JP4437827B2 - Method for producing anisotropic conductive adhesive sheet - Google Patents

Description

The present invention relates to a method for producing a conductive adhesive sheet in which conductivity is imparted only in the thickness direction of a sheet by conductive fine particles dispersed and arranged in the sheet surface.

2. Description of the Related Art Conventionally, a conductive adhesive sheet that imparts conductivity only in the thickness direction has been used at the time of connection between a liquid crystal display wiring and a flexible substrate, high density mounting of an integrated circuit component on a substrate, or the like. An example of a conventional conductive adhesive sheet is shown in FIG . In this example, the conductive fine particles 4 are randomly arranged in the sheet 20 made of an adhesive layer. This sheet has the following problems.
In recent years, the dimensions of connected wiring patterns and land patterns have been increasingly miniaturized. When the dimension of the connected pattern is reduced, in the sheet in which the conductive fine particles are randomly dispersed and arranged, as shown in FIG. 9B , the connected pattern is arranged at the position A where the conductive fine particles do not exist. The probability that As a result, the connected patterns may not be electrically connected.

In order to solve this problem, it is effective to disperse smaller conductive fine particles in the sheet at a high density. However, when the size of the conductive fine particles is reduced, as shown in FIG. There is a problem that variations in the protruding height of the connection patterns P1, P2 from the surfaces of the substrates B1, B2 cannot be absorbed. When the density of the conductive particles 4 in the sheet 20 is increased, as shown in FIG. 10B , when the patterns P1 and P2 are arranged at a fine pitch, a short (short circuit) occurs between adjacent patterns. ) Is likely to occur. That is, in these methods, the connection reliability of a conductive adhesive sheet in which conductive fine particles are randomly dispersed and arranged is not improved.

On the other hand, JP-A-5-67480 and JP-A-10-256701 describe that conductive fine particles are dispersed in a predetermined arrangement in a sheet.
In the method described in Japanese Patent Laid-Open No. 5-67480, the conductive fine particles are charged before being dispersed in the sheet (adhesive layer), and the repulsive force between the conductive fine particles is utilized to make the conductive fine particles in the sheet. Are uniformly dispersed. In addition, each position of the conductive fine particles and the support is charged with different charges, and after the conductive fine particles are arranged on the support in a predetermined arrangement, the conductive fine particles are transferred to the adhesive layer in a state in which this arrangement is maintained. It is described to do.
However, in this method, since the arrangement is maintained by the repulsive force between the charged conductive fine particles, it is impossible to bring the distance between the adjacent conductive fine particles within the sheet surface closer to 20 μm or less.

In JP-A-10-256701, a composition comprising a rubber material and conductive particles is formed into a sheet using conductive particles having magnetism, and a magnetic field is applied in the thickness direction of the sheet. It is described that the conductive particles are oriented to cure the rubber in this state.
However, this method has the following problems. Since it is difficult to concentrate the magnetic field in a very narrow region, the distance between adjacent conductive fine particles in the sheet surface cannot be brought close to 20 μm or less. In some cases, the conductive particles are arranged so as to overlap in the thickness direction of the rubber sheet. It is difficult to arrange the conductive particles regularly (while maintaining a predetermined interval between adjacent particles). The conductive particles that can be used are limited to magnetic materials.

The present invention has been made paying attention to such problems of the prior art, and conductive adhesion imparting conductivity only in the thickness direction of the sheet by conductive fine particles dispersed and arranged in the sheet surface. Provided is a method for producing a conductive adhesive sheet in which conductive fine particles are regularly and densely arranged in a sheet surface (so that the distance between adjacent conductive fine particles is 20 μm or less). Is an issue.

This invention is a manufacturing method of the electroconductive adhesive sheet which solved the said subject.
That is,
1. Adhesive layers are disposed on both sides of a core film disposed in the center in the thickness direction in an adhesive sheet that imparts conductivity only in the thickness direction of the sheet by conductive fine particles dispersed in the sheet surface. The core film and the adhesive layer are insulative, and the core film is formed of a resin having a softening temperature higher by 20 ° C. or more than the resin constituting the adhesive layer, and a part of the individual conductive fine particles or In the method of manufacturing an electrically conductive adhesive sheet having anisotropy, all of which are present in the core film and the conductive fine particles are arranged in a predetermined arrangement in the core film surface, the core film having holes that do not penetrate therethrough A first adhesive layer is formed on the surface opposite to the first surface, and then conductive fine particles are placed in the holes, and then a second adhesive layer is formed on the other surface of the core film. A method for producing a conductive adhesive sheet.
2. The method for producing a conductive adhesive sheet according to 1, comprising a step of forming a hole not penetrating the core film by laser irradiation.
3. The conductive fine particles are formed of copper, gold, silver, nickel, palladium, indium, tin, lead, zinc, bismuth, or an alloy of any of these metals, or carbon, or a metal coating on the surface. 3. The method for producing a conductive adhesive sheet according to 1 or 2, wherein the conductive adhesive sheet is a fine particle .

According to the conductive adhesive sheet of the present invention, a plurality of through holes are formed in a predetermined arrangement in the core film surface, and conductive fine particles are arranged in the through holes. It is possible to set in accordance with the arrangement pitch of the pattern to be performed, the wiring width, and the like. In use, the arrangement of the conductive fine particles in the sheet surface is fixed by the core film.
Therefore, by setting the pitch and size of the through holes corresponding to the arrangement pitch and wiring width of the pattern to be connected, even when connecting patterns arranged at a fine pitch, short-circuits between adjacent patterns. Can be prevented from occurring. Further, it is possible to eliminate the fear that the pattern to be connected is disposed at a position where no conductive fine particles are present.
As a result, according to the conductive adhesive sheet of the present invention, a highly reliable connection can be performed even when the dimension of the pattern to be connected is small or when a pattern arranged at a fine pitch is connected.
Further, according to the method for producing a conductive adhesive sheet of the present invention, the conductive fine particles are regularly and densely arranged in the sheet surface (so that the distance between adjacent conductive fine particles is 20 μm or less). The manufactured conductive adhesive sheet can be easily manufactured.

The core film used in the present invention needs to be formed from a resin having a softening temperature higher by 20 ° C. or more than the resin constituting the adhesive layer formed on both sides thereof. This is because the flow of resin occurs when the conductive adhesive sheet of the present invention is placed in the center and the components or substrates to be connected from above and below are heat-pressed, but the conductive fine particles arranged in advance are difficult to move. It is a device.
That is, the adhesive layer needs to be fluidized before the core film is fluidized so that the adhesive layer moves following the unevenness of the connection bumps on the component or the substrate and no gap is generated. When the resin composing the core film is fluidized at the same time or before the adhesive layer is fluidized, it is difficult to connect the fine pitch because the conductive particles placed in a predetermined position move with the flow of the resin. It becomes.

Therefore, the softening temperature of the core film is 20 ° C. or more, preferably 50 ° C. or more, more preferably 80 ° C. or more higher than the softening temperature of the adhesive resin forming the adhesive layer.
Here, the softening temperature of the core film and the adhesive layer means that the viscosity decreases greatly when the temperature of the resin forming the core film and the adhesive forming the adhesive layer is increased from room temperature (the slope of the viscosity curve). Means the first temperature that changes. This softening temperature can be examined by measuring the viscosity using a viscoelasticity measuring device such as a rheometer while increasing the temperature of the resin and the adhesive from room temperature at a constant rate.
As the resin forming the core film used in the present invention, polyimide resin, polyamide resin, polyamideimide resin, polysulfone resin, polyethersulfone resin, polyester resin, unsaturated polyester resin, polyallyl resin, polyolefin resin, polycarbonate resin, polystyrene A resin such as a resin, a polyphenylene ether resin, a thermoplastic resin containing these resins as a main component, or a thermosetting resin containing a thermosetting component of a type that is cured after being plasticized with heat is preferable.

The thickness of the core film greatly depends on the size of the conductive fine particles used. That is, in the conductive adhesive sheet of the present invention, it is necessary to bring conductive fine particles into contact with both patterns to be connected during use. There are no through-holes in the core film used in the present invention.
That is, the conductive particles arranged in a predetermined manner are in the holes not penetrating formed in the core film, or some or all of the individual conductive particles are taken into the core film. After only the layer is fluidized in accordance with the shape of the connection pattern and then curing is started by heat, the core film is softened by heat, and the portion of the thin core film around the conductive fine particles is fluidized. Therefore, it is necessary to set the thickness so that the core film, which is an insulator around the conductive fine particles, does not hinder connection.

The thickness of the core film is preferably not more than 3 times, more preferably not more than 2 times the average particle diameter of the conductive fine particles used in the conductive adhesive sheet. Further, the lower limit of the thickness is preferably 0.5 times or more, more preferably 0.75 times or more the average particle diameter of the conductive fine particles used in the conductive adhesive sheet. If the core film is thinner than this, the conductive fine particles contained in the holes or recesses will be removed together with the removal of the conductive fine particles adhering to places other than the holes or recesses formed in the core film.
Further, with reference to FIG. 1 (a-1), the thickness of the core film present at the bottom of the hole not penetrating is preferably 0. The thickness of the core film in the portion where no conductive fine particles are present. 5 times or less, more preferably 0.25 times or less. Further, the lower limit of the thickness of the core film present at the bottom of the non-penetrating hole is preferably 0.05 times or more, more preferably 0.1 times the thickness of the core film in the portion where no conductive fine particles are present. That's it. If it is thinner than this, when forming a recess not penetrating into the core film, when the core film is peeled from a mold having a protrusion corresponding to the recess, a location where physical strength cannot be maintained and the portion is broken. Or a portion that becomes a hole through which the concave portion passes is not preferable.

Moreover, in the reference example in this application, the hole which is not penetrated is formed in a core film, and electroconductive fine particles are put only into this hole. Therefore, it is necessary to blow away the conductive fine particles adsorbed at a place other than the holes using compressed air or the like, or to remove them using an adhesive sheet or the like. In this step, when the hole depth is shallower than the particle diameter of the conductive fine particles used, the conductive fine particles that have entered the hole are removed together with unnecessary conductive fine particles. Therefore, the preferable depth of the hole is 0.5 times or more, more preferably 1 time or more of the average particle diameter of the conductive fine particles.
Therefore, the preferable thickness of the core film in the part where the holes are not opened is 0.7 times or more, more preferably 1.2 times or more the average particle diameter of the conductive fine particles used.

In the reference example in the present application, the size of the non-penetrating holes formed in the core film depends on the size of the conductive fine particles used, but is preferably 1 to 1.5 times the average particle diameter of the conductive particles. To do. The arrangement of the holes depends on the arrangement pitch of the connection pattern and the wiring width, but it is preferable to arrange the holes at intervals of 0.3 to 1 times the arrangement pitch. Moreover, it is also possible to form a hole only in the pattern of the part to connect. However, in this case, it is necessary to align the connection pattern and the connection component.
The conductive fine particles used in the present invention preferably have an average particle size of 0.5 to 50 μm, more preferably 1 to 20 μm, and most preferably 2 to 10 μm. If the average particle size of the conductive fine particles is less than 0.5 μm, the variation in the height of the connection pattern may not be absorbed. On the other hand, when the size exceeds 50 μm, it is not suitable for connecting a fine pattern.

The shape of the conductive fine particles used in the present invention is not particularly required to be spherical, and polyhedral and spherical particles may have a large number of protrusions. However, a flat shape is not preferable because it is difficult to put into a hole or to be adsorbed by an adsorption device. Conductive fine particles that are easily crushed during compression and that are easy to deform are preferable because they can increase the contact area with the connection pattern and absorb variations in the height of the connection pattern.
The particle size distribution of the conductive fine particles used in the present invention is preferably such that the standard deviation is 50% or less of the average particle size. More preferably, the standard deviation is 20% or less of the average particle diameter, and most preferably 10% or less. When the particle size distribution of the conductive fine particles is widely distributed with a standard deviation exceeding 50% of the average particle size, the conductive fine particles having a small particle size may cause clogging of the through-holes, or may be present in places other than the holes. It becomes difficult to remove small conductive fine particles. Moreover, it becomes difficult to absorb the height variation of the connection pattern. This leads to a decrease in electrical connection reliability between connection patterns. Moreover, it is preferable that one conductive fine particle is contained in one hole, that is, one conductive fine particle exists in the thickness direction of the core film.

As a method for classifying the conductive fine particles, a conventional method, for example, a centrifugal classifier such as cyclone or clacyclon, a gravity classifier, an inertia classifier, an air classifier, or a classifier by sieving can be used. In order to classify fine conductive fine particles having a particle size of 10 μm or less, first, a coarse classification is performed using an airflow classifier or the like, and then a classification method is performed by sieving using a sieve in which through holes are precisely formed. Is preferred. When fine conductive fine particles having a particle diameter of 10 μm or less are classified by precision sieving, it is effective to use ultrasonic waves in a solvent such as alcohol that does not change the conductive fine particles.
For example, a thermosetting adhesive, a thermoplastic adhesive, or a pressure sensitive adhesive can be suitably used as the adhesive forming the adhesive layer constituting the conductive adhesive sheet produced in the present invention . In particular, it is preferable to use a type of adhesive containing a so-called latent curing agent in which a compound containing a curing agent is confined in a microcapsule and curing starts when the microcapsule is crushed by pressure or heat.

  Examples of the material of the adhesive layer include epoxy resins, polyimide resins, urea resins, amino resins, melamine resins, phenol resins, xylene resins, furan resins, isocyanate resins, benzocyclobutene resins, polyphenylene ethers. Examples thereof include a resin, a polysulfone resin, and a polyethersulfone resin. In particular, from the viewpoint of dimensional stability, heat resistance, etc., the resin constituting the adhesive used is an aromatic compound such as benzene, naphthalene, anthracene, pyrene, biphenyl, phenylene ether, cyclohexane, cyclohexene, bicyclooctane, bicyclo It preferably comprises a compound having a skeleton of an aliphatic cyclic compound such as octene or adamantane in the molecular chain.

In addition, if an adhesive made of a resin soluble in a solvent is used, an adhesive layer can be obtained by applying the adhesive on a support in a state dissolved in a solvent and then drying. Preferably, the thickness of the adhesive layer after drying (solvent removal) is 1 μm to 50 μm, more preferably 5 μm to 20 μm. When the thickness is less than 1 μm, it is difficult to obtain adhesion strength after bonding. When the thickness of the adhesive layer exceeds 50 μm, the amount of the adhesive is too large and the electrical connection between the conductive fine particles and the connection pattern is hindered.
In the conductive adhesive sheet produced in the present invention, the first and second adhesive layers are formed on both sides of the core film, but these adhesive layers are different even if they have the same composition. It does not matter. In addition, the first and second adhesive layers may be formed by laminating a plurality of adhesive layers having different functions.

When the electroconductive adhesive sheet manufactured by this invention is exposed to acidic aqueous solution, water, etc. in a manufacturing process, it is preferable to use the adhesive bond layer which neither a quality change nor reaction arises with an aqueous processing liquid. Further, by using an adhesive layer having tackiness or tackiness, the conductive adhesive sheet of the present invention can be temporarily fixed to an object to be connected.
Hereinafter, an embodiment of a conductive adhesive sheet manufactured by the manufacturing method of the present invention will be described.
One embodiment of the conductive adhesive sheet manufactured by the manufacturing method of the present invention will be described with reference to FIG.
The conductive adhesive sheet shown in FIG. 1 (a-1) includes a core film 1 disposed in the center in the thickness direction, adhesive layers 2 and 3 disposed on both surfaces of the core film 1, and a spherical conductive property. It consists of fine particles 4. The core film 1 is made of a polysulfone thermosetting resin and has a thickness of 10 μm. The adhesive layers 2 and 3 are made of an epoxy thermosetting adhesive containing a latent curing agent and have a thickness of 12 μm.

The conductive fine particles 4 are powders made of an alloy of copper and silver, and have an average particle size of 6 μm and a standard deviation of particle size distribution of 0.5 μm. The softening temperature of the polysulfone-based thermosetting resin used as the core film is 160 ° C., and the softening temperature of the epoxy-based thermosetting adhesive used as the adhesive layer is 60 ° C. A large number of holes 10 not penetrating in the thickness direction are regularly arranged in the film surface in the core film 1.
In this embodiment, as shown in FIG. 1 (b), holes 10 that do not pass through are located at the positions of lattice points (intersections of vertical lines and horizontal lines of the lattice) and the center positions of the unit lattices in the film plane. Has been placed. The interval between adjacent lattice points along the vertical line is 15 μm, and the interval between adjacent lattice points along the horizontal line is 15 μm. The planar shape (cross-sectional shape along the film surface) of the hole 10 not penetrating is a circle, and the diameter of this circle is 7.5 μm (1.25 times the average particle diameter of the conductive fine particles 4). In addition, one conductive fine particle 4 is disposed in every hole 10 of the core film 1.

The conductive adhesive sheet of FIG. 1A-2 is an example in which conductive fine particles arranged in a predetermined arrangement are embedded in the core film 1 in an embedded state. The thickness of the core film 1 is 4 μm, the thickness of the adhesive layers 2 and 3 is 10 μm, and the average particle size of the conductive fine particles is 6 μm.
These conductive adhesive sheets are pressed while being sandwiched between substrates to be connected during use. As a result, the adhesive layers 2 and 3 are deformed to start curing. Subsequently, the core film 1 is deformed with a time delay, and the conductive fine particles 4 are brought into contact with both patterns to be connected. At this time, the arrangement of the conductive fine particles 4 in the sheet surface is fixed by the core film 1. In this conductive adhesive sheet, as described above, the conductive fine particles 4 are regularly and densely arranged in the sheet surface (so that the distance between adjacent conductive fine particles is 20 μm or less). ing.

Therefore, according to the conductive adhesive sheet of this embodiment, even when the dimension of the pattern to be connected is small or when patterns arranged at a fine pitch are connected, highly reliable connection can be performed. In particular, by setting the pitch and size of the holes 10 in accordance with the arrangement pitch and the wiring width of the pattern to be connected, the position where the conductive fine particles 4 do not exist (indicated by symbol A in FIG. 9 ). The fear of being placed in is eliminated.
According to the conductive adhesive sheet of this embodiment, since the conductive fine particles are regularly arranged, the conductive fine particles are extremely small (for example, a diameter of 2 μm or less, as in the case of being randomly arranged). Even if it is not, the probability that the pattern to be connected is arranged at a position where the conductive fine particles do not exist (indicated by symbol A in FIG. 9 ) becomes zero in principle. Therefore, in the conductive adhesive sheet of this embodiment, the conductive fine particles are made to have a certain size, so that the connection pattern protrudes from the substrate surface more than the conductive adhesive sheet in which the conductive fine particles are randomly arranged. It becomes easy to absorb the variation in height.

FIG. 1C shows a conductive adhesive sheet in which the arrangement of the holes 10 in the plane of the core film 1 is different from the above. In this example, the holes 10 are arranged at the positions of lattice points in the film plane. In each of these holes 10, one conductive fine particle 4 is disposed.
An embodiment of a method for producing a conductive adhesive sheet of the present invention will be described with reference to FIGS.
First, the first adhesive layer 2 is formed on the support 5 by applying an adhesive solution with a predetermined thickness on the support 5 and then drying. FIG. 4A shows this state. A core film 1 having holes 10 as shown in FIG. 4B is bonded onto the first adhesive layer 2. FIG. 4C shows this state. This joining is performed by placing the core film 1 on the first adhesive layer 2 and heating. This heating temperature is set to a temperature at which the adhesive forming the adhesive layer 2 is not cured.

Next, the conductive fine particles 4 are filled in the holes 10 of the core film 1.
As shown in FIG. 3C, a sheet made of a support 5, a first adhesive layer 2, and a core film 1 is obtained after a powder made of a large number of conductive fine particles 4 is dispersed from above the core film 1. The conductive fine particles 4 are put into the holes 10 of the core film 1 by vibrating the whole. The conductive fine particles 4a that do not enter the hole 10 and exist on the upper surface of the core film 1 are removed by pressing with a film with an adhesive or the like. By vibrating the entire sheet, the conductive fine particles 4 easily enter all the holes 10. Alternatively, the conductive fine particles 4 may be put into the holes 10 of the core film 1 by passing the entire sheet through the container a plurality of times in the conductive fine particles. In this way, as shown in FIG. 3D, the conductive particles 4 are put in each of the holes 10 one by one.

Next, the second adhesive layer 3 is formed on the core film 1 and the cover film 6 is coated. Thereby, as shown in FIG.4 (e), a conductive adhesive sheet is obtained in the state by which the support body 5 was joined to one surface, and the cover film 6 was joined to the other surface, respectively.
In this method , as shown in FIG. 4B, as a method of forming the core film 1 having the holes 10 not penetrating, a method of irradiating the core film 1 with laser light as shown in FIG. It is preferable to adopt.
As an embodiment of the laser beam irradiation method, first, as shown in FIG. 5A, a metal mask K having an opening K1 corresponding to the hole 10 formed in the core film 1 is formed on the support 5. An adhesive layer is formed on the core film 1 made of a thermoplastic polyimide resin fixed on the adhesive layer, and an excimer laser is irradiated from above the mask K. Thereby, the part irradiated with the excimer laser of the core film 1 is removed, and the hole 10 is formed. FIG. 5B shows this state.

As the laser light used here, such as a carbon dioxide laser, a fundamental wave of a YAG laser, etc. having an oscillation wavelength in the infrared region, the third and fourth harmonics of a YAG laser, an excimer laser, a copper vapor laser, etc. Thus, the thing which can irradiate the light of an ultraviolet-ray or a vacuum ultraviolet-ray area | region is mentioned.
For example, by using the third and fourth harmonics of a YAG laser, a copper vapor laser, or an excimer laser, the minute hole 10 having a diameter of 20 μm or less can be easily formed. The cross-sectional shape of the hole may be tapered.
As described above, according to this method , the fine hole 10 having a diameter of 20 μm or less can be easily formed in the core film 1 by adopting the laser irradiation method.

In this embodiment, the method of the present invention was formed on the support 5 as a method of forming the first adhesive layer 2 on one surface of the core film 1 having the holes 10 not penetrating. Although the method of joining the core film 1 having the non-through holes 10 on the first adhesive layer 2 is adopted, instead of this, for example, the core film 1 having the non-through holes 10 is bonded onto the core film 1. You may employ | adopt the method of apply | coating and drying an agent solution.
In this case, after forming the first adhesive layer on the core film, the core film side is turned up, and conductive fine particles are put in the holes, and then the second adhesive layer is formed on the core film. To do.

[ Reference Example 1 ]
(Preparation of conductive adhesive sheet)
This reference example will be described with reference to FIG.
First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. A thermoplastic polyimide solution was applied to the surface of the PET film (support) 5 coated with a release agent using a blade coater. Next, by removing the solvent from the coating film by drying, a film made of thermoplastic polyimide having a thickness of 10 μm was formed on the PET film 5.

As the thermoplastic polyimide solution, a thermoplastic polyimide solution “UPA-N-221” manufactured by Ube Industries, Ltd. was used.
Next, cylindrical convex patterns having a diameter of 7.5 μm and a height of 8 μm are arranged on the surface in the same arrangement as the arrangement of the non-through holes 10 shown in FIG. Furthermore, a nickel plate-shaped mold 13 in which the same cylindrical convex pattern was regularly arranged at the center of the lattice was also produced.
A core film made of thermoplastic polyimide and having a thickness of 10 μm was placed on this mold, and a thermocompression treatment was performed at 180 ° C. and 1 MPa for 10 minutes using a hot press machine (FIG. 3A). After cooling, the core film was peeled from the mold to form a non-penetrating recess corresponding to the mold protrusion on one side of the core film.

Next, as shown in FIG. 3 (b), a PET film 5 having an adhesive layer (first adhesive layer) 2 made of an epoxy adhesive on one surface is used, and the adhesive layer 2 is used as a core. The film 1 was placed on the core film 1 and heated toward the surface without a concave portion, and joined by heating.
The PET film 6 in which the adhesive layer 3 made of an epoxy adhesive is formed on one surface was produced as follows. First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. An epoxy adhesive solution was applied to the surface of the PET film (cover film) 6 coated with a release agent using a blade coater. Next, a layer 3 made of an epoxy adhesive having a thickness of 10 μm was formed on the PET film 6 by drying and removing the solvent from the coating film.

The composition of the epoxy adhesive solution used is as follows: bisphenol A type liquid epoxy resin: 10 parts by weight, phenoxy resin: 10 parts by weight, latent hardener comprising imidazole derivative epoxy compound of microcapsule type: 4.5 parts by weight Toluene / ethyl acetate mixture: 5 parts by weight.
Next, after spraying a powder made of a large number of conductive fine particles 4 on the core film 1, the conductive fine particles 4 are formed in all the holes 10 by applying vibration to the entire sheet using an ultrasonic vibration device. I put it in. Next, the adhesive film “SPV-363” manufactured by Nitto Denko Co., Ltd. is attached to the surface of the core film 1 using a roller and then peeled off, so that it does not enter the hole 10 and exists on the upper surface of the core film 1. The conductive fine particles 4a to be removed were removed.

Examples of the powder composed of the conductive fine particles 4 include Ag _x Cu _(1-x) (0.008 ≦ x ≦ 0.4) described in JP-A-6-223633, and silver on the particle surface. Concentration is higher than 2.2 times the average silver concentration, and is composed of spherical conductive particles having a region where the silver concentration increases toward the particle surface near the surface, the average particle size is 6 μm, and the standard deviation of the particle size distribution A powder having a thickness of 0.5 μm was used.
Next, as shown in FIG. 3 (d), a PET film 6 having an adhesive layer (second adhesive layer) 3 made of an epoxy adhesive on one surface is used, and the adhesive layer 3 is used as a core. The film 1 was placed on the core film 1 and heated by heating toward the film 1 side.

As described above, the adhesive layers 2 and 3 made of epoxy adhesive are arranged on both surfaces of the core film 1 made of thermoplastic polyimide resin, and the core film 1 has circular holes 10 having a diameter of 7.5 μm, A conductive adhesive sheet which is regularly formed at a pitch of 15 μm (lattice spacing) in the arrangement shown in FIG. 1B, and each conductive fine particle 4 made of copper-silver alloy is arranged in each hole 10. was gotten. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
The softening temperature of the thermoplastic polyimide and epoxy adhesive forming the core film was measured using a rotary “rheometer” which is a viscoelasticity measuring device manufactured by Rheometrics Scientific F.E. The measurement conditions were a rotation speed: 10 rad / sec, a temperature rise start temperature: room temperature, a temperature rise speed: 10 ° C./min, and the first temperature at which the slope of the viscosity curve changed was determined as the softening temperature. As a result, the softening temperature of the epoxy adhesive was about 60 ° C., and the softening temperature of the thermoplastic polyimide was 170 ° C.

(Production of mold)
Zinc displacement plating was performed on the surface of aluminum, and a copper layer having a thickness of 3 μm was formed thereon using a copper pyrophosphate plating bath. Further, the copper surface was blackened to produce a conductive substrate having a low reflectance. A photosensitive resin layer having a thickness of 10 μm was formed on the conductive substrate, and a resin pattern was obtained using photolithography through a glass chromium mask corresponding to the hole arrangement pattern shown in FIG.
The photosensitive resin used was an unsaturated polyester prepolymer having a number average molecular weight of 2000: 100 parts by weight, tetraethylene glycol dimethacrylate: 10.7 parts by weight, diethylene glycol dimethacrylate: 4.3 parts by weight, pentaerythritol tris Methacrylate: 15 parts by weight, phosphoric acid (monomethacryloyloxyethyl): 3.6 parts by weight, 2,2-dimethoxy-2-phenylacetophenone: 2 parts by weight, 2,6-di-tert-butyl-4-methylphenol : 0.04 parts by weight, and “OPLAS Yellow 140” manufactured by Orient Chemical Co., Ltd .: 0.11 parts by weight were added and mixed by stirring.

The unsaturated polyester prepolymer having a number average molecular weight of 2,000 was obtained by dehydration polycondensation reaction by adjusting the charging ratio of adipic acid, isophthalic acid, itaconic acid, fumaric acid and diethylene glycol. The number average molecular weight was measured using a gel permeation chromatography apparatus manufactured by Shimadzu Corporation and calibrated with a polystyrene standard product.
Next, as an exposure mask M, a circular chrome pattern having a diameter of 7.5 μm has the same arrangement as the arrangement of the through holes 10 shown in FIG. A glass photomask regularly arranged in the center was prepared. This exposure mask M was placed on the photosensitive resin layer 11, and the light from the ultrahigh pressure mercury lamp was irradiated on the exposure mask M. This irradiation light is a parallel light beam obtained by collimating the light from the light source by the optical system. FIG. 2A shows this state. However, in this figure, a PET cover film having a thickness of 10 μm is omitted.

Next, the PET cover film was peeled off and developed. As a result, the portion of the photosensitive resin layer 11 that was not exposed to light was removed, and the core film 1 having a large number of holes 10 was formed on the conductive substrate as shown in FIG.
Next, the substrate surface on which the resin pattern was formed was subjected to a palladium catalyst application treatment, followed by electroless nickel plating to form a nickel layer having a thickness of several μm. Furthermore, electrolytic nickel plating was performed in a nickel sulfamate plating bath to form a nickel layer having a thickness of 70 μm. FIG. 2 (d) shows this state.
Thereafter, the formed nickel layer was peeled from the substrate to obtain a nickel mold in which cylindrical convex portions having a diameter of 7.5 μm and a height of 10 μm were regularly arranged on the surface. The surface of the obtained mold was treated with a silicone release agent (manufactured by Shin-Etsu Chemical Co., Ltd., SEPA-COAT SP).

(Performance evaluation)
6 (a) is a plan view showing a part of a test substrate, FIG. 6 (b) is a line a-a sectional view of FIGS. 6 (a). The test substrate 30 has 200 wirings 32 on an insulating substrate 31, and the wirings 32 have a thickness of 15 μm and are exposed on the insulating substrate 31 in a convex shape. The width of the wiring 32 is 15 μm, and the arrangement pitch p is 30 μm.
First, peel off the PET film 5, 6 from both sides of the conductive adhesive sheets obtained in the above manner, and all the wiring 32 portion of the test substrate 30, shows a plan view of the pattern in FIG. 8 (a) A glass substrate is sandwiched between one convex linear pattern 22 and a substrate D having a convex circular pattern 21 and an inspection terminal 26, and heated to 230 ° C. under a pressure of 50 MPa for 5 minutes. Retained.

All the patterns of the substrate D are made using copper plating, the width of the linear pattern 22 is 15 μm, and the thickness is 15 μm. The diameter of the circular pattern arranged on both sides of the linear pattern 22 is 15 μm, and the height is 15 μm. They are arranged with a pitch of 30 μm. A thin chromium layer is formed between the glass substrate and the copper plating film for the purpose of improving adhesion. The circular pattern 21 is a dummy pattern for ensuring stability during connection evaluation. At this time, the wiring 32 of the test substrate 30 and the linear pattern of the substrate D were arranged so as to be orthogonal to each other. As a result, the wiring 32 portion of the test substrate 30 and the substrate D were bonded by the conductive adhesive sheet.
Figure 7 includes a substrate D which was formed a convex-shaped conductor pattern on the glass substrate shown a plan view of the pattern wiring 32 parts in FIG. 8 of the test substrate 30 (a) is bonded by a conductive adhesive sheet It is sectional drawing which shows the state. The sectional view corresponds to a line b-b sectional view of FIG. 6 (a). During this bonding, the core film 1 and the adhesive layer 2,3 of both sides of the conductive adhesive sheet to deform, are shown collectively the in Figure 7, reference numeral 23.

A connection confirmation test using the conductive adhesive sheet of Reference Example 1 was performed using the two test pieces thus obtained. That is, for each test piece, the resistance between the 200 test pads 35 and the test pads on the substrate D was measured. As a result, it was found that none of the total 400 connection points of the two test pieces is not electrically connected to the copper substrate D.
Next, the PET films 5 and 6 are peeled off from both surfaces of the conductive adhesive sheet obtained by the above method, and all the wiring 32 portions of the test substrate 30 and the glass whose cross-sectional structure is shown in FIG. The plate was sandwiched between the plates E, heated to 230 ° C. under a pressure of 50 MPa, and held for 5 minutes. This on the glass substrate E are given the irregularities on the surface in the same pattern as the pattern shown FIG. 8 (a). That is, the hatched portion in FIG. 8 (a) so as to project, and ablation processing using an excimer laser. The height of the convex portion was 15 μm. As a result, the wiring 32 portion of the test substrate 30 and the glass substrate were bonded by the conductive adhesive sheet. Similar to the connection confirmation test, both substrates were arranged so that the wiring 32 of the inspection substrate and the linear pattern on the glass substrate E were orthogonal to each other.

Using the two test pieces thus obtained, the insulation resistance between the adjacent test pads 35 was measured. As a result, regarding the total of 398 test pads 35 of the two test pieces, all the insulation resistances were 10 ¹² Ω or more. As a result, it was found that no short circuit occurred at all the adjacent connection points in all the connection points of the total 398 sets of the two test pieces.
From these test results, with the conductive adhesive sheet of this example, as shown in FIG. 6 , the wiring 32 and the substrate D of the test substrate 30 are connected by the conductive fine particles 4 of the conductive adhesive sheet and are adjacent to each other. It can be seen that the wirings 32 are not connected by the conductive fine particles 4.

[ Example 1 ]
(Preparation of conductive adhesive sheet)
In this embodiment, a conductive adhesive sheet is produced by a method corresponding to the embodiment of the method of the present invention . This embodiment will be described with reference to FIG. First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. An epoxy adhesive solution was applied to the surface of the PET film coated with the release agent using a blade coater. Next, the solvent was dried and removed from the coating film to form an adhesive layer made of an epoxy adhesive having a thickness of 12 μm on the PET film. Two sheets comprising this PET film and an adhesive layer were prepared.
The composition of the epoxy adhesive solution used is as follows: bisphenol A type liquid epoxy resin: 10 parts by weight, phenoxy resin: 10 parts by weight, latent hardener comprising imidazole derivative epoxy compound of microcapsule type: 4.5 parts by weight Toluene / ethyl acetate mixture: 5 parts by weight.

On the other hand, the surface of the same PET film as described above was coated with polydimethylsiloxane as a release agent in a film thickness of about 50 nm. A thermoplastic polyimide resin solution (“UPA-N-111C” manufactured by Ube Industries, Ltd.) was applied to the surface of the PET film coated with the release agent using a blade coater. Next, by removing the solvent from the coating film by drying, a core film 1 made of a thermoplastic polyimide resin is formed on the PET film (support) with a thickness of 10 μm. Was adhered from the core film side, and then the PET film was peeled off.
Next, a nickel metal mask K having an opening K1 designed so as to form a non-through hole 10 formed in the core film 1 is prepared, and the metal mask K is disposed above the core film 1, Excimer laser was irradiated from above the metal mask K. FIG. 5A shows this state. In the metal mask K, circular holes having a diameter of 7.5 μm are regularly formed at a pitch of 15 μm (lattice interval) with the same arrangement as the arrangement of the through holes shown in FIG.

Excimer laser irradiation was performed using an excimer laser processing apparatus including an excimer laser “INDEX800” manufactured by LUMONICS and a transport system “SIL300H” manufactured by Sumitomo Heavy Industries, Ltd. The laser wavelength was 248 nm (krypton fluoride gas), the laser beam dimensions were 8 mm × 25 mm, and the oscillation frequency was 200 Hz.
As a result, the portion of the core film 1 irradiated with the excimer laser (the lower portion of the opening K1) was removed, and the non-through hole 10 was formed at a predetermined position of the core film 1. In the core film 1, circular non-through holes 10 having a diameter of 7.5 μm and a depth of 8 μm are regularly arranged at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG. . FIG. 5B (same as FIG. 4C) shows this state.

After the powder composed of a large number of conductive fine particles 4 is dispersed on the core film 1, the conductive fine particles 4 are put in all the through holes 10 by applying vibration to the entire sheet using an ultrasonic vibration device. It was. This state is shown in FIG. Next, the adhesive film “SPV-363” manufactured by Nitto Denko Corporation is attached to the surface of the core film 1 using a roller, and then peeled off, so that it does not enter the through-hole 10 and the upper surface of the core film 1. The existing conductive fine particles were removed.
Examples of the powder composed of the conductive fine particles 4 include Ag _x Cu _(1-x) (0.008 ≦ x ≦ 0.4) described in JP-A-6-223633, and silver on the particle surface. Concentration is higher than 2.2 times the average silver concentration, and is composed of spherical conductive particles having a region where the silver concentration increases toward the particle surface near the surface, the average particle size is 6 μm, and the standard deviation of the particle size distribution A powder having a diameter of 0.6 μm was used.

Next, as shown in FIG. 4 (e), an adhesive layer (second adhesive layer) prepared in advance by the above-mentioned method and having an adhesive layer made of an epoxy adhesive formed on a PET film is formed. ) It was placed on the core film 1 with the 3 side facing down and joined by heating.
Thereby, the adhesive layers 2 and 3 made of 12 μm thick epoxy adhesive are arranged on both surfaces of the core film 1 made of polyimide resin and having a thickness of 7.5 μm. The through-holes 10 are regularly formed at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG. 1B, and one conductive fine particle 4 made of copper-silver alloy is arranged in each hole 10. A conductive adhesive sheet was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.

(Performance evaluation)
A conductive adhesive sheet produced in this example, Reference Example 1 and the same test substrate 30 using the substrate D, and a glass substrate, to produce a respective two test pieces in the same manner as in Reference Example 1 A connection confirmation test and a short confirmation test were performed in the same manner as in Reference Example 1 .
As a result, in the connection confirmation test, it was confirmed that none of the total 400 connection locations of the two test pieces was not electrically connected to the substrate D.
In the short check test, all the insulation resistances were 10 ¹² Ω or more for a total of 398 sets of wirings 32 of two test pieces. As a result, it was confirmed that no short circuit occurred between all the adjacent wirings 32 at all the connection points of the total 398 sets of the two test pieces .

[Comparative Example 1]
(Preparation of conductive adhesive sheet)
To the epoxy adhesive solution used in Reference Example 1 , the conductive fine particles 4 used in Reference Example 1 were added and mixed at a ratio of 1.2% by volume. This liquid was applied to the surface of a PET film coated with polydimethylsiloxane as a release agent using a blade coater. Next, by removing the solvent from the coating film by drying, a conductive adhesive sheet having a thickness of 28 μm was formed on the PET film. This conductive adhesive sheet is used after peeling off the PET film.
The addition rate of the conductive fine particles 4 to the epoxy adhesive solution was set so that the content of the conductive fine particles 4 in the conductive adhesive sheet was approximately the same as that in Example 2.

(Performance evaluation)
Preparation and conductive adhesive sheet produced in Comparative Example 1, Reference Example 1 and the same test substrate 30, the copper plate D, and by using the glass substrate, each of two test pieces in the same manner as in Reference Example 1 Then, a connection confirmation test and a short confirmation test were performed in the same manner as in Reference Example 1 .
As a result, in the connection confirmation test, it was confirmed that four of the 400 connection pads 34 of the two test pieces were not electrically connected to the copper plate D.
Further, in the short check test, all the insulation resistances were 10 ¹² Ω or more for a total of 400 test pads 35 of two test pieces. As a result, it was confirmed that no short circuit occurred between all adjacent connection pads 34 for all 400 connection pads 34 of the two test pieces.

[Comparative Example 2]
A conductive adhesive sheet having the same configuration was produced in the same manner as in Comparative Example 1 except that the addition ratio of the conductive fine particles 4 to the epoxy adhesive solution was 20% by volume.
Preparation and conductive adhesive sheet produced in Comparative Example 2, Reference Example 1 and the same test substrate 30, the copper plate D, and by using the glass substrate, each of two test pieces in the same manner as in Reference Example 1 Then, a connection confirmation test and a short confirmation test were performed in the same manner as in Reference Example 1.
As a result, in the connection confirmation test, it was confirmed that all the 400 connection pads 34 of the two test pieces were electrically connected to the copper plate D.
In the short check test, the insulation resistance was 10 ⁸ Ω or less at 10 points out of a total of 400 test pads 35 of 2 test pieces. Thereby, it turned out that the short circuit has generate | occur | produced between the connection pads 34 adjacent in these 10 places.

It is sectional drawing (a-1, a-2) and top view (b, c) which show one Embodiment of the electroconductive adhesive sheet of this invention. It is a figure explaining the manufacturing method of the type | mold used in the method of manufacturing the electroconductive adhesive sheet of the reference example 1. FIG. It is a figure explaining embodiment of the method to manufacture an electroconductive adhesive sheet , and the reference example 1. FIG. Embodiment of a method of manufacturing a conductive adhesive sheet of the present invention, and is a diagram for explaining a first embodiment. It is a figure explaining embodiment of the method of manufacturing an electroconductive adhesive sheet . They are the top view (a) and sectional drawing (b) which show the board | substrate for a test used for performance evaluation in Example 1, Reference example 1, and Comparative Examples 1 and 2. FIG. Wiring portion of the test substrate and the substrate D is, Example 1, a diagram showing a state of being adhered by a conductive adhesive sheet of Reference Example 1, corresponding to line b-b cross section of FIG. 6 (a) To do. It is a top view (a) which shows the pattern of the board | substrate D used for performance evaluation, and the board | substrate E, (b) is equivalent to the cc sectional view taken on the line of the board | substrate E. It is sectional drawing (a) and a top view (b) which show an example of the conventional conductive adhesive sheet. It is sectional drawing for demonstrating the problem of the conventional electroconductive adhesive sheet.

Explanation of symbols

1 Core film 2 Adhesive layer (first adhesive layer)
3 Adhesive layer (second adhesive layer)
4 conductive fine particles 5 support 6 cover film 7 conductive substrate 8 photosensitive resin layer 10 through hole 11 photosensitive resin layer 12 electroless plating layer 13 metal layer 20 sheet made of adhesive layer 21 copper cylindrical convex portion 22 made of copper Linear convex portion 23 Core film and adhesive layer 24 Cylindrical convex portion made of glass 25 Glass plate 26 Electrical inspection pad 30 Test substrate 31 Insulating substrate 32 Wiring 35 Inspection pad 170 Conductive particle array jig 171 Concave portion 100 Porous component 300 Particle adsorption device A Position where conductive fine particles do not exist B1 Substrate B2 Substrate C Sectional line of FIG . 8 (b) sectional view D Substrate h Height of wiring K1 Opening K Metal mask M Exposure mask M1 Photo Mask P1 Connection pattern P2 Connection pattern p Wiring arrangement pitch p10 Cylindrical convex arrangement pitch W Wiring Width W1 Width of copper straight convex part W2 Diameter of copper cylindrical convex part

Claims (3)

  In the adhesive sheet that imparts conductivity only in the thickness direction of the sheet by the conductive fine particles dispersed and arranged in the sheet surface, an adhesive layer is disposed on both surfaces of the core film disposed in the center in the thickness direction, The core film and the adhesive layer are insulative, and the core film is formed of a resin having a softening temperature that is 20 ° C. higher than the resin constituting the adhesive layer, and a part or all of the individual conductive fine particles are formed. In the method of manufacturing an electrically conductive adhesive sheet having anisotropy that is present in the core film and the conductive fine particles are arranged in a predetermined arrangement in the core film surface, the surface of the core film having holes that do not penetrate therethrough Forming a first adhesive layer on the surface opposite to the surface, and then forming a second adhesive layer on the other surface of the core film after putting conductive fine particles in the holes. Conductive adhesive sheet manufacturing method of the symptoms.   The manufacturing method of the electroconductive adhesive sheet of Claim 1 including the process of forming the hole which has not penetrated in the core film by laser irradiation.   The conductive fine particles are fine particles made of copper, gold, silver, nickel, palladium, indium, tin, lead, zinc, bismuth, an alloy of any of these metals, or carbon, or fine particles having a metal coating on the surface. The method for producing a conductive adhesive sheet according to claim 1, wherein:

Images