JP2022027735A - Repair method for electronic element mounting board, repair material, cured product and wiring board - Google Patents

Abstract

To provide a repair method for an electronic element mounting board, with which reworking operations are facilitated and high connection reliability can be obtained.SOLUTION: In an electronic element mounting board, an electrode and an electronic element on a wiring board are mounted to allow current flow therebetween via a cured product of a conductive paste composition. A repair method for the electronic element mounting board includes: heating an electronic element mounting area where at least an electronic element not mounted normally is included and removing the electronic element not mounted normally from the wiring board; irradiating the area, where the electronic element has been removed, with laser beams and removing an entire or at least part of a cured product of the conductive paste composition from the wiring board; and remounting an electronic element in an area where the cured product has been removed.SELECTED DRAWING: None

Description

The present invention relates to a method for repairing an electronic element mounting substrate, a repair material used thereof, a cured product of the repair material, and a wiring board including the cured product thereof.

Electro-optical devices such as liquid crystal displays are used as display units for computers, mobile phones and other electronic devices. In particular, liquid crystal displays are lightweight, thin, and consume less power, so they are widely used as display units for various electronic devices. Has been done. In these liquid crystal display devices, those equipped with a so-called backlight on the back side of an electro-optic component such as a liquid crystal panel are often used.

In recent years, LED array substrates have come to be used as backlights used in electro-optical devices and the like. The LED array board is a board in which a plurality of LED chips are mounted in a matrix, and the individual LED chips and the wiring board are electrically connected by solder or the like. Recently, in order to reduce the size and efficiency of backlights, it has become common to use smaller LED chips in LED array boards, integrate individual LED chips, and mount them on wiring boards. .. Along with this, even in the mounting of LED chips, conductive pastes and conductive films called anisotropic conductive materials have begun to be used instead of the conventional electrical connection using solder. The anisotropic conductive material is a material in which conductive particles are dispersed in an insulating curable resin binder, and the electrode portions of electronic components (here, a wiring board and an LED chip) are thermally pressure-bonded to each other. Electronic components can be electrically connected to each other via conductive particles only in the pressurizing direction, and the electronic components can be fixed by curing the curable resin binder while maintaining insulation between adjacent electrodes. There is (for example, Patent Document 1 etc.).

The advantage of using an anisotropic conductive material instead of solder is that a large number of LED chips can be mounted on a wiring board at the same time and in a short time. On the other hand, the anisotropic conductive material has a problem that the reworkability is worse than that of the solder connection. That is, in the case of solder connection, the target component can be easily removed from the wiring board and remounted by heating the target component to be reworked, but in the connection using the anisotropic conductive material as described above, the electronic components are connected to each other. Since it is firmly adhered by the resin binder, it cannot be easily removed, and even if the electronic components can be removed, the cured resin binder remains on the wiring board, so use a special solvent or the like. It was necessary to remove the resin binder.

In order to deal with these problems, in Patent Document 2, a new anisotropic conductive film is attached while the cured anisotropic conductive material remains on the wiring board, and electronic components are used without using a repair agent. The technology that can be re-crimped is described.

Japanese Unexamined Patent Publication No. 8-003529 Japanese Unexamined Patent Publication No. 2010-272545

However, the method proposed in Patent Document 2 requires a design in which the elastic modulus of the cured product of the anisotropic conductive film at 150 ° C. is 10 MPa or less, so that the connection reliability (heat resistance) between electronic components is required. Was difficult to obtain. Further, since pressurization is required when remounting electronic components, damage to the wiring board is unavoidable when an FPC (flexible wiring board) or the like is used as the wiring board.

Furthermore, in recent years, the miniaturization of LED chips has progressed, and for example, LED array boards in which LED chips with external dimensions of several tens of microns are mounted on wiring boards at adjacent intervals of 1 mm or less have also been put into practical use. Therefore, it is becoming more and more difficult to remove the LED chip from the wiring board. Further, since the portion where the defective LED chip is removed is narrow, it is very difficult to remove the cured resin binder remaining on the wiring board side. It is conceivable to use a strong removing solvent, but in that case, there is a risk of damaging the surrounding electronic elements and the like mounted.

The present invention has been made based on such a problem, and an object of the present invention is to provide a method for repairing an electronic element mounting substrate which facilitates rework work and can obtain high connection reliability. .. Another object of the present invention is to provide a wiring board including a repair material, a cured product of the repair material, and a cured product of the repair material used in such a repair method.

To solve the above problems, the present inventors can easily perform the rework work by removing the resin component remaining at the time of repairing the conventional electronic element mounting substrate by laser irradiation before remounting the electronic element. At the same time, it was found that the connection reliability of the remounted electronic element can be improved. The present invention has been completed based on such findings. That is, the gist of the present invention is as follows.

[1] A method for repairing an electronic element mounting substrate in which an electrode on a wiring board and an electronic element are mounted so as to be energized via a cured product of a conductive paste composition.
The electronic element mounting region containing at least the improperly mounted electronic element is heated to remove the improperly mounted electronic element from the wiring board.
The region from which the electronic element has been removed is irradiated with laser light to remove all or at least a part of the cured product of the conductive paste composition from the wiring board.
The electronic element is remounted in the region where the cured product has been removed.
A method characterized by including.
[2] The method according to [1], wherein the repair material containing a curable resin is applied to the region from which the cured product has been removed or the electronic element to be remounted, and the electronic element is remounted.
[3] The conductive paste composition contains a curable resin and conductive particles, and the light absorption wavelength of at least one of the cured product of the curable resin and the conductive particles is 300 nm to 10600 nm [1]. ] Or the method according to [2].
[4] The method according to [3], wherein the electronic element mounting region is heated at a temperature higher than the glass transition point of the cured product and at a temperature equal to or higher than the melting point of the conductive particles.
[5] The conductive paste composition and the repair material contain flux.
The method according to any one of [2] to [4], wherein the amount of flux contained in the repair material is 2 to 10 times the amount of flux contained in the conductive paste composition on a mass basis.
[6] The method according to [5], wherein the repair material contains the flux in a proportion of 0.5 to 20% by mass with respect to the solid content of the repair material.
[7] An electronic element that is not normally mounted is removed from an electronic element mounting board that is mounted so that an electrode on a wiring board and an electronic element are energized via a cured product of the conductive paste composition. , A repair material used when remounting electronic elements.
Contains at least curable resin and flux,
A repair material comprising the flux at a ratio of 0.5 to 20% by mass with respect to the solid content of the repair material.
[8] The method according to [7], further comprising conductive particles.
[9] The cured product of the repair material according to [7] or [8].
[10] A wiring board comprising the cured product according to [8].

According to the present invention, the cured product of the conductive paste composition remaining on the wiring board is removed by irradiating the region where the electronic component is removed from the electronic element mounting substrate with a laser beam. Moreover, the rework work can be easily carried out, and the connection reliability of the remounted electronic element can be improved. This is especially effective when repairing a miniaturized LED chip.

Aspects for carrying out the invention

The method for repairing an electronic element mounting board of the present invention is (i) heating an electronic element mounting region containing at least an electronic element that is not normally mounted, and removing the improperly mounted electronic element from the wiring board. Steps, (ii) a step of irradiating the region from which the electronic element has been removed with laser light to remove all or at least a part of the cured product of the conductive paste composition from the wiring board, and (iii). The step of remounting the electronic element in the region from which the cured product has been removed is included.

The electronic element mounting substrate used in the repair method of the present invention refers to a wiring board in which an electrode on a wiring board and an electronic element are mounted so as to be energized via a cured product of a conductive paste composition. do. However, it does not positively exclude the electronic element mounting board on which the electrode on the wiring board and the electronic element are energized by an electric connection means such as solder, and the electronic element puts a resin on the wiring board. Needless to say, the repair method of the present invention can be applied to an electronic element mounting substrate that is fixed (bonded) via the same.

To mount an electronic element on a wiring board, usually, as described above, a conductive paste composition such as an anisotropic conductive adhesive is applied to the wiring board, and each electronic element is placed at an electrode position on the wiring board. By arranging and subsequently heating, the composition is solidified and the electronic element is adhered to the wiring board, and the electrode of the wiring board and the electronic element are electrically connected via the conductive particles in the composition. At the time of heating, if desired, pressurization may be performed from the electronic element side. Although the conductive paste composition itself is insulating, the conductive particles contained in the conductive paste composition are melted by heating and are sandwiched between the electrode on the wiring board side and the electrode on the electronic element side to be conductive. Path is formed. As a result, electrical connection between the members becomes possible. On the other hand, in the region not sandwiched between the electrodes even after heating, the conductive particles remain dispersed, so that the insulating property is maintained. This results in a so-called anisotropically conductive connection structure. Of course, the electronic element mounting substrate may be manufactured by a method other than the above, and is not limited to the one manufactured by the above method.

The electronic element mounting substrate applied to the repair method of the present invention is not particularly limited as long as it is an electronic element mounting substrate manufactured by using the conductive paste composition as described above, and the manufacturing method thereof is not particularly limited, for example. Even if it is applied on a wiring board, an electronic element is placed on the wiring board via a conductive paste composition, and then the electronic element is heated on the wiring board to mount the electronic element on the wiring board. good.

Further, examples of the electronic element mounting substrate to which the repair method of the present invention can be applied include a chip-on-board (COB) in which an electronic element such as a bare chip or an LED chip is directly mounted on a wiring board and connected. Hereinafter, the repair method of the electronic element mounting substrate of the present invention will be described in detail.

<Process for removing electronic elements that are not mounted normally>
First, among the electronic elements mounted on the wiring board, the electronic elements that are not normally mounted (hereinafter, also referred to as “defective points”) are identified. In the present invention, the defective part is not only the part that does not function normally due to the defect of the electronic element when the energization inspection is performed on the electronic element mounting board, but also the electrode of the wiring board that the electronic element itself functions normally. It also includes the places where the connection is poor and the places where the electronic elements and the electrodes of the wiring board are connected normally, but the positions of the electronic elements are not good, such as the positions are misaligned. Further, the wiring board may be not only a rigid printed wiring board but also a flexible printed wiring board.

The defective portion may be identified visually or by using a general-purpose inspection machine or the like. For example, when the electronic element mounting board is an LED array board, a lighting inspection may be performed to identify a defective part, and an LED chip having a non-lighting or a defect in emission color or brightness may be used. Identify.

Next, the electronic element mounting region including at least the defective portion identified as described above is heated to remove the electronic element that is not normally mounted from the wiring board. The electronic element mounting region here may be only the specified electronic element that is not normally mounted, or may be a peripheral region including the electronic element. For example, if only one electronic element is defective, it may be only in the place where the electronic element is mounted, or even in the peripheral region including the normally functioning electronic element around the electronic element. good.

The region to be heated may include the specified electronic element, and when there is only one defective part, only the defective part can be heated to remove the specified electronic element. When there are a plurality of defective parts in the electronic element mounting substrate, the individual defective parts may be heated, or the entire wiring board may be heated to remove the specified electronic element.

The heating temperature is not particularly limited as long as it can be removed by the electronic element mounted on the wiring substrate, but is preferably a temperature higher than the glass transition point of the cured product of the conductive paste composition. It is preferable that the temperature is equal to or higher than the melting point of the molten solidified product of the conductive particles (that is, the conductive particles contained in the conductive paste composition). Although it depends on the curable resin and the conductive particles contained in the conductive paste composition used, the heating is preferably performed at 100 to 240 ° C, more preferably 120 to 220 ° C, and particularly preferably. Is 140-200 ° C. The heating time is 1 to 60 seconds, preferably 1 to 30 seconds, and more preferably 1 to 15 seconds.

The heating may be performed from the side of the wiring board on which the electronic element is mounted or from the opposite surface, but from the viewpoint of minimizing the thermal damage to the electronic element, the wiring board may be heated. It is preferable to heat from the surface opposite to the side on which the electronic element is mounted. Further, the heating means is not particularly limited, and various methods can be used. For example, in the case of locally heating only a defective portion, a heating means such as a spot heater or a heat dryer may be applied. In addition, when the entire wiring board is heated, a planar heating means such as a hot plate can be applied.

By heating, the cured product of the conductive paste composition that fixes (bonds) the wiring board and the electronic element softens, and the molten solidified product of the conductive particles in the cured product remelts, resulting in unnecessary stress. The electronic element can be removed from the electronic element mounting board without applying stress. As a means for removing the electronic element, it may be performed manually using tweezers or the like, or a removing device provided with a dedicated gripping tool may be used.

<Curing product removal process>
When a specific electronic element is removed from the electronic element mounting substrate as described above, a cured product of the conductive paste composition in which the wiring board and the electronic element are adhered remains on the surface of the electronic element mounting substrate after removal. is doing. Such a residue may cause a connection failure or the mounting position of the electronic element may shift when a new electronic element is remounted. In the present invention, the cured product of the conductive paste composition is irradiated with laser light to convert the energy of the laser light irradiation into heat, and the heat removes the resin component constituting the remaining cured product. .. That is, the region from which the specific electronic component has been removed from the electronic element mounting substrate as described above is irradiated with laser light to remove the cured product of the conductive paste composition remaining on the wiring board. From the viewpoint of connection stability of the electronic element after remounting, it is preferable to remove all the cured products remaining on the wiring board, but it is not always necessary to remove all the cured products. It suffices if at least a part is removed. For example, the cured product contains a resin component and a component derived from conductive particles (a melt-solidified conductive particle). The resin component can be removed by laser irradiation, but most of the components derived from conductive particles are removed. Not done. In the present invention, from the viewpoint of efficiently removing the cured product remaining on the substrate, the cured product is a conductive paste containing a curable resin and conductive particles capable of absorbing at least a part of the wavelength band of laser light. It is preferably a cured product of the composition.

The laser light to be irradiated is not particularly limited as long as it is in a wavelength range (300 nm to 10600 nm) in which the conductive particles contained in the cured product of the conductive paste composition can absorb the irradiation light and convert it into heat. Laser light of the same wavelength or type can be used, and it may be a continuous wave laser or a pulse wave laser. Examples of continuous wave lasers include _YVO4 lasers, fiber lasers, excima lasers, green lasers, carbon dioxide gas lasers, ultraviolet lasers, YAG lasers, semiconductor lasers, glass lasers, ruby lasers, He-Ne lasers, nitrogen lasers, and chelate lasers. , Dye laser and the like can be used. Further, as the pulse wave laser, for example, a nanosec pulse laser, a millisec pulse laser, or the like can be used.

The output of the laser beam is not particularly limited as long as the resin component in the cured product can be removed, but if the output is high, excessive heat may be generated and the substrate may be damaged. Therefore, it is preferable to repeatedly irradiate the laser beam with an average output of about 0.2 to 1.0 W. The number of repetitions is not particularly limited, but is preferably about 5 to 50 times from the viewpoint of achieving both damage to the substrate and practicality. Further, the continuous wave laser may be used to repeatedly irradiate the laser beam, or a pulse wave laser may be used. The beam diameter of the laser beam is, for example, about 5 μm to 200 μm.

In the repair method of the present invention, among the cured products (cured products of the conductive paste composition) remaining on the wiring board when the mounted electronic elements are removed, the resin component is mainly decomposed by laser light irradiation. And be removed. According to laser light irradiation, it is possible to accurately remove all or at least a part of the cured product even in a narrow area, and it is possible to reduce the influence of heat on the surroundings, so that it is mounted. It is unlikely that other normal electronic devices will be adversely affected by heat. Therefore, it can be said that it is suitable for repairing an electronic element mounting board such as a chip-on-board (COB) in which an electronic element such as a bare chip or an LED chip is directly mounted and connected on the substrate. In particular, it can be suitably used when an electronic element having an outer dimension of 0.3 mm or less, more preferably 0.2 mm or less, is removed from the wiring board and remounted. The outer dimension of the electronic element means the length of the longest side among the three sides of length, width, and height. It is also suitable for repairing a substrate on which such a small electronic element is mounted at a high density. For example, it is particularly suitable for repairing an electronic element mounting substrate in which the distance between adjacent electronic elements is 5 mm or less, preferably 4 mm or less.

Here, a conductive paste composition suitably used for an electronic element mounting substrate to which the repair method of the present invention is applied will be described. The conductive paste composition generally contains a curable resin and conductive particles, but may contain other components as long as the anisotropic conductive adhesive function as described above is not impaired.

The curable resin contained in the conductive paste composition functions as a binder for the conductive fine particles and also has a function of being cured to fix the wiring board and the electronic element. The curable resin is preferably a curable resin that is cured by heat, and examples thereof include epoxy resin, phenol resin, melamine resin, unsaturated polyester resin, maleimide resin, polyurethane resin, silicone resin, cyanate resin, and acrylic resin. Among them, epoxy resin and acrylic resin can be preferably used, and epoxy resin is particularly preferable.

The epoxy resin can be used without limitation as long as it has two or more epoxy groups in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A. Novolak type epoxy resin, biphenyl type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, phosphorus Examples thereof include epoxy resin, anthracene type epoxy resin, norbornen type epoxy resin, adamantan type epoxy resin, fluorene type epoxy resin, aminophenol type epoxy resin, aminocresol type epoxy resin, alkylphenol type epoxy resin and the like. The above-mentioned epoxy resins can be used alone or in combination of two or more.

Even among the above-mentioned epoxy resins, it is preferable that the composition is liquid rather than solid from the viewpoint of forming a paste. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol E type epoxy resin are preferable. These commercially available products include ZX-1059 (a mixture of bisphenol A type and bisphenol F type epoxy resin) manufactured by Nittetsu Chemical & Materials Co., Ltd., jER-828 and jER-834 manufactured by Mitsubishi Chemical Co., Ltd. Examples thereof include jER-1001 (bisphenol A type epoxy resin), jER-807, jER-4004P (bisphenol F type epoxy resin), and R710 (bisphenol E type epoxy resin) manufactured by Air Water.

The acrylic resin is not particularly limited as long as it is a resin having a (meth) acrylic group, and examples thereof include trifunctional methacrylate monomers such as trimethylolpropane trimethacrylate and epoxy acrylate having a trimethylpropane skeleton. Among these, monofunctional (meth) acrylate, bifunctional (meth) acrylate, trifunctional or higher polyfunctional (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, bifunctional or higher polyester (meth). Acrylate can be preferably used.

Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and s-butyl. (Meta) acrylate, t-butyl (meth) acrylate, butoxyethyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octylheptyl (meth) ) Acrylate, Nonyl (meth) acrylate, Decyl (meth) acrylate, Undecyl (meth) acrylate, Lauryl (meth) acrylate, Tridecyl (meth) acrylate, Tetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, Hexadecyl (meth) acrylate , Stearyl (meth) acrylate, behenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) ) Acrylate (meth) acrylates such as acrylates, cyclopentyl (meth) acrylates, cyclohexyl (meth) acrylates, cyclopentyl (meth) acrylates, dicyclopentanyl (meth) acrylates, dicyclopentenyl (meth) acrylates, isobornyl (meth). ) Acrylate, 3-methyl-3-oxetanylmethyl (meth) acrylate, alicyclic (meth) acrylate such as 1-adamantyl (meth) acrylate, phenyl (meth) acrylate, nonylphenyl (meth) acrylate, p-cumylphenyl (Meta) acrylate, o-biphenyl (meth) acrylate, 1-naphthyl (meth) acrylate, 2-naphthyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- Hydroxy-3- (o-phenylphenoxy) propyl (meth) acrylate, 2-hydroxy-3- (1-naphthoxy) propyl (meth) acrylate, 2-hydroxy-3- (2-naphthoxy) propyl (meth) acrylate Aromatic (meth) acrylates, 2-tetrahydrofurfuryl (meth) acrylates, N- (meth) acryloyloxye Examples include heterocyclic (meth) acrylates such as chillhexahydrophthalimide, 2- (meth) acryloyloxyethyl-N-carbazole.

Examples of the bifunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol di (meth). Acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butane Didioldi (meth) acrylate, 2-methyl-1,3-propanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1, 5-Pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, 1,9-nonanediol di ( Fat group (meth) acrylates such as meta) acrylates, 1,10-decanediol di (meth) acrylates, glycerindi (meth) acrylates, tricyclodecanedimethanol (meth) acrylates, cyclohexanedimethanol (meth) acrylates, Alicyclic (meth) acrylates such as tricyclodecanedimethanol (meth) acrylates, hydrogenated bisphenol A di (meth) acrylates, hydrogenated bisphenol F di (meth) acrylates, bisphenol A di (meth) acrylates, bisphenol F Like di (meth) acrylates, bisphenol AF di (meth) acrylates, ethoxylated bisphenol A di (meth) acrylates, aromatic (meth) acrylates such as fluorene-type di (meth) acrylates, di (meth) acrylates of isocyanuric acid. Examples thereof include heterocyclic (meth) acrylates.

Examples of the trifunctional or higher-functional polyfunctional (meth) acrylate include trimethyl propanetri (meth) acrylate, pentaerythritol tri (meth) acrylate, ditrimethylol propanetetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, and di-erythritol tetra (meth) acrylate. Pentaerythritol Penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, aliphatic (meth) acrylate such as ethoxylated glycerin tri (meth) acrylate, heterocyclic (meth) acrylate such as isocyanuric acid tri (meth) acrylate. ) Acrylate can be mentioned.

The conductive paste composition may contain other curable resins. For example, a polyfunctional epoxy resin may be contained in addition to the above-mentioned epoxy resin. Examples of the polyfunctional epoxy resin include EP-3300E manufactured by ADEKA Co., Ltd., which is a hydroxybenzophenone type liquid epoxy resin, and jER-630 manufactured by Mitsubishi Chemical Co., Ltd., which is an aminophenol type liquid epoxy resin (paraaminophenol type liquid epoxy resin). , ELM-100 manufactured by Sumitomo Chemical Co., Ltd., jER-604 manufactured by Mitsubishi Chemical Co., Ltd., which is a glycidylamine type epoxy resin, Epototo YH-434 manufactured by Nittetsu Chemical & Materials Co., Ltd., manufactured by Sumitomo Chemical Industry Co., Ltd. Examples thereof include Sumi-epoxy ELM-120 and DEN-431 manufactured by Dow Chemical Co., Ltd., which is a phenol novolac type epoxy resin. These polyfunctional epoxy resins can be used alone or in combination of two or more.

The conductive paste composition may contain a curing agent for curing the above-mentioned curable resin. As the curing agent, a known curing agent generally used for curing a thermosetting resin can be used, and for example, amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, etc. can be used. , And polymers containing these functional groups, and a plurality of these may be used if necessary. Examples of amines include dicyandiamide and diaminodiphenylmethane. Examples of imidazoles include alkyl-substituted imidazoles and benzimidazoles. Further, the imidazole compound may be an imidazole latent curing agent such as an imidazole adduct. Examples of polyfunctional phenols include hydroquinone, resorcinol, bisphenol A and halogen compounds thereof, and novolak and resor resins which are condensates of aldehydes. Examples of the acid anhydride include phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, benzophenone tetracarboxylic acid and the like. Examples of the isocyanates include tolylene diisocyanate and isophorone diisocyanate, and those isocyanates masked with phenols or the like may be used. These curing agents may be used alone or in combination of two or more.

The curing rate of the resin can be controlled by adjusting the type and blending amount of the curing agent and curing accelerator, but from the viewpoint of idiosyncratic conductivity, the reaction temperature (curing temperature) of the resin is the conductivity described later. It is preferably higher than the melting point of the sex particles, and more preferably 5 ° C. or higher. Reaction temperature of the resin Since the reaction temperature (curing temperature) of the resin is higher than the melting point of the conductive particles, the conductive particles dispersed in the composition can be self-aggregated before the resin is cured.

Regarding the selection of the curable resin and the curing agent or curing accelerator, a combination may be used in which the cured resin is colored. As will be described later, it is preferable that the conductive particles have a function of absorbing laser light and converting it into heat energy, but even when the conductive particles do not absorb the laser light, the cured resin can be used. Anything that can absorb laser light and convert it into heat energy will do. That is, the cured resin may have a wavelength band capable of absorbing at least a part of the wavelength band of the laser light. The resin component absorbs the laser beam and is converted into heat energy, so that the removability of the resin component in the cured product is improved.

As the conductive particles, any material having conductivity can be used without particular limitation, but those capable of absorbing at least a part of the wavelength band of laser light can be preferably used, for example, gold. Examples include silver, nickel, copper, lead, and low melting point solder particles described below. The conductive particles may be composite particles in which non-conductive particles such as glass, ceramic, and plastic as nuclei are coated with a metal layer, and composite particles having the non-conductive particles and metal particles. When the conductive particles are the above-mentioned composite particles or heat-meltable metal particles, the conductive particles are melt-deformed by heating, so that the contact area with the electrode increases at the time of connection, and particularly high reliability can be obtained. As the conductive particles, silver-coated copper particles or metal particles having a shape in which a large number of fine metal particles are connected in a chain can also be used.

In the present invention, when the cured product of the conductive paste composition contains the conductive particles, the conductive particles in the cured product absorb the laser light by the laser light irradiation in the step of removing the cured product. Light energy is converted to heat and the cured product is heated locally. As a result, it is considered that the resin component mainly constituting the cured product is thermally decomposed and all or at least a part of the cured product is removed.

As the conductive particles, heat-meltable conductive particles are preferable, and it is particularly preferable to use conductive particles that are melted by heating at 170 ° C. or lower, and among them, low melting point solder particles are more preferable, and Sn-Pb. System and Sn—Bi system low melting point solder particles are more preferable. The low melting point solder particles mean solder particles having a melting point of 200 ° C. or lower, preferably 170 ° C. or lower, and more preferably 150 ° C. or lower. In particular, from the viewpoint of facilitating the removal of the electronic element in the above-mentioned step of removing the defective electronic element, the melting point of the conductive particles may be higher or lower than the glass transition temperature of the cured product of the above-mentioned curable resin. You may.

Further, as the low melting point solder particles, lead-free solder particles are preferable, and the lead-free solder particles are defined in JIS Z 3482: 2017 (solder-chemical composition and shape) and have a lead content of 0. . Means solder particles of 10% by mass or less.

As the lead-free solder particles, low melting point solder particles composed of one or more kinds of metals selected from tin, bismuth, indium, copper, silver and antimony are preferably used. In particular, an alloy of tin (Sn) and bismuth (Bi) is preferably used from the viewpoint of the balance between cost, handleability and bonding strength.

The content of Bi in such low melting point solder particles is appropriately selected in the range of 15 to 65% by mass, preferably 35 to 65% by mass, and more preferably 55 to 60% by mass.

By setting the Bi content to 15% by mass or more, the alloy starts melting at about 160 ° C. Further, when the Bi content ratio is increased, the melting start temperature is lowered, and the melting start temperature becomes 139 ° C. at 20% by mass or more, and the eutectic composition is obtained at 58% by mass. Therefore, by setting the Bi content ratio in the range of 15 to 65% by mass, the effect of lowering the melting point can be sufficiently obtained, and as a result, sufficient conduction connection can be obtained even at a low temperature.

The conductive particles are preferably spherical. Here, the spherical conductive particles mean those containing 90% or more of the spherical powder having a ratio of the major axis to the minor axis of 1 to 1.5 at a magnification at which the shape of the conductive particles can be confirmed. Further, the conductive particles preferably have an average particle diameter of 1 to 100 μm, more preferably 3 to 80 μm, and even more preferably 5 to 60 μm. In the present specification, the average particle size means the median size (D50) measured by using a laser diffraction type particle size distribution meter.

The specific surface area of the conductive particles is preferably 300 cm ² / g to 2000 cm ² / g, and more preferably 500 cm ² / g to 1500 cm ² / g. By using conductive particles having a specific surface area in the above range, the stability of the conductive connection between the electrodes of the wiring board and the electronic element is improved. The specific surface area of the conductive particles means a value measured by the BET method, and specifically, an inert gas (for example, nitrogen gas) having a known molecular size is applied to the surface of the measurement sample. It is adsorbed, and the specific surface area can be obtained from the adsorbed amount and the occupied area of the inert gas.

The blending amount of the conductive particles is preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and particularly 40 to 50% by mass with respect to the solid content in the conductive paste composition. It is preferably in the range. By setting the blending amount of the conductive particles to 20% by mass or more, it is possible to secure a sufficient conductive connection while ensuring the adhesion between the wiring board and the electronic element. Further, by setting the blending amount of the conductive particles to 70% by mass or less, it is possible to secure sufficient adhesion while ensuring conduction connectivity.

The conductive paste composition may contain other components in addition to the curable resin and the conductive fine particles. The conductive paste composition may contain a flux in order to enhance the stability of the conductive connection. As the flux, a known flux used in the conductive paste composition can be used, for example, zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, and the like. Examples thereof include phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, and pine fat. These fluxes can be used alone or in combination of two or more.

Among the above-mentioned fluxes, organic acids can be preferably used. Preferred organic acids include monocarboxylic acids as well as polyvalent carboxylic acids such as dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids. Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tubercrostearic acid. , Arakidic acid, behenic acid, lignoseric acid, glycolic acid and the like. Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartrate acid, diglycolic acid and the like. Examples of the tricarboxylic acid include benzene-1,2,5-tricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,3-propanetricarboxylic acid and the like. Examples of the tetracarboxylic acid include benzophenone tetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid and the like. Among these carboxylic acids, dicarboxylic acid is preferable, glutaric acid and adipic acid are more preferable, and adipic acid is particularly preferable.

The content of the flux in the conductive paste composition is preferably 0.5 to 15% by mass, more preferably 0.5 to 10% by mass, based on the solid content in the composition. By using a conductive paste composition having a flux content within the above range, the conductive connectivity can be further improved.

In addition, a basic organic compound may be contained in order to adjust the activity of the flux. Examples of the basic organic compound include aniline hydrochloride, hydrazine hydrochloride and the like.

Further, the conductive paste composition may contain a filler, if necessary, in order to increase the physical strength of the cured product. As the filler, known inorganic or organic fillers can be used, but barium sulfate, spherical silica, hydrotalcite and talcite are particularly preferably used. Further, in order to obtain flame retardancy, a metal oxide, a metal hydroxide such as aluminum hydroxide, or the like can be used as an extender pigment filler. Among these fillers, those having a wavelength band capable of absorbing at least a part of the wavelength band of the laser beam can be preferably used, and examples thereof include titanium oxide. By including such a filler, the cured product easily absorbs the laser beam and is converted into heat energy, and the removability of the resin component in the cured product is improved.

When the filler is blended, the filler may be surface-treated in order to enhance the dispersibility in the conductive paste composition. Aggregation can be suppressed by using a filler that has been surface-treated. The surface treatment method is not particularly limited, and a known and commonly used method may be used. However, the surface of the inorganic filler may be treated with a surface treatment agent having a curable reactive group, for example, a coupling agent having a curable reactive group as an organic group. It is preferable to treat it.

As the coupling agent, a silane-based, titanate-based, aluminate-based, zircoaluminate-based, or other coupling agent can be used. Of these, a silane-based coupling agent is preferable. Examples of such silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N- (2-aminomethyl) -3-aminopropylmethyldimethoxysilane, and N- (2-aminoethyl) -3-amino. Propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxy) Cyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, etc. can be mentioned, and these can be used alone or in combination of two or more.

An organic solvent may be added to the conductive paste composition from the viewpoint of ease of preparation and coatability. Examples of the organic solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethyl benzene; cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol and propylene glycol monomethyl ether. , Dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, tripropylene glycol monomethyl ether and other glycol ethers; ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbi Esters such as tall acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, and solvent naphtha are known. Conventional organic solvents can be used. These organic solvents may be used alone or in combination of two or more.

<Remounting process of electronic elements>
As described above, the electronic device is remounted in the region where all or at least a part of the cured product has been removed. To remount the electronic element, a repair material is applied to the area on the wiring board where the electronic element is arranged or the electronic element to be remounted, and after the electronic element is arranged, the repair material is cured by heating. The electronic element can be remounted by solidifying (adhering) the wiring board and the electronic element. At the time of heating, if desired, pressurization may be performed from the electronic element side. The repair material used when remounting the electronic element on the wiring board will be described below.

The repair material used in the repair method of the present invention needs to have a function of adhering the wiring board from which the cured product has been removed and the electronic element to be remounted. Therefore, the repair material contains a curable resin. As the curable resin, the same curable resin as that used in the above-mentioned conductive paste composition can be used. In the repair method of the present invention, as described above, when the cured product remaining on the wiring substrate is removed by irradiation with laser light, the resin component constituting the cured product is thermally decomposed and removed from the wiring substrate. The molten solidified of conductive particles contained in the cured product is heated by laser light irradiation and remelted, but normally does not decompose or evaporate and is attached to the electrodes on the wiring board. It remains. Therefore, by heating to a temperature at which the remaining conductive particles are remelted, the electrodes of the wiring board and the electronic elements can be conductively connected. Further, since the curable resin contained in the repair material is cured by heating to become a cured product, the electronic element can be fixed (adhered) to the wiring board.

The repair material contains a flux in addition to the curable resin. As the flux, the same flux as that used in the above-mentioned conductive paste composition can be used. In the present invention, as described above, when the resin component in the cured product remaining on the wiring substrate is removed by irradiation with laser light, the molten solidified of the conductive particles in the cured product is the light energy of the laser light. Oxidation proceeds as it is converted to heat. In particular, an oxide film may be formed on the surface of the molten solidified product that is in contact with air. Therefore, when the electronic element is remounted, a defect may occur in the conduction connection between the electrode of the wiring board and the electronic element due to the influence of the oxide film. In the present invention, since the repair material contains flux, the influence of the oxide film can be suppressed and the conduction connectivity can be improved.

The content of the flux contained in the repair material is preferably 2 to 10 times, based on the mass, 4 to 6 times the amount of the flux contained in the conductive paste composition from the viewpoint of conduction connectivity. It is more preferable to have. Further, from the viewpoint of conduction connectivity, the flux content is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, based on the solid content of the repair material.

Even if the repair material does not contain conductive particles, the conductive connection between the electrodes of the wiring board and the electronic element to be remounted is possible as described above, but even if the repair material contains conductive particles, it is possible. good. As the conductive particles, the same conductive particles as those used in the above-mentioned conductive paste composition can be used. When the repair material contains conductive particles, the blending amount thereof is preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and 35 to 35 to 70% by mass with respect to the solid content in the repair material. It is more preferably 55% by mass.

Further, the repair material may contain the same components as the conductive paste composition (for example, filler, organic solvent, etc.), and the blending amount thereof can be about the same as that of the conductive paste composition. ..

The method of applying the repair material to the region where the electronic element is to be remounted (that is, the region where the cured product is removed by laser light irradiation) or the method of applying the repair material to the electronic element to be remounted is particularly limited. However, from the viewpoint of being able to be applied locally, a method of applying with a scraper via a screen mesh or a metal mask and a method of applying with a dispenser can be mentioned. Among these coating methods, the method of coating using a dispenser is preferable because the repair material can be easily and easily applied to a desired region. In an electronic element mounting board such as a chip-on-board (COB) that mounts and connects electronic elements such as bare chips and LED chips directly on the substrate, the repair material is applied with an appropriate coating amount even in a narrow area. can do. When applying the repair material using a dispenser, the syringe filled with the repair material can be attached to the dispenser, and the repair material can be applied to a desired region while adjusting the discharge amount. The repair material may be applied to both the region where the electronic device is to be remounted and the electronic device to be remounted.

After applying the repair material to the region where the electronic element is to be remounted or the electronic element, the electronic element is placed and heated in the remounting area to which the repair material is applied. Along with the curing of the repair material by heating, the molten solidified of the conductive particles remaining on the substrate electrode is remelted, the electrode of the wiring board and the electronic element are electrically connected, and the electronic element is fixed to the electronic element mounting substrate ( By being glued), the repair is completed. At the time of heating, if desired, pressurization may be performed from the electronic element side.

The temperature at the time of heating is not particularly limited as long as the repair material is cured and the molten solidified of the conductive particles remaining on the electrodes of the wiring board is remelted, but is not particularly limited, but is 100 to 240 ° C., preferably 120. It is about 200 ° C., more preferably 145 to 200 ° C. As long as the conduction connectivity is not impaired, the electronic element may be crimped by applying pressure as desired with heating. In the case of heat crimping, crimping is performed at 0.5 to 5.0 MPa, preferably 0.8 to 3.0 MPa, more preferably 1.0 to 2.0 MPa, and the heating time is 1 to 60 seconds, preferably 1 It is ~ 30 seconds, more preferably 1 ~ 15 seconds. Under such heating or crimping conditions, it is possible to secure a conduction connection without damaging the electronic element to be remounted and the surrounding electronic elements mounted by heating or crimping.

According to the present invention, a cured product of the above-mentioned repair material is also provided. The production conditions such as the temperature at the time of heating in the cured product of the repair material are as described above, for example.

Further, according to the present invention, a wiring board provided with the cured product is also provided. Examples of the type of wiring board provided with the cured product of the repair material include a printed wiring board, a glass substrate, a substrate having a wiring layer on a ceramic substrate, and the like. The wiring board may be single-sided, double-sided, or multi-layered.

According to the present invention, the following embodiments are included.
[1] Electrodes and electronic elements on a wiring board are energized via a cured product of a conductive paste composition containing a curable resin and conductive particles capable of absorbing at least a part of the wavelength band of laser light. It is a repair method of the electronic element mounting board that is mounted in this way.
Identify the defective part where the electronic element is not mounted normally,
The electronic element mounting region including at least the defective portion is heated to remove the specified electronic element from the wiring board.
The region from which the electronic element has been removed is irradiated with laser light to remove all or at least a part of the cured product of the conductive paste composition.
A repair material containing a curable resin is applied to the region where the cured product has been removed or the electronic element to be remounted, and the electronic element is placed on the electrode of the wiring substrate from which the electronic element has been removed. The repair material is cured and the electronic element is remounted.
The method, including that.
[2] The method according to [1], wherein the conductive paste composition contains the conductive particles at a ratio of 20 to 70% by mass with respect to the solid content in the conductive paste composition.
[3] The method according to [1] or [2], wherein the conductive particles have a light absorption wavelength of 300 nm to 10600 nm.
[4] The method according to any one of [1] to [3], wherein the electronic element mounting region is heated at a temperature higher than the glass transition point of the cured product and at a temperature equal to or higher than the melting point of the conductive particles. Method.
[5] The method according to any one of [1] to [4], wherein the specific surface area of the conductive particles is 300 cm ² / g to 2000 cm ² / g.
[6] The conductive paste composition and the repair material contain flux.
The method according to any one of [1] to [5], wherein the amount of flux contained in the repair material is 2 to 10 times the amount of flux contained in the conductive paste composition on a mass basis.
[7] The method according to any one of [1] to [6], wherein the repair material contains the flux at a ratio of 1 to 10% by mass with respect to the solid content of the repair material.
[8] The method according to any one of [1] to [7], wherein the flux contains a carboxylic acid compound.
[9] The method according to any one of [1] to [8], wherein the curable resin is an epoxy resin.
[10] The method according to any one of [1] to [9], wherein the electronic element has an outer dimension of 1 mm or less.
[11] The method according to any one of [1] to [10], wherein the distance between adjacent electronic elements on the electronic element mounting substrate is 5 mm or less.
[12] An electronic element that is not normally mounted is removed from an electronic element mounting board that is mounted so that an electrode on a wiring board and an electronic element are energized via a cured product of the conductive paste composition. , A repair material used when remounting electronic elements.
Contains at least curable resin and flux,
A repair material containing the flux at a ratio of 1 to 20% by mass with respect to the solid content of the repair material.
[13] The repair material according to [12], which further contains conductive particles.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples. In the following, "part" and "%" are all based on mass unless otherwise specified.

[Example 1]
<Preparation of electronic element mounting board>
First, each component shown below was blended in a predetermined ratio and kneaded with a three-roll mill to prepare an anisotropic conductive paste composition.
-Epoxy resin 55 parts by mass (jER-828, liquid at room temperature, manufactured by Mitsubishi Chemical Corporation)
・ Hardener (DICY, dicyandiamide) 3 parts by mass ・ Flux (azipic acid) 1 part by mass ・ Low melting point solder particles 41 parts by mass (42Sn-58Bi spherical particles, melting point 139 ° C., specific surface area 541 cm ² / g (measured by BET method) Value), manufactured by Senju Metal Industry Co., Ltd.)

Next, the obtained anisotropic conductive paste composition was applied to a rigid substrate (base material: FR-4, electrode width: 120 μm, electrode length: 200 um, pitch width: 0.6 mm, number of electrodes 150, flash Au treatment). The top was coated with a scraper via a metal mask (mask thickness: 100 μm, opening: 200 μm × 100 μm) so as to have a thickness of 80 μm.
Subsequently, the electrodes of the individual LED chips (125 μm × 75 μm) are arranged so as to overlap each other at each electrode position of the rigid substrate to which the anisotropic conductive paste composition is applied, and the temperature is 180 ° C. for 10 minutes from the LED chip side. Was heated to prepare a substrate on which 150 LED chips were mounted.

<Repair of electronic element mounting board>
First, the LED mounting board obtained as described above was subjected to a continuity lighting inspection using a signal generator (DC signal source 7011 manufactured by Hioki Electric Co., Ltd.), and it was confirmed that all 150 LEDs were lit. did. From these, 10 LEDs were arbitrarily selected, and the 10 LEDs were virtually identified as defective parts. When selecting 10 LEDs, the adjacent LEDs were not selected.
Next, from the back side of the board on which the LED identified as the defective part is mounted, the LED identified as the defective part is heated at 170 ° C. for 1 minute using a hot plate whose heating surface is partially masked with a heat insulating material, and the LED identified as the defective part is used as the substrate. After removal from the substrate, the substrate was cooled to room temperature. It was confirmed by visually observing each part where the LED was removed, and that the cured product of the anisotropic conductive paste composition remained on the electrode on the surface of the substrate in all 10 parts.
Subsequently, a fiber laser (wavelength: 1064 nm, beam diameter: 40 μm) was used to irradiate the portion where the LED was removed with a laser beam at an output of 0.4 W for 1 second. This operation was repeated 15 times. When the spots irradiated with the laser beam were visually observed, it was confirmed that solder remained on the electrode surface of the substrate but no resin solids remained in all 10 spots.

Using a dispenser device, apply 300 mg of the anisotropic conductive paste composition to the place where the LED was removed (area of one place: about 120 μm × 200 μm), and use the same LED as the LED used for the LED mounting substrate as a repair material. Was placed at the place where the above was applied, and the positions of the electrodes on the substrate and the electrodes of the LED were adjusted so as to overlap each other.
Next, the LED was remounted by heating at 180 ° C. for 10 minutes from the LED chip side.

<Continuity test evaluation>
When a continuity lighting inspection was performed on a board on which 10 LEDs were remounted using a signal generator (DC signal source 7011 manufactured by Hioki Electric Co., Ltd.) in the same manner as above, 4 of the remounted LEDs were found. Although it turned on, 6 did not turn on.
Further, after conducting a TH test (Thermal Humidity Test) at a temperature of 85 ° C. and a humidity of 85% for 1000 hours on the remounted substrate, a continuity lighting inspection was performed in the same manner as described above. Four were lit, but six were not.

[Example 2]
<Preparation of repair material 1>
Repair materials 1 to 4 were obtained by blending each of the components shown below in a predetermined ratio and kneading with a stirrer.
Repair material 1
-Epoxy resin 54 parts by mass (jER-828, liquid at room temperature, manufactured by Mitsubishi Chemical Corporation)
・ Hardener (DICY, dicyandiamide) 3 parts by mass ・ Flux (adipic acid) 3 parts by mass ・ Low melting point solder particles 40 parts by mass (42Sn-58Bi spherical particles, melting point 139 ° C., specific surface area 541 cm ² / g, Senju Metal Industry Co., Ltd. Made by the company)

The LED was remounted in the same manner as in Example 1 except that the repair material 1 was used instead of the anisotropic conductive paste composition used for the LED remounting, and the continuity test was evaluated. As a result, 6 of the remounted LEDs turned on, but 4 did not. In the continuity lighting inspection after the TH test, 6 of the remounted LEDs were lit, but 4 were not.

[Example 3]
<Preparation of repair material 2>
-Epoxy resin 52 parts by mass (jER-828, liquid at room temperature, manufactured by Mitsubishi Chemical Corporation)
・ Hardener (DICY, dicyandiamide) 3 parts by mass ・ Flux (adipic acid) 6 parts by mass ・ Low melting point solder particles 39 parts by mass (42Sn-58Bi spherical particles, melting point 139 ° C., specific surface area 541 cm ² / g, Senju Metal Industry Co., Ltd. Made by the company)

The LED was remounted in the same manner as in Example 1 except that the repair material 2 was used instead of the anisotropic conductive paste composition used for the LED remounting, and the continuity test was evaluated. As a result, it was confirmed that all 10 of the remounted LEDs were lit. In the continuity lighting inspection after the TH test, it was confirmed that all 10 of the remounted LEDs were lit.

[Example 4]
<Preparation of repair material 3>
-Epoxy resin 49 parts by mass (jER-828, liquid at room temperature, manufactured by Mitsubishi Chemical Corporation)
・ Hardener (DICY, dicyandiamide) 3 parts by mass ・ Flux (adipic acid) 9 parts by mass ・ Low melting point solder particles 39 parts by mass (42Sn-58Bi spherical particles, melting point 139 ° C., specific surface area 541 cm ² / g, Senju Metal Industry Co., Ltd. Made by the company)

The LED was remounted in the same manner as in Example 1 except that the repair material 1 was used instead of the anisotropic conductive paste composition used for the LED remounting, and the continuity test was evaluated. As a result, it was confirmed that all 10 of the remounted LEDs were lit. In the continuity lighting inspection after the TH test, nine of the remounted LEDs were lit, but one was not.

[Example 5]
<Preparation of repair material 4>
-Epoxy resin 46 parts by mass (jER-828, liquid at room temperature, manufactured by Mitsubishi Chemical Corporation)
・ Hardener (DICY, dicyandiamide) 3 parts by mass ・ Flux (adipic acid) 12 parts by mass ・ Low melting point solder particles 39 parts by mass (42Sn-58Bi spherical particles, melting point 139 ° C., specific surface area 541 cm ² / g, Senju Metal Industry Co., Ltd. Made by the company)

The LED was remounted in the same manner as in Example 1 except that the repair material 1 was used instead of the anisotropic conductive paste composition used for the LED remounting, and the continuity test was evaluated. As a result, it was confirmed that all 10 of the remounted LEDs were lit. In the continuity lighting inspection after the TH test, 6 of the remounted LEDs were lit, but 4 were not.

[Comparative Example 1]
In the above-mentioned repair process of the electronic element mounting substrate, 10 LEDs were remounted on the substrate in the same manner as in Example 1 except that the laser beam irradiation was not performed.
Next, when the continuity lighting inspection was performed in the same manner as in Example 1, all 10 of the remounted LEDs did not light. Moreover, in the continuity lighting inspection after the TH test, all 10 of the remounted LEDs did not light.

[Comparative Example 2]
In the above-mentioned repair step of the electronic device mounting substrate, an organic solvent (methyl ethyl ketone) was used instead of the laser light irradiation to remove the deposits remaining on the electrodes of the substrate at the place where the LED chip was removed. Ten LEDs were remounted on the substrate in the same manner as in 1.
Next, when the continuity lighting inspection was performed in the same manner as in Example 1, all 10 of the remounted LEDs did not light. Moreover, in the continuity lighting inspection after the TH test, all 10 of the remounted LEDs did not light.

Claims (10)

It is a repair method of an electronic element mounting substrate in which an electrode on a wiring board and an electronic element are mounted so as to be energized through a cured product of a conductive paste composition.
The electronic element mounting region containing at least the improperly mounted electronic element is heated to remove the improperly mounted electronic element from the wiring board.
The region from which the electronic element has been removed is irradiated with laser light to remove all or at least a part of the cured product of the conductive paste composition from the wiring board.
The electronic element is remounted in the region where the cured product has been removed.
A method characterized by including. The method according to claim 1, wherein a repair material containing a curable resin is applied to the region from which the cured product has been removed or the electronic element to be remounted, and the electronic element is remounted. Claim 1 or 2 in which the conductive paste composition contains a curable resin and conductive particles, and the light absorption wavelength of at least one of the cured product of the curable resin and the conductive particles is 300 nm to 10600 nm. The method described in. The method according to claim 3, wherein the electronic element mounting region is heated at a temperature higher than the glass transition point of the cured product and at a temperature equal to or higher than the melting point of the conductive particles. The conductive paste composition and the repair material contain flux.
The method according to any one of claims 2 to 4, wherein the amount of flux contained in the repair material is 2 to 10 times the amount of flux contained in the conductive paste composition on a mass basis. The method according to claim 5, wherein the repair material contains the flux in a proportion of 0.5 to 20% by mass with respect to the solid content of the repair material. The electronic element that is not normally mounted is removed from the electronic element mounting board that is mounted so that the electrode on the wiring board and the electronic element are energized through the cured product of the conductive paste composition, and the electronic element is used. It is a repair material used when remounting
Contains at least curable resin and flux,
A repair material comprising the flux at a ratio of 0.5 to 20% by mass with respect to the solid content of the repair material. The repair material according to claim 7, further comprising conductive particles. The cured product of the repair material according to claim 7 or 8. A wiring board comprising the cured product according to claim 9.