JP2009252772A - Circuit pattern forming method and circuit pattern substrate for etching - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit pattern forming method using an ink resist as an etching mask when a comparatively thick metal plate is etched to form a circuit pattern. <P>SOLUTION: The circuit pattern forming method includes: the steps of forming an aluminum film 11 on a ceramic substrate 10; printing a first ink resist 12 on the aluminum film; curing the first ink resist by irradiating it with an ultraviolet ray; printing a second ink resist 13 on the first ink resist; curing the second ink resist by irradiating it with an ultraviolet ray; and etching the aluminum film with an etching liquid while using the first and second ink resists 12, 13 as masks. Thus, the circuit pattern 11a consisting of the aluminum film is formed on the ceramic substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit pattern forming method and an etching circuit pattern substrate, and more particularly, to form a circuit pattern using an ink resist as an etching mask even when a relatively thick metal plate is etched to form a circuit pattern. The present invention relates to a method and an etching circuit pattern substrate.

A conventional circuit pattern forming method will be described.
An aluminum film is bonded onto the surface of the ceramic substrate by a molten metal bonding method, and an ink resist is screen-printed on the aluminum film in a circuit pattern shape. Next, the printed ink resist is cured by irradiating the ink resist with ultraviolet rays. Next, the aluminum film is etched using the cured ink resist as a mask. Specifically, the aluminum film is etched away by spraying and supplying an etching solution to the aluminum film using the ink resist as a mask. Thereafter, the ink resist is peeled off. As a result, a circuit pattern made of an aluminum film is formed on the ceramic substrate (see, for example, Patent Document 1).

JP 2006-161158 (paragraph 0022 and FIG. 1)

  If a metal plate such as a relatively thick aluminum film is to be etched using the conventional circuit pattern forming method, it is necessary to increase the etching time, for example. When the etching time is lengthened, the side surface of the circuit pattern is removed by side etching of the aluminum film. Since the ink resist is in a floating state in the removed portion, the ink resist in the floating state is destroyed by the impact (spray pressure) of the etching solution. Since the progress of etching changes between the part to be destroyed and the part not to be destroyed, as a result, the circuit pattern is rattling. When an attempt is made to etch a relatively thick metal plate in this way, the strength of the ink resist with respect to the spray pressure of the etching solution is insufficient, so that the circuit pattern formed by the etching has pattern defects and poor dimensional accuracy. Therefore, when a circuit pattern is formed by etching a relatively thick metal plate, it is necessary to use a resist made of a laminate film having high strength.

  However, a resist using a laminate film is more expensive than an ink resist. Therefore, it is required to use a low-cost resist forming method even when a circuit pattern is formed by etching a relatively thick metal plate.

  The present invention has been made in consideration of the above circumstances, and its purpose is to provide a circuit pattern using an ink resist as an etching mask even when a circuit pattern is formed by etching a relatively thick metal plate. And a circuit pattern substrate for etching.

In order to solve the above problems, a circuit pattern forming method according to the present invention includes a step of forming a metal plate on a substrate,
Printing a first ink resist on the metal plate;
Curing the first ink resist by irradiating the first ink resist with ultraviolet rays;
Printing a second ink resist on the first ink resist;
Curing the second ink resist by irradiating the second ink resist with ultraviolet rays;
Forming a circuit pattern made of the metal plate on the substrate by etching the metal plate with an etchant using the first and second ink resists as a mask;
It is characterized by comprising.

  In the circuit pattern forming method according to the present invention, it is preferable that the first ink resist has a thickness of 8 μm to 18 μm, and the second ink resist has a thickness of 8 μm to 18 μm. The thickness of the ink resist here is a thickness measured after UV curing.

The circuit pattern substrate for etching according to the present invention includes a metal plate formed on the substrate,
A first ink resist formed on the metal plate;
A second ink resist having substantially the same shape as the first ink resist formed on the first ink resist;
It is characterized by comprising.

  As described above, according to the present invention, there is provided a circuit pattern forming method using an ink resist as an etching mask and an etching circuit pattern substrate even when a circuit pattern is formed by etching a relatively thick metal plate. can do.

Embodiments of the present invention will be described below with reference to the drawings.
1A to 1D are cross-sectional views illustrating a circuit pattern forming method according to an embodiment of the present invention.

  First, as shown in FIG. 1A, for example, an aluminum nitride (AlN) substrate is prepared as the ceramic substrate 10, and the aluminum film 11 is bonded to the front and back surfaces of the ceramic substrate 10 by a molten metal bonding method. In this embodiment, an aluminum nitride substrate is used as the ceramic substrate 10. However, other ceramic substrates such as an alumina substrate and a silicon nitride substrate can also be used. In this embodiment, an aluminum film is used as the metal plate. However, other metal plates such as an Al alloy plate and a copper plate can also be used. In the present embodiment, the molten metal bonding method is used, but other bonding methods such as brazing or direct bonding can also be used.

  Next, the first ink resist 12 is screen-printed in a circuit pattern shape on one surface of the aluminum film 11, and the first ink resist 12 is formed in a solid pattern shape on the other surface (almost leaving the outer peripheral edge of the ceramic substrate). Screen printing on the entire surface. More specifically, a screen plate (not shown) in which an emulsion is applied to a mesh # 300 Tetron with a thickness of 10 μm and an opening pattern is formed thereon is prepared, and this screen plate is used to form on the aluminum film 11. A first ink resist 12 having a thickness of 8 μm to 18 μm is screen-printed. As a result, a first ink resist 12 having a circuit pattern shape is formed on the aluminum film 11. In this embodiment, the ink resist is formed by screen printing. However, the ink resist may be formed by other printing methods such as pad printing or copying printing.

Next, the first ink resist 12 is cured by irradiating the first ink resist 12 with ultraviolet light having a UV light amount of 1800 J / cm ² .

  Next, as shown in FIG. 1B, the second ink resist 13 having a thickness of 8 μm or more and 18 μm or less is screen-printed on the first ink resist 12 using the screen plate. As a result, the second ink resist 13 having the same pattern shape as the first ink resist 12 is formed on the first ink resist 12. Note that the first and second ink resists may be printing UV inks (ultraviolet curable inks) that are generally commercially available for printed circuits. The component is typically based on polyester acrylate, epoxy acrylate, urethane acrylate, and the like, and contains a photopolymerizable resin, a photopolymerization initiator, and the like.

Next, the second ink resist 13 is cured by irradiating the second ink resist 13 with ultraviolet rays having a UV light amount of 1800 J / cm ² . As a result, an ink resist having a thickness of 16 μm or more and 36 μm or less formed of the first and second ink resists 12 and 13 is formed on the aluminum film 11.

  Thereafter, as shown in FIG. 1C, the aluminum film 11 is etched using the first and second ink resists 12 and 13 as a mask. Specifically, the aluminum film 11 is etched away by spraying and supplying an etching solution such as an iron chloride solution to the aluminum film 11 using the first and second ink resists 12 and 13 as a mask. . Next, as shown in FIG. 1D, the first and second ink resists 12 and 13 are stripped with, for example, an aqueous sodium hydroxide solution. As a result, a circuit pattern 11 a and a solid pattern 11 b made of an aluminum film are formed on the ceramic substrate 10. FIG. 2 is a perspective view of FIG.

  As described above, the lower limit of the thickness of each of the first and second ink resists 12 and 13 is set to 8 μm. If the thickness is less than 8 μm, a pinhole is generated in each of the first and second ink resists 12 and 13. In other words, the strength of the ink resist after curing (strength against the impact of the spray pressure of the etching solution) is insufficient, and the circuit pattern 11a is chipped due to peeling of the ink resist. Further, the upper limit of the thickness of each of the first and second ink resists 12 and 13 is set to 18 μm. If the thickness is larger than 18 μm, the printed ink resist bleeds, thereby causing defective etching dimensions, that is, a circuit pattern. This is because a dimensional defect 11a occurs.

  According to the above embodiment, the first ink resist 12 is printed and cured by ultraviolet irradiation, and the second ink resist 13 is printed and cured by ultraviolet irradiation. A metal plate such as a relatively thick aluminum film (for example, a film thickness of 0.3 to 1.0 mm, preferably 0.3 to 0.8 mm) that could not be realized by printing can be etched with low cost and high accuracy. .

Specifically, in the conventional one-time printing of the ink resist, even if the ink resist is printed with a thickness of about 20 μm and cured by irradiating the ink resist with ultraviolet light having a UV light amount of 1800 J / cm ² , The ink resist is partially broken due to insufficient strength of the resist with respect to the spray pressure of the etching solution, and the resist cannot be etched with high accuracy, resulting in a defective circuit pattern.
On the other hand, in the present embodiment, the first ink resist 12 having a thickness of 8 μm or more and 18 μm or less is printed, cured by ultraviolet irradiation, and the second ink resist 13 having a thickness of 8 μm or more and 18 μm or less is printed. When cured by ultraviolet irradiation, the strength of the first and second ink resists 12 and 13 with respect to the spray pressure of the etching liquid is improved, and the ink resist is prevented from being peeled off during etching, and the etching can be performed with high accuracy. Occurrence of pattern dimension defects can be suppressed. The reason for this is considered to be that the strength of the etching solution against the spray pressure is improved because the formation of two layers of ink resist requires the starting point of destruction in each layer (two layers).

FIG. 3 is an enlarged cross-sectional view of a part of FIG. 1C, showing the state of the ink resist between the circuit patterns 11a. Although the side surfaces of the first and second ink resists 12 and 13 are substantially perpendicular to the ceramic substrate 10, the etched aluminum film is characterized in that the side surfaces are arcuate as shown in FIG. It is. In particular, the smaller the distance L between the ink resists, that is, between the circuit patterns, the easier it is to form an arc shape, and when the etching progressed in the thickness direction of the aluminum film, the first ink resist 12 was in contact before the etching. Etching proceeds to the surface of the aluminum film 11 to form portions where the first and second ink resists 12 and 13 are in a floating state (lengths l ₁ and l _{2 of the} portions). If a portion of the ink resist in the floating state is chipped due to the spray pressure of the etching solution, etching accuracy may be deteriorated or the circuit pattern may be chipped. Strength is important.

An experiment for forming a circuit pattern by the same method as in the embodiment was conducted. The experimental conditions at this time are as follows. The thickness of the ink resist was determined from the difference between the thickness of the aluminum nitride substrate and the metal ceramic substrate made of the aluminum film before the ink resist formation and after the ink resist formation / UV curing, measured with a micrometer.
First ink resist thickness: 10 μm
Second ink resist thickness: 10 μm
UV light quantity: 1800 J / cm ²
Aluminum film: Pure aluminum (4N)
Aluminum film thickness: 0.3 mm
Etching solution: Ferric chloride aqueous solution

  The results of the experiment are shown in Table 1.

  As shown in Table 1, Samples 1 to 8 were prepared, and the distance between circuit patterns after etching of each of Examples 1 to 8 was measured. As a result, it was confirmed that all the samples in Examples 1 to 8 were within the dimensional target value of the inter-pattern distance. At the same time, it was also confirmed that all the samples in Examples 1 to 8 had no chipped circuit pattern and no rattling (waving) of the linear portion of the pattern.

  In addition, an experiment similar to the above experiment was performed by changing only the thickness of the ink resist. That is, the case where the thickness of each of the first and second ink resists was 9 μm, 12 μm, and 15 μm was performed. As a result, it was confirmed that all samples were within the dimension target value of the inter-pattern distance and that there was no missing circuit pattern.

  Further, a sample was prepared in the same manner as in the above example except that the thickness of pure aluminum was 0.6 mm and the thickness of each of the first and second ink resists was 10 μm. Evaluation was performed in the same manner. Also at this time, it was within the dimensional target value ± 0.3 mm between the patterns. Further, as in the previous example, there was no chipping in the straight line portion of the pattern, and the straight line of the pattern was not rattled (undulated).

  Further, a comparative experiment was performed under the same conditions as the above experiment except that the thickness of each of the first and second ink resists was 20 μm. As a result, it was confirmed that bleeding occurred in the ink resist. Further, a comparative experiment was performed under the same conditions as in the above experiment except that the thickness of each of the first and second ink resists was 5 μm. As a result, the circuit pattern often has chipping and rattling.

  A sample was prepared and evaluated in the same manner as in Example except that the ink resist having a thickness of 10 μm was applied once (that is, only the first ink resist was applied and the second ink resist was not applied). In this example, the ink resist is broken in the linear part of the pattern due to the spray pressure of the etching solution, and the linear part of the Al pattern after etching is also rattled when viewed from above (non-uniform wavy line shape) It could not withstand use as a circuit pattern. Note that the rattling of the straight line portion refers to a portion that does not look visually straight but looks like a wavy line. As a specific example, there are 150 μm or more of the upper and lower parts of the wave that looks like a wavy line, and there are two or more waves that appear as a wavy line per 10 mm.

  In addition, this invention is not limited to the said embodiment and said Example, A various change can be implemented within the range which does not deviate from the main point of this invention.

(A)-(D) are sectional drawings explaining the formation method of the circuit pattern by embodiment of this invention. FIG. 2 is a perspective view of FIG. FIG. 2 is an enlarged cross-sectional view of a part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ceramic substrate 11 ... Aluminum film 11a ... Circuit pattern 12 ... 1st ink resist 13 ... 2nd ink resist

Claims (3)

Forming a metal plate on the substrate;
Printing a first ink resist on the metal plate;
Curing the first ink resist by irradiating the first ink resist with ultraviolet rays;
Printing a second ink resist on the first ink resist;
Curing the second ink resist by irradiating the second ink resist with ultraviolet rays;
Forming a circuit pattern made of the metal plate on the substrate by etching the metal plate with an etchant using the first and second ink resists as a mask;
A circuit pattern forming method comprising:   2. The circuit pattern forming method according to claim 1, wherein the first ink resist has a thickness of 8 μm to 18 μm, and the second ink resist has a thickness of 8 μm to 18 μm. A metal plate formed on the substrate;
A first ink resist formed on the metal plate;
A second ink resist having substantially the same shape as the first ink resist formed on the first ink resist;
A circuit pattern substrate for etching, comprising:

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