JP2004109121A - Anisotropic conductive sheet and probe for measuring impedances - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic conduction sheet usable in impedance measurement in a high-frequency region at 1GHz or higher, in particular in a high-frequency region at 10GHz or higher, and a probe for measuring impedance which suppresses the occurrence of damage on a substrate to be measured in impedance measurement in a high-frequency region at 1GHz or higher, in particular in a high frequency region at 10GHz or higher and obtains a high measurement reliability. <P>SOLUTION: The anisotropic conduction sheet has a thickness of 10 to 100 μm and a number average particle size of conductive particle exhibiting magnetism is 5 to 50 μm. The ratio of the thickness W<SB>1</SB>and the number average particle size D of conductive particle exhibiting magnetism, W<SB>1</SB>/D is 1.1 to 10 and the containing fraction of the conductive particle exhibiting magnetism is 10-40% in weight fraction, which is used in impedance measurement in the high-frequency region. The impedance measurement probe is provided with the anisotropic conduction sheet and is used in the high frequency region. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method for measuring the characteristic impedance of a printed wiring circuit on a printed wiring board in a high frequency region, and for measuring an electrical property of a high frequency semiconductor device. For probes.

In recent years, as the processing speed of a computer or the like has increased, the clock frequency of a CPU (central processing unit) and the operating clock frequency for the CPU to communicate with an external device have been significantly increased.
As the operating clock frequency increases in this way, demands on the performance of a printed wiring board for transmitting data signals between the CPU and an external device have become severe.

Specifically, in a printed circuit board, matching the characteristic impedance of a printed circuit formed by signal lines with the characteristic impedance of another printed circuit electrically connected to the printed circuit, It is required to match the characteristic impedance of the printed wiring circuit with the impedance of a circuit load electrically connected to the printed wiring circuit.

There is a mismatch in characteristic impedance between printed wiring circuits that are electrically connected to each other, or a mismatch between the characteristic impedance of the printed wiring circuit and the impedance of a circuit load that is electrically connected to the printed wiring circuit. In such a case, a part of the data signal is reflected to the signal transmission source, which weakens the signal finally going to the circuit load, and may not transmit the desired data signal. Problems arise. Such a problem becomes remarkable as the operating clock frequency increases and becomes a nonnegligible level.

Therefore, in order to maintain the quality of the printed wiring board, it is indispensable to measure the characteristic impedance of the printed wiring circuit in the printed wiring board, and a quality inspection of the printed wiring board is performed based on the measurement result. ing.
Conventionally, a TDR (Time Domain Refrectrometry) method has been used for measuring the impedance of a printed wiring circuit on a printed wiring board.

According to this method, a pulse signal or a step signal is transmitted to a transmission circuit including a signal circuit (a circuit under test) to be measured and a reference ground circuit, and a reflected signal in the transmission circuit is detected and reflected. The impedance value (characteristic impedance) of the transmission circuit (circuit under test) is obtained using the reflection coefficient obtained from the signal.

In such a TDR method, when transmitting a signal to a transmission circuit, a probe is used as an intermediary for electrically connecting a cable derived from a signal source and the transmission circuit.
Such an impedance measuring probe is provided with a contact pin for a circuit to be measured for contacting a circuit to be measured and a contact pin for a ground circuit for contacting a ground circuit. A macrostrip structure formed by sandwiching a plate-shaped dielectric layer between the contact pin and the internal conductor and the external conductor are arranged in a coaxial line shape. And a coaxial line structure formed by extracting a ground circuit contact pin from an external conductor.

Regardless of the structure of such an impedance measurement probe, the tip of the contact pin for the circuit to be measured and the tip of the contact pin for the ground circuit are connected to the signal circuit and the ground circuit, which are the circuit to be measured, respectively. At the same time, the impedance is measured.

However, in a conventional impedance measuring probe, a conductive state is formed by pressing a pointed contact pin against a signal circuit or a ground circuit of the printed wiring board, so that the printed wiring board is damaged during impedance measurement. There was something.

Furthermore, since the metal contact pins are brought into contact with the signal circuit and ground circuit of the printed wiring board, there is a problem that the contact state between the impedance measurement probe and the printed wiring board is unstable and the reliability of measurement is low. It is difficult to accurately measure the impedance with the impedance measuring probe described above.
In addition, it is expected that the operating clock frequency of equipment for connecting to a computer will be further increased in the future, and that the miniaturization and the densification of electronic components will be further advanced. Along with this, it is thought that the importance of accurately measuring the characteristic impedance will further increase in order to ensure the quality of the printed wiring board.However, conventional probes for impedance measurement can adequately respond to such demands. May not be possible.

On the other hand, as disclosed in Patent Document 1, for example, conventionally, in an electrical inspection of a printed wiring board, contact stability is obtained as a member for achieving electrical connection, and printed wiring is performed at the time of contact. Since it is possible to suppress the occurrence of damage to the substrate, it is possible to use an anisotropic conductive sheet and arrange the anisotropic conductive sheet between the printed wiring board and the inspection electrode to achieve a contact conductive state. It was done.

However, the conventionally known anisotropic conductive sheet has a problem such as a large transmission loss when used in a high frequency region, and therefore, sufficient characteristics cannot be obtained in impedance measurement in a high frequency region. In practice, it was difficult to use.

JP-A-3-183974

The present invention has been made in view of the above points, and a first object of the present invention is to provide an anisotropic conductive sheet that can be used for impedance measurement in a high-frequency region of 1 GHz or more, particularly in a high-frequency region of 10 GHz or more. It is in.
A second object of the present invention is to suppress the occurrence of damage to a substrate to be measured during impedance measurement in a high-frequency region of 1 GHz or more, particularly in a high-frequency region of 10 GHz or more, and to obtain impedance measurement with high measurement reliability. To provide a probe for use.

The anisotropic conductive sheet according to the first aspect of the present invention is a sheet base made of an elastic polymer material, in which conductive particles exhibiting magnetism are dispersed in a plane direction and contained in a state oriented in a thickness direction. An anisotropic conductive sheet comprising:
The thickness is 10 to 100 μm, the number average particle diameter of the conductive particles exhibiting magnetism is 5 to 50 μm, and the ratio W ₁ / of the thickness W ₁ to the number average particle diameter D of the conductive particles exhibiting magnetism. D is 1.1 to 10, and the content ratio of the conductive particles exhibiting magnetism is 10 to 40% by weight, and is used for impedance measurement in a high frequency region.

The anisotropic conductive sheet according to the first aspect of the present invention preferably contains a non-magnetic conductive material in a uniformly dispersed state.

The anisotropic conductive sheet according to the second aspect of the present invention includes a plurality of conductive portions extending in the thickness direction, wherein conductive members exhibiting magnetism are densely contained in a sheet base made of an elastic polymer material; An anisotropic conductive sheet formed with an insulating portion that insulates each other,
The thickness of the conductive portion is 10 to 100 [mu] m, with a number average particle diameter of the conductive particles exhibiting magnetism is 5 to 50 [mu] m, the number average particle diameter D of the conductive particles exhibiting thickness W ₂ and the magnetic conductive portion The ratio W ₂ / D is 1.1 to 10, and the content of the conductive particles exhibiting magnetism in the conductive portion is 10 to 40% by weight and used for impedance measurement in a high frequency region. And

In the anisotropic conductive sheet according to the second aspect of the present invention, it is preferable that the conductive material having no magnetism is contained in a state where the conductive material is uniformly dispersed in the conductive portion and the insulating portion.

In the anisotropic conductive sheet according to the second aspect of the present invention, the conductive portion connected to the circuit to be measured on the substrate to be measured of the probe for impedance measurement is insulated from the conductive portion connected to the ground circuit of the substrate to be measured. It may be separated by a part.

イ ン ピ ー ダ ン ス A probe for impedance measurement according to the present invention includes the above-described anisotropic conductive sheet, and is used in a high-frequency region.

The anisotropic conductive sheet of the present invention has a specific thickness and contains magnetic conductive particles having a specific number average particle diameter. It has excellent electrical properties that it can be measured and has sufficient elasticity, so it does not damage the substrate to be measured at the time of conducting pressure and has good durability for repeated use. It is.
Therefore, the anisotropic conductive sheet of the present invention can be suitably used for impedance measurement in a high-frequency region of 1 GHz or more, particularly in a high-frequency region of 10 GHz or more, and is used for measuring a fine-pitch printed wiring board or an electronic component. It can be.

Since the impedance measuring probe of the present invention is provided with the above-described anisotropic conductive sheet, the low transmission loss property of the anisotropic conductive sheet, the effect of preventing damage to the substrate to be measured, and the favorable Due to the durability of repeated use, it shows excellent performance in a high frequency region, specifically, a high frequency region of 1 G or more.
Therefore, according to the impedance measuring probe of the present invention, in the high frequency region of 1 GHz or more, particularly in the high frequency region of 10 GHz or more, the occurrence of damage to the substrate to be measured during impedance measurement is suppressed, and high measurement reliability is achieved. Obtainable.

Hereinafter, embodiments of the present invention will be described in detail.
The anisotropic conductive sheet of the present invention is an anisotropic conductive sheet used for measuring impedance in a high frequency region, and includes conductive particles exhibiting magnetism (hereinafter, also referred to as “magnetic conductive particles”) and elasticity. And a substrate made of a molecular substance.
Specifically, it is an anisotropic conductive sheet having the following configurations (1) and (2).

(1) A sheet base made of an elastic polymer material containing magnetic conductive particles dispersed in a plane direction and aligned in a thickness direction (hereinafter, referred to as “first anisotropic material”). Also referred to as "conductive sheet.")
(2) A plurality of conductive portions that are densely containing magnetic conductive particles and extend in a thickness direction and an insulating portion that insulates the conductive portions from each other are formed in a sheet base made of an elastic polymer material. (Hereinafter, also referred to as “second anisotropic conductive sheet”)

The magnetic conductive particles constituting the anisotropic conductive sheet of the present invention are required to have a number average particle size of 5 to 50 μm.
The number average particle diameter of the magnetic conductive particles is preferably from 6 to 30 μm, and particularly preferably from 8 to 20 μm.
Here, the “number average particle size of the magnetic conductive particles” refers to a value measured by a laser diffraction scattering method.

When the number average particle diameter of the magnetic conductive particles is 5 μm or more, the resulting anisotropic conductive sheet can easily undergo pressure deformation of a portion containing the magnetic conductive particles, and the manufacturing process thereof In the above, the magnetic conductive particles are easily oriented by the magnetic field alignment treatment, so that the obtained anisotropic conductive sheet has a high anisotropy, and the magnetic conductive particles are particularly uniformly dispersed in the surface direction in the sheet substrate. The anisotropic conductive sheet in this state has good resolution (insulation between test electrodes for measuring impedance adjacent in the horizontal direction during pressurization conduction).

On the other hand, when the number average particle diameter of the magnetic conductive particles is 50 μm or less, the obtained anisotropic conductive sheet has good elasticity, and particularly, in the second anisotropic conductive sheet, The conductive portion can be easily formed.

As the magnetic conductive particles, from the viewpoint that the magnetic conductive particles can be easily moved by the action of a magnetic field in a sheet forming material for forming an anisotropic conductive sheet by a manufacturing method described below, Those having a magnetization of 0.1 Wb / m ² or more can be preferably used, more preferably 0.3 Wb / m ² or more, and particularly preferably 0.5 Wb / m ² or more.
When the saturation magnetization is 0.1 Wb / m ² or more, the magnetic conductive particles can be surely moved by the action of a magnetic field in the manufacturing process to obtain a desired orientation state. When used, a chain of magnetic conductive particles can be formed.

Specific examples of the magnetic conductive particles include iron, nickel, particles of a metal exhibiting magnetism such as cobalt, particles of an alloy thereof, or particles containing these metals, or these particles as core particles, and the core particles. Composite particles coated with highly conductive metal on the surface, or inorganic particles or polymer particles such as non-magnetic metal particles or glass beads as core particles, and the surface of the core particles was plated with a highly conductive metal. Examples include composite particles or composite particles in which core particles are coated with both a conductive magnetic material such as ferrite and an intermetallic compound and a highly conductive metal.
Here, “highly conductive metal” refers to a metal having a conductivity of 5 × 10 ⁶ Ω ⁻¹ m ⁻¹ or more at 0 ° C.
As such a highly conductive metal, specifically, gold, silver, rhodium, platinum, chromium, and the like can be used. Among these, gold is chemically stable and has high conductivity. Preferably, it is used.

Among these magnetic conductive particles, composite particles in which nickel particles are used as core particles and the surfaces thereof are plated with a highly conductive metal such as gold or silver are preferable.
Means for coating the surface of the core particles with a highly conductive metal is not particularly limited, but for example, an electroless plating method can be used.

The magnetic conductive particles preferably have a coefficient of variation of the number average particle diameter of 50% or less, more preferably 40% or less, further preferably 30% or less, and particularly preferably 20% or less. .
Here, the “variation coefficient of the number average particle diameter” is represented by the formula: (σ / Dn) × 100 (where σ indicates the value of the standard deviation of the particle diameter, and Dn indicates the number average particle diameter of the particles) Shown)).
When the coefficient of variation of the number average particle diameter of the magnetic conductive particles is 50% or less, the degree of irregularity of the particle diameter is reduced, and thus the portion of the resulting anisotropic conductive sheet containing the magnetic conductive particles is obtained. Can be reduced.

Such magnetic conductive particles can be obtained by converting a metal material into particles by an ordinary method, or by preparing commercially available metal particles and performing a classification treatment on the particles.
The classification process of the particles can be performed by a classifier such as an air classifier or a sonic sieve.
Further, specific conditions for the classification treatment are appropriately set according to the number average particle diameter of the target conductive metal particles, the type of the classification device, and the like.

In the magnetic conductive particles, the specific shape is not particularly limited, particles having a shape of a secondary particle formed by integrally connecting a plurality of spherical primary particles, particles of a preferred shape It can be mentioned as.

In the case where a composite particle in which the surface of a core particle is coated with a highly conductive metal (hereinafter, also referred to as “conductive composite metal particle”) is used as the magnetic conductive particle, a viewpoint that good conductivity is obtained. Therefore, the coverage of the highly conductive metal on the surface of the conductive composite metal particles (the ratio of the area of the highly conductive metal to the surface area of the core particles) is preferably 40% or more, and more preferably 45% or more. And particularly preferably 47 to 95%.
Further, the coating amount of the highly conductive metal is preferably from 2.5 to 50% by mass, more preferably from 3 to 45% by mass, still more preferably from 3.5 to 40% by mass, particularly preferably from 2.5 to 50% by mass of the weight of the core particles. Preferably it is 5 to 30% by mass.

は In the conductive composite metal particles, the thickness t of the coating layer made of a highly conductive metal, calculated by the following formula, is preferably 10 nm or more, more preferably 10 to 100 nm.

[Where t is the thickness of the coating layer (m), Sw is the BET specific surface area of the conductive composite metal particles (m ² / kg), ρ is the specific gravity of the highly conductive metal (kg / m ³ ), and N is the coating. The coverage by the layer (weight of highly conductive metal constituting the coating layer / weight of conductive composite metal particles) is shown. ]

When the thickness t of the coating layer is 10 nm or more, the conductive composite metal particles have high conductivity, and the anisotropic conductive sheet using the conductive composite metal particles as the magnetic conductive particles has a high temperature. It is less likely that the coating layer is peeled off due to a change or pressure and the conductivity is reduced.

The conductive composite metal particles may be those whose surfaces have been treated with a coupling agent such as a silane coupling agent.
By treating the surface of the conductive composite metal particles with the coupling agent, the adhesion between the conductive composite metal particles and the elastic polymer material is increased, and as a result, the resulting anisotropic conductive sheet has high durability. It has the property.
The amount of the coupling agent to be used is appropriately selected within a range that does not affect the conductivity of the conductive composite metal particle body. However, the coating ratio of the coupling agent on the surface of the conductive composite metal particle (the conductive composite metal particle (The ratio of the coating area of the coupling agent to the surface area of the main body) is preferably 5% or more, more preferably 7 to 100%, further preferably 10 to 100%, and particularly preferably 20 to 100%. Amount.

In the first anisotropic conductive sheet, the content ratio of the magnetic conductive particles is 10 to 40% by weight, particularly preferably 15 to 30%.
When the content ratio of the magnetic conductive particles is less than 10%, the anisotropic conductive sheet hardly obtains a low inductance property in the measurement system in the impedance measurement, and is transmitted particularly in the impedance measurement in a high frequency region of 1 GHz or more. Loss is unlikely to be low.
On the other hand, when the content ratio of the magnetic conductive particles exceeds 40%, the anisotropic conductive sheet has a low elasticity and tends to be fragile, and easily damages a substrate to be measured such as a printed wiring board during impedance measurement. Become.

In the second anisotropic conductive sheet, the content ratio of the magnetic conductive particles in the conductive portion is 10 to 40% by weight, particularly preferably 15 to 30%.
When the content ratio of the magnetic conductive particles is less than 10%, the anisotropic conductive sheet hardly obtains a low inductance property in the measurement system in the impedance measurement, and is transmitted particularly in the impedance measurement in a high frequency region of 1 GHz or more. Loss is unlikely to be low.
On the other hand, when the content ratio of the magnetic conductive particles exceeds 40%, the conductive portion of the anisotropic conductive sheet has low elasticity and tends to be fragile. It is easy to hurt.

The elastic polymer material constituting the sheet substrate of the anisotropic conductive sheet of the present invention is preferably a cured product of liquid rubber. As such liquid rubber, liquid silicone rubber, liquid polyurethane rubber and the like can be used. . Among these, liquid silicone rubber is preferred. The liquid silicone rubber as the polymer material-forming material preferably has a viscosity of 10 ⁵ poise or less at a strain rate of 10 ^-1 sec and is a condensation type, an addition type, or a vinyl group or hydroxyl group-containing one. And so on.
Specifically, dimethyl silicone raw rubber, methyl vinyl silicone raw rubber, methyl phenyl vinyl silicone raw rubber and the like can be mentioned.

Among these, a liquid group-containing silicone rubber (vinyl group-containing polydimethylsiloxane) is usually prepared by hydrolyzing dimethyldichlorosilane or dimethyldialkoxysilane in the presence of dimethylvinylchlorosilane or dimethylvinylalkoxysilane. And a condensation reaction, for example, followed by fractionation by repeated dissolution-precipitation.
The liquid silicone rubber containing vinyl groups at both ends is anionically polymerized with a cyclic siloxane such as octamethylcyclotetrasiloxane in the presence of a catalyst, using dimethyldivinylsiloxane as a polymerization terminator, and other reaction conditions. (For example, the amount of the cyclic siloxane and the amount of the polymerization terminator) are appropriately selected. Here, as a catalyst for the anionic polymerization, an alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C.

On the other hand, liquid silicone rubber containing hydroxyl groups (hydroxyl group-containing polydimethylsiloxane) is usually prepared by subjecting dimethyldichlorosilane or dimethyldialkoxysilane to hydrolysis and condensation reaction in the presence of dimethylhydrochlorosilane or dimethylhydroalkoxysilane. For example, followed by fractionation by repeated dissolution-precipitation.
Further, the liquid silicone rubber containing a hydroxyl group is obtained by anionic polymerization of a cyclic siloxane in the presence of a catalyst, and using, for example, dimethylhydrochlorosilane, methyldihydrochlorosilane or dimethylhydroalkoxysilane as a polymerization terminator, and other reaction conditions. (For example, the amount of the cyclic siloxane and the amount of the polymerization terminator) can also be obtained by appropriately selecting the amount. Here, as a catalyst for the anionic polymerization, an alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C.

Such an elastic polymer material preferably has a molecular weight Mw (mean weight average molecular weight in terms of standard polystyrene) of 10,000 to 40,000.
In addition, from the viewpoint of heat resistance of the obtained first anisotropically conductive sheet, the molecular weight distribution index (refers to the value of the ratio Mw / Mn between the standard polystyrene equivalent weight average molecular weight Mw and the standard polystyrene equivalent number average molecular weight Mn). Is preferably 2 or less.

For obtaining the anisotropic conductive sheet of the present invention, containing a polymer material forming material and magnetic conductive particles, in a sheet molding material for forming an anisotropic conductive sheet by a manufacturing method described below, A curing catalyst for curing the polymer-forming material can be included.
As such a curing catalyst, an organic peroxide, a fatty acid azo compound, a hydrosilylation catalyst, or the like can be used.
Specific examples of the organic peroxide used as the curing catalyst include benzoyl peroxide, bisdicyclobenzoyl peroxide, dicumyl peroxide, ditertiary butyl peroxide, and the like.
Specific examples of the fatty acid azo compound used as a curing catalyst include azobisisobutyronitrile and the like.
Specific examples of the hydrosilylation reaction catalyst that can be used as a curing catalyst include chloroplatinic acid and salts thereof, a platinum-unsaturated group-containing siloxane complex, a complex of vinylsiloxane and platinum, and platinum and 1,3-divinyltetrafluoroethylene. Known examples include a complex with methyldisiloxane, a complex of triorganophosphine or phosphite with platinum, an acetylacetate platinum chelate, and a complex of cyclic diene and platinum.
The amount of the curing catalyst used is appropriately selected in consideration of the type of the polymer substance-forming material, the type of the curing catalyst, and other curing treatment conditions. 15 parts by mass.

The anisotropic conductive sheet of the present invention may contain a conductive material that does not show magnetism (hereinafter, also referred to as “non-magnetic conductive material”).
Specifically, in the first anisotropic conductive sheet, the non-magnetic conductive material is contained in a state of being uniformly dispersed, and in the second anisotropic conductive sheet, the second anisotropic conductive sheet has the second anisotropic conductive material. It is contained in a state where it is uniformly dispersed in the conductive portion and the insulating portion constituting the conductive sheet.
The non-magnetic conductive material is added to the polymer material forming material before the curing treatment, so that the non-magnetic conductive material can be contained in the anisotropic conductive sheet obtained by molding so as to be uniformly dispersed in both the surface direction and the thickness direction. it can.
Such a non-magnetic conductive material has an effect of preventing the anisotropic conductive sheet from being charged by adding an appropriate amount thereof without impairing the anisotropic conductivity in the obtained anisotropic conductive sheet.
When the anisotropically conductive sheet is prevented from being charged by the effect of the nonmagnetic conductive material, the anisotropically conductive sheet may be rejected when the impedance measurement using the anisotropically conductive sheet is repeatedly performed. It is possible to prevent the measurement result from being adversely affected due to the electrification of the conductive sheet.

As the nonmagnetic conductive substance, a substance which itself exhibits conductivity (hereinafter, also referred to as “self-conductive substance”), a substance which exhibits conductivity by absorbing moisture (hereinafter, “hygroscopic conductive substance”) Etc.) can be used.

As the self-conductive substance, in general, a substance that exhibits conductivity due to a metal bond, a substance in which charge transfer occurs due to the movement of surplus electrons, a substance in which charge transfer occurs due to the movement of vacancies, generates ions, Select from a substance whose ions carry charge, a substance that has π bonds along the main chain and exhibits conductivity due to the interaction, and a substance that causes charge transfer by the interaction of groups in the side chain. be able to.
Specifically, metal particles containing platinum, gold, silver, copper, nickel, cobalt, iron, aluminum, manganese, zinc, tin, lead, indium, molybdenum, niobium, tantalum, chromium, etc .; copper dioxide, zinc oxide, Conductive metal oxides such as tin oxide; whiskers such as potassium titanate; semiconductive materials such as germanium, silicon, indium phosphorus, and zinc sulfide; carbon-based materials such as carbon black and graphite; quaternary ammonium salts; Substances that generate cations such as amine compounds; negative ions such as aliphatic sulfonates, higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher alcohol phosphates, and higher alcohol ethylene oxide addition phosphates; Substances that generate ions; cations such as betaine and anions Material to generate both down; polyacetylene-based polymers, acryl-based polymers, polyphenylene-based polymers, heterocyclic polymers, rudder polymers, network polymers, and a conductive polymer material such as an ionic polymer.

Substances that generate ions exemplified as one type of self-conductive substance may be collectively referred to as surfactants.
Further, in a polymer such as a polyacetylene-based polymer, an acrylic polymer, a polyphenylene-based polymer, a ladder polymer, and a network polymer, the conductivity can be controlled by doping a metal ion or the like.
In general, the moisture-absorbing conductive substance is preferably a substance having a large hygroscopic property, and is preferably a substance having a highly polar group such as a hydroxyl group or an ester group.
Specifically, silicon compounds such as chloropolysiloxane, alkoxysilane, alkoxypolysilane, and alkoxypolysiloxane; polymer materials such as conductive urethane, polyvinyl alcohol or a copolymer thereof; higher alcohol ethylene oxide, polyethylene glycol fatty acid ester; Alcohol surfactants such as polyhydric alcohol fatty acid esters, polysaccharides and the like can be used.

Among the above nonmagnetic conductive substances, preferred are aliphatic sulfonates.
In addition, among the aliphatic sulfonic acid salts, it is particularly preferable to use a metal salt of an alkyl sulfonic acid. In this case, the obtained anisotropic conductive sheet is provided with an appropriate conductivity and has a good antistatic effect. In addition, since the metal salt of alkyl sulfonic acid has excellent thermal stability, a stable antistatic effect can be obtained even when the anisotropic conductive sheet is repeatedly used for impedance measurement in a high-frequency region.

As the metal salt of the alkyl sulfonic acid, an alkali metal salt is preferable.
Specific examples of the alkali metal salt include sodium 1-decanesulfonate, sodium 1-undecanesulfonate, sodium 1-dodecanesulfonate, sodium 1-tridecanesulfonate, sodium 1-tetradecanesulfonate, and 1-pentadecanesulfone. Sodium acid, sodium 1-hexadecane sulfonate, sodium 1-heptadecane sulfonate, sodium 1-octadecane sulfonate, sodium 1-nonadecane sulfonate, sodium 1-eicosandecane sulfonate, potassium 1-decane sulfonate, 1 -Potassium undecanesulfonate, potassium 1-dodecanesulfonate, potassium 1-tridecanesulfonate, potassium 1-tetradecanesulfonate, potassium 1-pentadecanesulfonate, 1-hexadecanesulfone Potassium, potassium 1-heptadecane sulfonate, potassium 1-octadecane sulfonate, potassium 1-nonadecane sulfonate, potassium 1-eicosandecane sulfonate, lithium 1-decane sulfonate, lithium 1-undecane sulfonate, 1- Lithium dodecanesulfonate, lithium 1-tridecanesulfonate, lithium 1-tetradecanesulfonate, lithium 1-pentadecanesulfonate, lithium 1-hexadecanesulfonate, lithium 1-heptadecanesulfonate, lithium 1-octadecanesulfonate, Lithium nonadecane sulfonate, lithium 1-eicosandecane sulfonate and isomers thereof can be mentioned.

Among these compounds, sodium salts are particularly preferred because of their excellent heat resistance.
These compounds may be used in combination of two or more.
The content ratio of the metal salt of alkyl sulfonic acid is preferably in the range of 0.1 to 30% by mass in the polymer substance constituting the sheet base material.
The reason is that when the content ratio of the metal salt of alkylsulfonic acid is less than 0.1% by mass, the antistatic effect of the obtained anisotropic conductive sheet may be low, while 30% by mass If it exceeds, the mechanical strength of the obtained anisotropically conductive sheet is reduced, and in particular, in the case of the second anisotropically conductive sheet, the electric conductivity of the insulating portion located between the adjacent conductive portions. And the insulation between the conductive portions may be insufficient, which is not preferable.

The sheet molding material may contain an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, alumina, and diamond powder, if necessary.
By appropriately containing such an inorganic filler, the thixotropy of the sheet molding material is ensured, the viscosity is increased, and the dispersion stability of the magnetic conductive particles is improved, and the obtained anisotropic material is obtained. The strength of the conductive sheet increases. In addition, by appropriately improving the hardness of the surface of the anisotropic conductive sheet, the anisotropic conductive sheet can have an effect of improving durability against repeated use in impedance measurement.
The use amount of such an inorganic filler is not particularly limited, but when used in a large amount, the orientation state of the magnetic conductive particles due to the magnetic field cannot be changed to a desired state, and thus it is preferable. Absent.
The viscosity of the sheet molding material is preferably in the range of 100,000 to 1,000,000 cp at a temperature of 25 ° C.

FIG. 1 is an explanatory cross-sectional view showing a configuration of an example of the anisotropic conductive sheet according to the first invention.
In the first anisotropic conductive sheet 10, magnetic conductive particles P are contained in a sheet base made of an elastic polymer material in a state of being uniformly dispersed in a plane direction and oriented in a thickness direction. It is.

Such a first anisotropic conductive sheet 10 can be manufactured, for example, by the following method.
First, a flowable sheet molding material in which the magnetic conductive particles P and the non-magnetic conductive material used as needed are dispersed in a polymer material forming material that becomes a sheet substrate by curing treatment is prepared. As shown in FIG. 2, the sheet molding material is injected into the mold 20 to form the sheet molding material layer 10A.

Here, the mold 20 is configured by arranging an upper mold 21 and a lower mold 22 each made of a rectangular ferromagnetic plate so as to face each other via a rectangular frame-shaped spacer 23. A cavity is formed between the lower surface and the upper surface of the lower mold 22.

Next, for example, an electromagnet or a permanent magnet is arranged on the upper surface of the upper mold 21 and the lower surface of the lower mold 22, and a parallel magnetic field is applied to the sheet forming material layer 10 </ b> A in the mold 20 in the thickness direction. As a result of the magnetic field orientation treatment, in the sheet forming material layer 10A, the state in which the magnetic conductive particles P dispersed in the sheet forming material layer are dispersed in the plane direction is maintained as shown in FIG. While aligning in the thickness direction.
When the non-magnetic conductive material is contained in the sheet forming material layer 10A, the non-magnetic conductive material is dispersed in the sheet forming material layer 10A even when a parallel magnetic field acts. It is in the state as it is.
In this state, by curing the sheet molding material layer 10A, the magnetic conductive particles P are contained in the sheet base made of an insulating elastic polymer material in a state of being aligned in the thickness direction. A first anisotropic conductive sheet 10 is obtained.

In the above manufacturing process, the intensity of the parallel magnetic field applied to the sheet forming material layer 10A is preferably such that the average is 0.02 to 1.5T.
When a parallel magnetic field is applied in the thickness direction of the sheet forming material layer 10A by the permanent magnet, the permanent magnet has a parallel magnetic field strength in the above-described range, and therefore, is preferably an alnico (Fe-Al-Ni-Co-based). Alloy), ferrite or the like.
The curing treatment of the sheet forming material layer 10A can be performed while the parallel magnetic field is applied, but can also be performed after the operation of the parallel magnetic field is stopped.
The curing treatment of the sheet molding material layer 10A is appropriately selected depending on the material used, but is usually performed by a heat treatment. The specific heating temperature and heating time are appropriately set in consideration of the type of the material for forming the polymer substance constituting the sheet forming material layer 10A, the time required for the movement of the magnetic conductive particles P, and the like.

The first anisotropic conductive sheet 10 needs to have a thickness of 10 to 100 μm.
When the thickness is less than 10 μm, the anisotropic conductive sheet has low elasticity. Therefore, the anisotropic conductive sheet is arranged between an inspection object such as a printed wiring board and an inspection electrode. When pressure is applied to achieve the contact conduction state, the inspection object is easily damaged.
On the other hand, when the thickness exceeds 100 μm, when the anisotropic conductive sheet is placed between the inspection object such as a printed wiring board and the inspection electrode and pressurized to achieve the contact conduction state, the inspection is performed. The distance between the object and the inspection electrode becomes large, and transmission loss hardly decreases in impedance measurement in a high frequency region, specifically, a high frequency region of 1 GHz or more.

In the first anisotropic conductive sheet 10, the ratio W ₁ / D of the thickness W ₁ (μm) to the number average particle diameter D (μm) of the magnetic conductive particles is 1.1 to 10. There is a need to be.
When the ratio W ₁ / D is less than 1.1, the diameter of the magnetic conductive particles becomes equal to or larger than the thickness of the anisotropic conductive sheet. Therefore, when the anisotropic conductive sheet is placed between the test object such as a printed wiring board and the test electrode and pressurized to achieve contact conduction, the test object may be damaged. It will be easier.
On the other hand, when the ratio W ₁ / D exceeds 10, when the anisotropic conductive sheet is placed between the inspection object such as a printed wiring board and the inspection electrode to apply pressure and achieve a contact conduction state. In addition, a large number of conductive particles are arranged between the object to be inspected and the inspection electrode to form a chain. Therefore, since there are contact points between a large number of conductive particles, a high-frequency region, specifically, In the measurement of impedance in a high frequency region of 1 GHz or more, the transmission loss is not easily reduced.

FIG. 4 is an explanatory cross-sectional view showing a configuration of an example of the anisotropic conductive sheet according to the second invention.
The second anisotropic conductive sheet 40 includes a plurality of conductive portions 11 extending in the thickness direction in which magnetic conductive particles are densely contained in a sheet base made of an elastic polymer material, The insulating portion 12 is made of a sheet base material made of an elastic polymer material and insulated from each other.
In the example of this figure, the conductive portion 11 is formed so as to protrude from both surfaces of the insulating portion 12.

Such a second anisotropic conductive sheet 40 can be manufactured, for example, as follows.
FIG. 5 is an explanatory cross-sectional view illustrating a configuration of an example of a mold used to manufacture the second anisotropic conductive sheet 40.
This mold is configured such that an upper mold 50 and a lower mold 55 to be paired with the upper mold 50 are arranged so as to face each other via a frame-shaped spacer 54, and a lower surface of the upper mold 50 and an upper surface of the lower mold 55 are formed. A cavity is formed between them.
In the upper die 50, a ferromagnetic layer 52 is formed on the lower surface of the substrate 51 according to a pattern opposite to the intended arrangement pattern of the conductive portions 11 of the anisotropic conductive sheet 40. The non-magnetic layer 53 having a thickness larger than the thickness of the ferromagnetic layer 52 is formed at the position (1).
On the other hand, in the lower die 55, a ferromagnetic layer 57 is formed on the upper surface of the substrate 56 in accordance with the same pattern as the arrangement pattern of the conductive portions 11 of the target anisotropic conductive sheet 40. At other locations, a nonmagnetic layer 58 having a thickness larger than the thickness of the ferromagnetic layer 57 is formed.

As shown in FIG. 6, using such a mold, a polymer material to be a sheet base is formed in the mold by a curing treatment in the same manner as in the first anisotropic conductive sheet of the present invention. A sheet forming material layer 40A is formed by injecting a flowable sheet forming material in which the magnetic conductive particles P and a non-magnetic conductive material used as needed are dispersed in the material to form the sheet forming material layer 40A. For example, an electromagnet or a permanent magnet is disposed on the lower surface of the lower mold 55, and a parallel magnetic field is applied to the sheet forming material layer 40A in the mold in the thickness direction. As a result of this magnetic field orientation treatment, as shown in FIG. 7, the sheet molding material layer 40A has a portion between the ferromagnetic layer 52 of the upper die 50 and the corresponding ferromagnetic layer 57 of the lower die 55. In this case, since a magnetic field having a higher intensity than the other portions is applied, the magnetic conductive particles P dispersed in the sheet molding material layer 40A gather at the portion 11A where the high-intensity magnetic field is applied. In this state, by curing the sheet molding material layer 40A, a plurality of conductive portions 11 extending in the thickness direction, in which the magnetic conductive particles P are densely contained in the sheet base made of the elastic polymer material, are provided. Then, a second anisotropic conductive sheet 40 comprising the insulating portion 12 for insulating the conductive portion 11 from each other is obtained.

The second anisotropic conductive sheet 40 needs to have a thickness of the conductive portion 11 of 10 to 100 μm.
When the thickness of the conductive portion 11 is less than 10 μm, the anisotropic conductive sheet has a low elasticity. Therefore, the anisotropic conductive sheet is placed between the inspection object such as a printed wiring board and the inspection electrode. When the contact is established by applying pressure to achieve a contact conduction state, the inspection object is easily damaged.
On the other hand, when the thickness of the conductive portion 11 exceeds 100 μm, when the anisotropic conductive sheet is arranged between the inspection object such as a printed wiring board and the inspection electrode to apply pressure and achieve a contact conduction state. In addition, the distance between the object to be inspected and the inspection electrode is increased, and transmission loss is less likely to be reduced in impedance measurement in a high frequency region, specifically, a high frequency region of 1 GHz or more.

In the second anisotropic conductive sheet 40, the ratio W ₂ / D of the thickness W ₂ (μm) of the conductive portion 11 to the number average particle diameter D (μm) of the magnetic conductive particles is 1. It is required to be 1 to 10.
When the ratio W ₂ / D is less than 1.1, the diameter of the magnetic conductive particles is equal to or larger than the thickness of the conductive portion of the anisotropic conductive sheet. The conductive part has low elasticity, so when this anisotropic conductive sheet is placed between the inspection object such as a printed wiring board and the inspection electrode and pressurized to achieve the contact conduction state, In addition, the inspection object is easily damaged.
On the other hand, when the ratio W ₂ / D exceeds 10, when an anisotropic conductive sheet is arranged between an inspection object such as a printed wiring board and an inspection electrode to apply pressure and achieve a contact conduction state. In addition, a large number of conductive particles are arranged between the object to be inspected and the inspection electrode to form a chain. Therefore, since there are contact points between a large number of conductive particles, a high-frequency region, specifically, In the measurement of impedance in a high frequency region of 1 GHz or more, the transmission loss is not easily reduced.

The anisotropic conductive sheet of the present invention is not limited to the above embodiment, and various changes can be made.
For example, as shown in FIGS. 8 and 9, the second anisotropic conductive sheet has a cylindrical conductive portion K, an inner diameter larger than the conductive portion K, and a cylinder having the same axis as the conductive portion K. It may include two conductive portions, namely, a conductive portion G having a shape of a circle. In the anisotropic conductive sheet 80, the conductive portion K is a conductive portion connected to the measuring circuit of the impedance measuring probe main body, and the conductive portion G is connected to the ground circuit connecting circuit of the impedance measuring probe main body. It is a conductive part to be performed.
These conductive portions K and G forming the anisotropic conductive sheet 80 contain magnetic conductive particles densely, and the conductive portions K and G are electrically connected by the insulating portion N. Insulated.

FIG. 10 is an explanatory conceptual diagram showing the impedance measuring probe of the present invention in which the anisotropic conductive sheet 80 shown in FIGS. 8 and 9 is provided in the impedance measuring probe main body.
The impedance measuring probe 120 has a cylindrical measuring circuit 121 and a cylindrical ground circuit connecting circuit 122 having an inner diameter larger than the measuring circuit 121 and having the same axis as the measuring circuit 121. The impedance measuring probe body 120 </ b> A has a cylindrical shape and the anisotropic conductive sheet 80.
In the impedance measuring probe 120, the end surface of the conductive portion K on one side (the lower surface in FIG. 10) of the anisotropic conductive sheet 80 is connected to the measuring circuit 121 of the impedance measuring probe main body 120A. Is connected to the ground circuit connection circuit 122 of the impedance measurement probe main body 120A.
In the example of this figure, in the anisotropic conductive sheet 80, the conductive part K has a diameter suitable for the measurement circuit 121, and the conductive part G has a diameter suitable for the ground circuit connection circuit 122.
The impedance measuring probe 120 provided with the anisotropic conductive sheet 80 has a surface opposite to one surface connected to the impedance measuring probe main body 120A of the anisotropic conductive sheet 80 (the upper surface in FIG. 10). Is brought into contact with a printed wiring board, which is a substrate to be measured, and pressurized, through each conductive portion (conductive portion K and conductive portion G) of the anisotropic conductive sheet 80, the impedance and the circuit to be measured of the printed wiring board are measured. Conduction is achieved by connecting the measurement circuit 121 of the measurement probe main body 120A and connecting the reference ground circuit of the printed wiring board and the ground circuit connection circuit 122 of the impedance measurement probe main body 120A, An impedance measurement is performed.

<Example>
Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to the following examples.

<Preparation of anisotropic conductive sheet>
In 100 parts by mass of an addition-type liquid silicone rubber “KE2000-60” manufactured by Shin-Etsu Chemical Co., Ltd., 22.5 parts by mass of magnetic conductive particles having a number average particle diameter of 8 μm and sodium alkyl sulfonate (C _n H _{2n + A} sheet molding material was prepared by adding and mixing 2.5 parts by mass of ₁ SO ₃ Na (n = 12 to 20).
In the above, composite particles (average coating amount: 7% by mass of the weight of the core particles) obtained by applying gold plating to core particles made of nickel were used as the magnetic conductive particles.
The prepared sheet molding material was injected into a mold having the spacer shown in FIG. 2 and having a thickness of 30 μm to form a sheet molding material layer.
Then, a hardening treatment is performed at 100 ° C. for 1 hour while applying a magnetic field of 2 T in the thickness direction to the sheet molding material layer formed between the upper mold and the lower mold made of the ferromagnetic plate by an electromagnet. By performing the above, an anisotropic conductive sheet having the configuration shown in FIG. 1 was manufactured. Hereinafter, this anisotropic conductive sheet is referred to as “anisotropic conductive sheet C1”.

<Evaluation of high frequency characteristics of anisotropic conductive sheet>
For the manufactured anisotropically conductive sheet C1, a value expressed by combining the inductance of the measurement system when used for impedance measurement and the resistance loss at the particle interface of the magnetically conductive particles constituting the anisotropically conductive sheet. It was determined whether or not the anisotropic conductive sheet was suitable for use in a high frequency region using the transmission loss as an index.
Specifically, transmission loss (S-parameter) at a frequency of 10 GHz to 60 GHz is measured using a network analyzer, and the value of the measured transmission loss (S-parameter) is in the range of −2 dB to 0 dB. Was evaluated as passing.
Here, when the value of the transmission loss (S parameter) is in the range of −2 dB to 0 dB, the impedance of a printed wiring board or the like can be measured in a good condition, and particularly in the range of −1 dB to 0 dB. If, the impedance measurement can be performed in a better condition.
On the other hand, when the value of the transmission loss (S parameter) is greater than -2 dB in absolute value, impedance measurement becomes difficult.
The results are shown in Table 1. In Table 1, the case where the value of the measured transmission loss (S parameter) was in the range of -1 dB to 0 dB is indicated by "O", and the value of the measured transmission loss (S parameter) was -2 dB to- The case where the value was within the range of 1 dB is indicated by “△”, and the case where the measured value of the transmission loss (S parameter) became larger than the absolute value of −2 dB is indicated by “×”.

[Examples 2 to 10 and Comparative Examples 1 to 8]
In Example 1, as shown in Table 1, the number average particle diameter of the magnetic conductive particles to be used, the mass of the magnetic conductive particles to be added, the gold plating amount of the magnetic conductive particles, and the thickness of the spacer constituting the mold were set as follows. Anisotropically conductive sheets C2 to C18 were produced in the same manner as in Example 1 except that each was changed.
With respect to the manufactured anisotropically conductive sheets C2 to C18, transmission loss (S parameter) was measured in the same manner as in Example 1, and the high-frequency characteristics of the anisotropically conductive sheet were evaluated. The results are shown in Table 1.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory sectional drawing which shows the structure in an example of the anisotropic conductive sheet which concerns on 1st this invention. FIG. 3 is an explanatory sectional view showing a state in which a sheet forming material layer is formed in a mold for manufacturing an anisotropic conductive sheet according to the first invention. It is explanatory sectional drawing which shows the state which applied the parallel magnetic field to the thickness direction to the sheet forming material layer formed in the metal mold | die for manufacture of the anisotropic conductive sheet which concerns on the 1st this invention. It is explanatory sectional drawing which shows the structure in an example of the anisotropic conductive sheet which concerns on 2nd this invention. It is explanatory sectional drawing which shows the structure in an example of the metal mold | die for manufacture of the anisotropic conductive sheet which concerns on 2nd this invention. It is explanatory sectional drawing which shows the state in which the sheet forming material layer was formed in the metal mold | die for manufacture of the anisotropic conductive sheet which concerns on 2nd this invention. It is explanatory sectional drawing which shows the state which applied the parallel magnetic field in the thickness direction to the sheet forming material layer formed in the metal mold | die for manufacture of the anisotropic conductive sheet which concerns on 2nd this invention. It is a top view showing an example of a modification of the anisotropic conductive sheet concerning the 2nd present invention. It is a sectional view showing an example of a modification of the anisotropic conductive sheet concerning the 2nd present invention. FIG. 1 is an explanatory cross-sectional view illustrating a configuration of an example of an impedance measurement probe according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Anisotropic conductive sheet 10A Sheet molding material layer 11 Conductive part 11A Part to which strong magnetic field is applied 12 Insulating part 20 Mold 21 Upper die 22 Lower die 23 Spacer P Magnetic conductive particles 40 Anisotropic conductive sheet 40A sheet molding material layer 50 upper die 51 substrate 52 ferromagnetic layer 53 non-magnetic layer 54 spacer 55 lower die 56 substrate 57 ferromagnetic layer 58 non-magnetic layer 80 anisotropic conductive sheet 120 impedance measuring probe 120A impedance Measuring probe body 121 Measurement circuit 122 Ground circuit connection circuit K Conducting part G Conducting part N Insulating part

Claims (6)

Anisotropically conductive sheet containing in a sheet base made of an elastic polymer material, conductive particles exhibiting magnetism are dispersed in a plane direction and contained in a state aligned in a thickness direction,
The thickness is 10 to 100 μm, the number average particle diameter of the conductive particles exhibiting magnetism is 5 to 50 μm, and the ratio W ₁ / of the thickness W ₁ to the number average particle diameter D of the conductive particles exhibiting magnetism. An anisotropic conductive sheet, wherein D is 1.1 to 10, the content ratio of conductive particles exhibiting magnetism is 10 to 40% by weight, and is used for impedance measurement in a high frequency region. 2. The anisotropic conductive sheet according to claim 1, wherein the non-magnetic conductive material is contained in a uniformly dispersed state. In a sheet substrate made of an elastic polymer material, there are formed a plurality of conductive portions extending in a thickness direction in which conductive particles exhibiting magnetism are densely contained and an insulating portion for insulating the conductive portions from each other. An anisotropic conductive sheet,
The thickness of the conductive portion is 10 to 100 [mu] m, with a number average particle diameter of the conductive particles exhibiting magnetism is 5 to 50 [mu] m, the number average particle diameter D of the conductive particles exhibiting thickness W ₂ and the magnetic conductive portion The ratio W ₂ / D is 1.1 to 10, and the content of the conductive particles exhibiting magnetism in the conductive portion is 10 to 40% by weight and used for impedance measurement in a high frequency region. Anisotropic conductive sheet. 4. The anisotropic conductive sheet according to claim 3, wherein the conductive material having no magnetism is contained in a state where it is uniformly dispersed in the conductive part and the insulating part. The conductive part connected to the circuit to be measured of the substrate to be measured of the probe for impedance measurement and the conductive part connected to the ground circuit of the substrate to be measured are separated by an insulating part. The anisotropic conductive sheet according to claim 3 or 4. A probe for impedance measurement, comprising the anisotropic conductive sheet according to any one of claims 1 to 5, and used in a high-frequency region.

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