JP2009111043A - Electric connection body, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric connection body, wherein conductive particles contained in an anisotropic conductive film can be uniformly crushed even when the sizes of conductive particles are small, and excellent conduction characteristics can be obtained. <P>SOLUTION: The electric connection body is constituted by electrically connecting a semiconductor element 1 as a first electronic member and a wiring board 3 as a second electronic member through the anisotropic conductive film 5. Bumps (projection electrode) 2 are formed on one of the electronic members (the semiconductor element 1 in this case), and a top portion of each bump 2 is formed to have a flat surface having a surface roughness Ra of ≤0.05 μm. An average particle size of conductive particles 6 contained in the anisotropic conductive film 5 is ≤4 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrical connection body in which electronic members such as a semiconductor element and an electronic substrate are electrically connected to each other, and in particular, electrical connection is performed using a protruding electrode (bump) and an anisotropic conductive film. Related to the electrical connection.

  2. Description of the Related Art Conventionally, when an electronic member such as a semiconductor element is mounted on a wiring board, for example, the terminal electrode of the semiconductor element and the electrode of the wiring board are electrically connected by wire bonding. However, in this type of wire bonding, the electrodes must be connected to each other with bonding wires, and the connection process is complicated, and the terminal electrodes are miniaturized and the pitch is reduced due to high-density mounting. There is a problem that it is difficult to cope with the problem, and the improvement is desired.

  Under such circumstances, a flip chip mounting method has been proposed in which a semiconductor element is mounted on a wiring board in a so-called face-down state. In this flip chip mounting method, a bump electrode called a bump is formed on one of a terminal electrode of a semiconductor element or an electrode of a wiring board, and the bump electrode is disposed so as to face the other electrode. This is a method of electrical connection in a lump. The protruding electrode is formed by plating Au, Cu, solder or the like, and its height is about several μm to several tens of μm.

  In such a flip chip mounting method, an anisotropic conductive film is used for the purpose of improving connection reliability. An anisotropic conductive film is a conductive particle dispersed in an insulating resin that functions as an adhesive. When this is sandwiched between electrodes facing a protruding electrode, and heated and pressurized, the conductive particle is an electrode. They are crushed between them to make an electrical connection. In the portion without the protruding electrode, the conductive particles are maintained dispersed in the insulating resin and kept in an electrically insulated state, so that electrical conduction is achieved only in the portion with the protruding electrode. It will be.

  According to the flip chip mounting method using an anisotropic conductive film, as described above, a large number of electrodes can be electrically connected together, and one electrode can be connected as in wire bonding. It is not necessary to connect with one bonding wire, and it is relatively easy to cope with the miniaturization of terminal electrodes and the narrow pitch associated with high-density mounting.

  In the flip chip mounting method using such an anisotropic conductive film, it is necessary to improve the trapping property of the conductive particles on the protruding electrode in order to ensure the reliability of the electrical connection. Is underway. For example, when the height of the protruding electrode is not uniform, a problem occurs in connection. Therefore, a technique for making the height of the protruding electrode uniform has been proposed (see, for example, Patent Document 1 to Patent Document 6).

  Specifically, Patent Document 1 discloses a method of mounting a semiconductor element having an electrode portion on a substrate having an electrode pattern. In particular, in this mounting method, a conductive protrusion that protrudes from the surface of the semiconductor element is provided on the electrode portion of the semiconductor element, and the protrusion is temporarily pressed against the surface of the rigid body, and the adhesive resin is applied to at least one of the substrate and the semiconductor element. The semiconductor element and the substrate are pressed and bonded so that the protrusion and the electrode pattern are in contact with each other, and then the adhesive resin is cured.

  Patent Document 2 discloses a method of forming bumps used for bonding with electrodes of a semiconductor element on a large number of electric circuits formed on the surface of a substrate, and the bumps have a uniform height by pressurization. A method for producing a bump characterized by the above is disclosed.

  Further, Patent Document 3 is characterized in that at least a bump forming surface of a ceramic circuit board having a through hole filled with a conductor is polished, and a metal piece is brazed onto the through hole conductor exposed on the surface. A method of manufacturing a bumped substrate is disclosed.

  Further, Patent Document 4 is mounted by face-down bonding on a lead surface having a structure in which a silver plating layer is provided as a lower layer, a nickel plating layer is provided as an upper layer, and a gold plating layer is further provided as an upper layer. A columnar protruding electrode is formed by gold plating on a portion facing the electrode pad of the semiconductor device, and the protruding electrode is pressed by a flat plate from above the semiconductor device mounting substrate, and a contact surface with the electrode pad of the semiconductor device A technique for flattening the surfaces of a plurality of protruding electrodes so as to coincide with each other in the same plane is disclosed.

  Further, in Patent Document 5, contact is made with a solder bump electrode for the purpose of reducing mounting defects by aligning the height of the solder bump electrode, reducing electrical connection resistance and improving connection strength. Discloses a technique of polishing at least a top portion of a solder bump electrode after performing an electrical property test.

  Further, in Patent Document 6, for the purpose of efficiently aligning the height of the bump, the imaging means focuses on the top of the bump, and the position of the cutting means at that time is the origin, and the cutting is performed with the origin as a reference. A technique for cutting a bump by driving means is disclosed.

  In addition to the techniques described in Patent Documents 1 to 6, it is also attempted to form irregularities on the protruding electrode in order to improve the trapping property of the conductive particles between the protruding electrode and the connection terminal. (For example, see Patent Document 7 to Patent Document 10).

  For example, Patent Document 7 discloses a liquid crystal display device in which an electrode of a liquid crystal cell and an electrode of a flexible substrate are connected, and the electrode of the flexible substrate has a roughened surface. It is disclosed.

  Further, in Patent Document 8, a semiconductor device (IC substrate) is placed face down on a flat base including a polishing sheet having abrasive grains so that bumps come into contact with the polishing sheet. It is disclosed that an uneven surface is formed on the front end surface of a bump by ultrasonically vibrating the flat base in a plane perpendicular to the pressing direction while pressing the base.

  Further, Patent Document 9 discloses a step of forming a gold bump on an electrode of a semiconductor device, a step of attaching an anisotropic conductive film on a circuit board, and an anisotropic conductive film made of a material harder than the gold bump. Forming a concavo-convex portion on the front end surface of the gold bump by pressing a pressing substrate having a concavo-convex smaller than the diameter of the conductive particles on the front end surface of the gold bump of the semiconductor device; A method of mounting a semiconductor device is disclosed, which includes a step of pressing and heating a semiconductor device against a circuit substrate on which an anisotropic conductive film is attached after aligning the electrodes of the substrate.

  Furthermore, in Patent Document 10, when the bump electrode is formed, a plurality of conical or trapezoidal convex portions made of a passivation film are provided on the wiring electrode in advance, and a bump base metal layer is deposited in this state, Discloses a technique for forming a gold electrode by plating growth to form a bump electrode. As a result, an uneven portion corresponding to the uneven portion provided on the wiring electrode is formed on the electrode surface of the bump electrode.

Japanese Patent Laid-Open No. 1-278034 JP-A-1-295433 JP-A-4-33395 Japanese Patent Laid-Open No. 5-291262 JP 2000-114313 A JP 2006-324397 A Japanese Utility Model Publication No. 63-174328 JP-A-6-283537 Japanese Patent Laid-Open No. 11-16946 JP 2004-14778 A

  By the way, in the anisotropic conductive film used for the flip chip mounting described above, the particle size of the conductive particles is usually in the range of 5 μm to 10 μm. It is required to reduce the proportion of particles or to reduce the particle size of conductive particles. For example, when the proportion of conductive particles is large and the particle size of the conductive particles is large, the conductive particles are clogged between the protruding electrodes in a fine pitch flip chip mounting, and an electrical short circuit occurs. The problem arises.

  In this case, reducing the proportion of the conductive particles is directly related to the trapping property of the conductive particles, so it is appropriate to reduce the particle size of the conductive particles. If the particle size of the conductive particles is reduced, the conductive particles in the gaps between the protruding electrodes are dispersed in the insulating resin (adhesive), and the conductive particles are in contact with each other between the protruding electrodes. The short-circuit problem due to is avoided.

  However, when the particle size of the conductive particles is reduced, the conductive particles are not crushed uniformly due to variations in the height of the protruding electrodes, mounting accuracy, etc. A new problem arises. The surface height of each protruding electrode has a variation of about ± 2 μm (the surface roughness Ra of the conventional protruding electrode is about 0.3 μm). For example, when the average particle diameter of the conductive particles is 4 μm or less, It is difficult to crush uniformly.

  When considering such a reduction in the diameter of the conductive particles, a technique for making the heights of the protruding electrodes uniform, such as the techniques described in Patent Documents 1 to 6 described above, cannot cope. In the techniques described in Patent Document 1 to Patent Document 6, although the variation in height between the protruding electrodes can be reduced, the height due to the surface roughness of the protruding electrode top portion (tip flat portion) is reduced. The variation cannot be eliminated, and the variation due to the surface roughness exists at the top of the protruding electrode. Therefore, the problem that the conductive particles on the protruding electrodes are not uniformly crushed when the particle diameter of the conductive particles is reduced remains unsolved.

  On the other hand, in the technique of forming irregularities on the protruding electrode in order to improve the trapping property of the conductive particles like the techniques described in Patent Documents 7 to 10, the surface roughness of the protruding electrode is increased. In this case, since the trapped conductive particles enter the irregularities, they cannot be uniformly crushed, and it is difficult to cope with the reduction in the diameter of the conductive particles.

  Moreover, when mounting a semiconductor element etc., it is normal to perform an annealing process for the purpose of adjusting so that the hardness of a protruding electrode may become uniform. However, even if the surface roughness of the protruding electrode can be reduced by performing a process such as cutting on the top, there is a problem that the surface roughness is greatly increased by performing the annealing process.

  The present invention has been made in view of such circumstances, and even when the particle size of the conductive particles contained in the anisotropic conductive film is small, it is possible to uniformly crush it. It is an object of the present invention to provide an electrical connection body capable of obtaining good conduction characteristics regardless of whether or not annealing is performed, and a method for manufacturing the electrical connection body.

  The inventor of the present application has made extensive studies over a long period of time in order to achieve the above-described object. As a result, when unevenness is formed on the surface of the protruding electrode, the trapping property of the conductive particles may be improved. However, sufficient pressure is transmitted to the conductive particles in the portion located around the protruding electrode by the unevenness. Therefore, when the conductive particles on the protruding electrode are not uniformly crushed, and conversely, the surface of the protruding electrode is exceptionally smooth, so that the conductive particles that act effectively when crushed are small. As a result, the number of slag increased, and it was found that there was almost no problem with the trapping property.

  The present invention has been completed based on such findings. That is, the electrical connection body according to the present invention that achieves the above-described object is an electrical connection body in which the first electronic member and the second electronic member are electrically connected via an anisotropic conductive film. A bump electrode is formed on any one of the electronic members, and the top of the bump electrode is a flat surface having a surface roughness Ra of 0.05 μm or less after annealing. It is said.

  Further, in the method of manufacturing the electrical connection body according to the present invention that achieves the above-described object, the surface roughness Ra of the top portion is set to 0. 0 by plating on either one of the first electronic member and the second electronic member. A step of forming a protruding electrode having a flat surface of 05 μm or less, a step of interposing an anisotropic conductive film between the first electronic member and the second electronic member, and the protruding electrode by pressing And crushing conductive particles of the opposite anisotropic conductive film to electrically connect the first electronic member and the second electronic member.

  When an anisotropic conductive film in which conductive particles having a small particle diameter are dispersed is used, if the surface roughness Ra of the protruding electrode is large and the surface is uneven, the first electronic member and the second electronic member When an anisotropic conductive film is sandwiched between the electronic member and the anisotropic conductive film is pressed between the electrodes facing the protruding electrode, conductive particles that have entered, for example, a recess on the surface of the protruding electrode The pressure is not sufficiently transmitted to and does not collapse sufficiently. If the conductive particles are not sufficiently crushed, the electrical contact area is insufficient, and it is difficult to ensure conduction reliability.

  On the other hand, in the present invention, the surface roughness Ra of the protruding electrode is set to 0.05 μm or less and is in an extremely smooth state. In particular, in the present invention, the surface roughness Ra is set to 0.05 μm or less even after the annealing treatment, and the top of the protruding electrode can be maintained in an extremely smooth state regardless of whether or not the annealing treatment is performed. . Therefore, even when the particle size of the conductive particles is small, pressure is uniformly applied to each conductive particle, and uniform particle deformation is realized.

  According to the present invention, even when the particle size of the conductive particles contained in the anisotropic conductive film is small, it can be uniformly crushed and good conduction characteristics can be obtained. Therefore, according to this invention, it is possible to provide the electrical connection body excellent in conduction | electrical_connection reliability.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the present specification, bumps and bump electrodes are treated as synonymous.

  FIG. 1 shows an example of an electrical connection body. The electrical connection body is obtained by electrically and mechanically connecting and fixing an electronic member such as a semiconductor element to an electronic member such as a wiring board. Here, a case where the first electronic member is a semiconductor element (IC chip) and the second electronic member is a wiring board will be described as an example.

  In FIG. 1, a bump (projection electrode) 2 is formed as a connection terminal on a semiconductor element 1 which is a first electronic member. On the other hand, an electrode 4 is formed at a position facing the bump 2 on the wiring board 3 as the second electronic member. An anisotropic conductive film 5 is interposed between the semiconductor element 1 and the wiring substrate 3, and the conductive particles 6 included in the anisotropic conductive film 5 are present at the portion where the bump 2 and the electrode 4 face each other. It is crushed to achieve electrical continuity.

  The bump 2 is formed of a conductive metal such as Au, Cu, or solder, for example, and its height is about 5 μm to 50 μm. The bump 2 can be formed by plating or the like. For example, only the surface can be gold-plated. As will be described later, the bump 2 is required to have surface smoothness, and from this point of view, it is preferable to use gold plating.

  In the electrical connection body having such a structure, the surface roughness of the bumps 2 formed on the semiconductor element 1 is important. When the surface roughness of the bump 2 is large, for example, as schematically shown in FIG. 2, a part of the conductive particles 6 enters the concave portion 2a of the connection surface of the bump 2, and no pressure is applied even when pressed. A phenomenon in which the conductive resistance becomes unstable due to the unsmashed state is likely to occur. On the other hand, if the connection surface of the bump 2 is flat, all the conductive particles 6 captured between the bump 2 and the electrode 4 are uniformly crushed, and the conduction reliability is stably secured. .

  From such a viewpoint, in the present invention, the surface roughness of the bump 2 is set to 0.05 μm or less in terms of the center line average roughness Ra. In the electrical connection body, by setting the surface roughness Ra to 0.05 μm or less, uniform particle deformation is realized even when the average particle diameter of the conductive particles 6 is 4 μm or less, for example. It becomes possible to do. Note that the surface roughness Ra of the bump 2 is preferably set in consideration of the average particle diameter of the conductive particles 6, and particularly preferably 0.02 μm or less.

  The surface roughness Ra of the bump 2 can be measured by using a contact-type measuring instrument such as a surface profiler manufactured by Tencor.

  Here, in the electrical connection body, when the annealing process is performed in a later step, even if the surface roughness Ra before the annealing process can be formed to 0.05 μm or less, the annealing process is performed after the annealing process. Usually, the surface roughness Ra is greatly increased. On the other hand, in the electrical connection body according to the present invention, the surface roughness Ra is more preferably 0.05 μm or less before and after the annealing process by controlling the crystal state of the plating when the bump 2 is formed. Can be kept below 0.02 μm.

  In addition to the surface roughness Ra, the bump 2 is preferably set appropriately for its hardness. The hardness of the bumps 2 can be designed according to the type of conductive material used for the bumps 2 and, for example, the formation conditions when plating is formed, but uniform particle deformation of the conductive particles 6 is realized. In order to achieve this, the Vickers hardness Hv is preferably 40 to 150. In the electrical connection body, by setting the Vickers hardness Hv of the bump 2 within the range of this value, when the conductive particles 6 are crushed, the applied pressure is properly transmitted to the conductive particles 6 and uniformly. It can be crushed.

  On the other hand, in the electrical connection body, the anisotropic conductive film 5 used for electrical connection and mechanical fixation between the bump 2 and the electrode 4 has conductive particles 6 dispersed in an insulating resin. Is. As the insulating resin, for example, a thermoplastic hot melt resin such as a urethane resin, a polyester resin, or chloroprene, a thermosetting resin such as an epoxy resin, or the like can be used. Examples of the epoxy resin include BPA type epoxy resin, BPF type epoxy resin, novolac type epoxy resin, various modified epoxy resins such as rubber and urethane, etc. Even if these are used alone, two or more types are mixed. May be used.

  Further, a latent curing agent may be added to the anisotropic conductive film 5 and heated to activate the curing agent. By adding a latent curing agent to the anisotropic conductive film 5, it is possible to impart initiation reactivity, and it is possible to reliably and quickly cure by a heating operation at the time of connection. In this case, as the latent curing agent, an imidazole-based latent curing agent or the like can be used. A trade name) Amicure PN-23 (manufactured by Ajinomoto Co., Inc.), and a trade name ACR Hardener H-3615 (manufactured by ACR).

If the viscosity of the insulating resin contained in the anisotropic conductive film 5 is high, the insulating resin cannot be sufficiently removed from between the electrodes to be conducted, and the conduction reliability may be reduced. Moreover, when the viscosity of the insulating resin contained in the anisotropic conductive film 5 becomes high, it is necessary to increase the press pressure at the time of thermosetting in order to sufficiently exclude the insulating resin between the electrodes to be connected. Further, the contact of the conductive particles 6 with the bumps 2 and the electrodes 4 becomes strong, and there is a possibility that cracks and the like are generated. Therefore, the insulating resin preferably has a melt viscosity at the thermocompression bonding temperature of the anisotropic conductive film 5 of 10 ⁸ mPa · s or less, and more preferably 10 ⁷ mPa · s or less.

  On the other hand, if the melt viscosity at the time of thermocompression bonding of the insulating resin is too low, the electrodes to which the conductive particles 6 are to be conducted can easily escape, which may cause a problem in terms of trapping properties. Therefore, the insulating resin preferably has a melt viscosity of 10 mPa · s or more at the thermocompression bonding temperature of the anisotropic conductive film 5.

  As the conductive particles 6 constituting the anisotropic conductive film 5, any known conductive particles used in this kind of anisotropic conductive film can be used. For example, nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold and other metals and metal alloy particles, metal oxides, carbon, graphite, glass, ceramics, plastics and other metal particles Or those obtained by further coating the surface of these particles with an insulating thin film.

However, in the electrical connection body according to the present invention, it is necessary that the conductive particles 6 be crushed between the electrodes, and therefore, the resin particles whose surface is coated with metal are suitable. In this case, as the resin particles, compressive hardness at 20% compression ^deformation, it is preferable to use those ^{100~1000kgf / mm 2 (1kgf / mm} 2 = 9.80665MPa). If the K value at 20% compression deformation of the resin particles is larger than 1000 kgf / mm ² , the resin particles are not properly crushed, so that variations in the height of the electrode surface cannot be absorbed. In addition, a high pressure is required, and the repulsive force of the conductive particles 6 may increase, causing inconveniences such as interfacial peeling.

  Examples of the resin particles that satisfy such requirements include particles of epoxy resin, phenol resin, acrylic resin, acrylonitrile / styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, styrene resin, and the like.

  The average particle diameter of the conductive particles 6 is arbitrary, but the effect of the present invention is great when the conductive particles 6 having an average particle diameter of 4 μm or less are used. Therefore, the average particle diameter of the conductive particles 6 is preferably 1 μm to 4 μm. Further, as the top of the protruding electrode is flattened, the variation in the particle diameter of the conductive particles may be affected depending on the hardness of the conductive particles. In the case of the present invention, it is preferable that 90% or more of all particles are contained in the range of ± 1 μm of the average particle diameter of the conductive particles.

  In the electrical connection body having the above configuration, even when the particle diameter of the conductive particles 6 included in the anisotropic conductive film 5 is as small as 4 μm or less, it can be uniformly crushed. Yes, it is possible to obtain good conduction characteristics. Therefore, an electrical connection body excellent in conduction reliability can be realized.

  Next, a method for manufacturing the above-described electrical connection body will be described. In order to produce the electrical connection body having the above-described configuration, first, it is necessary to form bumps 2 on the electrodes of the semiconductor element 1. The bump 2 is formed by a method such as plating. In order to set the surface roughness Ra before and after the annealing treatment to 0.05 μm, it is preferable to use gold plating, and by selecting the plating conditions, It is necessary to make the surface of the bump 2 to be smoothed.

  Here, in gold plating, the following gold plating solution is used in order to control the crystal state and smooth the surface of the bump 2 to be formed.

Gold plating solution
a) Gold compound b) Conductive salt / buffer c) Crystal growth agent d) Organic brightener and the like as a basic composition. Examples of the gold compound include gold sulfite and gold cyanide. Conductive salts / buffering agents include sulfites, phosphates, citrates, oxalates, sulfates, borates, hydrochlorides, amine salts, chelating agents, and the like. Further, examples of the crystal growth agent include Tl, Pb, As, Bi, Co, Ni, Fe, and Sb. Furthermore, as the organic brightener, there are polymers having NH groups, that is, ethoxylated polyethyleneimine (PEIE), polyalkylimine (PAI), polyethyleneimine (PEI) and the like. The gold plating obtained from these liquid compositions has a dense deposit and gloss, and is extremely suitable for applications in which the surface of the bump 2 formed in the present invention is smooth.

  After the formation of the bump 2, the connection between the bump 2 of the semiconductor element 1 and the electrode 4 of the wiring board 3 is performed. In this case, for example, an anisotropic conductive film 5 is pasted on the surface of the wiring board 3. After the alignment and temporary connection, the conductive particles 6 are crushed by thermocompression bonding at a predetermined temperature and pressure, and the bumps 2 of the semiconductor element 1 and the electrodes 4 of the wiring board 3 are electrically connected. The insulating resin constituting the anisotropic conductive film 5 is cured in the connected state. Although the temperature and pressure at the time of thermocompression bonding vary depending on the type of the anisotropic conductive film 5 to be used, for example, the temperature is preferably 180 ° C. to 220 ° C. and the pressure is preferably 30 MPa to 120 MPa.

  By passing through the above process, even if the particle diameter of the conductive particles 6 contained in the anisotropic conductive film 5 is small, it is possible to uniformly crush the conductive particles 6 to be produced. Thus, it is possible to obtain good conduction characteristics.

[Example]
Next, specific implementation of the electrical connection body to which the present invention is applied will be described based on experimental results.

Example 1
In order to evaluate the trapping property and crushing state of the conductive particles due to the difference in the surface roughness Ra of the bump, the IC with the bump was mounted on glass through an anisotropic conductive film. The anisotropic conductive film was formed by blending conductive particles into the binder component so as to be about 3 million particles / mm ³ and forming this into a film. The breakdown of each component is as follows.
Epoxy resin: Japan Epoxy Resin, trade name EP828 30 parts by weight Phenoxy resin: InChem, trade name PKHH 40 parts by weight Epoxy curing agent: Asahi Kasei Corporation, trade name HX3941HP 30 parts by weight Conductive particles: Ni / Au plating Resin Particles In addition, conductive particles having an average particle diameter of 4 μm and conductive particles having an average particle diameter of 2 μm are used as the conductive particles, and two types of anisotropic conductive films (an anisotropic conductive film A and an anisotropic conductive film B) are used. ) Was produced.

The bump of the bumped IC was formed by gold plating. This gold plating was performed under the conditions of a plating temperature of 50 ° C. and a current density of 0.4 A / dm ² using a product name Microfab Au310 manufactured by Nippon Electroplating Engineering Co., Ltd. as a gold plating solution. As a result, the surface roughness Ra of the connection surface of the bump obtained was 0.0105 μm. The pressure bonding conditions at the time of mounting were an ultimate temperature of 200 ° C., a pressure of 40 MPa, and a time of 5 seconds.

(Example 2)
A bumped IC was manufactured by changing the gold plating solution and plating conditions of Example 1. Gold plating was performed under the conditions of a plating temperature of 65 ° C. and a current density of 0.5 A / dm ² using a product name Neutronex 240 manufactured by Nippon Electroplating Engineers Co., Ltd. as a gold plating solution. The surface roughness Ra of the connection surface of the bump obtained as a result was 0.004 μm. The other conditions were the same as in Example 1, and the bumped IC was mounted on glass via an anisotropic conductive film.

(Comparative Example 1)
A bumped IC was manufactured by changing the gold plating solution and plating conditions of Example 1 and Example 2. Gold plating was performed under the conditions of a plating temperature of 60 ° C. and a current density of 0.5 A / dm ² using a trade name Microfab Au100 manufactured by Nippon Electroplating Engineering Co., Ltd. as a gold plating solution. As a result, the surface roughness Ra of the connection surface of the obtained bump was 0.298 μm. The other conditions were the same as in Example 1, and the bumped IC was mounted on glass via an anisotropic conductive film.

(Comparative Example 2)
ICs with bumps were produced by changing the gold plating solutions and plating conditions of Examples 1 and 2 and Comparative Example 1. Gold plating was performed under the conditions of a plating temperature of 60 ° C. and a current density of 0.8 A / dm ² using a product name Microfab Au660 manufactured by Nippon Electroplating Engineering Co., Ltd. as a gold plating solution. As a result, the surface roughness Ra of the connection surface of the bump obtained was 0.130 μm. The other conditions were the same as in Example 1, and the bumped IC was mounted on glass via an anisotropic conductive film.

For the anisotropic conductive films A and B prepared as evaluation examples and comparative examples, the conductive particles captured on the bumps are observed from the back of the glass using an optical microscope, and the number of captured particles is counted. The total number of trapped particles was determined, and the number of particles having passed the collapsed state was counted to determine the number of trapped effective particles (range 2000 μm ² ). The results are shown in the following Tables 1 and 2. The following table 1 shows the results for the anisotropic conductive film A, and the following table 2 shows the results for the anisotropic conductive film B.

  As is apparent from Table 1 and Table 2, it can be seen that the number of effective conductive particles contributing to electrical connection is greatly increased by setting the bump surface roughness Ra to 0.05 μm or less. Further, the total number of particles captured is also equal to or greater than that of the comparative example.

  FIG. 3 shows an optical microscope image near the bump in Example 1 (anisotropic conductive film A), and FIG. 4 shows an optical microscope image near the bump in Comparative Example 1 (anisotropic conductive film B). Show. Comparing these drawings, it is clear that the top of the bump is very smooth in Example 1, whereas the top of the bump is rough in Comparative Example 1.

  Further, FIG. 5 shows another optical microscopic image in the vicinity of the bump in Example 1 (anisotropic conductive film A), and FIG. 6 shows another optical microscopic image in the vicinity of the bump in Comparative Example 1 (anisotropic conductive film B). An optical microscope image is shown. Each drawing (photograph) is an optical microscopic image of the periphery of the bump. Comparing these drawings, in Example 1, it can be seen that the conductive particles are uniformly crushed in the entire bump including the peripheral portion of the bump. On the other hand, in Comparative Example 1, the method of crushing the conductive particles is insufficient particularly in the peripheral portion of the bump.

Evaluation of influence of annealing treatment Next, in order to evaluate the influence of the annealing treatment on the surface roughness Ra of the bump, the bumped IC produced as Example 1 was subjected to the annealing treatment, and the surface roughness before and after the annealing treatment. Ra was measured. The results are shown in Table 3 below.

  As is apparent from Table 3 above, when the bumped IC manufactured as Example 1 was annealed, the bump surface roughness Ra after the annealing treatment was 0.0179 μm, for example, the top portion was cut Unlike conventional methods such as annealing the smoothed bumps, the value is kept at 0.05 μm or less.

  This is due to the following reason. That is, the bump produced as Example 1 is formed by accumulating agglomerates (crystal grains) of a gold plating solution, but in order to smooth the top, the crystal state is reduced so that the crystal grains become smaller. A controlled gold plating solution is used. Specifically, in the bump manufactured as Example 1, when the state of the crystal grain of the bump cross section before the annealing treatment is measured, fine crystal grains are gathered as shown in the distribution diagram on the left side in FIG. As shown on the right side in FIG. 7, the average particle size was 0.08 μm. That is, the bump produced as Example 1 was formed by finely stacking small crystal grains having an average grain size of 0.1 μm or less before the annealing treatment. Thus, the crystal grain size is not increased, and the change in the crystal grain size can be suppressed before and after the annealing treatment, and the bump surface roughness Ra is maintained at 0.05 μm or less.

  Thus, in the present invention, the surface roughness Ra of the bump can be 0.05 μm before and after the annealing treatment, and even when the particle diameter of the conductive particles contained in the anisotropic conductive film is small, It was shown that this can be uniformly crushed, and good electrical conduction characteristics can be obtained in the manufactured electrical connection body.

It is a schematic sectional drawing which shows the example of 1 structure of an electrical connection body. It is a schematic sectional drawing which shows typically how to crush the electroconductive particle when the bump surface has unevenness. 2 is an optical microscope image in the vicinity of a bump in Example 1. FIG. 3 is an optical microscope image in the vicinity of a bump in Comparative Example 1. 6 is another optical microscope image in the vicinity of the bump in Example 1. FIG. 10 is another optical microscope image in the vicinity of the bump in Comparative Example 1. FIG. 3 is a diagram illustrating a state of crystal grains of a bump cross section in Example 1.

Explanation of symbols

1 Semiconductor element (first electronic member)
2 Bump 3 Wiring board (second electronic member)
4 Electrode 5 Anisotropic conductive film 6 Conductive particles

Claims (11)

An electrical connection body in which the first electronic member and the second electronic member are electrically connected via an anisotropic conductive film,
A protruding electrode is formed on any one of the electronic members,
The electrical connection body, wherein the top portion of the protruding electrode is a flat surface having a surface roughness Ra after annealing of 0.05 μm or less. 2. The electrical connection body according to claim 1, wherein the top portion of the protruding electrode is a flat surface having a surface roughness Ra of 0.02 μm or less after annealing. The electrical connection body according to claim 1, wherein a top portion of the protruding electrode is formed by gold plating. 4. The electrical connection body according to claim 1, wherein an average particle diameter of the conductive particles contained in the anisotropic conductive film is 4 μm or less. 5. The electrical connection body according to claim 4, wherein the conductive particles have resin particles as a core material, and a conductive layer is formed on a surface thereof. The electrical connection body according to claim 4, wherein the resin particles have a compression hardness at 20% compression deformation of 100 to 1000 kgf / mm ² . A step of forming a protruding electrode having a top surface roughness Ra of 0.05 μm or less by plating on either one of the first electronic member and the second electronic member;
Interposing an anisotropic conductive film between the first electronic member and the second electronic member;
And crushing the conductive particles of the anisotropic conductive film facing the protruding electrode by pressing to electrically connect the first electronic member and the second electronic member. Manufacturing method of electrical connection body. The method for manufacturing an electrical connection body according to claim 7, wherein the top portion of the protruding electrode is a flat surface having a surface roughness Ra of 0.02 μm or less. The method for manufacturing an electrical connection body according to claim 7, wherein a top portion of the protruding electrode is formed by gold plating. 10. The electrical connection according to claim 7, wherein the top portion of the protruding electrode is a flat surface having a surface roughness Ra of 0.02 μm or less after the annealing process. Body manufacturing method. 11. The crystal grain of the plating solution used when forming the protruding electrode has an average grain size before annealing of 0.1 μm or less. 11. The manufacturing method of the electrical connection body of description.