adhesive containing a plurality of conductive particles in an adhesive resin component between an electrode of a substrate and an electrode of a connected member, A heating and pressing step for pressing the substrate and the connected member in a direction approaching each other while heating the anisotropic conductive adhesive, and a cooling step for cooling the heated anisotropic conductive adhesive. A component mounting method for mechanically fixing the substrate and the member to be connected by the cooled resin component, wherein the conductive particles include an insulating film on a surface of metal particles made of a low melting point metal. Using the covered particles, in the heating and pressing step, the anisotropic conductive adhesive is heated to melt the metal particles, and is positioned between the electrode of the substrate and the electrode of the connected member. Destroying the insulating film of the pressed conductive particles And releasing the melt of the pressed metal particles of the conductive particles into the resin component to bring the melt into contact with the electrode of the substrate and the electrode of the connected member. The anisotropic conductive adhesive is cooled to solidify the molten material that contacts the electrode of the substrate and the electrode of the connected member, and the electrode of the substrate and the connected material are solidified by the solidified melt. It is the mounting method of the components which electrically connect the said electrode of a member.
Further, the present invention is a component mounting method, wherein the low melting point metal uses an alloy that melts at a temperature of 220 ° C. or less.
Further, the present invention is a component mounting method, wherein the low melting point metal uses an alloy that melts at a temperature of 150 ° C. or higher.
The present invention is also a component mounting method, wherein the low-melting-point metal does not contain lead and uses a solder alloy containing 50% or more of tin.
The present invention is also a component mounting method, which is a component mounting method using an oxide film as the insulating film.

  Therefore, the method for producing conductive particles according to one embodiment of the present invention forms an insulating film on the surface of metal particles containing a soft metal by sputtering while applying vibration in an atmosphere containing oxygen. The deformation of the metal particles during the formation of can be suppressed.

The conductive particles according to one embodiment of the present invention are soft and have a low melting point, and in the manufacturing method, the ultimate vacuum V (Pa) before the sputtering treatment is 9 × 10 ⁻⁵ <V <2 × 10 ⁻² . It is preferable to adjust so that it becomes.

Therefore, in the method for producing conductive particles according to one embodiment of the present invention, by adjusting the ultimate vacuum V (Pa) before the sputtering treatment to be 9 × 10 ⁻⁵ <V <2 × 10 ^−2. An insulating film having appropriate adhesion and film density can be obtained.

  In the method for producing conductive particles according to one embodiment of the present invention, the soft metal is preferably a solder alloy.

  Therefore, in the method for producing conductive particles according to one embodiment of the present invention, the soft metal is a solder alloy, so that the conductive particles can be dissolved at a low temperature.

  In the method for producing conductive particles according to one embodiment of the present invention, it is preferable to adjust the thickness T (nm) of the insulating film so that 2 <T <500.

  Therefore, in the method for manufacturing conductive particles according to one embodiment of the present invention, by adjusting the thickness T (nm) of the insulating film to satisfy 2 <T <500, the connection between the substrate and the connected member can be performed. It becomes possible to easily peel the insulating film from the surface of the conductive particles.

  In the method for manufacturing conductive particles according to one embodiment of the present invention, the insulating film is a thin film of an insulating material such as an oxide or a nitride, and the silicon nitride thin film is also included in the insulating film. It is preferably a metal oxide thin film containing at least one of aluminum, titanium oxide, and niobium oxide.

  Therefore, in the method for producing conductive particles according to one embodiment of the present invention, the insulating film is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. Insulation between the electrodes can be ensured at the time of connection between the substrate and the member to be connected, and a metal oxide corresponding to the application can be selected as appropriate.

An anisotropic conductive adhesive according to another embodiment of the present invention for achieving the above-described object is provided with a conductive particle having an insulating film formed on the surface of metal particles and a binder material. In the anisotropic conductive adhesive, the metal particles include a soft metal, and the insulating film is formed on the surface of the metal particles by sputtering while applying vibration in an atmosphere containing oxygen.
A case where an insulating film is formed by sputtering a target made of an insulating material such as oxide or silicide in a sputtering atmosphere not containing oxygen gas is also included.

  Therefore, in the anisotropic conductive adhesive according to another aspect of the present invention, the metal particles contain a soft metal, and the insulating film is formed on the surface of the metal particles by sputtering while applying vibration in an atmosphere containing oxygen. Therefore, it is possible to ensure insulation between the electrodes and maintain high connection reliability when the substrate and the member to be connected are connected.

  In the anisotropic conductive adhesive according to another aspect of the present invention, the average particle diameter D (μm) of the metal particles is preferably 1 ≦ D ≦ 20.

  Therefore, in the anisotropic conductive adhesive according to another aspect of the present invention, the average particle diameter D (μm) of the metal particles is 1 ≦ D ≦ 20. Can be used.

  According to the present invention, deformation of particles is suppressed when an insulating film is formed on the surface of metal particles. When the connected member is mounted on the substrate, insulation between the electrodes can be ensured when the substrate and the connected member are connected, and high connection reliability can be maintained.

It is sectional drawing which showed typically the mode of the cross section of the particle | grains for electroconductivity concerning one embodiment of this invention. It is the schematic which showed the one part outline of the sputtering device for producing the electroconductive particle concerning one embodiment of this invention. (a)-(c): Drawing for demonstrating the component mounting method of this invention

  A specific embodiment to which the present invention is applied (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings along the following items. Note that the present invention is not limited to the following embodiment, and various modifications can be made without departing from the scope of the present invention.

1. 1. Conductive particles 2. Method for producing conductive particles 3. Anisotropic conductive adhesive Method for producing anisotropic conductive adhesive

[1. Conductive particles]
Although the details of the conductive particles will be described later, they are obtained by the method for manufacturing conductive particles according to the present embodiment. As shown in FIG. 1, the conductive particle 1 is obtained by forming an insulating film 12 on the surface 11 of a metal particle 10.

  The average particle diameter of the conductive particles 1 is appropriately determined according to the average particle diameter D of the metal particles 10 described later and the film thickness T of the insulating film 12, and the shape of the conductive particles 1 is particularly limited. However, it can be determined appropriately according to the application.

  The metal particles 10 include a soft metal, so-called soft metal, and the metal particles 10 may include inevitable impurities that are unintentionally mixed during the manufacturing process. Examples of the soft metal applicable to the conductive particles 1 include a solder alloy.

  Conventionally, in order to mount electronic components (members to be connected) on a substrate such as an electronic circuit, solder (lead-containing solder) that is an alloy of lead (Pb) and tin (Sn) has been used in large quantities. However, since lead is harmful to the human body and there are concerns about adverse effects on the natural environment as waste, development and popularization of solder not containing lead (lead-free solder) is currently underway.

  Therefore, as described above, lead-free solder can be used for the metal particles 10 in the conductive particles 1 from the viewpoint of safety to the human body and the environment.

  As the low melting point soft metal applicable to the conductive particles 1, a metal having a melting point within a temperature range of 150 ° C. or higher and 220 ° C. or lower and which melts when heated to a temperature within the temperature range is suitable. An example is lead-free solder. If the high connection reliability as an anisotropic conductive adhesive mentioned later is securable, it will not specifically limit. However, when the conductive particles 1 are applied to the anisotropic conductive adhesive, the lead-free solder having a melting temperature of less than 150 ° C. has a melting point lowered by adding In (indium) or Bi (bismuth). Addition of such a metal may have poor mechanical strength as a solder and poor connection reliability. On the other hand, if the melting temperature of the lead-free solder exceeds 220 ° C., there is a risk of thermal destruction or deterioration of the substrate or the connected member, which is not preferable. Therefore, it is preferable to use lead-free solder having a melting temperature in the temperature range of 150 ° C. or higher and 220 ° C. or lower for the conductive particles 1.

  Examples of such lead-free solder include SnAgCu series containing Sn, Ag (silver) and Cu (copper), SnZnBi series containing Sn, Zn (zinc) and Bi, SnCu series containing Sn and Cu, Sn and Ag. SnAgInBi system including In, Bi, SnZnAl system including Sn, Zn, and Al (aluminum). The composition ratio of the metal species contained in the lead-free solder is not particularly limited and can be appropriately adjusted according to the application.

  The average particle diameter D (μm) of the metal particles 10 is preferably in the range of 1 ≦ D ≦ 20 because the metal particles 10 are used for fine pitch wiring or the like where the space between the electrodes is narrow. When the average particle diameter D of the metal particles 10 is less than 1 μm, a large amount of conductive particles 1 are required to connect the substrate and the connected member when used for the anisotropic conductive adhesive. There is a possibility that problems such as an increase and a decrease in coatability may occur. In such a case, since the gap between the connection terminals of the substrate and the connected member is inevitably small, the amount of binder material (described later) around the conductive particles 1 is reduced, and the connection is made. There is a risk of lowering reliability. On the other hand, when the average particle diameter D of the metal particles 10 exceeds 20 μm, it cannot be used for fine pitch wiring or the like, which is not preferable. Therefore, the average particle diameter D of the metal particles 10 is preferably in the range of 1 ≦ D ≦ 20.

  Moreover, it does not specifically limit about the shape of the metal particle 10, It can determine suitably according to a use.

  The insulating film 12 is a metal oxide, and the insulating film 12 may contain inevitable impurities that are unintentionally mixed during the manufacturing process.

  The insulating film 12 of the conductive particle 1 can be formed on the surface 11 of the metal particle 10 and is not particularly limited as long as the insulating property of the conductive particle 1 can be secured. For example, the oxide film includes silicon oxide, Examples thereof include aluminum oxide, titanium oxide, and niobium oxide. Examples of the nitride film include silicon nitride. The insulating film 12 only needs to contain at least one of the metal oxides described above.

In addition, the material of the insulating film 12 may include materials having different valences or different crystal structures. In the case of an oxide, for example, silicon oxide (SiO _x (1 ≦ x ≦ 2)) includes silicon monoxide (SiO) and silicon dioxide (SiO ₂ ). Moreover, in aluminum oxide (AlO _x (0.5 ≦ x ≦ 1.5)), aluminum oxide (III) (Al ₂ O ₃ ), aluminum oxide (II) (AlO), aluminum oxide (I) (Al ₂ O) and the like, and aluminum (III) oxide has crystal structures such as α-alumina (corundum type) and γ-alumina (spinel type). Further, in titanium oxide (TiO _x (1 ≦ x ≦ 2)), there are titanium dioxide (IV) (TiO ₂ ), titanium oxide (II) (TiO), etc. In titanium dioxide (IV), anatase type, There are crystal structures such as rutile type and brookite type. There is also niobium oxide (V) (Nb ₂ O ₅ ).

The film thickness T (nm) of the insulating film 12 is 2 <T <because the insulating film 12 can be easily peeled from the surface 11 of the conductive particles 1 when the substrate and the connected member are connected. It is preferably within the range of 500, more preferably within the range of 5 ≦ T ≦ 480, and particularly preferably within the range of 5 ≦ T ≦ 200. If the thickness T of the insulating film 12 is 2 nm or less, it is not preferable because a short circuit between adjacent electrodes cannot be prevented when the substrate and the connected member are connected. On the other hand, when the thickness T of the insulating film 12 is 500 nm or more, the connection resistance value at the time of connection between the substrate and the connected member becomes high, which is not preferable.
Therefore, the film thickness T of the insulating film 12 is preferably in the range of 2 <T <500, more preferably in the range of 5 ≦ T ≦ 480, and particularly in the range of 5 ≦ T ≦ 200. Preferably there is.

[2. Method for producing conductive particles]
The method for producing conductive particles according to the present embodiment includes a thin film forming step of forming an insulating film 12 on the surface 11 of the metal particle 10 shown in FIG.

  In the thin film forming step, deformation of the metal particles 10 may be suppressed and the surface 11 of the metal particles 10 may be covered with the insulating film 12. For example, physical vapor deposition (PVD) can be used. Examples of physical vapor deposition include sputtering, sputtering laser (PLD), ion plating, ion beam deposition (IBD), and the like. Of these, the sputtering method is used because it can be easily produced, has high productivity, and has good film formability.

First, the sputtering apparatus 4 of FIG. 2 used in the thin film forming process will be described.
The sputtering apparatus 4 includes a vacuum chamber 3, and a backing plate 31 that is a cathode electrode is disposed on the ceiling side inside the vacuum chamber 3.

  A sputtering target 32 made of a metal or an insulating material is disposed on the backing plate 31. Examples of the metal used for the sputtering target 32 include silicon (Si), aluminum (Al), titanium (Ti), niobium (Nb), and the like.

  A vibration device 23 is disposed outside the vacuum chamber 3. A vibration shaft 24 connected to the vibration device 23 is hermetically inserted into the bottom surface of the vacuum chamber 3, and the upper end of the vibration shaft 24 is the vacuum chamber 3. It is supposed to be located inside. The vibration device 23 may be disposed inside the vacuum chamber 3.

  A vibration container 21 is disposed at the upper end of the vibration shaft 24. The vibrating container 21 is located below the sputtering target 32, the opening 33 of the vibrating container 21 is directed upward, and the bottom surface of the vibrating container 21 is connected to the sputtering target 32 via the opening 33 of the vibrating container 21. It is made to face.

  A vacuum evacuation device 35 is connected to the vacuum chamber 3, and when the vacuum evacuation device 35 is operated, the inside of the vacuum chamber 3 is evacuated and a vacuum atmosphere is formed inside the vacuum chamber 3. .

  A gas introducing device 36 is connected to the vacuum chamber 3 so that the gas disposed in the gas introducing device 36 can be introduced into the vacuum chamber 3 in a vacuum atmosphere. Here, an insulator is generated from a gas introducing device 36 by reacting with an inert gas such as Ar gas, a sputtering gas such as nitrogen gas, an inert gas such as Ar gas, or nitrogen gas with a metal such as oxygen gas. A sputtering gas to which a reactive gas is added can be introduced.

In addition, when performing the film-forming process on the surface of the metal particle 10 by sputtering method, it is common to use a vibration auxiliary material (vibration amplification means) made of metal or resin. However, in the method for producing particles according to the present invention, as described above, since the metal particles 10 are made of a soft and low-melting metal, deformation or deterioration due to collision between the metal particles 10 and the vibration assisting material occurs. There is a fear. Therefore, in order to prevent the occurrence of such a problem, it is preferable to form the insulating film 12 on the surface 11 of the metal particle 10 without using a vibration assisting material.
However, the use of the vibration assisting material is not hindered as long as the vibration assisting material is provided with a measure for preventing a problem with the metal particles 10.

  Next, the detail of the process of forming the insulating film 12 on the surface 11 of the metal particle 10 using the sputtering apparatus 4 described above will be described.

  First, the door 39 of the vacuum chamber 3 is opened, a predetermined amount of the metal particles 10 are arranged in the vibrating container 21, the door 39 is closed, and the inside of the vacuum chamber 3 is shut off from the atmosphere, and then the vacuum exhaust device 35 is operated. Then, after the inside of the vacuum chamber 3 is evacuated to a vacuum atmosphere by the evacuation device 35, the vibration device 23 is operated to generate vibration. Here, the vibration is in the vertical direction, and the vibration in the vertical direction is transmitted to the vibration container 21 by the vibration shaft 24 without the air entering the vacuum chamber 3, so that the vibration container 21 vibrates, and the metal in the vibration container 21. The vibration of the particle 10 is started.

  On the bottom surface of the vibration container 21, a plurality of metal particles 10 are disposed in an amount that forms a single layer or a plurality of layers, and between the metal particles 10 and the metal particles 10, or between the metal particles 10 and the bottom surface of the vibration container 21. There is no adsorptive power between the metal particles 10 and the wall surfaces, and the metal particles 10 can be rotated and moved independently of each other inside the vibration container 21, and when the vibration container 21 is vibrated, the metal particles 10. Vibrates and moves in the vertical and horizontal directions and rotates.

When the introduction of the sputtering gas is started while the inside of the vacuum chamber 3 is evacuated after the pressure V inside the vacuum chamber 3 is lowered to a predetermined pressure by the vacuum exhaust, the pressure V inside the vacuum chamber 3 increases.
Note that when the sputtering gas is introduced, the exhaust speed of the vacuum exhaust device 35 can be lowered.

A sputtering power source 38 is connected to the backing plate 31.
The sputtering gas is introduced in a state in which the flow rate is controlled by the flow rate control device, the pressure V inside the vacuum chamber 3 is stabilized at a predetermined value, and a sputtering gas atmosphere having a constant pressure is formed inside the vacuum chamber 3. After that, when the sputtering power source 38 is activated and a voltage is applied to the backing plate 31, sputtering of the sputtering target 32 is started.

  Of the sputtered particles struck out from the surface of the sputtering target 32 by sputtering, the sputtered particles that have passed through the opening 33 of the vibrating container 21 reach a place where the metal particles 10 are not shaded when viewed from the sputtering target 32. As a result, a thin film is formed at the reached position.

  As each metal particle 10 is moved and rotated in the vertical and horizontal directions by vibration, the shadowed part faces the sputtering target 32 and the sputtered particle reaches the part where no thin film is formed. Since the thin film is formed, the sputtered particles reach the entire surface of one metal particle 10 by vibrating a predetermined number of times, and the thin film is formed on the entire surface of each metal particle 10.

  When the sputtering target 32 is an insulator, the insulating film 12 which is a thin film of an insulator is formed. When the sputtering target 32 is a metal, a reactive gas is included in the sputtering gas, and the sputtering particles are flying. Alternatively, the sputtering particles and the reactive gas are reacted on the surface of the metal particles 10 to form the insulating film 12 on the surfaces of the metal particles 10.

  Each metal particle 10 in the vibration container 21 is covered with an insulating film 12. A case where the insulating film 12 is not formed on a part of the surface of the small number of metal particles 10 is also included in the present invention.

  After each metal particle 10 is covered with an insulating thin film and the conductive particles 1 are formed, the voltage application to the backing plate 31 and the introduction of the sputtering gas are stopped, and then the evacuation is stopped, and the vacuum chamber The atmosphere is introduced into 3 and the conductive particles 1 are taken out of the vacuum chamber 3 to complete the thin film forming step.

In the thin film formation process described above, before starting sputtering, it is preferable that the pressure V inside the vacuum chamber 3 is evacuated so that 9 × 10 ⁻⁵ <V <2 × 10 ⁻² . In particular, the pressure is more preferably in the range of 2 × 10 ⁻⁴ ≦ V ≦ 9 × 10 ⁻³ .

In the formation process of the insulating film 12, after the pressure V inside the vacuum chamber 3 reaches 9 × 10 ⁻⁵ Pa or less, sputtering is started while maintaining the state where the vacuum chamber 3 is not opened to the atmosphere. Impurities (mainly moisture) in the tank 3 are reduced, the adhesion and film density of the insulating film 12 are improved, and the insulating film 12 is removed from the surface 11 of the metal particle 10 by the pressure at the time of connection between the substrate and the connected member. Since the peeling does not occur, the connection resistance value may be increased by the remaining insulating film 12.

On the other hand, in the process of forming the insulating film 12, when sputtering is started by introducing a sputtering gas in a state where the pressure V inside the vacuum chamber 3 has decreased only to a pressure of 2 × 10 ⁻² Pa or more, the vacuum chamber 3 Due to the influence of the residual gas inside, the adhesiveness and film density of the insulating film 12 are reduced, and the insulating property of the conductive particles 1 is not maintained, so that it may not be possible to suppress the occurrence of a short circuit between the electrodes.

Therefore, in the thin film formation step, the pressure V inside the vacuum chamber 3 is in the range of 9 × 10 ⁻⁵ <V <2 × 10 ⁻² from the viewpoint of obtaining the insulating film 12 having appropriate adhesion and film density. It is preferable to start sputtering while maintaining the state in which the vacuum chamber 3 is not opened to the atmosphere after reaching the pressure of, particularly, the vacuum after reaching the pressure in the range of 2 × 10 ⁻⁴ ≦ V ≦ 9 × 10 ^−3. It is more preferable to start sputtering while maintaining the state where the tank 3 is not opened to the atmosphere.

  In the thin film forming process, vibration is generated with a predetermined amplitude and frequency by the vibration device 23, and a predetermined sputtering gas is introduced into the vacuum chamber 3 while continuously vibrating the vibration container 21. The flow rate of the sputtering gas can be adjusted so that the inside of the vacuum chamber 3 is maintained at a predetermined pressure.

In the above example, the vibration applied to the vibrating container 21 using the vibration device 23 is the vertical vibration. However, the vertical vibration is maintained while maintaining the state where the atmosphere does not enter the vacuum chamber 3 as necessary. In addition to the component, a vibration having a lateral vibration component may be applied to the vibration container 21. If the metal particle 10 moves in the vertical direction and rotates, only the vibration in the lateral direction may be used.
Further, the amplitude of the vibration device 23 may be adjusted to ± (0.5 or more and 10 or less) [mm], for example. Further, the frequency of the vibration device 23 may be adjusted to a value within a frequency range of 15 Hz to 65 Hz, for example, or the frequency may be changed within a set frequency range.

  As described above, the method for producing conductive particles according to the present embodiment forms the insulating film 12 on the surface 11 of the metal particle 10 containing a soft metal by sputtering while applying vibration. It is possible to suppress deformation of the metal particles 10 during the formation of 12, and to ensure insulation between the electrodes when connecting the substrate and the connected member, thereby maintaining high connection reliability.

[3. Anisotropic conductive adhesive]
Although the details of the anisotropic conductive adhesive according to the present embodiment will be described later, the anisotropic conductive adhesive is obtained by a method for producing an anisotropic conductive adhesive. The anisotropic conductive adhesive is composed of the conductive particles 1 shown in FIG. 1 and a binder material in which the conductive particles 1 are dispersed. In addition, since the particle | grains 1 for electrically conductive are as above-mentioned, description here is abbreviate | omitted.

  The form of the anisotropic conductive adhesive may be a film or a paste, and can be appropriately determined depending on the application.

  As the resin component having adhesiveness used for the anisotropic conductive adhesive, a known thermosetting resin that is usually used for anisotropic conductive adhesive can be used. Examples of such thermosetting resins include epoxy resins, phenol resins, melamine resins, urea resins (urea resins), unsaturated polyester resins, alkyd resins, polyurethane resins, thermosetting polyimides, acrylic resins, and the like. . In the anisotropic conductive adhesive, at least one kind of the thermosetting resin can be used as a binder material. In the anisotropic conductive adhesive, the type of the thermosetting resin used as the resin component is not particularly limited, and it is possible to use a resin other than the above depending on the application.

  In the anisotropic conductive adhesive, it is preferable to mix a curing agent that reacts with the resin component. In the anisotropic conductive adhesive, the type of the curing agent is not particularly limited, and for example, isocyanate, acid anhydride, amino resin, or the like can be used.

  In the anisotropic conductive adhesive, in order to accelerate the curing reaction between the resin component and the curing agent, a suitable coupling agent, catalyst, accelerator, and other components according to other applications may be used in combination.

  When the anisotropic conductive adhesive is in the form of a paste (anisotropic conductive paste), the viscosity or the like may be adjusted using a solvent in order to improve the coating property. In the anisotropic conductive paste, the type of the solvent is not particularly limited, and ester type, ketone type, alcohol type, hydrocarbon type, ether type, etc. can be used, and these may be used alone or in combination of two or more. You can also. In the anisotropic conductive paste, a leveling material, an antifoaming material, a dispersing material, etc. may be added as necessary.

  In the anisotropic conductive adhesive, the composition ratio between the conductive particles 1 and the resin component is set to an arbitrary composition range depending on the particle diameter and shape of the conductive particles 1 and the thermosetting resin used as the resin component. Can do. The composition range of the anisotropic conductive adhesive can be appropriately changed according to the object using the anisotropic conductive adhesive, the process to be used, and the like.

  As described above, since the anisotropic conductive adhesive according to the present embodiment includes the conductive particles 1 as described above, when the substrate and the connected member are connected, the opposing electrodes are connected to each other. Electrical connection and mechanical fixation can be performed (anisotropic conductive connection) so as to maintain a conductive state and maintain insulation between adjacent electrodes.

[4. Method for producing anisotropic conductive adhesive]
A method for producing an anisotropic conductive adhesive (hereinafter sometimes referred to as “adhesive production method”) is obtained by forming an insulating film 12 on the surface 11 of the metal particle 10 shown in FIG. This is a method for producing anisotropic conductive adhesive by dispersing particles 1 for use in a resin component.

  The adhesive production method is not particularly limited as long as the conductive particles 1 can be dispersed in the resin component, and a known dispersion method can be applied. Moreover, in an adhesive manufacturing method, an anisotropic conductive adhesive can be made into a film form or a paste form, and a dispersion | distribution method can be changed suitably according to the form.

  A film-like anisotropic conductive adhesive (anisotropic conductive film) is obtained by molding a mixture of conductive particles 1 dispersed in a resin component into a film shape. About the mixture obtained by carrying out similarly to the conductive film, it can obtain by adjusting a viscosity etc. using a solvent.

  The obtained anisotropic conductive film is used, for example, in a connection process in which a connected member such as an electronic component is mounted on a substrate.

  The connecting process will be described in more detail. Referring to FIG. 3A, when the connected member 61 is mounted on the substrate 51, there is an anisotropic effect between the electrode 52 of the substrate 51 and the electrode 62 of the connected member 61. The substrate 51 and the connected member 61 are placed in a direction in which the substrate 51 and the connected member 61 approach each other with a pad having elasticity such as rubber while sandwiching an anisotropic conductive film 71 in which a conductive conductive adhesive is formed into a film. When either one or both of the member 51 and the connected member 61 are pressurized while heating and the anisotropic conductive film 71 is heated, the resin component 72 of the anisotropic conductive film 71 softens and can flow by pressing. As shown in FIG. 3B, the resin component 72 located between the electrode 52 of the substrate 51 and the electrode 62 of the connected member 61 is pushed out, and the electrode 52 and the connected member 61 of the substrate 51 are extruded. Between the electrode 62 and The conductive particles 1 that have been formed are sandwiched between the electrode 52 and the electrode 62.

In FIG. 3B, reference numeral 74 indicates the sandwiched conductive particles, and reference numeral 73 indicates the conductive particles located outside the electrodes 52 and 62.
In FIG. 3B, one conductive particle 74 is located between the electrode 52 and the electrode 62, but a plurality of conductive particles 74 are located between the electrode 52 and the electrode 62. The case where it is pressed by the two electrodes 52 and 62 is also included. Further, the anisotropic conductive adhesive may be heated so as to flow before being pressed.

When the anisotropic conductive film 71 is further heated to a temperature equal to or higher than the melting point of the low melting point metal of the metal particles 10, the metal particles 10 in the conductive particles 1 are melted.
When the metal particles 10 in the conductive particles 1 dispersed in the resin component 72 of the anisotropic conductive film 71 are melted, the conductive particles 74 sandwiched and pressed between the electrode 52 and the electrode 62. Is pressed, the insulating film 12 is broken and the melt of the metal particles 10 is pushed into the resin component 72, and the melt is composed of the electrode 52 of the substrate 51 and the electrode 62 of the connected member 61. Contact with.

  At this time, since the electrodes 52 and 62 are pressed toward each other, the two electrodes 52 and 62 are in contact with each other directly or via a melt, and the anisotropic conductive film 71 is in that state. When the melt is cooled and the melt is solidified, the electrodes 52 and 62 are mechanically and electrically connected to each other by a metal layer formed by solidifying the melt. At this time, a conductive path is formed.

When the melt is solidified, the fluidized resin component 72 is also solidified, and the substrate 51 and the connected member 61 are mechanically connected by the solidified resin component 72.
Reference numeral 77 in FIG. 3C denotes a metal layer in which the melt is solidified, and reference numeral 75 denotes a solidified resin component.

  On the other hand, since the conductive particles 1 (73) located between the two electrodes 52 and 62 and not being pressed are not pressed, the insulating film 12 is not melted even if the metal particles 10 are melted. The metal particles 10 are held without being destroyed, and the melt of the metal particles 10 is not extruded into the resin component 72. When cooled, the solidified metal particles 10 return to the conductive particles 1 covered with the insulator 12, so that The insulation between the aligned electrodes is maintained. Therefore, by using the anisotropic conductive film 71, conductivity is generated in the vertical direction and anisotropy is maintained in the horizontal direction so that the insulating property is maintained. The connected member can be mounted without causing a short circuit. In particular, since the anisotropic conductive film 71 uses a solder alloy as the metal particles 10, the electrodes can be electrically and mechanically connected even when the heating temperature is low.

  The obtained anisotropic conductive paste is coated with an anisotropic conductive paste between the electrode portion of the substrate and the electrode portion of the connected member when mounting the connected member, Similarly, the connected member can be mounted without causing a short circuit even if the distance between the electrodes in the horizontal direction is narrow.

  Examples of the substrate include a printed wiring board, a glass substrate for LCD (liquid crystal display), a flexible printed circuit (FPC), and the like. Examples of the connected member include semiconductor elements such as IC (integrated circuit) and LSI (large-scale integration) and electronic components such as packages.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited thereto.

[Example 1]
<1. Preparation of conductive particles>
In Example 1, a metal oxide film was formed on the surface of the solder alloy particles by using the sputtering apparatus 4 provided with the vibration apparatus 23 shown in FIG. Moreover, in Example 1, the particle | grains of an Sn-3.0Ag-0.5Cu (wt%) composition whose average particle diameter is 5 micrometers are used for the particle | grains of a solder alloy, and a sputtering target material (sputtering target 32 in FIG. 2). For this, a silicon (Si) target was used.

  The solder alloy used in the present invention does not contain lead and contains 50 wt% or more of Sn and melts at a temperature of 220 ° C. or less. However, technically, an alloy containing Pb may be used for the metal particles. It is possible to electrically connect the electrode of the member to be connected and the electrode of the substrate.

Specifically, in Example 1, in the sputtering apparatus 4, a stainless steel container (vibration container 21 in FIG. 2) having an opening diameter of φ12 cm is placed on a vibration table, 50 g of solder alloy particles are placed in the stainless steel container, and sealed. Thereafter, exhaust was performed with a rotary pump and a cryopump until the internal pressure of the vacuum chamber 3 reached 2 × 10 ⁻⁴ Pa.

Next, in Example 1, the vibration device 23 generates a vibration having an amplitude of ± 2 mm and a vibration frequency of 30 Hz, and while continuously applying vibration to the stainless steel container, 90% argon (Ar) and oxygen (O ₂ ) are used as gases. ) 10% was introduced at a predetermined flow rate so that the pressure V inside the vacuum chamber 3 was maintained at 2 Pa, and the exhaust speed was adjusted.

  Next, in Example 1, a 300 W direct current was applied to the target, and a 50 nm silicon oxide (SiOx) insulating film was formed on the particle surface to obtain conductive particles.

(Particle deformation)
In Example 1, the conductive particles obtained by the sputtering process as described above were observed with 10 fields of view using a scanning electron microscope (SEM) manufactured by Keyence Corporation (VE-8800) at a magnification of 1000 times. The case where there were 10 or more deformations was defined as “with deformation”.

<2. Production of anisotropic conductive adhesive>
In Example 1, 20 parts by weight of naphthalene type bifunctional epoxy resin (manufactured by DIC, HP-4032D), 25 parts by weight of bisphenol F type epoxy resin (manufactured by DIC, EXA830CRP) as a thermosetting resin, master batch Type imidazole curing agent (Asahi Kasei E-Materials, HX-3721) 55 parts by weight, epoxy silane coupling agent (Shin-Etsu Chemical Co., KBM-403) 1 part by weight, fine particle silica (Nippon Aerosil Co., Ltd.) 2 parts by weight of R202) and 20 parts by weight of the obtained conductive particles were mixed uniformly with a rotating and rotating mixer to obtain an anisotropic conductive adhesive.

<3. Fabrication of mounting body>
In Example 1, using the obtained anisotropic conductive adhesive, IC (6.3 mm × 6.3 mm, t = 0.4 mm, 85 μm pitch, gold plating bump [50 μm × 50 μm, h = 15 μm]) And an FPC board (polyimide, t = 20 μm) on which nickel / gold plated copper wiring (t = 12 μm) is patterned.

  Specifically, in Example 1, the obtained anisotropic conductive adhesive was applied onto an FPC board, an IC was aligned and placed thereon, and then a predetermined bonding was performed using a constant heat tool. The IC and the FPC board were bonded under the conditions (200 ° C., 125 N / chip, 10 seconds) to obtain a mounted body.

<4. Measurement of connection resistance>
In Example 1, the initial resistance value and the resistance value after high temperature and high pressure test (85 ° C., 85% RH, 500 hours) (after aging) were measured using the obtained mounting body. Such measurement was performed by a four-terminal method using a digital multimeter (manufactured by Advantest Corporation, R6551).

<5. Measurement of the number of shorts>
In Example 1, using the obtained mounting body, the insulation resistance value (25 V applied) between adjacent bumps was measured (120 ch). In this measurement, when the insulation resistance value was less than 10 ⁻⁸ Ω, it was determined as a short circuit, and the number of channels was counted.

  The production conditions of the conductive particles obtained in Example 1 and the measurement results of the obtained mounting body are shown together in Table 1. Also in Example 2 to Example 9 described later, the production conditions and measurement results are summarized in Table 1 and Table 2 in the same manner as in Example 1. Further, in Comparative Examples 1 to 5 to be described later, the production conditions and measurement results are summarized in Table 2 in the same manner as in Example 1.

[Example 2 to Example 9]
In Examples 2 to 9, the conductive particles were prepared in the same manner as in Example 1 except that the production conditions of any of the conductive particles of Example 1 were changed as shown in Tables 1 and 2. An anisotropic conductive adhesive was produced from the produced particles. Moreover, in Example 2-9, the mounted body was produced using the obtained anisotropic conductive adhesive, and the connection reliability of the mounted body and the number of occurrence of short circuits were evaluated.

[Comparative Examples 1 to 5]
In Comparative Examples 1 to 5, except that the production conditions for any of the conductive particles of Example 1 were changed as shown in Table 2, conductive particles were produced in the same manner as in Example 1, An anisotropic conductive adhesive was prepared from the obtained particles. Moreover, in Comparative Examples 1 to 5, a mounted body was produced using the obtained anisotropic conductive adhesive, and the connection reliability of the mounted body and the number of occurrence of short circuits were evaluated.

  In Comparative Example 1, as shown in Table 2, as a result of using an anisotropic conductive adhesive containing untreated solder alloy particles, a short circuit occurred in the mounting body. On the other hand, in Example 1 to Example 9, as shown in Tables 1 and 2, the anisotropic conductive adhesion including the solder alloy particles on which an insulating film (metal oxide sputter layer) was formed by performing the sputtering process. As a result of using the agent, no short circuit occurred in the mounting body, and the initial resistance value and the resistance value after aging were low.

  Therefore, in Examples 1 to 9, it was found that a highly reliable mounting body (connection structure) can be obtained by forming an insulating film on the solder alloy particles.

  In Comparative Example 2, as shown in Table 2, as a result of forming the insulating film (sputter layer) with a thickness of 2 nm, a short circuit occurred in the mounting body. In Comparative Example 3, as shown in Table 2, the insulating film As a result of forming the film thickness to 500 nm, the connection resistance value increased in the mounted body. On the other hand, in Examples 1 to 4, Example 8, and Example 9, as shown in Tables 1 and 2, as a result of forming the film thickness of the insulating film to 5 nm or more and 480 nm or less, occurrence of short circuit in the mounting body The initial resistance value and the resistance value after aging were low.

  Therefore, in Examples 1 to 4, Example 8, and Example 9, it was found that a highly reliable mounting body can be obtained by forming at least the thickness of the insulating film to 5 nm or more and 480 nm or less. .

In Comparative Example 4, as shown in Table 2, as a result of film formation with a vacuum degree before sputtering treatment of 9 × 10 ⁻⁵ Pa, the connection resistance value increased in the mounted body. As shown, as a result of forming the insulating film by sputtering with a vacuum degree before sputtering treatment of 2 × 10 ⁻² Pa, a short circuit occurred in the mounting body. On the other hand, in Examples 1 to 4, Example 8, and Example 9, as shown in Table 1 and Table 2, the degree of vacuum before the sputtering treatment is 2 × 10 ⁻⁴ Pa or more and 9 × 10 ⁻³ Pa or less. As a result of film formation, no short circuit occurred in the mounted body, and the initial resistance value and the resistance value after aging were low.

When an insulating film is formed by sputtering in a state where the degree of vacuum before the sputtering treatment is lower than 2 × 10 ⁻⁴ Pa, for example, 9 × 10 ⁻⁵ Pa as in Comparative Example 4, the connection resistance value increases. End up. This is because when the pressure inside the vacuum chamber 3 is low, impurities (mainly moisture) inside the vacuum chamber 3 are reduced, the adhesion of the insulating film and the film density are improved, and the insulating film becomes particles by the pressure at the time of connection. This is thought to be due to insufficient peeling from the surface.

On the other hand, if the degree of vacuum before the sputtering treatment is higher than 9 × 10 ⁻³ Pa, for example, 2 × 10 ⁻² Pa as in Comparative Example 5, the occurrence of short circuit cannot be prevented. This is presumably because the pressure inside the vacuum chamber 3 is too high, and the adhesiveness and film density of the insulating film are reduced due to the residual impurities inside the vacuum chamber 3.

Therefore, in Examples 1 to 4, Example 8, and Example 9, at least the internal pressure of the vacuum chamber 3 before the sputtering treatment is set to 2 × 10 ⁻⁴ Pa or more and 9 × 10 ⁻³ Pa or less. It has been found that an insulating film that can be applied to a mounting body and can be made into a highly reliable mounting body is obtained.

  In Examples 1 to 9, the solder alloy particles on which the insulating film after the sputtering treatment was formed were observed using SEM, and as a result, it was found that no deformation of the particles was observed.

  From Example 1 and Examples 5 to 7, the metal species of the target for forming the insulating film is any one of aluminum (Al), titanium (Ti), and niobium (Nb) in addition to silicon. In addition, it has been found that an insulating film that can be applied to a mounting body and can be a highly reliable mounting body is obtained.

DESCRIPTION OF SYMBOLS 1 Conductive particle, 3 Vacuum chamber, 4 Sputtering device, 10 Metal particle, 12 Insulating film, 21 Vibrating vessel, 23 Vibrating device, 31 Backing plate, 32 Sputtering target, 51 Substrate, 52 Substrate electrode, 61 Connected member, 62 Electrode of connected member, D average particle diameter, T film thickness

Claims (16)

In a method for producing conductive particles, a sputtering gas is introduced into a vacuum chamber in which a sputtering target is arranged, and the sputtering target is sputtered to form a thin film on the surface of the low melting point metal particles to form conductive particles. There,
A plurality of the metal particles are disposed in a vibrating container, and the target is sputtered while vibrating the vibrating container to vibrate the metal particles to form an insulating film on the surface of the metal particles, and the metal particles are formed on the insulating film. A method for producing conductive particles, which forms the conductive particles covered with. 2. The conductive particle according to claim 1, wherein the pressure in the vacuum chamber is set to a pressure greater than 9 × 10 ⁻⁵ Pa and less than 2 × 10 ⁻² Pa before starting the formation of the insulating film. Manufacturing method.   The method for producing conductive particles according to claim 1, wherein a solder alloy is used for the metal particles.   The method for producing conductive particles according to any one of claims 1 to 3, wherein the thickness of the insulating film is set to a value in a range thicker than 2 nm and thinner than 500 nm.   5. The insulating film according to claim 1, wherein the insulating film is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. The manufacturing method of particle | grains for electroconductivity.   The method for producing conductive particles according to claim 1, wherein the sputtering target made of metal is used, and oxygen gas is contained in the sputtering gas. An anisotropic conductive adhesive having a resin component having adhesiveness and a plurality of conductive particles dispersed in the resin component,
The conductive particles include metal particles made of a low melting point metal,
An insulating film covering the metal particles,
An anisotropic conductive adhesive, wherein the insulating film is formed on the surface of the metal particles by sputtering while applying vibration in an atmosphere containing oxygen.   The anisotropic conductive adhesive according to claim 7, wherein the low melting point metal is a solder alloy.   The anisotropic conductive adhesive according to claim 7 or 8, wherein the thickness of the insulating film is set to a value in a range thicker than 2 nm and thinner than 500 nm.   10. The insulating film according to claim 7, wherein the insulating film is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. An anisotropic conductive adhesive.   The anisotropic conductive adhesive according to any one of claims 7 to 10, wherein the average particle diameter of the metal particles is set to a value in a range of 1 µm to 20 µm. An arrangement step of arranging an anisotropic conductive adhesive containing a plurality of conductive particles in a resin component having adhesiveness between an electrode of a substrate and an electrode of a connected member;
A heating and pressing step of pressing the substrate and the connected member in a direction approaching each other while heating the anisotropic conductive adhesive;
A cooling step for cooling the heated anisotropic conductive adhesive;
Have
A component mounting method for mechanically fixing the substrate and the connected member by the cooled resin component,
For the conductive particles, use is made of particles in which the surface of metal particles made of a low melting point metal is covered with an insulating film,
In the heating and pressing step, the anisotropic conductive adhesive is heated to melt the metal particles, and is positioned between the electrode of the substrate and the electrode of the connected member and pressed. The insulating film of particles is destroyed, and the melt of the pressed metal particles of the conductive particles is discharged into the resin component, and the melt is transferred to the electrode of the substrate and the electrode of the connected member. Contact,
In the cooling step, the anisotropic conductive adhesive is cooled to solidify the melt that contacts the electrode of the substrate and the electrode of the connected member, and the melt of the substrate causes the melt of the substrate to be solidified. A component mounting method for electrically connecting an electrode and the electrode of the connected member.   The component mounting method according to claim 12, wherein an alloy that melts at a temperature of 220 ° C. or lower is used for the low melting point metal.   The component mounting method according to claim 13, wherein an alloy that melts at a temperature of 150 ° C. or higher is used as the low melting point metal.   The component mounting method according to claim 14, wherein the low melting point metal is a solder alloy that does not contain lead and contains 50% or more of tin. The component mounting method according to claim 12, wherein an oxide film is used as the insulating film.

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