JP7277289B2 - Conductive material, connection structure, and method for manufacturing connection structure - Google Patents

Description

The present invention relates to conductive materials containing solder particles. The present invention also relates to a connection structure using the conductive material and a method for manufacturing the connection structure.

Solder pastes containing relatively large amounts of solder are known.

Also, anisotropic conductive materials are widely known that contain a relatively large amount of binder resin compared to solder paste. Examples of anisotropic conductive materials include anisotropic conductive pastes and anisotropic conductive films. In the anisotropic conductive material, conductive particles are dispersed in a binder resin. In the anisotropic conductive material, for example, two members can be bonded by the binder resin. Examples of the conductive particles include solder particles and particles containing a metal other than solder.

The anisotropic conductive material is used to obtain various connection structures. Examples of the connection using the anisotropic conductive material include connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), semiconductor Examples include connection between a chip and a glass substrate (COG (Chip on Glass)) and connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

For example, when electrically connecting electrodes of a flexible printed circuit board and electrodes of a glass epoxy board using the anisotropic conductive material, an anisotropic conductive material containing conductive particles is placed on the glass epoxy board. do. Next, the flexible printed circuit board is laminated and heated and pressurized. As a result, the anisotropic conductive material is cured and the electrodes are electrically connected via the conductive particles to obtain a connection structure.

Patent Document 1 below discloses a film containing (A) a phenoxy resin, (B) an epoxy resin, (C) a rubber and/or thermoplastic elastomer, (D) conductive particles, and (E) an imidazole-based latent curing agent. An anisotropically conductive adhesive is disclosed. The film-like anisotropically conductive adhesive satisfies the following requirements (a) and (b). (a) The lowest melt viscosity (V ₁ ) is 500 Pa or more and 1000 Pa or less. (b) The temperature (T ₁ ) at which the lowest melt viscosity is reached is 110° C. or higher and 125° C. or lower.

Patent Document 2 below discloses a solder paste composed of a mixture of solder powder and flux. In the solder paste, the solder powder has an average particle size of 4 μm to 20 μm. In the solder paste, a uniform oxide film is formed on the surface of the solder powder. In the solder paste, the solder powder has an oxygen content of 700 ppm to 3000 ppm.

JP 2012-234804 A JP-A-2000-094179

When conducting conductive connection using an anisotropic conductive material containing solder particles, a plurality of upper electrodes and a plurality of lower electrodes are electrically connected to form a conductive connection. Solder is preferably placed between the top and bottom electrodes and not between adjacent lateral electrodes. It is desirable that there is no electrical connection between adjacent lateral electrodes.

In general, an anisotropic conductive material containing solder particles is placed on a substrate and then heated by reflow or the like before use. When the anisotropic conductive material is heated to the melting point of the solder particles or higher, the solder particles melt and the solder aggregates between the electrodes, thereby electrically connecting the upper and lower electrodes.

With conventional anisotropic conductive materials, the speed at which solder particles move onto the electrodes (lines) is slow, and the solder may not be efficiently placed between the upper and lower electrodes to be connected. If the solder cannot be sufficiently agglomerated between the vertical electrodes to be connected, solder particles or the like may be left between the horizontal electrodes that should not be connected, separated from the solder between the vertical electrodes. It may remain as a side ball or the like. As a result, it may not be possible to sufficiently improve the reliability of conduction between electrodes that should be connected and the reliability of insulation between adjacent electrodes that should not be connected.

In addition, in manufacturing a conventional connected structure using an anisotropic conductive material, after placing the anisotropic conductive material between two members to be connected, the anisotropic conductive material is heated, and the melted solder is applied to the electrode. A step of aggregating upward (aggregation step) is performed, followed by a step of curing the resin component by heating (curing step). In manufacturing a connected structure using a conventional anisotropic conductive material, the curing process cannot be started until the aggregating process is sufficiently completed. Time can be long.

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive material capable of efficiently arranging solder on electrodes and effectively shortening the tact time in obtaining a connection structure. Another object of the present invention is to provide a connection structure using the conductive material and a method for manufacturing the connection structure.

According to a broad aspect of the present invention, a binder resin, a curing agent or curing accelerator, flux, and a plurality of solder particles are included, the oxygen concentration of the solder particles is xppm, and the amount of the flux per 100 parts by weight of the solder particles is Provided is a conductive material that satisfies the following formula (1) when the content is y parts by weight.

0.001x≦y≦0.012x Formula (1)

In a specific aspect of the conductive material according to the present invention, the solder particles have a particle diameter d50 of 50 μm or less.

In a specific aspect of the conductive material according to the present invention, the content of the solder particles is 10% by weight or more and 70% by weight or less in 100% by weight of the conductive material.

In a specific aspect of the conductive material according to the present invention, the resin curing rate of the reaction product is 70% or more when the conductive material is cured for 25 seconds under the following heating conditions.

Heating conditions for measuring resin curing rate:
0 to 5 seconds: Start heating the conductive material at 0° C., and set the temperature of the conductive material after 5 seconds to the melting point of the solder particles.

5 seconds to 15 seconds: The conductive material at the melting point of the solder particles is heated, and after 15 seconds the temperature of the conductive material is brought to the melting point of the solder particles +40°C.

15 seconds to 25 seconds: The conductive material having the melting point of the solder particles +40°C is held at the melting point of the solder particles +40°C.

In a specific aspect of the conductive material according to the present invention, the conductive material is conductive paste.

According to a broad aspect of the present invention, a first member to be connected having a first electrode on its surface, a second member to be connected having a second electrode on its surface, the first member to be connected, a connecting portion connecting the second member to be connected, wherein the material of the connecting portion is the conductive material described above, and the first electrode and the second electrode are connected to the connecting portion A connecting structure is provided that is electrically connected by a solder portion therein.

According to a broad aspect of the present invention, using the above-described conductive material, placing the conductive material on the surface of a first member to be connected having a first electrode on the surface; A second connection target member having a second electrode on its surface is arranged on the surface opposite to the first connection target member side such that the first electrode and the second electrode face each other. and heating the conductive material to a melting point of the solder particles or higher to form a connecting portion connecting the first member to be connected and the second member to be connected from the conductive material. and electrically connecting the first electrode and the second electrode with a solder portion in the connection portion.

In a specific aspect of the method for manufacturing a connected structure according to the present invention, pressure is not applied in the step of arranging the second member to be connected and the step of forming the connecting portion, and the conductive material is: The weight of the second member to be connected is applied, or pressure is applied in at least one of the step of arranging the second member to be connected and the step of forming the connecting portion, and In both the step of arranging the members to be connected in 2 and the step of forming the connecting portion, the pressure applied is less than 1 MPa.

A conductive material according to the present invention includes a binder resin, a curing agent or curing accelerator, flux, and a plurality of solder particles. The conductive material according to the present invention satisfies the above formula (1), where xppm is the oxygen concentration of the solder particles, and y parts is the content of the flux with respect to 100 parts by weight of the solder particles. Since the conductive material according to the present invention has the above configuration, it is possible to efficiently arrange the solder on the electrode, and to effectively shorten the tact time when obtaining the connection structure. be able to.

FIG. 1 is a cross-sectional view schematically showing a connected structure obtained using a conductive material according to one embodiment of the present invention. 2(a) to 2(c) are cross-sectional views for explaining steps of an example of a method of manufacturing a connection structure using a conductive material according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a modification of the connection structure.

The details of the present invention are described below.

(Conductive material)
A conductive material according to the present invention includes a binder resin, a curing agent or curing accelerator, flux, and a plurality of solder particles. The conductive material according to the present invention satisfies the following formula (1), where xppm is the oxygen concentration of the solder particles, and y parts by weight is the content of the flux with respect to 100 parts by weight of the solder particles.

0.001x≦y≦0.012x Formula (1)

Since the conductive material according to the present invention has the above configuration, it is possible to efficiently arrange the solder on the electrode, and to effectively shorten the tact time when obtaining the connection structure. be able to.

With conventional anisotropic conductive materials, the speed at which solder particles move onto the electrodes (lines) is slow, and the solder may not be efficiently placed between the upper and lower electrodes to be connected. If the solder cannot be sufficiently agglomerated between the vertical electrodes to be connected, solder particles or the like may be left between the horizontal electrodes that should not be connected, separated from the solder between the vertical electrodes. It may remain as a side ball or the like. As a result, it may not be possible to sufficiently improve the reliability of conduction between electrodes that should be connected and the reliability of insulation between adjacent electrodes that should not be connected.

In addition, in manufacturing a conventional connected structure using an anisotropic conductive material, after placing the anisotropic conductive material between two members to be connected, the anisotropic conductive material is heated, and the melted solder is applied to the electrode. A step of aggregating upward (aggregation step) is performed, followed by a step of curing the resin component by heating (curing step). In manufacturing a connected structure using a conventional anisotropic conductive material, the curing process cannot be started until the aggregating process is sufficiently completed. Time can be long.

The present inventors have found that by using a conductive material that satisfies a specific relationship between the oxygen concentration of solder particles and the content of flux, solder can be efficiently arranged on the electrode, and furthermore, the connection structure It has been found that the tact time can be effectively shortened when obtaining

In addition, in the present invention, a plurality of solder particles tend to gather between the upper and lower facing electrodes at the time of conductive connection between the electrodes, and a plurality of solder particles can be arranged on the electrodes (lines). Also, some of the plurality of solder particles are less likely to be placed between lateral electrodes that should not be connected, and the amount of solder particles placed between lateral electrodes that should not be connected can be significantly reduced. can. As a result, in the present invention, it is possible to prevent solder particles and the like from remaining as side balls and the like, effectively improve the reliability of conduction between the upper and lower electrodes to be connected, and further improve the connection reliability. Insulation reliability between adjacent electrodes, which should not be required, can be effectively improved.

In the present invention, the use of a conductive material that satisfies a specific relationship between the oxygen concentration of solder particles and the flux content greatly contributes to obtaining the effects described above.

Furthermore, according to the present invention, positional displacement between electrodes can be prevented. In the present invention, when the second connection target member is superimposed on the first connection target member having the conductive material disposed on the upper surface, the electrode of the first connection target member and the electrode of the second connection target member Even if the alignment is misaligned, the electrodes can be connected by correcting the misalignment (self-alignment effect).

From the viewpoint of shortening the tact time more effectively, the "0.001x ≤ y" part in the formula (1) is preferably "0.0011x ≤ y", more preferably "0.0012
x≦y”.

From the viewpoint of shortening the tact time more effectively, the “y ≤ 0.012x” part in the formula (1) is preferably “y ≤ 0.011x”, more preferably “y ≤ 0.01x”. be.

From the viewpoint of arranging the solder on the electrodes more efficiently, the conductive material is preferably liquid at 25° C., and is preferably a conductive paste. Preferably, the conductive material is a conductive paste at 25°C.

From the viewpoint of placing the solder on the electrode more efficiently, the viscosity (η25) of the conductive material at 25° C. is preferably 0.1 Pa s or more, more preferably 30 Pa s or more, and still more preferably It is 50 Pa·s or more, preferably 400 Pa·s or less, and more preferably 300 Pa·s or less. The viscosity (η25) can be appropriately adjusted depending on the types and amounts of ingredients to be blended.

The viscosity (η25) can be measured at 25° C. and 5 rpm using, for example, an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.).

The viscosity (ηmp) of the conductive material at the melting point of the solder particles is preferably 50 Pa·s or less, more preferably 10 Pa·s or less, still more preferably 1 Pa·s or less, and preferably 0.1 Pa·s or more. More preferably, it is 0.2 Pa·s or more. When the viscosity (ηmp) is equal to or less than the upper limit, the solder can be arranged on the electrodes more efficiently. When the viscosity is equal to or higher than the lower limit, it is possible to suppress the formation of voids at the connecting portion and suppress the protrusion of the conductive material to areas other than the connecting portion.

The above viscosity (ηmp) was measured using a STRESSTECH (manufactured by REOLOGICA) or the like using a distortion control of 1 rad, a frequency of 1 Hz, a temperature increase rate of 20°C/min, and a measurement temperature range of 25°C to 200°C (however, the liquidus line of the solder particles When the temperature (melting point) exceeds 200° C., the upper temperature limit is the liquidus temperature (melting point) of the solder particles). From the measurement results, the viscosity at the melting point (° C.) of the solder particles is evaluated.

When the conductive material is cured under the following heating conditions, the curing rate of the resin after 25 seconds is preferably 70% or more, more preferably 75% or more. When the said resin hardening rate is more than the said minimum, when obtaining a bonded structure, a tact time can be shortened further effectively.

Heating conditions for measuring resin curing rate:
0 seconds to 5 seconds: Start heating the conductive material at 0° C., and set the temperature of the conductive material after 5 seconds to the melting point of the solder particles.

5 seconds to 15 seconds: The conductive material at the melting point of the solder particles is heated, and after 15 seconds the temperature of the conductive material is brought to the melting point of the solder particles +40.degree.

15 seconds to 25 seconds: The conductive material having the melting point of the solder particles +40°C is held at the melting point of the solder particles +40°C.

From 0 seconds to 25 seconds, the conductive material is exposed to the above series of temperature conditions. The resin cure rate of the reactants is evaluated at 25 seconds under the above heating conditions.

The resin hardening rate is obtained by the following procedure.

Measurement of calorific value X: The conductive material is cured for 25 seconds under the above heating conditions to obtain a reactant. A resin portion is scraped from the obtained reactant to obtain a scraped sample. The machined sample is subjected to differential scanning calorimetry (DSC) to determine the heat generation amount X per unit weight associated with the heat generation peak. The differential scanning calorimetry is carried out by weighing about 5 mg of the scraped sample, mounting it on a container holder, heating at a heating rate of 10°C per minute, and measuring while heating from 30°C to 300°C. When the scraped sample contains an uncured component, an exothermic peak is observed as the uncured component cures.

Measurement of total calorific value Y: A resin having the same composition as the resin contained in the conductive material (a composition obtained by removing the solder particles from the conductive material) is prepared. Differential scanning calorimetry (DSC) is performed on the resin to measure the total calorific value Y per unit weight. The differential scanning calorimetry is performed under the conditions that about 5 mg of the resin is weighed out, mounted on a container holder, heated at a heating rate of 10°C per minute, and measured while being heated from 30°C to 300°C. An exothermic peak is observed as the resin cures.

Calculation of resin curing rate: The resin curing rate is calculated from the formula: (1−X/Y)×100.

The conductive material can be used as a conductive paste, a conductive film, and the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. From the viewpoint of arranging the solder on the electrodes more efficiently, the conductive material is preferably a conductive paste. The conductive material is suitably used for electrical connection of electrodes. The conductive material is preferably a circuit connecting material.

Each component contained in the conductive material will be described below.

(solder particles)
The conductive material includes solder particles. Both the central portion and the outer surface of the solder particles are formed of solder. The solder particles are particles in which both the central portion and the outer surface are solder. Instead of the solder particles, when using conductive particles comprising base particles made of a material other than solder and solder portions disposed on the surfaces of the base particles, conductive particles are formed on the electrodes. It becomes difficult for particles to gather. In addition, since the conductive particles have low solderability between the conductive particles, the conductive particles that have moved onto the electrodes tend to move out of the electrodes. tends to be low.

The solder is preferably a metal having a melting point of 450° C. or less (low melting point metal). The solder particles are preferably metal particles having a melting point of 450° C. or less (low-melting-point metal particles). The low-melting-point metal particles are particles containing a low-melting-point metal. The low-melting-point metal means a metal having a melting point of 450° C. or lower. The melting point of the low-melting-point metal is preferably 300° C. or lower, more preferably 220° C. or lower, and even more preferably 190° C. or lower. The solder particles are preferably low-melting solder having a melting point of less than 150.degree.

The melting point of the solder particles can be determined by differential scanning calorimetry (DSC). Examples of the differential scanning calorimeter (DSC) device include "EXSTAR DSC7020" manufactured by SII.

Also, the solder particles preferably contain tin. The content of tin in 100% by weight of the metal contained in the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. . When the content of tin in the solder particles is equal to or higher than the lower limit, the connection reliability between the solder portion and the electrode is further enhanced.

The tin content is measured using a high-frequency inductively coupled plasma atomic emission spectrometer ("ICP-AES" manufactured by Horiba Ltd.) or a fluorescent X-ray spectrometer ("EDX-800HS" manufactured by Shimadzu Corporation). can do.

By using the solder particles, the solder is melted and joined to the electrodes, and the solder portions conduct between the electrodes. For example, since the solder part and the electrode are likely to be in surface contact rather than point contact, the connection resistance is reduced. In addition, the use of the solder particles increases the bonding strength between the solder portion and the electrode, making it more difficult for the solder portion and the electrode to separate, thereby further increasing the conduction reliability and connection reliability.

The low-melting-point metal forming the solder particles is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. The alloys include tin-silver alloys, tin-copper alloys, tin-silver-copper alloys, tin-bismuth alloys, tin-zinc alloys, tin-indium alloys, and the like. The low-melting-point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy because of its excellent wettability with the electrode. More preferably, the low melting point metal is a tin-bismuth alloy or a tin-indium alloy.

The solder particles are preferably a filler material having a liquidus line of 450° C. or less based on JIS Z3001: Welding Terminology. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, and indium. A tin-indium system (117° C. eutectic) or a tin-bismuth system (139° C. eutectic), which have a low melting point and are lead-free, are preferred. That is, the solder particles preferably do not contain lead, and preferably contain tin and indium, or tin and bismuth.

In order to further increase the bonding strength between the solder part and the electrode, the solder particles contain nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, Metals such as molybdenum and palladium may also be included. Moreover, from the viewpoint of further increasing the bonding strength between the solder portion and the electrode, the solder particles preferably contain nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further increasing the bonding strength between the solder part and the electrode, the content of these metals for increasing the bonding strength is preferably 0.0001% by weight or more in 100% by weight of the metal contained in the solder particles. It is preferably 1% by weight or less.

The particle diameter d50 of the solder particles is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 50 μm or less, more preferably 45 μm or less. When the particle diameter d50 of the solder particles is equal to or more than the lower limit and equal to or less than the upper limit, the solder can be arranged on the electrode more efficiently. From the viewpoint of arranging the solder on the electrode more efficiently, it is particularly preferable that the particle diameter d50 of the solder particles is 2 μm or more and 40 μm or less.

The particle diameter d50 of the solder particles indicates a 50% cumulative value in particle size distribution, and is a value measured by a laser diffraction particle size distribution analyzer or the like. Examples of the laser diffraction particle size distribution analyzer include "LA-920" manufactured by Horiba Ltd., and the like.

Methods for adjusting the particle diameter d50 of the solder particles to the preferred range include a method of pulverizing the solder particles with a jet mill or the like, a sieving method with a sieve or the like, and the like.

The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 5% or more, more preferably 10% or more, and preferably 40% or less, more preferably 30% or less. When the coefficient of variation of the particle size of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder can be arranged on the electrode more efficiently. However, the CV value of the particle diameter of the solder particles may be less than 5%.

The coefficient of variation (CV value) can be measured as follows.

CV value (%) = (ρ/Dn) × 100
ρ: standard deviation of particle size of solder particles Dn: average value of particle size of solder particles

The shape of the solder particles is not particularly limited. The shape of the solder particles may be spherical, may be other than spherical, or may be flat.

It is preferable that the oxygen concentration of the solder particles is low. The oxygen concentration of the solder particles is preferably 2500 ppm or less, more preferably 2000 ppm or less. When the oxygen concentration of the solder particles is equal to or less than the upper limit, the solder characteristics can be improved more effectively, and the solder can be more efficiently arranged on the electrodes.

In order to reduce the oxygen concentration of the solder particles, it is effective to set the process of preparing the solder particles in an environment in which the solder particles are not easily oxidized, and to handle the produced solder particles in an environment in which the solder particles are not easily oxidized. be.

The oxygen concentration of the solder particles can be measured by a nitrogen/oxygen simultaneous analyzer (manufactured by Horiba Ltd., EMGA-650).

The content of the solder particles in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight or more, and particularly preferably 25% by weight or more. is 70% by weight or less, more preferably 65% by weight or less, and still more preferably 60% by weight or less. When the content of the solder particles is equal to or more than the lower limit and equal to or less than the upper limit, the solder can be arranged on the electrodes more efficiently, and it is easy to arrange a large amount of solder between the electrodes, and the conduction Reliability can be enhanced more effectively. From the standpoint of further improving conduction reliability, the content of the solder particles is preferably large.

(binder resin)
The conductive material includes a binder resin. The binder resin is not particularly limited. A known insulating resin is used as the binder resin. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include photocurable components and thermosetting components. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent as a curing agent.

The conductive material preferably contains a thermosetting compound and a thermosetting agent. The binder resin preferably contains a thermosetting compound. The conductive material preferably contains a curing accelerator. When the conductive material and the binder resin satisfy the above preferred aspects, the tact time can be shortened more effectively in obtaining a connected structure.

(binder resin: thermosetting compound)
The thermosetting compound is not particularly limited. Examples of the thermosetting compounds include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds and polyimide compounds. From the viewpoint of further improving the curability and viscosity of the conductive material, the viewpoint of further effectively improving the conduction reliability, and the viewpoint of further effectively improving the insulation reliability, the thermosetting compound is Epoxy compounds or episulfide compounds are preferred, and epoxy compounds are more preferred. The thermosetting compound preferably contains an epoxy compound. As for the said thermosetting compound, only 1 type may be used and 2 or more types may be used together.

The epoxy compound is a compound having at least one epoxy group. Examples of the epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, phenol novolac type epoxy compounds, biphenyl type epoxy compounds, biphenyl novolak type epoxy compounds, biphenol type epoxy compounds, and naphthalene type epoxy compounds. , fluorene type epoxy compound, phenol aralkyl type epoxy compound, naphthol aralkyl type epoxy compound, dicyclopentadiene type epoxy compound, anthracene type epoxy compound, epoxy compound having adamantane skeleton, epoxy compound having tricyclodecane skeleton, naphthylene ether type Epoxy compounds, epoxy compounds having a triazine core in the skeleton, and the like are included. Only one type of the epoxy compound may be used, or two or more types may be used in combination.

The epoxy compound is liquid or solid at normal temperature (23° C.), and when the epoxy compound is solid at normal temperature, the melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder. By using the above preferable epoxy compound, the viscosity is high at the stage of bonding the connection target members, and when acceleration is applied due to impact such as transportation, the first connection target member and the second connection Positional deviation from the target member can be suppressed. Furthermore, the heat during curing can greatly reduce the viscosity of the conductive material, allowing the cohesion of the solder to proceed efficiently.

From the viewpoint of more effectively improving insulation reliability and more effectively improving conduction reliability, the thermosetting compound preferably contains an epoxy compound.

From the viewpoint of arranging the solder on the electrode more efficiently, the thermosetting compound preferably contains a thermosetting compound having a polyether skeleton.

As the thermosetting compound having a polyether skeleton, a compound having a glycidyl ether group at both ends of an alkyl chain having 3 to 12 carbon atoms, and a polyether skeleton having 2 to 4 carbon atoms, the polyether skeleton Examples thereof include polyether type epoxy compounds having a structural unit in which 2 to 10 are continuously bonded.

From the viewpoint of more effectively increasing the heat resistance of the cured product, the thermosetting compound preferably contains a thermosetting compound having an isocyanuric skeleton.

Examples of the thermosetting compound having an isocyanurate skeleton include triisocyanurate type epoxy compounds, and the TEPIC series manufactured by Nissan Chemical Industries, Ltd. (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-PAS, TEPIC-VL, TEPIC-UC) and the like.

The content of the thermosetting compound in 100% by weight of the conductive material is preferably 5% by weight or more, more preferably 10% by weight or more, and preferably 85% by weight or less, more preferably 75% by weight or less, More preferably 65% by weight or less, particularly preferably 55% by weight or less. When the content of the thermosetting compound is the lower limit or more and the upper limit or less, the solder can be arranged on the electrodes more efficiently, and the insulation reliability between the electrodes can be more effectively improved. It is possible to further effectively improve the reliability of electrical connection between the electrodes. From the viewpoint of more effectively increasing the impact resistance, the content of the thermosetting compound is preferably large.

The content of the epoxy compound in 100% by weight of the conductive material is preferably 5% by weight or more, more preferably 10% by weight or more, preferably 85% by weight or less, more preferably 75% by weight or less, and even more preferably. is 65% by weight or less, particularly preferably 55% by weight or less. When the content of the epoxy compound is equal to or more than the lower limit and equal to or less than the upper limit, the solder can be arranged on the electrodes more efficiently, and the insulation reliability between the electrodes can be more effectively improved. It is possible to more effectively improve the reliability of electrical connection between the electrodes. From the viewpoint of further increasing the impact resistance, the content of the epoxy compound is preferably large.

(Curing agent: thermosetting agent)
The conductive material includes a curing agent or curing accelerator. The curing agent is not particularly limited. The curing agent is preferably a thermosetting agent. From the viewpoint of more effectively shortening the tact time when obtaining a connected structure, the conductive material preferably contains the thermosetting agent together with the thermosetting compound.

From the viewpoint of enabling the conductive material to be cured at a low temperature more rapidly, the thermosetting agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent. Moreover, from the viewpoint of enhancing storage stability when the thermosetting compound and the thermosetting agent are mixed, the thermosetting agent is preferably a latent curing agent. The latent curing agent is preferably a latent imidazole curing agent, a latent thiol curing agent or a latent amine curing agent. The thermosetting agent may be coated with a polymeric material such as polyurethane resin or polyester resin.

The imidazole curing agent is not particularly limited. Examples of the imidazole curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6. -[2′-methylimidazolyl-(1′)]-ethyl-s-triazine and 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine isocyanuric acid adducts , 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-p-toluyl-4-methyl-5 -5-position of 1H-imidazole in hydroxymethylimidazole, 2-methatoluyl-4-methyl-5-hydroxymethylimidazole, 2-methatoluyl-4,5-dihydroxymethylimidazole, 2-paratoluyl-4,5-dihydroxymethylimidazole, etc. and the hydrogen at the 2-position is substituted with a hydroxymethyl group and the hydrogen at the 2-position with a phenyl group or a toluyl group.

The thiol curing agent is not particularly limited. Examples of the thiol curing agent include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate and dipentaerythritol hexa-3-mercaptopropionate.

The amine curing agent is not particularly limited. Examples of the amine curing agent include hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4 -aminocyclohexyl)methane, metaphenylenediamine and diaminodiphenylsulfone.

The acid anhydride curing agent is not particularly limited, and a wide range of acid anhydrides can be used as long as they are used as curing agents for thermosetting compounds such as epoxy compounds. Examples of the acid anhydride curing agent include phthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and methylbutenyltetrahydrophthalic anhydride. , anhydrides of phthalic acid derivatives, maleic anhydride, nadic anhydride, methyl nadic anhydride, glutaric anhydride, succinic anhydride, glycerin bis trimellitic anhydride monoacetate, and ethylene glycol bis trimellitic anhydride. acid anhydride curing agent, trifunctional acid anhydride curing agent such as trimellitic anhydride, and pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methylcyclohexene tetracarboxylic anhydride, polyazelaic anhydride, etc. and a tetrafunctional or higher acid anhydride curing agent.

The thermal cationic initiator is not particularly limited. Examples of the thermal cationic initiator include iodonium-based cationic curing agents, oxonium-based cationic curing agents, and sulfonium-based cationic curing agents. Examples of the iodonium cationic curing agent include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. Examples of the oxonium cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

The thermal radical generator is not particularly limited. Examples of the thermal radical generator include azo compounds and organic peroxides. Examples of the azo compound include azobisisobutyronitrile (AIBN). Examples of the organic peroxide include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

The reaction initiation temperature of the thermosetting agent is preferably 50°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, preferably 250°C or lower, more preferably 200°C or lower, and still more preferably 150°C. Below, it is 140 degrees C or less especially preferably. When the reaction initiation temperature of the thermosetting agent is equal to or higher than the lower limit and equal to or lower than the upper limit, the solder can be arranged on the electrode more efficiently, and the tact time can be further reduced when obtaining a connection structure. can be shortened effectively. From the viewpoint of further effectively shortening the tact time when obtaining the bonded structure, the reaction initiation temperature of the thermosetting agent is particularly preferably 80° C. or higher and 140° C. or lower.

From the viewpoint of arranging the solder on the electrode more efficiently, the reaction initiation temperature of the thermosetting agent is preferably higher than the melting point of the solder particles, more preferably 5 ° C. or higher, and 10 ° C. more preferably higher than

The reaction start temperature of the thermosetting agent means the temperature at which the exothermic peak starts to rise in DSC. Examples of the DSC apparatus include "EXSTAR DSC7020" manufactured by SII.

The content of the thermosetting agent is not particularly limited. With respect to 100 parts by weight of the thermosetting compound, the content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably It is 100 parts by weight or less, more preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the lower limit, it is easy to sufficiently cure the conductive material. When the content of the thermosetting agent is equal to or less than the above upper limit, it becomes difficult for excess thermosetting agent that has not been involved in curing to remain after curing, and the heat resistance of the cured product is further enhanced.

(Curing accelerator)
The conductive material includes a curing agent or curing accelerator. The curing accelerator is not particularly limited. The curing accelerator preferably acts as a curing catalyst in the reaction between the thermosetting compound and the thermosetting agent. The curing accelerator preferably acts as a curing catalyst in the reaction with the thermosetting compound. Only one kind of the curing accelerator may be used, or two or more kinds thereof may be used in combination.

Examples of the curing accelerator include phosphonium salts, tertiary amines, tertiary amine salts, quaternary onium salts, tertiary phosphines, crown ether complexes, and phosphonium ylides. Specifically, the curing accelerator includes imidazole compounds, isocyanurates of imidazole compounds, dicyandiamide, dicyandiamide derivatives, melamine compounds, melamine compound derivatives, diaminomaleonitrile, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. , bis(hexamethylene)triamine, triethanolamine, diaminodiphenylmethane, amine compounds such as organic acid dihydrazide, 1,8-diazabicyclo[5,4,0]undecene-7,3,9-bis(3-aminopropyl) -2,4,8,10-tetraoxaspiro[5,5]undecane, boron trifluoride, and organophosphorus compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine and methyldiphenylphosphine.

The phosphonium salt is not particularly limited. Examples of the phosphonium salts include tetra-butylphosphonium bromide, tetra-butylphosphonium O,O-diethyldithiophosphate, methyltributylphosphonium dimethylphosphate, tetra-butylphosphonium benzotriazole, tetra-butylphosphonium tetrafluoroborate, and tetra-normal butylphosphonium tetraphenylborate and the like.

The content of the curing accelerator is appropriately selected so that the thermosetting compound cures satisfactorily. The content of the curing accelerator with respect to 100 parts by weight of the thermosetting compound is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more, preferably 10 parts by weight or less, more preferably 8 parts by weight. Part by weight or less. When the content of the curing accelerator is equal to or more than the lower limit and equal to or less than the upper limit, the thermosetting compound can be cured satisfactorily.

(flux)
The conductive material includes flux. By using flux, the solder can be more efficiently placed on the electrodes. The above flux is not particularly limited. Flux generally used for soldering or the like can be used as the flux.

Examples of the flux include zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, phosphoric acid derivatives, organic halides, hydrazine, amine compounds, organic acids and pine resin and the like. Only one kind of the above flux may be used, or two or more kinds thereof may be used in combination.

Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid and glutaric acid. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably an organic acid having two or more carboxyl groups, or rosin. The flux may be an organic acid having two or more carboxyl groups, or may be rosin. The use of rosin, an organic acid having two or more carboxyl groups, further enhances the reliability of electrical connection between electrodes.

Examples of the organic acid having two or more carboxyl groups include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

Examples of the amine compound include cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

The pine resin is a rosin containing abietic acid as a main component. Examples of the rosins include abietic acid and acryl-modified rosins. The flux is preferably rosins, more preferably abietic acid. The use of this preferable flux further enhances the reliability of electrical connection between the electrodes.

The active temperature (melting point) of the flux is preferably 50° C. or higher, more preferably 70° C. or higher, still more preferably 80° C. or higher, preferably 200° C. or lower, more preferably 190° C. or lower, and even more preferably 160° C. °C or less, more preferably 150°C or less, and even more preferably 140°C or less. When the activation temperature of the flux is equal to or higher than the lower limit and equal to or lower than the upper limit, the flux effect is exhibited more effectively, and the solder can be arranged on the electrode more efficiently. The active temperature (melting point) of the flux is preferably 80° C. or higher and 190° C. or lower. It is particularly preferable that the flux has an activation temperature (melting point) of 80° C. or higher and 140° C. or lower.

Examples of the above fluxes having an activation temperature (melting point) of 80° C. or more and 190° C. or less include succinic acid (melting point 186° C.), glutaric acid (melting point 96° C.), adipic acid (melting point 152° C.), pimelic acid (melting point 104° C.). ° C.), dicarboxylic acids such as suberic acid (melting point 142° C.), benzoic acid (melting point 122° C.), and malic acid (melting point 130° C.).

Also, the boiling point of the flux is preferably 200° C. or lower.

From the viewpoint of arranging the solder on the electrode more efficiently, the melting point of the flux is preferably higher than the melting point of the solder particles, more preferably 5° C. or higher, and 10° C. or higher. More preferred.

From the viewpoint of arranging the solder on the electrode more efficiently, the melting point of the flux is preferably higher than the reaction initiation temperature of the thermosetting agent, more preferably 5° C. or higher, and 10° C. or higher. Higher is more preferred.

The flux may be dispersed in the conductive material or adhered to the surfaces of the solder particles.

Since the melting point of the flux is higher than the melting point of the solder particles, the solder particles can be efficiently agglomerated on the electrode portion. This is because when heat is applied during bonding, the thermal conductivity of the electrode formed on the member to be connected and the portion of the member to be connected around the electrode are compared. This is due to the rapid temperature rise of the electrode portion due to the higher thermal conductivity. When the melting point of the solder particles is exceeded, the inside of the solder particles melts, but the oxide film formed on the surface is not removed because it has not reached the melting point (activation temperature) of the flux. In this state, the temperature of the electrode portion first reaches the melting point (activation temperature) of the flux, so the oxide film on the surface of the solder particles preferentially moved onto the electrode is removed, and the solder particles are deposited on the surface of the electrode. It can be spread wet. Thereby, the solder particles can be efficiently agglomerated on the electrode.

The flux is preferably a flux that releases cations when heated. The use of a flux that releases cations upon heating allows for much more efficient placement of the solder on the electrodes.

Examples of the flux that releases cations upon heating include the thermal cationic initiator (thermal cationic curing agent).

From the viewpoints of more efficiently arranging the solder on the electrode, more effectively improving the insulation reliability, and more effectively improving the conduction reliability, the above-mentioned flux contains an acid compound and a base compound. It is preferably a salt with.

The acid compound is preferably an organic compound having a carboxyl group. Examples of the acid compound include aliphatic carboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, malic acid, and cycloaliphatic carboxylic acids. Examples include cyclohexylcarboxylic acid, 1,4-cyclohexyldicarboxylic acid, isophthalic acid which is an aromatic carboxylic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid. From the viewpoints of more efficiently arranging the solder on the electrode, more effectively improving the insulation reliability, and more effectively improving the conduction reliability, the above acid compounds include glutaric acid, cyclohexyl Carboxylic acid or adipic acid is preferred.

The basic compound is preferably an organic compound having an amino group. Examples of the base compound include diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine. , N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N,N-dimethylbenzylamine, imidazole compounds, and triazole compounds. . From the viewpoint of more efficiently arranging solder on the electrode, more effectively improving insulation reliability, and more effectively improving conduction reliability, the base compound is benzylamine. is preferred.

The flux content in 100% by weight of the conductive material is preferably 0.5% by weight or more, preferably 30% by weight or less, and more preferably 25% by weight or less. When the content of the flux is at least the lower limit and at most the upper limit, it becomes more difficult to form an oxide film on the surface of the solder and the electrode, and furthermore, the oxide film formed on the surface of the solder and the electrode is further removed. can be removed effectively.

(filler)
The conductive material according to the present invention may contain filler. The filler may be an organic filler or an inorganic filler. By including the filler in the conductive material, the solder can be more uniformly agglomerated on all the electrodes of the substrate. In addition, since the conductive material contains a filler, the solder particles can be more uniformly dispersed in the conductive material.

Preferably, the conductive material does not contain the filler, or contains the filler in an amount of 5% by weight or less. When the above thermosetting compound is used, the smaller the content of the filler, the easier it is for the solder to move onto the electrode.

In 100% by weight of the conductive material, the content of the filler is preferably 0% by weight (not included) or more, preferably 5% by weight or less, more preferably 2% by weight or less, and further preferably 1% by weight or less. is. When the content of the filler is equal to or more than the lower limit and equal to or less than the upper limit, the solder is evenly arranged on the electrode.

(other ingredients)
The above-mentioned conductive material may optionally include fillers, extenders, softeners, plasticizers, thixotropic agents, leveling agents, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, , ultraviolet absorbers, lubricants, antistatic agents and flame retardants.

(Connection structure and method for manufacturing the connection structure)
A connection structure according to the present invention includes a first connection object member having a first electrode on the surface, a second connection object member having a second electrode on the surface, the first connection object member, and a connecting portion connecting the second member to be connected. In the connection structure according to the present invention, the material of the connection portion is the above-described conductive material. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

A method for manufacturing a connected structure according to the present invention includes the step of placing the conductive material on the surface of the first member to be connected having the first electrode on the surface thereof, using the conductive material described above. In the method for manufacturing a connected structure according to the present invention, a second member to be connected having a second electrode on the surface thereof is formed on the surface of the conductive material opposite to the first member to be connected. A step of arranging the one electrode and the second electrode so as to face each other. In the method for manufacturing a connected structure according to the present invention, the first member to be connected and the second member to be connected are connected by heating the conductive material to the melting point of the solder particles or higher. forming a section from the conductive material, and electrically connecting the first electrode and the second electrode by a solder section in the connecting section.

In the connection structure and the method for manufacturing the connection structure according to the present invention, since the specific conductive material is used, the solder tends to gather between the first electrode and the second electrode, and the solder can be applied to the electrodes (lines). can be efficiently placed on Also, part of the solder is less likely to be placed in the regions (spaces) where the electrodes are not formed, and the amount of solder placed in the regions where the electrodes are not formed can be considerably reduced. Therefore, reliability of conduction between the first electrode and the second electrode can be improved. Moreover, it is possible to prevent electrical connection between laterally adjacent electrodes, which should not be connected, and improve insulation reliability.

Also, in order to efficiently dispose the solder on the electrodes and considerably reduce the amount of solder disposed in areas where no electrodes are formed, the conductive material is not a conductive film but a conductive paste. is preferred.

The thickness of the solder portion between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder-wetting area on the surface of the electrode (the area in contact with solder in 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

In the method for manufacturing a connected structure according to the present invention, pressure is not applied in the step of arranging the second member to be connected and the step of forming the connecting portion, and the second connection is not applied to the conductive material. Preferably, the weight of the target member is added. In the method for manufacturing a connected structure according to the present invention, in at least one of the step of arranging the second member to be connected and the step of forming the connecting portion, pressure is applied and the second connection is formed. It is preferable that the pressure applied is less than 1 MPa in both the step of arranging the target member and the step of forming the connecting portion. By not applying a pressure of 1 MPa or more, the agglomeration of the solder particles is considerably promoted. When pressure is applied, the pressure may be applied only in the step of arranging the second member to be connected, or may be applied only in the step of forming the connecting portion. Pressurization may be performed in both the step of arranging the member to be connected and the step of forming the connecting portion. The case where the pressurization pressure is less than 1 MPa includes the case where no pressurization is applied. When applying pressure, the pressure is preferably 0.9 MPa or less, more preferably 0.8 MPa or less. When the applied pressure is 0.8 MPa or less, aggregation of the solder particles is promoted more significantly than when the applied pressure exceeds 0.8 MPa.

In the method for manufacturing a connected structure according to the present invention, pressure is not applied in the step of arranging the second member to be connected and the step of forming the connecting portion, and the second connection is not applied to the conductive material. Preferably, the weight of the target member is added. In the method for manufacturing a connected structure according to the present invention, in the step of arranging the second member to be connected and the step of forming the connecting portion, the conductive material does not have the force of the weight of the second member to be connected. It is preferable not to apply a pressure exceeding . In these cases, it is possible to further improve the uniformity of the amount of solder in the plurality of solder portions. Furthermore, the thickness of the solder portion can be increased more effectively, so that more solder can easily gather between the electrodes, and the solder can be more efficiently arranged on the electrodes (lines). Also, part of the solder is less likely to be placed in the regions (spaces) where the electrodes are not formed, and the amount of solder placed in the regions where the electrodes are not formed can be further reduced. Therefore, it is possible to further improve the reliability of electrical connection between the electrodes. Moreover, it is possible to further prevent electrical connection between laterally adjacent electrodes that should not be connected, thereby further enhancing insulation reliability.

Also, if a conductive paste is used instead of a conductive film, it becomes easier to adjust the thickness of the connecting portion and the solder portion by adjusting the amount of the conductive paste applied. On the other hand, with the conductive film, in order to change or adjust the thickness of the connection part, there is a problem that it is necessary to prepare conductive films with different thicknesses or prepare conductive films with a predetermined thickness. There is Moreover, in the conductive film, the melt viscosity of the conductive film cannot be sufficiently lowered at the melting temperature of the solder compared to the conductive paste, and the aggregation of the solder tends to be easily inhibited.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a connected structure obtained using a conductive material according to one embodiment of the present invention.

A connection structure 1 shown in FIG. a part 4; The connecting portion 4 is made of the conductive material described above. In this embodiment, the conductive material includes a binder resin, a curing agent or curing accelerator, flux, and a plurality of solder particles. The binder resin contains a thermosetting compound. In this embodiment, a conductive paste is used as the conductive material.

The connection portion 4 has a solder portion 4A in which a plurality of solder particles are gathered and joined together, and a cured product portion 4B in which a thermosetting component is thermally cured.

The first connection target member 2 has a plurality of first electrodes 2a on its surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on its surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by a solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by the solder portion 4A. In the connection portion 4, solder does not exist in a region (cured material portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a. In a region different from the solder portion 4A (hardened material portion 4B portion), there is no solder separate from the solder portion 4A. As long as the amount is small, the solder may exist in a region (cured material portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a. In addition, it is preferable that the solder wets and spreads on the surfaces of the electrodes, and the solder does not necessarily have to be collected between the upper and lower electrodes.

As shown in FIG. 1, in the connection structure 1, a plurality of solder particles gather between the first electrode 2a and the second electrode 3a. Wet and spread the surface of the electrode and then solidify to form the solder portion 4A. Therefore, the connection areas between the solder portion 4A and the first electrode 2a and between the solder portion 4A and the second electrode 3a are increased. That is, by using solder particles, the solder portion 4A and the first electrode 2a, as well as the solder portion, are compared with the case where the conductive outer surface is a metal such as nickel, gold or copper. The contact area between 4A and the second electrode 3a is increased. This also increases the conduction reliability and connection reliability in the connection structure 1 . In addition, when flux is contained in the conductive material, the flux is generally gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 1, all of the solder portions 4A are located in the opposing regions between the first and second electrodes 2a and 3a. A connection structure 1X of a modification shown in FIG. 3 differs from the connection structure 1 shown in FIG. 1 only in connection portions 4X. The connection portion 4X has a solder portion 4XA and a cured product portion 4XB. Like the connection structure 1X, most of the solder portion 4XA is located in the region where the first and second electrodes 2a and 3a face each other, and part of the solder portion 4XA is located between the first and second electrodes 2a and 3a. It may protrude laterally from the regions where the electrodes 2a and 3a face each other. The solder portion 4XA protruding laterally from the regions where the first and second electrodes 2a and 3a face each other is a part of the solder portion 4XA and is not solder separate from the solder portion 4XA. In this embodiment, the amount of solder separated from the solder portion can be reduced, but the solder separated from the solder portion may exist in the cured product portion.

If the amount of solder particles used is reduced, it becomes easier to obtain the connection structure 1 . If the amount of solder particles used is increased, it becomes easier to obtain the connection structure 1X.

In the connection structures 1, 1X, when the first electrode 2a, the connection portion 4, 4X, and the second electrode 3a are stacked in the direction in which the first electrode 2a and the second electrode 3a face each other, Furthermore, it is preferable that the solder portions 4A and 4XA in the connection portions 4 and 4X are arranged in 50% or more of the 100% area of the portion where the first electrode 2a and the second electrode 3a face each other. . When the solder portions 4A and 4XA in the connection portions 4 and 4X satisfy the above preferred aspects, the electrical connection reliability can be further improved.

When the facing portion of the first electrode and the second electrode is viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode It is preferable that the solder portion in the connection portion is arranged in 50% or more of 100% of the area of the portion facing the two electrodes. When the facing portion of the first electrode and the second electrode is viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode More preferably, the solder portion in the connecting portion is arranged in 60% or more of 100% of the area of the portion facing the two electrodes. When the facing portion of the first electrode and the second electrode is viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode More preferably, the solder portion in the connection portion is arranged in 70% or more of 100% of the area of the portion facing the two electrodes. When the facing portion of the first electrode and the second electrode is viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode It is particularly preferable that the solder portion in the connection portion is arranged in 80% or more of 100% of the area of the portion facing the two electrodes. When the facing portion of the first electrode and the second electrode is viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode It is most preferable that the solder portion in the connection portion is arranged in 90% or more of 100% of the area of the portion facing the two electrodes. When the solder portion in the connection portion satisfies the above-mentioned preferred aspects, the reliability of conduction can be further improved.

When a portion of the first electrode and the second electrode facing each other is viewed in a direction orthogonal to the lamination direction of the first electrode, the connecting portion, and the second electrode, the first electrode It is preferable that 60% or more of the solder portion in the connection portion is arranged in the portion where the electrode and the second electrode face each other. When a portion of the first electrode and the second electrode facing each other is viewed in a direction orthogonal to the lamination direction of the first electrode, the connecting portion, and the second electrode, the first electrode More preferably, 70% or more of the solder portion in the connection portion is arranged in the portion where the electrode and the second electrode face each other. When a portion of the first electrode and the second electrode facing each other is viewed in a direction orthogonal to the lamination direction of the first electrode, the connecting portion, and the second electrode, the first electrode More preferably, 90% or more of the solder portion in the connection portion is arranged in the portion where the electrode and the second electrode face each other. When a portion of the first electrode and the second electrode facing each other is viewed in a direction orthogonal to the lamination direction of the first electrode, the connecting portion, and the second electrode, the first electrode It is particularly preferable that 95% or more of the solder portion in the connection portion is arranged in the portion where the electrode and the second electrode face each other. When a portion of the first electrode and the second electrode facing each other is viewed in a direction orthogonal to the lamination direction of the first electrode, the connecting portion, and the second electrode, the first electrode Most preferably, 99% or more of the solder portion in the connecting portion is arranged in the portion where the electrode and the second electrode face each other. When the solder portion in the connection portion satisfies the above-mentioned preferred aspects, the reliability of conduction can be further improved.

Next, with reference to FIG. 2, an example of a method of manufacturing the connection structure 1 using the conductive material according to one embodiment of the present invention will be described.

First, a first member to be connected 2 having a first electrode 2a on its surface (upper surface) is prepared. Next, as shown in FIG. 2(a), a conductive solder containing a binder resin 11B, a curing agent or a curing accelerator, flux, and a plurality of solder particles 11A is formed on the surface of the first member 2 to be connected. A material 11 is placed (first step, first placement step). The conductive material 11 used contains a thermosetting compound as the binder resin 11B. In this embodiment, the conductive material 11 is a conductive paste.

A conductive material 11 is arranged on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the placement of the conductive material 11, the solder particles 11A are placed both on the first electrodes 2a (lines) and on the regions (spaces) where the first electrodes 2a are not formed.

The method of arranging the conductive material 11 is not particularly limited, but examples thereof include application using a dispenser, screen printing, and ejection using an inkjet device.

Also, a second connection object member 3 having a second electrode 3a on its surface (lower surface) is prepared. Next, as shown in FIG. 2(b), on the surface of the conductive material 11 on the surface of the first connection target member 2, on the surface opposite to the first connection target member 2 side of the conductive material 11, A second member to be connected 3 is placed (second step, second placement step). The second member 3 to be connected is arranged on the surface of the conductive material 11 from the side of the second electrode 3a. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

Next, the conductive material 11 is heated above the melting point of the solder particles 11A (third step, connecting step). Preferably, the conductive material 11 is heated to a curing temperature of the binder resin 11B (thermosetting compound) or higher. During this heating, the solder particles 11A existing in the regions where no electrodes are formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). When a conductive paste is used instead of the conductive film, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. Also, the solder particles 11A are melted and joined together. Also, the binder resin 11B is thermally cured. As a result, as shown in FIG. 2(c), the connecting portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed of the conductive material 11. Next, as shown in FIG. A connection portion 4 is formed of the conductive material 11, a solder portion 4A is formed by joining a plurality of solder particles 11A, and a hardened material portion 4B is formed by thermosetting the binder resin 11B. If the solder particles 11A move sufficiently, the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a start to move, and then the first electrode 2a and the second electrode It is not necessary to keep the temperature constant until the movement of the solder particles 11A between the solder particles 3a is completed.

In the present embodiment, it is preferable not to pressurize in the second step and the third step. In this case, the weight of the second member 3 to be connected is added to the conductive material 11 . Therefore, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a when forming the connecting portion 4. As shown in FIG. In at least one of the second step and the third step, when pressure is applied, the solder particles 11A tend to gather between the first electrode 2a and the second electrode 3a. are more likely to be inhibited.

Further, in this embodiment, since no pressure is applied, the first connection target member 2 and the second connection target member 3 are connected in a state in which the first electrode 2a and the second electrode 3a are out of alignment. are superimposed on each other, the deviation can be corrected and the first electrode 2a and the second electrode 3a can be connected (self-alignment effect). This is because the molten solder that is self-coalescing between the first electrode 2a and the second electrode 3a is replaced by the solder and other conductive material between the first electrode 2a and the second electrode 3a. This is because the energy is more stable when the area in contact with the component is minimized, and a force is applied to the aligned connection structure, which is the connection structure with the minimum area. At this time, it is desirable that the conductive material is not hardened and that the viscosity of the components other than the solder particles of the conductive material is sufficiently low at that temperature and time.

Thus, the connection structure 1 shown in FIG. 1 is obtained. Note that the second step and the third step may be performed continuously. Further, after performing the second step, the obtained laminate of the first connection object member 2, the conductive material 11, and the second connection object member 3 is moved to the heating unit, and the third step is performed. process may be performed. To perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

The heating temperature in the third step is preferably 140° C. or higher, more preferably 160° C. or higher, and preferably 450° C. or lower, more preferably 250° C. or lower, still more preferably 200° C. or lower.

The heating method in the third step includes a method of heating the entire connection structure using a reflow furnace or an oven to a temperature above the melting point of the solder and above the curing temperature of the binder resin, or a method of heating the connection structure. A method of locally heating only a portion can be mentioned.

Tools used in the local heating method include a hot plate, a heat gun that applies hot air, a soldering iron, an infrared heater, and the like.

Also, when locally heating with a hot plate, use a metal with high thermal conductivity just below the connection part, and use a material with low thermal conductivity such as fluororesin for other places that are not desirable to heat. , preferably forming a hot plate top surface.

The first and second members to be connected are not particularly limited. Specifically, the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors and diodes, resin films, printed boards, flexible printed boards, flexible Examples include electronic components such as circuit boards such as flat cables, rigid flexible boards, glass epoxy boards and glass boards. The first and second members to be connected are preferably electronic components.

At least one of the first member to be connected and the second member to be connected is preferably a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. It is preferable that the second member to be connected is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Resin films, flexible printed boards, flexible flat cables, and rigid flexible boards have properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such members to be connected, solder tends to be less likely to gather on the electrodes. On the other hand, by using a conductive paste, even if a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board is used, by efficiently collecting solder on the electrodes, the reliability of the conduction between the electrodes can be improved. can be sufficiently increased. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, compared to the case of using other connection target members such as semiconductor chips, the conduction reliability between electrodes is improved by not applying pressure. An improvement effect can be obtained more effectively.

The electrodes provided on the connection object members include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the member to be connected is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode made of only aluminum, or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal elements include Sn, Al and Ga.

In the connection structure according to the present invention, it is preferable that the first electrode and the second electrode are arranged in an area array or a peripheral. The effects of the present invention are exhibited more effectively when the first electrode and the second electrode are arranged in an area array or peripheral arrangement. The area array is a structure in which electrodes are arranged in a grid pattern on the surface of the member to be connected where the electrodes are arranged. The peripheral is a structure in which electrodes are arranged on the outer periphery of the member to be connected. In the case of the structure in which the electrodes are arranged in a comb shape, the solder should be aggregated along the direction perpendicular to the comb. The solder should agglomerate uniformly. Therefore, in the conventional method, the amount of solder tends to be non-uniform, whereas in the method of the present invention, the solder can be uniformly aggregated over the entire surface.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. The invention is not limited only to the following examples.

Binder resin:
Thermosetting compound 1: Bisphenol F type epoxy resin, "DER354" manufactured by DOW
Thermosetting compound 2: bisphenol A type epoxy resin, manufactured by DIC "EXA-850CRP"
Thermosetting compound 3: Phenol novolac type epoxy compound, "DEN431" manufactured by DOW

Hardener:
Curing agent 1: latent microencapsulated imidazole curing agent, "Novacure HX3941HP" manufactured by Asahi Kasei Chemicals

Curing accelerator:
Curing accelerator 1: boron trifluoride, "boron trifluoride ethylamine complex" manufactured by Aldrich

flux:
Flux 1: "Glutaric acid benzylamine salt", melting point 108°C, solid at 23°C Method of making Flux 1:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved at room temperature until uniform. After that, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed liquid. The resulting mixture was placed in a refrigerator at 5°C to 10°C and allowed to stand overnight. Precipitated crystals were separated by filtration, washed with water, and dried in a vacuum to obtain a flux 1.

Flux 2: "benzylamine adipate", melting point 171°C, solid at 23°C Method of making Flux 2:
24 g of water as a reaction solvent and 13.89 g of adipic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved at room temperature until uniform. After that, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed liquid. The resulting mixture was placed in a refrigerator at 5°C to 10°C and allowed to stand overnight. Precipitated crystals were collected by filtration, washed with water, and dried in a vacuum to obtain a flux 2.

Solder particles:
Solder particles 1: SnBi solder particles, melting point 139° C., "Sn42Bi58" manufactured by Mitsui Mining & Smelting Co., Ltd. was selected to prepare solder particles having a particle diameter d50 of 2 μm and an oxygen concentration of 1500 ppm.
Solder particles 2: SnBi solder particles, melting point 139° C., "Sn42Bi58" manufactured by Mitsui Mining & Smelting Co., Ltd. was selected to prepare solder particles having a particle diameter d50 of 13 μm and an oxygen concentration of 300 ppm.
Solder particles 3: SnAgCu solder particles, melting point 217° C., "SnAg3Cu0.5" manufactured by Mitsui Mining & Smelting Co., Ltd. was selected to prepare solder particles having a particle diameter d50 of 2 μm and an oxygen concentration of 1300 ppm.
Solder particles 4: SnAgCu solder particles, melting point 217° C., "SnAg3Cu0.5" manufactured by Mitsui Mining & Smelting Co., Ltd. was selected to prepare solder particles having a particle diameter d50 of 13 μm and an oxygen concentration of 270 ppm.

(Examples 1 to 17 and Comparative Examples 1 to 3)
(1) Preparation of conductive material (anisotropic conductive paste) The components shown in Tables 1 to 3 below are blended in the amounts shown in Tables 1 to 3 below to obtain a conductive material (anisotropic conductive paste). rice field.

(2) Fabrication of connection structure As the first member to be connected, a glass epoxy substrate (FR -4 substrate, thickness 0.6 mm) was prepared.

As a second member to be connected, a flexible printed circuit board (made of polyimide, thickness 0.1 mm) having a copper electrode pattern (L/S: 50 μm/50 μm, electrode length: 3 mm, electrode thickness: 12 μm) on the lower surface. prepared.

A conductive material (anisotropic conductive paste) immediately after production was applied to the upper surface of the glass epoxy substrate so as to have a thickness of 100 μm to form a conductive material (anisotropic conductive paste) layer. Next, a flexible printed circuit board was laminated on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes faced each other. The weight of the flexible printed circuit board is added to the conductive material (anisotropic conductive paste) layer. Heating was performed under the following heating conditions to cure the conductive material (anisotropic conductive paste) layer, thereby obtaining a connection structure. No pressure was applied during heating.

Heating conditions:
0 seconds to 5 seconds: Start heating the conductive material at 0° C., and set the temperature of the conductive material after 5 seconds to the melting point of the solder particles.

5 seconds to 15 seconds: The conductive material at the melting point of the solder particles is heated, and after 15 seconds the temperature of the conductive material is brought to the melting point of the solder particles +40.degree.

15 seconds to 25 seconds: The conductive material having the melting point +40° C. of the solder particles is held at the melting point +40° C. of the solder particles.

(evaluation)
(1) Relationship between oxygen concentration x of solder particles and flux content y per 100 parts by weight of solder particles For the obtained conductive material, the oxygen concentration of the solder particles is xppm, and the flux content per 100 parts by weight of solder particles. is y parts by weight, it was confirmed whether the following formula (1) is satisfied. The relationship between the oxygen concentration of the solder particles and the flux content per 100 parts by weight of the solder particles was evaluated according to the following criteria.

0.001x≦y≦0.012x Formula (1)

[Criteria for determining the relationship between the oxygen concentration x of the solder particles and the flux content y per 100 parts by weight of the solder particles]
○: The conductive material satisfies the above formula (1) ×: The conductive material does not satisfy the above formula (1)

(2) Cohesiveness of Solder In the obtained connection structure, the ratio of the number of first electrodes or second electrodes on which solder is arranged to 100% of the number of first electrodes and second electrodes X was rated. The cohesiveness of solder was judged according to the following criteria.

[Criteria for determination of cohesiveness of solder]
○○○: Proportion X is 90% or more ○○: Proportion X is 70% or more and less than 90% ×: Proportion X is less than 70%

(3) Solder Wetting Area In the obtained connection structure, the ratio Y of the area in contact with the solder to the 100% exposed area of the first electrode and the second electrode was evaluated. The solder wetted area was determined according to the following criteria.

[Criteria for Solder Wetting Area]
○○○: Proportion Y is 90% or more ○○: Proportion Y is 70% or more and less than 90% ×: Proportion Y is less than 70%

(4) Arrangement Accuracy of Solder on Electrodes When the parts were viewed, the ratio Z of the area where the solder part in the connecting part was arranged in 100% of the area of the facing part of the first electrode and the second electrode was evaluated. The placement accuracy of the solder on the electrodes was determined according to the following criteria.

[Criteria for determination of placement accuracy of solder on electrodes]
○○○: Proportion Z is 70% or more ○○: Proportion Z is 60% or more and less than 70% ○: Proportion Z is 50% or more and less than 60% ×: Proportion Z is less than 50%

(5) Bridge between Electrodes In the resulting connected structure, the connection portion was observed with a scanning electron microscope to confirm whether or not a bridge was formed between adjacent electrodes. Bridges between electrodes were judged according to the following criteria.

[Evaluation criteria for bridges between electrodes]
○: Bridge between electrodes is not formed ×: Bridge between electrodes is formed

(6) Solder Side Balls In the obtained connection structure, by observing the connection portion with a scanning electron microscope, solder side balls with a diameter of 100 μm or more or solder side balls with a diameter of less than 100 μm were formed around the connection portion. It was confirmed whether or not Solder side balls were evaluated according to the following criteria.

[Determination Criteria for Solder Side Balls with a Diameter of 100 μm or More]
○○○: Solder side balls with a diameter of 100 µm or more are not formed around the connection part ○○: The number of solder side balls with a diameter of 100 µm or more formed around the connection part is 3 or less ×: Connection part The number of solder side balls with a diameter of 100 μm or more formed around the

[Determination Criteria for Solder Side Balls with a Diameter of Less Than 100 μm]
○○○: The number of solder side balls with a diameter of less than 100 μm formed around the connection is 3 or less ○○: The number of solder side balls with a diameter of less than 100 μm formed around the connection is 4 more than 10 or less ×: More than 11 solder side balls with a diameter of less than 100 μm formed around the connection

(7) Resin Curing Rate Using the obtained conductive material, the resin curing rate was measured by the method described above. The resin curing rate was determined according to the following criteria. As a differential scanning calorimeter (DSC) device, "EXSTAR DSC7020" manufactured by SII was used.

[Criteria for determination of resin curing rate]
○○○: Resin curing rate is 75% or more ○○: Resin curing rate is 70% or more and less than 75% ×: Resin curing rate is less than 70%

The results are shown in Tables 1-3 below.

A similar tendency was observed when using a flexible printed circuit board, a resin film, a flexible flat cable, and a rigid flexible circuit board.

DESCRIPTION OF SYMBOLS 1, 1X... Connection structure 2... 1st connection object member 2a... 1st electrode 3... 2nd connection object member 3a... 2nd electrode 4, 4X... connection part 4A, 4XA... solder part 4B, 4XB ... Cured material part 11 ... Conductive material 11A ... Solder particles 11B ... Binder resin

Claims (7)

A binder resin, a curing agent or curing accelerator, flux, and a plurality of solder particles,
satisfying the following formula (1), where xppm is the oxygen concentration of the solder particles and y parts by weight is the content of the flux with respect to 100 parts by weight of the solder particles ,
A conductive material having a resin cure rate of 70% or more as a reaction product when the conductive material is cured for 25 seconds under the following heating conditions.
0.001x≦y≦0.012x Formula (1)
Heating conditions for measuring resin curing rate:
0 to 5 seconds: Start heating the conductive material at 0° C., and set the temperature of the conductive material after 5 seconds to the melting point of the solder particles.
5 seconds to 15 seconds: The conductive material at the melting point of the solder particles is heated, and after 15 seconds the temperature of the conductive material is brought to the melting point of the solder particles +40°C.
15 seconds to 25 seconds: The conductive material having the melting point of the solder particles +40°C is held at the melting point of the solder particles +40°C. 2. The conductive material according to claim 1, wherein the solder particles have a particle diameter d50 of 50 [mu]m or less. 3. The conductive material according to claim 1, wherein a content of said solder particles is 10% by weight or more and 70% by weight or less in 100% by weight of said conductive material. The conductive material according to any one of claims 1 to 3 , which is a conductive paste. a first connection target member having a first electrode on its surface;
a second connection target member having a second electrode on its surface;
A connecting portion that connects the first connection target member and the second connection target member,
The material of the connection portion is the conductive material according to any one of claims 1 to 4 ,
A connection structure, wherein the first electrode and the second electrode are electrically connected by a solder portion in the connection portion. Using the conductive material according to any one of claims 1 to 4 , disposing the conductive material on the surface of a first connection target member having a first electrode on the surface;
A second member to be connected having a second electrode on the surface of the conductive material opposite to the side of the first member to be connected is provided so that the first electrode and the second electrode face each other. arranging to
By heating the conductive material to a melting point of the solder particles or higher, a connecting portion connecting the first member to be connected and the second member to be connected is formed from the conductive material, and A method of manufacturing a connection structure, comprising the step of electrically connecting the first electrode and the second electrode with a solder portion in the connection portion. In the step of arranging the second member to be connected and the step of forming the connecting portion, pressure is not applied, and the weight of the second member to be connected is applied to the conductive material, or
In at least one of the step of arranging the second member to be connected and the step of forming the connecting portion, pressure is applied, and the step of arranging the second member to be connected and forming the connecting portion 7. The method for manufacturing a connected structure according to claim 6 , wherein the pressure for pressurization is less than 1 MPa in both steps.

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