JP2008110384A - Porous resin film and its punching method, anisotropic conductive sheet using the resin film, electric inspection method and circuit connection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous resin film having a large number of through-holes of high roundness at a fine pitch. <P>SOLUTION: A large number of laser beams branched from one laser beam are generated by an optical apparatus 51 for laser beam machining. The large number of laser beams are applied to a porous resin film 2 to simultaneously form a large number of through-holes 5 penetrating in the film thickness direction in the resin film 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an anisotropic conductive sheet used for inspection of a semiconductor integrated circuit, a porous resin film suitably used as an intermediate material thereof, a perforation method thereof, and an electrical inspection method using the anisotropic conductive sheet And a circuit connection method.

Conventionally, a burn-in test has been performed as one of screening methods for removing an initial failure of a semiconductor device. In this burn-in test, accelerated stress higher than the operating conditions of the semiconductor device is applied to accelerate failure occurrence and remove defective products in a short time.
For example, a large number of packaged semiconductor devices are arranged on a burn-in board, and a power supply voltage and an input signal that cause acceleration stress are applied from outside in a high-temperature bath for a certain period of time. Thereafter, the semiconductor device is taken out and a determination test for a non-defective product and a defective product is performed. In the determination test, an increase in leakage current due to a semiconductor device defect, a defective product due to a multilayer wiring defect, a contact defect, and the like are determined. The semiconductor device is generally a surface-mounted LSI such as a BGA (Ball Grid Array), an LGA (Land Grid Array), or a PLCC (Plastic Leaded Chip Carrier).

For example, when a burn-in test of a semiconductor device is performed, the test is performed via an electrode pad on the surface of a surface-mounted LSI such as the BGA, LGA, or PLCC.
At that time, in order to compensate for the contact failure due to the variation in the electrode height between the electrode pad of the semiconductor device and the head electrode of the inspection jig, the conductivity difference between these electrodes is usually only in the film thickness direction. The test is performed with an isotropic conductive sheet (interposer) sandwiched in between. This anisotropic conductive sheet (also referred to as an anisotropic conductive film) exhibits conductivity only in the film thickness direction in a conductive portion arranged according to a pattern corresponding to the surface electrode.

The anisotropic conductive sheet is not only used as a component part for inspection jigs for burn-in testing, but also for connecting sockets and electrical connectors between LSIs and printed circuit boards (PCBs), and for connecting printed circuit boards. It is used as an electrical connector.
This anisotropic conductive sheet uses an electrically insulating porous resin film formed of a synthetic resin as a base film, and forms a plurality of through holes penetrating in the film thickness direction at a plurality of locations on the base film. It is manufactured by attaching a conductive metal to the inner wall surface of the hole to form a conducting portion (see [Claim 9] and [Claim 10] of Patent Document 1).

Examples of a method for forming a through-hole in the film thickness direction at a specific position of the porous resin film include a chemical etching method, a thermal decomposition method, an ablation method using laser light or soft X-ray irradiation, and an ultrasonic method.
Among these, as a method for producing an anisotropic conductive sheet using a porous PTFE membrane (porous polytetrafluoroethylene membrane) as a base membrane, there is a production method comprising the following steps (1) to (5) (patent) (Refer to [0038] and [0039] of Document 1.)

(1) Step of forming a three-layered laminate by fusing a PTFE film as a mask layer on both sides of a base film made of a porous PTFE film (2) From the surface of one mask surface, in a predetermined pattern Step of forming through-holes by irradiation of synchrotron radiation or laser light having a wavelength of 250 nm or less through a light shielding sheet having a plurality of independent light transmitting portions (3) All surfaces of the laminate including the wall surfaces of the through-holes (4) Step of peeling the mask layer on both sides of the laminate (5) Electroless plating on the resin part of the porous structure on the wall surface of the through hole by electroless plating Adhesion process

JP 2004-265844 A

  In the manufacturing process of the anisotropic conductive sheet, as a method of forming a through hole by irradiating the laminated body with laser light, it is placed on the movable stage of the laminated body and penetrated while moving the movable stage at a predetermined pitch. There are a method of drilling holes one by one (first method) and a method of simultaneously drilling a plurality of through-holes simultaneously by a large number of laser beams transmitted through the light shielding sheet (second method) as described above. .

However, the first method of drilling through-holes one by one in the laminate has a drawback that it is difficult to perform high-precision drilling when the object to be drilled is a porous resin film. That is, when the porous resin film is perforated with laser light, for example, as shown by the phantom line in FIG. 11, the through-hole 5 of the porous resin film 2 is caused by the pressure received from the laser light during the previous perforation. The surrounding height may be lowered. For this reason, particularly in the case of drilling at a fine pitch, the distance difference from the next drilling point is short and the variation in film thickness becomes remarkable, and the roundness of the through-hole 5 deteriorates and high-precision drilling is difficult. is there.
This is particularly noticeable when a femtosecond laser is used, which exhibits a behavior close to cutting rather than fusing due to the use of high-power laser light.

On the other hand, the second method using the light shielding sheet does not have the inconvenience as described above, but on the other hand, since the shape of the opening of the light shielding sheet is easily deformed by the heat received from the laser light, the porous resin thin film is formed. On the other hand, drilling may not be possible at a fine pitch.
In view of such circumstances, an object of the present invention is to provide a porous resin film having a large number of through holes having a fine pitch and a high roundness, a method for perforating the resin film, and the like.

In the porous resin film perforation method of the present invention, a large number of laser beams branched from one laser beam are generated by an optical device for laser processing, and the porous resin film is irradiated with the many laser beams to obtain a film thickness. A large number of through holes penetrating in the direction are simultaneously drilled in the base film.
According to this drilling method, by irradiating a porous resin film with a large number of laser beams, a large number of through-holes penetrating in the film thickness direction are simultaneously drilled in the resin film, so that the thickness of the base film varies. A large number of through holes can be drilled without any. For this reason, the roundness of the through-holes can be improved as compared with the case where the through-holes are drilled one by one. Specifically, the roundness of many through-holes is 0.9 to 1.1. A porous resin film within the range of is obtained.
In addition, according to the perforation method, not a laser beam that has passed through the opening of the light shielding sheet, but a large number of laser beams that are branched from one laser beam (for example, a laser beam that is branched by a DOE or the like described later) is used. Therefore, it is difficult for variations in the shapes of a large number of laser beams to occur, and therefore, it is possible to perforate the porous resin film at a fine pitch.

By the way, a laser beam is deflected by a galvanometer mirror and condensed by a lens, and is reflected by a galvanometer mirror, a galvanometer scanner, and a galvanometer mirror as an optical device for laser processing that instantaneously punches a workpiece. Some include an fθ lens that condenses laser light, and an XY table that moves a workpiece in the XY directions and changes a scanning area.
However, it is difficult to reduce the processing time required by the market because the capabilities of the galvano scanner and the XY table are approaching the limits. Therefore, in addition to the galvanometer mirror and the fθ lens, there is known an optical apparatus for laser processing in which a diffractive optical element (DOE) that branches a laser beam into a plurality of laser beams is introduced into an optical path.

As such an apparatus, for example, in the apparatus described in Japanese Patent No. 3458759, a diffractive optical element is disposed on an optical path between a laser oscillator and a galvanometer mirror, and the deflected branched laser light is collected by an fθ lens. This enables high-speed machining.
However, when fine drilling is performed with the laser processing optical device described in the above-mentioned patent publication, the branched laser light branched by the diffractive optical element is deflected by two angle-adjusted galvanometer mirrors and used as an fθ lens. Scanned through. At this time, there is a problem in principle that the pitch of the spot group of the branched laser light slightly changes depending on the scanning position on the workpiece. For this reason, there is a problem in that the condensing position at the time of scanning with the laser beam is shifted, and the pitch accuracy of the hole to be processed is lowered.

This is because the branch angle of each branch laser beam (angle formed with the optical axis) and the deflection angle of the laser beam by the galvanometer mirror are not a simple sum.
In other words, if the X and Y components of the branching angle of a certain branched laser beam are α, β, the X direction, and the Y direction, the deflection angles by the two galvanometer mirrors (beam swing angles by mirror oscillation) are ξ and ζ. If the X component and the Y component of the incident angle to the lens are simple sums such as γ = α + ξ and η = β + ζ, the spot pitch on the workpiece is ΔX = f × Δγ = f × Δα, ΔY = f × Δη = f × Δβ, and the pitch does not change depending on the deflection angles ξ and ζ. Here, f is the focal length of the fθ lens.

  However, in practice, the simple sum of the branch angle and the deflection angle as described above does not hold in principle. Although the detailed description is omitted, the conclusion is that γ≈ (α + ξ) √ (1 + tan2η) and η≈β√ (1 + tan2ξ) + ζ are complicated relational expressions. Accordingly, the spot pitches are ΔX≈f × Δα√ (1 + tan 2 (β√ (1 + tan 2ξ) + ζ)), ΔY≈f × Δβ√ (1 + tan 2ξ), and the pitch changes depending on the deflection angles ξ and ζ. is there.

  Accordingly, the present invention provides a laser oscillator that generates laser light as an optical apparatus for laser processing used in the method for punching a porous resin thin film, and deflects the laser light generated from the laser oscillator at a predetermined deflection angle. A galvanometer mirror, an fθ lens that condenses the laser beam deflected by the galvanometer mirror, and a plurality of laser beams that are arranged on the optical path between the fθ lens and the object to be processed and are collected by the fθ lens. It is recommended to use one having a diffractive optical element that branches into a laser beam.

According to such an optical device for laser processing, since the laser beam condensed by the fθ lens is branched into a plurality of laser beams by the diffractive optical element, high-speed processing is possible.
Further, since the branch beam is not deflected by the galvanometer mirror, the above-mentioned problem that the pitch accuracy of the spot is lowered because the branch angle and the deflection angle do not become a simple sum is eliminated. Accordingly, it is possible to increase the accuracy of the light collection position during the scanning of the laser beam, and it is possible to improve the pitch accuracy of the through holes opened in the porous resin film that is the object to be processed.

  As the fθ lens, an image side telecentric optical system is preferable. In an fθ lens that is not image-side telecentric, an angle is given to the laser beam emitted from the fθ lens depending on the beam deflection angle by the galvanometer mirror. When the deflection angle is small and close to the optical axis, the laser beam is almost parallel to the optical axis, but as the deflection angle increases, the laser light is emitted obliquely from the fθ lens. When the oblique laser beam is incident on the diffractive optical element, the laser beam is branched at a branching angle slightly different from that in the case of vertical incidence. In the mathematical expression, it is expressed as sin α + sin θin∝λ.

  Here, θin is the angle at which the laser beam is incident on the diffractive optical element, and λ is the wavelength of the laser beam. On the other hand, in the case of an image-side telecentric fθ lens, the laser beam emitted from the fθ lens is substantially vertical regardless of the beam deflection angle by the galvanometer mirror. By using the image-side telecentric fθ lens, the laser light enters the diffractive optical element almost vertically (sin θin≈0), and the variation in the branching angle that occurs in the case of oblique incidence is suppressed. There is an effect of further improving the accuracy of the light collection position on the workpiece.

Moreover, it is preferable that the said laser processing optical apparatus is provided with the position adjustment means which adjusts the position of the said diffraction type optical element in an optical axis direction.
In this case, by adjusting the position of the diffractive optical element in the optical axis direction and changing the distance between the diffractive optical element and the object to be processed, the pitch of the branch spot group can be changed within a relatively large range.

Furthermore, it is preferable that the optical apparatus for laser processing includes angle adjusting means for adjusting a rotation angle with the axis of the diffractive optical element as a rotation axis.
In this case, if the rotation angle with the axis of the diffractive optical element as the rotation axis is changed, the spot group of the branched laser beam will also rotate and change its direction. Can be easily adjusted to the appropriate orientation.

As described above, in the porous resin film obtained by the drilling method of the present invention, the roundness of many through holes is within the range of 0.9 to 1.1.
Therefore, if a conductive substance is attached to the inner wall surface of each through hole of this porous resin film, an anisotropic conductive sheet having conductivity only in the film thickness direction is obtained, and the roundness of the through hole is high. Therefore, the conductive portions of the anisotropic conductive sheet can also be arranged at a fine pitch.
The anisotropic conductive sheet can be used as a contactor for an electrical inspection method such as a burn-in test, or can be used as a connector for connecting printed circuit boards.

  As described above, according to the present invention, a porous resin film having a large number of through-holes having a fine pitch and a high roundness can be obtained. Further, by using this porous resin film as the base film of the anisotropic conductive sheet, the conductive portions of the sheet can be arranged at a fine pitch.

[Structure of anisotropic conductive sheet]
FIG. 1 is a perspective view showing an example of the structure of the anisotropic conductive sheet 1. FIG. 2 is a cross-sectional view of the anisotropic conductive sheet 1 taken along the line II-II shown in FIG.
As shown in FIGS. 1 and 2, the anisotropic conductive sheet 1 of the present embodiment includes a rectangular flat base film 2 (having a thickness of about 120 μm, for example) made of a porous resin having a large number of micropores, A number of through holes 5 penetrating between the first surface 3 and the second surface 4 of the base film 2 in the film thickness direction, and a cylindrical electrode film serving as a conduction portion formed in the inner wall portion of the through hole 5 6 is provided. Thereby, the anisotropic conductive function of having conductivity in the film thickness direction and no conductivity in the in-plane direction is provided.

The through holes 5 have a diameter d of about 10 μm and a pitch p of about 25 μm. Since the anisotropic conductive sheet 1 is used under a high temperature environment such as a burn-in test of a semiconductor device, the base film 2 needs to have high heat resistance. And in order to prevent the electrical short circuit between each cylindrical electrode film 6 used as a conduction | electrical_connection part, the base film 2 needs to be an insulator.
Moreover, as will be described later, in this embodiment, the base film 2 is made of a synthetic resin of a porous film in order to give the anisotropic conductive sheet 1 both elasticity and high strength. In a conductive sheet used for a burn-in test of a semiconductor device or the like, it is preferable that the diameter of the through hole 5 is 15 μm or less in order to obtain a fine pitch.

  Examples of the synthetic resin material constituting the base film 2 made of the porous resin film include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl vinyl ether. Fluororesin such as polymer (PFA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymer, ethylene / tetrafluoroethylene copolymer (ETFE resin); polyimide (PI), polyamideimide (PAI), Engineering such as polyamide (PA), modified polyphenylene ether (mPPE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polysulfone (PSU), polyethersulfone (PES), liquid crystal polymer (LCP) Grayed plastic, and the like.

Among these, PTFE is preferable in consideration of heat resistance, workability, mechanical properties, dielectric properties, and the like. Therefore, in this embodiment, a porous PTFE film (porous polytetrafluoroethylene film) is used as the base film 2.
In this embodiment, as will be described later, since a porous PTFE membrane obtained by a stretching method is used, the base membrane 2 is composed of very thin fibers (fibrils) formed by PTFE and the fibers. It has a fine fibrous structure (porous structure) composed of connected nodes (nodes).

  In the present embodiment, the porous PTFE membrane used as the base membrane 2 preferably has a porosity of about 20 to 80%. The porous PTFE membrane preferably has an average pore diameter of 10 μm or less or a bubble point of 2 kPa or more from the viewpoint of fine pitching of the conducting part, and an average pore diameter of 1 μm or less or a bubble point of 10 kPa or more. It is more preferable. The film thickness of the porous PTFE membrane can be appropriately selected according to the purpose of use and the place of use, but is usually about 0.05 to 3 mm.

The cylindrical electrode film 6 has a multilayer metal plating layer (electroless plating layer) having a tube thickness t of 0.2 to 50 μm on the inner wall portion including the inner wall surface of the through hole 5 and the inside of the fine hole. That is, the cylindrical electrode film 6 is formed in the surface region including the fibers of the porous PTFE film by the catalyst particles and the metal that have entered the micropores from the inner wall surface during the electroless plating.
In the present embodiment, the cylindrical electrode film 6 is constituted by a Ni—P alloy layer and an Au layer, which are Ni alloy layers deposited using catalyst catalyst particles attached to the fiber surface as nuclei. In the present embodiment, the P content in the Ni—P alloy layer is 5 wt% or more, and the electrical resistance value is low. This feature point will be described later.

  As described above, the cylindrical electrode film 6 is preferably coated with a noble metal or a noble metal alloy in order to improve oxidation prevention and electrical contact. As the noble metal, palladium, rhodium, gold or silver is preferable from the viewpoint of low electric resistance. The thickness of the noble metal layer is preferably 0.05 to 0.5 μm, and more preferably 0.01 to 0.1 μm. If the thickness of the coating layer is too thin, the effect of improving electrical contact is small, and if it is too thick, the production cost increases, so that neither is preferable. For example, when the surface of the cylindrical electrode film 6 is coated with gold, it is effective to perform substitution gold plating after coating the base metal layer with nickel of about 8 nm or more.

As described above, during electroless plating, the catalyst particles penetrate not only from the inner wall surface of the through-hole 5 but also from the micropores of the porous PTFE film and adhere to the fiber surface. The porous PTFE membrane is deposited by penetrating into the inside from the micropores. That is, not only the multilayer metal plating layer but also the fibers of the porous PTFE film are mixed in the region (inner wall portion) of the tube thickness t shown in FIG.
Since this cylindrical electrode film 6 is formed by adhering to the surface of the resin portion having a porous structure, the cylindrical electrode film 6 itself has a characteristic of being porous. That is, by applying a compressive load in the film thickness direction of the anisotropic conductive sheet 1, conductivity is maintained only in the film thickness direction of the anisotropic conductive sheet 1 while maintaining insulation between the cylindrical electrode films 6. Imparted (anisotropic conductivity). Further, when the compressive load is removed, the entire anisotropic conductive sheet 1 including the cylindrical electrode film 6 is elastically recovered, so that the anisotropic conductive sheet 1 of this embodiment can be used repeatedly.

  In the present embodiment, the tube thickness t of the cylindrical electrode film 6 is about 1 μm, and when the predetermined compression amount (about 30 μm) is applied, the resistance value of the cylindrical electrode film 6 that is a conducting portion is 0.1Ω. It is formed to be as follows. The compression amount is normally set to about 1/4 of the thickness of the base film 2. In this embodiment, since the base film 2 having a thickness of about 120 μm is used, the compression amount is set to 30 μm. Yes. However, since the required resistance value differs depending on the type of the anisotropic conductive sheet 1 and the object to be inspected, the resistance values of the respective cylindrical electrode films 6 having variations in the contact degree are all equal to or less than the desired resistance values. Any compression amount can be used.

[Manufacturing process of anisotropic conductive sheet]
[First step: Production of base film]
FIGS. 3A to 3E are perspective views showing a manufacturing process of the anisotropic conductive sheet 1 according to the first embodiment. Hereinafter, the manufacturing process of the anisotropic conductive sheet 1 will be described with reference to FIGS.

  In the step shown in FIG. 3A, a base film 2 that is a porous PTFE film is prepared. Generally, methods for producing a porous film using a synthetic resin include a pore making method, a phase separation method, a solvent extraction method, a stretching method, a laser irradiation method, and the like. By forming a porous film using a synthetic resin, elasticity can be given in the film thickness direction, and the dielectric constant can be further lowered. In particular, the porous film obtained by the stretching method (porous PTFE film in this embodiment) is excellent in heat resistance, processability, mechanical properties, dielectric properties, etc., and has a uniform pore size distribution. Since it is easy to obtain, it is an optimal material for the base film 2 of the anisotropic conductive sheet 1.

The porous PTFE membrane of the present embodiment can be produced, for example, by the method described in Japanese Patent Publication No. 42-13560. In this method, first, a liquid lubricant is mixed with an unsintered powder of PTFE, and extruded into a tube shape or a plate shape by ram extrusion. When a thin sheet is desired, the plate is rolled with a rolling roll. After the extrusion rolling process, the liquid lubricant is removed from the extruded product or the rolled product as necessary.
When the extruded product or the rolled product thus obtained is stretched at least in a uniaxial direction, unsintered porous PTFE is obtained in the form of a film. An unsintered porous PTFE membrane is heated to a temperature of 327 ° C. or higher, which is the melting point of PTFE, and fixed to prevent shrinkage. A quality PTFE membrane is obtained. When the porous PTFE membrane is in a tube shape, a flat membrane can be obtained by opening the tube.

[Second step: Drilling through holes]
Next, in the step shown in FIG. 3 (b), the mask films 11 and 12 are fused on both surfaces of the base film 2 which is a porous PTFE film obtained by the stretching method to form a laminate 14 having a three-layer structure. The through hole 5 is formed in the entire laminated body 14 (see the broken line). As the mask films 11 and 12, a PTFE film made of the same material as that of the base film 2, preferably a porous PTFE film is used. At this time, for example, the three layers of porous PTFE membranes are fused to each other by sandwiching both surfaces of the three porous PTFE membranes stacked between two stainless steel plates and heating each stainless steel plate to a high temperature. Can do.

Generally, as a method of forming a through-hole in a film thickness direction at a specific position of a synthetic resin, for example, there are a chemical etching method, a thermal decomposition method, an ablation method by laser light or soft X-ray irradiation, an ultrasonic method, etc. In the present embodiment, an optical device 51 for laser processing that punches a large number of through holes 5 at once is used. The optical device 51 and the drilling method using the optical device 51 will be described later.
The arrangement pattern of the multiple through-holes 5 can be any shape such as a circle, a star, an octagon, a hexagon, a quadrangle, and a triangle. Since the hole diameter of the through-hole 5 determines the size of the cylindrical electrode film 6 of the anisotropic conductive sheet 1 to be manufactured, it may be appropriately formed according to the size of the cylindrical electrode film 6 to be manufactured.

  When the anisotropic conductive sheet 1 is used as an interposer for inspection (burn-in test or the like) of a semiconductor device mounted with high density, the pitch p between the through holes 5 should be fine pitch of 30 μm or less. Is preferred. In the present embodiment, the pitch p is 25 μm. The diameter d of the through hole 5 by this method is generally about 5 to 100 μm, but is preferably 15 μm or less in order to cope with fine pitch. In the present embodiment, the diameter d of the through hole 5 is about 10 μm.

[Third step: Application of catalyst]
Next, in the process shown in FIG. 3C, the catalyst is applied to the laminate 14 through conditioning, washing with water, and pre-dip of the laminate 14. The purpose of conditioning is to make the surface of PTFE having water repellency as hydrophilic as possible, and to facilitate the adhesion of catalyst particles in a later step. For the porous PTFE membrane, a solution containing alcohol such as ethanol or a surfactant is used as a conditioner, and the conditioner is infiltrated to each fiber in the porous structure.

And after completion | finish of a pre-dip process, the laminated body 14 is immersed in the catalyst liquid (For example, a tin chloride-palladium chloride colloid liquid) containing Pd, and the surface of each fiber of PTFE which comprises the laminated body 14 is made from Pd compound. The colloidal particles adhering region 15 is formed by adhering the colloidal particles to the surface of each fiber in the surface region such as the inner wall of the through hole 5.
The Pd concentration in the catalyst solution is about 100 ppm. In the colloidal particle adhesion region 15, the colloidal particles are rarely continuous layers, and are often island-shaped layers. At this time, the colloidal particle adhesion region 15 is also formed in the surface region of the exposed portions of the mask films 11 and 12 (the hatched region shown in FIG. 3C). Note that the pre-dip process may be omitted.

  In this step, the catalyst particles are uniformly dispersed and attached to the surface of each fiber of the porous PTFE membrane in the subsequent step, and the electric resistance of the cylindrical electrode membrane 6 formed by electroless plating The value can be suppressed. However, in this step, colloidal particles made of a Pd compound are attached to the surface of the PTFE fiber, and not Pd alone. When the catalyst application step is completed, the laminate 14 is washed with water, and the process proceeds to the next step.

[Fourth step: removal of mask film]
Next, the mask films 11 and 12 are peeled off from both surfaces of the base film 2 in the step shown in FIG. At this time, the colloidal particle forming regions 15 are not formed on both surfaces of the base film 2. On the other hand, a colloidal particle adhesion region 15 is also formed at the side edge of the base film 2. The colloidal particle adhesion region 15 formed in this part is appropriately formed after the end of this step or after the end of electroless plating. Removed.

[Fifth step: electroless plating]
Next, in the step shown in FIG. 3 (e), electroless plating is performed to form the cylindrical electrode film 6, but before that, using dilute hydrochloric acid, dilute sulfuric acid or the like, The process of activating Pd is performed. Thereby, activated catalyst particles 6a are formed. The catalyst particles 6a generally contain a Pd compound (for example, palladium-tin chloride) and simple Pd, and even if all the colloidal particles are not changed to simple Pd, Pd remains on the surface. If it is exposed, the function as a catalyst for electroless plating can be exhibited. Thereafter, the treatment liquid adhering to the surface of the base film 2 is washed away with water.

  In this electroless plating step, catalyst particles having activated catalyst particles 6a as nuclei by electroless Ni-P alloy plating using a solution containing Ni ions such as nickel sulfate and a reducing agent containing phosphinate ions. A Ni—P alloy layer 6b having a thickness of about 0.1 μm is deposited around 6a. Then, it is washed with water. The composition of a solution containing Ni ions, such as nickel sulfate, is 30 g of nickel sulfate per 1 liter of solution, for example, and the composition of the reducing agent containing phosphinate ions is 10 g of sodium phosphinate per 1 liter of solution, for example. It is.

Thereafter, an Au layer 6c having a thickness of about 0.05 μm is formed by displacement gold plating. When an electrochemically noble metal (Ni) is immersed in a solution containing electrochemically noble metal (Au) ions, noble metal ions are reduced by electrons released by the dissolution of the noble metal, A noble metal (Au) coating is deposited on the base metal (Ni) surface. Utilizing this, an Au layer 6c having a thickness of about 0.05 μm is formed on the Ni—P alloy layer 6b.
The cylindrical electrode film 6 including the catalyst particles 6a, the Ni—P alloy layer 6b, and the Au layer 6c is formed through the above steps. Note that the Au layer may be formed by autocatalytic electroless plating after displacement plating. Then, the electroless plating process is completed by drying through water washing and alcohol substitution.

By the way, in a normal electroless plating process, in the process shown in FIG. 3D, first, a Cu layer having a thickness of about 0.1 to 0.2 μm is formed by using electroless plating as a core, A Ni—P alloy layer having a thickness of about 0.01 μm is formed thereon. Thereafter, an Au layer is formed on the Ni—P alloy layer. The Au layer and the Ni-P alloy layer serve to prevent Cu from rusting. The Ni—P alloy layer is a barrier layer for preventing the reaction between Au and Cu.
However, in such a structure of the cylindrical electrode film 6, an oxide of Cu may be deposited while the burn-in test or the like is repeated. In particular, when the pitch p between the cylindrical electrode films 6 is reduced to a fine pitch of 50 μm or less, the tube thickness t of the cylindrical electrode film 6 must be reduced. Reduced reliability.

  Therefore, it is conceivable to increase the thickness of the Ni-P alloy layer to suppress the formation of Cu oxides, but according to experiments, increasing the thickness of the Ni-P alloy layer results in an increase in the hardness of the cylindrical electrode film. When a predetermined amount of compression (for example, about 30 μm) is applied to the cylindrical electrode film during a burn-in test or the like, a phenomenon occurs in which the electrical resistance value of the cylindrical electrode film increases. When examined in detail, this phenomenon is presumed to be caused by the occurrence of microcracks in the Ni-P alloy layer.

The P concentration in the Ni—P alloy layer constituting the cylindrical electrode film of the conventional anisotropic conductive sheet is at most about 4%. This is because it is considered that a high P concentration is not preferable in order to maintain low resistance. However, as a result of creating a Ni-P alloy layer having a P concentration of 4 to 5 wt%, 5 to 7 wt%, and 7 to 9 wt%, the electrical resistance value when the compression amount at the time of the test is applied as the P concentration increases. Turned out to be lower.

FIG. 4 is a table showing the electrical resistance values (values when the amount of compression during the test is added) of the cylindrical electrode film when the P concentration is changed. In addition, when the compression amount at the time of the test is not added, it has been confirmed that the lower the P concentration, the lower the electrical resistance value.
In general, when the anisotropic conductive sheet 1 is used for a burn-in test of a semiconductor device, in order to eliminate measurement errors, the resistance values of the cylindrical electrode films 6 having variations in the contact degree are all desired resistance values ( For example, it should be 0.1Ω or less, and is preferably as small as possible (for example, about 0.1Ω).
Referring to FIG. 4, the P concentration in the Ni—P alloy layer is preferably in the range of 4 to 9 wt%, and more preferably in the range of 5 to 7 wt%.

In the present embodiment, the Ni-P alloy layer 6b is thickened from about 0.01 .mu.m to about 0.1 .mu.m, and the electrical resistance value can be suppressed to a low level. The Au layer 6c can be formed by displacement gold plating thereon.
As a result, since there is no precipitation of Cu oxide, high reliability can be obtained, and furthermore, the electric resistance value when the amount of compression during the test is added can be lowered. That is, the tube thickness t of the cylindrical electrode film 6 can be reduced to cope with a fine pitch.

[Laminated sheet body and inspection unit]
Next, a laminated sheet body and an inspection unit using the anisotropic conductive sheet 1 of the present embodiment will be described.
FIG. 5 is a side view showing a schematic configuration of the inspection unit 20 of the present embodiment. FIG. 6 is a cross-sectional view illustrating a first example of the laminated sheet body 30 in the inspection unit 20. FIG. 7 is a cross-sectional view illustrating a second example of the laminated sheet body 40 in the inspection unit 20.

  As shown in FIG. 5, the inspection unit 20 of the present embodiment includes a circuit board 10 on which the anisotropic conductive sheet 1 is placed and a semiconductor device 17 that is an object to be inspected up to just above the anisotropic conductive sheet 1. A device guide 13 for guiding, a pressing lid 18 for applying a compressive load by pressing the semiconductor device 17 onto the circuit board 10, and a fixing member 19 for fixing the circuit board 10 to a work desk or the like. I have. The device guide 13, the pressing lid 18, and the fixing member 19 constitute a holding unit that holds the semiconductor device 17, the anisotropic conductive sheet 1, and the circuit board 10 so as to be electrically connected.

  The semiconductor device 17 that is an object to be inspected is, for example, an LSI package in which BGA terminals 17a (ball grid array) are arranged on the back surface. The circuit board 10 has electrodes having an arrangement pattern with the same pitch p as that of the anisotropic conductive sheet 1 on its surface, and electrodes having an arrangement pattern having a pitch larger than that are provided on the back surface. . In addition, although the circuit board 10 shown in FIG. 5 has a pitch conversion function, it does not need to have a pitch conversion function.

In order to perform a test (inspection) using the inspection unit 20 of the present embodiment, the semiconductor device 17 is mounted on the device guide 13, the pressing lid 18 is lowered from above, and the semiconductor device 17 is pressed from the back surface. Then, after bringing the BGA terminal 17a of the semiconductor device 17 into contact with the cylindrical electrode film 6 of the anisotropic conductive sheet 1, a predetermined compression amount is applied to the anisotropic conductive sheet 1 (for example, about 30 μm). Thereby, even if the contact position of each BGA terminal 17a of the semiconductor device 17 and each electrode on the circuit board 10 varies in the vertical direction, it is absorbed by the elasticity of the anisotropic conductive sheet 1.
Then, a burn-in test or the like is performed by bringing the electrode of the inspection device disposed below the circuit board 10 into contact with the back electrode of the circuit board 10.

FIG. 6 is a cross-sectional view of a laminated sheet body 30 in which the circuit board 10 that does not have a pitch conversion function and the anisotropic conductive sheet 1 are bonded and integrated. The anisotropically conductive sheet 1 and the circuit board 10 having a fine pitch are bonded and integrated in a state where the tubular electrode film 6 and the electrode wiring 31 are in contact with each other.
FIG. 7 is a cross-sectional view of a composite laminated sheet body 40 in which two laminated sheet bodies are stacked. As shown in FIG. 7, in this laminated sheet body 40, a first anisotropic conductive sheet 41 having a fine pitch is bonded onto a first circuit board 42 having a pitch conversion function.

At this time, the cylindrical electrode film 6A of the first anisotropic conductive sheet 41 and the wiring electrode 31A of the first circuit board 42 are bonded together. A second anisotropic conductive sheet 43 having a relatively large pitch is bonded to the second circuit board 44 that does not have a pitch conversion function. At this time, the cylindrical electrode film 6B of the second anisotropic conductive sheet 43 and the wiring electrode 31B of the second circuit board 44 are bonded together.
The first circuit board 42 and the second anisotropic conductive sheet 43 are in a state where the electrode 31A of the first circuit board 42 and the cylindrical electrode film 6B of the second anisotropic conductive sheet 43 are in contact with each other. And are pasted together.

According to the laminated sheet body 30 shown in FIG. 6, the anisotropic conductive sheet 1 is fine pitched with the high-density mounting of the semiconductor device, so that the anisotropic conductive sheet 1 and the electrodes on the circuit board 10 are separated. Although there is a possibility that the labor for positioning may increase, by using the laminated sheet body 30 of the present embodiment, the work can be speeded up, and a remarkable effect can be exhibited.
According to the composite-type laminated sheet body 40 shown in FIG. 7, in addition to the effect that the operation can be speeded up like the laminated sheet body 30 shown in FIG. The pitch of the conductive sheet 41 can be enlarged on the second circuit board 44 and connected to the test apparatus. In addition, since the two anisotropic conductive sheets 41 and 43 are interposed, the function of absorbing the variation in the vertical direction of the contact position by elasticity is also improved.

According to the inspection unit 20 of the present embodiment shown in FIG. 5, the laminated sheet bodies 30 and 40 that exhibit the above-described effects are provided, and the following effects can be further exhibited.
Even when the semiconductor device 17 is an LSI package mounted with high density, it is caused by a short circuit between the cylindrical electrode films 6 of the anisotropic conductive sheet 1 having a fine pitch or a high electrical resistance of the cylindrical electrode film 6. It can be used for a burn-in test or the like without incurring a measurement error.
Since the semiconductor device 17, the anisotropic conductive sheet 1, and the circuit board 10 are held by the device guide 13, the holding lid 18, and the fixing member 19, which are holding means, so as to be electrically connected, Work becomes highly efficient. In addition, since the shape and position of the device guide 13 and the pressing lid 18 are provided so as to be compatible with the anisotropic conductive sheet 1 that has been fine pitched in advance, the BGA of the semiconductor device 17 is also used during a burn-in test or the like. The operation of aligning the terminal 17a and the cylindrical electrode film 6 of the anisotropic conductive sheet 1 becomes quick.

In the above embodiment, the laminated body 14 is formed by sandwiching the base film 2 from both sides with the mask films 11 and 12, and then the through holes are formed and immersed in the catalyst solution. There is no need to form. For example, the steps shown in FIGS. 3C to 3E such as formation of through holes, application of a catalyst, activation treatment, and electroless plating may be performed by the base film 2 alone.
In that case, an electroless plating layer is formed on both the front and back surfaces of the base film 2, but may be removed by polishing or the like. However, by forming the through hole 5 in the laminate 14 as in the present embodiment, the highly accurate through hole 5 can be obtained. In addition, the manufacturing cost can be reduced by not forming an extra electroless plating layer.

In the above embodiment, the catalyst particles are attached to the PTFE fiber surface by conditioning, pre-dip, catalyst application and activation treatment. However, the method for fixing the catalyst particles is not limited to this procedure. Any method may be used. The catalyst particles are not limited to those obtained by activating the Pd compound, and may be other metals, inorganic materials other than metals, organic conductors, and the like.
Moreover, in the said embodiment, although the Ni-P alloy layer was used as a Ni alloy layer, you may use a Ni-B alloy layer.

[Optical device for laser processing]
Next, the laser processing optical apparatus for punching a large number of through holes 5 at once will be described.
FIG. 8 is a perspective view showing a schematic configuration of the laser processing optical device 51 of the present embodiment, and FIG. 9 is a perspective view showing an essential part thereof.
The laser processing optical device 51 includes a laser oscillator 52 that generates laser light, a bend mirror 3 provided in the vicinity of the laser oscillator 52, a pair of galvanometer mirrors 54 that deflect laser light, and the galvanometer mirror 54. And a fθ lens 56 that condenses the laser light deflected by the galvanometer mirror 54.

The optical device 51 for laser processing includes a diffractive optical element 58 disposed on the optical path between the fθ lens 56 and the workpiece 57, a position adjusting unit and an angle adjusting unit of the diffractive optical element 58. , And a control device 59 for controlling the laser oscillator 52 and the galvano scanner 55.
The workpiece 57 is the base film 2 of the anisotropic conductive sheet 1, and a plurality of through-holes 4 are drilled (perforated process) on the surface thereof by laser irradiation.

The laser light generated by the laser oscillator 52 is, for example, a carbon dioxide laser or a YAG laser (including a fundamental wave or a harmonic thereof). In the case of this embodiment in which the through holes 5 are drilled in the base film 2 made of a porous resin film, it is preferable to use a femtosecond laser.
The reason is that the femtosecond laser instantaneously generates a large power of 1 million watts or more, so the influence of heat is small and it shows a behavior close to cutting rather than fusing, enabling highly accurate drilling. Because.

The pair of galvanometer mirrors 54 deflects the laser beam output from the laser oscillator 52 at a predetermined deflection angle and swings it in the X-axis direction and the Y-axis direction on the workpiece 57. The control device 59 controls the laser light emission by the laser oscillator 52 and drives the galvano scanner 55 to oscillate the galvano mirror 54 to change the laser light incident position on the fθ lens 56.
The fθ lens 56 is an image-side telecentric optical system. By using the fθ lens 56, both the on-axis and off-axis laser beams deflected in various directions by the galvanometer mirror 54 are used as the optical axis. It becomes substantially parallel, and is substantially perpendicularly incident on the surface of the object 57 to be focused on the surface. By doing so, a large number of through-holes 5 arranged discretely in a grid, for example, can be opened on the surface of the workpiece 57.

The diffractive optical element 58 (DOE) disposed on the optical path between the fθ lens 56 and the workpiece 57 has a plurality of beams having a desired spatial distribution with different exit angles by diffracting one incident beam. Each branched laser beam is condensed by the fθ lens 56 and irradiated to the object 57 to be processed.
That is, since the diffractive optical element 58 generates a plurality of laser beams at once, a large number of holes can be instantaneously formed on the workpiece 57 while the galvanometer mirror 54 is stationary. Normally, only one place can be processed by one laser beam oscillation, but for example, by using the diffractive optical element 88 designed to perform 25 spectroscopy, 25 points can be processed simultaneously by one laser oscillation. Drilling can be performed at high speed.

FIG. 10 shows the stage mechanism 60.
The stage mechanism 60 includes a position adjusting unit 61 that adjusts the position of the diffractive optical element 58 in the optical axis direction and an angle adjusting unit 62 that adjusts the rotation angle about the axis of the diffractive optical element 58 as a rotation axis. It is structured.
The position adjustment means 61 includes an adjustment unit main body 61h, an adjustment roller 61r, and the like. By rotating the adjustment roller 61r, the diffractive optical element 58 moves in the Z-axis direction, that is, the optical axis direction. By doing so, the distance L from the diffractive optical element 88 to the workpiece 57 changes.

On the other hand, the angle adjusting means 62 includes an adjusting unit main body 62h, an adjusting roller 62r, and the like. By rotating the adjusting roller 12r, the rotation angle with the axis of the diffractive optical element 58 as the rotation axis changes. ing. Although detailed description of the position adjusting means 61 and the angle adjusting means 62 is omitted, commercially available known means can be used for each of the adjusting means 61 and 62.
Further, in the stage mechanism 60 shown in FIG. 3, the position adjusting means 61 and the angle adjusting means 62 are integrally configured, but each means may be configured separately. A configuration is also possible in which the stage mechanism that forms the angle adjusting means is connected to the stage mechanism that forms the position adjusting means and is movable up and down.

Here, regarding the position of the diffractive optical element 58 in the optical axis direction, when the pitch of the spot group of the branched laser light is P1, the following relational expression (1) is established.
P1 = Ltanθ (1)
However, in the above relational expression (1), L is the distance from the diffractive optical element 58 to the workpiece 57, and θ is a spot on the optical axis relative to the diffractive optical element 58 and other spots. It is an angle to make.

Therefore, if the distance from the diffractive optical element 58 to the workpiece 57 is changed by, for example, 5%, the pitch of the spot group changes by 5%.
On the other hand, if the pitch of the spot group when the diffractive optical element 58 is positioned between the laser oscillator 52 and the galvanometer mirror 54 is P2, the following relational expression (2) is established.
P2 ∝ λf1- (M / f) Δ (2)
Where λ is the wavelength of the laser light, f is the focal length, M is the magnification, and Δ is the distance the diffractive optical element 58 is moved.

In the relational expression (2), since M = 1/10 to 1/100 is small, the change amount of the pitch P2 of the spot group with respect to the change amount of Δ is very small. Accordingly, when the distance L from the diffractive optical element 58 to the workpiece 57 is changed by the position adjusting means 61, the spot group of the branched laser light is more than that when the diffractive optical element 58 is positioned between the galvanometer mirrors 54. The pitch P1 can be changed within a large range.
Further, if the angle adjustment means 62 changes the rotation angle about the axis of the diffractive optical element 58 as the rotation axis, the branch laser beam spot group also rotates and changes its direction, so that the branch laser beam spot group is processed. It is possible to easily adjust the object 57 to an appropriate direction.

When drilling the workpiece 57 with the laser processing optical device 51, the laser light generated by the laser oscillator 52 is emitted by the oscillator 52 and two vents provided in the vicinity of the laser oscillator 52. The traveling direction is changed by the mirror 53, deflected by the pair of galvanometer mirrors 54, and guided to the fθ lens 56.
The laser light emitted from the galvanometer mirror 54 is divided by the diffractive optical element 58 held by the stage mechanism 60 while being condensed by the fθ lens 56, and becomes a branched laser light to have a focal length of the fθ lens 56. Accordingly, the processing object 57 is irradiated. Then, the galvano mirror 54 changes the irradiation position of the branched laser beam on the workpiece 57 by oscillating the direction of travel of the laser beam (deflecting the laser beam), and a plurality of holes are drilled in the workpiece 57. Is done at high speed.

According to the laser processing optical device 51 of the present embodiment, the laser beam condensed by the fθ lens 56 is branched into a plurality of laser beams by the diffractive optical element 58, so that high-speed processing is possible. The angle of the laser beam deflected by the galvanometer mirror 54 is corrected substantially parallel to the optical path axis by the fθ lens 56, and the laser beam in a state perpendicular to the workpiece 57 is branched by the diffractive optical element. This eliminates the problem in principle that the pitch of the spot group of the branched laser light changes depending on the scanning position on the workpiece 57.
Accordingly, it is possible to improve the accuracy of the light collection position during the scanning of the laser beam, and to improve the pitch accuracy of the holes to be drilled in the workpiece 57.

For this reason, in the manufacturing process of the anisotropic conductive sheet 1 shown in FIG. 3, the following effects can be obtained by using the optical device 51 in the drilling process of the through hole 5 of the base film 2 of the sheet 1.
That is, by irradiating the base film 2 made of a porous resin film with a large number of laser beams, a large number of through holes 5 penetrating in the film thickness direction are simultaneously drilled in the base film 2. A large number of through holes 5 can be drilled without variation. For this reason, the roundness of the through-hole 5 can be improved compared with the case where the through-hole 5 is drilled one by one.
More specifically, using the laser processing optical device 51 (however, a femtosecond laser is used as the laser beam), the 50 through holes 5 are collectively formed in the stacked body 14 shown in FIG. After perforating, the mask films 11 and 12 on the front and back sides were peeled off and the simple substance of the base film 2 was taken out. The roundness of the many through holes 5 in the base film 2 was 0.9 to 1.1. It was confirmed that it was within the range.

Further, according to the punching method using the laser processing optical device 51 of the present embodiment, a large number of laser beams branched from one laser beam are used instead of the laser beam that has passed through the opening of the conventional light shielding sheet. Therefore, it is difficult for variations in the shapes of a large number of laser beams to occur, and therefore, it is possible to perforate the porous resin film at a fine pitch.
Therefore, if the anisotropic conductive sheet 1 is manufactured by attaching a conductive substance to the inner wall surface of each through hole 5 of the porous resin film 2 having a fine pitch and high roundness as described above, The cylindrical electrode film 6 of the anisotropic conductive sheet 1 also has a high roundness and can be arranged at a fine pitch.

  Furthermore, according to the drilling method using the laser processing optical device 51 of the present embodiment, since the branch beam is not deflected by the galvano mirror 54, the branch angle and the deflection angle do not become a simple sum. This eliminates the problem of a decrease in pitch accuracy. Accordingly, it is possible to improve the accuracy of the condensing position at the time of scanning with the laser beam, and it is possible to improve the pitch accuracy of the through holes 5 opened in the porous resin film 2 that is the processing object 57.

Further, by changing the position of the diffractive optical element 58 in the optical axis direction by the position adjusting unit 61, the pitch P1 of the spot group of the branched laser light can be changed within a relatively large range. The pitch of the holes to be drilled can be easily changed.
Furthermore, since the spot group of the branched laser light can be easily adjusted to an appropriate direction with respect to the workpiece 57 by the angle adjusting means 62, workability is improved.

The laser processing optical device 51 is not limited to the above.
For example, in the above embodiment, it is assumed that the diffractive optical element 58 branches in the same manner regardless of the position on the incident surface irradiated with the laser beam. That is, the diffractive optical element 58 has uniform characteristics over the entire surface.
In this case, a change in the arrangement of the spot group or a large change in the pitch can be dealt with by exchanging the diffractive optical element 58. In addition, if a plurality of diffractive optical elements 58 having different functions are prepared in advance and an exchange means for the diffractive optical element 58 is provided, the diffractive optical element can be changed according to the arrangement of holes and the pitch of the workpiece 57. The element 58 can be exchanged.

On the other hand, the diffractive optical element 58 can also have its surface divided into a plurality of regions and have different beam branching functions in each region. In this case, the arrangement and pitch of the spot groups of the branched laser light vary depending on where the laser light is incident.
This method is very effective in the processing field where the scanning position on the processing object 57 and the arrangement and pitch of the spot group are clearly separated and corresponded. This eliminates the need to prepare a plurality of diffractive optical elements.

It is a perspective view which shows the structure of an anisotropic conductive sheet. It is sectional drawing of the anisotropic conductive sheet at the time of cut | disconnecting by the II-II line | wire of FIG. It is a figure which shows the manufacturing process of an anisotropic electrically conductive sheet, (a) is the cross section of a base film, (b) is the drilling process of a through-hole, (c) is a provision process of a catalyst, (d) is the removal process of a mask. (E) shows an electroless plating step. It is a table | surface of the electrical resistance value of a cylindrical electrode film when P density | concentration is changed. It is a side view which shows schematic structure of a test | inspection unit. It is sectional drawing which shows the 1st example of the lamination sheet body in a test | inspection unit. It is sectional drawing which shows the 2nd example of the lamination sheet body in a test | inspection unit. It is a perspective view which shows schematic structure of the optical apparatus for laser processing. It is a perspective view which shows the principal part of the optical apparatus for laser processing. It is a perspective view of a stage mechanism. It is a schematic diagram which shows the behavior of the porous resin film at the time of punching a through-hole.

Explanation of symbols

1 Anisotropic Conductive Sheet 2 Base Film (Porous Resin Film)
3 First surface 4 Second surface 5 Through-hole 6 Cylindrical electrode film (conduction part)
20 Inspection Unit 30 Laminated Sheet Body 40 Laminated Sheet Body 51 Laser Processing Optical Device 52 Laser Oscillator 54 Galvano Mirror 56 fθ Lens 57 Work Object 58 Diffraction Optical Element 60 Stage Mechanism 61 Position Adjustment Means 62 Angle Adjustment Means

Claims (9)

  A plurality of laser beams branched from one laser beam are generated by an optical device for laser processing, and the porous resin film is irradiated with the many laser beams, and a plurality of through holes penetrating in the film thickness direction are formed in the resin film. A method for perforating a porous resin film, characterized by simultaneously perforating.   The optical apparatus for laser processing condenses a laser oscillator that generates laser light, a galvano mirror that deflects the laser light generated from the laser oscillator at a predetermined deflection angle, and the laser light deflected by the galvano mirror. An fθ lens, and a diffractive optical element that is disposed on an optical path between the fθ lens and the resin thin film that is the object to be processed, and that divides the laser beam condensed by the fθ lens into a plurality of laser beams. The method for perforating a porous resin film according to claim 1.   The method for punching a porous resin film according to claim 2, wherein the fθ lens is an image side telecentric optical system.   4. The method for punching a porous resin film according to claim 2, wherein the laser processing optical device includes a position adjusting means for adjusting a position of the diffractive optical element in an optical axis direction.   5. The porous resin film according to claim 2, wherein the optical apparatus for laser processing includes an angle adjusting unit that adjusts a rotation angle with the axis of the diffractive optical element as a rotation axis. Drilling method. A porous resin film in which a large number of through holes penetrating in the film thickness direction are perforated by a large number of laser beams branched from one laser beam,
A porous resin film, wherein the roundness of the plurality of through holes is in a range of 0.9 to 1.1.   An anisotropic conductive sheet having conductivity only in the film thickness direction, wherein a conductive substance is attached to an inner wall surface of each through hole of the porous resin film according to claim 6.   An electrical inspection method using the anisotropic conductive sheet according to claim 7 as a contactor.   A circuit connection method using the anisotropic conductive sheet according to claim 7 as a connector.

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