JP2006210196A - Metal particle composite structure and its manufacturing method, and anisotropic conductive membrane using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal particle composite structure by which an anisotropic conductive membranes or the like can be easily manufactured, and its effective manufacturing method, and the anisotropic conductive membranes which are manufactured by using the metal particle composite structure, which are homogeneous all over the whole face, and which have anisotropic conductive characteristics. <P>SOLUTION: The metal particle composite structure 1 has a shape in which liquid droplets are face-contacted with the surface of the base material 2, and the metal particles 3 in which the particle diameter in the surface direction is 0.1-20 μm are separately distributed on the surface of the base material 2 so that they are not connected to each other. In this manufacturing method, a coating film containing metal fine particles of the primary particle diameter 200 nm or less on the surface of the base material 2, and this is heat-treated at temperatures of 200 degrees or more and less than the melting point of the metal, and the metal fine particles are coagulated in liquid droplet state, and the metal particles 3 are formed. As for the anisotropic conductive membranes, the coating solution containing an insulating binder is applied on the base material 2 and solidified to form the film and distribution state on the base material 2 of numerous metal particles 3 is fixed in the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal particle composite structure that can be used as, for example, an anisotropic conductive film, an efficient manufacturing method thereof, and an anisotropic conductive film using the metal particle composite structure.

  For example, a semiconductor package is mounted on a mounting electrode provided in a conductor circuit such as a flexible printed circuit board (FPC) by so-called flip chip bonding, or two or more FPC conductor circuits are connected to each other. In the field of electronics mounting in which connections are made via electrodes provided in the connection portion, high-density mounting is progressing, and the pitch between adjacent electrodes tends to become narrower.

  As one of mounting methods in electronics mounting, there is a method using a film-like anisotropic conductive film having thermal adhesiveness (see, for example, Patent Documents 1 and 2). Anisotropic conductive film usually has a powdery conductive component, an insulating property that insulates between the individual conductive components, a function of forming a film while holding the conductive component (film forming property), and further if necessary In a film made of a binder such as a thermoplastic resin or a curable resin, which also has a function (adhesiveness) as an adhesive for thermal bonding (adhesive layer may be laminated on the film) Can be separated by function).

  The anisotropic conductive film having the above structure forms a coating solution by blending a conductive component and a solid binder together with a solvent that dissolves the binder in a predetermined ratio, and this coating solution is applied onto a base. In addition to forming a coating film, the film is dried and solidified by removing the solvent, and then peeled off from the base. Further, the anisotropic conductive film may be formed by, for example, applying a coating solution in which a solvent is omitted by using a liquid curable resin or the like as a binder on a base, and then solidifying the curable resin by semi-curing. Can be manufactured.

  In an anisotropic conductive film, in order to prevent short-circuiting between adjacent electrodes when thermally bonded, the conductive component of the conductive component is increased so that the conductive resistance in the surface direction of the film (referred to as “insulation resistance”) is increased. Adjust the distribution density. When heat bonding is performed with the anisotropic conductive film sandwiched between the FPC and the semiconductor package to be conductively connected or between the FPCs, the anisotropic conductive film is heated and pressed during heat bonding. By compressing in the direction, the distribution density of the conductive component in the thickness direction increases, and the conductive components come close to or in contact with each other to form a conductive network. As a result, the conductive resistance in the thickness direction (referred to as “connection resistance”) ) Becomes lower.

  However, at this time, the distribution density of the conductive component in the plane direction of the anisotropic conductive film does not increase. That is, the surface direction maintains an initial state where the insulation resistance is high and the conductivity is low. Therefore, the insulation resistance in the surface direction of the anisotropic conductive film maintains the insulation between the adjacent electrodes to prevent short circuit, while the connection resistance in the thickness direction causes a large number of electrodes-bumps, and between the electrodes-electrodes. Conductive connections can be made at once and independently of each other. At the same time, since the FPC and the semiconductor package or between the FPCs can be fixed by thermal bonding via an anisotropic conductive film, the mounting operation is easy.

  As the conductive component contained in the anisotropic conductive film, for example, Ni powder having a particle size of about several μm to several tens of μm, and the shape is granular, spherical, flaky (flaky, flaky), etc. In addition, various metal powders such as resin powders whose surfaces are gold-plated have been put into practical use. However, as described above, the conventional anisotropic conductive film is formed by applying a coating liquid containing a conductive component on a base and drying, solidifying, or semi-curing, and then peeling off from the base. Since it is manufactured, there is a problem that it is difficult to obtain uniform and good anisotropic conductive characteristics over the entire surface of the anisotropic conductive film.

  That is, as described above, a conductive component such as a metal powder having a small particle size usually contains a resin component as a binder, so it is not easy to uniformly disperse in a relatively high viscosity coating solution, If the dispersion of the conductive component is insufficient, an agglomeration of the conductive component occurs in the manufactured anisotropic conductive film, and insulation between adjacent electrodes cannot be maintained, resulting in poor insulation or aggregation. There is a possibility that the distribution density of the conductive component is insufficient in a portion other than the lump, and the conductive connection between the electrode and the bump and between the electrode and the electrode cannot be reliably established.

  In view of this, it has been proposed to manufacture an anisotropic conductive film using a chain metal powder that has a large specific surface area and is easily dispersed uniformly in a coating solution as a conductive component (see Patent Document 3). Further, in Patent Document 3, in order to further improve the anisotropic conductive characteristics of the anisotropic conductive film, at least a part of the chain metal powder is formed of a magnetic material such as Ni, By spraying on the base to which the magnetic field is applied in the intersecting direction and orienting it in the direction of the magnetic field, a coating solution containing a binder is applied and solidified to form a film made of a binder. It also describes that an anisotropic conductive film is produced by fixing the distribution state of the metal powder on the substrate in the film.

  According to said manufacturing method, many chain-shaped metal powder contained in an anisotropic electrically conductive film can be orientated in the thickness direction of a film | membrane. Therefore, the anisotropic conductive characteristics of the anisotropic conductive film can be improved. In addition, among the many metal powders dispersed on the base to which a magnetic field is applied, the many metal powders in the first layer that are in direct contact with the base surface are all magnetized to the same polarity, so that they are adjacent to each other. Due to the magnetic repulsive force between the matching objects, they are distributed on the base in a state where they are maintained at approximately equal intervals.

Therefore, by further spreading the metal powder on the metal powder of the first layer, a linear shape is formed along the direction of the magnetic field further upward from the upper end of the metal powder of the first layer. Alternatively, a conductive network made of a plurality of metal powders formed in a chained manner can be distributed almost uniformly in the surface direction of the base without causing non-uniform distribution or aggregates.
JP-A-6-102523 (column 0009, column 0010, FIG. 2) JP-A-8-115617 (Columns 0003 to 0006, FIG. 1) JP 2003-331951 A (Claims 1, 16, columns 0020, columns 0039 to 0040)

  However, as a result of investigation by the inventors, in order to manufacture the anisotropic conductive film by the method described in Patent Document 3, a magnetic field is applied in a direction intersecting the base surface, and as described above, a chain shape is formed. In order to uniformly distribute the metal powder on the base surface, it has become clear that there is a problem that the manufacturing cost is high because a magnet is required.

  An object of the present invention is to provide a novel metal particle capable of manufacturing an anisotropic conductive film having uniform and good anisotropic conductive characteristics over the entire surface thereof relatively easily and inexpensively. An object of the present invention is to provide a composite structure and an efficient manufacturing method thereof. Another object of the present invention is to provide an anisotropic conductive film which is manufactured using the above metal particle composite structure and has uniform and good anisotropic conductive characteristics over the entire surface. is there.

  The invention according to claim 1 includes a base material and a large number of metal particles distributed on the surface of the base material so as not to contact each other, and each of the metal particles includes a droplet. The metal particle composite structure is characterized in that each of the metal particles has a shape in surface contact with the surface of the substrate, and the particle size in the surface direction of the substrate is 0.1 to 20 μm.

  The invention according to claim 2 is a method for producing the metal particle composite structure according to claim 1, wherein a dispersion containing fine metal particles having a primary particle diameter of 200 nm or less is applied to the surface of the substrate and dried. The step of forming a coating film and the formed coating film are heat-treated at a temperature of 200 ° C. or higher and lower than the melting point of the metal forming the metal fine particles, and a large number of metal fine particles dispersed in the coating film are dropped. The metal particle composite structure manufacturing method is characterized in that a large number of metal particles are generated on the surface of the base material by being agglomerated in a state of being separated and distributed so as not to contact each other.

  The invention according to claim 3 is to apply a coating liquid containing an insulating binder on the base material of the metal particle composite structure according to claim 1 and solidify to form a film made of the binder. An anisotropic conductive film characterized in that a distribution state of a large number of metal particles on a substrate is fixed in the film.

  In the metal particle composite structure according to the first aspect of the present invention, many of the metal particles are all fine particles having a particle size of 0.1 to 20 μm in the surface direction of the substrate, and droplets are formed on the substrate. In addition to being formed in a stable shape in surface contact with the surface, it is formed on the surface of the base material so as not to contact each other in advance and in a substantially evenly distributed state. Therefore, an anisotropic conductive film having uniform and good anisotropic conductive characteristics over the entire surface can be easily and inexpensively manufactured without requiring a magnet or the like.

  According to the invention described in claim 2, a coating liquid is formed by applying a dispersion containing fine metal fine particles having a primary particle diameter of 200 nm or less, which is the basis of the metal particles, to the surface of the substrate. Then, heat treatment is performed at a temperature of 200 ° C. or higher and lower than the melting point of the metal forming the metal fine particles, and a large number of metal fine particles dispersed in the coating film are simply aggregated in droplets. The metal particle composite structure of the invention can be produced efficiently. This is because when a heat treatment in the above temperature range is performed, a large number of fine metal particles in the coating film behave like a liquid due to the so-called Kubo effect and agglomerate into a plurality of droplets one by one. This is based on the knowledge that metal particles having a shape in which droplets adhere to the surface of the substrate are formed.

  Moreover, according to the invention of claim 2, by adjusting conditions such as the particle size of the metal fine particles as the starting material, the type and surface state of the base material, the temperature and time of the heat treatment, The particle diameter in the surface direction of the substrate, the distance between adjacent metal particles on the substrate surface, and the like can be adjusted. Therefore, there also exists an advantage that the anisotropic conductive characteristic etc. of the anisotropic conductive film formed using the manufactured metal particle composite structure can be adjusted easily.

  Furthermore, since the anisotropic conductive film of the invention of claim 3 is formed using the metal particle composite structure of the invention of claim 1, it is uniform and good anisotropic conductive over the entire surface. It has characteristics.

<Metal particle composite structure and manufacturing method thereof>
FIG. 1 is an enlarged scanning electron micrograph of a part of the metal particle composite structure 1 manufactured in Example 1 of the present invention, and FIG. 2 is a part of the metal particle composite structure 1 of Example 1 described above. Further enlarged scanning electron micrograph, FIG. 3 is a scanning type showing a state in which one metal particle 3 formed on the substrate 2 in the metal particle composite structure 1 of Example 1 is viewed from the side. It is an electron micrograph.

  1 and 2, a metal particle composite structure 1 includes a base material 2 and a large number of metal particles 3 distributed on the surface of the base material 2 so as not to contact each other. I have. Referring to FIG. 3, each metal particle 3 is formed in a shape in which a droplet is brought into surface contact with the surface 20 of the substrate 2.

  The particle size of the metal particles 3 in the surface direction of the substrate 2 is limited to a range of 0.1 to 20 μm. It is substantially difficult to form the metal particles 3 having a particle size of less than 0.1 μm in a state of being uniformly distributed on the surface of the substrate 2. Moreover, even if it can form, each metal particle 3 will become a thing physically or chemically unstable. In particular, the metal particles 3 are easily deformed at a temperature lower than the melting point of the metal or move on the base material 2 to cause a problem that a good distribution state cannot be maintained (also described above). Takubo effect).

  On the other hand, when the particle diameter exceeds 20 μm, when the anisotropic conductive film is formed using the metal particle composite structure 1 of the present invention, the insulation resistance in the surface direction of the anisotropic conductive film becomes low, There is a problem that insulation between adjacent electrodes cannot be maintained and insulation failure occurs. In consideration of more reliably preventing these problems from occurring and forming an anisotropic conductive film having good anisotropic conductive characteristics, etc., the particles of the metal particles 3 in the surface direction of the substrate 2 Even in the above range, the diameter is particularly preferably 2 to 10 μm.

  In the present invention, the particle size of the metal particles 3 in the surface direction of the substrate 2 is defined by the average value of the particle sizes obtained by the following method. That is, a scanning electron micrograph of the surface of the base material 2 on which the metal particles 3 are distributed is taken at an arbitrary plurality of locations on the base material 2, and the actual size of the photograph taken is 100 × 125 μm. For all the metal particles 3 copied in the rectangular region, the area is obtained by image analysis. And the diameter of the virtual circle which has an area which corresponds to the calculated | required area is calculated, it is set as the particle size of the surface direction of the base material 2 of each metal particle 3, and it calculates | requires of all the metal particles 3 calculated | required in that way. The average value of the particle diameters is calculated to be the particle diameter in the surface direction of the base material 2 of the metal particles 3 in the metal particle composite structure 1.

  As the metal that forms the metal particles 3, various metals that satisfy the functions required of the metal particles 3 can be used depending on the use of the metal particle composite structure 1. For example, when forming an anisotropic conductive film using the metal particle composite structure 1 of the present invention, the metal particles 3 are made of platinum, gold, silver, copper, palladium, ruthenium, rhodium, iridium, and osmium. What is necessary is just to form with the metal excellent in electroconductivity, such as the at least 1 sort (s) of metal chosen from the group, or its alloy.

  Moreover, the base material 2 can be formed of various materials that satisfy the functions required of the base material 2 in the usage depending on the usage of the metal particle composite structure 1. Further, when the metal particle composite structure 1 is manufactured by the manufacturing method of the present invention described below, the base material 2 has a metal having a predetermined particle size and distribution state by aggregation of a large number of metal fine particles by heat treatment. It is also required that the particles 3 can be formed. It is also required to have heat resistance that can withstand the heat treatment temperature. The substrate 2 should be selected in consideration of the balance of these conditions.

  For example, when forming the anisotropic conductive film using the metal particle composite structure 1 of the present invention, the base material 2 is finally peeled off from the anisotropic conductive film as a product. There is no function required for the substrate 2 in use. Therefore, the base material 2 has characteristics that can form metal particles 3 having a predetermined particle size and distribution state exclusively by agglomeration of a large number of metal fine particles by heat treatment, and has heat resistance that can withstand the temperature of heat treatment. Is required. That is, it is not deformed by the heat treatment and has an appropriate affinity for the metal fine particles that behave like a liquid during the heat treatment, specifically, the material forming the base material 2, the surface state of the base material 2, etc. It is required that the affinity for the specific metal forming the metal fine particles defined by the above is not too high or too low.

  When the affinity of the base material 2 to the metal fine particles is too high, the metal fine particles do not aggregate in the form of droplets during the heat treatment and spread on the surface of the base material 2 to form a metal particle 3. There is a risk that it will not be. Moreover, when the affinity of the base material 2 for the metal fine particles is too low, the contact area of the formed metal particles 3 that are in surface contact with the surface of the base material 2 is reduced. For this reason, the metal particles 3 easily move on the base due to the pressure of the flow applied when the coating liquid is applied to the surface of the substrate 2, and the distribution thereof is biased, so that the anisotropic anisotropic conductive characteristics are uniform. It becomes impossible to live by forming a conductive film. Examples of the base material 2 that can form an anisotropic conductive film having uniform and good anisotropic conductive characteristics in combination with the above-described metals having excellent electrical conductivity include, for example, blue plate glass glass and alkali-free glass. And various ceramics such as alumina and silica.

  In the metal particle composite structure 1 of the present invention, as described above, a dispersion containing metal fine particles having a primary particle diameter of 200 nm or less is applied to the surface of a substrate and dried to form a coating film, Heat treatment at a temperature of 200 ° C. or higher and lower than the melting point of the metal forming the metal fine particles, and agglomerate a large number of metal fine particles dispersed in the coating film in the form of droplets, whereby It can be manufactured by the manufacturing method of the present invention in which a large number of metal particles are generated in a state of being distributed apart so as not to contact. According to this manufacturing method, the metal particle composite structure 1 of the present invention can be efficiently manufactured.

  The primary particle diameter of the metal fine particle that is the basis of the metal particle 3 is limited to 200 nm or less. The metal fine particle having a large particle diameter exceeding 200 nm behaves like a liquid even when heated to the above temperature range. This is because they cannot be aggregated into droplets. The lower limit of the primary particle diameter of the metal fine particles is not particularly limited, but is preferably 1 nm or more for practical use. Further, considering that a large number of metal fine particles are aggregated in the form of droplets as well as possible to form good metal particles 3 having a uniform particle size and distribution state, the primary particle size of the metal fine particles is Even within the above range, 1 to 50 nm is particularly preferable. In the present invention, the primary particle diameter of the metal fine particles is defined by the peak value of the particle size distribution measured using a particle size distribution measuring apparatus applying the laser Doppler method.

  The metal fine particles are preferably produced, for example, by reducing and precipitating metal ions in water. Specifically, for example, in water, a water-soluble metal compound that is a source of metal ions and, if necessary, a dispersant are dissolved, and a reducing agent is added, preferably under stirring, Metal fine particles are produced by a reduction reaction of metal ions for a certain period of time. The metal fine particles produced by such a liquid phase reduction method are characterized by having a spherical or granular shape, a sharp particle size distribution, and a small primary particle size.

The water-soluble metal compound that is a source of metal ions is not limited to this. For example, in the case of platinum, dinitrodiammine platinum (II) [Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ] or Hexachloroplatinum (IV) acid hexahydrate [H ₂ (PtCl ₆ ) · 6H ₂ O] and the like. In the case of gold, tetrachloroauric (III) acid tetrahydrate [HAuCl ₄ · 4H ₂ In the case of silver, silver nitrate (I) [AgNO ₃ ], silver methanesulfonate [CH ₃ SO ₃ Ag] and the like can be mentioned.

Examples of copper include copper nitrate (II) [Cu (NO ₃ ) ₂ ] and copper (II) sulfate pentahydrate [CuSO ₄ .5H ₂ O]. (II) Nitric acid solution [Pd (NO ₂ ) ₂ / H ₂ O], palladium (II) chloride solution [PdCl ₂ ] and the like. In the case of ruthenium, ruthenium (III) nitrate solution [Ru (NO ₃ ) ₃ ] and the like. Further, in the case of rhodium, rhodium (III) chloride solution [RhCl ₃ .3H ₂ O] and the like can be mentioned. In the case of iridium, hexachloroiridium (III) hexahydrate [2 (IrCl ₆ ) · 6H ₂ O] and the like, and in the case of osmium, hexachloroosmate (IV) ammonium [(NH ₄ ) ₂ OsCl ₅ ] and the like.

  As the reducing agent, any of various reducing agents that can be precipitated as metal fine particles by reducing metal ions in a liquid phase reaction system can be used. Examples of the reducing agent include sodium borohydride, sodium hypophosphite, hydrazine, and transition metal element ions (trivalent titanium ions, divalent cobalt ions, and the like). However, in order to reduce the primary particle size of the metal fine particles to be precipitated as much as possible, it is effective to reduce the reduction and precipitation rate of metal ions, and to reduce the reduction and precipitation rate, the reduction power is as low as possible. It is preferable to select and use a weak reducing agent.

  Examples of the reducing agent having a weak reducing power include alcohols such as methanol, ethanol and isopropyl alcohol, ascorbic acid, and the like, as well as ethylene glycol, glutathione, and organic acids (citric acid, malic acid, tartaric acid, etc.). , Reducing sugars (glucose, galactose, mannose, fructose, sucrose, maltose, raffinose, stachyose, etc.) and sugar alcohols (sorbitol, etc.). Among them, reducing sugars and sugars as derivatives thereof Alcohols are preferred.

  As the dispersant, any of various dispersants having good solubility in water can be used. In particular, a polymer dispersant having a molecular weight of about 30,000 or less is preferably used. In addition, as a dispersant, in consideration of preventing deterioration of electrodes and bumps connected using an anisotropic conductive film, electronic components arranged in the vicinity thereof, sulfur, phosphorus, boron and halogen atoms Organic compounds containing no are preferred. Suitable dispersants that satisfy these conditions include, for example, amine-based polymer dispersants such as polyethyleneimine and polyvinylpyrrolidone, carbonization having a carboxylic acid group in the molecule such as polyacrylic acid and carboxymethylcellulose. Examples thereof include a hydrogen-based polymer dispersant, poval (polyvinyl alcohol), and a polymer dispersant such as a copolymer having a polyethyleneimine moiety and a polyethylene oxide moiety in one molecule.

  In order to adjust the primary particle diameter of the metal fine particles to the above range, the metal compound, the dispersant, the kind of the reducing agent and the blending ratio are adjusted, and when the metal compound is subjected to a reduction reaction, the stirring speed and temperature are adjusted. The time, pH, etc. may be adjusted.

  In the production method of the present invention, the reaction solution after depositing the metal fine particles by the reduction reaction is used as it is as a dispersion for coating the surface of the substrate 2 to form a coating film. You can also. Further, the produced metal fine particles can be dispersed in a suitable solvent to prepare a new dispersion, which can be used for forming a coating film. Examples of the solvent for preparing a new dispersion include water or a mixed solvent of water and a water-soluble organic solvent.

  Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, n-propanol, 2-propanol, 2-ethoxyethanol, glycerin, dipropylene glycol, ethylene glycol, and polyethylene glycol; ketones such as acetone and methyl ethyl ketone; Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene Glico Monoethyl ether, glycol ethers such as tripropylene glycol monomethyl ether; 2-pyrrolidone, water-soluble nitrogen-containing organic compounds such as N- methyl pyrrolidone; and ethyl acetate. The water-soluble organic solvent can be used alone or in combination of two or more.

  In the present invention, water or a water-soluble organic solvent is used as a dispersion medium so as to have the optimum physical properties for a coating method for forming a coating film using the dispersion, and the blending ratio of the water-soluble organic solvent When using two or more types of water-soluble organic solvents in combination, the combination thereof is appropriately selected. For example, in the formation of a coating film by a spin coating method or a spray method, the dispersion liquid is required to have a viscosity as low as possible. Conversely, in the formation of a coating film by a dip coating method, the dispersion liquid is appropriate. It is required to have a viscosity.

  Therefore, in order to satisfy these physical properties, the mixing ratio of water and the water-soluble organic solvent, the type of the water-soluble organic solvent, the combination in the case of using two or more water-soluble organic solvents in combination, and the like are selected. . At the same time, the primary particle size and blending ratio of the metal fine particles, the molecular weight and blending ratio of the dispersant, the type of the dispersant, and the like are also selected.

  As in the conventional case, the dispersion liquid is made into a powder form through steps such as separation, washing, drying, and crushing, and then dispersed in a dispersion medium with an additional dispersant as necessary. Can be manufactured. However, the dispersion liquid undergoes a process of completely separating the precipitated metal fine particles from the liquid phase reaction system after reducing the metal ions and precipitating the metal fine particles in water as described above. It is more preferable to produce without.

  Specifically, the liquid phase reaction system after depositing the metal fine particles is centrifuged to remove impurities lighter than the metal fine particles, or washed with water to remove water-soluble impurities, For example, use a rotary evaporator, heat, or centrifuge again to remove the supernatant liquid, concentrate to a predetermined concentration, and then add a predetermined amount of water and / or water-soluble organic solvent This produces a dispersion. At this time, since the dispersant used for the production of the metal fine particles is contained in the reaction system, it is usually not necessary, but in some cases, a dispersant similar to the above may be newly added.

  The dispersion produced through the above steps prevents the formation of coarse and irregular particles due to the aggregation of the metal fine particles, and the metal fine particles formed by the liquid phase reduction method have a spherical or granular shape. In addition, the characteristics that the particle size distribution is sharp and the primary particle size is small can be maintained as they are. Therefore, if the coating film is formed using the above dispersion liquid, the metal fine particles in the coating film can be uniformly aggregated by the subsequent heat treatment. The metal particles 3 can be uniformly distributed.

  In the production method of the present invention, the coating film formed on the surface of the substrate 2 is heat-treated at a temperature of 200 ° C. or higher and lower than the melting point of the metal forming the metal fine particles, as described above. A large number of fine metal particles dispersed therein are aggregated in the form of droplets, thereby generating a large number of metal particles on the surface of the substrate. The temperature of the heat treatment is limited to 200 ° C. or more. If the temperature is lower than 200 ° C., a large number of metal fine particles cannot be smoothly moved on the surface of the base material to be aggregated in droplets. This is because a discontinuous film in which a large number of metal fine particles are softened and integrated on the surface is formed on the surface.

  Further, the temperature of the heat treatment is limited to less than the melting point of the metal forming the metal fine particles, when the heat treatment is performed at a temperature equal to or higher than the melting point, a large number of metal fine particles cannot be smoothly aggregated, This is because the metal particles 3 in the form of clean droplets cannot be uniformly distributed on the surface of the substrate 2. As the heat treatment temperature is increased even within the above range and as the heat treatment time is increased, a larger number of metal fine particles are aggregated into one metal particle. As the particle size in the surface direction of the substrate 2 increases, the number of metal particles 3 formed per unit area tends to decrease. Therefore, according to the particle size and distribution state of the metal particles 3 required for the metal particle composite structure 1 to be manufactured, the temperature of the heat treatment is appropriately adjusted within the above range and the time within the arbitrary range. It is preferable to do this.

  Moreover, the particle diameter and distribution state of the metal particles 3 can also be adjusted by adjusting the thickness of the coating film formed on the surface of the substrate 2 (that is, the amount of metal fine particles). Moreover, in order to adjust the thickness of the coating film, the concentration of the metal fine particles in the dispersion liquid is adjusted, the amount and type of the dispersing agent are changed, the viscosity of the dispersion liquid is adjusted, What is necessary is just to change the coating method to the base-material surface.

  The metal particle composite structure 1 of the present invention manufactured by the above manufacturing method is distributed on the surface of the base material 2 so that the fine metal particles 3 having a uniform shape and particle size are not in contact with each other. Since it has an unprecedented special structure, it can be expected to develop various applications such as a planar contact substrate for membrane switch panels. Among these, in particular, the metal particle composite structure 1 can be suitably used as a starting material for the anisotropic conductive film described below.

<Anisotropic conductive film>
The anisotropic conductive film of the present invention is formed by applying a coating solution containing an insulating binder onto the base material 2 of the metal particle composite structure 1 and solidifying it to form a film made of the binder. After the distribution state of the metal particles 3 on the base material 2 is fixed in the film, the film is peeled off from the base material 2 together with the fixed many metal particles 3.

  As described above, the binder that forms the film includes an insulating property that insulates between the individual metal particles 3, a film formability that forms the film while holding the metal particles 3, and further, if necessary. Examples thereof include thermoplastic resins and curable resins that also have adhesiveness as an adhesive for heat bonding. Particularly preferably, an acrylic resin, an epoxy resin, a fluorine resin, a phenol resin, or the like can be used. When the binder is a solid thermoplastic resin or curable resin, the coating solution is prepared by dissolving the binder in an appropriate solvent. When the binder is a liquid curable resin, the binder is prepared by using the liquid curable resin alone. In addition, in order to adjust the viscosity of the liquid curable resin, a coating solution may be prepared by diluting with a solvent or a reactive diluent.

  When the coating liquid is applied onto the base material 2 of the metal particle composite structure 1 and the binder is a solid thermoplastic resin or curable resin, the solvent is dried and removed to solidify, and the binder Is a liquid curable resin, it is solidified by a semi-curing reaction, and as described above, a solid film made of a binder is formed, so that a large number of metal particles 3 are distributed on the substrate 2. Is fixed in the film, and then the film is peeled off from the substrate 2 together with the fixed number of metal particles 3 to produce an anisotropic conductive film. In order to cause a solid curable resin to undergo a curing reaction by heat at the time of pressure bonding, a latent curing agent may be blended in the coating solution.

  The thickness of the binder film that forms the anisotropic conductive film is considered to ensure that the semiconductor package is thermally bonded to the electrode provided on the wiring board by crimping in the case of mounting a normal semiconductor package. Then, it is preferable that it is about 5-50 micrometers. In addition, when the two are thermally bonded by pressure bonding, considering that the metal particles 3 fixed in the film have a good conductive connection between the electrodes and the bumps, the metal particles 3 have the thickness of the film. It is preferable to have a height of approximately 1 to 50% (height in a direction orthogonal to the surface direction of the substrate 2). In the case of the ideal droplet-shaped metal particles 3, the height of the metal particles 3 can be increased or decreased in proportion to the particle size in the surface direction of the substrate 2, so that the substrate 2 in advance. What is necessary is just to adjust the particle size of the metal particle formed above suitably according to the thickness of the film | membrane formed after that.

<Manufacture of metal particle composite structure>
Example 1:
A dispersion containing silver fine particles having a primary particle diameter of 15 nm is applied to the surface of a previously washed alkali-free glass substrate by spin coating (rotation speed: 2000 rpm), dried by heating at 100 ° C. for 10 minutes. Thus, a coating film having a thickness of 0.4 μm was formed. The primary particle size of the silver fine particles in the dispersion is, as described above, a particle size distribution measuring device applying the laser Doppler method [Nanotrack (registered trademark) particle size measuring device UPA- manufactured by Nikkiso Co., Ltd. The peak value of the particle size distribution measured using EX150].

  Next, the alkali-free glass substrate on which the coating film has been formed is put in an electric furnace preheated to 400 ° C. and heat-treated for 30 minutes, then taken out, cooled to room temperature, and the surface thereof is scanned. When observed using an electron microscope, as shown in FIG. 1 and FIG. 2, a large number of silver particles 3 formed by agglomerating silver fine particles in the coating film into droplets on the surface of the substrate 2 are mutually connected. It was confirmed that they were distributed so as not to contact each other. Moreover, it was also confirmed that each silver particle 3 has a shape in which a droplet is brought into surface contact with the surface 20 of the substrate 2 as shown in FIG. Furthermore, when the particle size in the surface direction of the base material 2 of the silver particles 3 distributed on the surface of the base material 2 was determined by the method using the electron micrograph and the image analysis described above, it was 2 μm. .

Example 2:
A heat treatment was carried out in the same manner as in Example 1 except that the temperature of the electric furnace was set to 450 ° C., then taken out, cooled to room temperature, and the surface thereof was observed with a scanning electron microscope. Similarly, it was confirmed that a large number of silver particles 3 formed by agglomerating silver fine particles in the coating film in the form of droplets were distributed on the surface of the substrate 2 so as not to contact each other. It was. It was also confirmed that each silver particle 3 had a shape in which a droplet was brought into surface contact with the surface 20 of the substrate 2. Furthermore, the particle size in the surface direction of the base material 2 of the silver particles 3 distributed on the surface of the base material 2 was determined to be 3.5 μm. And from this, it was confirmed that the particle diameter of the surface direction of the base material 2 of the silver particle formed can be adjusted by changing the conditions of heat processing.

Comparative Example 1:
As the base material, a pre-washed soda glass was used, and after heat treatment in the same manner as in Example 1 except that the temperature of the electric furnace was 180 ° C., it was taken out and cooled to room temperature. When observed using a scanning electron microscope, it was confirmed that a discontinuous silver film was formed on the surface of the substrate 2. From this, it was confirmed that the temperature of the heat treatment needs to be 200 ° C. or higher.

Example 3:
A dispersion containing silver-palladium alloy fine particles (palladium content: 5% by weight) having a primary particle size of 10 nm was used, and heat treatment was performed in the same manner as in Example 1 except that the temperature of the electric furnace was 600 ° C. Then, when taken out and cooled to room temperature, the surface was observed using a scanning electron microscope. As in Example 1, the silver-palladium alloy fine particles in the coating film were formed on the surface of the substrate 2. It was confirmed that a large number of silver-palladium alloy particles 3 produced by aggregation in the form of droplets were distributed apart so as not to contact each other. It was also confirmed that each silver-palladium alloy particle 3 had a shape in which a droplet was brought into surface contact with the surface 20 of the substrate 2. Furthermore, when the particle diameter of the surface direction of the base material 2 of the silver-palladium alloy particles 3 distributed on the surface of the base material 2 was determined, it was 5 μm.

Example 4:
A dispersion containing silver-gold alloy fine particles (gold content: 10% by weight) having a primary particle size of 25 nm is applied to the surface of an alumina (Al ₂ O ₃ ) substrate that has been washed in advance by a dip coating method. The film was heated and dried at 0 ° C. for 10 minutes to form a coating film having a thickness of 0.2 μm.

  Next, the alumina base material on which the coating film is formed is placed in an electric furnace heated to 250 ° C. in advance and heat-treated for 30 minutes, then taken out, cooled to room temperature, and its surface is subjected to a scanning electron microscope. As in Example 1, a large number of silver-gold alloy particles 3 produced by agglomerating silver-gold alloy fine particles in the coating film into droplets on the surface of the substrate 2 as in Example 1, It was confirmed that they were distributed so as not to contact each other. It was also confirmed that each silver-gold alloy particle 3 had a shape in which a droplet was brought into surface contact with the surface 20 of the substrate 2. Furthermore, when the particle size in the surface direction of the base material 2 of the silver-gold alloy particles 3 distributed on the surface of the base material 2 was determined, it was 1 μm.

Example 5:
A dispersion containing fine palladium particles having a primary particle diameter of 2 nm is applied to the surface of a silica (SiO ₂ ) substrate that has been washed in advance by a spray method, and heated and dried at 100 ° C. for 10 minutes to obtain a thickness of 0 A coating film of 0.05 μm was formed.

  Next, the silica base material on which the coating film is formed is put in an electric furnace preheated to 800 ° C., heat-treated for 30 minutes, then taken out, cooled to room temperature, and the surface thereof is subjected to a scanning electron microscope. As in Example 1, a large number of palladium particles 3 produced by agglomeration of palladium fine particles in the coating film in the form of droplets were separated from the surface of the substrate 2 so as not to contact each other. It was confirmed that they were distributed. It was also confirmed that each palladium particle 3 had a shape in which a droplet was brought into surface contact with the surface 20 of the substrate 2. Furthermore, when the particle diameter of the palladium particles 3 distributed on the surface of the base material 2 in the surface direction of the base material 2 was determined, it was 1 μm.

Example 6:
A dispersion containing gold fine particles having a primary particle diameter of 50 nm is applied to the surface of an alumina substrate that has been washed in advance by a dip coating method, and is heated and dried at 100 ° C. for 10 minutes to form a coating film having a thickness of 3 μm. Formed.

  Next, the alumina base material on which the coating film is formed is put in an electric furnace preheated to 600 ° C., heat-treated for 30 minutes, then taken out, cooled to room temperature, and the surface thereof is scanned with a scanning electron microscope. As in Example 1, a large number of gold particles 3 produced by agglomeration of gold fine particles in the coating film in the form of droplets were separated from the surface of the substrate 2 so as not to contact each other. It was confirmed that they were distributed. It was also confirmed that each gold particle 3 had a shape in which a droplet was brought into surface contact with the surface 20 of the substrate 2. Furthermore, when the particle size of the gold particles 3 distributed on the surface of the substrate 2 in the surface direction of the substrate 2 was determined, it was 10 μm.

<Manufacture of anisotropic conductive film>
Example 7:
(Preparation of coating solution for anisotropic conductive film)
Solid epoxy resin [Asahi Kasei Chemicals Co., Ltd. product number 6099] 28 parts by weight, Solid epoxy resin [Asahi Kasei Chemicals Co., Ltd. product number 6144] 12 parts by weight, microcapsule type latent curing agent [Asahi Kasei Chemicals Co., Ltd. No. HX3721] 16 parts by weight, 45 parts by weight of butyl acetate, and 15 parts by weight of methyl isobutyl ketone were mixed to prepare a coating solution for an anisotropic conductive film.

(Manufacture of anisotropic conductive film)
The surface of the non-alkali glass substrate produced in Example 1 and the surface of the silver particle composite structure in which a large number of silver particles having a particle size in the surface direction of the substrate of 2 μm are distributed are distributed on the surface of the silver particles. The above coating solution is applied, dried at room temperature (23 ° C.) and solidified to form a film, thereby fixing the distribution state of a large number of silver particles on the substrate in the film. . Then, the film was peeled off from the base material together with a large number of fixed metal particles to produce an anisotropic conductive film having a thickness of 10 μm.

(Measurement of connection resistance)
An FPC having an electrode pattern in which gold electrodes having a width of 15 μm, a length of 50 μm, and a thickness of 2 μm are arranged at intervals of 15 μm is pasted on the electrode pattern, and the anisotropic conductive film manufactured as described above is pasted and heated to 80 ° C. Then, pressure was applied at a pressure of 0.1 N / mm ² for temporary adhesion. Next, on this anisotropic conductive film, a glass substrate having an aluminum film deposited on one side is overlaid so that the aluminum film is in contact with the anisotropic conductive film, while heating to 200 ° C., 3 N / mm ² The main adhesion was made by pressurizing with pressure. Then, the resistance value between two adjacent gold electrodes conductively connected via the anisotropic conductive film and the aluminum film is measured, and the measured value is halved to connect the anisotropic conductive film in the thickness direction. The resistance was 0.1Ω, and the conductivity in the thickness direction was found to be very good.

(Measurement of insulation resistance)
An FPC having an electrode pattern in which gold electrodes having a width of 15 μm, a length of 50 μm, and a thickness of 2 μm are arranged at intervals of 15 μm is pasted on the electrode pattern, and the anisotropic conductive film manufactured as described above is pasted and heated to 80 ° C. Then, pressure was applied at a pressure of 0.1 N / mm ² for temporary adhesion. Next, on this anisotropic conductive film, a glass substrate on which an aluminum film was not deposited was stacked, and this was pressure bonded at a pressure of 3 N / mm ² while being heated to 200 ° C., and finally bonded. And when the resistance value between two adjacent gold electrodes was measured to obtain the insulation resistance in the surface direction of the anisotropic conductive film, it was found to be 1000 GΩ, and the insulation in the surface direction was very good. .

It is the scanning electron micrograph which expanded a part of metal particle composite structure manufactured in Example 1 of this invention. It is the scanning electron micrograph which expanded a part of metal particle composite structure of the said Example 1 further. It is a scanning electron micrograph which shows the state which looked at one metal particle formed on the base material from the side among the metal particle composite structure of the said Example 1. FIG.

Explanation of symbols

1 Metal Particle Composite Structure 2 Base Material 3 Metal Particle

Claims (3)

  A shape having a base material and a large number of metal particles distributed on the surface of the base material so as not to contact each other, each metal particle having a droplet in surface contact with the surface of the base material A metal particle composite structure, wherein each metal particle has a particle size in the surface direction of the substrate of 0.1 to 20 μm.   A method for producing a metal particle composite structure according to claim 1, wherein a dispersion containing metal fine particles having a primary particle diameter of 200 nm or less is applied to the surface of a substrate and dried to form a coating film; The coating film thus formed is heat-treated at a temperature of 200 ° C. or higher and less than the melting point of the metal forming the metal fine particles, and a large number of metal fine particles dispersed in the coating film are aggregated in droplets to form a base. A method for producing a metal particle composite structure, characterized in that a large number of metal particles are generated on a surface of a material in a state of being distributed so as not to contact each other. A coating liquid containing an insulating binder is applied onto the base material of the metal particle composite structure according to claim 1 and solidified to form a film made of the binder, thereby forming a base material of a large number of metal particles. An anisotropic conductive film characterized in that the above distribution state is fixed in the film.