JP2006005302A - Flexible substrate and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible substrate of high reliability in connection and a manufacturing method of the same when bonded to a semiconductor element or other substrates through a conductive adhesive. <P>SOLUTION: In the flexible substrate 1 that a flexible film substrate 2 is bonded to the semiconductor element or other substrates through the conductive adhesive 4, the substrate is characterized in that the surface of the film substrate 2 is of rough nitride surface. Since the rough surface allows the substrate to obtain anchor effect in the conductive adhesive at the time of bonding, thereby increasing adhesion, sufficient connection strength can be secured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flexible substrate that is formed of a flexible film-like substrate, and the film-like substrate is bonded to a semiconductor element or another substrate via a conductive adhesive, and a method for manufacturing the same.

  A flat panel display (hereinafter referred to as FPD) such as a liquid crystal display (hereinafter referred to as LCD) or a plasma display panel (hereinafter referred to as PDP). A flexible substrate having flexibility is used as a substrate for mounting a control IC (Integrated Circuit), and as a wiring cable for connection.

  When this flexible substrate is connected to an LCD or PDP, an anisotropic conductive film (hereinafter referred to as ACF) or an anisotropic conductive paste (hereinafter referred to as ACP) is used. It is bonded with a conductive adhesive.

  When the flexible substrate and the FPD are connected using ACF or ACP, the adhesion between the flexible substrate and another substrate is a major factor for connection reliability.

  As a technique for improving the adhesion, Patent Document 1 discloses a method for manufacturing a liquid crystal display device in which a flexible substrate is connected to an LCD via an ACF.

The method of manufacturing a liquid crystal display device described in Patent Document 1 is characterized in that after an Ar plasma process or an O ₂ plasma process is performed on an input terminal of an LCD, the LCD and a flexible substrate are connected via an ACF. .

According to this manufacturing method, by applying Ar plasma treatment or O ₂ plasma treatment to the input terminals of the LCD, dirt and the like can be removed without contacting each input terminal, so that adhesion can be improved.
JP 2000-1111938 A

In the method of manufacturing a liquid crystal display device described in Patent Document 1, the adhesion between the LCD and the ACF is improved by performing Ar plasma treatment or O ₂ plasma treatment on the input terminal of the LCD.

  However, the adhesion between glass, which is a material of LCD, and ACF is sufficiently secured, and peeling due to physical stress occurs at the interface between the flexible substrate and ACF. In addition to the low adhesion between ACF and polyimide, which is the base material for flexible substrates, this delamination is caused by the deposition of surface contaminants that adhere to the flexible substrate and carbon and other contaminants that float in the atmosphere. Is more likely to occur because the adhesion is further reduced. Therefore, in order to increase the connection reliability, it is necessary to increase the connection strength on the side of the flexible substrate connected to the LCD, rather than improving the adhesion between the glass as the LCD material and the ACF.

  Therefore, an object of the present invention is to provide a flexible substrate having high connection reliability and a method for manufacturing the same when bonding to a semiconductor element or another substrate via a conductive adhesive.

  In order to achieve the above object, the present invention provides a flexible substrate formed of a flexible film-like substrate, wherein the film-like substrate is bonded to a semiconductor element or another substrate via a conductive adhesive. The surface of the film-like substrate is a nitrided rough surface.

  The flexible substrate of the present invention is formed of a flexible film-like substrate and is nitrided on the surface of the film-like substrate in a flexible substrate that is bonded to a semiconductor element or another substrate via a conductive adhesive. , A functional group showing a strong bond with ACF can be formed on the surface of the substrate to improve the adhesion between the film-like substrate and the ACF. Further, since the surface of the film-like substrate is roughened during nitriding and the conductive adhesive enters the irregularities of the rough surface, the adhesion can be improved by the anchor effect of the conductive adhesive. Therefore, since the connection strength between the flexible substrate and the adherend is increased, the connection reliability can be improved.

  A first invention of the present application is a flexible substrate formed of a flexible film-like substrate, and the film-like substrate is bonded to a semiconductor element or another substrate via a conductive adhesive. The surface of the film-like substrate is nitrided to form a functional group exhibiting a strong bond with ACF on the substrate surface. Accordingly, the adhesion between the film-like substrate and the ACF can be improved. Further, since the surface of the film-like substrate is roughened during nitriding and the conductive adhesive enters the irregularities of the rough surface, the adhesion can be improved by the anchor effect of the conductive adhesive. Therefore, since the connection strength between the flexible substrate and the adherend is increased, the connection reliability can be improved.

  The second invention of the present application is characterized in that the rough surface is formed with irregularities having an arithmetic average roughness of 1.0 nm to 100 nm, and the surface is arithmetically averaged by nitriding a flexible substrate. It is formed on a rough surface having a roughness of 1.0 nm to 100 nm. By making the surface an uneven surface with an arithmetic average roughness of 1.0 nm to 100 nm, sufficient connection strength can be ensured.

  A third invention of the present application is characterized in that the film-like substrate is formed of any one of polyimide, polyester, polycarbonate, polyamide, epoxy resin, and liquid crystal polymer. As a base film, polyimide, polyester, When formed of any one of polycarbonate, polyamide, epoxy resin, and liquid crystal polymer, adhesion of carbon and other contaminants significantly reduces the connection strength of the conductive adhesive. By doing so, a flexible substrate capable of improving the connection strength can be obtained.

  According to a fourth aspect of the present invention, there is provided a flexible substrate manufacturing method in which a flexible film-like substrate is formed, and the film-like substrate is bonded to a semiconductor element or another substrate via a conductive adhesive. A step of setting a substrate in a holder of a vacuum chamber; a step of introducing a nitrogen-based gas into the vacuum chamber; and a step of nitriding the film-like substrate by decomposing the introduced nitrogen-based gas. And by nitriding the surface of the film-like substrate by decomposing nitrogen-based gas and forming a functional group showing a strong bond with ACF on the substrate surface, improving the adhesion between the film-like substrate and ACF Can do. Further, since the surface of the film-like substrate is roughened during nitriding and the conductive adhesive enters the irregularities of the rough surface, the adhesion can be improved by the anchor effect of the conductive adhesive. Therefore, since the connection strength between the substrate and another substrate is increased, this is a method for manufacturing a flexible substrate that can improve connection reliability.

  The fifth invention of the present application is characterized in that the decomposition of the nitrogen-based gas is performed by applying an electric field to the nitrogen-based gas. By doing so, it can be easily disassembled.

  The sixth invention of the present application is characterized in that the decomposition of the nitrogen-based gas is performed by heating the nitrogen-based gas, and can be easily decomposed by contacting the nitrogen-based gas with a heated filament. it can.

Seventh invention of the present application, the nitrogen-based gas is obtained by comprising at least one of N ₂ or NH _3, a nitrogen-based gas that includes at least one of N ₂ or NH ₃ , N ions or radicals.

  The configuration of the flexible substrate according to the present embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a state in which a flexible substrate and a liquid crystal display according to an embodiment of the present invention are connected. FIG. 2 is a perspective view showing a state in which the flexible substrate and the semiconductor element according to the embodiment of the present invention are connected.

  As shown in FIG. 1A, the flexible substrate 1 according to the embodiment of the present invention is connected to the LCD 3 via a conductive adhesive 4.

  The flexible substrate 1 has a substrate 2 in which a base of a film substrate is formed of polyimide. The film-like substrate can be formed of any one of polyester, polycarbonate, polyamide, epoxy resin, and liquid crystal polymer.

  On the substrate 2, a wiring pattern 2 a, a first electrode portion 2 b that is connected to a printed board that controls the LCD 3, and a second electrode portion 2 c that is connected to the LCD 3 are formed.

  The LCD 3 is obtained by enclosing a liquid crystal composition in a glass cell formed by vertically facing electrodes, at least one of which is transparent. The LCD 3 is connected to the second electrode portion 2c of the substrate 2 through a conductive adhesive 4 that is an ACF.

  The conductive adhesive 4 is formed by dispersing a large number of conductive particles in a thermosetting resin and applying the resin to a base tape. When the flexible substrate 1 and the LCD 3 are bonded using the conductive adhesive 4, the conductive adhesive 4 is adhered to the transparent electrode portion 3 a called ITO (Indium Tin Oxide) formed on the glass substrate of the LCD 3. The flexible substrate 1 and the LCD 3 are bonded together by placing the second electrode portion 2c of the substrate 2 and applying pressure by heating with a pressure head from above. A state where the flexible substrate 1 and the LCD 3 are bonded is shown in FIG.

  As shown in FIG. 2A, the flexible substrate 1 is provided with a third electrode portion 2d for mounting and connecting an IC (Integrated Circuit) 5 thereon.

  The substrate 2 and the IC 5 are bonded to each other by attaching the conductive adhesive 4 to the third electrode portion 2d of the substrate 2, placing the IC 5 on the third electrode portion 2d of the substrate 2, and applying it to the upper portion of the IC 5. The flexible substrate 1 and the IC 5 are bonded together by heating and pressing with a pressure head. FIG. 2B shows a state where the flexible substrate 1 and the IC 5 are bonded.

  The entire surface of the substrate 2 including the first electrode portion 2b, the second electrode portion 2c, and the third electrode portion 2d is roughened by nitriding. This rough surface is a surface on which irregularities having an arithmetic average roughness of 1.0 nm to 100 nm are formed.

  A method of manufacturing a flexible substrate according to the embodiment of the present invention configured as described above will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view of an apparatus used in the method for manufacturing a flexible substrate according to the embodiment of the present invention.

  As shown in FIG. 3, the vacuum chamber 11 includes a substrate holder 12 for setting a flexible substrate 17 formed of a film substrate before nitriding the surface, a high-frequency power source 13 for applying a voltage to the substrate holder 12, and a vacuum. An exhaust device 14 having an exhaust valve 15 for exhausting air in the chamber 11, a gas introduction device 16 for introducing a nitrogen-based gas into the vacuum chamber 11, and a heater 18 for heating the flexible substrate 17 are provided.

  The vacuum chamber 11 is grounded by a grounding unit 19 that is a ground level.

  Plasma can be generated by glow discharge in a vacuum chamber by a high-frequency power source 13. At that time, the substrate holder 12 generates a negative induced DC voltage of 200 to 1000V.

  The heater 18 can remove moisture adhering to the surface of the flexible substrate 17 by adjusting the degree of heating. In addition, the reaction rate of the flexible substrate 17 can be controlled.

The exhaust device 14 has a function of opening the exhaust valve 15 and exhausting the air in the vacuum chamber 11 so that the pressure is 1.0 × 10 ⁻³ Pa or less.

The gas introduction device 16 is introduced into the vacuum chamber 11 from a tank 16a that stores a nitrogen-based gas in which a gas containing either NH ₃ or N ₂ is combined as a nitrogen-based gas.

A method of nitriding the surface of the flexible substrate 17 using the vacuum chamber 11 as described above to make it rough will be described.
(1) Set the flexible substrate 17 before nitriding the surface to the substrate holder 12.
(2) The exhaust valve 15 is opened and the air in the vacuum chamber 11 is exhausted from the exhaust device 14 so that the pressure is 1.0 × 10 ⁻³ Pa or less.
(3) The flexible substrate 17 is heated by the heater 18 so that the temperature is room temperature to 300 ° C.
(4) A nitriding gas is introduced from the gas introduction device 16 into the vacuum chamber 11.
(5) A high frequency voltage is applied to the substrate holder 12 on which the flexible substrate 17 is set by the high frequency power source 13.

  By applying the high-frequency voltage, N plasma is generated in the space S1 between the flexible substrate 17 introduced into the vacuum chamber 11 and the wall surface of the vacuum chamber 11, and the nitriding gas is decomposed. At this time, a negative induced DC voltage is generated in the substrate holder 12, and N ions are attracted to the substrate holder 12.

  The attracted N ions are accelerated and collide with the flexible substrate 17. Further, N radicals generated together with N plasma diffuse and reach the flexible substrate 17. An etching reaction is generated on the surface of the film-like substrate of the flexible substrate 17 by the collision of the N ions and the N radicals reached by diffusion. By this etching reaction, a contamination layer such as carbon adhering to the surface of the flexible substrate 17 is removed. Then, after the contamination layer is removed, the polyimide forming the flexible substrate 17 is etched. The etching of the flexible substrate 17 is chemically etched by N ions and N radicals together with physical etching by collision of N ions. In the molecular structure of polyimide, there are a portion that is easily etched chemically and a portion that is difficult to etch, and the etching rate is different, so that the etching is selective etching. By this selective etching, the flexible substrate becomes a flexible substrate 1 in which irregularities having an arithmetic average roughness of 1.0 nm to 100 nm are formed on the surface and the adhesion surface is rough.

  When physical etching by plasma processing is performed using only an inert gas such as Ar gas, the surface roughness is about 0.5 nm in terms of arithmetic average roughness. If the surface roughness is an arithmetic average roughness of about 0.5 nm, sufficient connection strength cannot be obtained. In the case of chemical etching by N plasma used in the manufacturing method according to the embodiment of the present invention, the rough surface can have an arithmetic average roughness of 1.0 to 100 nm. As a result, the anchor effect of the conductive adhesive can be obtained at the time of bonding, and sufficient adhesion strength can be ensured by increasing the adhesion.

  Further, the surface of the flexible substrate 1 formed of polyimide is nitrided and modified by the N plasma that has collided and the N radicals that have arrived by diffusion, and a functional group resulting from N is formed. Since the surface of the flexible substrate 1 on which this functional group is formed has a very high affinity with the conductive adhesive, it can have high connection reliability.

  Next, the manufacturing method of the flexible substrate which concerns on other embodiment of this invention is demonstrated based on FIG. FIG. 4 is a schematic cross-sectional view of an apparatus used in a method for manufacturing a flexible substrate according to another embodiment of the present invention.

  The apparatus shown in FIG. 4 is decomposed by bringing a nitriding gas into contact with the heated filament 23 to nitride the surface of the flexible substrate. The vacuum chamber 21 has the same functions as those of the substrate holder 12, the exhaust device 14, and the gas introduction device 16 shown in FIG.

  As shown in FIG. 4, the vacuum chamber 21 includes a heater 22 that heats the flexible substrate 17, a filament 23 that thermally decomposes the introduced gas, a DC power supply 24 that supplies current to the heater 22, and a current that flows to the filament 23. And a DC power supply 25 to be supplied.

A method of nitriding the surface of the flexible substrate 17 using the vacuum chamber 21 as described above to make it rough will be described.
(1) Set the flexible substrate 17 before nitriding the surface to the substrate holder 12.
(2) The exhaust valve 15 is opened to exhaust the air in the vacuum chamber 21 from the exhaust device 14, and the pressure is set to 1.0 × 10 ⁻³ Pa or less.
(3) A current is supplied from the DC power source 24 to the heater 22 to heat the surface temperature of the flexible substrate 17 to a room temperature to 300 ° C.
(4) A nitriding gas is introduced from the gas introduction device 16 into the vacuum chamber 21.
(5) A current is supplied to the filament 23 from the DC power source 25 to heat the filament 23 to 1500 ° C. to 2000 ° C.
(5) The nitriding gas is decomposed by contact with the heated filament 23 and N radicals are generated to diffuse in the vacuum chamber 21. The diffused N radicals reach the flexible substrate 17.

  In this way, the nitrogen-based gas is decomposed by bringing it into contact with the heated filament, and by generating N radicals, the surface of the flexible substrate 17 is nitrided in the same manner as the vacuum chamber 11 shown in FIG. A rough surface having a surface roughness of 1.0 nm to 100 nm can be formed.

(Example)
A flexible substrate (invention product) having a nitrided surface was produced using the vacuum chamber 11 shown in FIG. 3, and was bonded to the glass substrate by thermocompression bonding using a conductive adhesive, and the connection strength was measured. An enlarged view of the surface of the nitrided flexible substrate is shown in FIG.

  As shown in FIG. 5, the surface of the nitrided flexible substrate is a rough surface on which irregularities having an arithmetic average roughness of about 1.0 nm to 100 nm are formed. The arithmetic average roughness was measured with Nanoscope IIIa manufactured by Digital Instruments.

  For comparison, the connection strength of the liquid crystal panel to the glass substrate is measured using a flexible substrate (conventional product 1) whose surface is not nitrided and a flexible substrate (conventional product 2) subjected to Ar plasma treatment. The same bonding conditions were used.

  The bonding conditions were a pressure of 2 MPa, a temperature of 200 ° C., and a time of 10 s.

  The connection strength was measured by peeling 90 °, and the peeling speed was 50 mm / min.

  As a result, the inventive product had a connection strength of 12.1 N / cm, whereas the conventional product 1 was 2.5 N / cm and the conventional product 2 was 5.5 N / cm.

  From the above results, it was possible to improve the connection strength by 2 to 4 times that of the conventional flexible substrate by nitriding the surface of the flexible substrate formed of the film-like substrate to make it a rough surface.

  Since the present invention can increase the connection strength with an object to be bonded, a flexible substrate formed of a flexible film-like substrate that is connected to a semiconductor element or another substrate through a conductive adhesive. Is preferred.

The perspective view which shows the state which connects the flexible substrate and liquid crystal display which concern on embodiment of this invention The perspective view which shows the state which connects the flexible substrate and semiconductor element which concern on embodiment of this invention Schematic sectional view of an apparatus used in a method for manufacturing a flexible substrate according to an embodiment of the present invention The schematic sectional drawing of the apparatus used for the manufacturing method of the flexible substrate which concerns on other embodiment of this invention. Enlarged view of the surface of a nitrided substrate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,17 Flexible substrate 2 Board | substrate 2a Wiring pattern 2b 1st electrode part 2c 2nd electrode part 2d 3rd electrode part 3 LCD
3a Transparent electrode part 4 Conductive adhesive 5 IC
DESCRIPTION OF SYMBOLS 11 Vacuum chamber 12 Substrate holder 13 High frequency power supply 14 Exhaust device 15 Exhaust valve 16 Gas introduction device 16a Tank 18 Heater 19 Grounding part 21 Vacuum chamber 22 Heater 23 Filament 24, 25 DC power supply S1 space

Claims (7)

In a flexible substrate formed of a flexible film-like substrate and bonded to the semiconductor element or other substrate via a conductive adhesive,
A flexible substrate characterized in that the surface of the film-like substrate is a nitrided rough surface. 2. The flexible substrate according to claim 1, wherein the rough surface is formed as an unevenness having an arithmetic average roughness of 1.0 nm to 100 nm. 3. The flexible substrate according to claim 1, wherein the film-like substrate is formed of any one of polyimide, polyester, polycarbonate, polyamide, epoxy resin, and liquid crystal polymer. In a method for manufacturing a flexible substrate, which is formed of a flexible film-like substrate, and the film-like substrate is bonded to a semiconductor element or another substrate via a conductive adhesive.
Setting the film-like substrate in a vacuum chamber holder;
Introducing a nitrogen-based gas into the vacuum chamber;
And a step of decomposing the introduced nitrogen-based gas and nitriding the film-like substrate. The method for manufacturing a flexible substrate according to claim 4, wherein the decomposition of the nitrogen-based gas is performed by applying an electric field to the nitrogen-based gas. The method for manufacturing a flexible substrate according to claim 4, wherein the decomposition of the nitrogen-based gas is performed by heating the nitrogen-based gas. The method for manufacturing a flexible substrate according to claim 4, wherein the nitrogen-based gas contains at least one of N _{2 and} NH ₃ .

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