JP6360760B2 - Copper-clad laminate and circuit board - Google Patents

Description

  The present invention relates to a copper clad laminate (CCL) and a circuit board using the same.

  In recent years, with the progress of miniaturization, weight reduction, and space saving of electronic devices, a flexible printed wiring board (FPC; Flexible Printed) that is thin, light, flexible, and has excellent durability even when it is repeatedly bent The demand for Circuits is increasing. The FPC can be mounted three-dimensionally and in a high density even in a limited space, so its application is for wiring of movable parts of electronic devices such as HDDs, DVDs and mobile phones, parts for cables and connectors, etc. It is expanding.

  The FPC is manufactured by etching and wiring a copper layer of a copper clad laminate (CCL). Rolled copper foil is often used as a material of a copper layer for FPCs that are bent continuously or bent 180 ° in mobile phones and smartphones. For example, in patent document 1, the proposal which prescribes | regulates the bending resistance of the copper clad laminated board produced using the rolled copper foil by the number of times of roll-resistance is made | formed. Moreover, in patent document 2, the copper clad laminated board using the rolled copper foil prescribed | regulated by the glossiness and bending frequency is proposed.

  In the process of photolithography for a copper-clad laminate and in the process of mounting an FPC, various processes such as bonding, cutting, exposure, and etching are performed based on alignment marks provided on the copper-clad laminate. The processing accuracy in these steps is important in maintaining the reliability of the electronic device on which the FPC is mounted. However, since the copper-clad laminate has a structure in which copper layers and resin layers having different thermal expansion coefficients are laminated, stress is generated between the layers due to the difference in thermal expansion coefficient between the copper layer and the resin layer. This stress causes expansion or contraction by being released partially or entirely when the copper layer is etched and processed to cause a change in the dimension of the wiring pattern. Therefore, the dimensional change finally occurs at the stage of the FPC, which causes a connection failure between the wirings or between the wirings and the terminals, which lowers the reliability and the yield of the circuit board. Therefore, in a copper clad laminate as a circuit board material, dimensional stability is a very important characteristic. However, in the patent documents 1 and 2 mentioned above, the dimensional stability of the copper clad laminate is not considered at all.

  In addition, when manufacturing a copper-clad laminate, the dimensional stability of the copper-clad laminate is improved by adopting a method (casting method) of casting a polyimide precursor on a rolled copper foil as compared with a laminate manufacturing method. be able to. However, when manufacturing a copper-clad laminate from a long copper foil by a casting method, there is a problem that irregularities called "corrugation" are easily generated, and stable production becomes difficult.

JP, 2014-15674, A (claim, etc.) JP-A-2014-11451 (claims etc.)

  An object of the present invention is to provide a copper-clad laminate which uses rolled copper foil as a material, is excellent in dimensional stability, and can be stably produced.

  The copper-clad laminate of the present invention is a copper-clad laminate provided with a polyimide insulating layer and a first copper foil layer laminated on one side of the polyimide insulating layer. In the copper clad laminate of the present invention, the thermal expansion coefficient of the polyimide insulating layer is in the range of 10 ppm / K or more and 30 ppm / K or less. In the copper clad laminate of the present invention, the first copper foil layer has a thickness of 13 μm or less, and the product of the thickness (μm) and the tensile elastic modulus (GPa) is in the range of 180 to 250. It consists of a rolled copper foil.

  In the copper-clad laminate of the present invention, the polyimide insulating layer may be formed by applying a precursor solution of a polyimide to the first copper foil layer and drying it, followed by imidization. Good.

  The copper clad laminate of the present invention may further include a second copper foil layer laminated on the surface of the polyimide insulating layer opposite to the first copper foil layer.

The copper clad laminate of the present invention comprises the following steps (1) to (7):
(1) A step of preparing a test piece by cutting the long copper-clad laminate into a predetermined length,
(2) Assuming that the longitudinal direction of the copper-clad laminate is the MD direction and the width direction is the TD direction, an imaginary square shape having sides parallel to the MD direction and the TD direction is assumed in the test piece, A linear array is provided in each of a central area including the center of a virtual square and two corner areas including one of two corners sharing one side in the TD direction in the virtual square. Forming a plurality of marks including
(3) A first measurement step of measuring the positions of the plurality of marks and calculating the distance L0 between the adjacent marks,
(4) etching a part or all of the copper layer of the test piece;
(5) A second measurement step of measuring the positions of the plurality of marks after etching and calculating the distance L1 between the adjacent marks,
(6) A step of calculating a difference L1-L0 between the distance L0 obtained in the first measurement step and the distance L1 obtained in the second measurement step for the same two marks before and after the etching ,as well as,
(7) The difference L1-L0 is converted to the scale of the wiring pattern in the circuit board formed from the copper clad laminate to obtain the cumulative converted dimensional change amount, and the obtained cumulative converted dimensional change amount is the wiring pattern Process expressed as a ratio to the sum of the wiring width and wiring spacing
In the test piece of the ratio of the cumulative dimensional change amount to the sum of the wiring width of the wiring pattern and the wiring interval in a circuit board size of 10 mm obtained by the test method including .

  The circuit board of the present invention is obtained by processing the copper foil of the copper-clad laminate described in any one of the above to a wiring circuit.

  The copper-clad laminate of the present invention is a first copper foil having a thickness of 13 μm or less, and a product of a thickness (μm) and a tensile elastic modulus (GPa) in the range of 180 to 250. By having a layer, it is excellent in dimensional stability and production stability. Therefore, by using the copper clad laminate of the present invention as a circuit board material, the reliability and yield of the circuit board can be improved.

It is a perspective view which shows schematic structure of the copper clad laminated board used for the evaluation method which evaluates the dimensional stability of the copper clad laminated board which concerns on one embodiment of this invention, and a test piece. It is drawing explaining the mark position in a test piece. It is the elements on larger scale of the central area of a specimen. It is the elements on larger scale of the corner area of a specimen. It is drawing explaining the dimensional variation of the space | interval of a hole and a hole. It is drawing used for description of the evaluation sample in an Example and a comparative example. It is drawing used for description of preparation of the evaluation sample in an Example and a comparative example. It is a graph which shows FPC size and wiring misregistration rate in an Example. It is a graph which shows FPC size and wiring misregistration rate in a comparative example.

  Next, embodiments of the present invention will be described with reference to the drawings as appropriate.

<Copper-clad laminates>
The copper clad laminate of the present embodiment is composed of a polyimide insulating layer and a copper foil layer. The copper foil layer is provided on one side or both sides of the polyimide insulating layer. That is, the copper-clad laminate of this embodiment may be a single-sided copper-clad laminate (single-sided CCL) or a double-sided copper-clad laminate (double-sided CCL). In the case of single-sided CCL, the copper foil layer laminated on one side of the polyimide insulating layer is referred to as "first copper foil layer" in the present invention. In the case of double-sided CCL, the copper foil layer laminated on one side of the polyimide insulating layer is referred to as the “first copper foil layer” in the present invention, and in the polyimide insulating layer, the side on which the first copper foil layer is laminated Let the copper foil layer laminated | stacked on the surface on the opposite side be a "2nd copper foil layer" in this invention. The copper-clad laminate of this embodiment is used as an FPC by forming a copper wiring by processing a wiring circuit by etching a copper foil or the like.

<First copper foil layer>
In the copper clad laminate of the present embodiment, the copper foil used in the first copper foil layer (hereinafter sometimes referred to as “first copper foil”) is made of rolled copper foil. A copper-clad laminate capable of achieving both excellent dimensional stability and high flexibility by considering the product of thickness and tensile modulus as described later by using rolled copper foil as the first copper foil Can be manufactured stably. Moreover, in the copper clad laminate of this embodiment, a long copper foil having a ratio (long side / short side) of long side (length) to short side (width) of 600 or more as the first copper foil. Use copper foil.

  The thickness of the first copper foil is 13 μm or less, preferably in the range of 6 to 12 μm. When the thickness of the first copper foil exceeds 13 μm, the bending resistance applied to the copper foil (or copper wiring) when bending the copper-clad laminate (or FPC) becomes large, and thus the bending resistance decreases. Become. Moreover, it is preferable that the lower limit of the thickness of a 1st copper foil shall be 6 micrometers from a viewpoint of production stability and handling property.

The tensile modulus of elasticity of the first copper foil is, for example, preferably in the range of 10 to 35 GPa, and more preferably in the range of 15 to 25 GPa. The rolled copper foil used as the first copper foil in the present embodiment has high flexibility when annealed by heat treatment. Therefore, when the tensile modulus of elasticity of the first copper foil is less than the above lower limit value, when producing a copper clad laminate from the long first copper foil by the casting method, polyimide insulation on the first copper foil is carried out. In the step of forming the layer, the rigidity of the first copper foil itself is reduced by heating. As a result, there arises a problem that corrugation occurs in the copper clad laminate. In addition, when manufacturing a copper clad laminated board by a lamination method, although the problem of the said corrugation hardly arises, sufficient dimensional stability is not acquired.
On the other hand, when the tensile elastic modulus exceeds the above upper limit value, a large bending stress is applied to the copper wiring when the FPC is bent, and the bending resistance thereof is reduced. The tensile modulus of elasticity of the rolled copper foil changes due to heat treatment conditions for forming a polyimide insulating layer on the copper foil by the above-described casting method, annealing treatment of the copper foil after forming the polyimide insulating layer, and the like. There is a tendency to Therefore, in the present embodiment, in the copper clad laminate finally obtained, the tensile modulus of the first copper foil may be in the above range.

  The product of the thickness (μm) of the first copper foil and the tensile elastic modulus (GPa) is in the range of 180 to 250, and preferably in the range of 210 to 240. If the product of the thickness of the first copper foil and the tensile elastic modulus is less than 180, corrugation tends to occur when the copper clad laminate is produced by a casting method using the long first copper foil, which is a production process. The stability decreases, and when it exceeds 250, the bending resistance decreases. In the present embodiment, by defining the product of the thickness of the first copper foil and the tensile elastic modulus in the above range, the handling property and the rigidity of the first copper foil are balanced, and the production stability and Compatibility with bending resistance can be achieved.

  The first copper foil is not particularly limited as long as it satisfies the above characteristics, and a rolled copper foil commercially available can be used. As a commercial item suitable as a 1st copper foil, HA-V2 foil made from JX Nippon Oil Nippon Metal Co., Ltd. can be mentioned, for example.

<Second copper foil layer>
The second copper foil layer is laminated on the surface of the polyimide insulating layer opposite to the first copper foil layer. It does not specifically limit as copper foil (2nd copper foil) used for a 2nd copper foil layer, For example, a rolled copper foil or an electrolytic copper foil may be sufficient. Moreover, the copper foil marketed can also be used as a 2nd copper foil. In addition, you may use the same thing as 1st copper foil as 2nd copper foil.

<Polyimide insulating layer>
In the copper clad laminate of the present embodiment, the thermal expansion coefficient (CTE) of the entire polyimide insulating layer is in the range of 10 ppm / K to 30 ppm / K in order to prevent the occurrence of warpage and the decrease in dimensional stability. It is important to be. The thermal expansion coefficient (CTE) of the polyimide insulating layer is preferably in the range of 10 ppm / K to 25 ppm / K. If the coefficient of thermal expansion (CTE) is less than 10 ppm / K, or more than 30 ppm / K, warpage may occur in the copper-clad laminate or dimensional stability may be reduced. Further, in the copper clad laminate according to the present embodiment, the thermal expansion coefficient (CTE) of the polyimide insulating layer is more preferably ± 5 ppm / K or less relative to the thermal expansion coefficient (CTE) of copper, ± 2 ppm Most preferable is within the range of / K or less.

  In the copper clad laminate of the present embodiment, the thickness of the polyimide insulating layer can be set to a thickness within a predetermined range according to the thickness, rigidity and the like of the copper foil layer. The thickness of the polyimide insulating layer is, for example, preferably in the range of 8 to 50 μm, and more preferably in the range of 11 to 26 μm. If the thickness of the polyimide insulating layer is less than the above lower limit, problems such as the inability to ensure electrical insulation and the difficulty in handling in the manufacturing process due to a decrease in handling may occur. On the other hand, when the thickness of the polyimide insulating layer exceeds the above upper limit value, bending stress may be applied by the copper wiring when the FPC is bent, and the bending resistance may be reduced.

  Moreover, it is preferable that the tensile elasticity modulus of a polyimide insulating layer exists in the range of 3.0-10.0 GPa, and it is good for it to exist in the range of 4.5-8.0 GPa. When the tensile modulus of the polyimide insulating layer is less than 3.0 GPa, the strength of the polyimide itself is reduced, which may cause handling problems such as tearing of the film when processing the copper-clad laminate into a circuit board. is there. On the contrary, when the tensile elastic modulus of the polyimide insulating layer exceeds 10.0 GPa, the rigidity against bending of the copper-clad laminate increases, so that the bending stress applied to the copper wiring when bending the copper-clad laminate increases. The bending resistance is reduced.

  Although a commercially available polyimide film can be used as it is as the polyimide insulating layer, a polyamic acid solution is directly coated on a copper foil, and dried by heat treatment, because of easy control of thickness and physical properties. What is formed by the so-called cast method of curing is preferred. The polyimide insulating layer may be formed of only a single layer, but in consideration of the adhesion between the polyimide insulating layer and the first copper foil layer, a plurality of layers are preferable. When a polyimide insulating layer is made into multiple layers, another polyamic acid solution can be sequentially apply | coated and formed on the polyamic acid solution which consists of a different structural component. When a polyimide insulating layer consists of multiple layers, you may use the polyimide precursor resin of the same structure twice or more.

Preferably, the polyimide insulating layer has a plurality of layers, but as a specific example, the polyimide insulating layer preferably has a laminated structure including a low thermal expansion polyimide layer and a high thermal expansion polyimide layer. Here, the low thermal expansion polyimide layer has a thermal expansion coefficient of less than 35 × 10 ⁻⁶ / K, preferably 1 × 10 ⁻⁶ to 30 × 10 ⁻⁶ / K, particularly preferably 3 × 10 ^−6. Polyimide layer in the range of -25 x 10 ^-6 / K. Further, the high thermal expansion polyimide layer has a thermal expansion coefficient of 35 × 10 ⁻⁶ / K or more, preferably 35 × 10 ⁻⁶ to 80 × 10 ⁻⁶ / K, particularly preferably 35 × 10 ⁻⁶ to It refers to a polyimide layer in the range of 70 × 10 ⁻⁶ / K. The polyimide layer can be made into a polyimide layer having a desired thermal expansion coefficient by appropriately changing the combination of the raw materials used, the thickness, and the drying and curing conditions.

  The polyamic acid solution giving the polyimide insulating layer can be produced by polymerizing a known diamine and an acid anhydride in the presence of a solvent.

  Examples of diamine used as a raw material of polyimide include 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o- Toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4 ' -Diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2-Bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl Sulfone, 4,4'-diami Diphenyl ether, 3,3-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-Diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino- p-terphenyl, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-) Methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino- t-Butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m- Silylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2,2'-dimethyl-4, 4'-diaminobiphenyl, 3,7-diaminodibenzofuran, 1,5-diaminofluorene, dibenzo-p-dioxin-2,7-diamine, 4,4'-diaminobenzyl and the like.

  Moreover, as an acid anhydride used as a raw material of a polyimide, for example, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride, 2,2', 3,3 ' -Benzophenonetetracarboxylic acid dianhydride, 2,3,3 ', 4'-benzophenonetetracarboxylic acid dianhydride, naphthalene-1,2,5,6-tetracarboxylic acid dianhydride, naphthalene-1,2,5 4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl -1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,3,5,6,7- Hexahydronaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,7-dichloronaphthalene-1, 4,5,8-Tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloro Phthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 3,3 ', 4 2,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3, 3 '', 4,4 ''-p-terphenyltetracarboxylic dianhydride, 2,2 '', 3,3 ''-p-terphenyltetracarboxylic dianhydride, 2,3,3 ' ', 4' '-p-terphenyltetracarboxylic acid dianhydride, 2, 2-bis (2,3-dicarboxyphenyl) -propane dianhydride, 2, 2- bis (3,4- dicarboxyphenyl) ) -Propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, Bis (2,3-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxylate) Phenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, perylene-2,3 , 8,9-tetracarboxylic acid dianhydride, perylene-3,4,9,10-tetracarboxylic acid dianhydride, perylene-4,5,10,11-tetracarboxylic acid dianhydride, perylene-5, 6,11,12-tetracarboxylic acid dianhydride, phenanthrene-1,2,7,8-tetracarboxylic acid dianhydride, phenanthrene-1,2,6,7-tetracarboxylic acid dianhydride, phenanthrene-1 2,9,10-tetracarboxylic acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride, pyrrolidine -2,3,4,5-tetracarboxylic acid dianhydride, thiophene-, 3,4,5-tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 2,3,6,7 -Naphthalenetetracarboxylic acid dianhydride etc And the like.

  The diamine and the acid anhydride may be used alone or in combination of two or more. Further, examples of the solvent used for the polymerization include dimethylacetamide, N-methyl pyrrolidinone, 2-butanone, diglyme, xylene and the like, and one or more kinds can be used in combination.

In order to form a low thermal expansion polyimide layer having a thermal expansion coefficient of less than 35 × 10 ⁻⁶ / K, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid as an acid anhydride component of the raw material Acid dianhydride is preferably used as the diamine component, preferably 2,2'-dimethyl-4,4'-diaminobiphenyl or 2-methoxy-4,4'-diaminobenzanilide, and particularly preferably pyromellitic. It is preferable that acid dianhydride and 2,2'-dimethyl-4,4'-diaminobiphenyl be the main components of the starting materials.

Moreover, in order to form a high thermal expansion polyimide layer having a thermal expansion coefficient of 35 × 10 ⁻⁶ / K or more, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyl as an acid anhydride component of the raw material Tetracarboxylic acid dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride, 3,3', 4,4'-diphenyl sulfone tetracarboxylic acid dianhydride, and as a diamine component, It is preferable to use 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-diaminodiphenylether, 1,3-bis (4-aminophenoxy) benzene, particularly preferably pyromellitic It is preferable that acid dianhydride and 2,2′-bis [4- (4-aminophenoxy) phenyl] propane be the main components of the starting materials. In addition, the preferable glass transition temperature of the high thermal expansion polyimide layer obtained by doing in this way exists in the range of 300-400 degreeC.

  When the polyimide insulating layer has a laminated structure of a low thermal expansion polyimide layer and a high thermal expansion polyimide layer, preferably, the thickness ratio of the low thermal expansion polyimide layer to the high thermal expansion polyimide layer (low thermal expansion polyimide The layer / high thermal expansion polyimide layer) should be in the range of 1.5 to 6.0. If the value of this ratio is less than 1.5, the low thermal expansion polyimide layer with respect to the entire polyimide insulating layer becomes thin, so the dimensional change rate when etching the copper foil tends to be large, and when it exceeds 6.0, high thermal conductivity Since the intumescent polyimide layer becomes thin, the adhesion reliability between the polyimide insulating layer and the copper foil tends to be reduced.

  The copper-clad laminate of this embodiment has the ratio of the amount of change in cumulative dimensional change to the sum of the wiring width of the wiring pattern and the wiring spacing in a circuit board size (FPC size) of 10 mm, obtained by the following evaluation method. The in-plane variation in the test piece is ± 2% or less. When the value of this variation exceeds ± 2%, in the FPC processed from the copper-clad laminate, it causes the connection failure between the wires or between the wires and the terminals, which lowers the reliability and the yield of the circuit board. It becomes a factor. Here, with reference to FIGS. 1-7, the evaluation method of the dimensional stability of the copper clad laminated board used in this Embodiment is demonstrated. This evaluation method comprises the following steps (1) to (7).

(1) Process of preparing a test piece:
In this step, as illustrated in FIG. 1, the test strip 10 is prepared by cutting the long copper-clad laminate 100 into a predetermined length. In the following description, the longitudinal direction of the long copper-clad laminate 100 is defined as the MD direction, and the width direction is defined as the TD direction (the same applies to the test piece 10). It is preferable that the width (length in the TD direction) of the copper-clad laminate 100 and the cutting interval (length in the MD direction) be substantially equal so that the test piece 10 has a shape close to a square. The copper-clad laminate 100 has an insulating resin layer (not shown) and a copper layer laminated on one side or both sides of the insulating resin layer.

  What was prepared by arbitrary methods can be used for the copper clad laminated board 100 used as the object of this evaluation method. For example, the copper clad laminate 100 may be prepared by preparing a resin film, sputtering a metal thereon to form a seed layer, and then forming a copper layer by plating. The copper-clad laminate 100 may be prepared by laminating a resin film and a copper foil by a method such as thermocompression bonding. Furthermore, the copper clad laminate 100 may be prepared by applying a resin solution on copper foil to form an insulating resin layer.

(2) Step of forming a plurality of marks on a test piece:
In this process, as shown in FIG. 2, first, on the test piece 10, a virtual square 20 having sides parallel to the MD direction and the TD direction is assumed. The length of one side of the virtual square 20 can be set to a length according to the width (length in the TD direction) of the copper-clad laminate 100. Moreover, in order to include the area of the virtual square 20 in the evaluation target up to the limit of the range processed into the FPC in the case of picking a large number of pieces, it is preferable to set the area to cover the range processed into the FPC. Therefore, the length of one side of the square 20 is preferably in the range of 60 to 90% of the length in the TD direction (the width of the copper clad laminate 100) in the test piece 10, and in the range of 70 to 80%. It is more preferable to set it inside. For example, when the width (length in the TD direction) of the copper-clad laminate 100 is 250 mm, the length of one side of the virtual square 20 is preferably set within the range of 150 to 225 mm, 175 It is more preferable to set in -200 mm.

  Next, as shown in FIGS. 2 to 4, it includes a central region 21 including the center 20 a of the virtual square 20 and one of two corner portions 20 b sharing one side in the TD direction in the square 20. A plurality of marks including a linear arrangement are formed in the two corner areas 23a and 23b, respectively. The mark is, for example, a round hole 30 penetrating the test piece 10. The plurality of holes 30 are preferably formed at equal intervals. The hole 30 as a mark may be, for example, a polygonal shape such as a triangle or a rectangle. Further, the mark is not limited to the through hole, but may be, for example, a groove, a cut or the like formed on the test piece 10 as long as the position can be identified. It may be.

<Central region>
Since the center 20a of the virtual square 20 serves as a reference of coordinates for measuring the expansion and contraction of the test piece 10, in this evaluation method, the central region 21 including the center 20a is to be measured. In central region 21, as long as it includes a linear arrangement, the positions for forming the plurality of holes 30 are arbitrary, and may be arranged in, for example, a T shape or an L shape. From the above, it is preferable to use a cruciform that can be uniformly arranged in the MD direction and the TD direction. That is, as shown in FIG. 3, it is preferable to form the plurality of holes 30 in the MD direction and the TD direction along the cross shape passing through the center 20 a of the virtual square 20, and the crosses of the cross shape are virtual It is more preferable to arrange so that it may overlap with the center 20a of the square 20 of. In this case, the holes 30 overlapping the center 20a are counted as duplicates as the holes 30 constituting the arrangement in both the MD direction and the TD direction.

  Further, in the central region 21, in order to be able to accurately evaluate dimensional stability including variation in dimensional change in the plane of the test piece 10, the center 20a of the square 20 from the center 20a to the MD and TD directions, respectively. And at least 12.5% or more, preferably in the range of 12.5 to 32.5%, more preferably in the range of 12.5 to 25% with respect to the length of one side of the square 20. The holes 30 may be formed.

<Corner area>
The circumference of the two corner portions 20b sharing one side in the TD direction in the square 20 is a region that is most likely to expand and contract in the long copper-clad laminate 100 as shown in FIG. . Therefore, in this evaluation method, both of the two corner areas 23a and 23b including one each of the two corner portions 20b sharing one side in the TD direction in the square 20 are to be measured.

  In the corner areas 23a and 23b, the positions for forming the holes 30 are arbitrary as long as they include a linear arrangement, but for example, as shown in FIG. It is preferable to form in an L shape in the MD direction and the TD direction along two sides sandwiching 20b. In this case, the holes 30 overlapping the corner portion 20b are counted in duplicate as the holes 30 constituting the arrangement in both the MD direction and the TD direction. Although FIG. 4 shows only one corner area 23b, the same applies to the other corner area 23a.

  In the two corner areas 23a and 23b, both ends of one side in the TD direction of the square 20 (that is, in order to be able to accurately evaluate the dimensional stability including the dimensional change variation in the plane of the test piece 10). From the corner 20 b of the square 20 to the center side in the MD direction, at least 12.5% or more, preferably in the range of 12.5 to 32.5% with respect to the length of one side in the MD direction More preferably, the holes 30 are formed in the range of 12.5 to 25%.

  Further, in the two corner areas 23a and 23b, both ends of one side in the TD direction in the square 20 can be evaluated in order to be able to accurately evaluate the dimensional stability including the dimensional change variation in the plane of the test piece 10 That is, from the corner 20b of the square 20 to the center side in the TD direction, the range is at least 12.5% or more, preferably 12.5 to 32.5% with respect to the length of one side in the TD direction. It is preferable to form the holes 30 within the range, more preferably in the range of 12.5 to 25%.

In addition, in order to cover the surface of the test piece 10 so that the dimensional change of each part can be accurately grasped, the arrangement range between the holes 30 at both ends linearly arranged in the central region 21 and the corner region The arrangement range between the holes 30 at both ends linearly arranged in the same direction in 23 a and 23 b may overlap.
Specifically, at least positions of both ends of the plurality of holes 30 arranged in the MD direction in the central region 21 and in the plurality of holes 30 arranged in the MD direction in the two corner regions 23a and 23b, respectively. The positions of the holes 30 on the innermost side (the side far from the corner 20b) may be arranged to overlap when translated in the TD direction.
Similarly, at least the positions of the holes 30 closest to the corner areas 23a and 23b among the plurality of holes 30 arranged in the TD direction in the central area 21 and in the TD direction in the two corner areas 23a and 23b The positions of the innermost (farthest from the corner 20b) holes 30 among the plurality of holes 30 arranged may be arranged to overlap when translated in the MD direction.
In view of the above arrangement, it is most rational to arrange the plurality of holes 30 in a cruciform manner in the central region 21 and, in the two corner regions 23a and 23b, the plurality of holes 30 in an L shape. It is most reasonable to arrange in

  In the imaginary square 20 of the test piece 10, the range in which the holes 30 are formed can be adjusted by the size of the holes 30, the number of the holes 30, and the distance between the holes 30 and 30.

  The size of the hole 30 is preferably in the range of 20% or less of the distance between the hole 30 and the hole 30 in order to increase the detection accuracy of the dimensional change.

  The plurality of holes 30 formed in the central region 21 and the two corner regions 23a and 23b can be evaluated in order to accurately evaluate dimensional stability including variation in dimensional change in the plane of the test piece 10 In each of the direction and the TD direction, it is preferable to include at least 11 or more linear arrays, and more preferably include 20 or more linear arrays. Here, when the number of holes 30 is n, the number of intervals between the adjacent holes 30 and the holes 30 to be measured in the subsequent steps (3) and (5) is n-1. For example, the distance between the adjacent holes 30 and the holes 30 is nine when the number of the holes 30 is ten, and is twenty when the number of the holes 30 is twenty. In this case, the number of holes 30 is preferably the same in the MD direction and the TD direction.

  The distance between the hole 30 and the hole 30 is preferably in the range of 2 mm or more in order to increase the detection accuracy of the dimensional change.

(3) First measurement step:
In this process, the positions of the plurality of holes 30 are measured. Then, from the measurement results of the positions of the respective holes 30, the distance L0 between the adjacent holes 30 and the holes 30 is calculated. For example, if the number of holes 30 is 21, the distance L0 is determined for 20 intervals between the adjacent holes 30 and the holes 30. Here, the distance L0 between the adjacent holes 30 and the holes 30 means the distance from the center 30a of a certain hole 30 to the center 30a of the adjacent hole 30, as shown in FIG.

  The measurement of the position of the hole 30 is not particularly limited, and can be performed, for example, by a method of detecting the position of the hole 30 based on the image of the test piece 10.

  Although the measurement of the position of the hole 30 in this step may be performed subsequently to the above step (2), it is preferable to provide a step of adjusting the condition of the test piece 10 before measurement. As an example of condition adjustment of the test piece 10, humidity control processing can be mentioned. The humidity control process can be performed by leaving the test piece 10 stationary for a fixed time (for example, 24 hours in an environment of 23 ° C., 50 RH%) in a fixed environment.

(4) Etching process:
In this step, part or all of the copper layer of the test piece 10 is etched. In order to evaluate the dimensional stability in line with the reality, it is preferable to perform the contents of etching in accordance with the wiring pattern of the FPC formed from the copper clad laminate 100. When the test piece 10 is prepared from a double-sided copper-clad laminate, copper layers on both sides may be etched. When heat treatment is involved in the actual processing of the FPC, the test piece 10 may be heated at an arbitrary temperature after the etching.

(5) Second measurement process:
This step is a step of measuring the positions of the plurality of holes 30 again after the etching of the above (4). Then, from the measurement result of the position of each hole 30, the distance L1 between the adjacent hole 30 and the hole 30 is calculated. The measurement of the position of the hole 30 in this process can be performed by the same method as the process (3). The distance L1 between the adjacent holes 30 and the holes 30 means the distance from the center 30a of a certain hole 30 to the center 30a of the adjacent hole 30, as shown in FIG.

  Although the measurement of the position of the hole 30 in this step may be performed subsequently to the above step (4), it is preferable to provide a step of adjusting the condition of the test piece 10 as in the above step (3). In particular, when the condition adjustment is performed in the step (3), it is preferable to perform the condition adjustment under the same condition before measurement also in this step.

(6) Process of calculating dimensional change:
In this step, as shown in FIG. 5, for the same distance between the two holes 30 before and after etching, the distance L0 obtained in the first measurement step and the distance L1 obtained in the second measurement step The difference L1-L0 is calculated. Then, differences L1-L0 are similarly calculated for two or more, preferably ten or more, and more preferably all of the intervals between the holes 30 and the holes 30 arranged in the same linear shape. This difference L1-L0 is referred to as "dimension change amount Δ".

(7) Process of converting to wiring scale:
In this step, the amount of dimensional change Δ obtained in step (6) is converted to the scale of the wiring pattern in the FPC formed from the copper clad laminate 100, and the obtained conversion value is the wiring width and wiring of the wiring pattern. Expressed as a ratio to the sum of intervals. By this process, when the copper-clad laminate 100 subjected to the test is actually processed into an FPC, the influence of the dimensional change of the copper-clad laminate 100 on the wiring pattern of the FPC can be expressed in an easy-to-understand manner.

  In this process, first, the dimensional change amount Δ is converted to the scale of the wiring width / wiring interval in the L / S wiring pattern of the FPC to be formed from the copper clad laminate 100, and the converted dimensional change amount is accumulated. To determine the cumulative converted dimensional change. For example, when the distance L0 between the two holes 30 before etching is X mm, and the wiring width and wiring spacing in the wiring pattern of the FPC to be formed are 1 / Y of the distance L0, respectively, The dimensional change amount Δ is converted to a value when downsizing to a 2 × (1 / Y) scale, and the cumulative converted dimensional change amount of the 2 × (1 / Y) scale is obtained.

Cumulative converted dimensional change amount = [Σ _{i = 1} ⁱ (2 × Δ _i / Y)]

Next, the positional deviation ratio of the wiring is obtained from the cumulative converted dimensional change amount based on the following equation. The positional displacement ratio of the wiring represents the cumulative reduced dimensional change amount as a ratio to the sum of the wiring width (L mm) and the wiring interval (S mm) in the wiring pattern of L / S scheduled to be formed.
Wiring misalignment ratio (%) =
{[Σ _{i = 1} ⁱ (2 × Δ _i / Y)] / [L + S]} × 100

  By plotting the positional deviation ratio of the wiring in the MD direction and the TD direction in the FPC calculated as described above on a graph, an approximate straight line according to the FPC size can be obtained. Here, “FPC size” means the distance between the farthest ends of the plurality of wires formed in the FPC. The magnitude of the inclination of the graph means the magnitude of positional deviation of the wiring, and the magnitude of the variation of the inclination of the graph means the magnitude of in-plane dispersion of the positional displacement of the wiring.

  By this process, when the copper-clad laminate 100 subjected to the test is actually processed into a circuit, the influence of the dimensional change of the copper-clad laminate 100 on the wiring pattern of the FPC can be expressed in an easy-to-understand manner. Further, by creating a graph of the approximate straight line, it is possible to visualize and express the size of displacement of the wiring formed from the copper-clad laminate 100 as the test object and the in-plane variation according to the size of the FPC.

  In addition, after accumulating the dimensional variation Δ obtained in the step (6), the cumulative dimensional variation is formed of the copper clad laminate 100 from the wiring width / wiring interval in the L / S wiring pattern in the FPC It is also possible to convert it into a scale and find the cumulative converted dimensional change amount. For example, the dimensional change amount Δ at each interval is accumulated to obtain the cumulative dimensional change amount Σ. The accumulated dimensional change amount Σ can be calculated by the following equation.

Σ = Δ ₁ + Δ ₂ + Δ ₃ +... + Δ _i = Σ _{i = 1} ⁱ Δ _i

In the above equation, the symbol _{i i = 1} ⁱ represents the sum from 1 to i. Further, the dimensional variation Δ is determined from the distance L1 between the nth hole 30 and the n−1th hole 30 after etching to the nth hole 30 and the n−1th hole 30 before etching. And a value obtained by subtracting the distance L0 with (wherein n is an integer of 2 or more). Δ ₁ is the dimensional change of the first interval length (the distance between two adjacent holes 30), and Δ _i is the i-th (i means positive integer) interval It is a dimensional change amount of length.

  The cumulative dimensional change amount Σ can be obtained for either one or preferably both of the MD direction and the TD direction of the copper-clad laminate 100. The dimensional stability of the copper clad laminate 100 in the MD direction and the TD direction can be evaluated by the magnitude of the cumulative dimensional change amount 変 化. In addition, the scaled-up approximate straight line is obtained based on the actual measurement value of the cumulative dimensional change amount Σ.

  As described above, according to the present evaluation method, the dimensional change of the copper-clad laminate 100 can be evaluated with high accuracy including in-plane variations by the steps (1) to (7). . In addition, even in the case where many pieces are taken out of the copper-clad laminate 100, it is possible to evaluate the dimensional stability individually for each processing region to the FPC.

<Manufacturing of copper clad laminates>
The copper-clad laminate of this embodiment is manufactured, for example, by applying a polyimide precursor resin solution (also referred to as a polyamic acid solution) on the surface of the first copper foil, and then drying and curing it. can do. In the heat treatment step, the solvent in the polyamic acid is removed by drying at a temperature of less than 160 ° C., and then the temperature is raised stepwise in the temperature range of 150 ° C. to 400 ° C. It is done by In order to make the single-sided copper-clad laminate thus obtained into a double-sided copper-clad laminate, the single-sided copper-clad laminate and the copper foil (second copper foil) separately prepared therefrom are used The method of thermocompression-bonding at 400 degreeC is mentioned.

<FPC>
The copper-clad laminate of this embodiment is mainly useful as an FPC material. That is, the FPC according to an embodiment of the present invention can be manufactured by processing the copper foil of the copper-clad laminate of the present embodiment into a pattern by an ordinary method to form a wiring layer.

Synthesis Example 1
In a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, N, N-dimethylacetamide is placed, and 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) is placed in this reaction vessel. The solution was charged and dissolved in the vessel with stirring. Next, pyromellitic dianhydride (PMDA) was charged such that the total amount of charged monomers was 12 wt%. Then, stirring was continued for 3 hours to carry out a polymerization reaction to obtain a resin solution of polyamic acid a. The thermal expansion coefficient (CTE) of a 25 μm-thick polyimide film formed of polyamic acid a was 55 × 10 ⁻⁶ / K.

(Composition example 2)
N, N-Dimethylacetamide is placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, and 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is placed in this reaction vessel. Then, it was dissolved in the vessel with stirring. Next, 15 wt% of 3,3 ′, 4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) and pyromellitic dianhydride (PMDA) in the total amount of monomers charged, the molar ratio of each acid anhydride ( BPDA: PMDA was introduced to be 20:80. Then, stirring was continued for 3 hours to carry out a polymerization reaction to obtain a resin solution of polyamic acid b. The thermal expansion coefficient (CTE) of a 25 μm-thick polyimide film formed of polyamic acid b was 22 × 10 ⁻⁶ / K.

(Example)
<Manufacture of flexible copper clad laminates>
Resin solution (polyamic acid solution of polyamic acid a which is a polyimide precursor prepared in Synthesis Example 1 on the surface of a long copper foil (for example, GHY 5-93F-HA-V2 foil manufactured by JX Nippon Mining & Metals Co., Ltd.) It was applied and dried. Subsequently, a resin solution of polyamic acid b and polyamic acid a prepared in Synthesis Example 2 and Synthesis Example 1 was sequentially applied and dried in the same manner, and then cured, to form a 25 μm thick polyimide layer. . In the heat treatment step, the solvent in the polyamic acid is removed by drying at a temperature of less than 160 ° C., and then the temperature is raised stepwise in the temperature range of 150 ° C. to 400 ° C. It was done by During this process, no occurrence of corrugation was observed in the single-sided copper clad laminate. A double-sided copper-clad laminate was produced by thermocompressing the thus-obtained single-sided copper-clad laminate and a separately prepared copper foil at 300 to 400 ° C.

From the obtained double-sided copper-clad laminate, a copper-clad laminate 1 (end width: 250 mm) was prepared as a material for a sample for evaluation.
Copper-clad laminate 1:
Long, double-sided copper clad laminate manufactured by the method of the embodiment, thickness of insulating layer: 25 μm, CTE of insulating layer; 17 ppm / K, first copper foil layer; GHY 5 manufactured by JX Nippon Mining & Metals Co., Ltd. -93F-HA-V2 foil, thickness of first copper foil layer: 12 μm, CTE of first copper foil layer; 17 ppm, tensile modulus of elasticity of first copper foil layer 18 GPa, of first copper foil layer Product of thickness and tensile modulus; 216.

(Comparative example)
A copper-clad laminate 2 (end width: 250 mm) was prepared as a material of an evaluation sample.
Copper clad laminate 2:
Long, general-purpose laminate material, thickness of insulating layer: 25 μm, copper foil layer; BHY-82F-HA foil manufactured by JX Nippon Mining & Metals Co., Ltd., thickness of copper foil layer; 12 μm, polyimide film by lamination method A copper foil made by thermocompression bonding on both sides of Kaneka Corporation (trade name; Pixio). Tensile modulus of elasticity 14 GPa of the copper foil layer, product of thickness of copper foil layer and tensile modulus; 168.

<Preparation of evaluation sample>
The above copper-clad laminate 1 or 2 was cut into a length of 250 mm in the MD direction to make MD: 250 mm × TD: 250 mm. As shown in FIG. 6, an imaginary square shape was assumed in the range of MD: 200 mm × TD: 200 mm in the copper-clad laminate after cutting. In each of two left and right corner areas (Left and Right) including one corner each of two corners sharing one side in the TD direction of this virtual square, and a central area (Center) including the center of the virtual square, A sample for evaluation was prepared by continuously performing 21 holes at 2.5 mm intervals in the MD and TD directions. In addition, the drill of 0.105 mm diameter was used for the drilling process.

<Evaluation of dimensional stability>
The position of each hole before and after etching and removing all of the copper foil layers on both sides of the sample for evaluation using a non-contact CNC image measurement machine (Mitutoyo, trade name; Quick Vision QV-X404 PIL-C) Was measured. From the measured values, the dimensional change amount and the cumulative dimensional change amount of the distance between two adjacent holes before and after etching were calculated.

  Long copper-clad laminates 1 and 2 were prepared, and evaluation samples 1 and 2 were prepared as shown in FIG. For each of the evaluation samples 1 and 2, the positions of the holes before and after the etching at Center, Left, and Right were measured. From the measured values, the dimensional change of the distance between two adjacent holes before and after etching and the cumulative dimensional change of their total (20 locations) were calculated.

  Based on the evaluation results of the copper-clad laminate 1, Table 1 shows cumulative dimensional change amounts and variations in the MD direction, and FIG. 8 shows the relationship between the FPC size and the wiring misalignment rate. Similarly, based on the evaluation results of the copper-clad laminate 2, the cumulative dimensional change amount of MD and the variation thereof are shown in Table 2, and FIG. 9 shows the relationship between the FPC size and the wiring misalignment rate. In Tables 1 and 2 and FIGS. 8 and 9, the cumulative dimensional change rate and the cumulative dimensional change amount at Left, Center, and Right are shown as a cumulative converted dimensional change amount converted to an assumed FPC size of 10 mm. The variation in the whole range of Center and Right is also shown. The numerical value of "range" in the table means median ± upper and lower range.

  From these results, with respect to the circuit wiring board (L / S = 0.025 mm / 0.0025 mm) formed using the copper-clad laminate 1 and the copper-clad laminate 2 as materials, the positional deviation ratio of the wiring and the in-plane of the test piece It is confirmed that the variation in dimensional change rate at the time of evaluation can be evaluated, and the variation in wiring misalignment rate at each FPC size in the copper clad laminate 1 of the example is compared with that in the copper clad laminate 2 of the comparative example. It was confirmed that it was small.

  Although the embodiments of the present invention have been described in detail for the purpose of illustration, the present invention is not limited to the above-described embodiments, and various modifications are possible.

  DESCRIPTION OF SYMBOLS 10 ... Test piece, 20 ... Virtual square, 20a ... Center, 20b ... Corner part, 21 ... Central area, 23a, 23b ... Corner area, 30 ... Hole, 100 ... Copper-clad laminated board

Claims (5)

A copper-clad laminate comprising a polyimide insulation layer and a first copper foil layer laminated on one side of the polyimide insulation layer,
The thermal expansion coefficient of the polyimide insulating layer is in the range of 10 ppm / K to 30 ppm / K,
The first copper foil layer is characterized in that the thickness is 13 μm or less, and the product of the thickness (μm) and the tensile elastic modulus (GPa) is in the range of 180 to 250. Copper clad laminate.   2. The copper clad laminate according to claim 1, wherein the polyimide insulating layer is formed by applying a precursor solution of polyimide to the first copper foil layer and drying it, followed by imidization.   The copper clad laminate according to claim 1 or 2, further comprising a second copper foil layer laminated on the surface of the polyimide insulating layer opposite to the first copper foil layer. The following steps (1) to (7);
(1) A step of preparing a test piece by cutting the long copper-clad laminate into a predetermined length,
(2) Assuming that the longitudinal direction of the copper-clad laminate is the MD direction and the width direction is the TD direction, an imaginary square shape having sides parallel to the MD direction and the TD direction is assumed in the test piece, A linear array is provided in each of a central area including the center of a virtual square and two corner areas including one of two corners sharing one side in the TD direction in the virtual square. Forming a plurality of marks including
(3) A first measurement step of measuring the positions of the plurality of marks and calculating the distance L0 between the adjacent marks,
(4) etching a part or all of the copper layer of the test piece;
(5) A second measurement step of measuring the positions of the plurality of marks after etching and calculating the distance L1 between the adjacent marks,
(6) A step of calculating a difference L1-L0 between the distance L0 obtained in the first measurement step and the distance L1 obtained in the second measurement step for the same two marks before and after the etching ,as well as,
(7) The difference L1-L0 is converted to the scale of the wiring pattern in the circuit board formed from the copper clad laminate to obtain the cumulative converted dimensional change amount, and the obtained cumulative converted dimensional change amount is the wiring pattern Process expressed as a ratio to the sum of the wiring width and wiring spacing
The in-plane variation in the test piece of the ratio of the cumulative dimensional change amount to the sum of the wiring width of the wiring pattern and the wiring interval in a circuit board size of 10 mm obtained by the test method including The copper clad laminate according to any one of Items 1 to 3.   The circuit board formed by carrying out a wiring circuit process of the copper foil of the copper clad laminated board of any one of Claim 1 to 4.

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