JP2007084767A - Adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive curable by heating by electromagnetic induction with a high-frequency wave, enabling an electroconductive material to be heated efficiently by the induction heating by the high-frequency electric current when using the high frequency wave-curable adhesive for sticking members to be stuck to each other, and capable of improving the connection reliability between the members to be stuck. <P>SOLUTION: The adhesive contains a thermosetting resin and an electroconductive material heated by the induction heating at the high-frequency heating treatment, and sticks the materials to be stuck to each other by the curing of the thermosetting resin by the heat generation of the electroconductive material. The electroconductive material has a shape of linearly linked many fine particles, or a needle shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive for bonding a member to be bonded such as a substrate or an electronic component provided with an electrode, a circuit, and the like by being heated by a high frequency electromagnetic field.

  Conventionally, in many industrial fields, a method of bonding using an adhesive is used when bonding members. For example, in the electronics packaging field, the miniaturization of connection terminals in component parts is progressing in the trend of downsizing and higher functionality of electronic devices in recent years. Therefore, it is easy to connect such terminals. Various circuit connecting adhesives that can be used are widely used.

  Here, in recent years, a high-frequency curable adhesive that has been cured by heating by high-frequency electromagnetic induction to bond the members to be bonded has been proposed. More specifically, for example, the adhesive is mainly composed of a thermosetting resin or a thermoplastic resin and contains a conductive material such as iron powder, and the adhesive is heated by heat generation of the conductive material due to induction heating of high-frequency current. A high-frequency curable adhesive that heats and adheres members to be bonded is disclosed. It is described that by using such an adhesive, members to be bonded can be quickly bonded (see, for example, Patent Document 1).

Further, an adhesive containing nanoscale particles having ferromagnetism, ferrimagnetism, and superparamagnetism is disclosed as a high-frequency curable adhesive. More specifically, an adhesive containing particles such as aluminum having an average particle diameter of 1 to 500 nm as a conductive substance is disclosed. By using such an adhesive, heat diffusion to the adherend can be prevented without adversely affecting the properties of the adhesive such as heat resistance and shear strength, and the curing time of the adhesive is significantly reduced. (For example, refer to Patent Document 2).
JP-A-8-73818 JP-T-2004-506065

  However, in the conventional high-frequency curable adhesive, the conductive material such as iron powder and aluminum is considered to have a substantially spherical shape. Therefore, the conductive material is efficiently removed by induction heating with a high-frequency current. There was a problem that the adhesive could not be heated efficiently due to heat generation of the conductive material. Moreover, since it is necessary to increase the blending ratio of the conductive material to efficiently heat the conductive material, the blending ratio of the resin that is the main component of the adhesive decreases, and as a result, between the bonded members There was a problem that the connection reliability of the system deteriorated.

  Accordingly, the present invention has been made in view of the above-described problems, and can efficiently heat a conductive substance by induction heating of a high-frequency current and improve connection reliability between bonded members. An object is to provide an adhesive that can be used.

  In order to achieve the above object, the invention according to claim 1 includes a thermosetting resin and a conductive substance that generates heat by induction heating in a high-frequency heat treatment, and is also cured by heat generation of the conductive substance. In the adhesive that bonds the members to be bonded by curing the conductive resin, the conductive material has a shape in which a large number of fine particles are connected in a straight chain or a needle shape.

  According to this configuration, since the conductive material has a shape in which a large number of fine particles are connected in a straight chain or a needle shape, the surface area per unit volume compared to a conductive material having a substantially spherical shape. Becomes larger. Accordingly, since the conductive material can be efficiently heated by induction heating with a high-frequency current, the adhesive can be efficiently heated by the heat generation of the conductive material. In addition, since the conductive substance can be efficiently heated, the blending ratio of the conductive substance in the adhesive can be decreased, and the blending ratio of the thermosetting resin in the adhesive can be increased. As a result, the connection reliability between the adherend members is improved.

  A second aspect of the present invention is the adhesive according to the first aspect, wherein the conductive material has an aspect ratio of 10 or more. According to this configuration, the conductive material can be heated more efficiently by induction heating using a high-frequency current.

  The invention according to claim 3 is the adhesive according to claim 1 or claim 2, wherein the conductive material is a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, and ferromagnetism. It is any one of an alloy of a metal having another metal and a composite containing a metal having ferromagnetism. According to this configuration, the magnetic property of the metal itself enables the conductive material to be oriented in a desired direction using a magnetic field.

  In addition, as an electroconductive substance of this invention, from a viewpoint of an electroconductive improvement and availability, either of nickel, iron, cobalt, and these 2 or more types of alloys as described in Claim 4 It is preferable that

  A fifth aspect of the present invention is the adhesive according to any one of the first to fourth aspects, wherein the conductive material is oriented in the thickness direction of the adhesive. According to this configuration, for example, when a protruding electrode formed on an electronic component and a wiring electrode formed on a circuit board are bonded, insulation between adjacent electrodes is maintained by a high conductive resistance in the surface direction of the adhesive. Thus, while preventing a short circuit, a low conductive resistance in the thickness direction of the adhesive makes it possible to electrically connect a large number of electrodes to each other at once and independently.

  Invention of Claim 6 is an adhesive agent in any one of Claim 1 thru | or 5, Comprising: While the thermosetting resin is an epoxy resin, the said electroconductive substance is disperse | distributed in the said epoxy resin. It is characterized by being. According to this configuration, it is possible to produce an adhesive having excellent film formability, heat resistance, and adhesive strength.

  According to the present invention, when using a high-frequency curable adhesive that is cured by heating by high-frequency electromagnetic induction and adheres between the members to be bonded, the conductive material is efficiently heated by induction heating by high-frequency current. In addition, it is possible to improve the connection reliability between the adherends.

Hereinafter, a preferred embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view showing an adhesive structure bonded with an adhesive according to the present invention, and shows a state in which the adhesive is heated by a high-frequency oscillator. Moreover, FIG. 2 is sectional drawing which shows the state which connected between electrodes with the adhesive agent which concerns on this invention. In the present embodiment, a circuit board on which an electronic component is mounted will be described as an example of an adhesive structure.

  As a method for mounting an electronic component such as an IC chip on a circuit board by using the adhesive according to this embodiment, the above-described high-frequency heating method is employed. That is, with the thermosetting resin as a main component, the adhesive containing the conductive material is heated by induction heating by high-frequency heat treatment, thereby generating heat in the conductive material, and by the heat generation of the conductive material, The thermosetting resin is cured, and the protruding electrode of the electronic component is connected to the wiring electrode of the circuit board.

  More specifically, as shown in FIGS. 1 and 2, an adhesive 3 containing a thermosetting resin as a main component and containing a conductive substance 2 is placed on a circuit board 1 such as a glass substrate. Next, the metal coil 5 included in the high-frequency oscillator 4 is disposed below the circuit board 1 on which the adhesive 3 is placed. The coil 5 is wound around a metal core 10 as shown in FIG. Next, in a state where the electronic component 6 is faced down (face down), the wiring electrode 7 that is a member to be bonded formed on the surface of the circuit board 1 and the protrusion that is a member to be bonded formed on the surface of the electronic component 6 By placing the electronic component 6 on the adhesive 3 while aligning with the electrode 8, the adhesive 3 is interposed between the circuit board 1 and the electronic component 6. Then, when a high-frequency current having a predetermined frequency is passed from the high-frequency power source 9 of the high-frequency oscillator 4 to the coil 5 connected to the high-frequency power source 9 to generate a high-frequency induction magnetic field, an eddy current is generated in the conductive material 2. The conductive material 2 generates heat due to the eddy current, the adhesive 3 is heated, and the adhesive 3 is heated and melted. Then, as described above, since the adhesive 3 is mainly composed of a thermosetting resin, the adhesive 3 softens once when heated at the curing temperature, but by continuing the heating, It will be cured. When the preset curing time of the adhesive 3 has elapsed, the heating state of the adhesive 3 is released, and cooling is started to connect the wiring electrode 7 and the protruding electrode 8 via the adhesive 3, The component 6 is mounted on the circuit board 1.

  In addition, as the adhesive 3 used in the present invention, an adhesive which has been conventionally used for connection of the circuit board 1 and the electronic component 6 and mainly contains a thermosetting resin and contains a latent curing agent. Can be used. Examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyurethane resin, an unsaturated polyester resin, a polyimide resin, and a urea resin. Among these, in particular, by using an epoxy resin as the thermosetting resin, it is possible to improve the film formability, heat resistance, and adhesive strength of the adhesive 3.

  The epoxy resin to be used is not particularly limited. For example, bisphenol A type, F type, S type, or AD type epoxy resin, naphthalene type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, diphenyl type epoxy resin, A cyclopentadiene type epoxy resin or the like can be used. A phenoxy resin that is a high molecular weight epoxy resin can also be used.

  The molecular weight of the epoxy resin can be appropriately selected in consideration of the type of the adherend member. When a high molecular weight epoxy resin is used, the film formability is high, the melt viscosity of the resin at the connection temperature can be increased, and there is an effect that the connection can be made without disturbing the orientation of the conductive material described later. On the other hand, when a low molecular weight epoxy resin is used, the crosslink density is increased and the heat resistance is improved, and the cohesive force of the resin is increased. Therefore, it is preferable to use a combination of a high molecular weight epoxy resin having a molecular weight of 15000 or more and a low molecular weight epoxy resin having a molecular weight of 2000 or less in order to balance performance. In addition, the compounding quantity of a high molecular weight epoxy resin and a low molecular weight epoxy resin can be selected suitably.

  In addition, the latent curing agent used in the present invention is excellent in storage stability at low temperatures and hardly causes an effective reaction at room temperature. It is a curing agent to be performed. This latent curing agent includes imidazole, hydrazide, boron trifluoride-amine complexes, amine imides, polyamines, tertiary amines, alkyl ureas and other amines, dicyandiamides, acid and acid anhydrides. Agents, basic active hydrogenated compounds, and modified products thereof are exemplified, and these can be used alone or as a mixture of two or more.

  In particular, these latent curing agents coated with a polymer material such as polyurethane and polyester, a metal thin film such as nickel and copper, and an inorganic material such as calcium silicate, This is preferable because it is possible to achieve both contradictory properties of storage stability and fast curability. Therefore, a microcapsule type imidazole-based latent curing agent is particularly preferable.

  As the wiring electrode 7 of the present invention, for example, an ITO electrode formed on the circuit board 1 is used. The protruding electrode 8 is formed, for example, by forming a barrier metal (not shown) on the electronic component 6 and forming a photoresist (not shown) having a predetermined opening pattern on the barrier metal. Is used as a mask to plate gold (for example, electrolytic plating).

  The high frequency oscillator 4 may be any type of oscillator as long as it can generate a high frequency having a desired frequency, such as a microwave oscillator that generates a microwave having a predetermined frequency. A heating device can be used. Further, the frequency of the high frequency to be used can be appropriately selected in consideration of the type of the adherend member, the purpose of use, and the like. For example, when the electronic component 6 is mounted on the circuit board 1, a component in the range of 1 kHz to 1000 kHz can be used. For the coil 5, for example, a conductor such as stainless steel, titanium, or tungsten can be used.

  Here, the present invention is characterized in that the conductive material 2 of the adhesive 3 has a shape in which a large number of fine particles are connected in a straight chain or a needle shape. By setting it as such a structure, the surface area per unit volume of the electroconductive substance 2 can be enlarged compared with the electroconductive substance which has a substantially spherical shape. Therefore, since the conductive material 2 can be efficiently heated by induction heating using a high-frequency current, the adhesive 3 can be efficiently heated by the heat generated by the conductive material 2. In addition, since the conductive material 2 can be efficiently heated, the blending ratio of the conductive material 2 in the adhesive 3 can be reduced, and the blending ratio of the thermosetting resin in the adhesive 3 can be increased. Become. As a result, the connection reliability between the adherends (that is, between the wiring electrode 4 and the protruding electrode 5) is improved.

  In addition, since the conductive material 2 has a shape in which a large number of fine particles are connected in a straight chain or a needle shape and has an excellent cushioning property, the wiring electrode 7 and the protrusion as an adherend member are provided. When the electrode 8 is connected via the adhesive 3 having the conductive substance 2, the connection can be made without damaging the wiring electrode 7 and the protruding electrode 8.

  Note that the conductive material 2 used in the present invention preferably includes a ferromagnetic material in part, such as a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, and a metal having ferromagnetism. It is preferably any one of an alloy of a metal with another metal and a composite containing a metal having ferromagnetism. This is because by using a metal having ferromagnetism, it is possible to orient the conductive material 2 in a desired direction using a magnetic field due to the magnetism of the metal itself. For example, from the viewpoint of improvement in conductivity and availability, nickel, iron, cobalt, and two or more kinds of alloys connected in a straight chain can be used.

  Further, by passing the conductive material 2 through a magnetic field applied in the thickness direction of the adhesive 3 when the adhesive 3 is formed, the thickness direction (the direction of the magnetic field and the direction of the arrow X in FIG. It is preferable to be used after being oriented to the above. By adopting such an orientation, a short circuit is maintained while maintaining insulation between adjacent electrodes by a high conductive resistance in the surface direction of the adhesive 3 (the direction perpendicular to the thickness direction and in the direction of arrow Y in FIG. 2). It is possible to connect a large number of electrodes to each other at once, and to independently conduct conductive connection with each other by the low conductive resistance in the thickness direction of the adhesive 3.

  In addition, it is preferable to use a conductive material 2 having a shape with a large so-called aspect ratio. The aspect ratio here refers to the ratio of the short diameter of the conductive material 2 (the length of the cross section of the conductive material 2) to the long diameter (the length of the conductive material 2). More specifically, the conductive material 2 preferably has an aspect ratio of 10 or more. By using such a conductive substance 2, it becomes possible to heat the conductive substance 2 more efficiently by induction heating with a high frequency current.

  The aspect ratio of the conductive material 2 is directly measured by a method such as observation with a CCD microscope. In the case of the conductive material 2 whose cross section is not a circle, the aspect ratio is obtained by setting the maximum length of the cross section as the minor axis. Further, the conductive substance 2 does not necessarily have a straight shape, and can be used without any problems even if there is some bending or branching. In this case, the aspect ratio is obtained with the maximum length of the conductive material 2 as the major axis.

  In addition, this invention is not limited to the said embodiment, A various design change is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention.

  For example, in the above-described embodiment, the circuit board 1 on which the electronic component 6 is mounted is described as an example of the bonding structure, but the adhesive of the present invention is also preferably used for other members to be bonded. can do. For example, the present invention can be used for wooden and resin bonded members in the construction industry and metal bonded members in the metal processing industry such as the automobile industry. For example, it is good also as a structure which uses the electrode formed in each of a some flexible printed wiring board as a to-be-adhered member, and adhere | attaches the said electrode with the adhesive agent of this invention. In either case, the same effects as those of the above-described embodiment can be obtained.

  Moreover, in the said embodiment, although thermosetting resin was used as a resin component of the adhesive agent 3, thermoplastic resins, such as ethylene vinyl alcohol, an acrylic resin, a polyester resin, a urethane resin, an ethylene vinyl acetate polymer, are mentioned, for example. Can also be used as a resin component of the adhesive 3. In this case, when a high-frequency current having a predetermined frequency is supplied from the high-frequency power supply 9 of the high-frequency oscillator 4 to the coil 5 connected to the high-frequency power supply 9 to generate a high-frequency induction magnetic field, the conductive material 2 is vortexed. An electric current is generated, the conductive material 2 generates heat by the eddy current, the adhesive 3 is heated, and the adhesive 3 is heated and melted. Next, by releasing the heating state of the adhesive 3 and starting cooling, the adhesive 3 mainly composed of a thermoplastic resin is cured, and the wiring electrode 7 and the protruding electrode 8 are connected via the adhesive 3. Then, the electronic component 6 is mounted on the circuit board 1. Also in this case, the same effect as the above-described embodiment can be obtained.

  In the above embodiment, the metal coil 5 is arranged below the circuit board 1 on which the adhesive 3 is placed. However, the coil 5 is formed in a substantially circular shape or a substantially elliptical shape. In the coil 5, an adhesive structure in which the adhesive 3 is interposed between the circuit board 1 and the electronic component 6 may be disposed.

  As an application example of the present invention, for example, an adhesive for bonding a member to be bonded such as a substrate or an electronic component provided with an electrode, a circuit or the like by being heated by a high-frequency electromagnetic field can be cited.

It is sectional drawing which shows the adhesion structure joined by the adhesive agent which concerns on this invention, and is a figure which shows the state which is heating the adhesive agent by the high frequency oscillator. It is sectional drawing which shows the state which connected between electrodes with the adhesive agent which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Conductive substance, 3 ... Adhesive, 4 ... High frequency oscillator, 5 ... Coil, 6 ... Electronic component, 7 ... Wiring electrode (bonded member), 8 ... Projection electrode (bonded member), 9 ... High frequency power supply

Claims (6)

It contains a thermosetting resin and a conductive substance that generates heat by induction heating in a high-frequency heat treatment, and the heat-resistant resin is cured by the heat generation of the conductive substance, thereby bonding the members to be bonded together. In the adhesive
An adhesive characterized in that the conductive substance has a shape in which a large number of fine particles are connected in a straight chain or a needle shape.   The adhesive according to claim 1, wherein the conductive material has an aspect ratio of 10 or more.   The conductive material is any one of a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, an alloy of a metal having ferromagnetism and another metal, and a composite containing a metal having ferromagnetism. The adhesive according to claim 1 or 2, wherein the adhesive is provided.   The adhesive according to claim 3, wherein the conductive substance is any one of nickel, iron, cobalt, and two or more kinds of alloys thereof.   The adhesive according to any one of claims 1 to 4, wherein the conductive substance is oriented in a thickness direction of the adhesive.   The adhesive according to any one of claims 1 to 5, wherein the thermosetting resin is an epoxy resin and the conductive substance is dispersed in the epoxy resin.

Images