JP6851813B2 - Wiring board - Google Patents

Description

The present invention relates to a wiring board, particularly a wiring board provided with a metal foil circuit pattern. It also relates to a structure or the like using the wiring board.

In recent years, with the progress of miniaturization and labor saving of assembly of various electronic parts, a resin molded product having a three-dimensional shape and having a conductive circuit is required. As a method for obtaining such a structure, a flexible printed wiring board is integrally molded as an insert product (for example, Patent Document 1) or a resin molded product is plated to form a conductive circuit (for example, a patent). Reference 2) can be mentioned.

However, the elongation rate of the metal foil depends on the thickness, but it is only about 30% at the maximum, while the elongation rate of the resin film reaches several hundred percent, and there is a large difference in moldability between the two. Therefore, when a resin film having a circuit made of a metal foil formed by the technique of Patent Document 1 is used for a molded product having many undulations, the metal foil hinders the molding of the resin film, which is expected. It is not molded into the shape as it was, or the circuit cannot follow the elongation during molding and the wire breaks.

Further, in the technique of Patent Document 2, since a conductive circuit is formed by plating, it is difficult to increase the circuit thickness, and it is necessary to increase the wiring in order to reduce the electric resistance. It becomes difficult to handle. Therefore, it is difficult to apply it to products that require a large current to flow.

Japanese Unexamined Patent Publication No. 7-106733 Japanese Unexamined Patent Publication No. 2005-217156

An object of the present invention is to provide a wiring board capable of passing a large current and in which disconnection or peeling of a circuit is unlikely to occur even due to deformation due to molding.

The present inventors have found that if a wiring board has a meandering circuit pattern made of metal foil, the disconnection of the circuit can be suppressed even by deformation due to molding, and further improvements have been made to complete the present invention. It was.

The present invention includes, for example, the subjects described in the following sections.
Item 1.
A wiring board having a circuit pattern made of metal foil on at least one side of a resin board.
A part or all of the circuit pattern is a zigzag meandering circuit pattern having a structure in which linear metal leaf lines are folded in a zigzag shape in the longitudinal direction.
The metal leaf line length of the meandering circuit pattern in the range of A [mm] in the longitudinal direction of the meandering circuit pattern is defined as B [mm].
The tensile elongation at break of the resin substrate in the longitudinal direction of the meandering circuit pattern is E (resin) [%], and the elongation at tensile elongation of the metal foil is E (metal) [%].
When the 0.2% proof stress of the metal foil at room temperature is F [N / mm ² ] and the thickness is T [μm].
A wiring board that satisfies the following equations (1) and (2).
Equation (1): E (resin) / 4-E (metal) <(BA) / A × 100
Equation (2): (F × T) ≦ 22000
Item 2.
Item 2. The wiring board according to Item 1, wherein the metal foil is an aluminum foil or a copper foil.
Item 3.
Item 2. The item 1 or 2, wherein the resin substrate is a substrate containing at least one resin selected from the group consisting of polyethylene-based resin, polypropylene-based resin, polyester-based resin, acrylic-based resin, and polycarbonate-based resin. Wiring board.
Item 4.
Item 2. The wiring board according to any one of Items 1 to 3, wherein at least a part of the metal foil is coated with a protective resin.
Item 5.
Item 2. The wiring board according to any one of Items 1 to 4, wherein the metal foil is laminated on at least one surface of the resin substrate via an adhesive layer.
Item 6.
Item 2. The wiring board according to any one of Items 1 to 5, wherein a force for stretching a zigzag meandering circuit is applied in the longitudinal direction of the meandering circuit pattern.
Item 7.
Item 7. A molded processed product of a wiring board according to any one of Items 1 to 6.
Item 8.
A component comprising the wiring board according to any one of Items 1 to 6 or the molded product according to Item 7.

With the above wiring board, since the circuit is made of metal foil, it is possible to pass a large current, and by having the above configuration, the circuit cannot follow the elongation of the resin during molding and is disconnected. It is possible to reduce the possibility that the circuit will be peeled off from the resin substrate.

The longitudinal direction and the width direction of the line are shown. An example of a structure in which a metal leaf line is folded in a zigzag shape in the longitudinal direction is shown. The name of each part in the structure in which the metal leaf line is folded in a zigzag shape in the longitudinal direction is shown. , The zigzag meandering circuit pattern consists of a metal leaf line (“wiring part”) parallel to the longitudinal direction and the perpendicular direction of the meandering circuit pattern, and a metal leaf line (“connection part”) connecting the wiring parts. It can be configured, and examples thereof are shown. An example of a zigzag meandering circuit pattern is shown. An example of a zigzag meandering circuit pattern is shown. The zigzag meandering pattern circuit of the aluminum foil created in the Example is shown. The blue part indicates the wiring part, and the red part indicates the connection part. The outline of the molding process performed in the examples is shown. When a wiring board (film) having a zigzag meandering circuit pattern and a linear circuit pattern made of various metal foils is bent, a disconnection occurs in the linear circuit pattern (red arrow), but a disconnection occurs in the meandering circuit pattern. Indicates that there is no such thing. In the wiring board having a circuit pattern manufactured by using a metal foil having an F × T of more than 22000 in the formula (2), the metal foil cannot follow the deformation of the resin substrate when the substrate is molded, and the resin substrate. Indicates that problems such as unnatural deformation or peeling of the metal foil from the resin substrate occur.

Hereinafter, each embodiment of the present invention will be described in more detail.

The wiring board included in the present invention is a wiring board having a circuit pattern made of a metal foil on at least one side (one side or both sides) of the resin board.

The resin substrate is a substrate containing a resin. The shape is not particularly limited, and it is preferable that the shape is easily deformed by molding (flexible substrate). For example, a sheet-shaped or film-shaped resin substrate can be preferably used. The thickness of the resin substrate is not particularly limited as long as the effects of the present invention are not impaired, but for example, it is preferably 20 to 300 μm, more preferably 40 to 200 μm, and even more preferably 50 to 150 μm. If the resin substrate is too thin, the strength of the molded product manufactured using the substrate may decrease. On the other hand, if it is too thick, the moldability will be hindered and the cost will increase.

The resin contained in the resin substrate is not particularly limited, and for example, polyethylene-based resin, polypropylene-based resin, polyester-based resin, polyamide (nylon) -based resin, acrylic-based resin, polyvinyl chloride-based resin, polystyrene-based resin, and polychloride. Examples thereof include vinylidene resin, ethylene-vinyl acetate copolymer saponified product, polyvinyl alcohol resin, polycarbonate resin, polyvinyl acetate resin, acetal resin and the like. Among these, polyethylene-based resins, polypropylene-based resins, polyester-based resins, acrylic resins, and polycarbonate-based resins are preferable because of the ease of molding. These resins can be used alone or in combination of two or more. Further, the resin substrate preferably contains a resin as a main component (for example, 50, 60, 70, 80, 90, or 95% or more by mass), and is made of a resin (that is, made of 100% resin). Is even more preferable.

The resin layer substrate may be composed of a plurality of layers, and may be, for example, a stack of a plurality of the above resin films and resin sheets.

The metal foil may be any metal foil having conductivity and satisfying "F × T ≦ 22000" in the above formula 2. Although not particularly limited, it is preferably F × T ≦ 20000, more preferably F × T ≦ 18000, further preferably F × T ≦ 16000, still more preferably F × T ≦ 14000, still more preferably F × T ≦ 13000. is there. Examples of such a metal foil include an aluminum foil and a copper foil. The thickness of the metal foil is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 5 to 140 μm, more preferably 10 to 120 μm, still more preferably 20 to 100 μm, for example. The 0.2% proof stress of the metal foil at room temperature (25 ° C.), F [N / mm ² ], is a value measured by JIS Z 2241.

More specific examples of the preferred aluminum foil include soft and hard materials such as 1030, 1N30, 1050, 1100, 8021, and 8079 with the JIS (AA) symbol. Among these, 1N30, 8021, and 8079 soft materials are more preferable from the viewpoint of workability. Further, when these specific aluminum foils are used, the thickness thereof is preferably the thickness of the above-mentioned metal foil, and even more preferably 20 to 50 μm. Further, for example, an aluminum foil in the 3000 series having a JIS (AA) symbol and satisfying the above formula (2) can also be used. In the case of 3000 series aluminum foil, a hard material having a thickness of 80 μm or more is more preferable.

The copper foil is not particularly limited as long as it satisfies the above formula (2), but for example, a copper foil having a thickness of 70 μm or more is preferably exemplified.

In the above formula (2), when a metal foil having an F × T of more than 22000 is used, the metal foil cannot follow the deformation of the resin substrate when the circuit board is molded, and the resin substrate becomes unnatural. Problems such as deformation and peeling of the metal foil from the resin substrate may occur (see FIG. 9).

Further, the metal foil may be laminated on the surface of the resin substrate via an adhesive layer. That is, an adhesive layer containing an adhesive may be laminated on the resin substrate, and a metal foil may be laminated on the adhesive layer. As the adhesive, a known adhesive can be used, and examples thereof include epoxy resin, polyester resin, acrylic resin, urethane resin, silicon resin, polyimide resin, vinyl chloride resin and the like. These adhesives can be used alone or in combination of two or more. The resin contained in the resin substrate and the adhesive (resin) contained in the adhesive layer may be different, but are preferably the same. In particular, when the resin constituting the resin substrate and the resin constituting the adhesive layer are the same, it can be said that the adhesive layer is integrated with the resin substrate (that is, the adhesive layer does not exist). ..

The thickness of the adhesive layer is preferably in the range of 0.5 to 7 μm, more preferably 1.5 to 4 μm, for example. If the thickness is less than 0.5 μm, the unevenness of the resin substrate or the metal foil cannot be filled, and there is a possibility that sufficient adhesive strength cannot be obtained.

Further, in order to protect the surface of the metal foil that is not in contact with the resin substrate (or the adhesive layer), it is preferable that at least a part (a part or the whole) thereof is covered with a protective resin. That is, a protective layer containing a protective resin may be provided on the back surface of the surface of the metal foil on which the resin substrate is arranged. Further, not only the surface of the metal foil but also a part or the whole of the side surface provided with the circuit pattern of the resin substrate may be coated with the protective resin. (In this case, the surface of the circuit pattern is also coated with the protective resin. It can be said that the protective resin is laminated on the surface of the resin substrate on the circuit pattern formation side.) A known protective resin is used. be able to. For example, epoxy-based resin, polyester-based resin, acrylic-based resin, urethane-based resin, silicon-based resin, polyimide-based resin, vinyl chloride-based resin and the like can be mentioned.

The thickness of the protective layer is preferably in the range of, for example, 5 to 30 μm, more preferably in the range of 10 to 15 μm. If the thickness is less than 5 μm, the protective layer is partially thinned during molding, which may result in insufficient function as a protective resin.

When the resin substrate of the present invention is considered as a laminate, it is a laminate having at least a resin substrate and a metal foil (circuit pattern), and an adhesive layer may be provided between the resin substrate and the metal foil, or at least a metal. It can be said that a protective layer (coating with a protective resin) may be provided on the foil (in some cases, a part or all of the circuit pattern forming side surface of the resin substrate). For example, one surface of a resin substrate provided with all of these layers can be described as "resin substrate / adhesive layer / metal foil (circuit pattern) / protective layer".

The circuit pattern has a structure in which a part or all of the linear metal foil line is folded in a zigzag shape in the longitudinal direction. The circuit pattern of the structure can be said to be a zigzag meandering circuit pattern.

A line has a width and a length. In the present invention, the direction of measuring the width of the line is referred to as the width direction, and the direction of measuring the length is referred to as the longitudinal direction (see FIG. 1). FIG. 2 shows an example of a structure in which the metal foil line is folded in a zigzag shape in the longitudinal direction. The longitudinal direction of the zigzag meandering circuit pattern coincides with the longitudinal direction of the metal leaf line before folding. In other words, the longitudinal direction of the zigzag meandering circuit pattern can be said to be parallel to the traveling direction of the snake, when the meandering of the meandering circuit is considered to be literally winding. In the present specification, the longitudinal direction of the zigzag meandering circuit pattern may be referred to as the first direction.

In the present specification, the width of the zigzag meandering circuit pattern means the width of the meandering pattern. Further, the width of the metal leaf line of the circuit pattern is the same as the width of the metal leaf line before folding in a zigzag shape. The length of the zigzag meandering circuit pattern means the length of the zigzag meandering circuit pattern in the longitudinal direction. The length of the metal leaf line of the zigzag meandering circuit pattern means the length of the metal leaf line folded in a zigzag shape. That is, the width and length of the metal leaf line of the zigzag meandering circuit pattern are the same as the width and length of the metal leaf line before folding, respectively, and the width and length of the zigzag meandering circuit pattern are folded. The width and length of the pattern in the longitudinal direction (length in the first direction) after that (see FIG. 3). In the present specification, the length of the metal leaf line of the circuit pattern may be referred to as the circuit pattern line length. Further, the length of the zigzag meandering circuit pattern may be referred to as the length in the first direction. The length in the first direction is not particularly limited, but is preferably 5 mm or more, and more preferably 10 mm or more, for example.

In the present specification, the meandering circuit pattern in a zigzag shape is a metal leaf line (sometimes referred to as a "wiring portion") substantially parallel to the longitudinal direction and the perpendicular direction of the meandering circuit pattern, and a metal foil connecting the wiring portions. It can also be thought of as a line (sometimes called a "connection"). In other words, the meandering circuit pattern is composed of a wiring portion in which wirings adjacent to each other in the longitudinal direction of the meandering circuit pattern are substantially parallel to each other and a connection portion connecting the wiring portions. it can. The wiring part consists of a substantially straight metal leaf line. The length of the wiring portion (see FIG. 3) is not particularly limited as long as the equation (1) is satisfied, and may be 0 mm or more. For example, it may be approximately 0 mm or about 10,000 mm. For example, it is preferably 0 mm or more and 10000 mm or less (for example, 5000 mm or less, 3000 mm or less, 1000 mm or less, or 500 mm or less). Further, the distance between the wiring portions (see FIG. 3) is not particularly limited as long as the equation (1) is satisfied, and for example, about 0.1 mm to 5 mm is exemplified. For example, 0.1 mm or more and 3 mm or less is more preferable, and 0.5 mm or more and 2 mm or less is further preferable.

Further, the width of the metal leaf line of the circuit pattern is not particularly limited, and for example, about 0.1 mm to 50 mm is exemplified. Although not particularly limited, it is preferable that the distance between the wiring portions is equal to or less than the width of the metal foil line. Also, in the meandering circuit pattern, the metal leaf line width may vary (ie, may not be constant). For example, it may be 0.5 mm in some places of the meandering circuit pattern, but 1.0 mm in other places. When the metal foil line width changes, the line width may change gradually (smoothly) or abruptly, but it is preferable that the line width changes gradually (smoothly). Although not particularly limited, when the metal leaf line changes in the meandering circuit pattern, the width ratio of the narrowest portion to the widest portion is preferably greater than 1: 1 to about 5, preferably 1: 2. More preferably, it is about ~ 3.

Further, the connecting portion is not particularly limited as long as the wiring portion can be connected without impairing the effect of the present invention, and examples thereof include a substantially U-shape, a substantially V-shape, a substantially C-shape, and a substantially I-shape (straight line). (See FIG. 4; the connection portions in FIG. 4 are substantially U-shaped, substantially V-shaped, substantially C-shaped, and substantially I-shaped in order from the top).

Various zigzag meandering circuit patterns can be formed depending on the length of the wiring portion, the shape of the connection portion, the width and length of the metal foil line, and the like. These various zigzag meandering circuit patterns can be used as long as the effects of the present invention are not impaired. Although not particularly limited, some zigzag meandering circuit patterns are illustrated in FIGS. 5a and 5b. Note that FIG. 5b shows an example of a meandering circuit pattern in which the width of the metal foil line changes.

Further, the number of turns (in other words, the number of connecting portions) in the zigzag meandering circuit pattern is not particularly limited, but is preferably 2 or more, for example, about 2 to 1000 can be exemplified, and about 2 to 100 is more preferable. About 50 is more preferable.

Further, the width of the zigzag meandering circuit pattern depends on the length of the wiring portion, the shape of the connection portion, etc., but is not particularly limited, and is, for example, about 1.05 to 1.7 times the length of the wiring portion. It is preferably about 1.1 to 1.5 times, and more preferably about 1.1 to 1.5 times.

Even a complicated circuit pattern including a zigzag meandering circuit pattern can be easily obtained by etching a metal foil, for example.

As described above, the wiring board according to the present invention is
(Equation 1): E (resin) / 4-E (metal) <(BA) / A × 100
Is also satisfied. The number of variables included in the equation (1) is four, and in the meandering circuit pattern of the spiral fold, the metal leaf line length of the meandering circuit pattern in the range of A [mm] in the longitudinal direction is B [mm]. The tensile elongation at break of the resin substrate in the longitudinal direction of the meandering circuit pattern is E (resin) [%], and the elongation at break of the metal foil is E (metal) [%].

Here, the tensile elongation at break E (resin) [%] of the resin substrate is a value measured by JIS C 2151, and the tensile elongation at break E (metal) [%] of the metal foil is a value measured by JIS Z 2241. Is.

By having the above configuration, the wiring board according to the present invention can reduce the possibility that the circuit cannot follow the elongation of the resin and is broken or the circuit is peeled off from the resin board during molding. it can. Particularly preferably, when the molding involves bending the wiring board in a direction in which a bending line substantially orthogonal to the longitudinal direction (first direction) of the meandering circuit pattern is formed, the circuit is peeled off from the resin substrate. And disconnection are suppressed. It should be noted that it is not necessary for the bending line to be formed in the molding, and here, the word "bending line" is only used to explain the bending direction. Further, "substantially orthogonal" is not particularly limited, but the angle formed by the bending line from the first direction is preferably about 90 ° ± 30 °, more preferably about 90 ° ± 20 °, and 90 ° ± 10 About ° is even more preferable, about 90 ° ± 5 ° is even more preferable, and about 90 ° ± 3 ° is still more preferable.

From a larger point of view, in the wiring board according to the present invention, it can be said that the meandering circuit pattern in a zigzag shape can be extended in the first direction at the time of molding, and a force for extending the circuit in the first direction is applied. However (for example, even if the wiring board is bent in the direction in which the bending line substantially orthogonal to the first direction is formed), it can be said that the circuit pattern is less likely to cause peeling or disconnection.

It is shown that when a wiring board (film) having a zigzag meandering circuit pattern and a linear circuit pattern made of various metal foils is bent, the linear circuit pattern causes disconnection, but the meandering circuit pattern does not cause disconnection. The photograph is shown in FIG.

Therefore, the wiring board according to the present invention is molded in a direction in which a force for extending the circuit is applied in the longitudinal direction (first direction) of the meandering circuit pattern (for example, in a direction in which a bending line substantially orthogonal to the first direction is formed). It is particularly preferably used for molding) including bending of a wiring board.

The present invention preferably also includes a molded product of the wiring board. As described above, the wiring board according to the present invention is particularly preferably used for molding in which a force for extending the circuit is applied in the longitudinal direction (first direction) of the meandering circuit pattern. The molded product is particularly preferable. The present invention also preferably includes a component provided with the wiring board and the molded product.

Although not particularly limited, for example, when the wiring board according to the present invention is molded in the shape of a dashboard of an automobile, for example, the molded wiring board corresponds to a molded product, for example, an automobile provided with the molded product. The dashboard (and the vehicle equipped with the dashboard of the vehicle) corresponds to the component.

In addition, in this specification, "including" also includes "consisting essentially" and "consisting of" (The term "comprising" includes "consisting essentially of" and "consisting of.").

Hereinafter, the present invention will be specifically described, but the present invention is not limited to the following examples.
(Example 1)
Adhesive resin (DIC Co., Ltd.) on one side of 80 μm thick aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 1N30, hard material: tensile elongation at break 6%, 0.2% proof stress 150 N / mm ²⁾ Urethane adhesive: 100 parts of LX500 and 10 parts of KW75, which is a curing agent, are mixed), coated and dried, and then bonded to a polypropylene film (FRTK-G manufactured by Futamura Chemical Co., Ltd.) with a thickness of 60 μm. It was. The tensile elongation at break and 0.2% proof stress of the aluminum foil were measured by JIS Z 2241.

Next, the aluminum foil was formed into a zigzag meandering pattern circuit by a photolithography method. The outline of the circuit pattern is shown in FIG. In the circuit pattern, the metal leaf line width is 1 mm, the distance between the wiring portions of the circuit is about 0.3 mm, the connection portion is substantially U-shaped, and the outer edge of the connection portion is semicircular.

The length of the zigzag meandering circuit pattern in the longitudinal direction (first direction) was set to 10 mm, and the total length of the circuit within this range (circuit pattern line length) was set to 30 mm. The tensile elongation at break in the first direction of the polypropylene film used alone was 500%. The tensile elongation at break in the first direction of the polypropylene film was measured by JIS C 2151.

The test body thus obtained was molded. In the molding process, as shown in FIG. 7, the obtained test piece was fixed so that the circuit pattern surface and the mold were in contact with each other, and a metallic jig having a tip on a hemisphere with an R (radius) of 2.5 mm was used. This was done by pressing at a speed of 50 mm / min. At this time, the position of the jig to be pressed against the test piece was set to be around the center of the range of 10 mm in the circuit shown in FIG. Further, the depth at which the jig was pushed was set to 50% of the depth at which the depth at which the test piece was broken was confirmed in advance.

(Examples 2 to 8 and Comparative Examples 1 to 6)
A test body was prepared in the same manner as in Example 1 except that the metal foil, resin layer, and circuit pattern shown in Table 1 were adopted. The circuit pattern line length differs depending on each example, but this is adjusted by changing the length of the wiring portion.

In addition, the tensile elongation at break (E (metal)) and 0.2% proof stress of the metal foil used in each example are based on JIS Z 2241, and the tensile elongation at break of the resin layer (resin film or sheet) used in each example. (E (resin)) was measured by JIS C 2151, respectively.

<Evaluation items and evaluation criteria>
The test bodies of each Example and Comparative Example obtained as described above were evaluated from the viewpoints of (A) and (B) below. The results are also shown in Table 1.

(A) Disconnection of circuit pattern after molding The test pieces obtained in each Example and Comparative Example were visually observed and the electric resistance value was measured, and it was confirmed whether or not the circuit pattern was disconnected. The evaluation results are displayed as follows.

◯: No disconnection of the circuit pattern.
X: There is a disconnection in the circuit pattern.

(B) Distortion of the resin layer after molding The test pieces obtained in each Example and Comparative Example were visually observed to confirm whether the resin layer was distorted in the vicinity of the circuit pattern. The evaluation results are displayed as follows.

◯: No distortion of the resin layer.
X: The resin layer is distorted.

As the above results show
Equation (1): E (resin) / 4-E (metal) <(BA) / A × 100
Equation (2): (F × T) ≦ 22000
It was found that a wiring board that satisfies all of the above conditions can pass a large current and can suppress disconnection and peeling of a circuit during molding.

Claims (7)

A wiring board having a circuit pattern made of metal foil on at least one side of a resin board.
A part or all of the circuit pattern is a zigzag meandering circuit pattern having a structure in which linear metal leaf lines are folded in a zigzag shape in the longitudinal direction.
The metal foil is an aluminum foil.
The metal leaf line length of the meandering circuit pattern in the range of A [mm] in the longitudinal direction of the meandering circuit pattern is defined as B [mm].
The value measured by JIS C 2151 for the tensile elongation at break of the resin substrate in the longitudinal direction of the meandering circuit pattern is E (resin) [%], and the tensile elongation at break of the metal foil is measured by JIS Z 2241. E (metal) [%]
When the 0.2% proof stress of the metal foil at 25 ° C. was measured by JIS Z 2241 as F [N / mm ² ] and the thickness was T [μm].
A wiring board that satisfies the following equations (1) and (2).
Equation (1): E (resin) / 4-E (metal) <(BA) / A × 100
Equation (2): (F × T) ≦ 22000 The wiring according to claim 1 , wherein the resin substrate is a substrate containing at least one resin selected from the group consisting of polyethylene-based resin, polypropylene-based resin, polyester-based resin, acrylic-based resin, and polycarbonate-based resin. substrate. The wiring board according to claim 1 or 2 , wherein at least a part of the metal foil is coated with a protective resin. The wiring board according to any one of claims 1 to 3 , wherein the metal foil is laminated on at least one surface of the resin substrate via an adhesive layer. The wiring board according to any one of claims 1 to 4 , wherein a force for stretching a zigzag meandering circuit is applied in the longitudinal direction of the meandering circuit pattern. The molded product of the wiring board according to any one of claims 1 to 5. A component comprising the wiring board according to any one of claims 1 to 5 or the molded product according to claim 6.

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