JP5282431B2 - Circuit board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for enhancing the reliability of connections between a semiconductor element and a wiring substrate by avoiding poor electrical connections between an electrode of the semiconductor element and an electrode of the wiring substrate and shortage between the adjacent electrodes, in flip chip implementation. <P>SOLUTION: A circuit substrate includes: a wiring substrate 13 which includes a first electrode 14; a semiconductor device 17 which includes a second electrode 16 in a surface thereof and is arranged on the wiring substrate so that the second electrode is opposed to the first electrode; and a conductive adhesive which is arranged between the wiring substrate and the semiconductor element. The conductive adhesive consists of: a first insulating resin 12; and conductive particles 11 which are dispersed within the first insulating resin and cover a surface of a core particle 1 with a conductive film 2 and a second insulating resin 3, in sequence. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to flip chip mounting of a semiconductor element on a wiring board.

  In recent years, several to several thousand electrode terminals of a semiconductor element are formed depending on the circuit scale of the semiconductor element. Under such circumstances, there is an increasing demand for mounting the electrode terminals of the semiconductor element at a high density, that is, the terminal interval is decreasing. For this reason, a flip chip mounting method has attracted attention in place of wire bonding mounting.

  The flip chip mounting method is a method of mounting a semiconductor element on a wiring board in a state where the semiconductor element is face-down (the circuit surface of the semiconductor element faces downward). In this flip mounting method, generally, a semiconductor element and a wiring board are electrically connected by protruding terminals called bumps. As such a connection method, a connection using a solder bump, a gold bump pressure bonding, a connection using a conductive adhesive, or the like has already been performed.

  Further, after the electrical connection between the opposing terminals, a liquid resin (underfill) is caused to flow from the gap between the adjacent terminals, thereby contributing to protection from the external environment and improvement in connection reliability.

  However, as the gap between the opposing parts and the gap between adjacent terminals become smaller, it becomes difficult to allow the underfill material to flow in. Therefore, a mounting method that does not require inflow of underfill has been proposed.

In this method, a conductive adhesive is applied in advance to a wiring board region on which a semiconductor element is mounted, the positions of the electrodes of the semiconductor element and the wiring board are aligned, and then bonded by thermocompression bonding.
Japanese Patent Laid-Open No. 11-203938 Japanese Patent Laid-Open No. 11-251368 Japanese Patent Laid-Open No. 11-12494

  In such a conductive adhesive, in order to adjust the coefficient of thermal expansion, it is necessary to mix an inorganic filler in a predetermined amount. However, when a large number of inorganic fillers are mixed, an electrode of a semiconductor element or a wiring board is mixed. Inorganic fillers are likely to be sandwiched between the electrode and the conductive particles, which causes an increase in connection resistance and disconnection. In order to avoid such a problem, if the mixing amount of the inorganic filler is limited, the thermal expansion coefficient is not sufficiently reduced, and the connection reliability is lowered.

  Therefore, a flip-chip mounting structure that is excellent in electrical connection between the electrode of the semiconductor element and the electrode of the wiring board, insulation between adjacent electrodes, and excellent in connection reliability is desired.

In order to solve the above problem, according to one aspect of the present invention, a circuit board according to the present invention includes a wiring board including a first electrode, a second electrode on a surface, and the second electrode includes the second electrode. A semiconductor element disposed on the wiring board so as to face the first electrode; and a conductive adhesive disposed between the wiring board and the semiconductor element, the conductive adhesive Is a first insulating resin;
Conductive particles that are dispersed inside the first insulating resin and have the surface of the core particles coated with a conductive film and a second insulating resin in order.

  According to another aspect of the present invention, the conductive adhesive of the present invention is present in a dispersed manner in the first insulating resin and the first insulating resin, and on the surface of the core particle. The conductive particle which coat | covered the electrically conductive film and 2nd insulating resin in order is included.

  Furthermore, according to another aspect of the present invention, the circuit board manufacturing method of the present invention includes a first insulating resin, and a conductive material in which a conductive film and a second insulating resin are sequentially coated on the surface of the core particles. Mixing a particle to form a conductive adhesive; forming a wiring substrate having a first electrode on a surface; forming a semiconductor element having a second electrode on a surface; The step of applying the conductive adhesive to the surface of the wiring substrate or the surface of the semiconductor element, and heating and pressing in a state where the first electrode and the second electrode are aligned, Electrically connecting the second electrode and the second electrode via the conductive adhesive.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to avoid the electrical connection failure of the electrode of a semiconductor element and the electrode of a wiring board and the short circuit between adjacent electrodes, the connection reliability of a semiconductor element and a wiring board can be improved. Furthermore, the thermal expansion coefficient of the wiring board can be reduced at the same time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1A is a plan view showing a circuit board according to an embodiment of the present invention, and FIG. 1B is a view showing a cross section taken along line X-X ′ of FIG. Moreover, FIG.1 (c) is an enlarged view of the electrically-conductive particle in Fig.1 (a).

    As shown in FIG. 1B, the circuit board 10 of this embodiment has a structure in which a semiconductor element 17 is mounted on, for example, a BT resin wiring board 13. The semiconductor element 17 is mounted on the wiring substrate 13 with the circuit surface 17c formed on the substrate 15 facing the wiring substrate 13 side, that is, in a face-down state. Electrode pads 16 are formed on the circuit surface 17c.

  An electrode pad 14 is formed on one main surface of the wiring board 13 on which the semiconductor element 17 is mounted. In addition, the area of the wiring board 13 has a size of 40 mm × 40 mm, for example.

  A gap between the wiring substrate 13 and the semiconductor element 17 is filled with the first insulating resin 12. Conductive particles 11 are dispersed in the first insulating resin 12, and the electrode pads 14 on the wiring board 13 side and the electrode pads 16 on the semiconductor element 17 side are connected via the conductive particles 11.

  As shown in FIG. 1C, the conductive particles 11 have a form in which the conductive particles 2 and the second insulating resin 3 are coated in this order with the inorganic particles 1 as the core.

  In the present embodiment, a material including the first insulating resin 12 and the conductive particles 11 is referred to as a conductive adhesive.

  Since the outer surface of the conductive particle 11 is covered with the second insulating resin 3, the conductive particle 11 exhibits insulating properties when no pressure is applied. However, as will be described later, when the mounting process is performed, the electrode pads 14 on the wiring board 13 side and the electrode pads 16 on the semiconductor element side are electrically connected by the conductive particles 11 connected in the vertical direction. The

  On the other hand, since there is no pressure in the lateral direction, the second insulating resin 3 of the conductive particles 11 connected in the lateral direction does not melt. That is, even if the conductive particles 11 arranged in the horizontal direction are in contact with each other, it is possible to maintain the insulation in the horizontal direction.

  Furthermore, since the inorganic particles 1 are the core of the conductive particles, the inorganic particles 1 do not directly contact the electrode pads 16 of the semiconductor element 17 or the electrode pads 14 of the wiring board 13. Therefore, an increase in connection resistance value can be avoided. At the same time, the presence of the inorganic particles 1 has the effect of lowering the coefficient of thermal expansion of the wiring board 13, so that it is not necessary to add an inorganic filler in addition to the conductive particles.

  Hereinafter, a method for manufacturing a circuit board according to the present invention will be specifically described with reference to the accompanying drawings.

  FIG. 2A to FIG. 2C are cross-sectional views shown in the order of steps of the method of manufacturing the circuit board according to the first embodiment.

  First, conductive particles 11 are created.

As the core particles 1 of the conductive particles 11, for example, non-conductive inorganic particles such as silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are used. In addition to such silica and alumina particles, glass particles, other various ceramic particles, FRP (fiber reinforced plastic) particles, and the like can also be used.

  The shape of the core particle 1 is not particularly limited. Various shapes of particles can be used depending on the application, such as true spherical shape, granular shape, massive shape, crushed shape, porous shape, aggregated shape, flake shape, spike shape, filament shape, fiber shape, whisker shape and the like. In general, it is desirable to use a true spherical powder having as uniform a particle size as possible in order to reduce the variation in electrical conductivity during use.

  In addition, the diameter of the core particle 1 is, for example, in the range of 1 to 20 μm, and preferably about 10 μm on average.

  In order to coat the conductive film 2 on the surface of the core particles, a known method such as electroless plating, sputtering, or vapor deposition of a metal can be used. Examples of the metal include Ag, Au, Ni, Cu, Pt, Pd, and Sn. Ag is most preferable from the viewpoint of conductivity and cost. In addition, these can also be used individually by 1 type or in combination of 2 or more types.

  As a method of forming an insulating coating on the outside of the conductive film, the following known methods can be used. For example, a wet method using a chemical change by an organic solvent or a dispersant, a dry method using a physicochemical change by mechanical energy (specifically, a spray method, a high-speed stirring method, a spray dryer method) and the like can be mentioned.

  The insulating resin 3 to be coated may be a compound containing at least one of functional groups among any of thiol groups, disulfide groups, silanol groups, amino groups, hydroxyl groups, carboxyl groups and the like.

  The insulating resin 3 may be thermoplastic or thermosetting. Examples of resins that can be used for the insulating resin 3 include polyethylene, acrylonitrile, styrene, polybutadiene, ethyl cellulose, polyester, polyamide, polyurethane, natural rubber, silicone rubber, synthetic rubber such as polychloroprene, and polyvinyl ether. It is done.

  Further, the insulating resin 3 is desirably hydrophilic or hydrophobic like the insulating resin 12 so as to be easily mixed with the insulating resin 12.

  Next, an insulating resin 12 for sealing the semiconductor element and the wiring board is produced.

  The insulating resin 12 for sealing the semiconductor element and the wiring board is, for example, a microcapsule type epoxy and imidazole-based curing agent (microcapsule type curing having an imidazole modified as a core and a surface coated with polyurethane. A curing agent formed by dispersing the agent in a bisphenol F-type epoxy resin), and a mercaptan curing agent.

  Specifically, the curing agent is, for example, 40 parts by weight of naphthalene type epoxy “HP-4032D” (trade name) manufactured by Dainippon Ink & Chemicals, Inc., bisphenol F type epoxy “EXA-” manufactured by Dainippon Ink & Chemicals, Inc. "830LVP" (trade name) 30 parts by weight, ADEKA bisphenol F type epoxy "EP-3020" (trade name) 30 parts by weight, microcapsule type imidazole curing agent "LSA-H0206" (product) Name) 25 parts by weight and 50 parts by weight of a mercaptan-based curing agent “QX-40” (trade name) manufactured by Japan Epoxy Resin Co., Ltd. are mixed.

  Next, a conductive adhesive film is produced.

  The insulating resin 12 produced above and 65 parts by weight of the conductive particles 11 were mixed and stirred to produce a conductive adhesive. This conductive adhesive was produced in a sheet shape, and a conductive adhesive film 20 was produced.

  An appropriate amount of a coupling agent may be added in order to improve adhesion at the bonding interface of the conductive adhesive, heat resistance, and moisture resistance. As the coupling agent, a silane coupling agent, a titanium coupling agent, a zirconium coupling agent, an aluminum coupling agent, or the like can be used.

  As the silane coupling agent, the organic functional group contains, for example, at least one of a vinyl group, an epoxy group, a nitro group, a methacryl group, an amino group, a mercapto group, an isocyanato group, a carboxyl group, and a hydroxyl group. For example, a compound in which the functional group contains at least one of a chloro group, an alkoxy group, an acetoxy group, an isopropenoxy group, and an amino group can be used.

  That is, as the silane coupling agent, in addition to 3-mercaptopropyltrimethoxysilane, for example, vinyltrichlorosilane, vinylmethoxysilane, vinyltris (2methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, 3- ( Methacryloxypropyl) trimethoxysilane, 2- (3,4-epoxycyclohexyl) 3-glycidoxypropyl 3-methyldiethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) ) Less than 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, etc. It may be used one also.

Next, a semiconductor element 17 having a size of 8.5 × 8.5 mm ² and having about 120 gold electrode pads 16 disposed in the periphery is prepared. Further, the electrode pads having the same arrangement as the gold electrode pads 16 of the semiconductor element 17 are prepared. A 40 × 40 mm ² BT resin wiring board 13 having the following structure was prepared.

  Next, as shown in FIG. 2A, the conductive adhesive film 20 was laminated and attached to the region where the electrode pads 14 of the wiring substrate 13 were installed. The pressure, temperature, and time for laminating were set to 1 MPa, 60-80 ° C., and 30 seconds, respectively.

  Thereafter, as shown in FIG. 2B, the gold electrode pad 16 of the face-down semiconductor element 17 and the electrode pad 14 of the wiring board 13 were aligned.

  Subsequently, as shown in FIG. 2C, the semiconductor element 17 was pressed against the wiring board 13. The pressure at the time of press contact was 3 MPa, for example. At the same time, the semiconductor element was held on the chip heating tool of the bonder apparatus, and the conductive adhesive film was cured at 150 ° C. for about 10 seconds.

  By such heating and pressurizing processes, the second insulating resin 3 of the conductive particles 11 connected in the vertical direction (specifically, the second insulating resin 3 between the electrode pad 16 and the conductive particles 11). The second insulating resin 3 between the conductive particles 11 and the conductive particles 11 and the second insulating resin 3) between the wiring board electrode pad 14 and the conductive particles 11 are melted, so that the conductive particles Via the conductive film 2, the electrode pad 14 on the wiring substrate 13 side and the electrode 16 on the semiconductor element side are electrically connected.

  The flip chip type circuit board according to this example was manufactured through the above steps.

  As a result of testing the continuity of the joint using the lead wiring on the wiring board 13 side of the circuit board, it was confirmed that all the joints were conducting. Furthermore, in the temperature cycle test of -25 ° C to 125 ° C, a cycle of -25 ° C, 30min to + 125 ° C, 30min was set as one cycle, and a thermal cycle test was repeated for 1000 cycles. As a result, in the circuit board according to this example, the connection resistance change rate was + 5% or less.

  In order to make the thermal expansion coefficient of the insulating resin for sealing as close as possible to the thermal expansion coefficient of the wiring board or semiconductor element, and to reduce the stress on the wiring board or semiconductor element, there are two types with cores with different thermal expansion coefficients. The above conductive particles may be used. High thermal expansion conductive particles that contain core particles with a relatively high coefficient of thermal expansion are placed in the film portion near the wiring board, and low thermal expansion coefficient conductive particles that contain core particles with a relatively low thermal expansion coefficient are used as semiconductors. What is necessary is just to arrange | position to the film part near an element.

In this embodiment, the electrode pad is arranged around the semiconductor element. However, the electrode pad may be arranged at the center of the semiconductor element.
(Comparative Example 1)
In the conductive adhesive, 5 parts by weight of Ni powder was used as the conductive particles. Furthermore, 60 parts by weight of alumina powder was used as a filler. These were mixed and stirred to prepare a conductive adhesive.

  A flip-chip circuit board similar to that in Example 1 was produced, and then continuity was measured in the same manner as in Example 1. As a result, there was a non-conductive junction. As a result of FE-SEM observation, it was confirmed that alumina powder was sandwiched between the electrode pad of the semiconductor element and the Ni powder in the non-conductive joint.

  Next, this embodiment will be described. In Example 2, the material used for the conductive adhesive, the manufacturing method, and the like are different from those in Example 1.

  Since the steps of the method of manufacturing the circuit board according to the present embodiment are the same as those shown in FIGS. 2A to 2C, the same reference numerals are given to the portions corresponding to the portions described above, Description is omitted.

  The conductive adhesive used in Example 2 can be produced by the following method.

  100 parts by weight of bisphenol F type epoxy “EXA830CRP” (trade name) manufactured by Dainippon Ink & Chemicals, Inc., 15 parts by weight of triglycidyl ether of aminomethylphenol, azine adducted imidazole-based curing agent “Curazole C11Z-” manufactured by Shikoku Kasei Co., Ltd. In Example 1, 7.5 parts by weight of A ″ (trade name) and 7.5 parts by weight of microcapsule type imidazole curing agent “Novacure HX3721” (trade name) manufactured by Asahi Kasei Co., Ltd. were mixed. 65 parts by weight of the produced conductive particles were mixed and stirred to produce a conductive adhesive.

  Next, the conductive adhesive 12 produced by the above method was applied to the same wiring substrate 13 as in Example 1, and the wiring substrate 13 was placed on the substrate stage of the bonder apparatus set at 60 ° C. After leaving for about 10 minutes, the gold electrode pad 16 of the face-down semiconductor element 17 and the electrode pad 14 of the wiring board 13 were aligned.

  Thereafter, the electrode pad 16 of the semiconductor element 17 is ultrasonically bonded to the electrode pad 14 of the wiring board 13 under the conditions of 30 ° C. and 0.15 seconds. Thereafter, the semiconductor element was held on the chip heating tool of the bonder apparatus, and the conductive adhesive was cured at 180 ° C. for about 3 seconds, and then the flip chip type circuit board according to this example was manufactured.

  Next, in the same manner as in Example 1, as a result of testing the continuity of the joint, it was confirmed that all the joints were conductive. Furthermore, in the temperature cycle test of -25 ° C to 125 ° C, a cycle of -25 ° C, 30min to + 125 ° C, 30min was set as one cycle, and a thermal cycle test was repeated for 1000 cycles. As a result, in the circuit board of the present invention, the connection resistance change rate was + 5% or less.

The conductive adhesive or conductive adhesive film prepared as described above exhibits conductivity between the electrode pad 16 of the semiconductor element 17 and the electrode pad 14 of the wiring substrate 13, but does not exhibit conductivity in other directions. . Therefore, such a conductive adhesive or a conductive adhesive film is also called an anisotropic conductive adhesive or a conductive adhesive film.
(Comparative Example 2)
In the conductive adhesive, 5 parts by weight of Au powder was used as the conductive particles. Furthermore, 60 parts by weight of alumina powder was used as a filler. These were mixed and stirred to prepare a conductive adhesive.

  A flip-chip circuit board similar to that of Example 2 was produced, and then continuity was measured in the same manner as in Example 2. As a result, the connection resistance value was five times that of Example 2. Furthermore, in the temperature cycle test of -25 ° C to 125 ° C, a cycle of -25 ° C, 30min to + 125 ° C, 30min was set as one cycle. The rate of change was + 10%.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these Examples. For example, various substitutions, changes, improvements, combinations, and the like are naturally possible.

It is a figure which shows the structure of the circuit board based on the Example of this invention. It is sectional drawing which shows the method of manufacturing the circuit board based on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core particle 2 Conductive film 3 2nd insulating resin 10 Circuit board 11 Conductive particle 12 1st insulating resin 13 Wiring board 14 Electrode pad 15 Substrate 16 Electrode pad 17c Circuit surface 17 Semiconductor element 20 Conductive adhesive film

Claims (3)

A wiring board comprising a first electrode;
A semiconductor element provided on a surface of the wiring board so as to have a second electrode and the second electrode facing the first electrode;
A conductive adhesive disposed between the wiring board and the semiconductor element;
The conductive adhesive is
A first insulating resin;
The first present dispersed in the insulating resin, the entire surface thermosetting second insulating resin of the conductive film and the conductive film on the surface of the core particles consisting of inorganic material coated in this order formed, seen including a small diameter of the conductive particles than the distance between said first and second electrodes,
The first and second electrodes are electrically connected via the plurality of conductive particles in the conductive adhesive,
The conductive particles include first and second conductive particles having the core particles having different thermal expansion coefficients as cores,
The abundance ratio of the first and second conductive particles in the conductive adhesive changes in a direction in which the first and second electrodes face each other in a region where the wiring board and the semiconductor element face each other.
A circuit board characterized by that. The circuit board according to claim 1, wherein the first insulating resin includes a microcapsule type epoxy, an imidazole curing agent, and a mercaptan curing agent . First conductive particles in which a conductive film and a thermosetting second insulating resin are sequentially coated on the entire surface of the first core particles made of an inorganic material, and the first core particles and the coefficient of thermal expansion are Dispersed in the first insulating resin film are second conductive particles in which a conductive film and the thermosetting second insulating resin are sequentially coated on the entire surface of the second core particles made of different inorganic materials. Forming a conductive adhesive film comprising a first insulating resin film in which the abundance ratio of the first and second conductive particles changes in the thickness direction;
Forming a wiring board having a first electrode on the surface;
Forming a semiconductor element having a second electrode on the surface;
Arranging the conductive adhesive film on the surface of the wiring substrate or the surface of the semiconductor element;
The first electrode and the second electrode are heated and pressed in a state where the first electrode and the second electrode are opposed to each other while maintaining an interval wider than the diameters of the first and second conductive particles, and the first electrode and the second electrode A step of electrically bonding a plurality of conductive particles in the conductive adhesive film via the plurality of conductive particles
A method of manufacturing a circuit board, comprising: