JP4737092B2 - Circuit board for molding and three-dimensional circuit obtained using the same - Google Patents

Description

  The present invention relates to a molding circuit board capable of drawing or deep drawing and a three-dimensional circuit obtained by processing the circuit board.

  Planar film antennas are used in small electronic devices such as cellular phones because of their flexibility and miniaturization. Recently, there has been a demand for further downsizing, multi-functionalization, and cost reduction of such electronic devices, and a method of mounting a three-dimensional circuit board on an electronic device has been proposed and realized.

  For example, there is a mold printed circuit board (MPCB) or an injection molding circuit (MID). A circuit board is obtained by these injection moldings, and is roughly classified into a plating system and a circuit film system.

  The plating method is obtained by plating a resin molded product, and a representative production method includes a one-shot mold method and a two-shot mold method. In the one-shot mold method, first, a desired three-dimensional shape is formed using a resin capable of electroless plating, then a photoresist is applied to the surface of the molded product, a circuit pattern is exposed, developed, and an exposed resin surface. A three-dimensional circuit board is formed by electroless plating.

  In contrast, the two-shot mold method uses a resin mixed with a catalyst for plating, forms a solid that can be electrolessly plated by the first injection molding, and further determines the predetermined of the solid by the second injection molding. A surface layer that is not subjected to electroless plating is formed on the surface, and then electroconductive plating is performed on the first molded three-dimensional surface to form a conductive portion.

  On the other hand, the circuit film system is a system in which a predetermined circuit pattern is formed on the film surface, and the predetermined circuit pattern is integrated or transferred at the time of resin molding. The in-mold method forms a circuit pattern on the film surface to be a substrate by a conventionally known method, and then loads the substrate on which the circuit pattern has been formed into a molding die and fills the resin with the resin molded body. Or a circuit molded body is manufactured by transferring the circuit pattern to a resin molded body.

  However, the various manufacturing methods described above have the following problems due to their characteristic manufacturing processes. For example, in the one-shot mold method, the manufacturing process is very long and the cost is high. Further, it is not suitable for manufacturing a three-dimensional shape having a three-dimensional curved surface shape. Furthermore, the material for forming the resin molded product is limited, and patterning of the circuit is difficult.

  In addition, although the two-shot mold method is suitable for manufacturing a three-dimensional shape having a three-dimensional curved surface shape, a high-precision mold is required as a molding die, and two injection moldings are performed. The cost becomes higher.

  In addition, the circuit film type in-mold method can apply various methods to the formation of the circuit pattern and has a high degree of freedom in selecting the material for forming the resin molded product, but the adhesion between the circuit pattern and the resin molded product can be improved. It is not fully satisfactory in terms of the degree and followability to the three-dimensional shape.

  In order to eliminate the drawbacks of these methods using the injection molding method, it was formed of a forming material having a melting point lower than the thermal decomposition temperature of the thermosetting resin filled in the mold and higher than the molding temperature. A predetermined conductor circuit pattern is formed on the surface of the spherical molded body, and the spherical molded body is loaded in the mold while maintaining a predetermined space with the inner peripheral surface of the mold, and the thermosetting resin is placed in the space. After the thermosetting resin is thermoset to form a thermosetting resin molded body composed of a thermosetting resin cured body and a spherical molded body, the above-mentioned thermosetting resin molded body is filled with the above-mentioned Patent Document 1 discloses a method for manufacturing a three-dimensional molded circuit body by melting and removing a spherical molded body.

  However, in any of these methods, the problem that the injection molding method itself has a long process, the problem that an expensive mold is used, and the problem that it is difficult to obtain a thin molded product have been solved. Absent. In addition, when obtaining a resin molded body capable of electroless plating, there is a problem that a large amount of expensive Pd must be added to the resin for producing the resin molded body and kneaded.

  By the way, as a method of forming a three-dimensional circuit pattern with a thin film-like substrate, copper or the like is formed on the surface of a resin film or sheet made of an amorphous polymer such as ABS resin, polycarbonate, polyethersulfone or the like. A film-like member having a conductive part formed of silver and a resin film made of an amorphous polymer such as ABS resin, polycarbonate, polyethersulfone, and the conductive part of the film-like member face the resin film surface. Patent Document 2 discloses a method in which the film-like member and the resin member are brought into close contact with each other and blow-molded or vacuum-molded to form a three-dimensional shape.

  In the injection molding method, as described above, the process is very long, a number of expensive molds are used, and a sufficient amount of expensive Pd is added to the resin in advance so that electroless plating can be performed after injection molding. It is not necessarily sufficient because of the high cost.

  In the method described in Patent Document 2, a circuit pattern is formed in advance on the surface of a resin film or sheet by a photoresist method or the like. When the obtained sheet is formed in two or more directions by drawing or the like, There is a problem that the wiring constituting the circuit pattern breaks due to the difference in elongation and tensile strength between the metal constituting the circuit pattern and the resin. In order to prevent this, a part of the film or the like is cut so as to obtain the desired three-dimensional shape, and the molding process is performed so that the elongation of the metal and the resin can follow each other, but the cutting is performed. Wiring cannot be formed on the film or the like, which is a great restriction in circuit design.

As means for solving such problems, a circuit board for molding processing having a multilayer structure is composed of at least three layers, and the first layer is selected from polyimide, polyetherimide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). Any one resin film, the second layer has a circuit having a desired pattern, and the third layer is any one resin film selected from polyimide, polyetherimide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). And the thing with the adhesive strength of 400 N / m or more of the resin film of a 1st layer and the wiring which comprises the circuit of a 2nd layer is examined.
JP 09-148712 A Japanese Patent Application Laid-Open No. 04-08292

  This substrate surely eliminates the problems of the injection molding method and the like, and even if three-dimensional molding such as drawing is performed using this substrate, the circuit pattern is not damaged. However, unfortunately, the deep drawing process has revealed the problem that the wiring is cracked at the corner of the wiring.

  Accordingly, an object of the present invention is to provide a molding circuit board that does not cause wiring damage even when deep drawing is performed, and a three-dimensional circuit obtained by using the molding circuit board.

As a result of various studies conducted by the present inventors to solve the above problems, if the corner of the wiring part constituting the circuit of the circuit board for molding is formed into a shape that satisfies a specific condition, the first layer is polyimide, Any one resin film selected from polyetherimide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), the second layer is a circuit having a desired pattern, and the first layer and the second layer circuit The present inventors have found that the above-mentioned problems can be solved with a circuit board for molding with an adhesion strength of 400 N / m or more.
That is, the first invention for solving the above-mentioned problem is a circuit board for molding processing having a multilayer structure, which is composed of at least two layers, the first layer of which is polyimide, polyetherimide, polyethylene terephthalate (PET), Any one resin film selected from polyethylene naphthalate (PEN), the second layer is a circuit having the following characteristics, and the adhesion strength between the first layer resin film and the second layer circuit is 400 N / m. That's all.
(Circuit features)
In the corner portion of the wiring that constitutes the circuit, the corner portion has a shape with a curvature radius R of t / 2 or more when the width of the wiring closest to the corner portion is t. Make it curved.
And in addition to the said invention, this 2nd invention is provided so that the space | interval between wiring which forms a circuit pattern may become equal to or more than wiring width.

  In the third aspect of the present invention, in any one of the above aspects, the circuit is made of copper.

  The fourth invention is a three-dimensional circuit obtained by molding the molding circuit board according to any one of the first to third embodiments.

In the substrate of the present invention, the adhesion strength between the resin film layer of the first layer and the circuit of the second layer is as high as 400 N / m or more, and the shape of the corner portion is set at the corner portion of the wiring constituting the circuit. When the width of the wiring closest to the corner portion is t, a three-dimensional shape three-dimensional circuit formed body is created by deep drawing in order to obtain a curved shape with a curvature radius R of t / 2 or more inside the corner. Even so, the distortion does not concentrate and the resulting wiring of the molded body is not damaged. Furthermore, deep drawing can be performed by providing a space equal to or larger than the wiring width between the wirings forming the circuit pattern.
If the structure of the present invention is adopted, deep drawing can be performed even if the line width is increased to 2 mm.

  The most characteristic feature of the present invention is that stress is not concentrated at the time of deep drawing at the corner portion of the wiring that is generated when the wiring is designed to be bent or when the wiring is designed to intersect. Thus, when the minimum line width closest to the corner portion is t, the shape of the corner portion is curved so that the radius of curvature R becomes t / 2 or more inside the corner. By doing so, it is possible to prevent stress from being concentrated on one point of the corner portion.

  In addition, the distance between the wirings forming the circuit pattern is equal to or larger than the wiring width. By doing so, it becomes possible to release the complicated stress applied to the wiring by the deep drawing process to the resin portion, and the wiring will not be broken even if the deep drawing process is performed.

  Next, a configuration other than this will be described. In the present invention, the adhesion strength between the circuit and the first layer needs to be 400 N / m or more. Therefore, if you have the required adhesion strength, use a resin film that is the first layer laminated with a metal foil via an adhesive, process the metal foil to create a circuit, and then place the resin film on the circuit Even if the circuit board for molding processing is prepared by pasting, a plating layer having an adhesion strength of 400 N / m or more is provided on the surface of the resin film by plating, and the same processing as described above is performed using the plating layer. You may get.

  In the case of forming a circuit composed of wiring having a width of 100 μm or less, it is recommended to use a resin film provided with a metal layer directly on the basis of reliability and electrical characteristics of the obtained circuit.

  When deep-drawing the circuit board for molding according to the present invention, a resin film of the same type as that of the first layer may be bonded to the circuit surface so as not to damage the circuit surface. Of course, the circuit surface may be covered with a resin film for deep drawing or construction and loaded into the mold.

  The resin film that can be used as the first layer in the present invention is polyimide, polyetherimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or the like. The reason for selecting these is for reasons such as transparency, insulation, heat resistance, and corrosion resistance required when a circuit is formed.

  The material that can be used as the circuit of the second layer is not particularly limited as long as it has a function as a circuit, and from this point of view, it may be a conductive material. It is preferable that

  Also, in order to increase the adhesion strength between the circuit and the first layer resin film, a seed layer is provided on the surface of the first layer by a dry plating method, and a metal layer is provided on the seed layer by a dry plating method or an electrolytic plating method. It is preferable to form a circuit by forming a conductive layer composed of a seed layer and a metal layer and etching the conductive layer. At this time, it is more preferable to increase the adhesion strength when the seed layer is formed of a thin film of Ni, Cr, Co, Mo, W, or an alloy mainly composed of these.

  In addition, providing a discoloration preventing film on the circuit surface is also a preferable aspect from the viewpoint of preventing discoloration due to long-term use of a three-dimensional circuit obtained by molding.

  Next, an example of forming the circuit board for molding according to the present invention will be described.

The circuit board for molding according to the present invention can be produced, for example, by the following steps.
First, a seed layer is provided on the surface of a resin film such as polyimide, polyetherimide, polyethylene terephthalate (PET), or polyethylene naphthalate (PEN) by a dry plating method such as a vapor deposition method or a sputtering method. The seed layer may be made of Cu, but is preferably made of Ni, Cr, Co, Mo, W, or an alloy mainly composed of these in order to ensure the adhesion between the wiring layer and the resin film. The conditions of the vapor deposition method and sputtering method that are specifically employed are not particularly limited, and may be appropriately selected according to the metal used as the target from the methods already disclosed.

  Next, a metal is deposited on the seed layer by at least one of vapor deposition, sputtering, and plating to provide a metal layer, and a conductive layer composed of the seed layer and the metal layer is provided. The material of the metal layer at this time is preferably copper from the viewpoint of ease of processing and electrical characteristics of the wiring portion. As for the specific conditions of the vapor deposition method, the sputtering method, and the plating method, the commonly used conditions may be selected as described above.

  Next, the conductive layer is patterned to create a desired pattern circuit with curved corners. At this time, for example, a photoresist is screen-printed on the surface of the conductive layer, or a photoresist film is bonded to the desired layer. Exposure is performed using a mask having a pattern, development is performed to form an etching mask, and the conductor layer and the seed layer are etched using this etching mask. For these methods, the technique used for producing a printed wiring board or the like which is an electronic component can be applied as it is.

  After forming the circuit in this manner, a resin film layer is provided on the circuit surface as necessary. As a method at this time, a liquid resin may be applied, or a film-like resin may be attached. The resin used in this case is not particularly limited as long as it is a film that can be formed by a mold at the time of molding, but it may be molded by applying heat at the time of molding, and the resin of the first layer Similarly, since it must be stretched, the same material as that of the first layer resin film or a material having a glass transition temperature and tensile properties close to those of the first layer resin is preferable.

  As the resin film of the first layer, a resin of polyimide, polyetherimide, polyethylene terephthalate (PET), or polyethylene naphthalate (PEN) can be used.

  When using a member in which the first layer and the second layer are bonded with an adhesion strength of 400 N / m or more, the second layer may be etched to form a circuit. is not.

(Examples 1 to 15)
Embodiments of the present invention will be specifically described below with reference to the drawings.
First, the circuit pattern is made into the lattice shape shown in FIG. 1, and the inner corner where the wiring intersects is curved as shown in FIG. It was confirmed whether the wiring would break when processed.
As a first layer resin film, a 50 μm thick PET film (trade name S10, manufactured by Toray Industries, Inc.) is used. A seed layer is formed on the surface by copper using a vapor deposition method, and then a copper plating layer is formed by electrolytic copper plating. A conductive layer having a copper layer thickness of 10 μm was formed. The conditions of the electrolytic copper plating method were as follows.
Plating bath composition: copper sulfate concentration 100 g / liter, sulfuric acid concentration 180 g / liter, hydrochloric acid 50 mg / liter Plating bath temperature: room temperature Cathodic current density: 1 A / dm ²
Next, a dry film resist (trade name AQ-1158 manufactured by Asahi Kasei Co., Ltd.) is attached to the surface of the conductive layer, exposed using a predetermined mask, and developed to obtain the wiring shape shown in FIGS. A mask was prepared. Then, the conductive layer is removed by etching, the last remaining etching mask is peeled off, and the wiring width of the grid-like wiring portion is 1 mm (Examples 1 to 5), 0.5 mm (Examples 6 to 10), Two types of circuits having the patterns shown in FIGS. 1 and 2 of 2 mm (Examples 11 to 15) were prepared to obtain a circuit board for molding with a two-layer structure. In addition, each circuit was formed so that the gap of the lattice was twice as wide as the wiring width, and the inner corner portion shape where the wiring intersected was formed into a curved shape with the curvature shown in Table 1. The adhesion strength between the circuit of the obtained circuit board for molding and the PET film was 400 N / m or more.
Next, a thin PET film is obtained so that the circuit does not directly touch the inner surface of the mold shown in FIG. 3 and placed on the surface of the circuit board for molding, and each of the molds shown in FIG. A three-dimensional circuit was obtained by molding so as to form a cube having a side length of 20 mm × 50 mm × height 10 mm. The heating temperature was 160 ° C. and held for 30 seconds.
Thereafter, it was confirmed whether or not the circuit portion of each three-dimensional circuit had a broken portion. The results are shown in Table 1.

  From Table 1, no break was found in each three-dimensional circuit. As a result, a circuit board for molding having a circuit formed so that the curvature (R) of the corner portion satisfies the relationship of t / 2 or more with respect to the wiring width (t) can be used regardless of the wiring width. For example, it has been confirmed that a three-dimensional circuit can be obtained without breaking the circuit even after drawing.

(Examples 16 to 30)
In the same manner as in Examples 1 to 3, a PET film having a circuit provided on one side thereof was obtained.
Next, a PET film having a thickness of 50 μm was laminated on the circuit surface through an adhesive to form a three-layer structure to obtain a circuit board for molding. The adhesion strength between the circuit of the obtained circuit board for molding and the PET film was 400 N / m or more.
The obtained circuit board for molding processing is molded using a mold shown in FIG. 3 so that each side has a length of 20 mm × 50 mm × height 10 mm as shown in FIG. It was. The heating temperature was 160 ° C. and held for 30 seconds.
Thereafter, it was confirmed whether or not there was a break in the circuit portion of each three-dimensional circuit. The results are shown in Table 2.

  From Table 2, no break was found in each three-dimensional circuit. As a result, a circuit board for molding having a circuit formed so that the curvature (R) of the corner portion satisfies the relationship of t / 2 or more with respect to the wiring width (t) can be used regardless of the wiring width. For example, it has been confirmed that a three-dimensional circuit can be obtained without breaking the circuit even after drawing.

(Examples 31-45)
Next, whether or not the wiring breaks by making the inner corner where the wiring intersects into a curved shape with a predetermined curvature in the same manner as in Example 1 by using a polyimide film as the base material of the first layer confirmed.
Using a copper poly substrate (trade name S'perFlex, manufactured by Sumitomo Metal Mining Co., Ltd.) in which a 8 μm thick copper foil was provided on the surface of a 38 μm thick polyimide film, a circuit was formed in the same manner as in Example 1. A two-layered circuit board for molding was obtained. The adhesion strength between the circuit of the obtained circuit board for molding processing and the polyimide film was 400 N / m or more.
Thereafter, in the same manner as in Example 1, the molding circuit of FIG. 4 was obtained by molding using the mold of FIG. The processing temperature was 200 ° C. and the holding time was 2 minutes.
It was investigated whether the circuit part of a three-dimensional circuit had a fracture part. The results are shown in Table 3.

  From Table 3, regardless of the wiring width, by forming the curvature of the corner portion so that the curvature (R) is greater than or equal to t / 2 with respect to the wiring width (t), the metal wiring is not broken. It was confirmed that three-dimensional formation was possible.

(Examples 46 to 60)
Next, a circuit was formed in the same manner as in Example 31 using a copper poly substrate (trade name S'perFlex, manufactured by Sumitomo Metal Mining Co., Ltd.) in which a copper foil having a thickness of 8 μm was provided on the surface of a 38 μm polyimide film. . The adhesion strength between the circuit of the obtained circuit board for molding processing and the polyimide film was 400 N / m or more.
After that, a polyimide with adhesive made by Yodogawa Manufacturing Co., Ltd. is in contact with the circuit surface so that the adhesive surface is on the circuit surface side, and thermocompression bonding is performed at a temperature of 180 ° C. for 30 seconds to form a three-layer structure. A circuit board was prepared. The molding circuit board was molded using the mold shown in FIG. 3 in the same manner as in the example to obtain the three-dimensional circuit shown in FIG. The processing temperature was 200 ° C. and the holding time was 2 minutes.
It was investigated whether the circuit part of a three-dimensional circuit had a fracture part. The results are shown in Table 4.

  From Table 4, regardless of the wiring width, by forming the curvature of the corner portion so that the curvature (R) is t / 2 or more with respect to the wiring width (t), the metal wiring is not broken, It was confirmed that three-dimensional formation was possible.

(Examples 61 and 62)
Next, a circuit board for molding with a two-layer structure was obtained in the same manner as in Example 1 except that the circuit was the circuit of FIG. 6 having a curved corner portion where R in FIG. 5 had a curvature of t / 2. It was. The adhesion strength between the circuit of the obtained circuit board for forming and the PET film was 400 N / m or more.
Using the obtained circuit board for molding processing, deep drawing is performed according to the procedure of FIGS. 7 (1) to (3), and a three-dimensional circuit having a length of each side of 20 mm × 50 mm × height 20 mm as shown in FIG. Obtained.
The mold used is such that it comes into contact with a recess having a desired shape, an upper mold 14 provided with a suction port 13 for sucking the gas inside the recess to the outside, and a substantially central portion of the recess of the upper mold. In addition, it is composed of a lower mold having a suction nozzle 15 and a gas introduction port 16 provided so as to be movable up and down.
In the molding process, first, a thin PET film is placed on the circuit surface of the circuit board 12 for molding process, and this is fixed by the upper mold 14 and the lower mold 17 (FIG. 7 (1)), and then the suction nozzle is moved to the mold. The molding circuit board 12 is inserted into the mold, pressed against the inner surface of the concave portion of the upper mold 14, and sucked from the suction nozzle 15 to secure the positional accuracy, thereby fixing the molding circuit board 12 (FIG. 7 ( 2)) Next, from the gas inlet port provided in the lower mold (14) while sucking air in the mold from the gas suction port (13) also received by the suction nozzle 15 and the upper mold 14 This was done by introducing compressed gas.
Note that the temperature of the mold during molding was 160 ° C., and after sucking and introducing pressurized air, the mold was held in that state for 30 seconds.
It was confirmed whether or not the obtained three-dimensional circuit was broken, but it was not broken.
Regarding the position accuracy after molding, whether or not the position confirmation wiring 11 after molding in FIG. 1 is located in the center of the three-dimensional circuit after molding was confirmed at any eight positions of the position confirmation wiring. The results are shown in Table 5. The position accuracy (%) in Table 5 is indicated by a value obtained by dividing the distance shifted from the center position by the distance of 1/2 side of the molded shape. For comparison, without operating the suction nozzle 15, suction is performed from the gas suction port 13 of the upper mold 14, and compressed gas is introduced from the gas inlet 16 of the lower mold 17, so that the circuit board 12 for molding processing is obtained. The results of molding are also shown in Table 5.

    From the results in Table 5, when molding is performed without positioning using the suction nozzle 15, the position shift changes greatly, but if positioning and molding is performed using the suction nozzle 15, molding is performed with extremely high positioning accuracy. It was confirmed that it was possible.

(Example 63)
For forming a three-layer structure in the same manner as in Example 46 except that a two-layer substrate (S'perFlex manufactured by Sumitomo Metal Mining Co., Ltd.) in which a copper foil having a thickness of 8 μm is formed on a 38 μm-thick polyimide film is used. A circuit board was obtained. The adhesion strength between the circuit of the obtained circuit board for molding processing and the polyimide film was 400 N / m or more.
A three-dimensional circuit was prepared from the obtained circuit board for molding processing in the same manner as in Example 61. The mold temperature during processing was 200 ° C., 200 ° C. compressed air was injected, and the holding time was 1 minute.
As a result of confirming the positional accuracy after molding in the same manner as in Example 61, the same result as in Example 61 was obtained.

FIG. 1 is a diagram showing a lattice circuit used in Examples 1-60. FIG. 2 is a diagram showing details of the wiring corner portions of the circuits used in Examples 1-60. FIG. 3 is a three-dimensional circuit diagram obtained in Examples 1-60. FIG. 4 is a diagram showing the drawing method used in Examples 1-60. FIG. 5 is a diagram showing details of wiring corner portions of the circuits used in Examples 61 and 62. In FIG. FIG. 6 is a diagram showing a circuit obtained in Examples 61 and 62. In FIG. FIG. 7A is a cross-sectional view showing a state in which the circuit board for molding is sandwiched between the upper mold and the lower mold. FIG. 7B is a cross-sectional view showing a state in which the molding circuit board is pressed against the inner surface of the upper mold by the suction nozzle. FIG. 7 (3) is a cross-sectional view showing a state in which it is held and molded after suction and compressed air charging. FIG. 8 is a diagram showing the processing method carried out in Examples 61 and 62.

Explanation of symbols

1 ―――― Substrate with wiring formation 2 ―――― Metal wiring 3 ―――― Corner of metal wiring 4 ―――― Resin film molded into cube 5 ―――― Circuit board for molding 6―― -Mold (female)
7 --- Mold (male)
8 --- Resin film 9 --- Wiring 10 --- Corner corner 11 --- Position confirmation wiring 12 after molding ---- Processing circuit board 13 --- Gas suction port 14 ―――― Upper mold 15 ―――― Suction nozzle 16 ―――― Gas inlet 17 ―――― Lower mold

Claims (4)

A circuit board for molding processing having a multilayer structure, comprising at least two layers, the first layer of which is selected from polyimide, polyetherimide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN) A circuit board for molding, which is a film, wherein the second layer is a circuit having the following characteristics, and the adhesion strength between the resin film of the first layer and the circuit of the second layer is 400 N / m or more.
(Circuit features)
In the corner portion of the wiring that constitutes the circuit, the corner portion has a shape with a curvature radius R of t / 2 or more when the width of the wiring closest to the corner portion is t. Make it curved.   2. The molding circuit board according to claim 1, wherein a space between wirings forming the circuit pattern is equal to or larger than a wiring width.   The circuit board for molding according to claim 1 or 2, wherein the circuit is made of copper.   A three-dimensional circuit obtained by molding the circuit board for molding according to any one of claims 1 to 3.

Images