KR100888984B1 - Conductive ball with nano metal particles bonded to polymer bead and preparation method thereof - Google Patents

Abstract

The present invention induces a strong bonding force through the chemical bonding of the metal layer and the polymer to prevent cracking between the metal and the polymer interface and separation of the metal layer, and to prevent the lowering of the conductivity due to the crack of the metal layer conductive ball and improved surface conductivity thereof It provides a manufacturing method. Method for producing a conductive ball according to the present invention, the first step of ionizing the polymer bead surface; Adsorbing ions to the modified polymer beads; A third step of reducing the adsorbed ions; And a fourth step of forming a metal layer by ion bonding on the reduced ion layer. In the conductive ball according to the present invention, the metal layer formed on the surface does not have the form of a continuous film but has a lamination form of nanoparticles, does not exhibit a layer separation phenomenon of the metal layer, and exhibits stable resistance characteristics.

Conductive Ball, Polymer Bead, Palladium, Nickel Layer, Gold Layer, Ion Bond

Description

CONDUCTIVE BALL WITH NANO METAL PARTICLES BONDED TO POLYMER BEAD AND PREPARATION METHOD THEREOF

This invention relates to the manufacturing method of the electroconductive ball which is a component of the anisotropic conductive film mainly used as an electronic packaging process connection material.

In general, electronic packaging technology is a very wide variety of system fabrication techniques including all stages from semiconductor devices to final products, and is a very important technique for determining the performance, size, price, reliability, etc. of final electronic products.

In recent years, in electronic packaging, the necessity of connecting a large number of electrodes with a narrow gap is increasing at the same time as the microgap of the circuit and the increase in the connection density increase. Accordingly, in the packaging of liquid crystal displays (LCDs), conductive adhesives are used for the mechanical and electrical connection of a flexible printed circuit (FPC) and a glass display, and in particular, anisotropic conductive films (anisotropic) conductive film) is mainly used.

The anisotropic conductive film is composed of conductive particles and an insulating adhesive. As the conductive particles that play an electrically conductive role, carbon fibers were initially used, and then solder balls were used, followed by nickel balls or silver powder. It is used until.

The reason why silver is used as the conductive particles of the anisotropic conductive film is that it is easy to use as conductive particles because of its low price, high electrical conductivity and good chemical stability. However, silver has a problem of electrical ion transfer. In addition, nickel has a low price and relatively good electrical conductivity, but when exposed to high temperature and high humidity, there is a problem such as corrosion or oxidation on the surface.

In order to solve this problem, the surface is coated with gold to improve the properties of the conductive particles. In particular, due to the inertness of the catalyst layer, palladium, which cannot be directly adsorbed onto the polymer, a conventional method is used to form a conductive layer in the order of palladium, nickel, and gold after physically adsorbing the polymer using tin chloride (SnCl ₂ ). However, in the case of using the above-described tin chloride, due to the physical properties of the polymer and the conductive layer, the adhesion is weak, causing a lot of phenomenon that the metal layer is separated from the pressure or external impact, and partial breakage and uniformity of the metal layer when the pressure is applied. This problem is generated to adversely affect the electrical resistance characteristics.

On the other hand, in the conductive ball, the plastic beads plated in the order of Pd, Ni, and Au are dispersed and disposed in the main body part or the resin part, and serve to perform electrical connection. In particular, the most important characteristics considered for conductive balls are connection resistance, reliability, and processability. Through these studies, these characteristics have been able to achieve many improvements. However, due to the difference in modulus between the polymer bead and the metal layer during the process of bonding the two different parts to each other to form a conductive part in contact with each other by heating and pressing, cracks between the polymer bead and the metal layer are generated, resulting in poor conductivity. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, to induce a strong bonding force through the chemical bonding of the metal layer and the polymer to prevent cracking and separation of the metal layer between the metal and polymer interface, and to form a coated metal surface The present invention provides a method for producing a conductive ball and a conductive ball having improved surface conductivity by preventing the lowering of conductivity due to cracking of a metal layer by effectively dispersing the pressure applied by controlling.

In order to achieve the above object, the present invention provides a conductive ball strongly bonded to the polymer bead and the metal layer through a chemical bond and a manufacturing method thereof. In particular, the present invention provides a conductive ball having a structure comprising a polymer bead and a metal layer formed by ion bonding on the polymer bead surface, ionizing the polymer bead surface, adsorbing ions to the modified polymer bead, and It provides a method for producing a conductive ball to form a metal layer by ion bonding on the reduced ion layer after reduction.

Hereinafter, the configuration of the present invention will be described in more detail.

The present invention comprises a first step of ionizing and modifying the polymer bead surface; Adsorbing ions to the modified polymer beads; A third step of reducing the adsorbed ions; And it provides a method for producing a conductive ball comprising a fourth step of forming a metal layer by ion bonding on the reduced ion layer.

The ionization modification can be carried out by bonding an ion group-containing compound including a sulfone group or the like to the polymer surface, and a compound having a functional group such as a sulfone group, a carboxyl group, an amine group, a hydroxyl group, a siol group, or a phosphate group is bonded to the polymer surface. This allows modification to cations or anions.

The metal layer for bonding by ionic bonding may use metal compounds, metal complexes which can be dissociated into cations or anions depending on the ionic state of the modified polymer surface, in particular nickel, gold, silver, copper, palladium, iron , Zinc, tin, chromium, magnesium, platinum, indium, and alloys thereof. These metal layers can be formed as one or more than two layers as the metal nanoparticle layer.

The present invention also provides a conductive ball having a structure comprising a polymer bead and a metal layer formed by ion bonding on the polymer bead surface. At this time, the metal has a form in which metal nanoparticles are stacked, and have a raspberry morphology by forming a selective surface of the nanoparticles. The raspberry morphology is a structure in which particles of nanoparticle units are stacked on a surface, and nanostructured spherical particles have a structure in which irregularities are formed on the surface. By such a raspberry-type morphology, the conductive ball according to the present invention forms a rough surface even though it is a metal layer rather than the smooth surface of the conventional conductive ball.

The present invention particularly provides a conductive ball having a structure comprising a polymer bead, a nickel layer formed by ion bonding on the surface of the polymer bead, and a gold layer formed on the nickel layer, wherein the nickel layer and the gold layer are in the form of a nanoparticle stack, It has a raspberry morphology by selective surface formation of nanoparticles.

The present invention also includes a first step of modifying the polymer bead surface by sulfonation directly with a sulfone group; Adsorbing palladium ions to the modified polymer beads; A third step of reducing palladium ions adsorbed to the polymer beads; Forming a nickel layer on the surface of the polymer beads coated with palladium; And a fifth step of forming a gold layer on the surface of the polymer bead having the nickel layer formed thereon.

The present invention also provides conductive balls having a structure comprising a polymer bead, a palladium ion layer ionically bonded to the polymer bead surface, a nickel layer formed on the palladium ion layer, and a gold layer formed on the nickel layer, wherein the nickel layer and / or Alternatively, the gold layer is preferably laminated in a nanoparticle structure.

According to the conductive ball manufacturing method of the present invention as described above, a strong bonding force is induced through the chemical bonding of the metal layer and the polymer beads. This prevents cracking of metal and polymer system surfaces and separation of metal layers. In addition, by controlling the coated metal surface in a morphological manner, by effectively dispersing the applied pressure, the conductivity of the metal layer is prevented from being degraded. This provides a conductive ball with improved surface conductivity.

Hereinafter, each step of the manufacturing method according to the present invention through the embodiments of the present invention will be described in more detail.

Step 1- Sulfone Modified Polymer beads  Produce

Polymer production methods include dispersion polymerization, emulsion polymerization and suspension polymerization. In the case of suspension polymerization, polymer beads of uniform size cannot be prepared, and in the case of emulsion polymerization, balls of very uniform size can be made, but in the manufacture of several micro-sized balls, they can be prepared through various stepwise methods.

The polymer in the form of beads in which the side of the sulfone group is modified with the sulfone group is obtained through a process of directly sulfonating. That is, a method of forming a catalyst layer directly on the surface of the polymer bead is used without using a conventional method of using tin chloride or surface roughness to form a catalyst layer on the surface of the polymer bead.

Surface modified polymer beads are obtained by reacting the polymer beads in a solvent for 1 to 24 hours and then centrifuging. At this time, the solvents that can be used include chlorosulfonic acid, sulfonic acid, acetic sulfide and the like. Bead polymers usable in the present invention include all polymers used in the art. The size of the beads can also be modified to all available sizes, without being particularly limited.

Stage 2-Surface Modified Polymer Beads  Adsorption of Palladium Ions on the Phase

The polymer beads obtained by modifying the surface obtained in the first step with a sulfone group are mixed with a palladium solution to induce an ionic bond between the sulfone group and the cationic palladium formed on the surface. At this time, it is preferable to impregnate for an appropriate time so that ions can be sufficiently adsorbed on the modified surface, this time can be appropriately selected according to the concentration and temperature of the palladium solution used.

As the palladium solution, palladium (II) acetate, palladium (II) acetylacetonate, palladium (II) bromide, palladium (II) Palladium chloride, palladium (II) cyanide, palladium (II) hexafluoroacetylacetonate, palladium (II) palladium (II) iodide, palladium (II) nitrate hydrate, palladium (II) oxide, palladium (II) oxide hydrate, palladium (II) ) Potassium thiosulfate monohydrate, palladium (II) propionate, palladium (II) sodium chloride, palladium (II) ) Sulfate (palladium (II) sulphate), palladium (II) Trifluoroacetic acid (palladium (II) trifluoro acetate), potassium tetrabromopalladate (II), potassium tetrachloropalladate (II), sodium tetrabromo Palladate (II), potassium hexachloropalladate (IV), sodium tetrachloro palladate (II) and the like can be used. .

Palladium cations that are not adsorbed sulfone groups are removed by washing. Washing is preferably separated by centrifugation and washed several times with distilled water.

Step 3-Reduction of Adsorbed Palladium Ions

Reduction can be performed using various reducing agents. For example, sodium borohydride, hydrazine, sodium sulphate, sulfite, sodium sulfide, iron ions, lithium aluminum hydride Lithium hydride, diisobutyl aluminum hydride, oxalic acid, Lindler catalyst, and the like, in particular sodium borohydride, Sodium sulfate, hydrazine, etc. can be used preferably. The palladium is reduced by placing a polymer having palladium ions adsorbed into a reducing agent solution.

Step 4- Nickel layer  formation

Palladium-coated polymer beads are impregnated into the nickel solution to form a nickel layer. Since this reaction does not require a reducing agent, it automatically reduces to form a nickel layer. The nickel solution used herein may be used by purchasing a commercially available product or by preparing a nickel solution having various compositions.

As a representative example, nickel (II) acetate tetrahydrate, nickel (II) acetylacetonate, nickel (II) bis (2,2,6,6- Tetramethyl-3,5-heptanedionate) (nickel (II) bis (2,2,6,6-tetramethyl-3,5-heptanedionate)), nickel (II) bromide, nickel (II) bromide hydrate (nickel (II) bromide hydrate), nickel (II) bromide ethylene glycol dimethyl ether complex (nickel (II) bromide ethylene glycol dimethyl ether complex), nickel (II) carbonate hydroxide tetrahydrate (II) carbonate hydroxide tetrahydrate, nickel (II) chloride, nickel (II) chloride hexahydrate, nickel (II) chloride hydrate ), Nickel (II) cyclohexane butylate, nickel (II) 2-ethylhex Nickel (II) 2-ethylhexanoate, Nickel (II) fluoride, Nickel (II) fluoride tetrahydrate, Nickel (II) hexafluoro Acetylacetonate hydrate (nickel (II) hexafluoroacetylacetonate hydrate), nickel (II) hydroxide (nickel (II) hydroxide), nickel (II) iodide (nickel (II) iodide), nickel (II) molybdate ( nickel (II) molybdate), nickel (II) nitrate hexahydrate, nickel (II) 5,9,14,18,23,27,32,36-octabutoxy-2, 3-naphthalocyanine (nickel (II) 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine), nickel (II) octanoate hydrate (nickel (II) octanoate hydrate, nickel (II) oxide, nickel (II) peroxide hydrate, nickel (II) phosphide, nickel (II) Citrate, nickel (II) Nickel sulfamate tetrahydrate, nickel (II) sulfate hexahydrate, nickel (II) sulfate heptahydrate, nickel (III) oxide III) oxide, nickel (III) hydroxide, potassium nickel (IV) fluoride and nickel (II), (III) thiolate compounds (II), (III) thiolate complexes, potassium tetracyanonickelate (II), and potassium tetracyanonickelate (II) hydrate.

Step 5-Form the Gold Layer

The nickel-coated polymer beads obtained in the fourth step are dispersed in a gold solvent to form a gold layer on the nickel layer. Gold solutions can be purchased and used on the market or a variety of gold solutions can be used.

Representative examples of the gold solution include gold (III) bromide hydrate, gold (I) chloride, gold (III) chloride, and gold (III) chloride tri. Hydrate (gold (III) chloride trihydrate), gold (I) cyanide, gold (III) hydroxide, gold (I) iodide ) iodide), gold (III) oxide hydrate, gold (I) sulfide, gold (III) sulfide, potassium tetrabromoau Potassium tetrabromoaurate, sodium tetrabromoaurate (III) hydrate, sodium tetrachloroaurate (III) dihydrate, sodium tetraaurate (III) ) Sodium tetraaurate (III) hydrate, potassium gold (III) claw Potassium gold (III) chloride, lithium tetrachloroaurate (III), sodium tetrabromoaurate (III) hydrate, potassium tetraiodoau And latex (III) (potassium tetraiodoaurate (III)).

Electroconductive balls produced in this way is a surface of the nanoparticle size irregularities are formed to have a rough surface without having a conventional smooth surface. Such a surface structure may be prepared according to the manufacturing method of the present invention described above, and other than the nickel layer and the gold layer as long as the ion dissociable metal layer may be ion-bonded, such as palladium ions, and the ion dissociable metal layer may be ion-bonded. Metal layers may also be used, in particular using metal layers of nanoparticle size.

The conductive balls produced by this method are a structure in which a polymer bead, a metal ion layer ionically bonded to the polymer bead surface, and an ion dissociable metal layer formed on the metal ion layer are bonded to the polymer bead. It will have a morphology with irregularities formed.

Hereinafter, the present invention will be described in more detail with reference to the following examples. The present invention is not limited by the following examples, and those skilled in the art will be able to variously modify and change the present invention. Therefore, it is apparent that the scope of the present invention is defined by the matter described in the appended claims rather than the specific embodiments.

Example

1) Polymer Bead Preparation

Through dispersion polymerization, uniform polymer beads having several micro sizes were prepared in a single process. Initiators (benzoyl peroxide, AIBN), polyvinylpyrrolidone, polyvinylacetate, hydroxylpropyl-cellulose (hydroxylpropyl-cellulose) as a dispersant in a solvent such as ethanol, isopropyl alcohol, distilled water, toluene, methanol cellulose, butyl acrylate, styrene monomer, and divinylbenzen were mixed and dissolved at a predetermined ratio to prepare polystyrene polymer beads by reacting at 50-70 ° C. for 12-24 hours. It was. It was confirmed that the size of the polystyrene beads is 500nm-10μm. The prepared polystyrene beads were washed several times with ethanol, methanol and distilled water, and then dried using a centrifuge and a lyophilizer.

2) Preparation of polymer beads surface-modified with sulfone groups

The prepared polystyrene beads were added together with chlorosulfonic acid, sulfonic acid, and acetic sulfide solution in a reaction tank and reacted at a stirring speed of 10-150 rpm. The reaction temperature was maintained at 0-30 ° C. After reacting for 5 hours, neutralization was performed with ethanol, methanol, distilled water, and the like to obtain sulfonated polystyrene beads. Because of the heat of reaction during the neutralization process, the temperature of the reaction tank can be raised sharply, thereby suppressing the temperature rise with liquid nitrogen.

3) palladium catalyst layer formation

100 ml of 50 mmol palladium (II) chloride (PdCl ₂ ) solution was added to a beaker and stirred at a rate of about 50 rpm, while maintaining the reaction temperature at 60 ° C., and about 0.5 g of surface-modified polystyrene beads could be adsorbed for about 1 hour. Impregnated so that. The palladium ions may be impregnated for 10 minutes to 24 hours depending on the concentration and the temperature so as to be sufficiently adsorbed on the modified surface.

It was rotated at 4000 rpm through a centrifugal separator to obtain polystyrene beads having a palladium catalyst layer. The mixture was washed 5 times or more with distilled water, and added to 400 ml of a solution of sodium borohydride (NaBH ₄ ) 0.1M, and stirred slowly. At this time, the reaction temperature was 60 ℃, the reaction time was 12 hours.

4) Nickel layer formation

The polystyrene beads in which the catalyst layer was formed were added to 1 L of nickel solution and reacted with agitation at 88 ° C. for 25 minutes. Centrifugation and distilled water were used to remove the nickel solution remaining after the reaction. The washing process was carried out five times.

5) gold layer forming

The polystyrene beads having the nickel layer formed therein were placed in 1 L of gold solution and reacted at 90 ° C. for 30 minutes by stirring. Unreacted gold solution was removed by the same washing process as the nickel layer was formed.

[Test Example]

The conductive test prepared according to the embodiment was subjected to the following test for confirming the physical properties.

Test Example  One: Morphology  compare

Conventional Conductive Ball (A): The conventional conductive ball manufacturing method is a method of adsorbing tin chloride to polymer beads whose surface is not modified with sulfonic acid or other functional groups and then reducing palladium. Bonding of the polymer results in weak bonding due to physical bonding. For comparison, the morphology and electrical properties of metals were investigated using commercially available conductive balls from Sekisui. A field emission scanning electron microscope (SEM, JEOL. JSM 890) photograph is shown in FIG. 1 to confirm the morphology of the conductive ball B prepared according to the embodiment of the present invention. In the conventional (Sekisui) conductive ball A, it was confirmed that the metal layer forms the smooth surface. On the other hand, in the conductive ball (B) of the present embodiment it can be seen that a large number of gold nanoparticles are formed on the polystyrene surface.

Test Example  2: connection resistance test

Figure 2 shows a graph of force vs. strain and resistance change measured using a micro-compression tester (Shimazu, MCT-W) and a digital multimeter (Advantest, R6552), respectively. .

In the conventional conductive ball A, the resistance was not measured any more when the strain was 40% or more, since the coated metal layer is completely separated from the polystyrene surface. In addition, resistance increases within 10%, 20%, and 32% of deformation, which is thought to be caused by the shape of partial lamination between the metal layer and the polymer.

On the contrary, in the conductive ball B manufactured according to the present embodiment, even when the deformation was 40% or more, the separation phenomenon of the metal layer was not observed, and the resistance was also stably measured in the entire range. This indicates that a strong bonding force is formed by chemical bonding of the metal layer and the polymer styrene. In addition, since the morphological structure of the gold nanoparticles causes the applied pressure to be dispersed, it can be directly confirmed that it does not adversely affect the resistance.

1 is a schematic view of each layer of a conductive ball formed in accordance with an embodiment of the present invention, where A is a polymer bead surface-modified by an anion by a sulfonation process, B1 and B2 is a palladium ion-modified polymer bead The form of adsorption (B1) and reduction (B2), C is a form in which a nickel layer is formed, and D represents a schematic diagram of a form in which a gold layer is formed.

2 shows a scanning electron micrograph A of a conventional conductive ball and a scanning electron micrograph B of a conductive ball manufactured according to an embodiment of the present invention.

3 shows a graph (A) for the load-tensile curve and resistance for a conventional conductive ball and a graph (B) for the load-tensile curve and resistance for a conductive ball made according to an embodiment of the present invention, respectively. .

Claims (17)

A first step of ionizing and modifying the polymer bead surface; Adsorbing ions to the modified polymer beads; A third step of reducing the adsorbed ions; And And a fourth step of forming a metal layer by ion bonding on the reduced ion layer. The method of claim 1, Ionization reforming in the first stage, A method for producing a conductive ball, characterized in that the functional group selected from a sulfone group, a carboxyl group, an amine group, a hydroxyl group, a siol group, and a phosphate group is bonded to the polymer bead surface. The method of claim 2, Bonding a sulfone group as the ionization modification, Chlorosulfonic acid, sulfonic acid, or acetic sulfide is made to react with a polymer surface, and the manufacturing method of the conductive ball characterized by the above-mentioned. The method of claim 1, Ion adsorption in the second step is carried out by impregnating a palladium compound solution in the ion-modified polymer beads. The method of claim 4, wherein The palladium compound, Palladium (II) nitrate hydrate, palladium (II) oxide, palladium (II) oxide hydrate, palladium (II) potassiumthiosulfate monohydrate, palladium (II) propionate, palladium (II) sodium chloride, palladium ( II) sulfate, palladium (II) trifluoroacetate, potassium tetrachloropalladate (II), sodium tetrabromopalladate (II), sodium tetrabromopalladate (II) hydrate, potassium hexachloropalladate (IV ), Sodium tetrachloropalladate (II). The manufacturing method of the conductive ball characterized by the above-mentioned. The method of claim 1, Reduction of adsorbed ions in the third step, Using a reducing agent selected from the group consisting of sodium borohydride, hydrazine, sodium sulfate, sulfite, sodium sulfide, iron ions, lithium aluminum hydride, lithium hydride, diisobutylaluminum hydride, oxalic acid and lindla catalyst And conductive ball production. The method of claim 1, The formation of the metal layer in the fourth step is carried out using a metal compound which can be dissociated into a cation or an anion depending on the modified surface ion state. The method of claim 1, The metal layer in the fourth step is conducted using a metal selected from the group consisting of nickel, gold, silver, copper, palladium, iron, zinc, tin, chromium, magnesium, platinum, indium and alloys thereof. Method of preparation. The method of claim 1, The metal layer is formed in the fourth step, after the nickel layer is formed, a gold layer is formed on the formed nickel layer. The method of claim 9, Formation of the nickel layer, Nickel (II) Acetate Tetrahydrite, Nickel (II) Acetacetonate, Nickel (II) Bis (2,2,6,6-Tetramethyl-3,5 Heptanedionate), Nickel (II) Bromide, Nickel ( II) bromide hydrate, nickel (II) bromide-ethylene glycol dimethyl ether compound, nickel (II) carbonate hydroxide tetrahydrate, nickel (II) chloride, nickel (II) chloride hexahydrate, nickel (II) chloride hydrate , Nickel (II) cyclohexane butyrate, nickel (II) 2-ethylhexanoate, nickel (II) fluoride, nickel (II) fluoride tetrahydrate, nickel (II) hexafluoroacetylacetonate hydrate, nickel (II) Hydroxide, nickel (II) iodide, nickel (II) molybdate, nickel (II) nitrate hexahydrate, nickel (II) 5,9,14,18,23,27,32,36 Octabutoxy-2,3-naphthalocyanine, nickel (II) Octanoate hydrate, nickel (II) oxide, nickel (II) peroxide hydrate, nickel (II) phosphide, nickel (II) citrate, nickel (II) sulfamate tetrahydrate, nickel (II) sulfate Hexahydrate, nickel (II) sulfate heptahydrate, nickel (III) oxide, nickel (III) hydroxide, potassium nickel (IV) fluoride and nickel (II), (III) thioleate compounds The electroconductive ball manufacturing method characterized by using a nickel compound. The method of claim 9, Formation of the gold layer, Gold (III) bromide hydrate, gold (I) chloride, gold (III) chloride, gold (III) chloride trihydrate, gold (I) sineide, gold (III) hydroxide, gold (I) iodide, Gold (III) oxide hydrate, Gold (I) sulfide, Gold (III) sulfide, potassium tetrabromoaurate, sodium tetrabromoaurate (III) hydrate, sodium tetrachloroaurate (III) dihydrate, sodium Gold selected from the group consisting of tetraaurate (III) hydrate, potassium gold (III) chloride, lithium tetrachloroaurate (III), sodium tetrabromoaurate (III) hydrate and potassium tetraiodoaurate (III) It performs using a solution, The manufacturing method of the conductive ball characterized by the above-mentioned. A first step of modifying the polymer bead surface by sulfonating directly with a sulfone group; Adsorbing palladium ions to the modified polymer beads; A third step of reducing palladium ions adsorbed to the polymer beads; Forming a nickel layer on the surface of the polymer beads coated with palladium; And And a fifth step of forming a gold layer on the surface of the polymer bead having the nickel layer formed thereon. delete delete delete delete A conductive ball having a structure comprising a polymer bead, a nickel layer formed by ion bonding on the surface of the polymer bead, and a gold layer formed on the nickel layer, The nickel layer and the gold layer is in the form of a nanoparticle stack, conductive ball, characterized in that having a raspberry-type morphology by the selective surface formation of the nanoparticles.

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