JP2010050271A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain a stable adhesion state of a pad formed by a metallic fine particle to a board. <P>SOLUTION: A circuit board 1 includes: a circuit pattern 3 formed by printing on a substrate 2 comprising an insulating material and including a wiring part 3b and a pad 3a connected to the wiring part 3b and having an area greater than that of the wiring part 3b; and a cover coat layer comprising an adhesive material contacting with a pad 3a and the wiring part 3b, and formed by printing at the part all over the circumferential periphery of the circuit pattern as thinner than the pad 3a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit board for forming a circuit without a mask.

  2. Description of the Related Art Conventionally, a circuit board manufacturing technique using an ink jet apparatus is known as a technique for forming a circuit without using a mask, which is environmentally friendly (see, for example, Non-Patent Document 1).

  This technique forms a circuit board by dispersing metal fine particles having a diameter on the order of nm in a solvent and printing a circuit pattern on the board using an ink jet apparatus.

In the conventional technique of forming a circuit pattern on a substrate by printing using an inkjet device, if the printing is not performed after preparing the surface state of the substrate in advance, the ink spreads out so that a precise circuit pattern cannot be formed. There is an inconvenience of disconnection or short circuit. For this reason, a liquid repellent surface treatment such as fluorine-based molecules is performed on the surface of the substrate.
Katsuaki Kakinuma, “Inkjet fine wiring of metal nanoparticle paste”, CMC Publishing Co., Ltd., March 2006

  However, when a circuit pattern is formed on a substrate surface that has been subjected to a liquid-repellent surface treatment by printing using an inkjet apparatus, there is a problem that the adhesion between the circuit pattern and the substrate becomes unstable.

  In particular, in order to facilitate the contact of the inspection probe, in the pad portion formed so as to have a larger area than the wiring portion, or in the pad portion where the mounting component is mounted, if the temperature change occurs during use, the substrate Since the thermal expansion coefficient differs between this material and the material constituting the circuit pattern, there may be a problem that the material peels off from the substrate.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a circuit board, a manufacturing method thereof, and an electronic apparatus that can stably maintain a pad portion in an adhesive state on the board. .

  In order to achieve the above object, the present invention provides the following means.

The present invention includes a circuit pattern including a wiring portion formed by printing on a substrate and a pad portion connected to the wiring portion and having a larger area than the wiring portion,
Provided is a circuit board which is thinner than the circuit pattern and on which a cover coat layer is formed over the entire periphery of the circuit pattern.

  According to the present invention, the cover coat layer printed so as to cover the periphery of the circuit pattern formed by printing on the substrate is configured to suppress peeling of the circuit pattern, and the edge of the circuit pattern is formed by the cover coat layer. Is maintained in an adhesive state so as not to peel from the substrate. Thereby, peeling of a circuit pattern can be prevented without performing special surface treatment on the surface of the substrate. Further, since the cover coat layer covers the periphery of the pad portion, the upper surface of the pad is not covered with the cover coat layer, so that the continuity test can be easily performed by contacting the test probe. Further, when the pad portion becomes a mounting portion with the board mounting component, the area of the upper surface of the pad portion is ensured, so that it is easy to obtain a strong bond between the circuit board and the component.

In the above invention, the cover coat layer may be formed to be thinner than the pad portion and to cover the entire periphery of the circuit pattern.
By doing in this way, it becomes a structure which covers a wiring part and becomes a structure in which multilayer wiring is possible.

In the invention described above, a cover coat layer may be formed that covers a convex lower portion of the pad portion, is thinner than the thickness of the pad portion, and covers the entire circumference of the periphery of the circuit pattern.
By doing in this way, it becomes a structure which can raise the adhesiveness with a board | substrate more firmly about the pad part with a large area.

In the said invention, the structure where the cross-sectional structure of the said pad part is concave shape may be sufficient.
By doing in this way, since an inspection probe contacts a concave shape, it becomes easy to inspect. Further, when mounting a component, the electrodes and bumps of the mounted component can be fitted, and alignment at the pad portion becomes possible.

In the above invention, the cover coat layer may be made of an epoxy resin thin film.
By doing in this way, the thin film made from an epoxy resin with high adhesiveness can be formed by printing, and peeling of a circuit pattern can be prevented more reliably.

  According to the present invention, it is possible to stably maintain the adhesion state between the circuit pattern and the substrate while securing the area of the pad portion.

  Hereinafter, a circuit board 1 according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the circuit board 1 according to the present embodiment includes a substrate 2 made of an insulating material, a circuit pattern 3 made of a conductive material formed on the surface of the substrate 2, and a peripheral edge of the circuit pattern 3. And a cover coat layer 4 in contact with a portion over the entire circumference.

  The substrate 2 is made of a plastic film such as glass, quartz glass, or polyimide, or a metal plate whose surface is covered with an insulator. Further, the substrate 2 has heat resistance that is not deformed by a temperature (for example, 120 ° C. to 200 ° C.) during sintering of metal fine particles contained in the ink described later. The surface of the substrate 2 is subjected to surface treatment by adsorbing fluorine-based molecules.

  Specifically, for example, after performing plasma treatment at Ar 10 mL / min, 500 W for 30 seconds, a fluorine film diluted to a concentration of 25 to 75% is applied with a dropper, and the surface treatment is performed by heat treatment at 80 ° C. for 30 minutes. Done.

  The circuit pattern 3 is drawn by ink jet printing in which fine droplets of ink containing metal fine particles are ejected onto the substrate 2 by an ink jet device, and then heated in a reducing atmosphere at 120 ° C. for 1 hour, for example. Is formed in an adhesive state on the substrate 2.

  Examples of the metal fine particles include those containing any of gold, silver, copper, palladium, and nickel, and oxides thereof.

  The particle size of the metal fine particles is preferably 1 nm or more and 100 nm or less. If it is larger than 100 nm, the nozzles of the ink jet apparatus may be clogged. On the other hand, if the thickness is smaller than 1 nm, the volume ratio of the dispersion medium to the metal fine particles is increased, so that the ratio of organic substances in the obtained circuit pattern 3 is excessive.

  The dispersion medium is not particularly limited as long as it can disperse the metal fine particles and does not cause aggregation. For example, in addition to water, alcohols such as methanol, ethanol, propanol, butanol, n-heptane, n-octane, decane, dodecane, tetradecane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydro Hydrocarbon compounds such as naphthalene and cyclohexylbenzene, 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, ether compounds such as p-dioxane, propylene carbonate, γ- Butyrolactone, N- methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, can be exemplified polar compounds such as cyclohexanone.

  Of these, water, alcohols, hydrocarbon compounds, and ether compounds are preferable from the viewpoints of particle dispersibility, dispersion stability, and ease of application in an inkjet apparatus, and more preferable dispersion media are , Water, and hydrocarbon compounds.

  1 shows one pad portion 3a and one wiring portion 3b, the actual circuit pattern 3 includes a large number of wiring portions 3b connected to terminals of electronic components (not shown), A pad portion 3a having a relatively large area connected to one end of the wiring portion 3b is formed. For example, the wiring portion 3b is formed in a square shape having a width of about 100 μm and the pad portion 3a having a side of about 1 mm.

  The cover coat layer 4 is formed in a thin film shape made of an epoxy resin. After the circuit pattern 3 is formed on the substrate 2 by sintering the metal fine particles, the cover coat layer 4 is printed with an epoxy resin so as to be in contact with the circuit pattern 3 by an inkjet device, and is irradiated with ultraviolet rays almost simultaneously. It is formed by.

  Specifically, for example, after performing plasma treatment at Ar 10 mL / min, 500 W for 30 seconds, printing is performed by spraying droplets of epoxy resin with an inkjet apparatus while heating to 80 ° C.

  As shown in FIG. 2, since the upper surface of the pad portion 3a is not covered with the cover coat layer 4, the central portion can be kept exposed in a square shape with one side of 1 mm.

  Further, as shown in FIG. 3, the cover coat layer 4 is formed on the substrate 2 with a width of about 50 μm from the periphery of the pad portion 3a to the outside.

  According to the circuit board 1 according to the present embodiment configured as described above, the circuit pattern 3 is covered with the cover coat layer 4 at the peripheral portion of the circuit pattern 3, so that the circuit pattern is formed by the cover coat layer 4 made of an adhesive epoxy resin. 3 is held so as not to peel from the substrate 2.

  That is, even if an internal stress or the like due to thermal expansion or contraction occurs, the peripheral edge of the circuit pattern 3 is adhered to the substrate 2 by the cover coat layer 4 over the entire periphery, so that peeling that tends to occur from the peripheral edge is effectively performed. It can be suppressed.

  As a result, the surface of the substrate 2 can be subjected to a liquid-repellent surface treatment to form a fine circuit pattern 3 and can be stably and stably prevented from peeling without reducing the area of the pad portion 3a. There is an advantage that the inspection can be performed.

  Moreover, in this embodiment, as shown in FIGS. 4-6, even if the circuit pattern 3 is formed so that the thickness of the pad part 3a and the thickness of the wiring part 3b may differ, the cover coat layer 4 may be formed after that. Good. By doing in this way, since almost the whole wiring part 3b is also coat | covered with the cover coat layer 4, peeling of the wiring part 3b can be suppressed more strongly and generation | occurrence | production of inconveniences, such as a disconnection, can be prevented beforehand. . Further, although not shown in the drawing, since the cover coat layer 4 is insulating, the wiring portion 3b is formed on the cover coat layer 4 so that a multilayer structure is possible.

  Furthermore, in this embodiment, after forming the pad part 3a as shown in FIG. 7, the cover coat layer 4 may be formed as shown in FIG. By doing so, the cross section of the pad portion has the structure shown in FIG. 9, and it becomes possible to more firmly suppress peeling and to perform a durable and stable inspection.

In the present embodiment, the structure of the pad portion 3a shown in FIGS. 4 and 8 may be the structure shown in FIGS. By doing in this way, since an inspection probe contacts a concave shape, it becomes easy to inspect.
In addition, the description has been made on the assumption that the pad portion 3a is in contact with the inspection probe, but by reducing the size of the pad portion 3, it can be replaced with the structure of the mounting portion of the mounted component. That is, in the structure shown in FIG. 10 or FIG. 11, when mounting components are mounted by the pad portion 3a, the electrodes and bumps of the mounting components can be fitted, and alignment at the pad portion becomes possible. It becomes a structure.

  Although the circuit board 1 according to the present embodiment is not shown, the circuit board 1 may be adopted as an internal board of an electronic device such as a stopwatch, a clock, or a metronome. In this case, the circuit board 1 is used during maintenance. An inspection probe can be brought into contact with the pad portion 3a provided on the substrate 3 to conduct a continuity test. Further, since the pad portion 3a is prevented from being peeled off from the substrate 2, a durable and stable inspection can be performed.

It is a perspective view showing a part of circuit board concerning one embodiment of the present invention. It is AA 'sectional drawing of FIG. FIG. 2 is a cross-sectional view taken along the line BB ′ of FIG. It is a perspective view showing a part of circuit board concerning one embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line AA ′ of FIG. FIG. 5 is a cross-sectional view taken along the line BB ′ of FIG. It is a perspective view which shows a part of circuit board before providing a cover-coat layer. It is a perspective view showing a part of circuit board concerning one embodiment of the present invention. It is AA 'sectional drawing of FIG. It is a perspective view showing a part of circuit board concerning one embodiment of the present invention. It is a perspective view showing a part of circuit board concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Board | substrate 3 Circuit pattern 3a Pad part 3b Wiring part 4 Cover coat layer

Claims (6)

A circuit pattern formed by printing on a substrate, including a wiring portion and a pad portion connected to the wiring portion and having a larger area than the wiring portion;
A circuit board having a cover coat layer that is thinner than a thickness of the circuit pattern and is formed over the entire periphery of the circuit pattern. The circuit pattern formed on the substrate by printing, including the wiring portion and the pad portion connected to the wiring portion and having a larger area than the wiring portion;
A circuit board on which the cover coat layer is formed over the entire circumference of the periphery of the circuit pattern, being thinner than the pad portion. The circuit pattern formed on the substrate by printing, including the pad portion connected to the wiring portion and the wiring portion and having a convex cross-sectional shape having a larger area than the wiring portion;
A circuit board that covers a lower portion of the pad portion having a convex shape, is thinner than the thickness of the pad portion, and on which the cover coat layer is formed over the entire periphery of the circuit pattern. The circuit pattern formed on the substrate by printing, including the wiring portion and the pad portion connected to the wiring portion and having a larger area than the wiring portion;
A circuit board that is thinner than the pad portion and includes the cover coat layer over the entire periphery of the circuit pattern, and the pad portion has a concave cross-sectional structure.   The circuit board according to any one of claims 1 to 4, wherein the cover coat layer is an adhesive material formed by printing.   The circuit board according to claim 1, wherein the cover coat layer is made of an epoxy resin thin film.

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