CN100405506C - Anisotropic Conductive Materials - Google Patents

Abstract

The present invention relates to an anisotropy conducting material for electronic packaging, which comprises an insulating adhesive and conducting particles dispersed on the adhesive, wherein the conducting particles are carbon nanotubes mixed with metal particles and polyaniline. The polyaniline can be the polyaniline containing metallic ions, and hydrogen atoms in the molecule chain of the polyaniline can be displaced by the metallic ions. Because the carbon nanotubes-conducting particles which have nanometer dimension and are mixed with the metal particles are adopted, the anisotropy conducting material of the present invention has large contacting surface area when being connected with a semiconductor element and a substrate. Because the polyaniline has good electric conductivity and adhesiveness, the carbon nanotubes can be well electrically bonded with the semiconductor element and the substrate.

Description

Anisotropic Conductive Materials

【Technical field】

The invention relates to an electronic packaging material, in particular to an anisotropic conductive adhesive material.

【Background technique】

Since the middle and late 1980s, electronic products have been developing in the direction of portability, miniaturization, networking and multimedia. In order to meet the needs of the market, electronic packaging technology must develop in the direction of high density and high speed. Electronic packaging mainly includes chip component packaging and IC packaging.

Chip component packaging is the earliest surface mount component with the largest output, and its packaging mainly adopts Surface Mounted Technology (SMT).

IC packaging has been developed since 1958, during which a variety of packaging technologies have been developed: the first generation of packaging is the pin through hole component packaging type (Pin Through Hole, PTH); the second generation of packaging, that is, surface bonding technology, is adopted to shrink Package volume and increase the number of I/O pins, but basically both use the lead frame as the carrier, use gold wires to connect the chip electrodes and the pins on the lead frame, which belongs to the peripheral packaging method, in the reduction of package volume and I/O The increase in the number of O pins still has its limitations; the third-generation package is AreaArray. Due to the use of area matrix packaging and the introduction of organic substrate carriers, the number of I/O pins, high speed, and high power have been greatly increased. And ultra-thin requirements; the fourth generation of packaging, Bare Die, is to put the bare die directly into the packaging matrix, avoiding the welding process that damages the efficiency of the chip and the melting step that affects the performance of the silicon core . It mainly includes two packaging methods: one is chip on board technology (Chip on Board, COB), and the other is flip chip technology (Flip Chip).

With the evolution of IC packaging technology, the chip bonding has also evolved from Wire Bonding to Tape Automated Bonding (TAB) to the current Flip Chip Bonding.

Wire bonding is the earliest and most widely used technology. This technology first fixes the chip on the lead frame, and then connects the circuit on the chip with the pins on the lead frame with thin metal wires. Tape-and-reel automatic bonding is to connect the chip to the metal circuit on the polymer tape. Flip-chip bonding is mainly to generate I/O bumps on the metal pad of the chip, and generate solder joints corresponding to the I/O bumps on the substrate, and then flip the chip to align with the corresponding solder joints on the substrate, and then place the chip Bonds to all I/O points on the substrate.

However, in the above chip bonding methods, only point-to-point soldering can be performed, so the soldering process is complicated and the speed is slow.

In 1997, Japan's Xinli Chemical Co., Ltd. developed and commercialized an anisotropic conductive film (Anisotropic Conducting Film, ACF) (hereinafter referred to as ACF) that can connect several electrodes together. It was initially applied to liquid crystal displays for calculators ( The connection between Liquid Crystal Display (LCD) and carbon printed wiring was later popularized for the connection between LCD and Flexible Printed Circuit (FPC). At present, ACF is widely used in large and medium-sized LCD modules assembled in TAB mode, as well as in the connection of COB and Flip Chip.

ACF refers to a film prepared by uniformly dispersing conductive particles that play a conductive role in an adhesive adhesive with insulating properties. The connection principle is that the ACF is sandwiched between the adherend terminals. In this state, heat and pressurize it to remove excess adhesive on the terminal, use the conductive particles sandwiched between the terminals to make it have conduction performance, and then pass the adhesive while maintaining its adhesive performance and resistance. Insulate between adjacent terminals.

China Taiwan Patent No. 250592 published on July 1, 1995 discloses an anisotropic conductive adhesive film, comprising an insulating adhesive, conductive particles dispersed in the insulating adhesive, and dispersed in the insulating adhesive. Transparent, spherical glass particles in an adhesive. The conductive particles are metal particles, such as nickel, aluminum, silver and other particles.

China Taiwan Patent No. 277152 published on June 1, 1996 discloses a method of manufacturing an anisotropic conductive resin film, which includes adhering conductive particles on an adhesive layer on a carrier and fixing therein, and The conductive particles are filled with a resin that is incompatible with the adhesive material, and the film has conductivity only in the thickness direction through the conductive particles uniformly dispersed in the plane direction, and is used for facing a large number of electronic parts with fine electrodes. Electrical connections between electrodes. Wherein, the conductive particles are plastic particles covered with a metal film.

China Taiwan Patent No. 525252 published on March 21, 2003 discloses an anisotropic conductive connecting material, which contains an insulating adhesive and conductive particles. The conductive particles are polymers coated with a metal layer. In the particles formed on the surface of the core material particles, the average particle diameter of the conductive particles is 1.5 times or more the difference between the height of the passivation film and the height of the semiconductor element electrode.

However, the sizes of the conductive particles in the above-mentioned prior patents are all in the micron order, and the large conductive particles have poor adhesion when connected to semiconductor elements and substrates.

Therefore, it is necessary to provide an anisotropic conductive material having nanoscale conductive particles with better adhesion.

【Content of invention】

The object of the present invention is to provide an anisotropic conductive material having conductive particles with better adhesion.

To achieve the purpose of the present invention, the present invention provides an anisotropic conductive material applied to electronic packaging, comprising an insulating adhesive and conductive particles dispersed in the adhesive, the conductive particles are doped with metal particles and Carbon nanotubes of polyaniline.

Wherein, the polyaniline may be polyaniline containing metal ions, and hydrogen atoms in its molecular chain are replaced by metal ions.

Compared with the prior art, the anisotropic conductive material of the present invention has a larger contact with the semiconductor element and the substrate due to the use of nano-sized carbon nanotube conductive particles doped with metal particles and polyaniline. The surface area, and the polyaniline after replacing copper or iron ions has better conductivity and adhesion, so that carbon nanotubes can be better electrically bonded to semiconductor elements and substrates.

【Description of drawings】

Fig. 1 is a schematic diagram of an anisotropic conductive film of the present invention.

2是本发明使用状态的各向异性导电膜示意图。picture

2 is a schematic diagram of the anisotropic conductive film in the use state of the present invention.

FIG. 3 is a schematic diagram of the connection structure of the ACF of the present invention applied to a semiconductor package.

4A to 4F are schematic diagrams of the steps of applying the ACF of the present invention to flip-chip packaging.

【Detailed ways】

The present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to FIG. 1 , the anisotropic conductive film 10 of the present invention includes an insulating adhesive 12 and nano conductive particles 14 dispersed in the adhesive 12 .

The adhesive 12 can be epoxy resin, phenolic resin, polyester resin containing hydroxyl groups, or acrylic resin containing hydroxyl groups. The adhesive 12 of the present invention can be any electrically insulating resin that can be cured under heating or ultraviolet (UV) irradiation, and there is no special limitation. In addition, a hardener may be added to the adhesive 12 . Based on the considerations of curing temperature, time, maintaining stability, etc., it is preferable to use epoxy resin. The epoxy resin can be selected from bisphenol-formaldehyde epoxy resins, phenolic resins for epoxy paints or epoxy compounds with at least two oxirane groups in the molecule.

The nano conductive particles 14 are carbon nanotubes doped with metal particles and polyaniline, wherein the polyaniline can be polyaniline containing metal ions, and the hydrogen atoms in its molecular chain are replaced by metal ions. The carbon nanotubes can be columnar multi-walled carbon nanotubes or single-walled carbon nanotubes, at least one end of which is open to facilitate the doping of metal particles and polyaniline inside the carbon nanotubes. The doped metal particles include gold, silver, Metal particles such as copper, nickel or iron.

The preparation of the anisotropic conductive film 10 of the present invention comprises the following steps:

First, carbon nanotubes doped with metal particles are provided, which can be prepared by an arc discharge method or a laser ablation method.

Second, the carbon nanotubes doped with metal particles are mixed with polyaniline, so that the polyaniline penetrates into the interior of the carbon nanotubes. The polyaniline has better conductivity and adhesion, and its structure is shown in the following formula:

Alternatively, polyaniline containing metal ions and carbon nanotubes doped with metal particles may be mixed. Preparation of polyaniline containing metal ions: add the polyaniline to the hydrogen chloride solution, add metal particles such as copper, iron, nickel or gold at an appropriate temperature, and replace the nitrogen atom with the molecular chain of the polyaniline polymer. Co-bonded hydrogen atoms (as shown in the above formula) generate polyaniline containing metal ions, which has better conductivity and adhesion, and its structure is shown in the following formula (A represents metal ions):

Finally, the carbon nanotubes doped with metal particles and polyaniline were mixed with the adhesive 12 to make ACF.

When the ACF of the present invention is used, the electrodes of the semiconductor element and the circuit substrate are made to face each other, an anisotropic conductive film 10 is interposed therebetween, the two are mechanically fixed by hot pressing technology, and the (Z Axis direction) is electrically connected, and the adjacent electrodes (X, Y axis direction) are kept in an insulated state. As shown in Fig. 2, it is the ACF in use according to the present invention.

Please refer to FIG. 3 , the first embodiment of the present invention, the ACF of the present invention is applied to a semiconductor package, and the ACF is connected to a semiconductor element 34 and a circuit substrate 36 .

A plurality of electrodes 342 are formed on one side of the semiconductor element 34 , and a passivation film 344 is formed around the plurality of electrodes 342 , wherein the thickness of the electrodes 342 is smaller than the thickness of the passivation film 344 . The electrode 342 can be made of aluminum, copper and other metals, and the passivation film 344 can be made of polyimide resin, polystyrene cyclobutene and other resins. The circuit board 36 has a plurality of electrodes 362 at positions corresponding to the electrodes 342 of the semiconductor element 34 . The circuit substrate 36 can be selected from resin substrates such as epoxy resin and glass substrate, and the plurality of electrodes 362 can be selected from common conductors such as aluminum and copper.

The ACF of the present invention is placed between the connected member, that is, the semiconductor element 34 and the circuit substrate 36 whose electrodes 342 and 362 are aligned with each other, respectively. As indicated by arrows in FIG. 3 , pressure and heat are applied from both outsides of the semiconductor element 34 and the circuit board 36 . Under pressure and heat, the electrical insulating resin 32 of the ACF has plasticity, and finally the electrodes are in contact with the nano conductive particles 31, and the excess electrical insulating resin 32 is concentrated in the part where the electrodes 342 and 362 do not exist. A plurality of conductive nano particles 31 are fully in contact with the electrodes 342, 362 at both ends. Because the nanoparticles have a larger surface area and the polyaniline inside and at the port of the conductive nano particles has better adhesion, the semiconductor element 34 and the circuit The substrate 36 has a better bonding effect. After heating and pressing, it is necessary to harden the ACF dispersed with carbon nanotube conductive particles. The ACF can be irradiated with laser or ultraviolet (UV) to harden the insulating resin 32 and polyaniline, and finally the semiconductor element 34 and the circuit substrate 36 can be obtained. Electrical connection between electrodes, electrical insulation between adjacent electrodes, and better mechanical fixation between the semiconductor element 34 and the circuit substrate 36 .

Please refer to FIG. 4A to FIG. 4F together, the second embodiment of the present invention, in the flip-chip packaging technology, the application steps of the ACF of the present invention:

Step 1, as shown in FIG. 4A , an electrically insulating adhesive layer 42 is formed on the surface of the matrix resin film 43 by coating or other means.

Step 2, as shown in FIG. 4B , the nano conductive particles 41 are distributed and fixed on the surface of the adhesive layer 42 through the adhesive force of the adhesive substance.

Step 3, as shown in FIG. 4C , filling the gap of the conductive nano particles 41 with the adhesive solution. Because the nano conductive particles 41 are fixed on the adhesive layer 42 and do not move in the adhesive solution, the particles do not agglomerate during coating, and the particles are uniformly arranged on a plane, and then the solvent is dried to form an adhesive layer 40 . The adhesive layer 40 and the nano conductive particles 41 dispersed in the adhesive layer 40 constitute the ACF of the present invention.

Step 4, as shown in FIG. 4D , when connecting the circuit, the adhesive layer 40 needs to be transferred to the surface of the chip 49 , and the surface is provided with a plurality of electrodes 490 . The adhesive layer 40 can be pressed to the surface of the chip 49 , and then the adhesive layer 42 can be peeled off along the interface between the adhesive layer 40 and the adhesive layer 42 . Because the materials of the adhesive layer 40 and the adhesive layer 42 are not compatible with each other, the material layers thereof are easily separated from each other along the interface.

Step five, as shown in FIG. 4E , connect the adhesive layer 40 prepared in step four with the chip 49 and the circuit substrate 48 . The circuit substrate is provided with electrodes 480 corresponding to the chip electrodes 490 . By aligning the electrodes of the two circuits, the two circuits are pressurized and heated under the action of the pressing equipment 45 , 46 , and the electrical connection is formed through the nano conductive particles 41 .

Step 6, as shown in FIG. 4F, harden the adhesive layer 40 and the nano-conductive particles 41, and finally the electrical connection between the electrodes facing the connected members can be obtained, the electrical insulation between adjacent electrodes, and the connected members have a relatively high Good mechanical fixation.

In this embodiment, the circuit substrates that can adopt the flip-chip technology include ceramics, silicon chips, polymer laminates, and glass. The application range of flip-chip technology includes high-end computers, PCMCIA cards, military equipment, personal communication products, clocks and liquid crystal displays, etc. When flip-chip technology is applied to liquid crystal displays, because the substrate is glass, it is also called COG (Chip On Glass).

It can be understood that the ACF of the present invention is also applicable to the packaging of LCD and flexible printed circuit boards, the packaging of large and medium-sized LCD modules assembled in a TAB manner, and the packaging of chip-on-board (COB).

The anisotropic conductive material of the present invention adopts nanometer-sized carbon nanotube conductive particles doped with metal particles and polyaniline, so that it has a larger contact surface area when it is connected with a semiconductor element and a substrate, and after replacing metal ions Polyaniline has better conductivity and adhesion, which makes carbon nanotubes better electrically bonded to semiconductor components and substrates.

Claims (8)

1. anisotropic conductive material comprises the adhesive of insulating properties and is scattered in the conducting particles of this adhesive, it is characterized in that this conducting particles is the carbon nano-tube that is doped with metallic and polyaniline.

2. anisotropic conductive material as claimed in claim 1 is characterized in that the hydrogen atom in this polyaniline molecule chain is replaced by metal ion.

3. anisotropic conductive material as claimed in claim 1 is characterized in that this adhesive is hardenable electric insulation resin.

4. anisotropic conductive material as claimed in claim 3 is characterized in that this electric insulation resin comprises epoxy resin, phenolic resins, contains the alkyd resin of hydroxy or contains the acrylic resin of hydroxy.

5. anisotropic conductive material as claimed in claim 1 is characterized in that this adhesive is added with curing agent.

6. anisotropic conductive material as claimed in claim 1 is characterized in that carbon nano-tube comprises Single Walled Carbon Nanotube and multi-walled carbon nano-tubes.

7. anisotropic conductive material as claimed in claim 1 is characterized in that metallic comprises gold, silver, copper, nickel or ferrous metal particle.

8. anisotropic conductive material as claimed in claim 2 is characterized in that this metal ion comprises copper, iron, nickel or gold ion.

Images