JP2007081198A - Method for conductive connection between terminals - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method for conductive connection that achieve high density and high integration in a field of circuit design. <P>SOLUTION: The method for conductive connection between terminals uses a conductive adhesive which contains a metal component and a thermosetting resin component, and the fusion point of the metal component is lower than the setting temperature of the resin component. The method for conductive connection includes a state of supplying the conductive adhesive to between the terminals, a stage of applying heat to the conductive adhesive to form a conductive tie part of the fused metal component between the terminals, and a stage of further applying heat to cure the resin component to seal the tie part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for conductively connecting terminals for component mounting or wiring formation on an electronic circuit board.

  In recent years, in electronic component mounting, there has been a growing demand for improved mechanical properties and improved reliability characteristics such as thermal shock strength at the joints between terminals. On the other hand, with increasing interest in protecting the global environment, laws and regulations regarding the disposal of industrial waste such as electronic circuit boards are also being advanced. Since lead is also subject to such laws and regulations, materials for component mounting and wiring formation are also shifting to materials that do not contain lead (so-called lead-free materials).

  In the field of mounting components on electric circuits and / or electronic circuits, an anisotropic conductive film (ACF (Anisotropic conductive film) (ACF) is used as one means for conductively connecting terminals of substrates on which electronic components are already mounted. Conductive Film)) is adopted. An anisotropic conductive film is generally a material in which conductive particles are dispersed in a thermosetting resin film-like or sheet-like material so as not to contact each other. When an anisotropic conductive film is arranged between two substrates and the two substrates are pressed and heated in the direction of each other, and thus in the thickness direction of the anisotropic conductive film, the pressurized thickness direction The conductive particles can only be agglomerated and brought into contact with each other to form conductive connecting portions or crosslinks, while the conductive particles are not brought into contact with each other in the plane direction of the anisotropic conductive film. The material having an anisotropic function that can maintain an insulating state in a portion where the pressure and heating of the anisotropic conductive film have not been achieved.

Such an anisotropic conductive film is supplied in a sheet form or a tape form, and electrically connects a flexible printed circuit board (FPC board) and a printed circuit board (PCB) on which an IC or other electronic component is already mounted. Are connected to each other to form a highly integrated mounting substrate, and to a technology for connecting a panel electrode connecting portion of a flat display panel such as an LCD and a flexible printed circuit (Patent Documents 1 and 2). ).
JP 2004-087940 A JP 2004-184805 A

  One example of electrically connecting two substrates using an anisotropic conductive film is schematically shown in FIG. In addition, in this specification, when describing each of the upper, lower, left, and right directions of the members shown in the drawings with reference to the drawings, it should be understood that the directions are the upper, lower, left, and right directions when viewed toward the drawings.

  FIG. 3A shows a terminal 3 provided on the upper surface side of the right end portion of the printed circuit board 1 on which the electronic components 2 and 2 ′ are respectively attached to the lower surface side and the upper surface side, and an electronic component 5 on the upper surface side. The example which connects the terminal 6 provided in the lower surface side of the left end part of the printed circuit board 4 to which is attached by the anisotropic conductive film 10 is shown. FIG. 3B shows an enlarged cross-sectional view of a circled portion where the terminals 3 and 6 and the anisotropic conductive film 10 are in contact with each other in FIG. The anisotropic conductive film 10 is configured by dispersing conductive particles 12 in a thermosetting resin material 11 formed in a film form.

  In order to heat and press the anisotropic conductive film 10 between the terminals 3 and 6, the printed circuit board 1 is supported by the substrate stage 7 from the lower surface side, and the printed circuit board 4 is heated and pressed from the upper surface side. Heat and press with 8. That is, by applying predetermined heat and pressure between the substrate stage 7 and the heating and pressing tool 8, the anisotropic conductive film 10 is heated and pressed (or thermocompression bonding) between the substrate 1 and the substrate 4. To do. As a result, between the terminals 3 and 6, the conductive particles 12 in the thermosetting resin material 11 aggregate in the direction in which the terminals 3 and 6 are in communication with each other and come into contact with each other. A conductive cross-linked portion or a connecting portion is formed between the two. In this way, a conductive connection can be formed between the terminal 3 and the terminal 6.

  However, in order to form a conductive connection between the terminals of two substrates using an anisotropic conductive film in this way, a substrate stage 7 and a heating and pressing tool 8 as shown in FIG. In general, it is necessary to apply a pressure of at least about 2 Pa to the anisotropic conductive film, and thus to the two substrates, using a pressure jig. Electronic parts, such as semiconductor parts, are often sensitive to mechanical external force, and are easily damaged or damaged when external force is applied. Heating using a pressure jig as shown in FIG. In the case of pressure bonding, electronic components cannot be arranged on the outer surface of the substrate with which the pressing jig abuts (for example, the lower surface 3 ′ of the substrate 1 surrounded by a broken line in FIG. 3A).

  Therefore, on the substrate, the area in which the terminals are provided and the area in a certain range on both the front and back sides of the area on the back surface side thereof cannot be used for mounting the electronic component. This has been one factor that hinders higher density and higher integration in the field of circuit design where higher density and higher integration are desired.

In addition, when a pair of substrates in which a plurality of terminals are arranged in a predetermined pattern in a predetermined pattern are opposed to each other and a conductive connection is to be formed between corresponding terminals of both substrates, An anisotropic conductive film material having a size and shape covering the entire region where the terminals are provided has been used. A cross-sectional view taken along the line III-III in FIG. 3B is shown in FIG. As can be understood from FIG. 3 (c), the anisotropic conductive film 10 is compressed in the vertical direction in the portion where the terminals 3 and 6 are opposed to each other by the operation of heating and pressing. Particles 12 can agglomerate between terminals 3 and 6 to form a conductive connection between terminals 3 and 6. On the other hand, the anisotropic conductive film 10 in the region where no terminal exists is not compressed to such an extent that the conductive particles 12 aggregate to form a conductive connecting portion. Accordingly, it is possible to maintain insulation in a region where no terminal exists. In this case, in the region where no terminal exists in the vertical direction, the conductive particles 12 in the anisotropic conductive film 10 do not contribute to the formation of the conductive connecting portion, resulting in waste as a material. It was.
An object of the present invention is to solve the problems related to higher density and higher integration in the field of circuit design as described above.

  The invention of this application comprises a metal component and a thermosetting resin component, and the conductive connection between at least two terminals by a conductive adhesive whose melting point of the metal component is lower than the curing temperature of the resin component. A step of supplying a conductive adhesive between the terminals, a step of applying heat to the conductive adhesive to form a conductive connecting portion between the terminals by a molten metal component, and a further step of heating. The invention further includes a step of curing the resin component to seal the connecting portion. The curing temperature of the resin component is preferably 0 to 50 ° C., particularly 10 to 20 ° C. higher than the melting point of the metal component.

  Since the metal component of the conductive adhesive used in this method has a melting point lower than the curing temperature of the resin component, when subjected to a general heating process of heating from a temperature near room temperature, the melting point of the metal component is reduced. When reached, the metal component melts and the metal component communicates with each other to form a conductive connection that bridges between the two terminals. During this process, the resin component is fluid.

  Thereafter, when the resin is further heated to reach the curing temperature of the resin, the resin is cured by surrounding the conductive connecting portion. Accordingly, a connecting portion having conductivity can be provided between the two terminals, and a sealing portion made of resin surrounding the conductive connecting portion can be provided. Therefore, according to this invention, when connecting the terminals of two substrates, it is essentially unnecessary to press the back side of the terminals of each substrate with a pressure jig, and the temperature conditions are manipulated. Thus, a conductive connection can be formed between the two terminals. Since the pressing jig or the like does not come into contact with the back side of the terminal on the board, it can be used as an area for mounting electronic components, and the mounting density or integration degree of electronic components on the board can be further improved. it can.

  In one aspect, the present invention is characterized by using a fluid conductive adhesive in which a metal component in the form of particles is dispersed in a resin component. The ratio of the weight of the metal component to the total weight of the conductive adhesive is preferably 5 to 50% by weight, particularly 10 to 30% by weight. The metal component particles preferably have an average particle size in the range of 5 to 30 μm. Among them, the particles of the metal component have a particle size in the range of 20 to 40 μm, preferably an average particle size of 30 μm. However, in some cases it may have a particle size of 5 to 150 μm. According to this aspect, the resin component in which the metal component in the form of particles is dispersed is supplied only to a necessary portion between the contacts to be connected to each other, and the terminals are conductively connected by an operation such as subsequent heating. be able to. Therefore, the conductive adhesive can be applied in a necessary amount to a necessary part, and waste of the metal material and the resin material can be prevented.

  In another aspect, the present invention provides that the step of supplying the conductive adhesive includes the step of supplying a metal component to the terminal surface and the step of subsequently supplying the resin component to the terminal surface. Features. According to this aspect, the conductive adhesive is supplied separately for the metal component and the resin component, but at the stage of preparing the base material having the terminal to be connected, the necessary portion of the terminal surface is previously provided. When supplying the necessary amount of metal component, when connecting the terminals, supply the resin component between the terminals, and then electrically connect the terminals by an operation such as heating. can do. Therefore, according to this aspect, the conductive adhesive can be applied in a necessary amount to a necessary portion, and waste of the metal material and the resin material can be prevented.

  In another aspect, the present invention is characterized in that the metal component comprises Sn and at least one metal selected from the group consisting of Ag, Bi, and In. The metal component of this embodiment is an alloy composition comprising Sn and at least one metal selected from the group consisting of Ag, Bi, and In, and is in the range of 70 to 250 ° C., particularly in the range of 80 to 150 ° C. The melting point can be set. Therefore, according to this aspect, mounting can be performed at a relatively low temperature.

  When the metal component contains Bi, the Bi content in the metal component is preferably in the range of 10 to 70% by weight, and more preferably in the range of 50 to 70% by weight. The Bi content in the metal component is set to 10 to 70% by weight. If the Bi content is less than 10% by weight, the effect of lowering the melting point is not sufficiently obtained. This is because the effect of lowering the melting point cannot be obtained.

  When the metal component contains In, the content of In in the metal component is preferably in the range of 10 to 90% by weight, and more preferably in the range of 10 to 30% by weight. The reason why the content of In in the metal component is set to 10 to 90% by weight is that if the content of In is less than 10% by weight, the effect of lowering the melting point cannot be sufficiently obtained. Similarly, the effect of lowering the melting point cannot be obtained.

Moreover, the content of Ag in the metal component is preferably in the range of 0.1 to 5.0% by weight, and more preferably 3 to 5% by weight. If the Ag content in the metal component is 0.1 to 5.0% by weight, if it is less than 0.1% by weight, no effect on the mechanical properties can be obtained, and if it exceeds 5% by weight This is because the melting point of the alloy rises rapidly.
The balance in the metal component may be Sn, or may contain other metal elements in addition to Sn if desired.

  In another aspect, the present invention is characterized in that the metal component further contains Cu or Ni. The metal component of this aspect can also set melting | fusing point in the range of 70-250 degreeC, especially the range of 80-150 degreeC similarly to said alloy composition. Therefore, according to this aspect, mounting can be performed at a relatively low temperature.

  The metal component of the present invention can further contain at least one metal selected from the group consisting of Cu and Ni in addition to the above basic composition. Cu is added for the purpose of improving the mechanical properties of the alloy.

  The Cu content in the metal component is preferably in the range of 0.1 to 1.0% by weight, and more preferably in the range of 0.5 to 0.7% by weight. If the Cu content is less than 0.1% by weight, the effect on the mechanical properties cannot be obtained, and if the Cu content exceeds 1.0% by weight, the alloy tends to become more brittle and the mechanical properties are reduced. This is because it is counterproductive.

  The addition of Ni to the metal component is aimed at suppressing the oxidation of Sn. The content of Ni in the metal component is preferably 0.01 to 0.1% by weight. The Ni content in the metal component is set to 0.01 to 0.1% by weight. If the amount is less than 0.01% by weight, the effect of suppressing Sn oxidation cannot be obtained. This is because if it exceeds, a strong Ni oxide film is formed, the melting point rises, and the effect of suppressing Sn oxidation cannot be obtained.

  These low melting point metal components are preferably dispersed in the conductive adhesive composition in a particulate form. The average particle size of the metal component is preferably 5 to 30 μm.

  The ratio of the weight of the metal component to the entire conductive adhesive composition used in the present invention can be selected from an appropriate range according to the use of the conductive adhesive, the type of metal component, the type of resin component, and the like. . However, since it is necessary to form a conductive connecting portion for connecting the terminals by heating operation, the metal component is 70 to 90% by weight, particularly 80 to 85% by weight, based on the entire conductive adhesive composition. It is preferable that If the proportion of the metal component is less than 70% by weight, sufficient conductivity cannot be obtained after curing, and if it exceeds 90% by weight, there is a possibility that the conductive path cannot be sufficiently surrounded by the resin. In addition, since the alloy obtained by melting the metal component has a lower melting point than that of the lead-free solder material or Sn—Pb solder material, a lower mounting temperature can be achieved.

  In a further aspect, the present invention is characterized in that the resin component includes a resin having a reducing property as the second component, the resin component includes a compound having a carboxyl group as the second component, The resin component may contain an organic compound containing a metal, or the metal may be selected from the group of Na, Ag, Cu, and K. According to these aspects, a metal component having a relatively low melting point can be more easily melted.

  As the resin component, various thermosetting resins known to those skilled in the art can be used. As the thermosetting resin, an epoxy resin, an acrylic resin, a phenol resin, a polyimide resin, a thermosetting polyurethane resin, an unsaturated polyester resin, or the like can be used. A preferable thermosetting resin is an epoxy resin. It is. Various types of epoxy resins such as a one-component curable type and a two-component curable type can be used, but a one-component curable type is preferable. Further, the thermosetting resin basically requires a thermosetting resin system known to those skilled in the art (a specific curable resin and a specific type of curing agent required for the curing, a viscosity modifier, and the like. (A system containing in an amount) can be used as a resin component.

  For example, when an electronic component is mounted using a conductive adhesive, if the metal component particles are heated during the heat curing process, the surface of the metal component particles may possibly be melted before the metal component particles melt. As a result, the oxide film may be formed on the surface of the metal component particles. The oxide film formed on the surface of the metal component particles becomes a kind of protective film that prevents the melting of the metal component particles, and prevents the metal component from melting at a predetermined temperature in the heat curing process of the conductive adhesive. Can do. As a result, metal component particles that could not be sufficiently melted after the heat curing process may remain.

  In such a case, the resin component includes a reducing resin component, a resin component containing a compound having a carboxyl group, a resin component containing an organic compound containing a metal, and / or Na, Ag, Cu and K. Since the resin component containing the organic compound containing the metal selected from the group is included, the inside of the conductive adhesive composition can be kept in a reducing atmosphere to some extent even during the heat curing process. Therefore, it is possible to substantially prevent the formation of an oxide film on the surface of the metal component particles during the heat curing process. By preventing the oxidation of the surface of the metal component particles during the heat curing process, it is possible to prevent the melting failure of the metal component during the heat curing process and promote the melting of the metal component.

  In one embodiment, the reducing resin preferably contains a compound having a carboxyl group, such as a carboxylic acid. By adding such a compound to the resin, the oxide film of the low melting point metal is removed (or the formation of an oxide film on the surface of the low melting point metal is prevented) and acts as a reducing agent to facilitate melting. Can be expressed. In addition, various carboxylic acids, such as aliphatic carboxylic acid, aromatic carboxylic acid, alicyclic carboxylic acid, can be used for such a compound. Examples of such compounds are adipic acid, abietic acid, ascorbic acid, acrylic acid, citric acid, polyacrylic acid, malic acid, pimelic acid, palmitic acid, myristic acid, lauric acid, sebacic acid, suberic acid, maleic acid Succinic acid, azelaic acid, fumaric acid, glutaric acid, malonic acid and the like. The carboxylic acid is preferably in the form of a metal salt such as Na, Ag, Cu, or K.

  In another embodiment, when the resin component contains an organic compound containing a metal, the metal is stably combined with or bonded to the organic compound at room temperature without being liberated, but when heated, the metal becomes an organic compound. As a result, the released metal accelerates the curing reaction of the resin. As a result, it can act as a curing agent that achieves both short-time curing and storage stability. In addition, it is preferable that such a metal is at least 1 sort (s) of the group of Na, Ag, Cu, and K.

  In another embodiment, when the organic compound containing a metal contains a carboxyl group or an amino group, the reducing agent derived from the carboxyl group or amino group acts as a curing agent derived from the organic compound containing the metal. The action is synergistically exhibited in the heat curing process, and can act as a good reducing agent.

  Regarding the invention of the present application, in the resin component, the ratio of the weight of the thermosetting resin component and the second resin component is in the range of 90:10 to 10:90, particularly in the range of 50:50 to 80:20. preferable. The ratio of the resin component to the metal component is preferably 20% by weight or less. This is because when it exceeds 20% by weight, no further change is observed in the action as a reducing agent and / or a curing agent. In addition, in order to recognize said effect, it is preferable that the ratio of a resin component is 10 weight% or more. In addition, when the 2nd resin component acts as a hardening | curing agent, the usage-amount of the hardening | curing agent used for a 1st resin component can also be reduced.

  The conductive adhesive described above is a liquid or paste-like material by adjusting the composition of the thermosetting resin or by appropriately selecting other ingredients such as a viscosity modifier, a dispersant and other materials. It can be supplied as a coating type adhesive having properties, or as a type of adhesive that has a sheet-like or tape-like form and is cut and used.

  This application also provides an invention of a device having a circuit connected by the connection method according to any one of the above-described inventions. Such a device can have the advantages of the respective connection methods described above.

  According to the invention of the present application, when the terminals of the two substrates are connected to each other by the conductive adhesive, by controlling the temperature condition, the conductive connecting portion for connecting the terminals to each other and the sealing by the resin surrounding the conductive connecting portion. Since a stop part can be provided, it is not necessary to press each board | substrate with a pressurization jig | tool, and low load joining can be implement | achieved. Therefore, it is possible to achieve high density and high degree of integration in circuit design by securing a wider area for mounting electronic components on the substrate surface.

(Best Mode for Carrying Out the Invention)
(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A shows a terminal 3 provided on the upper surface side of the right end portion of the printed circuit board 1 on which electronic components 2 and 2 ′ are respectively attached to the lower surface side and the upper surface side, and an electronic component 5 on the upper surface side. The example which connects the terminal 6 provided in the left side edge part of the lower surface side of the printed circuit board 4 to which is attached using the conductive adhesive 20 is shown. At the right end of the printed circuit board 1, an electronic component 2 ″ is also attached to the back side of the area where the terminals 3 are provided (and hence the bottom side of the printed circuit board 1).

  FIG. 1B shows the longitudinal sections of the substrates 1 and 4 extending in the left-right direction in FIG. 1A in which the terminals 3 and 6 are in contact via the conductive adhesive 20. Sectional drawing which expanded the part enclosed with the circle of (a) is shown. FIG. 1B shows a state before heating. As shown in FIG. 1B, the conductive adhesive 20 before heating is composed of particles of the metal component 22 in the thermosetting resin 21 in an uncured state. Is in a dispersed state.

  The operation of heating the conductive adhesive 20 is performed so that the substrate 4 and the substrate 1 are in contact with each other as shown in FIG. Can be done. With respect to this operation, the heating tool 9 does not need to fulfill the function of applying a substantial pressing force to the upper surface side of the substrate 4. What is important is that the heating tool 9 presses the upper surface side of the substrate 4 so as to maintain an interval that allows the substrate 4 and the substrate 1 to contact each other via the conductive adhesive 20. The upper surface side of the substrate 4 may be pressed by adjusting the distance between the substrate 4 and the substrate 1. Correspondingly, the substrate 1 may be supported by, for example, a buffer mechanism so that the heating tool 9 does not shift downward when the upper surface side of the substrate 4 is pressed. Accordingly, since the substrate 1 is not pressed by the pressing jig, the electronic component 2 ″ can be attached to the lower surface side of the printed circuit board 1, and the surface area of the printed circuit board 1 is useful for mounting the electronic component. Note that the heating means is not limited to a heating tool, for example, the substrate 1 and 4 can be heated in an atmosphere by heating them in a chamber that can be heated. Alternatively, the atmosphere heating by the chamber and the heating by the heating tool can be performed in combination.

  In the heated conductive adhesive 20, the metal component 22 melts and becomes liquid, and the liquefied metal components are united and communicated with each other, as schematically shown in FIG. In addition, the conductive connection portion 24 is formed by forming and maintaining the shape of the flow path through which the fluid can flow in the volume of the applied conductive adhesive 20 while spreading on the surfaces of the terminals 3 and 6. In the example of FIG. 1 (c), the metal component 22 is united at the central portion of the conductive adhesive 20, and a connecting portion 24 made of a massive metal is formed between the terminal 3 and the terminal 6. can do. On the other hand, the thermosetting resin component 21 that is still fluid at the melting point of the metal component 22 surrounds the conductive connecting portion 24.

  When the temperature further rises and reaches the curing temperature of the thermosetting resin 21, the thermosetting resin component 21 can be cured while surrounding the conductive connecting portion 24. Therefore, as schematically shown in FIG. 1C, a conductive connecting portion 24 and a cured resin cured resin 25 surrounding and sealing the conductive connecting portion 24 communicate between the terminal 3 and the terminal 6, Therefore, it can be considered that the terminal 3 and the terminal 6 can be conductively connected.

  FIG.1 (d) has shown the II sectional view taken on the line in FIG.1 (c). In the example shown in FIG. 1D, the conductive adhesive is supplied so as to cover the entire region where a plurality of terminals are arranged, as in the case of using the ACF. When the ratio of the weight of the metal component to the total weight of the conductive adhesive is in the range of 5 to 50% by weight, preferably 10 to 30% by weight, and the pitch between the terminals is 200 μm, the metal component particles are 20 to 20%. When having a size in the range of 40 μm and an average particle size of 30 μm, the conductive adhesive is supplied so as to cover the entire region in which the plurality of terminals are arranged as described above. After the heat treatment, it was confirmed that almost all the metal components present in the conductive adhesive were gathered at the connecting portion 24 between the terminals 3 and 6. That is, almost no metal component remains in the region where the terminal does not exist in the vertical direction, and therefore almost the entire amount of the metal component blended in the conductive adhesive can be used for forming the conductive connection. Accordingly, a relatively expensive metal material can be effectively used.

  In relation to the first aspect of the present invention, as shown in Table 1, the metal components having the compositions corresponding to Examples 1 to 22 are blended, and the resulting blend (and hence the alloy having the corresponding composition) The melting point was measured using a differential thermal analyzer.

  Moreover, the conductive adhesive was produced using the metal component of the composition corresponding to said each Example. In all examples, a thermosetting epoxy resin was used as the resin. Examples of preferable epoxy resins for use in the present invention include Epicoat 828 and Epicoat 807 (manufactured by Japan Epoxy Resin (JER)), and 2PHZ (manufactured by Shikoku Chemicals) as a curing agent. The curing temperature is 150 ° C. for 10 minutes. The metal component may also be powder or flake metal fine particles that are generally available industrially. A conductive adhesive composition is prepared by blending 20% by weight of a metal component with 80% by weight of the resin component and setting the weight ratio of the thermosetting resin component and the second resin component in the resin component to 90:10. did.

  Using the conductive adhesive of each example, the corresponding terminals of the two substrates were bonded to each other as shown in FIG. 1B. Then, it heated and raised temperature to the temperature (about 220 degreeC) exceeding melting | fusing point of a metal component, and also exceeding the curing temperature of a thermosetting resin. This temperature was held for 10 minutes to complete the cure.

  The state of the conductive connecting portion after curing is based on the conductive connecting portion 24 and the cured resin remaining on the surface of the terminal after the pair of substrates are bonded and then the adhesive portion is broken and peeled off again. The state of the sealing part 25 and the state around the terminal were visually observed and evaluated. It was confirmed that the conductive connecting portion was sufficiently melted with the metal component to form a metallic bond, for example, a bond with a bulk metal.

  Regarding the state around the terminal, the number of so-called solder balls existing in the region other than the connecting portion 24 between the terminal 3 and the terminal 6 facing each other in both of the modes shown in FIGS. 1 (d) and 1 (e). Measured by visual inspection using a loupe. The measured number of solder balls is shown in the column of the number of balls generated between the wirings in Table 1. This solder ball is surrounded and sealed by a hardened resin component around the metal component, like the conductive connection between the terminals, and is fixed to the surface of the substrate, which reduces the bonding reliability. Can be understood as not connecting.

(Second Embodiment)
Using the metal component (Sn43-Bi57) having the composition of Example 1 and blending each organic compound shown in Table 2 below as a resin component to be blended, a conductive adhesive was prepared. The weight ratio of the resin component to the metal component was 80:20, and the weight ratio of the thermosetting resin component to the second resin component in the resin component was 90:10.

  When adipic acid, abietic acid, ascorbic acid, acrylic acid, citric acid, polyacrylic acid, etc. are used as the resin having the reducing property of the second component, the meltability of the metal component containing Sn is improved and the wiring resistance is improved. It was confirmed that it decreased. Moreover, when the joint part after hardening was observed, it has confirmed that the metal component was fully fuse | melted and the metal coupling | bonding, for example, the coupling | bonding by a bulk metal, was formed.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. The arrangement and names of the members in FIG. 2A are substantially the same as those in FIG. FIG. 2B shows an enlarged cross-sectional view of the state surrounded by a circle where the terminals 3 and 6 and the conductive adhesive 20 are in contact with each other in FIG. Moreover, FIG.2 (c) has shown the state after the heating of the part corresponding to FIG.2 (b).

  In 3rd Embodiment, as shown in Table 3 described below, the metal component of the composition corresponding to Examples 28-38 was mix | blended, and it used for the 3rd Embodiment of this invention. Melting | fusing point of the metal component of each Example was measured using the differential thermal analyzer. The resin component used as the conductive adhesive was the same as that in the first embodiment.

  As can be understood from FIG. 2B, in this embodiment, the step of supplying the conductive adhesive includes the step of supplying a metal component to the terminal surface, and the step of subsequently supplying the resin component to the terminal surface. This is divided into two stages. Specifically, in the step of supplying the metal component to the terminal surface, the metal component layer 26 is formed by covering the surface of the terminal 3 on the substrate 1 side with the metal component used in the present invention, and similarly the terminal on the substrate 4 side. This was carried out by forming a metal component layer 26 ′ on the surface of 6. The coating can be performed by plating, for example.

  Thereafter, a thermosetting resin 27 having fluidity is applied to the surface of the terminal 3 provided with the metal component layer 26 in a required amount. The surface of the terminal 6 on the mating side may be applied with a thermosetting resin or without applying a thermosetting resin. The total amount of the thermosetting resin 27 is equal to the amount of the terminals 3 and 6. It is sufficient if it is an amount necessary to be applied in between.

  The terminal 3 and the terminal 6 were opposed to each other, the substrate 4 and the substrate 1 were bonded to each other, and the heating operation was performed in the same manner as in the first embodiment. Therefore, also in this embodiment, the electronic component 2 ″ can be attached to the back side of the terminal 3 in the printed circuit board 1, and the surface area of the printed circuit board 1 can be effectively utilized for mounting the electronic component. it can.

  As a result of the heat treatment, the metal components 26 and 26 'are melted into a liquid state, and the liquefied metal components are united and communicated with each other. As shown schematically in FIG. Forming and holding the shape of the flow path through which the fluid can flow in the thermosetting resin component 21 that is still wettable and spreads on the surface of the film to form a conductive connecting portion 24; The thermosetting resin component 27 surrounds the periphery.

  When the temperature further rises and reaches the curing temperature of the thermosetting resin, the thermosetting resin component can be cured while surrounding the conductive connecting portion 24. Therefore, as shown schematically in FIG. 2 (c), the conductive connecting portion 24 and the sealing portion 25 made of a cured resin surrounding and sealing the conductive connecting portion 24 communicate between the terminals 3 and 6. Therefore, a conductive connection can be formed between the terminal 3 and the terminal 6.

  When the cross-sectional shape of the conductive adhesive portion formed of the conductive connecting portion 24 and the sealing portion 25 formed as described above is observed as a cross-section in the direction of arrows II in FIG. 2C, FIG. It was in substantially the same state. Therefore, according to this embodiment, it is possible to form the conductive connecting portion 24 and the sealing portion 25 of the cured resin only between the terminals 3 and 6 after curing. Therefore, it is possible to prevent the conductive adhesive or the hardened metal component or resin component derived therefrom from being disposed in a region where no terminal exists between the substrate 1 and the substrate 4, and according to this aspect, the adhesive material Can be avoided.

  The evaluation of the conductive connecting part after curing was performed in the same manner as in the first embodiment. The conductive connecting portion 24 is formed by sufficiently melting a metal component to form a metallic bond, for example, a bulk metal bond, and a sealing portion 25 made of a cured resin surrounding the conductive connecting portion 24. The formation of solder balls was not observed in each example. Furthermore, according to this method, the amount of the conductive adhesive to be supplied can be controlled with a very small amount. Therefore, it can be used effectively for connection between substrates provided with wiring having a pitch of about 0.2 mm.

(Particle size confirmation test)
The present invention was tested to confirm the preferred particle size. Using the alloy particles having the composition (43Sn-57Bi) used in Example 1, various particle group samples having an average particle size of 5 to 150 μm were prepared as shown in Table 4, and shown in Example 23. A conductive adhesive was prepared by blending with a resin having a composition. Using this conductive adhesive, wiring of a substrate (a pitch between terminals of 200 μm) was connected as shown in FIG. The curing conditions were the same as in the first embodiment. The defect rate (%) was measured by the occurrence rate of a short circuit occurring between wirings on a connected substrate. As a result, it is confirmed that the metal component particles preferably have an average particle size in the range of 5 to 30 μm, further have a particle size in the range of 20 to 40 μm, and preferably have an average particle size of 30 μm. did it.

(Confirmation test of metal particle ratio)
About this invention, the test which confirms the preferable metal particle ratio in a conductive adhesive was done. Using the alloy particles having the composition (43Sn-57Bi) used in Example 1 and the resin having the composition shown in Example 23, conductive adhesive samples having various metal particle ratios were prepared as shown in Table 5. did. Using this conductive adhesive, wiring of a substrate (a pitch between terminals of 200 μm) was connected as shown in FIG. The curing conditions were the same as in the first embodiment. For the connected substrates, the number of solder balls and the connection strength were measured. As a result, when the metal particle ratio exceeded 50% by weight, the number of solder balls between the wirings increased, and when the metal particle ratio fell below 50% by weight, no solder balls were observed. Moreover, it was recognized that higher connection strength was obtained as the metal particle ratio was smaller. The connection strength is considered to be due to the thermoplastic resin in the conductive adhesive. When these results are combined, it is considered that the metal particle ratio to be blended in the conductive adhesive may be the minimum limit that allows metal bonding between the wirings.

  The connection method between the terminals of the present invention requires the use of a pressure jig by conductively connecting the terminals using a conductive adhesive in which a low melting point metal component and a thermosetting resin are combined. To achieve low load bonding. Therefore, it is possible to secure a wider area for both-side mounting of electronic components on the substrate, and to use the circuit design for higher density and higher integration. Therefore, this method is useful for the connection between the flexible substrate and the flexible substrate on which both electronic parts such as semiconductors are mounted, and between the flexible substrate and the rigid substrate, and a product capable of increasing the density and the degree of integration of the circuit. For example, it can be used for DVDs, mobile phones, portable AV devices, notebook PCs, digital cameras, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the state of the connection between the terminals by the 1st Embodiment of this invention, Comprising: (a) A figure is the schematic of operation which bonds two board | substrates, (b) A figure and (c) figure are ( a) An enlarged cross-sectional view of a portion where the two terminals and the conductive adhesive are in contact with each other in the drawing, and FIGS. (d) and (e) are cross-sectional views taken along arrows II in FIG. ing. It is a schematic diagram which shows the state of the connection between terminals by the 3rd Embodiment of this invention, Comprising: (a) A figure is a schematic diagram of operation which bonds two board | substrates, (b) A figure is 2 in FIG. The expanded sectional view of the part which one terminal and conductive adhesive are contacting, (c) figure has each shown the state after a heating. It is a schematic diagram which shows the state of the connection between the conventional terminals, (a) A figure is a schematic diagram of operation which bonds two board | substrates, (b) A figure is two terminals in (a) figure, and anisotropic conduction. The enlarged sectional view of the part which is in contact with the membrane is shown, and FIG.

Explanation of symbols

1, 4: substrate, 2, 2 ′, 2 ″, 5: electronic component, 3, 6: terminal, 7: substrate stage, 8: heating and pressing tool, 9: heating tool, 10: anisotropic conductive film, 11: Thermosetting resin material, 12: Conductive particles, 20: Conductive adhesive, 21: Uncured thermosetting resin, 22: Metal component particles, 24: Conductive connecting part, 25: Cured resin, 26, 26 ': metal component layer, 27: thermosetting resin component.

Claims (11)

A method of forming a conductive connection between opposing terminals by a conductive adhesive comprising a metal component and a thermosetting resin component, wherein the melting point of the metal component is lower than the curing temperature of the resin component. ,
Supplying a conductive adhesive between the terminals,
Applying heat to the conductive adhesive to form a conductive connecting portion between the terminals by the molten metal component, and further applying heat to cure the resin component to seal the connecting portion. A method for conductive connection between terminals.   2. The conductive connection method according to claim 1, wherein a fluid conductive adhesive in which a metal component in a particle form is dispersed in a resin component is used.   2. The conductive material according to claim 1, wherein the step of supplying the conductive adhesive includes a step of supplying a metal component to the terminal surface and a step of subsequently supplying a resin component to the terminal surface. Connection method.   4. The conductive connection method according to claim 1, wherein the metal component comprises Sn and at least one metal selected from the group consisting of Ag, Bi, and In. 5.   5. The conductive connection method according to claim 4, wherein the metal component further contains Cu and / or Ni.   6. The conductive connection method according to claim 1, wherein the content of the metal component in the conductive adhesive is in the range of 5 to 50% by weight.   The conductive connection method according to claim 1, wherein the resin component includes a resin having reducibility as the second component.   The conductive connection method according to claim 1, wherein the resin component includes a compound having a carboxyl group as the second component.   The conductive connection method according to claim 1, wherein the resin component includes an organic compound containing a metal as the second component.   The conductive connection method according to claim 9, wherein the metal is selected from the group of Na, Ag, Cu, and K.   The apparatus which has the circuit formed by the conductive connection method in any one of Claims 1-10.

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