JP2008235656A - Package of circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a package of a circuit board capable of packaging a circuit board to a thin board and a plastic board having a low heat resistance at low temperatures without applying pressure. <P>SOLUTION: The package of the circuit board is formed by arranging an exposed conductive pattern 12 formed by opening an insulating layer of the circuit board 10 in positioning to an electrode terminal 42 of an electronic circuit 40, and by adhering it from the conductive pattern 12 side with a pressure-sensitive adhesive sheet 30. The conductive pattern 12 is stressed in a direction pressed to the electrode terminal part 44 of the electronic circuit 40 by an elasticity of the pressure-sensitive adhesive sheet 30 to be able to stably retain an electrical connection. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to mounting used for connecting circuit boards such as a printed circuit board constituting an electronic device, and for connecting a circuit board to a glass substrate or a plastic substrate of a display device such as a liquid crystal panel.

  Conventional circuit board mounting methods include a method of thermocompression bonding using an anisotropic conductive adhesive and a fusion connection using solder. (For example, refer to Patent Document 1).

  The mounting method disclosed in Patent Document 1 will be described with reference to FIG. FIG. 9 is a process sectional view showing a process of the conventional mounting method.

  First, as shown in FIG. 9A, in the conventional mounting method, first, the transparent electrode film 91 of the glass substrate 90 of the liquid crystal panel and the conductive pattern 12 of the circuit board 10 are aligned, and the conductor facing the transparent electrode film 91 is positioned. An anisotropic conductive adhesive film 93 containing conductive particles 92 is disposed between the patterns 12. Next, the anisotropic conductive adhesive film 93 is heated and cured by applying heat and pressure from the circuit board 10 side using the heating head 94.

  The mounting process is performed by heating from 120 ° C. to 180 ° C., applying a pressure of 30 to 60 kg / cm 2 to press the conductive particles, and holding this temperature for 12 to 20 seconds.

  After heating and pressurization, as shown in FIG. 9B, the conductive particles 92 of the anisotropic conductive adhesive film 93 are crushed by the transparent electrode film 91 and the conductive pattern 12, so that the vertical electrical conduction can be performed. become. Further, since the conductive particles 92 are not in contact in the lateral direction, the conductive particles 92 do not conduct and an anisotropic conductive connection is possible.

  In the conventional example, a thermosetting adhesive such as an epoxy resin is used for the adhesive resin used for the anisotropic conductive adhesive film 93, and heat pressure is applied to press the conductive particles 92 and cure the adhesive resin. An implementation method is used.

Japanese Patent Laid-Open No. 3-289627 (FIG. 4)

  In the conventional example, a mounting method using a liquid crystal panel is shown. However, a glass epoxy substrate, which is a general electronic circuit board, or a flexible printed circuit board using polyimide as a base material is mounted in a similar manner. Yes.

  In recent years, with the miniaturization and thinning of electronic devices, the miniaturization of wiring patterns and the thinning of circuit boards have been promoted by increasing the density of conductor patterns on circuit boards, and the thickness of glass substrates has also been reduced in displays such as liquid crystal panels. Development of thin and light LCD panels using plastic substrates and plastic substrates is underway. Such substrate materials are vulnerable to the heating and pressurizing processes applied during the mounting process, and the deformation and expansion of the wiring pattern associated with the deformation and disconnection of the wiring pattern are likely to occur due to deformation and expansion of the substrate due to heating and pressurization. Reduction of damage to the substrate during mounting is desired.

However, in the mounting method described in Patent Document 1, the temperature and pressure applied to the circuit board at the time of mounting are very large, and when this mounting method is performed on a thin substrate or a plastic substrate,
Since the above-described deformation or alteration due to thermal expansion of the substrate causes displacement or disconnection of the wiring pattern, there is a problem that it is difficult to adapt to a thin substrate, a plastic substrate, or a circuit substrate on which a fine wiring pattern is formed.

  Furthermore, in the mounting method described in Patent Document 1, it is necessary to crush the conductive particles by applying pressure to make contact with the wiring pattern of the circuit board in order to establish electrical continuity. It is necessary to apply pressure with a high degree of parallelism. Therefore, high precision flatness is required for the substrate material itself.

  In such a mounting method, it is necessary to frequently perform maintenance work for maintaining high-precision parallelism for the heating and pressing apparatus. Furthermore, it is necessary to perform heating at a temperature of slightly less than 200 ° C., which increases the power consumption of the apparatus. Therefore, there is a problem that workability is not good and efficiency is low.

  As is apparent from the above, the mounting method described in Patent Document 1 is difficult to adapt to a substrate with a low heat resistance such as a thin circuit board or a plastic substrate or a substrate with a fine wiring pattern. Due to the high cost, it has been considered difficult to produce an electronic circuit having a fine wiring pattern on a thin circuit board at a low cost.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and provide a method capable of mounting on a substrate with high accuracy and low cost even for a thin substrate, a plastic substrate, or a circuit substrate having a fine wiring pattern.

  In order to solve the above problems, the mounting method of the present invention basically adopts the following constituent elements.

  The present invention relates to an electronic circuit having a circuit board in which a conductive pattern is formed on a first insulating layer, a second insulating layer is further formed on the conductive pattern, and an electrode terminal portion in which the electrode terminals are exposed. In the circuit board mounting body electrically connected to each other, the circuit board includes a circuit board terminal portion in which both of the first insulating layer and the second insulating layer are opened and the conductive pattern is exposed. The circuit board and the electronic circuit are electrically connected and fixed between the adhesive sheet having adhesiveness at room temperature and the electrode terminal part of the electronic circuit with the circuit board terminal part interposed therebetween.

  The pressure-sensitive adhesive sheet is characterized in that it is thicker than the total thickness of at least the thickness of the conductor pattern and the thickness of the electrode terminal of the electronic circuit. The pressure-sensitive adhesive sheet is characterized by having a structure including an elastic support and an adhesive material disposed on one side of the support.

  A conductive material having a convex structure is provided on at least one of the conductive pattern in the circuit board terminal portion or the electrode terminal of the electronic circuit. An electronic circuit is a component of a device using a plastic substrate, and an electrode terminal of the electronic circuit is a connection electrode to an external circuit arranged on the plastic substrate.

  By adopting the circuit board mounting body of the present invention, even a circuit board with a low heat resistance substrate material such as a thin circuit board or a plastic substrate or a circuit board on which a fine wiring pattern is formed may be deformed. It can be implemented without causing any damage. Furthermore, the flatness of the circuit board is ensured and the maintenance of the apparatus for mounting is simplified, so that the mounting can be performed at low cost.

  The circuit board mounting method of the present invention will be described below with reference to the drawings. First, the structure of the circuit board in the present embodiment will be described. 2A is a perspective view of the circuit board, and FIG. 2B is a top view.

  First, as shown in FIG. 2A, the structure of the circuit board 10 such as a flexible circuit board is such that a conductive pattern 12 is formed on a first insulating layer 11 using a conductor, and further on that. The second insulating layer 13 is formed. In order to form the terminal part 14 used for connection with another board | substrate, both the 1st insulating layer 11 and the 2nd insulating layer 13 were opened, and the structure which formed the circuit board terminal part 14 which exposed the conductive pattern 12 was formed. It has become.

  FIG. 2B shows a plan view of the circuit board as viewed from above. Since the first insulating layer 11 and the second insulating layer 13 are opened, the conductor pattern 12 is exposed at the terminal portion 14.

  The material of the first insulating layer 11 and the second insulating layer 13 is an insulating material, and a general substrate material such as a polyimide film or a glass epoxy substrate can be used. Moreover, the conductor used for the conductive pattern 12 forms a wiring pattern by an etching method using copper foil. Further, the exposed portion of the conductor pattern 12 of the terminal portion 14 is configured to be plated with gold or nickel in order to prevent oxidation of the copper surface. The conductive pattern 12 may be a thin-film metal material that does not collapse the shape of the conductor pattern 12 exposed at the circuit board terminal portion 14, and gold, aluminum, or the like can also be used.

  Further, in the structure shown in FIG. 2, the circuit board terminal portion 14 where the conductor pattern 12 is exposed is not the endmost part of the circuit board 10, but is a perspective view shown in FIG. 3A and FIG. 3B. A structure in which the first insulating layer 11 and the second insulating layer 13 at the extreme ends are removed as shown in the plan view. In FIG. 3, the first insulating layer 11 and the second insulating layer 13 are opened at the end of the circuit board 10 to form a circuit board terminal portion 14. In this case, as shown in the perspective view of FIG. 3A, the conductor pattern 12 is completely exposed to be in a flying lead state, and the tip of the conductor pattern 12 is located anywhere as shown in the plan view of FIG. It is not fixed. Any circuit board shown in FIG. 2 or 3 may have a structure in which the conductor pattern 12 is exposed. However, when the width of the conductor pattern 12 is quite narrow, it is preferable to have an insulating layer at the end as shown in FIG.

  Next, the structure of the pressure-sensitive adhesive sheet 30 used in the present invention will be described with reference to FIG. FIG. 4A is a cross-sectional view of the pressure-sensitive adhesive sheet 30 used in the present invention. A rubber-based, acrylic resin-based or silicone resin-based pressure-sensitive adhesive is applied to a support 31 such as paper, polyimide film, or PET film. It has a two-layer structure used. Further, as shown in FIG. 3B, the support 31 is made of an elastic rubber film, a sponge-like elastic body made of PET or the like, and the adhesive material 32 is thinly formed on the surface of the support 31. Good. In any case, it is sufficient that the pressure-sensitive adhesive sheet 30 has a resilient structure.

  FIG. 1 is an exploded perspective view showing configurations of a circuit board and an electronic circuit according to the present embodiment. As the electronic circuit, a flexible circuit board or a circuit in which connection wiring for connecting to an external circuit is arranged on a plastic substrate, an IC chip having an electrode terminal, or the like can be used. As shown in FIG. 1, the electronic circuit 40 has a structure in which an electrode terminal 42 is formed on an electronic circuit first insulating layer 41 and an electronic circuit second insulating layer 43 is formed thereon. In addition, the electronic circuit second insulating layer 43 is opened, and the electrode terminal portion 44 is formed in which the electrode terminal 42 is exposed. Further, the circuit board 10 is disposed on the electronic circuit 40, and the adhesive sheet 30 is disposed so as to cover the conductor pattern 12 of the circuit board terminal portion 14 from above the circuit board terminal portion 14.

  Hereinafter, the mounting process will be described with reference to the cross-sectional structure of the AA ′ portion shown in FIG. As shown in FIG. 5A, first, the electrode terminal portion 44 of the electronic circuit 40 which is the counterpart material and the conductor pattern 12 exposed at the circuit board terminal portion 14 of the circuit board 10 are aligned. Next, as shown in FIG. 5B, the pressure-sensitive adhesive sheet 30 shown in FIG. 4 is stacked on the conductor pattern 12 of the circuit board 10, and although not shown, pressure is applied using a pressure jig, thereby pressure-sensitive adhesive sheet 30. The adhesive material 32 is adhered to the surface of the electronic circuit 40 so that the cross-sectional structure shown in FIG.

  In the pressurizing step of FIG. 5B, it is necessary to carry out with a pressurizing force sufficient to bring the adhesive material 30 into close contact with the surface of the electronic circuit 40, and a pressurizing force of several tens g to 10 kg is applied per square centimeter. The pressurization time may be maintained only for the time when the adhesive sheet 30 is in close contact with the electronic circuit 40, and the pressurization is performed for several seconds to 10 seconds.

  Although heating is not required at the time of pressurization, the pressurization step can be performed at room temperature. However, heating may be performed to increase the adhesion between the pressure-sensitive adhesive sheet 30 and the electronic circuit 40, and the heating temperature is from room temperature to 80 ° C. .

  The thickness of the adhesive sheet 30 is set to be thicker than the total thickness of the conductor pattern 12 of the circuit board 10 and the electrode terminal 42 of the electronic circuit 40 shown in FIGS. 2 and 3. With such a thickness, the pressure-sensitive adhesive 32 of the pressure-sensitive adhesive sheet 30 comes into contact with and adheres to the surface of the printed circuit board 40 by the pressure applied in the step of FIG. When the adhesive material 30 is thinner than the total thickness of the conductor pattern 12 and the electrode terminal 42, the adhesive material 32 does not reach the surface of the printed circuit board even if it is pressed, so that it cannot be bonded.

  FIG. 6 shows a mechanism in which electrical continuity is stably maintained in a mounting body manufactured by the circuit board mounting method of the present invention. FIG. 6 shows a cross-sectional structure after the mounting process shown in FIG. Since the adhesive material 32 of the adhesive sheet 30 is bonded to the electronic circuit 40, the elasticity of the adhesive sheet 30 acts in the direction of the stress 60 indicated by the arrow in the figure, thereby pressing the conductor pattern 12 downward. As described above, the stress 60 is generated, and the conductor pattern 12 can be exerted with a force such that the electrode terminal 42 of the electronic circuit 40 is always in contact with the conductor pattern 12. As a result, the electrical connection can always be made stably.

  Furthermore, even if this structure has extremely poor flatness of the circuit board 10 or the electronic circuit 40 and the circuit board terminal portion 14 and the electrode terminal portion 44 are not pressurized, a sufficient contact area cannot be obtained. Since the elasticity of the pressure-sensitive adhesive sheet 30 absorbs variation in flatness and deforms and adheres, electrical connection can be reliably performed even when the flatness of the members is not highly accurate. Similarly, it is not necessary to adjust the parallelism of the pressing jig with high accuracy for the mounting machine used for pressing, and it is possible to mount using a mounting machine with a simple structure.

  7A and 7B and FIGS. 8A and 8B show a structure for further ensuring electrical conduction. A convex structure 70 is formed on at least one surface of the circuit board terminal portion 14 of the circuit board 10 or the electrode terminal portion 44 of the electronic circuit 40 by stud bumps or plating. In FIG. 7, convex structures 70 are provided on both the circuit board 10 and the electronic circuit 40.

  FIG. 7A is a perspective view showing a case where the convex structure 70 is formed on the conductor pattern 12 on the circuit board 10 side. FIG. 7B is a perspective view showing a case where the convex structure 70 is formed on the electrode terminal 42 of the electronic circuit 40. By performing the pressurizing step shown in FIG. 5B using the substrate thus processed, the cross-sectional structure of the connection portion becomes a cross-sectional structure as shown in FIGS. 8A and 8B.

FIG. 8A is a cross-sectional view when the convex structure 70 is formed on the conductor pattern 12 of the circuit board 10, and FIG. 8B is a cross-sectional structure when the convex structure 70 is formed on the electrode terminal 42 of the electronic circuit 40. It is. In either case, the projecting structure 70 can be pierced into the mating member, thereby ensuring electrical continuity. In addition, even when it is difficult to make an electrical connection due to dirt on the surface of the circuit board terminal part 14 or the electrode terminal part 44, it is possible to stabilize the electrical conduction because the convex structure 70 penetrates the dirt on the surface. become.

  As described above, in the mounting body of the present invention, the electrical connection between the circuit board and the electronic circuit can be performed by a simple process in which the adhesive sheet is adhered and adhered to the electronic circuit. The pressurization can be performed by a simple process of performing only a few seconds. Therefore, it can be stably mounted even on a thin substrate or a plastic substrate having low heat resistance.

  In the conventional method, the adhesive is heat-cured at a temperature of less than 200 ° C., and at the same time, several tens of kg per square centimeter is applied, and the conductive particles are crushed to achieve electrical conduction. Therefore, mounting on a thin substrate that is easily deformed or a plastic substrate that is easily deformed by heat is difficult.

  Furthermore, in the conventional method, since the conductive particles must be crushed uniformly, the adjustment of the flatness of the heating / pressurizing head of the mounting machine must be made highly accurate, and regular maintenance is required. In general, it is necessary to adjust the flatness of the heating and pressing head within several microns.

  However, in the mounting method of the present invention, since the elasticity of the adhesive material has the effect of making the variation in flatness during pressing uniform, there is no need to adjust the flatness of the pressure jig with high accuracy. Maintenance, such as adjusting the flatness, becomes very easy.

  Further, when mounting at room temperature, it is not necessary to provide a heating mechanism in the mounting machine itself, so that the mounting machine can be moved at low cost with almost no power consumption of the mounting machine. Even when heating, the temperature is up to about 80 ° C., so that the power consumption is significantly less than that of the conventional method.

  As is apparent from the above description, the mounting process of the circuit board mounting body of the present invention can be performed at a low temperature and a low load.

  Further, it is possible to provide a mounting method capable of accurately and inexpensively mounting a circuit board on a thin substrate that is easily deformed or a plastic substrate having low heat resistance or connecting to a circuit board having a fine wiring pattern. .

It is a perspective view explaining the mounting body of the circuit board of this invention. It is a figure which shows the structure of the circuit board used by this invention. It is a figure which shows the structure of the circuit board used by this invention. It is sectional drawing which shows the structure of the adhesive sheet used by this invention. It is sectional drawing which shows the mounting method of the circuit board of this invention. It is sectional drawing which shows the state after mounting of the circuit board in this invention. It is a perspective view which shows the convex structure formed on the conductor pattern used by this invention. It is sectional drawing which shows the state after mounting of the circuit board in this invention. It is sectional drawing which shows the mounting method of the conventional circuit board.

Explanation of symbols

10 Circuit board
DESCRIPTION OF SYMBOLS 11 1st insulating layer 12 Conductive pattern 13 2nd insulating layer 14 Circuit board terminal part 30 Adhesive sheet 31 Support body 32 Adhesive material 40 Electronic circuit 41 Electronic circuit 1st insulating layer 42 Electrode terminal 43 Electronic circuit 2nd insulating layer 44 Electrode terminal Part 60 Stress 70 Convex structure 90 Glass substrate 91 Transparent electrode film 92 Conductive particle 93 Anisotropic conductive adhesive film 94 Heating head

Claims (5)

A circuit board having a conductive pattern formed on the first insulating layer and a second insulating layer formed on the conductive pattern is electrically connected to an electronic circuit having an electrode terminal portion from which the electrode terminal is exposed. In a circuit board mounted body that is connected
The circuit board includes a circuit board terminal portion in which a part of both the first insulating layer and the second insulating layer is opened to expose the conductive pattern,
The circuit board and the electronic circuit are electrically connected and fixed with the circuit board terminal part sandwiched between the adhesive sheet having adhesiveness at room temperature and the electrode terminal part in the electronic circuit. A circuit board mounting body. 2. The circuit board mounting body according to claim 1, wherein the adhesive sheet is thicker than a total thickness including at least the thickness of the conductor pattern and the thickness of the electrode terminal of the electronic circuit. 2. The circuit board mounting body according to claim 1, wherein the pressure-sensitive adhesive sheet has a structure including a resilient support and a pressure-sensitive adhesive disposed on one side of the support. 2. The circuit board mounting body according to claim 1, wherein a conductive material having a convex structure is provided on at least one of the conductive pattern in the circuit board terminal portion or the electrode terminal of the electronic circuit.   The electronic circuit is a component part of an apparatus using a plastic substrate, and the electrode terminal of the electronic circuit is a connection electrode with an external circuit arranged on the plastic substrate. Item 4. A circuit board mounting body according to Item 1.

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