JP4019328B2 - Electrode connection method - Google Patents

Description

  The present invention relates to a method for connecting electrodes in which an electronic component and a circuit board or circuit boards are bonded and fixed, and the electrodes of both are electrically connected.

In recent years, with the miniaturization and thinning of electronic components, circuits used for these have become denser and higher definition. Since it is difficult to connect such electronic components and fine electrodes with conventional solders or rubber connectors, anisotropically conductive adhesives and membranes with excellent resolution (hereinafter referred to as connecting members) Is frequently used.
This connecting member is made of an adhesive containing a predetermined amount of a conductive material such as conductive particles, and this connecting member is provided between the electronic component and the electrode or circuit to form a pressurizing or heating / pressing means. As a result, the electrodes are electrically connected to each other, and the electrodes formed adjacent to the electrodes are provided with insulating properties so that the electronic component and the circuit are bonded and fixed.

The basic idea for increasing the resolution of the connecting member is to ensure the insulation between the adjacent electrodes by making the particle size of the conductive particles smaller than the insulating portion between the adjacent electrodes. The amount is set so that the particles do not come into contact with each other and is surely present on the electrode to obtain conductivity at the connection portion.
JP-A-9-55279 JP-A-5-174890 Japanese Unexamined Patent Publication No. 7-73922

In the above prior art, when the particle size of the conductive particles is reduced, the particles are secondary agglomerated and connected due to a significant increase in the surface area of the particles, and insulation between adjacent electrodes cannot be maintained. In addition, if the content of the conductive particles is reduced, the number of conductive particles on the electrodes to be connected also decreases, so the number of contact points is insufficient and conduction between the connection electrodes cannot be obtained. It is extremely difficult to increase the resolution of the connecting member.
In other words, due to the recent significant increase in resolution, that is, the electrode area and the miniaturization between adjacent electrodes (spaces), the conductive particles on the electrodes flow out between the adjacent electrodes together with the adhesive by the pressurization or heating and pressurization at the time of connection, This hinders high resolution of the connecting member.

As a measure for high resolution connection, an attempt is made to form and connect an insulating film on the peripheral wall portion of the protruding electrode (Japanese Patent Laid-Open No. 6-232221). However, since it is necessary to remove the insulating film on the counter electrode surface, it is photosensitive. Since the insulating film is removed by masking with resin or by dry etching, the process is complicated, which is not economical.
Furthermore, there is also a proposal of a connection member that can connect such fine electrodes and circuits and has a dense region of conductive particles in necessary portions in both directions as a connection member that is excellent in connection reliability. According to this, although a dot-shaped fine electrode such as a semiconductor chip can be connected, there is a disadvantage that the workability is inferior because a precise alignment between the conductive particle dense region and the dot-shaped electrode is necessary.

  The present invention has been made in view of the above-described drawbacks, and it is difficult for the conductive particles to flow out from the electrode at the time of connection. The present invention relates to a low-cost method for connecting a fine electrode that is excellent in workability because alignment is unnecessary and does not require removal of an insulating coating on a counter electrode surface.

The present invention is a method for insulatingly covering at least one electrode surface of electrodes facing each other and obtaining a connection between the electrodes with a connecting member, wherein at least one of the following steps includes a projecting electrode. It is a connection method, and also relates to an electrode connection method capable of adding a step of performing inspection and / or repair between electrodes in the step.
(1) A step of laminating a thermoplastic film having a thickness smaller than the particle diameter of the conductive material as an insulating layer on at least one electrode surface of the opposing electrodes (2) A thermoplastic film as an insulating layer on at least one electrode surface Step (3) of disposing a connecting member made of a conductive material having a particle size of 7 μm or less and 1 μm or more and a curable adhesive between pressure-deformable crosslinked particles as a core material, A step of aligning the electrodes facing each other and destroying the thermoplastic film on the electrode surface with a conductive material by pressing (4) A step of curing a connecting member between the pressed electrodes

  According to the present invention, it is difficult for the conductive material to flow out from the electrode when connected, it is possible to maintain the insulation between the adjacent electrodes, and it is excellent in workability because accurate alignment between the conductive particles and the electrode is unnecessary. It is possible to provide a low-cost connection method for fine electrodes.

The present invention will be described with reference to the drawings. 1 to 3 are schematic cross-sectional views of connecting portions for explaining an embodiment of the present invention. In the present invention, an insulating layer 4 is provided on at least one electrode surface 3 of the facing electrode 1-2 (FIGS. 1-2) and electrode 1-1 ′ (FIG. 3), and the conductive material 5 and the insulating adhesive are provided. The connection member 7 made of 6 is used for connection.
The insulating layer 4 may be formed on the entire surface of at least one of the protruding electrode 1 and the planar electrode 2 as shown in FIGS. 1-2, or may be provided on both of the counter electrodes as shown in FIG. The insulating layer 4 may be insulated only on the entire surface of the protruding electrode 1 (FIG. 3) or on the substrate surface 8 (FIGS. 1-2). In the case where the entire surface of the substrate surface and the electrode surface has the insulating layer 4, it is more preferable because the insulating treatment process is simple and the surface of the electrode can be protected.

  FIG. 4 shows the case where the insulating layer 4 is formed on a part of the side surface of the electrode including the electrode surface 3, and FIG. 5 shows the case where the insulating layer 4 is formed only on the electrode surface 3. These require a step of exposing a part of the electrode, but have an advantage of having a small number of insulation processing portions. In the case of FIG. 4, at least the insulating layer 1 may be formed on one side surface facing the adjacent protruding electrode 1-1 ′. 1 to 5 can be used in any combination.

In FIGS. 1 to 3, the insulating layers 4 and 4 ′ are present on the electrode surfaces facing each other, but the insulating layers 4 and 4 ′ are made of the conductive material 5 under electrode connection conditions, that is, pressurization or heating and pressurization. By being destroyed, it becomes possible to connect the electrodes facing each other.
The insulating layers 4, 4 ′ are not limited as long as they can be broken by the conductive material 5 at the time of connection, and can be any inorganic material such as silica, silicon nitride, metal oxide, or organic materials such as resins. . It is preferable that the thickness of the insulating layers 4 and 4 ′ be smaller than the particle diameter of the conductive material 5 because conduction between the electrodes by pressurization is easily obtained. In addition, since the conductive connection between the electrodes is easy, it is preferable that the insulating layers 4 and 4 ′ be softer than the conductive material 5 under the electrode connection condition, for example, an organic material such as a resin, especially a thermoplastic material.

  For the purpose of illustration and not limitation of the thermoplastic material, ethylene vinyl acetate copolymer, polyethylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, acrylic acid ester rubber, polyisobutylene, polyvinyl Examples include high molecular compounds and rubbers such as butyral, acrylonitrile-butadiene copolymer, styrene-butadiene block copolymer, polybutadiene, phenoxy resin, polyester resin, polyurethane resin, silicone rubber, polyimide, polyamide, and polychloroprene. it can. These can be used alone or in combination of two or more. These films can also contain various adjusting agents such as tackifiers, crosslinking agents, anti-aging agents, and interfacial force improvers.

When the electrodes are connected, the electrodes are aligned with each other, and the insulating layer on the electrode surface is broken with a conductive material by pressing or heating and pressing to obtain a connection between both electrodes. Depending on the type of the insulating adhesive 6, the connection member between the electrode arrays is cured as necessary.
The present invention can also incorporate a process for performing inspection and / or repair between electrodes in the connection process. That is, by dividing the heating and pressurizing step into two or more steps, it is possible to control the viscosity of the flow process associated with the curing reaction of the adhesive, and thus it is possible to achieve a good connection without bubbles. In addition, it is possible to impart repairability, which is a problem with curable adhesives. Repairability means removing unnecessary part of the adhesive, cleaning it with a solvent, and reconnecting it. In general, a curable adhesive has been regarded as a problem because a network structure develops after curing, becomes insoluble and infusible with heat, solvent, and the like, and is extremely difficult to clean.

  The first stage of the heating and pressing step is, for example, in a state in which the conductive material 5 having the pressure-deformable cross-linked particles as a core material is in contact with the protruding electrode 1 and can be electrically connected to the planar electrode 2. Conduct energization inspection and appearance inspection. At this time, if there is a connection portion of a defective electrode, repair and reconnection are performed in this state. Since the adhesive can be in an uncured state or an insufficient curing reaction state, the repair work is easy. In the energization inspection, for example, lead wires can be taken out from both electrodes and the connection resistance can be measured, and an appearance inspection such as observing the contact state between the conductive material 5 and the electrodes is also possible.

  The connecting member 7 is preferably made of the conductive material 5 having the pressure-deformable crosslinked particles as the core material and the insulating adhesive 6 and having conductivity in the pressurizing direction. The ratio of the conductive material 5 to the insulating adhesive 6 is preferably about 0.1 to 30% by volume, and more preferably 1 to 20% by volume because anisotropic conductivity is easily obtained. In the present invention, these can be added at a higher density than ordinary anisotropic conductive connecting members.

  Examples of the conductive material 5 include metal particles such as Au, Ag, Pt, Ni, Cu, W, Sb, Sn, and solder, carbon, and the like. These conductive particles are used as a core material or non-conductive glass. Alternatively, a core material made of a polymer such as ceramics or plastic may be coated with a conductive layer made of the above-described material. Furthermore, insulating coated particles obtained by coating the conductive material 5 with an insulating layer, and the combined use of conductive particles and insulating particles such as glass, ceramics, and plastics are preferable because the resolution is further improved. The conductive material 5 has a particle size of 1 or more, preferably 15 μm or less, more preferably 7 μm or less and 1 μm or more, in order to ensure the number of particles as small as possible on the minute electrode. . If it is 1 μm or less, it is difficult to break through the insulating layer and contact the electrode. It is preferable that the conductive material 5 exists as a single layer between the electrodes because the insulating layer is easily broken.

  In the present invention, among these conductive particles, those in which a conductive layer is formed on a polymer core material such as plastic are deformable by heating or pressurization or pressurization (FIG. 1), and the connection is in contact with the circuit. Since the area is increased and the reliability is improved, conductive particles having a pressure deformable crosslinked particle as a core material are used. Especially when polymers are used as the core, it does not show a melting point like solder, so the softening state can be widely controlled at the connection temperature, and it is possible to obtain a connection member that can easily cope with variations in electrode thickness and flatness. Is preferred.

  As the insulating adhesive 6, a thermoplastic material or a material that exhibits curability by heat or light can be widely applied. The thermoplastic material has good repair properties, and the curable material is excellent in heat resistance and moisture resistance after connection, and therefore is selected according to the application. The connection reliability is preferably applicable because curable materials are generally excellent. Among these, epoxy adhesives can be more preferably applied because of their characteristics such that they can be cured in a short time, have good connection workability, and have excellent adhesion in terms of molecular structure. Epoxy adhesives are mainly composed of epoxy modified with high molecular weight epoxy, solid epoxy and liquid epoxy, urethane, polyester, acrylic rubber, NBR, silicone, nylon, etc., curing agent, catalyst, coupling agent, filling A material obtained by adding an agent or the like is generally used.

  In the figure, examples of the substrate 9 include plastic films such as polyimide and polyester, composites such as glass epoxy, semiconductors such as silicone, inorganic materials such as glass and ceramics, and the like. In addition to the above, the protruding electrode 1 can also include various circuits and terminals. The planar electrode 2 refers to a case where there is no unevenness from the substrate surface or even a few μm or less. When these are illustrated, the electrodes obtained by the additive method and the thin film method are typical. These various electrodes and substrates can be applied in any combination.

According to the present invention, an insulating layer is formed on at least one electrode surface of electrodes facing each other and at least one of the electrodes protrudes, and the connection member made of a conductive material and an adhesive is pressed or heated and pressed to perform phase matching. Connect the opposite electrodes.
For this reason, the projecting electrode portions of the opposed electrode portions are intensively pressed, so that the insulating layer on the electrode surface is broken by the conductive material, so that both electrodes can be connected. On the other hand, other than the protruding electrode part, there is no applied pressure, or even a small amount, so the insulating layer is not broken by the conductive material, and high insulation is obtained even when the distance between adjacent electrodes is narrow, and high-resolution connection is achieved. It becomes possible. At this time, since the conductive material is held by the broken insulating layer on the electrode, there is little outflow from the electrode, and high connection reliability is obtained. For example, even when the conductive material flows out from the electrode at the time of connection, the insulating property can be maintained because the insulating layer is formed on any of the adjacent electrodes.

In addition, according to the present invention, since the conductive material is reliably held on the electrode and becomes conductive, the reliability of continuity inspection and connection is improved. Since the adhesive can be inspected for continuity in an uncured state or in a state where the curing reaction is insufficient, repair work is easy.
The insulating layer on the electrode surface can be formed on the entire surface, and removal of a partial insulating layer is not necessary in principle, so that a low-cost fine electrode can be connected. Since the conductive material of the connection member is uniformly dispersed over the entire surface, it is excellent in workability because accurate alignment between the conductive particles and the electrodes is unnecessary.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
Example 1
(1) Connection A two-layer FPC circuit board (circuit pitch is 70 μm, electrode of a parallel circuit with an electrode width of 20 μm) having a copper circuit with a height of 18 μm was prepared on a polyimide film. A 3 μm thick phenoxy resin film (thermoplastic epoxy resin, softening point: 120 ° C.) was pressure-bonded at 180 ° C. by laminating on the circuit forming surface to form an insulating layer. Since it was a thermoplastic resin, it was softened and melted, and an insulating layer could be formed along the circuit pitch. For the connecting member, the ratio of the liquid epoxy resin containing the phenoxy resin and the microcapsule type latent curing agent was 20/80, and a 30% solution of ethyl acetate was obtained. To this solution, 5% by volume of conductive particles in which a 0.2 / 0.02 μm thick Ni / Au metal coating is added to styrene-divinylbenzene-based crosslinked particles having a particle size of 6 ± 0.2 μm are added and mixed and dispersed. did. This dispersion was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 110 ° C. for 20 minutes to obtain a connecting member having a thickness of 20 μm. Connection to a planar electrode having a thin film circuit with an indium oxide thickness of 0.2 μm (ITO, surface resistance 20Ω / □) on 0.7 mm of glass was performed. First, the connecting member was placed on the flat electrode side with a width of 2 mm, and was temporarily bonded to separate the separator. Subsequently, alignment between the electrodes facing the FPC circuit was performed, and the connection members were connected at 150 ° C., 30 kgf / mm ² and 20 seconds under conditions where the curing reaction was sufficient.

(2) Evaluation When the cross section of this connection body was polished and observed with a microscope, it was a connection structure corresponding to FIG. Phenoxy, which is an insulating layer on the electrode surface, was able to be destroyed with a conductive material by pressurization. The space between adjacent electrodes was free of bubbles and particles were spherical, but on the electrodes, the particles dig into the insulating layer and were compressed and deformed and held in contact with the upper and lower electrodes. Since it is a crosslinked particle, it seems that the hardness under the connecting condition temperature and the deformability by pressurization were obtained together. When the resistance between the electrodes facing each other was evaluated as the connection resistance and the insulation resistance between the adjacent electrodes was evaluated, the connection resistance was 1Ω or less and the insulation resistance was 10 ⁸ Ω or more. These were treated at 85 ° C. and 85% RH for 1000 hours. There was almost no change, and good long-term reliability was exhibited. The effective average number of particles contributing to the connection on the electrode (20 μm × 2 mm) in the present example is 50 (maximum 55, minimum 46), and a large number of conductive particles are secured on the electrode, and the variation There are few. The effective particles contributing to the connection are those in which the connection surface is observed with a microscope (× 100) from the glass side and gloss is generated by contact with the electrode.

Comparative Example 1
The same FPC circuit as that of Example 1 but without forming an insulating layer was used. When evaluated in the same manner as in Example 1, the number of particles on the electrode (20 μm × 2 mm) was 38 at the maximum and 0 at the minimum, and there was no effective particle on the electrode. And the smallest variation was large. Further, when the insulation resistance of the connection body was measured, a short circuit defect occurred. It seems that the conductive particles flowed out from the electrodes at the time of connection, and the insulation between adjacent electrodes (space portions) cannot be maintained.

Reference example 1
Similar to Example 1, but instead of FPC, there are 200 IC chips (2 × 10 mm, height 0.5 mm, 4 side 50 μm square, 20 μm height called bumps (projection electrodes) around 4 sides. Formation) was used. In this IC chip, a polyimide-based (glass transition point 170 ° C.) solution is formed on the protruding electrode formation surface at the wafer stage by a spin coater, and then the solvent is dried to form an insulating layer having a thickness of 2 μm on the electrode. is there. The ITO electrode on the glass side was changed to correspond to the bump electrode size of the IC chip. The connection was made in the same manner using the connection member of Example 1. The connection body has a configuration corresponding to FIG. 2 (the conductive material is FIG. 1). This example also showed good connection characteristics.

Example 2
The FPCs of Example 1 were similarly connected to obtain a connection body corresponding to FIG. 3 (the conductive material is FIG. 1). When evaluated in the same manner as in Example 1, good connection characteristics were shown. This configuration is a connection between the protruding electrodes, each formed with an insulating layer, but the number of effective particles on the electrodes is such that particles easily flow out due to the connection between the protruding electrodes. did it.

Reference Examples 2-3
Although it is the same as that of the reference example 1, it changed into the board | substrate which can mount five IC chips on a glass substrate, and made the heating-pressing process into two steps. First, the connection resistance at each connection point was measured and inspected with a multimeter while applying pressure at 150 ° C., 30 kgf / mm ² after 2 seconds (Reference Example 2). Similar but the other was removed from the connection device after 150 seconds at 150 ° C., 30 kgf / mm ² . Since the cohesive strength of the adhesive was improved by heating and pressing, each IC chip was temporarily fixed on the glass side and was not pressurized, and was similarly examined (Reference Example 3). In both reference examples, one IC chip was abnormal. Then, when the abnormal chip was peeled off and the same connection as described above was performed with a new chip, both were good this time. Since the adhesive is in a state where the curing reaction is insufficient, the chip peeling and the subsequent cleaning with acetone are very simple, and the repair work is easy.
After the above energization inspection process and repair process, when connected at 150 ° C., 30 kgf / mm ² for 20 seconds, both reference examples showed good connection characteristics. The number of effective particles on the bumps could be secured to 7 or more for all electrodes. In this reference example, the number of effective particles on the bumps is increased and the outflow from the electrodes is less than in Reference Example 1. It is considered that the retention property of the particles is further improved by making the heating and pressing step into two stages.

It is a cross-sectional schematic diagram of the connection structure of the electrode which shows Example 1 of this invention. It is a cross-sectional schematic diagram of the connection structure of the electrode which shows the reference example 1 of this invention. It is a cross-sectional schematic diagram of the connection structure of the electrode which shows Example 2 of this invention. It is a cross-sectional schematic diagram of the electrode which shows the reference example 2 of this invention. It is a cross-sectional schematic diagram of the electrode which shows the reference example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Protruding electrode 2 Planar electrode 3 Electrode surface 4 Insulating layer 5 Conductive material 6 Insulating adhesive 7 Connection member 8 Substrate surface 9 Substrate 10 Substrate

Claims (2)

A method of connecting at least one electrode surface of electrodes facing each other with insulation covering and obtaining a connection between the electrodes with a connecting member, wherein at least one of the following steps comprises a projecting electrode (1) Step (2) of laminating a thermoplastic film having a thickness smaller than the particle diameter of the conductive material as an insulating layer on at least one electrode surface of the opposing electrodes (2) A thermoplastic film as an insulating layer is laminated on at least one electrode surface Step (3) of placing a connecting member made of a conductive material having a particle size of 7 μm or less and 1 μm or more and a curable adhesive between the electrodes that are pressed against each other and having a pressure-deformable crosslinked particle as a core material A step of aligning the electrodes and breaking the thermoplastic film on the electrode surface with a conductive material by pressing (4) A step of curing the connecting member between the pressed electrodes A method of connecting at least one electrode surface of electrodes facing each other with insulation covering and obtaining a connection between the electrodes with a connecting member, wherein at least one of the following steps comprises a projecting electrode (1) Step (2) of laminating a thermoplastic film having a thickness smaller than the particle diameter of the conductive material as an insulating layer on at least one electrode surface of the opposing electrodes (2) A thermoplastic film as an insulating layer is laminated on at least one electrode surface Step (3) of placing a connecting member made of a conductive material having a particle diameter of 7 μm or less and 1 μm or more and a curable adhesive between pressure-deformable crosslinked particles as a core material between the opposing electrodes (3) A step of aligning the electrodes and destroying the thermoplastic film on the electrode surface with a conductive material by pressurization (4) A step of inspecting and / or repairing between the electrodes (5) Electricity The process of curing the connecting member between the electrodes

Images