JP2009259801A - Conductive particulate and conductive connection structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive particulate used for a conductive connection between fine electrodes, excellent in adhesiveness to the electrode, hard to generate cracks in a solder layer because of a shock by a fall and the like, and disconnection by a breakage on the connection interface between the electrode and the conductive particle, and resistive to fatigue even through a repeated heating and cooling operation; and to provide a conductive connection structure using the conductive particulate. <P>SOLUTION: The conductive particle has a solder layer formed on the surface of a resinous particulate. At least one surface-attaching metal selected from a group of palladium, germanium, iron, cobalt and copper is contained in an incompletely covered condition on the surface of the solder layer. The percentage of the surface-attaching metal amounts to 0.001 to 2 wt.% over the total of the metal contained in the solder layer and the surface-attaching metal in the incompletely covered condition on the surface of the solder layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention is used for conductive connection between fine electrodes, has excellent adhesion to the electrode, and cracks of the solder layer due to impact caused by dropping, etc., and breakage of the connection interface between the electrode and the conductive fine particles occur. The present invention relates to conductive fine particles that are difficult to be fatigued even when repeatedly subjected to heating and cooling, and a conductive connection structure using the conductive fine particles.

Conventionally, in an electronic circuit board, ICs and LSIs are connected by soldering electrodes to a printed circuit board. However, soldering cannot efficiently connect the printed circuit board to the IC or LSI. In addition, it is difficult to improve the mounting density of ICs and LSIs by soldering.
In order to solve this problem, a BGA (ball grid array) has been developed in which the solder is made into a spherical shape, so-called “solder balls” that connect the IC or LSI to the substrate. If BGA is used, a solder ball mounted on a chip or a substrate can be melted at a high temperature to connect the substrate and the chip. Therefore, the production efficiency of the electronic circuit board is improved, and an electronic circuit board with an improved chip mounting density can be manufactured.

However, in recent years, since the number of substrates has been increased and multilayer substrates are easily affected by the use environment, there has been a problem that distortion and expansion / contraction occur in the substrates and disconnection occurs in the connection portion between the substrates.

For such a problem, Patent Document 1 discloses a conductive fine particle in which a metal layer containing a highly conductive metal is formed on the surface of a resin fine particle, and a solder layer is further formed on the surface of the metal layer. It is disclosed. If such conductive fine particles are used, the stress applied by the flexible resin fine particles to the conductive fine particles can be relaxed. By forming a low melting point metal layer such as a solder layer on the outermost surface of the conductive fine particles, the electrodes can be easily conductively connected.

However, when conductive fine particles with a solder layer formed on the surface of resin fine particles are used in electronic devices such as mobile phones, the solder layer can be cracked by impact such as dropping, or the connection between the electrode and conductive fine particles Sometimes the interface was destroyed. When the solder layer is cracked or the connection interface is broken, there is a problem that the connection between the electrode and the conductive fine particles is broken.
In addition, when an electronic device is used, the temperature inside the electronic device rises due to the heat generated by the electronic component. After the electronic device is used, the temperature inside the electronic device returns to room temperature. Cycle "is in progress. When this heat cycle was repeated, thermal fatigue of the solder layer occurred, and the connection interface between the electrode and the conductive fine particles was broken and sometimes disconnected.

JP 2001-220691 A

The present invention is used for conductive connection between fine electrodes, has excellent adhesion to the electrode, and cracks of the solder layer due to impact caused by dropping, etc., and breakage of the connection interface between the electrode and the conductive fine particles occur. It is an object of the present invention to provide conductive fine particles that are difficult to be fatigued even when subjected to repeated heating and cooling, and a conductive connection structure using the conductive fine particles.

The present invention provides conductive fine particles in which a solder layer is formed on the surface of resin fine particles, wherein at least one surface-attached metal selected from the group consisting of palladium, germanium, iron, cobalt, and copper is the solder. The surface which is present in a state where the surface of the layer is not completely covered, and occupies the total of the metal contained in the solder layer and the surface-attached metal which is present in a state where the surface of the solder layer is not completely covered It is the electroconductive fine particle whose ratio of an adhering metal is 0.001-2 weight%.
The present invention is described in detail below.

As a result of intensive studies, the inventors of the present invention are selected from the group consisting of palladium, germanium, iron, cobalt, and copper on the surface of the solder layer in the conductive fine particles in which the solder layer is formed on the surface of the resin fine particles. At least one kind of surface-attached metal is present without completely covering the surface of the solder layer, and the conductive fine particles and the electrode are conductively connected by setting the amount of the surface-attached metal to a predetermined ratio. At the time, it was found that the solder layer was not easily cracked by an impact caused by dropping or the like, and the disconnection due to the breakage of the connection interface between the electrode and the conductive fine particles was hardly caused, and the present invention was completed. It was.

In the conductive fine particles of the present invention, a solder layer is formed on the surface of the resin fine particles.

Since the conductive fine particles of the present invention have a solder layer formed on the surface of the resin fine particles, if the conductive fine particles and the electrode are conductively connected, even if the substrate is distorted or stretched, the resin fine particles are flexible. Can relieve the stress applied to the conductive fine particles.
The resin fine particles are not particularly limited, and include, for example, polyolefin resin, acrylic resin, polyalkylene terephthalate resin, polysulfone resin, polycarbonate resin, polyamide resin, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, and the like. Resin fine particles.
The polyolefin resin is not particularly limited, and examples thereof include polyethylene resin, polypropylene resin, polystyrene resin, polyisobutylene resin, polybutadiene resin, polyvinyl chloride resin, polyvinylidene chloride resin, and polytetrafluoroethylene resin. The acrylic resin is not particularly limited, and examples thereof include polymethyl methacrylate resin and polymethyl acrylate resin. These resins may be used alone or in combination of two or more.

The preferable lower limit of the 10% K value of the resin fine particles is 1000 MPa, and the preferable upper limit is 15000 MPa. If the 10% K value is less than 1000 MPa, the resin fine particles may be destroyed when the resin fine particles are compressed and deformed. When the 10% K value exceeds 15000 MPa, the conductive fine particles may damage the electrode. The more preferable lower limit of the 10% K value is 2000 MPa, and the more preferable upper limit is 10,000 MPa.

The 10% K value is determined by using a micro compression tester (for example, “PCT-200” manufactured by Shimadzu Corporation), and using a smooth indenter end face of a diamond cylinder having a diameter of 500 μm and a compression speed of 2.6 mN / sec. The compression displacement (mm) when compressed under the condition of a maximum test load of 10 g can be measured and determined by the following formula.
K value ^{(N / mm 2) = (} 3 / √2) · F · S -3/2 · R -1/2
F: Load value at 10% compression deformation of particles (N)
S: Compression displacement (mm) in 10% compression deformation of particles
R: radius of particle (mm)

The resin fine particles have a preferable lower limit of the average particle diameter of 1 μm and a preferable upper limit of 2000 μm. When the average particle diameter is less than 1 μm, the resin fine particles are likely to aggregate, and the conductive fine particles obtained using the aggregated resin fine particles may short-circuit between adjacent electrodes. When the average particle diameter exceeds 2000 μm, the particle diameter suitable for the anisotropic conductive material may be exceeded. A more preferable lower limit of the average particle diameter is 30 μm, and a more preferable upper limit is 1500 μm. The more preferable lower limit of the average particle diameter is 100 μm, and the more preferable upper limit is 1000 μm.
The average particle diameter of the resin fine particles means an average value of diameters obtained by observing 50 resin fine particles randomly selected using an optical microscope or an electron microscope.

The resin fine particles have a preferred upper limit of CV value of 15%. If the CV value exceeds 15%, the connection reliability of the obtained conductive fine particles may be lowered. A more preferable upper limit of the CV value is 10%. The CV value is a numerical value indicated by a percentage (%) of a value obtained by dividing the standard deviation by the average particle diameter.

The method for producing the resin fine particles is not particularly limited, and examples thereof include a polymerization method, a method using a polymer protective agent, and a method using a surfactant.
The method by the said polymerization method is not specifically limited, The method by polymerization methods, such as emulsion polymerization, suspension polymerization, seed polymerization, dispersion polymerization, and dispersion seed polymerization, is mentioned.

In the conductive fine particles of the present invention, a solder layer is formed on the surface of the resin fine particles. Since the solder layer is melted and joined to the electrode by the reflow process, and the solder layer and the electrode are in surface contact, the connection reliability is increased. The reflow process means "a soldering process in which conductive fine particles provided with a solder layer containing a metal having a low melting point in advance are supplied to a location where an electronic component on a substrate is connected and heated."
In the present invention, the solder layer contains tin as an essential metal, and may further contain a metal such as silver, antimony, copper, bismuth, indium, germanium, aluminum, zinc, or nickel. Although the metal which forms the said solder layer is not specifically limited, Tin, a tin-silver alloy, a tin-zinc alloy, a tin-copper alloy, a tin-silver-copper alloy, a tin-bismuth alloy etc. are mentioned. The metal contained in the solder layer may include the same metal as the surface-attached metal.
In particular, in the present invention, a solder layer containing a tin-silver alloy is preferable because the melting point of the solder layer is lowered and the strength of the solder layer is improved.

The solder layer may contain silver. The proportion of silver in the total of the metal contained in the solder layer and the surface-attached metal present in a state where the surface of the solder layer is not completely covered is not particularly limited, but the preferred lower limit is 0.5 weight. %, And a preferred upper limit is 10% by weight. When the silver ratio is in the range of 0.5 to 10% by weight, the melting point of the solder layer is lowered, and the strength of the solder layer is improved. A more preferable lower limit of the silver ratio is 0.7% by weight, and a more preferable upper limit is 5% by weight.

The ratio of tin in the total of the metal contained in the solder layer and the surface-attached metal present in a state where the surface of the solder layer is not completely covered is not particularly limited, but the ratio of the metal other than tin The balance can be the tin content. The preferable lower limit of the ratio of tin in the total of the metal contained in the solder layer and the surface-attached metal attached to the surface of the solder layer is 88% by weight, and the preferable upper limit is 99.499% by weight. A more preferable lower limit of the ratio of tin in the total of the surface-attached metal adhering to the surface of the solder layer is 89% by weight.

Although the thickness of the said solder layer is not specifically limited, A preferable minimum is 1 micrometer and a preferable upper limit is 50 micrometers. When the thickness of the solder layer is less than 1 μm, the conductive fine particles may not be bonded to the electrode. When the thickness of the solder layer exceeds 50 μm, the conductive fine particles may agglomerate during the formation of the solder layer. The more preferable lower limit of the thickness of the solder layer is 3 μm, and the more preferable upper limit is 40 μm.
The thickness of the solder layer is a thickness obtained by observing and measuring a section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging the measured values.

In the conductive fine particles of the present invention, at least one surface-attached metal selected from the group consisting of palladium, germanium, iron, cobalt, and copper is present in a state that does not completely cover the surface of the solder layer.
When conductive fine particles that exist in a state where the surface-adhering metal does not completely cover the surface of the solder layer are used for connecting electrodes such as substrates, fine particles are formed at the interface between the conductive fine particles and the electrodes after reflow. An intermetallic compound having a proper crystal structure is formed. An intermetallic compound having a large crystal structure is hard and brittle, but when the crystal structure is refined, the hard and brittle nature is relaxed. Accordingly, since the bonding strength of the connection interface between the conductive fine particles and the electrode is improved, the solder layer is hardly cracked or the connection interface is not easily broken by an impact caused by dropping or the like. Furthermore, conductive fine particles that are not easily fatigued even when subjected to repeated heating and cooling can be obtained.
In addition, it is conceivable that an intermetallic compound with a refined crystal structure exerts an anchor effect, so that it is difficult to cause cracks in the solder layer or breakage of the connection interface due to impact due to dropping or the like.

In addition, when conductive fine particles having a solder layer containing tin formed on the outermost surface are mounted on an electrode in which a nickel-phosphorous layer and a gold layer are sequentially formed on the surface of copper and reflowed, the conductive fine particles and the electrode An intermetallic compound such as Cu ₆ Sn ₅ , (Cu, Ni) ₆ Sn ₅ is formed at the connection interface. Since intermetallic compounds such as Cu ₆ Sn ₅ and (Cu, Ni) ₆ Sn ₅ have low crystal symmetry, when stress is generated at the connection interface or when the connection interface is heated, the intermetallic compound crystal is formed. Distortion may occur. In particular, when palladium is used as the surface-attached metal, the atomic radius of palladium (137 pm) is larger than the atomic radius of copper (128 pm) and smaller than the atomic radius of tin (141 pm), so Cu ₆ Sn ₅ , (Cu , Ni) ₆ Sn ₅ , some atoms of lattice sites of intermetallic compounds may be substituted with palladium. When some atoms in the lattice sites are replaced with palladium, the intermetallic compound crystals are less likely to be distorted. Therefore, the bonding strength at the connection interface between the conductive fine particles and the electrode is improved, and heating and cooling are performed. It is considered that fatigue is less likely to occur repeatedly.

Further, when palladium is used as the surface-attached metal, the presence of palladium on the surface of the solder layer allows the metal of palladium and tin to be connected to the connection interface between the conductive fine particles and the electrode in the reflow process. Intermetallic compounds are preferentially formed. As a result, the intermetallic compound of palladium and tin suppresses the diffusion strength of nickel derived from the nickel-phosphorous layer into the solder layer, and thus reduces the bonding strength of the connection interface between the conductive fine particles and the electrode. Formation of the phosphorus-enriched layer is prevented.

The amount of palladium present on the surface of the solder layer is defined as the ratio of palladium in the total of the metal contained in the solder layer and palladium present in a state that does not completely cover the surface of the solder layer. Is done. The lower limit of the proportion of palladium in the total of the metal contained in the solder layer and palladium present in a state where the surface of the solder layer is not completely covered is 0.001 wt%, and the upper limit is 2 wt%. is there. When the ratio of palladium is less than 0.001% by weight, the connection interface between the electrode and the conductive fine particles due to impact such as dropping cannot be prevented, and disconnection occurs. If the proportion of palladium exceeds 2% by weight, the flexibility of the conductive fine particles is impaired, or the conductive fine particles cannot be mounted on the electrode in the reflow process. The preferable lower limit of the proportion of palladium is 0.005% by weight, the preferable upper limit is 1% by weight, and the more preferable upper limit is 0.5% by weight.
The ratio of the metal adhering to the surface should be measured using a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), an inductively coupled plasma emission analyzer (“SPS4000” manufactured by Seiko Denshi Kogyo Co., Ltd.), or the like. Can do. Also, confirm that the surface-attached metal exists without completely covering the surface of the solder layer with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.). Can do.

In the present invention, when palladium is used as the surface-attached metal, molybdenum may be further present without completely covering the surface of the solder layer. The amount of molybdenum present on the surface of the solder layer is not particularly limited, but the proportion of molybdenum in the total of palladium and molybdenum is preferably 30% by weight or less. If the proportion of molybdenum exceeds 30% by weight, a fine intermetallic compound may not be formed at the connection interface between the conductive fine particles and the electrode, and the bonding strength at the connection interface may decrease.

In the present invention, when germanium is used as the surface-attached metal, germanium is more easily oxidized than tin, and therefore has an effect of preventing oxidation of the solder layer containing tin and is expected to improve the wettability of the solder layer. .

When germanium is used as the surface adhering metal, the amount of germanium present on the surface of the solder layer is such that the metal contained in the solder layer and germanium present in a state that does not completely cover the surface of the solder layer. And the ratio of germanium to the total. The lower limit of the ratio of germanium in the total of the metal contained in the solder layer and germanium present in a state where the surface of the solder layer is not completely covered is 0.001% by weight, and the upper limit is 2% by weight. is there. If the germanium ratio is less than 0.001% by weight, the connection interface between the electrode and the conductive fine particles due to impact such as dropping cannot be prevented, and disconnection occurs. When the ratio of germanium exceeds 2% by weight, the flexibility of the conductive fine particles is impaired, or the conductive fine particles cannot be mounted on the electrode in the reflow process. The preferable lower limit of the ratio of germanium is 0.005% by weight, the preferable upper limit is 1% by weight, and the more preferable upper limit is 0.5% by weight.

In the present invention, when iron is used as the surface-adhesive metal, iron exists in a state that does not completely cover the surface of the solder layer containing tin. Therefore, tin and iron contained in the solder layer at the time of reflow are used. And preferentially form a fine intermetallic compound crystal structure. In particular, when the conductive fine particles of the present invention are mounted on an electrode in which a nickel-phosphorous plating layer and a displacement gold plating layer are sequentially formed toward the outermost surface, the crystal structure of a fine intermetallic compound of tin and iron during reflow Therefore, nickel derived from the nickel-phosphorous plating layer can be prevented from diffusing into the solder layer. By preventing diffusion of nickel derived from the nickel-phosphorous plating layer, it is possible to suppress the formation of a phosphorus-enriched layer, which is considered to reduce the strength of the connection interface between the solder layer and the electrode.

When iron is used as the surface-attached metal, the amount of iron present on the surface of the solder layer is such that the metal contained in the solder layer and the iron present in a state that does not completely cover the surface of the solder layer. And defined as the ratio of iron to the total. The lower limit of the ratio of iron in the total of the metal contained in the solder layer and the iron existing in a state where the surface of the solder layer is not completely covered is 0.001% by weight, and the upper limit is 2% by weight. is there. When the ratio of iron is less than 0.001% by weight, the connection interface between the electrode and the conductive fine particles due to impact such as dropping cannot be prevented, and disconnection occurs. When the ratio of iron exceeds 2% by weight, the flexibility of the conductive fine particles is impaired, or it cannot be mounted on the electrode in the reflow process. The preferable lower limit of the ratio of iron is 0.005% by weight, the preferable upper limit is 1% by weight, and the more preferable upper limit is 0.5% by weight.

In the present invention, when iron is used as the surface-attached metal, there may be a state where the surface of the solder layer is not completely covered. The amount of platinum present on the surface of the solder layer is not particularly limited, but the proportion of platinum in the total of iron and platinum is preferably 50% by weight or less. When the proportion of platinum exceeds 50% by weight, a fine intermetallic compound is not formed at the connection interface between the conductive fine particles and the electrode, and the bonding strength at the connection interface may decrease.

In the present invention, when cobalt is used as the surface adhering metal, the amount of cobalt present on the surface of the solder layer exists in a state where the metal contained in the solder layer and the surface of the solder layer are not completely covered. It is defined as the ratio of cobalt to the total of cobalt. The lower limit of the proportion of cobalt in the total of the metal contained in the solder layer and the cobalt present in a state where the surface of the solder layer is not completely covered is 0.001% by weight, and the upper limit is 2% by weight. is there. When the proportion of cobalt is less than 0.001% by weight, the connection interface between the electrode and the conductive fine particles due to impact such as dropping cannot be prevented, and disconnection occurs. When the proportion of cobalt exceeds 2% by weight, the flexibility of the conductive fine particles is impaired, or the conductive fine particles cannot be mounted on the electrode in the reflow process. In addition, the intermetallic compound formed at the connection interface between the solder layer and the electrode increases, and the bonding strength may decrease. The preferable lower limit of the proportion of cobalt is 0.005% by weight, the preferable upper limit is 1% by weight, and the more preferable upper limit is 0.5% by weight.

In the present invention, when cobalt is used as the surface-attached metal, antimony may be further present without completely covering the surface of the solder layer. The amount of antimony present on the surface of the solder layer is not particularly limited, but the proportion of antimony in the total of cobalt and antimony is preferably 50% by weight or less. When the proportion of antimony exceeds 50% by weight, a fine intermetallic compound may not be formed at the connection interface between the conductive fine particles and the electrode, and the bonding strength at the connection interface may decrease.

In the present invention, when copper is used as the surface-attached metal, if the conductive fine particles containing copper are used for connection of electrodes such as a substrate, tin and copper are connected to the connection interface between the conductive fine particles and the electrode after reflow. The intermetallic compound layer is formed. Since the surface of the intermetallic compound layer of tin and copper is rough, the bonding strength at the connection interface between the conductive fine particles and the electrode is improved. Further, when the conductive fine particles containing copper are mounted on an electrode, it is considered that an intermetallic compound layer having an optimum thickness is formed at the connection interface between the conductive fine particles and the electrode. If the intermetallic compound layer is too thin, the bonding strength at the connection interface is not sufficient, and if the intermetallic compound layer is too thick, the connection interface is hard and brittle. Therefore, the conductive fine particles of the present invention are less likely to break the connection interface between the conductive fine particles and the electrode even by an impact caused by dropping or the like, and have excellent thermal fatigue characteristics.

When copper is used as the surface adhering metal, the amount of copper present on the surface of the solder layer is equal to the metal contained in the solder layer and the copper present in a state that does not completely cover the surface of the solder layer. And defined as the ratio of copper to the total. The lower limit of the proportion of copper in the total of the metal contained in the solder layer and the copper present in a state where the surface of the solder layer is not completely covered is 0.001 wt%, and the upper limit is 2 wt%. is there. If the copper ratio is less than 0.001% by weight, the connection interface between the electrode and the conductive fine particles due to impact such as dropping cannot be prevented, and disconnection occurs. When the ratio of copper exceeds 2% by weight, the flexibility of the conductive fine particles is impaired, or the conductive fine particles cannot be mounted on the electrode in the reflow process. The preferable lower limit of the copper ratio is 0.005% by weight, the preferable upper limit is 1% by weight, and the more preferable upper limit is 0.5% by weight.

In the present invention, when copper is used as the surface-attached metal, molybdenum may be further present without completely covering the surface of the solder layer. The amount of molybdenum present on the surface of the solder layer is not particularly limited, but the ratio of molybdenum to the total of copper and molybdenum is preferably 50% by weight or less. If the molybdenum content exceeds 50% by weight, a fine intermetallic compound may not be formed at the connection interface between the conductive fine particles and the electrode, and the bonding strength at the connection interface may decrease.

In the present invention, when copper is used as the surface-attached metal, vanadium may be present without completely covering the surface of the solder layer. The amount of vanadium present on the surface of the solder layer is not particularly limited, but the proportion of vanadium in the total of copper and vanadium is preferably 50% by weight or less. When the proportion of vanadium exceeds 50% by weight, a fine intermetallic compound is not formed at the connection interface between the conductive fine particles and the electrode, and the bonding strength at the connection interface may be lowered.

In addition, when conductive fine particles having a solder layer containing tin formed on the outermost surface are mounted on an electrode in which a nickel-phosphorous layer and a gold layer are sequentially formed on the surface of copper and reflowed, the conductive fine particles and the electrode An intermetallic compound such as Cu ₆ Sn ₅ , (Cu, Ni) ₆ Sn ₅ is formed at the connection interface. Since intermetallic compounds such as Cu ₆ Sn ₅ and (Cu, Ni) ₆ Sn ₅ have low crystal symmetry, when stress is generated at the connection interface or when the connection interface is heated, the intermetallic compound crystal is formed. Distortion may occur.
Since the atomic radius of molybdenum (136 pm) and the atomic radius of vanadium (132 pm) are larger than the atomic radius of copper (128 pm) and smaller than the atomic radius of tin (141 pm), Cu ₆ Sn ₅ , (Cu, Ni) ₆ Some of lattice sites of intermetallic compounds such as Sn ₅ may be substituted with molybdenum or vanadium. When a part of the lattice site is replaced with molybdenum or vanadium, distortion of crystals of the intermetallic compound hardly occurs. As a result, since the bonding strength at the connection interface between the conductive fine particles and the electrode is improved, it is considered that fatigue is less likely to be caused by repeated heating and cooling.

In the conductive fine particles of the present invention, a metal layer may be formed between the resin fine particles and the solder layer.

The metal layer is formed in order to improve the connection reliability of the conductive fine particles of the present invention.
The metal forming the metal layer is not particularly limited, and examples thereof include nickel, copper, palladium, gold, silver, cobalt, titanium, and molybdenum.
In the conductive fine particles of the present invention, it is preferable that a nickel layer, a copper layer, and a solder layer are sequentially formed on the surface of the resin fine particles. In the conductive fine particles of the present invention, a nickel layer may be formed between the copper layer and the solder layer.

Although the thickness of the said metal layer is not specifically limited, A preferable minimum is 0.05 micrometer and a preferable upper limit is 70 micrometers. If the thickness of the metal layer is less than 0.05 μm, sufficient conductivity may not be obtained, and if it exceeds 70 μm, the flexibility of the conductive fine particles may be impaired. A more preferable lower limit of the thickness of the metal layer is 0.1 μm, and a more preferable upper limit is 50 μm.
The thickness of the copper layer is a thickness obtained by observing and measuring a section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging the measured values.

The manufacturing method of the electroconductive fine particles of this invention is not specifically limited, For example, it can manufacture with the following method.

When a metal layer other than the solder layer is formed between the resin fine particles and the solder layer, first, a metal layer is formed on the surface of the resin fine particles by electroless plating, electrolytic plating, or the like.

Next, a solder layer containing tin is formed on the surface of the metal layer.
The method for forming the solder layer is not particularly limited, and examples thereof include an electrolytic plating method and an electroless plating method.

Next, the ratio of the surface-attached metal in the total of the metal contained in the solder layer and the surface-attached metal present in a state where the surface of the solder layer is not completely covered is 0.001 to 2% by weight. As described above, the surface-attached metal is attached to the surface of the solder layer so that the surface of the solder layer is not completely covered.
The method of attaching the surface-attached metal to the surface of the solder layer is not particularly limited as long as the solder layer is not completely covered with the surface-attached metal, and the solder layer may be formed by electroless plating, electrolytic plating, sputtering, or the like. And a method of partially attaching a surface-attached metal to the surface of the substrate.
By attaching a surface-attached metal to the surface of the solder layer, the connection interface between the electrode and the conductive fine particles is destroyed by an impact caused by dropping or the like even if the solder layer does not contain a component of the surface-attached metal. There is no disconnection.
Note that a part of the surface-attached metal attached to the surface of the solder layer may be diffused in the solder layer.

As a method for attaching palladium to the surface of the solder layer, an electroless plating method is preferable. When the electroless plating method is used, the proportion of palladium can be controlled by appropriately setting the concentration, pH, reaction temperature, plating reaction time, and the like of the electroless plating solution.

Examples of the method of attaching germanium to the surface of the solder layer include a method of partially attaching germanium to the surface of the solder layer by an electrolytic plating method, a sputtering method, or the like.

As a method of attaching iron to the surface of the solder layer, an electroless plating method, an electrolytic plating method, a sputtering method, a method of attaching iron nanoparticles to the surface of the solder layer, etc. In particular, there is a method of attaching iron.

Cobalt can be deposited on the surface of the solder layer by electroless plating, electrolytic plating, sputtering, or by depositing cobalt nanoparticles on the surface of the solder layer. For example, a method of depositing cobalt can be mentioned.

As a method of attaching copper to the surface of the solder layer, an electroless plating method is preferable. When the electroless plating method is used, the amount of copper deposited can be controlled by appropriately setting the concentration, pH, reaction temperature, plating reaction time, etc. of the electroless plating solution.

The conductive fine particles of the present invention can be used for connection of electrodes in which a nickel layer and a gold layer are sequentially formed on the surface of copper, and in particular, a nickel-phosphorus layer and a gold layer are sequentially formed on the surface of copper. It is preferable to use it for connecting other electrodes.

In addition, a conductive connection structure using the conductive fine particles of the present invention is also one aspect of the present invention.

According to the present invention, it is used for conductive connection between fine electrodes, has excellent adhesion with the electrode, cracks in the solder layer due to impact due to dropping, etc., and disconnection due to breakage of the connection interface between the electrode and the conductive fine particles Therefore, it is possible to provide conductive fine particles that are less likely to cause fatigue due to repeated heating and cooling, and a conductive connection structure using the conductive fine particles.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
(1) Production of resin fine particles 50 parts by weight of divinylbenzene and 50 parts by weight of tetramethylolmethane tetraacrylate were copolymerized to produce resin fine particles (average particle size 240 μm, CV value 0.42%).

(2) Preparation of Solder Layer 10 g of the obtained resin fine particles were electroless nickel plated to form a base nickel layer having a thickness of 0.3 μm on the surface of the resin fine particles. Next, electrolytic fine copper plating was performed on the resin fine particles on which the base nickel layer was formed, thereby forming a copper layer having a thickness of 10 μm. Furthermore, a solder layer containing 25 μm thick tin and silver was formed by electrolytic plating. Next, the electrolytic plating solution is filtered, and the obtained particles are washed with water and dried with a vacuum dryer at 50 ° C., and the surface of the resin fine particles contains a base nickel layer, a copper layer, tin and silver. Conductive fine particles in which layers were sequentially formed were produced.

(3) Adhesion of palladium 1.5 g of the obtained conductive fine particles were immersed in 30 mL of the following electroless palladium plating solution (liquid temperature 30 ° C.) and stirred. After 5 minutes (plating reaction time) have passed since the conductive fine particles were immersed in the electroless palladium plating solution, the electroless palladium plating solution was filtered, and the resulting particles were washed with water and then vacuum dried at 50 ° C. It was dried with a machine. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which palladium adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

Electroless palladium plating solution composition Palladium sulfate: 0.01 mol / L
Ethylenediamine: 0.05 mol / L
Sodium citrate: 0.05 mol / L

Conductive fine particles with palladium attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the attached palladium was found. The proportion of each metal occupied was 3.5% by weight of silver, 0.05% by weight of palladium, and the balance was tin.
The thicknesses of the base nickel layer, the copper layer, and the solder layer are measured by observing a cross section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM), and the measured values are arithmetically averaged. Was calculated. Further, it was confirmed with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) that palladium was adhered to the surface of the solder layer. The same applies hereinafter.

(Example 2)
Conductive fine particles having palladium adhered to the surface of the solder layer were prepared in the same manner as in Example 1 except that the temperature of the electroless palladium plating solution was 40 ° C. and the plating reaction time was 10 minutes.
Conductive fine particles with palladium attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the attached palladium was found. The proportion of each metal occupied was 3.5% by weight of silver, 0.5% by weight of palladium, and the balance was tin.

(Example 3)
Conductive fine particles having palladium adhered to the surface of the solder layer were prepared in the same manner as in Example 1 except that the temperature of the electroless palladium plating solution was 40 ° C. and the plating reaction time was 15 minutes.
Conductive fine particles with palladium attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the attached palladium was found. The proportion of each metal occupied was 3.5% by weight of silver and 1.0% by weight of palladium, and the balance was tin.

Example 4
(1) Preparation of resin fine particles, (2) Preparation of solder layer In the same manner as in Example 1, a base nickel layer, a copper layer, and a solder layer containing tin and silver are sequentially formed on the surface of the resin fine particles. Conductive fine particles were prepared.

(3) Palladium adhesion 1.5 g of the obtained conductive fine particles were immersed in 30 mL of the following electroless palladium-molybdenum plating solution (liquid temperature 35 ° C.) and stirred. After 10 minutes (plating reaction time) has elapsed since the conductive fine particles were immersed in the electroless palladium-molybdenum plating solution, the electroless palladium-molybdenum plating solution was filtered, and the resulting particles were washed with water, then 50 It dried with the vacuum dryer of degreeC. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which palladium and molybdenum were adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.02%.

Electroless palladium-molybdenum plating solution composition Palladium sulfate: 0.01 mol / L
Sodium hypophosphite: 0.3 mol / L
Diethylamine: 0.06 mol / L
Sodium citrate: 0.03 mol / L
Sodium molybdate: 0.005 mol / L

Conductive fine particles with palladium and molybdenum adhering to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The metal contained in the solder layer and the adhering palladium were analyzed. The proportion of each metal in the total of molybdenum and molybdenum was 3.5% by weight of silver, 0.1% by weight of palladium, 0.02% by weight of molybdenum, and the balance was tin.

(Comparative Example 1)
Conductive fine particles were produced in the same manner as in Example 1 except that electroless palladium plating was not performed and palladium was not attached to the surface of the solder layer. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 0.81%.

(Comparative Example 2)
Conductive solder balls composed of tin, silver and copper (“M705” manufactured by Senju Metal Industry Co., Ltd., average particle size 300 μm (tin: silver: copper = 96.5 wt%: 3 wt%: 0.5 wt%)) Used as conductive fine particles.

(Comparative Example 3)
Conductive fine particles having palladium adhered to the surface of the solder layer were prepared in the same manner as in Example 1 except that the temperature of the electroless palladium plating solution was 40 ° C. and the plating reaction time was 60 minutes.
Conductive fine particles with palladium attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the attached palladium was found. The proportion of each metal occupied was 3.45% by weight of silver and 5.0% by weight of palladium, with the balance being tin.
In addition, since the conductive fine particles obtained in Comparative Example 3 could not be mounted on the electrode, the drop strength test and the temperature cycle test were not performed.

(Example 5)
(1) Production of resin fine particles, (2) Production of solder layer Conductive fine particles were produced in the same manner as in Example 1.

(3) Adhesion of germanium Germanium was adhered to the surface of the solder layer of the obtained conductive fine particles by a sputtering method. When the conductive fine particles having germanium adhered to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the total amount of the metal contained in the solder layer and the adhered germanium was calculated. The proportion of each metal occupied was 3.5% by weight of silver and 0.005% by weight of germanium, with the balance being tin.
The thicknesses of the base nickel layer, the copper layer, and the solder layer are measured by observing a cross section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM), and the measured values are arithmetically averaged. Was calculated. Further, it was confirmed with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) that germanium was adhered to the surface of the solder layer. The same applies hereinafter.

(Example 6)
Conductive fine particles were produced in the same manner as in Example 5 except that the conditions of the sputtering method were adjusted. The proportion of each metal in the total of the metal contained in the solder layer and the attached germanium was 3.5% by weight of silver, 0.1% by weight of germanium, and the balance was tin.

(Example 7)
Conductive fine particles were produced in the same manner as in Example 5 except that the conditions of the sputtering method were adjusted. The ratio of each metal to the total of the metal contained in the solder layer and the attached germanium was 3.5% by weight of silver and 1.0% by weight of germanium, and the balance was tin.

(Comparative Example 4)
Conductive fine particles were produced in the same manner as in Example 5 except that the conditions of the sputtering method were adjusted. The ratio of each metal to the total of the metal contained in the solder layer and the attached germanium was 3.5% by weight of silver, 5.0% by weight of germanium, and the balance was tin.
In addition, since the electroconductive fine particles obtained in Comparative Example 4 could not be mounted on the electrode, the drop strength test was not performed.

(Example 8)
(1) Production of resin fine particles, (2) Production of solder layer Conductive fine particles were produced in the same manner as in Example 1.

(3) Adhesion of iron The obtained conductive fine particles are immersed in a dispersion liquid in which iron particles (volume average particle diameter 3 nm) subjected to rust prevention are dispersed, and the iron particles are adhered to the surface of the conductive fine particles. It was. The dispersion was filtered, and the resulting particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles having iron adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

Conductive fine particles with iron attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The total of the metal contained in the solder layer and the attached iron The proportion of each metal occupied was 3.5% by weight of silver and 0.005% by weight of iron, with the balance being tin.
In addition, the thickness of the said nickel base layer, a copper layer, and a solder layer is measured by observing the cross section of 10 electroconductive fine particles selected at random with a scanning electron microscope (SEM), and a measured value is an arithmetic mean. It was calculated by doing. Moreover, it was confirmed with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) that iron was adhered to the surface of the solder layer. The same applies hereinafter.

Example 9
Except having adjusted the density | concentration of the iron particle of a dispersion liquid, the electroconductive fine particle which iron adhered to the surface of the solder layer similarly to Example 8 was produced. Conductive fine particles with iron attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The total of the metal contained in the solder layer and the attached iron The proportion of each metal occupied was 3.5% by weight of silver and 0.1% by weight of iron, with the balance being tin.

(Example 10)
Except having adjusted the density | concentration of the iron particle of a dispersion liquid, the electroconductive fine particle which iron adhered to the surface of the solder layer similarly to Example 8 was produced. Conductive fine particles with iron attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The total of the metal contained in the solder layer and the attached iron The proportion of each metal occupied was 3.5% by weight of silver and 1.0% by weight of iron, with the balance being tin.

Example 11
In the same manner as in Example 1, conductive fine particles were prepared in which a base nickel layer, a copper layer, and a solder layer containing tin and silver were sequentially formed on the surface of the resin fine particles.
The obtained conductive fine particles were immersed in a dispersion in which iron-platinum alloy particles (volume average particle diameter 3 nm) were dispersed, and the iron-platinum alloy particles were adhered to the surface of the conductive fine particles. The dispersion was filtered, and the resulting particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which iron and platinum adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

When the conductive fine particles in which iron and platinum are adhered to the surface of the solder layer are analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the iron contained in the solder layer and the adhered iron The proportion of each metal in the total with platinum was 3.5% by weight of silver, 0.05% by weight of iron and 0.01% by weight of platinum, with the balance being tin.

(Comparative Example 5)
Except having adjusted the density | concentration of the iron particle of a dispersion liquid, the electroconductive fine particle which iron adhered to the surface of the solder layer similarly to Example 8 was produced. Conductive fine particles with iron attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The total of the metal contained in the solder layer and the attached iron The proportion of each metal occupied was 3.5% by weight of silver and 5.0% by weight of iron, with the balance being tin.
In addition, since the electroconductive fine particles obtained in Comparative Example 5 could not be mounted on the electrode, the drop strength test and the temperature cycle test were not performed.

Example 12
(1) Production of resin fine particles, (2) Production of solder layer Conductive fine particles were produced in the same manner as in Example 1.

(3) Adhesion of cobalt The electroconductive fine particles obtained were electrolessly cobalt-plated, and cobalt was adhered to the surface of the solder layer. The electroless cobalt plating solution was filtered, and the resulting particles were washed with water and then dried with a 50 ° C. vacuum dryer. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which cobalt adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

When the conductive fine particles with cobalt attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the total of the metal contained in the solder layer and the attached cobalt was obtained. The proportion of each metal occupied was 3.5% by weight of silver and 0.02% by weight of cobalt, with the balance being tin.
The thicknesses of the underlying nickel layer, copper layer, and solder layer were measured by observing a cross section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM), and the measured values were arithmetically averaged. It was calculated by doing. Moreover, it was confirmed with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) that cobalt was adhered to the surface of the solder layer. The same applies hereinafter.

(Example 13)
Except that the plating reaction time of electroless cobalt plating was adjusted, conductive fine particles having cobalt adhered to the surface of the solder layer were prepared in the same manner as in Example 12. When the conductive fine particles with cobalt attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the total of the metal contained in the solder layer and the attached cobalt was obtained. The proportion of each metal occupied was 3.5% by weight of silver and 0.5% by weight of cobalt, with the balance being tin.

(Example 14)
Except that the plating reaction time of electroless cobalt plating was adjusted, conductive fine particles having cobalt adhered to the surface of the solder layer were prepared in the same manner as in Example 12. When the conductive fine particles with cobalt attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the total of the metal contained in the solder layer and the attached cobalt was obtained. The proportion of each metal occupied was 3.5% by weight of silver and 2.0% by weight of cobalt, with the balance being tin.

(Example 15)
The resin fine particles obtained in Example 1 were subjected to electroless nickel plating to form a base nickel layer having a thickness of 0.3 μm on the surface of the resin fine particles. Next, electrolytic fine copper plating was performed on the resin fine particles on which the base nickel layer was formed, thereby forming a copper layer having a thickness of 10 μm. Furthermore, a solder layer containing 25 μm thick tin and silver was formed by electrolytic plating. Next, the electrolytic plating solution is filtered, and the obtained particles are washed with water and dried with a vacuum dryer at 50 ° C., and the surface of the resin fine particles contains a base nickel layer, a copper layer, tin and silver. Conductive fine particles in which layers were sequentially formed were produced.

The obtained conductive fine particles were electrolytically plated to allow cobalt and antimony to adhere to the surface of the solder layer. The electrolytic plating solution was filtered, and the obtained particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which cobalt and antimony adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

When the conductive fine particles having cobalt and antimony adhered to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the metal contained in the solder layer and cobalt adhered The proportion of each metal in the total amount with antimony was 3.5% by weight of silver, 0.05% by weight of cobalt and 0.05% by weight of antimony, and the balance was tin.

(Comparative Example 6)
Except that the plating reaction time of electroless cobalt plating was adjusted, conductive fine particles having cobalt adhered to the surface of the solder layer were prepared in the same manner as in Example 12. When the conductive fine particles with cobalt attached to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the total of the metal contained in the solder layer and the attached cobalt was obtained. The proportion of each metal occupied was 3.5% by weight of silver and 5.0% by weight of cobalt, with the balance being tin.
In addition, since the electroconductive fine particles obtained in Comparative Example 6 could not be mounted on the electrode, the drop strength test was not performed.

(Example 16)
(1) Production of resin fine particles, (2) Production of solder layer Conductive fine particles were produced in the same manner as in Example 1.

(3) Adhesion of copper The obtained electroconductive fine particles were subjected to electroless copper plating, and copper was adhered to the surface of the solder layer. The electroless copper plating solution was filtered, and the resulting particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which copper adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

Conductive fine particles with copper adhering to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the adhering copper was found. The proportion of each metal occupied was 3.5% by weight of silver and 0.005% by weight of copper, with the balance being tin.
In addition, the thickness of the said nickel base layer, a copper layer, and a solder layer is measured by observing the cross section of 10 electroconductive fine particles selected at random with a scanning electron microscope (SEM), and a measured value is an arithmetic mean. It was calculated by doing. Moreover, it was confirmed with a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) that copper was adhered to the surface of the solder layer. The same applies hereinafter.

(Example 17)
Except for adjusting the plating reaction time of electroless copper plating, conductive fine particles having copper adhered to the surface of the solder layer were prepared in the same manner as in Example 16. Conductive fine particles with copper adhering to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the adhering copper was found. The proportion of each metal occupied was 3.5% by weight of silver and 0.1% by weight of copper, and the balance was tin.

(Example 18)
Except for adjusting the plating reaction time of electroless copper plating, conductive fine particles having copper adhered to the surface of the solder layer were prepared in the same manner as in Example 16. Conductive fine particles with copper adhering to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the adhering copper was found. The proportion of each metal occupied was 3.5% by weight of silver and 2.0% by weight of copper, and the balance was tin.

Example 19
The resin fine particles obtained in Example 1 were subjected to electroless nickel plating to form a base nickel layer having a thickness of 0.3 μm on the surface of the resin fine particles. Next, electrolytic fine copper plating was performed on the resin fine particles on which the base nickel layer was formed, thereby forming a copper layer having a thickness of 10 μm. Further, a solder layer containing tin and silver having a thickness of 25 μm was formed by electrolytic plating. Next, the electrolytic plating solution is filtered, and the obtained particles are washed with water and dried with a vacuum dryer at 50 ° C., and the surface of the resin fine particles contains a base nickel layer, a copper layer, tin and silver. Conductive fine particles in which layers were sequentially formed were produced.

The obtained conductive fine particles were electroplated to adhere copper and molybdenum to the surface of the solder layer. The electrolytic plating solution was filtered, and the obtained particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which copper and molybdenum adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

When the conductive fine particles having copper and molybdenum adhered to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the copper contained with the metal contained in the solder layer and The proportion of each metal in the total with molybdenum was 3.5% by weight of silver, 0.05% by weight of copper, 0.01% by weight of molybdenum, and the balance was tin.

(Example 20)
The resin fine particles obtained in Example 1 were subjected to electroless nickel plating to form a base nickel layer having a thickness of 0.3 μm on the surface of the resin fine particles. Next, electrolytic fine copper plating was performed on the resin fine particles on which the base nickel layer was formed, thereby forming a copper layer having a thickness of 10 μm. Furthermore, a solder layer containing 25 μm thick tin and silver was formed by electrolytic plating. Next, the electrolytic plating solution is filtered, and the obtained particles are washed with water and dried with a vacuum dryer at 50 ° C., and the surface of the resin fine particles contains a base nickel layer, a copper layer, tin and silver. Conductive fine particles in which layers were sequentially formed were produced.

The obtained conductive fine particles were electroplated, and copper and vanadium were adhered to the surface of the solder layer. The electrolytic plating solution was filtered, and the obtained particles were washed with water and then dried with a vacuum dryer at 50 ° C. A base nickel layer, a copper layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles in which copper and vanadium were adhered to the surface of the solder layer were produced. The average particle diameter of the conductive fine particles was 310 μm, and the CV value was 1.0%.

When the conductive fine particles having copper and vanadium adhered to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the metal contained in the solder layer and copper adhered The proportion of each metal in the total with vanadium was 3.5% by weight of silver, 0.05% by weight of copper and 0.01% by weight of vanadium, and the balance was tin.

(Comparative Example 7)
Except for adjusting the plating reaction time of electroless copper plating, conductive fine particles having copper adhered to the surface of the solder layer were prepared in the same manner as in Example 16. Conductive fine particles with copper adhering to the surface of the solder layer were analyzed with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), and the total of the metal contained in the solder layer and the adhering copper was found. The proportion of each metal occupied was 3.5% by weight of silver and 5.0% by weight of copper, with the balance being tin.

<Evaluation>
The following evaluation was performed about the electroconductive fine particles obtained by the Example and the comparative example. The results are shown in Table 1.

(Drop strength test)
A flux (“WS-9160-M7” manufactured by Cookson Electronics Co., Ltd.) was applied to 112 electrode lands (diameter: 280 μm) provided at a pitch of 0.5 mm on a silicon chip (length: 6 mm × width: 6 mm). The obtained conductive fine particles were placed on all the electrode lands, reflowed (heating temperature 250 ° C., 30 seconds), and the conductive fine particles were mounted on the electrode lands.
Next, a solder paste (“M705-GRN360-K2-V” manufactured by Senju Metal Industry Co., Ltd.) was applied to the printed circuit board on which the copper electrode (diameter 305 μm) was formed. Fifteen silicon chips on which conductive fine particles were mounted were placed on a printed circuit board, reflowed (heating temperature 250 ° C., 30 seconds), and 15 silicon chips were mounted on the printed circuit board to obtain a conductive connection structure.
According to JEDEC standard JESD22-B111, a drop strength test of the obtained conductive connection structure was performed.
Since the obtained conductive connection structure is formed with a daisy chain circuit, it can be detected even if one electrode land is disconnected.
The number of drops at which all 15 silicon chips were disconnected was measured.
In the electrode land, a copper layer, a nickel-phosphorus layer, and a gold layer were sequentially formed toward the outermost surface of the electrode land. The same applies hereinafter.
The drop strength test was evaluated according to the following criteria.
A: The number of drops at which all 15 silicon chips were disconnected was 100 times or more.
X: The number of times of dropping of all 15 silicon chips was less than 100 times.

(Temperature cycle test)
A flux (“WS-9160-M7” manufactured by Cookson Electronics Co., Ltd.) was applied to 112 electrode lands (diameter: 280 μm) provided at a pitch of 0.5 mm on a silicon chip (length: 6 mm × width: 6 mm). The obtained conductive fine particles were placed on all the electrode lands, reflowed (heating temperature 250 ° C., 30 seconds), and the conductive fine particles were mounted on the electrode lands.
Next, a solder paste (“M705-GRN360-K2-V” manufactured by Senju Metal Industry Co., Ltd.) was applied to the printed circuit board on which the copper electrode (diameter 305 μm) was formed. One silicon chip on which conductive fine particles were mounted was placed on a printed circuit board, reflowed (heating temperature 250 ° C., 30 seconds), and one silicon chip was mounted on the printed circuit board to obtain a conductive connection structure.
Since the obtained conductive connection structure is formed with a daisy chain circuit, it can be detected even if one electrode land is disconnected.
Using the obtained conductive connection structure, a temperature cycle test was performed with -40 ° C to 125 ° C as one cycle. The heat profile of the temperature cycle test was held at −40 ° C. for 10 minutes, raised from −40 ° C. to 125 ° C. for 2 minutes, held at 125 ° C. for 10 minutes, and then from 125 ° C. to −40 ° C. for 2 minutes. It was a heat profile that lowered the temperature.
The temperature cycle test was evaluated according to the following criteria.
(Circle): The cycle number by which the disconnection of a conductive connection structure is confirmed was 2000 cycles or more.
X: The number of cycles in which disconnection of the conductive connection structure was confirmed was less than 2000 cycles.

According to the present invention, it is used for conductive connection between fine electrodes, has excellent adhesion with the electrode, cracks in the solder layer due to impact due to dropping, etc., and disconnection due to breakage of the connection interface between the electrode and the conductive fine particles Therefore, it is possible to provide conductive fine particles that are less likely to cause fatigue due to repeated heating and cooling, and a conductive connection structure using the conductive fine particles.

Claims (4)

Conductive fine particles in which a solder layer is formed on the surface of the resin fine particles,
At least one surface-attached metal selected from the group consisting of palladium, germanium, iron, cobalt, and copper is present without completely covering the surface of the solder layer;
The ratio of the surface-attached metal to the total of the metal contained in the solder layer and the surface-attached metal present in a state where the surface of the solder layer is not completely covered is 0.001 to 2% by weight. Conductive fine particles characterized by The ratio of the surface-attached metal to the total of the metal contained in the solder layer and the surface-attached metal present in a state where the surface of the solder layer is not completely covered is 0.001 to 1% by weight. The conductive fine particles according to claim 1, wherein The conductive fine particles according to claim 1, wherein a metal layer is further formed between the resin fine particles and the solder layer. A conductive connection structure comprising the conductive fine particles according to claim 1, 2 or 3.