JP2006095381A - Film forming method, wiring pattern forming method, wiring pattern, electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method suitable for forming a substantially circular or substantially elliptical film.
The liquid droplets are arranged on a predetermined region (1-9) so that the liquid droplets partially overlap each other while the liquid droplets disposed on the substrate 31 have fluidity.
[Selection] Figure 9

Description

  The present invention relates to a film forming method, a wiring pattern forming method, a wiring pattern, and an electronic device.

  For example, a lithography method is used to form a wiring pattern constituting an electronic device. However, the lithography method requires not only a large equipment such as a vacuum apparatus and a complicated process, but also has a material use efficiency of about several percent, so that most of the material must be discarded, and the manufacturing cost is high. Furthermore, there is a limit to the miniaturization of the wiring pattern.

Therefore, as a process replacing the lithography method, a method (droplet discharge method) in which a liquid containing a functional material is discharged onto a substrate and a wiring pattern is directly drawn and formed has been studied. In this method, first, a liquid in which conductive fine particles are dispersed is discharged from a droplet discharge head onto a substrate to form a liquid line. Next, the liquid line is baked by heat treatment or laser irradiation to form a wiring pattern (see, for example, Patent Document 1). According to this droplet discharge method, the manufacturing process is simplified and the material use efficiency is high, so that the manufacturing cost can be reduced. In addition, it is easy to realize finer wiring patterns.
US Pat. No. 5,132,248

  In order to reduce the size of electronic devices, it is important to increase the number of layers as well as the wiring pattern. In order to increase the number of wiring patterns, electrical wirings are stacked and disposed via an interlayer insulating film, and the upper and lower electrical wirings are electrically connected by conductive posts.

  The conductive post described above needs to be formed at a considerable height so as to penetrate the interlayer insulating film. In this case, it is desirable that the cross-sectional shape of the conductive post has smooth corners in order to ensure structural or thermal strength. Specifically, the cross section of the film constituting the conductive post is preferably substantially circular (or substantially elliptical).

  In order to form a film having a substantially circular cross section using the droplet discharge method, a method of arranging a plurality of minute amounts of droplets in a substantially circular shape is conceivable. However, this method may cause a reduction in productivity because the number of droplet discharges increases.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a film forming method suitable for forming a substantially circular or substantially elliptical film.
Another object of the present invention is to provide a wiring pattern forming method suitable for forming a conductive post.
Another object of the present invention is to provide a wiring pattern and an electronic apparatus having excellent electrical connection reliability.

  In order to achieve the above object, a film forming method of the present invention is a method of forming a film on a substrate by placing a liquid material in droplets on the substrate, the film forming method being disposed on the substrate. While the droplets have fluidity, the droplets are arranged in a predetermined area so that the droplets partially overlap each other.

  According to this method, while the droplets have fluidity, the droplets are arranged so as to partially overlap each other with respect to a predetermined region, and thus the droplets are connected to each other due to an action such as surface tension. Integrated. At the time of this integration, the outer shape of the film becomes curved, and formation of sharp corners is avoided. In addition, it is possible to form a film in an arbitrary shape by arranging a plurality of droplets partially overlapping each other instead of arranging them all at the same place. Further, by utilizing the connection between the droplets, the number of droplet discharges can be reduced and the design of the droplet arrangement position can be facilitated.

In the above film forming method, the overlapping of the droplets is preferably 10% or more of the diameter of one droplet after landing on the substrate.
Thereby, the droplets are more reliably connected to each other and integrated.

Furthermore, in the above-described film forming method, it is preferable that the predetermined region is within a range in which droplets partially overlapping on the substrate approach each other due to surface tension.
Also by this, the droplets are more reliably connected to each other and integrated.

In the film forming method, the predetermined area may be a substantially rectangular area, for example.
In this case, even if the droplet arrangement is a substantially rectangular region, the droplets are arranged so as to partially overlap each other, whereby the droplets are connected to each other to form a substantially circular or elliptical film. . In this case, it is relatively easy to dispose droplets in a substantially rectangular area, and the number of droplet ejections can be reduced and the design of the droplet arrangement position can be facilitated.

  Furthermore, since the predetermined region is a substantially square region, the droplets are connected to each other to form a substantially circular film.

In the film forming method, a plurality of unit regions partitioned in a lattice shape for determining the droplet discharge position are set on the substrate, and the predetermined region is formed of the plurality of unit regions. Of these, it is preferable to have an area of n rows × n columns (n is a positive integer).
As a result, the arrangement area of the droplets becomes a substantially square shape, and the droplets are connected to each other to form a substantially circular film. The arrangement of droplets in n rows × n columns (n is a positive integer) is relatively easy, and the design thereof is also easy.

The wiring pattern forming method of the present invention is a method for forming a wiring pattern in which a plurality of electrical wirings stacked on a substrate are connected to each other by a plurality of conductive posts, and uses the film forming method described above. And the step of forming the conductive post.
According to this method, since the conductive posts having smooth corners are formed, it is possible to provide a wiring pattern having excellent electrical connection reliability. In addition, since the droplet discharge method is adopted, a miniaturized wiring pattern can be provided.

The wiring pattern of the present invention is formed by using the wiring pattern forming method described above.
This wiring pattern has excellent electrical connection reliability.

An electronic apparatus according to the present invention includes the above wiring pattern.
According to this electronic device, since the electrical connection reliability is excellent and the miniaturized wiring pattern is provided, a small electronic device excellent in electrical connection reliability can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

  FIG. 1 is an exploded perspective view of a liquid crystal module having a COF (Chip On Film) structure. In this embodiment, a method for forming a wiring pattern on a flexible printed circuit board (Flexible Printed Circuit; hereinafter referred to as “FPC”) 30 will be described as an example. The FPC 30 is obtained by forming electrical wiring patterns 39a and 39b on the surface of a flexible film substrate 31. As will be described in detail later, in the liquid crystal module 1 having the COF structure shown in FIG. 1, the FPC 30 is connected to the end of the liquid crystal panel 2, and the liquid crystal driving IC 100 is mounted on the surface of the FPC 30. An image is displayed on the liquid crystal panel 2 by outputting a drive signal from the liquid crystal drive IC 100 to the liquid crystal panel 2 via the FPC 30.

[Wiring pattern]
FIG. 2 is an explanatory diagram of a wiring pattern according to the embodiment, and is an enlarged view of a wiring formation portion of the FPC. 2A is a plan sectional view taken along line BB in FIG. 2B, and FIG. 2B is a side sectional view taken along line AA in FIG. As shown in FIG. 2B, the wiring pattern of the present embodiment has a configuration in which a lower-layer electrical wiring 32 and an upper-layer electrical wiring 36 are stacked with an interlayer insulating film 54 interposed therebetween. Note that the wiring patterns described below are merely examples, and the present invention can be applied to other wiring patterns.

  As shown in FIG. 2B, the FPC 30 includes a flexible film substrate 31 made of polyimide or the like. A base insulating film 51 is formed on the surface of the film substrate 31. The base insulating film 51 is made of an electrically insulating material obtained by mixing an ultraviolet curable resin such as acrylic and a thermosetting resin such as epoxy.

  A plurality of electrical wirings 32 are formed on the surface of the base insulating film 51. The electrical wiring 32 is formed in a predetermined pattern using a conductive material such as Ag. An in-layer insulating film 52 is formed in a region where the electric wiring 32 is not formed on the surface of the base insulating film 51. Then, by adopting a droplet discharge method which will be described later, the line × space of the electric wiring 32 is made finer, for example, to about 30 μm × 30 μm.

  An interlayer insulating film 54 is formed so as to mainly cover the electrical wiring 32. This interlayer insulating film 54 is also made of the same resin material as that of the base insulating film 51. A conductive post 34 having a considerably high height is formed so as to penetrate the interlayer insulating film 54 from a part of the electric wiring 32. The conductive post 34 is formed in a cylindrical shape by the same conductive material such as Ag as the electric wiring 32. For example, the thickness of the electric wiring 32 is about 2 μm, and the height of the conductive post 34 is about 8 μm.

  An upper electrical wiring 36 is formed on the surface of the interlayer insulating film 54. Similarly to the lower-layer electrical wiring 32, the upper-layer electrical wiring 36 is also made of a conductive material such as Ag. As shown in FIG. 2A, the upper-layer electrical wiring 36 may be arranged so as to intersect with the lower-layer electrical wiring 32. The upper-layer electrical wiring 36 is connected to the upper end portion of the conduction post 34 to ensure electrical continuity with the lower-layer electrical wiring 32.

  Further, as shown in FIG. 2B, an in-layer insulating film 56 is formed in a region where the electrical wiring 36 is not formed on the surface of the interlayer insulating film 54. Further, a protective film 58 is formed so as to mainly cover the electrical wiring 36. The in-layer insulating film 56 and the protective film 58 are also made of the same resin material as that of the base insulating film 51.

  The wiring pattern provided with two layers of electrical wirings 32 and 36 has been described above as an example. However, a wiring pattern including three or more layers of electrical wiring may be used. In this case, similarly to the structure from the first-layer electrical wiring 32 to the second-layer electrical wiring 36, the n-th layer electrical wiring to the (n + 1) th-layer electrical wiring may be formed.

[Method of forming wiring pattern]
Next, a method for forming a wiring pattern according to the embodiment will be described.
FIG. 3 is a process chart of a wiring pattern forming method according to the embodiment. 4 and 5 are explanatory diagrams of the method for forming a wiring pattern according to the embodiment. Below, each process is demonstrated in order of the step number of the left end column of FIG.

  First, the surface of the film substrate 31 shown in FIG. 2B is cleaned (step 1). Specifically, the surface of the film substrate 31 is irradiated with excimer UV having a wavelength of 172 nm for about 300 seconds. The film substrate 31 may be washed with a solvent such as water, or may be washed using ultrasonic waves. Alternatively, the film substrate 31 may be cleaned by irradiating with plasma at normal pressure.

Next, as a premise for forming the base insulating film 51 on the surface of the film substrate 31, a bank (peripheral portion) of the base insulating film 51 is drawn and formed (step 2). This drawing is performed by a droplet discharge method (inkjet method). That is, a resin material before curing, which is a material for forming the base insulating film 51, is discharged along the peripheral edge of the region where the base insulating film 51 is formed using a droplet discharge device described later.
Next, the discharged resin material is cured (step 3). Specifically, UV with a wavelength of 365 nm is irradiated for about 4 seconds to cure the UV curable resin that is the material for forming the base insulating film 51. Thereby, a bank is formed at the peripheral edge of the formation region of the base insulating film 51.

Next, the base insulating film 51 is drawn and formed inside the formed bank (step 4). This drawing is also performed by a droplet discharge method. Specifically, a resin material before curing, which is a material for forming the base insulating film 51, is discharged from the droplet discharge head while scanning a droplet discharge head of a droplet discharge device, which will be described later, over the entire bank. Here, even if the discharged resin material flows, the resin material is dammed by the bank of the peripheral portion, so that it does not spread beyond the formation region of the base insulating film 51.
Next, the discharged resin material is cured (step 5). Specifically, UV with a wavelength of 365 nm is irradiated for about 60 seconds to cure the UV curable resin that is the material for forming the base insulating film 51. As a result, a base insulating film 51 is formed on the surface of the film substrate 31 as shown in FIG.

  Next, as a premise for forming the electric wiring 32 on the surface of the base insulating film 51, the contact angle of the surface of the base insulating film 51 is adjusted (step 6). As will be described below, when a droplet containing the material for forming the electrical wiring 32 is ejected, if the contact angle of the surface of the base insulating film 51 is too large, the ejected droplet becomes a ball and is placed at a predetermined position. It becomes difficult to form electrical wiring of a predetermined shape. On the other hand, if the contact angle on the surface of the base insulating film 51 is too small, the discharged droplets spread and the electrical wiring becomes difficult to miniaturize. Since the surface of the cured base insulating film 51 exhibits liquid repellency, the contact angle of the surface of the base insulating film 51 is adjusted by irradiating the surface with excimer UV having a wavelength of 172 nm for about 15 seconds. The degree of relaxation of liquid repellency can be adjusted by the irradiation time of ultraviolet light, but can also be adjusted by a combination with the intensity of ultraviolet light, wavelength, heat treatment (heating), and the like. Note that other methods of lyophilic treatment include plasma treatment using oxygen as a reactive gas and treatment of exposing a substrate to an ozone atmosphere.

  Next, as shown in FIG. 4B, a liquid line 32p to be an electrical wiring later is drawn and formed on the surface of the base insulating film 51 (step 7a). This drawing is performed by a droplet discharge method using a droplet discharge device described later. What is discharged here is a dispersion liquid in which conductive fine particles, which are materials for forming electrical wiring, are dispersed in a dispersion medium. Silver is preferably used as the conductive fine particles. In addition, fine particles of conductive polymer or superconductor can be used in addition to metal fine particles containing any of gold, copper, palladium, and nickel.

  The conductive fine particles can be used by coating the surface with an organic substance or the like in order to improve dispersibility. Examples of the coating material that coats the surface of the conductive fine particles include polymers that induce steric hindrance and electrostatic repulsion. The particle diameter of the conductive fine particles is preferably 5 nm or more and 0.1 μm or less. If it is larger than 0.1 μm, nozzle clogging is likely to occur and ejection by the droplet ejection head becomes difficult. On the other hand, if the thickness is smaller than 5 nm, the volume ratio of the coating agent to the conductive fine particles is increased, and the ratio of organic substances in the obtained conductor is excessive.

  The dispersion medium to be used is not particularly limited as long as it can disperse the above-mentioned conductive fine particles and does not cause aggregation. In addition to water, alcohols such as methanol, ethanol, propanol and butanol, n- Hydrocarbon compounds such as heptane, n-octane, decane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydronaphthalene, cyclohexylbenzene, or ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl Ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether Le, p- ether compounds such as dioxane, propylene carbonate, .gamma.-butyrolactone, N- methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, may be mentioned polar compounds such as cyclohexanone. Among these, water, alcohols, hydrocarbon compounds, and ether compounds are preferable and particularly preferable from the viewpoints of fine particle dispersibility, dispersion stability, and ease of application to the droplet discharge method. Examples of the dispersion medium include water and hydrocarbon compounds. These dispersion media can be used alone or as a mixture of two or more.

The liquid dispersion medium containing conductive fine particles preferably has a vapor pressure at room temperature of 0.001 mmHg or more and 200 mmHg or less (about 0.133 Pa or more and 26600 Pa or less). This is because when the vapor pressure is higher than 200 mmHg, the dispersion medium rapidly evaporates after ejection, and it becomes difficult to form a good conductor.
The vapor pressure of the dispersion medium is more preferably 0.001 mmHg or more and 50 mmHg or less (about 0.133 Pa or more and 6650 Pa or less). This is because when the vapor pressure is higher than 50 mmHg, nozzle clogging due to drying tends to occur when droplets are ejected by the droplet ejection method, and stable ejection becomes difficult. On the other hand, in the case of a dispersion medium having a vapor pressure lower than 0.001 mmHg at room temperature, drying becomes slow and the dispersion medium tends to remain in the conductor, and a high-quality conductor can be obtained after heat and / or light treatment in the subsequent process. It's hard to be done.

  The dispersoid concentration when the conductive fine particles are dispersed in the dispersion medium is 1% by mass or more and 80% by mass or less, and can be adjusted according to the desired thickness of the conductor. If it exceeds 80% by mass, aggregation tends to occur and it is difficult to obtain a uniform conductor.

The surface tension of the conductive fine particle dispersion is preferably in the range of 0.02 N / m to 0.07 N / m. When the liquid is discharged by the droplet discharge method, if the surface tension is less than 0.02 N / m, the wettability of the ink composition with respect to the nozzle surface increases, and thus flight bending easily occurs, resulting in 0.07 N / m. This is because the shape of the meniscus at the tip of the nozzle is not stable, and it becomes difficult to control the discharge amount and the discharge timing.
In order to adjust the surface tension, a trace amount of a surface tension regulator such as fluorine, silicon, or nonion can be added to the dispersion liquid in a range that does not unduly reduce the contact angle with the base insulating film 51. . The nonionic surface tension modifier improves the wettability to the base insulating film 51, improves the leveling property of the film, and helps prevent the occurrence of coating crushing and the generation of distorted skin. The dispersion liquid may contain an organic compound such as alcohol, ether, ester, or ketone as necessary.

The viscosity of the dispersion is preferably 1 mPa · s or more and 50 mPa · s or less.
When discharging with the droplet discharge method, if the viscosity is less than 1 mPa · s, the nozzle periphery is easily contaminated by the outflow of the ink, and if the viscosity is more than 50 mPa · s, the nozzle hole has an eye. This is because clogging frequency increases and it becomes difficult to smoothly discharge droplets.

In the present embodiment, the dispersion liquid droplets (first droplets) are ejected from a droplet ejection head and dropped onto a location where an electrical wiring is to be formed. At this time, it is desirable to adjust the overlapping degree of the liquid droplets to be continuously discharged so that the liquid pool (bulge) does not occur. In particular, it is desirable to employ a discharge method in which a plurality of liquid droplets are discharged separately so as not to contact each other in the first discharge, and the gap is filled by the second and subsequent discharges.
As a result, the liquid line 32 p is formed on the surface of the base insulating film 51.

  Next, the liquid line 32p is temporarily dried (step 7b). This temporary drying is performed so that at least the surface of the liquid line 32p is dried. Specifically, dry air such as air with low humidity or inert gas is blown toward the liquid line 32p. The temperature of the dry air may be normal temperature (about 25 ° C.) or high temperature. Further, instead of blowing dry air, the liquid line 32p may be irradiated with infrared rays using an infrared lamp or the like. As described above, by adopting dry air spraying or infrared irradiation as a specific method of temporary drying, temporary drying can be performed with simple manufacturing equipment and manufacturing processes. Can be suppressed. Moreover, even if the temperature rises temporarily due to temporary drying, it can be immediately returned to room temperature, so that the manufacturing time can be shortened.

  Next, as shown in FIG. 4C, a liquid sub-post 34a to be a conductive post is drawn and formed on a part of the temporarily dried liquid line 32p (step 8a). Similar to the drawing of the liquid line 32p in step 7a, this drawing is also performed by a droplet discharge method using a droplet discharge device described later. Here, the liquid droplets (second liquid droplets) in which the conductive fine particles, which are the material for forming the conductive posts, are dispersed in the dispersion medium are discharged. Specifically, the liquid droplets are used for drawing the liquid line 32p. It is the same as the body droplet (first droplet). That is, after the liquid line 32p is drawn, the liquid material may be discharged to the conductive post formation position using the same droplet discharge head.

  As described above, the conductive post needs to be formed at a considerable height. For this purpose, it is necessary to eject and deposit a large number of droplets by a droplet ejection method to form a liquid post having a considerably high height. However, it is difficult to secure the height of the liquid post even if a large number of droplets are ejected at one time, and conversely, the diameter of the liquid post becomes large and may cause a short circuit with an adjacent electrical wiring or conduction post. There is. Therefore, the liquid droplets are discharged in a plurality of times. In one droplet discharge, a liquid sub-post lower than the required liquid post height is formed. For example, about 10 droplets are discharged at a time, and first the liquid sub-post 34a of the first layer is drawn and formed.

  Next, the liquid sub-post 34a is temporarily dried (step 8b). This temporary drying is performed so that at least the surface of the liquid sub-post 34a is dried. As a specific method thereof, it is desirable to employ dry air spraying or infrared irradiation similarly to the method of temporarily drying the liquid line in step 7b.

  Thereafter, Step 8a and Step 8b are repeated (Step 9). As described above, since the liquid sub-post 34a of the first layer is temporarily dried, it does not spread on the surface of the base insulating film 51 even if a new droplet is ejected onto the surface. Therefore, if about 10 droplets are newly ejected, the second liquid sub-post 34b can be stacked above the first liquid sub-post 34a as shown in FIG. 5A. In this way, by repeating Step 8a and Step 8b, a plurality of liquid sub-posts 34a, 34b, 34c can be stacked to form a liquid post 34p having a corresponding height.

Here, FIG. 6 schematically shows an example of a state in which droplets are discharged onto the surface of the substrate (film substrate 31).
As shown in FIG. 6, in this example, a plurality of nozzles are moved while relatively moving a droplet discharge head (hereinafter simply referred to as a head) 20 having a plurality of nozzles 91 and a substrate 31 in a predetermined direction (Y direction). A droplet is ejected from a predetermined nozzle 91 and the droplet is placed on the substrate 31.

  On the substrate 31, a bitmap made up of a plurality of unit areas (pixels) partitioned in a grid pattern for determining the droplet discharge position is set. The bitmap setting process is performed prior to the droplet discharge process.

  As shown in FIG. 6, one pixel (unit area) is set to a square. That is, the width cx in the X direction and the width cy in the Y direction of one pixel are set to be the same.

  The plurality of nozzles 91 are provided at regular intervals a in the X direction in the head 20. Each of the plurality of nozzles 91 is arranged along the X direction.

Here, in this example, the pixel width cx (= cy) is set narrower than the nozzle interval a. When setting a bitmap,
The width cx of one pixel in the X direction is set so that c = a / n (n is a positive integer).
In the example of FIG. 6, n = 4.

  For example, a linear coating film (liquid line) can be formed by disposing droplets for each of the hatched pixels shown in FIG. In this case, the droplets may be arranged one by one with respect to a plurality of pixels arranged in the relative movement direction (Y direction), or the step of arranging the droplets with a predetermined interval may be repeated. In addition, by disposing the droplets with a predetermined interval, it is possible to suppress excessive wetting and spreading of the liquid material and to prevent the so-called bulge.

  The degree of wetting and spreading when the droplet is placed on the substrate 31, that is, the diameter of the droplet immediately after landing on the substrate 31 varies depending on the liquid material and the characteristics of the substrate surface. When forming the wiring pattern, the pattern design is performed in consideration of the wet spread of the droplet. Further, the degree of wetting and spreading of the droplets on the substrate 31 is deeply related to the contact angle between the substrate 31 and the droplets. For this reason, the substrate 31 is subjected to surface treatment including lyophilic treatment and liquid repellent treatment according to the characteristics of the liquid material, and the contact angle is controlled, so that wetting and spreading of the droplet (diameter of the droplet after landing). Can be controlled.

FIG. 7 schematically shows an example of a state in which droplets are ejected when the conductive post 34 (see FIG. 5A) is formed.
Reference numerals P1 and P2 shown in FIG. 7 indicate the positions where the conductive posts are formed. Further, the widths cx and cy of one pixel (unit region) in the bitmap, the intervals a of the plurality of nozzles 91, and the like are the same as those in FIG.

As shown in FIG. 7, in this example, the interval b between the post formation positions P1 and P2 is set wider than the nozzle interval a. More specifically,
The post interval b and the width cx (= cy) in the X direction of one pixel are set so that b = m × a (m is a positive integer).
In the example of FIG. 7, m = 16.

  For example, by repeating the step of disposing droplets and the step of temporarily drying the droplets for each of the post formation positions P1 and P2 shown in FIG. As shown in FIG. 5A, the post 34 having a considerably high height can be formed in a stacked manner.

  Here, according to this example, since the interval b between the formation positions P1 and P2 of the plurality of conductive posts is an integral multiple of the interval a between the plurality of nozzles 91, the droplet discharge process can be simplified. It is done. That is, if the conductive post formation position P1 is arranged on the movement axis of one of the plurality of nozzles 91 when the head 20 and the substrate 31 are moved relative to each other under the above conditions, the other nozzles Since the conductive post formation position P2 is also arranged on the movement axis, a droplet can be arranged at each of the plurality of conductive post formation positions P1 and P2 during one relative movement. As a result, there is little waste in the relative movement, and the droplet discharge process can be simplified.

  In particular, when forming the conductive posts, since the droplets are repeatedly arranged at the respective formation positions P1 and P2 in order to obtain a considerable height, the relative movement between the head 20 and the substrate 31 is less wasteful. An increase in processing time associated with repeated ejection is suppressed. Thereby, the throughput can be improved and the cost of the formed wiring pattern can be reduced.

  6 and 7 are merely examples, and the present invention is not limited to this. 6 and 7, the width of the liquid line and the size of the conductive post are made to correspond to only one column in the X direction for simplification of description. Actually, the liquid line width and the size of the conductive post can be set to a desired state by disposing the droplets on the adjacent pixels in a plurality of columns (a plurality of columns in the X direction).

  6 and 7 are merely examples, and the present invention is not limited to this. In FIG. 6 and FIG. 7, the width of the liquid line and the size of the conductive post are made to correspond to only one column in the X direction for the sake of simplicity of explanation. Actually, the liquid line width and the size of the conductive post can be set to a desired state by disposing the droplets on adjacent pixels in a plurality of columns (a plurality of columns in the X direction).

  FIG. 8 schematically shows a more specific example of the arrangement of droplets when the conductive post 34 (see FIG. 5A) is formed.

  As shown in FIG. 8, in this example, when forming the conductive posts, droplets are arranged for each of the nine pixels on which numerals are written. That is, in this example, droplets are arranged in a substantially square area of 3 rows × 3 columns. In addition, the number in each pixel shows the order of arrangement | positioning of a droplet.

  That is, first, a droplet is placed on pixel 1 and then a droplet is placed on pixel 2. Similarly, droplets are arranged in order from pixel 1 to pixel 9. Droplet placement from pixel 1 to pixel 9 is performed while each droplet placed on the substrate has fluidity. That is, the liquid droplets are arranged for the nine pixels within a predetermined time determined from the drying speed of the liquid droplets without performing temporary drying in the middle. The order in which the droplets are arranged can be changed as appropriate.

  8 indicate the shape of the droplet L1 immediately after landing on the pixel 1 and the shape of the droplet L2 immediately after landing on the pixel 2, respectively. In this example, the diameter (landing diameter) of the droplets L1 and L2 after landing is about three times the width of one pixel. Therefore, the droplet L1 and the droplet L2 are arranged so that the width of 1/3 of the landing diameter overlaps each other.

FIG. 9 virtually shows the state of overlapping of droplets when the droplets are arranged from pixel 1 to pixel 9.
As shown in FIG. 9, in this example, the droplets are arranged for each of the nine pixels so that the droplets partially overlap each other.

FIG. 10 shows a state after a predetermined time elapses when droplets are arranged in nine pixels.
As shown in FIG. 10, the liquid droplets arranged on the pixels 1 to 9 become a substantially circular coating film S1. In other words, while the droplets have fluidity, the droplets are arranged so as to partially overlap each other with respect to nine pixels, so that the droplets are connected to each other and integrated by an action such as surface tension. The During the integration, the droplets aggregate and the outer shape of the aggregate of the droplets becomes a smooth curved shape. In this example, since the liquid droplets are arranged in a 3 × 3 square area, a substantially circular coating film is formed.

  As described above, in this example, a substantially circular coating film can be obtained by utilizing the connection between the droplets even though the droplets are arranged in a substantially square region. That is, the need to set a fine bitmap to avoid a circular film is avoided. As a result, the number of droplet discharges can be reduced, and the design of the droplet arrangement position (pattern design) can be facilitated.

  In addition, a substantially cylindrical conductive post 34 (FIG. 5A) can be formed by laminating and forming circular coating films. The substantially cylindrical conductive post 34 has smooth corners, high structural or thermal strength, and excellent electrical connection reliability.

  Since the overlap between the droplets is 10% or more of the landing diameter, the droplets are more reliably connected to each other and integrated. It should be noted that a plurality of droplets are not arranged in the same place all over (that is, 100% overlaid), but a plurality of droplets are arranged in a partially overlapping manner to form a film in an arbitrary shape. Can be formed. That is, a substantially elliptical film can be formed by setting the droplet arrangement region to a substantially rectangular shape.

  For example, the droplet arrangement region is not limited to 3 rows × 3 columns, but may be 2 rows × 2 columns, 4 rows × 4 columns, or 2 rows × 4 columns. However, if the droplet placement region is too wide, the droplets may not be sufficiently combined. Therefore, the droplet placement region is such that the partially overlapped droplets on the substrate 31 approach each other due to surface tension. It is preferable to be within the range.

  Returning to FIG. 5A, next, the main firing of the liquid line 32p and the liquid post 34p is performed (step 10). As described above, since the liquid line 32p and the liquid sub-posts 34a, 34b, and 34c are all formed in a preliminarily dried state, the entirety thereof is subjected to main firing. Specifically, the film substrate 31 on which the liquid line 32p and the liquid post 34p are formed is heated by a hot plate at 150 ° C. for about 30 minutes.

  Although the main calcination is usually performed in the air, it can also be performed in an inert gas atmosphere such as nitrogen, argon, or helium as necessary. In addition, although the processing temperature of this baking was 150 degreeC, heat | fever, such as the boiling point (vapor pressure) of the dispersion medium contained in the liquid line 32p and the liquid post 34p, the kind and pressure of atmospheric gas, and the dispersibility and oxidation nature of microparticles | fine-particles It is desirable to set appropriately considering the mechanical behavior, the presence or absence and amount of the coating material, the heat-resistant temperature of the substrate, and the like.

  Such a baking process can be performed by lamp annealing in addition to a process using a normal hot plate, an electric furnace, or the like. The light source used for lamp annealing is not particularly limited, but excimer laser such as infrared lamp, xenon lamp, YAG laser, argon laser, carbon dioxide laser, XeF, XeCl, XeBr, KrF, KrCl, ArF, ArCl, etc. Can be used as a light source. These light sources generally have a power output in the range of 10 W or more and 5000 W or less, but in this embodiment, a range of 100 W or more and 1000 W or less is sufficient.

  By such main firing, the dispersion medium contained in the liquid line 32p and the liquid post 34p is volatilized, and electrical contact between the conductive fine particles is ensured. Thereby, as shown in FIG.5 (b), the electrical wiring 32 and the conduction | electrical_connection post 34 are formed.

  Next, as shown in FIG. 2B, the contact angle of the surface of the base insulating film 51 is adjusted on the premise that the in-layer insulating film 52 is formed in the formation layer of the electrical wiring 32 (step 11). Since the surface of the cured base insulating film 51 exhibits liquid repellency, excimer UV with a wavelength of 172 nm is irradiated to impart lyophilicity to the surface.

  Next, the in-layer insulating film 52 is drawn and formed around the electrical wiring 32 (step 12). This drawing is also performed using a droplet discharge device in the same manner as the drawing of the base insulating film 51. Here, when the resin material, which is a material for forming the in-layer insulating film 52, is discharged so as to come into contact with the conductive posts 34, the resin material wets the upper ends of the conductive posts 34 and is electrically connected to the electrical wiring 36 in the upper layer. May become impossible. Therefore, a gap is formed around the conductive posts 34 and the electrical wiring 32, and the resin material is discharged to the outside.

Next, an excimer UV having a wavelength of 172 nm is applied to the gap around the conductive post 34 and the electric wiring 32 to perform lyophilic treatment (step 13). As a result, lyophilicity is imparted to the gap around the conductive post 34 and the electric wiring 32, and the resin material flows into the gap and comes into contact with the conductive post 34 and the electric wiring 32. In this case, the resin material wets the surface of the electrical wiring 32, but does not wet the upper end of the conductive post 34. Therefore, it is possible to ensure electrical continuity between the conductive post 34 and the upper-layer electrical wiring 36.
Then, the discharged resin material is cured (step 14). Specifically, UV with a wavelength of 365 nm is irradiated for about 4 seconds to cure the UV curable resin that is the material for forming the in-layer insulating film 52. Thereby, the in-layer insulating film 52 is formed.

Next, the interlayer insulating film 54 is drawn and formed mainly on the surface of the electric wiring 32 (step 15). This drawing is also performed using a droplet discharge device in the same manner as the drawing of the base insulating film 51. Also here, it is desirable to discharge the resin material with a gap around the conductive post 34.
Next, the discharged resin material is cured (step 16). Specifically, UV with a wavelength of 365 nm is irradiated for about 60 seconds to cure the UV curable resin that is the material for forming the interlayer insulating film 54. Thereby, the interlayer insulating film 54 is formed.

Next, an upper electrical wiring 36 is formed on the surface of the interlayer insulating film 54. The specific method is the same as Step 6 to Step 10 for forming the lower-layer electric wiring 32.
Next, an in-layer insulating film 56 is formed on the formation layer of the electrical wiring 36. The specific method is the same as Step 11 to Step 14 for forming the in-layer insulating film 52 in the formation layer of the electric wiring 32. Furthermore, if Step 15 and Step 16 are performed, an interlayer insulating film can be formed on the surface of the upper electrical wiring 36.

Thus, by repeating Step 6 to Step 16, the electrical wiring can be arranged in a stacked manner. A protective film 58 may be formed on the surface of the uppermost electrical wiring by the same method as in Step 15 and Step 16.
As described above, the wiring pattern of this embodiment shown in FIG. 2 is formed.

  As described above, in the wiring pattern forming method of this embodiment, a step of drawing and forming a liquid line by a droplet discharge method (step 7a), a step of temporarily drying the surface of the liquid line (step 7b), The liquid post is drawn and formed on a part of the liquid line by the droplet discharge method (Step 8a), and the liquid line and the liquid post are subjected to main firing (Step 10). According to this configuration, since the liquid post is drawn and formed on the surface of the liquid line in the temporarily dried state, both can be fused at the interface. And an electrical wiring and a conduction | electrical_connection post can be integrally formed by carrying out the main baking of a liquid line and a liquid post collectively. As a result, it is possible to prevent the occurrence of cracks at the interface between the electric wiring and the conductive post, and it is possible to form a wiring pattern having excellent reliability of the conductive connection.

  In the wiring pattern forming method of the present embodiment, the liquid sub-post is drawn and formed by the droplet discharge method (step 8a), the liquid sub-post is temporarily dried (step 8b), step 8a and step 8b. And the step of repeatedly firing (step 9) and the step of subjecting the liquid subposts arranged in layers to the main firing (step 10). According to this configuration, the formation of the liquid sub-post by droplet discharge and the temporary drying thereof are repeatedly performed, so that the liquid droplets can be stacked and arranged without the discharged droplet being wet spread on the plane. Then, by conducting the main firing of the liquid sub-posts stacked and arranged in a temporarily dried state, a conductive post having a considerably high height can be formed.

  In addition, since the method for forming a wiring pattern according to the present embodiment employs a droplet discharge method for forming electric wiring, conductive posts, and various insulating films, it is possible to improve material use efficiency and reduce manufacturing costs. can do. Furthermore, the electrical wiring can be multilayered and miniaturized. For example, the line × space width of a plurality of electrical wirings can be reduced from the conventional 50 μm × 50 μm to about 30 μm × 30 μm. As a result, the FPC can be miniaturized, and the electro-optical device and electronic apparatus that employ the FPC can be miniaturized.

  In the present embodiment, the wiring pattern forming method in the FPC has been described as an example, but the present invention can also be applied as a wiring pattern forming method in a hard substrate. In the present embodiment, the case where the conductive post is formed on the electric wiring has been described. However, the case where the conductive post is formed on the electrode land of the electric wiring is also included in the technical scope of the present invention.

(Droplet discharge device)
Next, a droplet discharge apparatus used for the droplet discharge method will be described with reference to FIGS.
FIG. 11 is a perspective view of the droplet discharge device. In FIG. 11, the X direction is the left-right direction of the base 12, the Y direction is the front-rear direction, and the Z direction is the up-down direction. The droplet discharge device 10 mainly includes a droplet discharge head (hereinafter simply referred to as a head) 20 and a table 46 on which a substrate 31 is placed. The operation of the droplet discharge device 10 is controlled by the control device 23.

  The table 46 on which the substrate 31 is placed can be moved and positioned in the Y direction by the first moving means 14, and can be swung and positioned in the θz direction by the motor 44. On the other hand, the head 20 can be moved and positioned in the X direction by the second moving means, and can be moved and positioned in the Z direction by the linear motor 62. The head 20 can be swung and positioned in the α, β, and γ directions by motors 64, 66, and 68, respectively. Accordingly, the droplet discharge device 10 can accurately control the relative position and posture between the ink discharge surface 20P of the head 20 and the substrate 31 on the table 46.

  Here, a structural example of the head 20 will be described with reference to FIG. FIG. 12 is a side sectional view of the droplet discharge head. The head 20 discharges the ink 21 from the nozzle 91 by a droplet discharge method. Various known technologies such as a piezo method in which ink is ejected using a piezoelectric element as a piezoelectric element, and a method in which ink is ejected by bubbles generated by heating the ink are applied as a droplet ejection method. can do. Of these, the piezo method has the advantage that it does not affect the composition of the material because it does not apply heat to the ink. Therefore, the above-described piezo method is adopted for the head 20 in FIG.

  A head body 90 of the head 20 is formed with a reservoir 95 and a plurality of ink chambers 93 branched from the reservoir 95. The reservoir 95 is a flow path for supplying ink to each ink chamber 93. A nozzle plate that constitutes an ink ejection surface is attached to the lower end surface of the head main body 90. In the nozzle plate, a plurality of nozzles 91 for discharging ink are opened corresponding to the respective ink chambers 93. An ink flow path is formed from each ink chamber 93 toward the corresponding nozzle 91. On the other hand, a diaphragm 94 is attached to the upper end surface of the head main body 90. The diaphragm 94 constitutes a wall surface of each ink chamber 93. Piezo elements 92 are provided outside the diaphragm 94 so as to correspond to the ink chambers 93. The piezo element 92 is obtained by sandwiching a piezoelectric material such as quartz with a pair of electrodes (not shown). The pair of electrodes is connected to the drive circuit 99.

  When a voltage is applied from the drive circuit 99 to the piezo element 92, the piezo element 92 expands or contracts. When the piezo element 92 contracts and deforms, the pressure in the ink chamber 93 decreases, and the ink 21 flows from the reservoir 95 into the ink chamber 93. When the piezo element 92 expands and deforms, the pressure in the ink chamber 93 increases and the ink 21 is ejected from the nozzle 91. Note that the amount of deformation of the piezo element 92 can be controlled by changing the applied voltage. Further, the deformation speed of the piezo element 92 can be controlled by changing the frequency of the applied voltage. That is, by controlling the voltage applied to the piezo element 92, the ejection conditions of the ink 21 can be controlled.

  The capping unit 22 shown in FIG. 11 is for capping the ink ejection surface 20P when the droplet ejection apparatus 10 is on standby to prevent the ink ejection surface 20P of the head 20 from drying. The cleaning unit 24 sucks the inside of the nozzles in order to remove clogging of the nozzles in the head 20. The cleaning unit 24 can also wipe the ink discharge surface 20P in order to remove dirt on the ink discharge surface 20P in the head 20.

(Electro-optical device)
In the present embodiment, the wiring pattern formed on the FPC has been described as an example. Returning to FIG. 1, a liquid crystal module as an example of an electro-optical device employing the FPC will be described.
FIG. 1 is an exploded perspective view of a liquid crystal module having a COF (Chip On Film) structure. The liquid crystal module 1 roughly includes a color display liquid crystal panel 2, an FPC 30 connected to the liquid crystal panel 2, and a liquid crystal driving IC 100 mounted on the FPC 30. Note that an illumination device such as a backlight and other auxiliary devices are attached to the liquid crystal panel 2 as necessary.

  The liquid crystal panel 2 has a pair of substrates 5a and 5b bonded by a sealing material 4, and liquid crystal is sealed in a so-called cell gap formed between the substrates 5b and 5b. In other words, the liquid crystal is sandwiched between the substrate 5a and the substrate 5b. These substrates 5a and 5b are generally formed of a translucent material such as glass or synthetic resin. A polarizing plate 6a is attached to the outer surfaces of the substrate 5a and the substrate 5b.

  An electrode 7a is formed on the inner surface of the substrate 5a, and an electrode 7b is formed on the inner surface of the substrate 5b. These electrodes 7a and 7b are formed of a light-transmitting material such as ITO (Indium Tin Oxide). The substrate 5a has a projecting portion that projects from the substrate 5b, and a plurality of terminals 8 are formed on the projecting portion. These terminals 8 are formed simultaneously with the electrodes 7a when the electrodes 7a are formed on the substrate 5a. Accordingly, these terminals 8 are made of, for example, ITO. These terminals 8 include one that extends integrally from the electrode 7a and one that is connected to the electrode 7b via a conductive material (not shown).

  On the other hand, wiring patterns 39a and 39b are formed on the surface of the FPC 30 by the wiring pattern forming method according to the present embodiment. That is, an input wiring pattern 39a is formed from one short side to the center of the FPC 30, and an output wiring pattern 39b is formed from the other short side to the center. Electrode pads (not shown) are formed at the ends on the center side of the input wiring pattern 39a and the output wiring pattern 39b.

  A liquid crystal driving IC 100 is mounted on the surface of the FPC 30. Specifically, a plurality of bump electrodes formed on the active surface of the liquid crystal driving IC 100 with respect to a plurality of electrode pads formed on the surface of the FPC 30 are ACF (Anisotropic Conductive Film) 160. Connected through. The ACF 160 is formed by dispersing a large number of conductive particles in a thermoplastic or thermosetting adhesive resin. As described above, the so-called COF structure is realized by mounting the liquid crystal driving IC 100 on the surface of the FPC 30.

  The FPC 30 including the liquid crystal driving IC 100 is connected to the substrate 5 a of the liquid crystal panel 2. Specifically, the output wiring pattern 39b of the FPC 30 is electrically connected to the terminal 8 of the substrate 5a via the ACF 140. Since the FPC 30 has flexibility, it can be space-saving by freely folding it.

  In the liquid crystal module 1 configured as described above, a signal is input to the liquid crystal driving IC 100 via the input wiring pattern 39 a of the FPC 30. Then, a driving signal is output from the liquid crystal driving IC 100 to the liquid crystal panel 2 via the output wiring pattern 39b of the FPC 30. As a result, an image is displayed on the liquid crystal panel 2.

  Note that examples of the electro-optical device include a device having an electro-optic effect that changes the light transmittance by changing the refractive index of a substance by an electric field, and a device that converts electric energy into optical energy. That is, the present invention is not limited to a liquid crystal display device, but an organic EL (Electro-Luminescence) device, an inorganic EL device, a plasma display device, an electrophoretic display device, and a display device using an electron-emitting device (Field Emission Display and Surface- It can also be widely applied to light emitting devices such as Conduction Electron-Emitter Display. For example, an organic EL module can be configured by connecting an FPC having the wiring pattern of the present invention to an organic EL panel.

[Electronics]
Next, an electronic device manufactured using the wiring pattern of this embodiment will be described with reference to FIG. FIG. 13 is a perspective view of a mobile phone. In FIG. 13, reference numeral 1000 denotes a mobile phone, and reference numeral 1001 denotes a display unit. The display unit 1001 of the cellular phone 1000 employs an electro-optical device having the wiring pattern of the present embodiment. Therefore, it is possible to provide a small mobile phone 1000 with excellent electrical connection reliability.
The present invention is not limited to the above mobile phone, but is an electronic book, personal computer, digital still camera, liquid crystal television, viewfinder type or monitor direct-view type video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, work It can be suitably used as an image display means for electronic devices such as stations, videophones, POS terminals, touch panels, etc. In any case, a small electronic device with excellent electrical connection reliability can be provided.

  The technical scope of the present invention is not limited to the above-described embodiments, and includes various modifications made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.

It is a disassembled perspective view of the liquid crystal module of a COF structure. It is explanatory drawing of the wiring pattern which concerns on embodiment. It is a process chart of the formation method of the wiring pattern concerning an embodiment. It is explanatory drawing of the formation method of the wiring pattern which concerns on embodiment. It is explanatory drawing of the formation method of the wiring pattern which concerns on embodiment. It is a figure which shows typically an example of a mode that a droplet is discharged to the surface of a board | substrate. It is a figure which shows typically an example of a mode that the droplet at the time of forming a conduction | electrical_connection post is discharged. It is a figure which shows typically the example of arrangement | positioning of the more specific droplet at the time of forming a conduction | electrical_connection post. It is a figure which shows virtually the mode of overlap of the droplets at the time of arrange | positioning a droplet to nine pixels. It is a figure which shows the mode after predetermined time progress which has arrange | positioned the droplet to nine pixels. It is a perspective view of a droplet discharge device. It is side surface sectional drawing of a droplet discharge head. It is a perspective view of a mobile phone.

Explanation of symbols

L1, L2 ... droplet, 20 ... droplet discharge head, 31 ... film substrate (substrate), 32 ... electric wiring, 32p ... liquid line, 34 ... conduction post, 34p ... liquid post, 36 ... electric wiring, 91 ... nozzle .

Claims (9)

A method of forming a film on the substrate by disposing a liquid material as droplets on the substrate,
A method of forming a film, wherein the droplets are arranged in a predetermined region so that the droplets partially overlap each other while the droplets arranged on the substrate have fluidity.   The film forming method according to claim 1, wherein the overlapping of the droplets is 10% or more of a diameter of one droplet after landing on the substrate.   3. The film forming method according to claim 1, wherein the predetermined region is within a range in which droplets partially overlapping on the substrate approach each other due to surface tension.   The film forming method according to claim 1, wherein the predetermined area is a substantially rectangular area.   The film forming method according to claim 4, wherein the predetermined region is a substantially square region. On the substrate, a plurality of unit areas partitioned in a lattice shape for determining the discharge position of the droplets are set,
The film forming method according to claim 5, wherein the predetermined region is a region of n rows × n columns (n is a positive integer) among the plurality of unit regions. A method of forming a wiring pattern in which a plurality of electrical wirings stacked on a substrate are connected to each other by a plurality of conductive posts,
7. A wiring pattern forming method comprising the step of forming the conductive post using the film forming method according to claim 1.   A wiring pattern formed by using the wiring pattern forming method according to claim 7. An electronic apparatus comprising the wiring pattern according to claim 8.

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