JP2006261270A - Laminated body for flexible printed wiring board and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the initial adhesive force between a polyimide resin layer and a copper foil, to reduce as much as possible the decrease in adhesive force after heat load, and to be excellent in durability and to cope with fine pitch wiring processing. Provided is a laminate for a flexible printed wiring board.
SOLUTION: A polyimide precursor resin solution is applied to a copper foil having at least Ni and Zn attached to the surface, and heat-treated in an atmosphere having an oxygen concentration of 1 to 10 vol%, whereby the polyimide precursor resin solution is obtained. It is a manufacturing method of the laminated body for flexible printed wiring boards which dries and hardens and forms a polyimide resin layer on copper foil, Comprising: 90 of copper foil after hold | maintaining the laminated board obtained above at 150 degreeC for 168 hours A method for producing a laminate for a flexible printed wiring board having a peel peel adhesive strength of 1.0 kN / m or more, and a laminate for a flexible printed wiring board obtained by this production method.
[Selection figure] None

Description

  The present invention provides a manufacturing method for obtaining a laminate for a flexible printed wiring board that exhibits a high initial adhesive force and can maintain a high adhesive force even after a thermal load, and a flexible print obtained by using this manufacturing method The present invention relates to a laminate for a wiring board.

  In recent years, electronic devices have been increasingly miniaturized, densified, and highly functionalized, and there is a demand for adapting to fine pitch fine processing of flexible printed wiring boards. For this reason, it is required that the conductor itself forming the flexible printed wiring board be made thin and have a low profile (flattening of the copper foil surface), and at the same time, the adhesive strength between the copper foil as the conductor and the insulating resin as the insulator. Is strongly required to be stronger. On the other hand, when the surface of the conductor in contact with the insulating resin is further flattened, a decrease in the adhesive force at the interface between the conductor and the insulating resin becomes a problem. About this adhesive strength, not only immediately after manufacturing the flexible printed wiring board, but also after being used for a long time in a heating load or in a moist heat environment from the viewpoint of high-density mounting conditions and the usage environment of the flexible printed wiring board. Therefore, it is necessary to develop a flexible printed wiring board having excellent heat resistance and durability.

  In general, flexible printed wiring boards do not have an adhesive layer, but are based on a “two-layer cast” in which a polyimide resin is directly coated on a copper foil to form a heat-resistant insulating layer. It is known that it is excellent in terms of efficiency and insulation reliability. Furthermore, in order to provide a material for flexible printed wiring boards that can handle fine pitch wiring, the adhesive strength between the conductor and the insulating resin is improved, especially after thermal load, without lowering other characteristics. Research and development to prevent it is actively conducted.

  Under such circumstances, a two-layer printed wiring board in which a conductive metal layer is formed on a polyimide film by a method such as vacuum deposition, sputtering, ion plating, or plating in consideration of the correspondence to fine pitch wiring. Has been proposed. However, in these flexible printed wiring boards, even if the adhesive force between the metal layer (conductor) and the polyimide film (insulating layer) is relatively satisfactory at the initial stage (90 ° C of copper foil with 80 μm pitch wiring) The adhesive strength after peeling off is 0.6 kN / m or more), and after being used for a long time, or after being exposed to a load due to heating or a moist heat environment, it is not always satisfactory.

Further, in Patent Document 1 (Japanese Patent Laid-Open No. 1-321687), a “three-layer plating” in which a metal vapor deposition layer is provided on a film surface via a resin layer, and a thick metal layer is laminated thereon by a plating method. The technique concerning is proposed. However, when an epoxy resin or an acrylic resin is used as the resin layer, the adhesion between the metal layer (conductor) and the film (insulator) is improved, but the resin layer itself has a problem in terms of heat resistance. .
Further, according to Patent Document 2 (Japanese Patent Laid-Open No. 4-282844), a wiring board that is improved in adhesive force by using a polyimide resin into which a siloxane-based diamine is introduced as an insulating layer and that is satisfactory in terms of heat resistance is also provided. However, when left in a wet bath at 85 ° C and 85% RH for a long time and then immersed in a solder bath at a temperature exceeding 200 ° C, a metal layer repels, a so-called phenomenon called popcorn occurs. The adhesive strength with the layer is also significantly reduced.
Patent Document 3 (Japanese Patent Application Laid-Open No. 2-284923) discloses a method using an end group-modified imide oligomer having a crosslinkable unsaturated functional group at the end group as an insulating layer. Although the decrease in the adhesive strength is suppressed and the popcorn phenomenon hardly occurs, the adhesive strength at room temperature is not satisfactory.

Furthermore, in Patent Document 4 (Japanese Patent Laid-Open No. 11-92917), a polyimide film is subjected to plasma treatment to form a thin film (intermediate layer) of one or more kinds of metals selected from nickel, chromium and titanium, and further a copper thin film is formed. It describes about the metal polyimide resin laminated body obtained by doing. According to this method, the adhesive force between copper and the polyimide film is improved, but there is a problem in that the etching efficiency is poor and high precision is difficult because the copper foil film and the intermediate layer need to be etched. In addition, there is a problem that a chromium alloy film-forming cost and a wastewater treatment cost are incurred, and an etching waste liquid treatment places a heavy burden on the environment.
JP-A-1-321687 JP-A-4-282844 JP-A-2-284923 JP-A-11-92917

  By the way, when forming a flexible printed wiring board by forming a polyimide resin layer on the surface of the copper foil by a casting method, as a means for improving the adhesive force between the copper foil and the polyimide resin layer, a metal adhered to the surface of the copper foil In general, the kind and the amount of adhesion thereof are adjusted, or treatment with a silane coupling agent is performed. However, in order to balance all of adhesive properties, processing properties, electrical properties, etc., the adjustment range of metal type and adhesion amount is limited, and the effect of adjusting these is the effect of polyimide resin layer There are variations depending on the characteristics of the resin to be formed. Therefore, it is practically difficult to improve the adhesive force only by adjusting the metal type and the amount of adhesion. On the other hand, when the surface of the copper foil is treated with a silane coupling agent, although it is effective in improving the adhesive force, it may adversely affect the heat resistance and durability of the obtained flexible printed wiring board.

  In the case where the polyimide resin layer is formed on the surface of the copper foil by the casting method, the present invention optimizes the conditions in the curing process of curing the polyimide precursor resin solution coated on the surface of the copper foil. A flexible printed wiring board that enhances the initial adhesion between the resin layer and the copper foil, and can reduce the decrease in adhesion after thermal load as much as possible. It also has excellent durability and can handle fine pitch wiring. It aims at providing the laminated body for use.

In order to solve the above problems, the present inventors have studied in detail, and as the Ni concentration attached to the surface of the copper foil increases, the adhesion after heating load is improved. Confirmed that it had an undesirable effect. In addition, the Ni forms an oxide between the copper foil and the polyimide resin layer, and the presence of the nickel oxide stabilizes the interface between the copper foil and the polyimide resin layer, and the nickel oxide We obtained the knowledge that it works as a barrier layer that prevents diffusion of Cu (I) from the copper foil side to the polyimide resin layer side, and serves to prevent deterioration of the polyimide resin.
And based on these findings, the present inventors apply a polyimide precursor resin solution to a copper foil having Ni and Zn attached to the surface, and heat-treat in an atmosphere having a predetermined concentration of oxygen. It was found that the laminate obtained by the above was excellent in the initial adhesive force between the polyimide resin layer and the copper foil, and the decrease in the adhesive force after the thermal load was reduced as much as possible, thereby completing the present invention.

  That is, in the present invention, the polyimide precursor resin is applied by applying a polyimide precursor resin solution to a copper foil having at least Ni and Zn attached to the surface, and heat-treating in an atmosphere having an oxygen concentration of 1 to 10 vol%. A method for producing a laminate for a flexible printed wiring board in which a solution is dried and cured to form a polyimide resin layer on a copper foil, the copper foil after the laminate obtained above is held at 150 ° C. for 168 hours It is a manufacturing method of the laminated body for flexible printed wiring boards which has a 90 degree direction peeling adhesive force of 1.0 kN / m or more.

In the present invention, the copper foil needs to have at least Ni and Zn attached to its surface. Preferably, the adhesion amount of Ni on the surface of the copper foil is 2.5 to 5.0 μg / cm ² in terms of metallic nickel, and Ni / (Ni + Zn) representing the adhesion amount ratio of Ni and Zn A range of 0.70 to 0.90 is preferred. When the adhesion amount of Ni is less than 2.5 μg / cm ² , the initial peel between the copper foil and the polyimide resin layer is lowered, and conversely when it is more than 5.0 μg / cm ² , the resulting laminate for a flexible printed wiring board is obtained. In the tin plating step after circuit processing is performed on the body, a phenomenon that tin abnormally precipitates occurs, which may cause problems such as deterioration of workability and poor electrical reliability. Also, the deposition amount of Zn, 0.25~50μg / cm ² of metal zinc terms, it's good preferably 1.0~40μg / cm ^2. Adhesion amount of the zinc is decreased adhesive strength between the copper foil and the polyimide resin layer after the thermal aging less than 0.25 [mu] g / cm ^2, such as an acid to be used in the processing step is more than 50 [mu] g / cm ² on the opposite The chemical solution may erode the interface between the polyimide resin layer and the copper foil, which may cause a decrease in the adhesive strength.

  When Ni / (Ni + Zn) representing the adhesion amount ratio of Ni and Zn is smaller than 0.70, in other words, when there is a large amount of Zn, it prevents diffusion of Cu (I) on the surface of the copper foil as described later. The formation of the expected continuous phase of nickel oxide is hindered, and the effect of oxygen concentration in the heat treatment atmosphere on the bonding strength cannot be expressed. On the other hand, when it exceeds 0.90, the appropriate amount of Zn decreases and the initial bonding Strength development cannot be expected. About Ni and Zn adhering to the surface of copper foil, it is thought that each is oxidized by the heat treatment in the present invention. At this time, the diffusion of various metals on the surface of the copper foil as described later is suppressed. It is presumed that the oxide of Ni functions to stabilize the interface between the polyimide resin layer and the copper foil. Excessive presence of Zn prevents the oxidation of Ni, prevents the formation of a nickel oxide layer that stabilizes the bonding interface, and prevents the effect of suppressing the diffusion of Cu (I). On the other hand, an appropriate amount of Zn is indispensable for increasing the adhesive strength, and Ni / (Ni + Zn) is an important index when expressing an appropriate adhesion amount ratio of Ni and Zn.

  As means for attaching Ni and Zn to the surface of the copper foil, for example, electroplating method, electroless plating method, vapor deposition method, sputtering method and the like can be mentioned, and control of the amount of metal adhesion is relatively easy. It is preferable to use an electroplating method. The plating bath used at this time is preferably an acidic bath containing at least Ni and Zn.

  In addition, in the present invention, the surface of the copper foil other than the above metals, B, Al, P, Ti, Cr, Mn, Fe, Co, Ag, In, Zr, Sn, Nb, Mo, Ru, Rh, Pd, At least one metal selected from Pb, Ta, W, Ir and Pt, or an alloy thereof may be attached. These metals are considered to function to control the particle size of the surface-treated metal made of Ni and Zn and the above metals and to strengthen the adhesion interface.

  Further, the copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil, and the thickness thereof is not particularly limited, but usually 5 to 80 μm is used, preferably 9 to 35 μm is used. Moreover, about the surface roughness of copper foil, if Rz of the surface by which the polyimide precursor resin solution is coated is 1.0 micrometer or less, it is preferable from a viewpoint which can improve the effect of this invention more. In addition, said Rz shows the ten-point average roughness (JIS B 0601-1994) in surface roughness.

  Moreover, in this invention, it is preferable to provide a chromium oxide layer with respect to the surface of the copper foil to which Ni and Zn were adhered. The presence of this chromium oxide layer can further improve the adhesive strength between the polyimide resin layer and the copper foil, and can also suppress the occurrence of rust on the copper foil. The chromium oxide layer can be formed by a general chromate treatment as described in, for example, Japanese Patent Publication No. 61-33906.

In the present invention, the polyimide precursor resin solution to be coated on the surface of the copper foil (the side to which Ni and Zn are attached) is obtained by polymerizing a known diamine and acid anhydride in the presence of a solvent. Can do.
For example, as tetracarboxylic dianhydride used, pyromellitic anhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4 '-Benzophenonetetracarboxylic dianhydride (BTDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic anhydride (DSDA), 3,3 ', 4,4'-diphenylsulfonetetracarboxylic acid Anhydride, 4,4′-oxydiphthalic anhydride, etc. can be mentioned, preferably pyromellitic anhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic anhydride (DSDA). As aromatic diamines, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 1,3-bis (4-aminophenoxy) benzene (TPR-E), 4, 4′-bis (4-aminophenoxy) biphenyl (BAPB), 4,4′-diaminodiphenyl ether, 2′-methoxy 4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, 2 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 4,4'-diaminobenzanilide, etc., preferably 2,2 ' -Bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 1,3-bis (4-aminophenoxy) benzene (TPR-E), 4,4'-bis (4-aminophenoxy) biphenyl ( BAPB).
Each of these tetracarboxylic dianhydrides and aromatic diamines may be used alone or in combination of two or more.

Examples of the solvent include dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and these can be used alone or in combination.
The viscosity of the polymerized polyimide precursor resin solution is preferably in the range of 500 cps to 35,000 cps from the viewpoints of wettability to the copper foil surface, uniform film thickness control, and ease of coating. It is good. Moreover, about the polyimide precursor resin solution coated on the surface of copper foil, although depending on the use of the laminated body for wiring boards obtained, the polyimide resin layer with a film thickness of about 12 μm to 60 μm is formed on the surface of the copper foil. It is good to be done.

  In the present invention, the polyimide precursor resin solution is applied to the surface of the copper foil, and the polyimide precursor is heat-treated in an atmosphere having an oxygen concentration of 1 to 10 vol%, preferably 2 to 5 vol%. The body resin solution is dried and cured to form a polyimide resin layer on the copper foil. As for the atmosphere in the heat treatment, it is preferable that the oxygen concentration be the above value, and other examples include nitrogen (N), helium (He), argon (Ar), and the like. Moreover, about this heat processing, although it changes with the kind of polyimide resin, the magnitude | size of copper foil, etc., generally, it is made for the total of heating time to be about 20 to 40 minutes in the temperature range of 100-400 degreeC. Is good.

  These steps of applying the polyimide precursor resin solution to the surface of the copper foil and then heat-treating may be repeated twice or more. That is, a polyimide precursor resin solution is applied to the surface of the copper foil, and then subjected to heat treatment under predetermined conditions to dry and cure the polyimide precursor resin solution, and then the polyimide precursor resin solution is applied to the surface again. It may be coated and subjected to a predetermined heat treatment. In addition, when applying a polyimide precursor resin solution in multiple times, the same polyimide precursor resin solution may be used and a different thing may be used.

By applying a polyimide precursor resin solution to this metal adhesion surface using a copper foil having Ni and Zn adhered on at least the surface, and performing a heat treatment under a predetermined oxygen partial pressure environment, The adhesive strength between the copper foil and the polyimide resin layer is excellent in the initial stage of manufacture, and has excellent adhesive strength even after being used for a long period of time or after being exposed to a load caused by heating or a moist heat environment. To guess.
Through various experiments, the present inventors have come to the idea that the oxides of Ni and Zn formed at the interface between the copper foil and the polyimide resin layer are related to the improvement in adhesion. When a polyimide precursor resin solution is applied to a copper foil with Ni and Zn attached to the surface and this polyimide precursor resin solution is dried and cured, heat treatment is performed in a predetermined oxygen partial pressure environment. It has been found that an oxide of the metal is formed between the copper foil and the polyimide resin layer, and that the adhesion between the copper foil and the polyimide resin layer is improved by controlling the thickness of the oxide. That is, Ni and Zn attached to the surface of the copper foil form an oxide at the interface between the copper foil and the polyimide resin layer by the heat treatment. These metal oxides easily react with polyamic acid (polyimide precursor resin solution), form a strong chemical bond between the polyimide resin layer and the copper foil, and have an adhesive force between the copper foil and the polyimide resin layer. It is thought that it contributes to improvement. In addition, the metal oxide formed at the interface between the copper foil and the polyimide resin layer stabilizes the interface between the copper foil and the polyimide resin layer, and the polyimide from the copper foil side, which is considered to be one of the causes of deterioration of the polyimide resin layer. The function of preventing the diffusion of Cu (I) to the resin layer side was also confirmed.

  By the way, since it is thought that a polyimide resin deteriorates when exposed to a high temperature in the presence of oxygen, when polyamic acid (polyimide precursor resin solution) coated on the surface of a copper foil is dried and cured, Is generally performed in an inert gas atmosphere. In addition, it is considered that the surface of the line becomes rough due to the metal oxide existing between the polyimide resin layer and the copper foil when patterning the obtained laminate, and adversely affects the linearity of the pattern. For this reason, the heat treatment is generally performed under an inert gas atmosphere as described above.

  On the other hand, the present inventors have found that an appropriate oxygen concentration exists in the atmosphere of the heat treatment based on the above knowledge, and completed the present invention. The presence of oxygen in the heat treatment atmosphere stabilizes the interface between the copper foil and the polyimide resin layer, and improves the adhesive force between the copper foil and the polyimide resin layer. On the contrary, when the oxygen concentration in the heat treatment exceeds a predetermined concentration, the thickness of the oxide film at the interface between the copper foil and the polyimide resin layer becomes too thick, and the adhesion between the copper foil and the polyimide resin layer decreases. Since the oxide film itself is also fragile, it is considered that the adhesive force cannot be improved as a result.

  By applying a polyimide precursor resin solution to this metal adhesion surface using a copper foil having Ni and Zn adhered on at least the surface, and performing a heat treatment under a predetermined oxygen partial pressure environment, Adhesive strength between the copper foil and the polyimide resin layer is excellent in the initial stage of manufacture, and excellent adhesive strength is obtained even after long-term use or after being exposed to a load due to heating or a moist heat environment. The laminate obtained in this way is excellent in heat resistance and durability, and can be used for fine pitch wiring processing. Therefore, it can be suitably used for a flexible printed wiring board. And in this invention, such a laminated body can be manufactured cheaply by simple control.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these. In the following examples, unless otherwise noted, various evaluations are as follows.

[Measurement of adhesive strength]
The adhesive strength between the copper foil and the insulating layer is that after forming a polyimide resin layer on the copper foil, circuit processing is performed to a line width of 0.1 mm, and a tensile tester manufactured by Toyo Seiki Co., Ltd. (Strograph-M1) The copper foil was peeled off in the 90 ° direction and measured. The initial adhesive force described in this specification means an adhesive force measured as it is without heat treatment after the laminate is manufactured. In addition, a heat resistance test was performed in which the laminate with the initial adhesive strength measured was held at 150 ° C. in an atmospheric environment, and the adhesive strength was measured 48 hours, 96 hours, and 168 hours after the heat resistance test. .

  Next, the synthesis of the polyimide resin precursor polyamic acid solution used in the following Examples and Comparative Examples will be described in detail.

[Synthesis Example 1]
Put n-methylpyrrolidinone in a reaction vessel equipped with a thermocouple and stirrer and capable of introducing nitrogen, immerse this reaction vessel in ice water, and then add pyromellitic anhydride (PMDA) to the reaction vessel. Thereafter, 4,4′-diaminodiphenyl ether (hereinafter referred to as DAPE) and 2′-methoxy 4,4′-diaminobenzanilide (hereinafter referred to as MABA) were added. The total amount of monomers was 15 wt%, the molar ratio of each diamine was MABA: DAPE = 60: 40, and the molar ratio of acid anhydride to diamine was 0.98: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 15,000 cps.

[Synthesis Example 2]
A reaction vessel equipped with a thermocouple and a stirrer and into which nitrogen can be introduced is charged with n-methylpyrrolidinone. The reaction vessel is immersed in ice water, and then the reaction vessel is charged with PMDA / 3,4'3,4'- Biphenyltetracarboxylic dianhydride (hereinafter referred to as BTDA) was charged, and then 4,4′-diaminodiphenyl ether (hereinafter referred to as DAPE) was charged. The total amount of monomers added was 15 wt%, the molar ratio of each acid anhydride was BTDA: PMDA = 70: 30, and the molar ratio of acid anhydride to diamine was 1.03: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 3,200 cps.

[Synthesis Example 3]
Place n-methylpyrrolidinone in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, immerse this reaction vessel in ice water and then put 3,3 ', 4,4'-diphenyl in the reaction vessel. Sulfonetetracarboxylic dianhydride (hereinafter referred to as DSDA) and PMDA were charged, and then 1,3-bis (4-aminophenoxy) benzene (hereinafter referred to as TPE-R) was charged. The total amount of monomers charged was 15 wt%, the molar ratio of each acid anhydride was DSDA: PMDA = 90: 10, and the molar ratio of acid anhydride to diamine was 1.03: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. The solution viscosity of polyamic acid which was kept stirring at room temperature for 3 hours was 3,200 cps.

[Synthesis Example 4]
A reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen was charged with N, N-dimethylacetamide, and 4,4′-diamino-2,2′-dimethylbiphenyl (DADMB) and 1,3- Bis (4-aminophenoxy) benzene (DAB) was dissolved in the vessel with stirring. Then 3,3 '4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride were added. The molar ratio of each diamine was DADMB: BAB = 90: 10, and the molar ratio of each acid anhydride was BPDA: PMDA = 20: 79. Thereafter, stirring was continued for 3 hours, and pyromellitic anhydride (hereinafter PMDA) was added, and then 4,4′-diaminodiphenyl ether (hereinafter DAPE) and 2′-methoxy 4,4′-diaminobenzanilide (hereinafter MABA). ). The total amount of monomers was 15 wt%, the molar ratio of each diamine was MABA: DAPE = 60: 40, and the molar ratio of acid anhydride to diamine was 0.98: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 15,000 cps.

[Synthesis Example 5]
Put n-methylpyrrolidinone in a reaction vessel equipped with a thermocouple and stirrer and capable of introducing nitrogen, immerse this reaction vessel in ice water, and then add pyromellitic anhydride (PMDA) to the reaction vessel. Thereafter, 4,4′-diaminodiphenyl ether (hereinafter referred to as DAPE) and 2′-methoxy 4,4′-diaminobenzanilide (hereinafter referred to as MABA) were added. The total amount of monomers was 15 wt%, the molar ratio of each diamine was MABA: DAPE = 60: 40, and the molar ratio of acid anhydride to diamine was 0.98: 1.0. Thereafter, stirring was further continued, and the reaction vessel was removed from the ice water when the temperature in the reaction vessel was in the range of room temperature to ± 5 ° C. Stirring was continued for 3 hours at room temperature, and the solution viscosity of the resulting polyamic acid was 15,000 cps.

Copper foil A having a Ni / Zn-based surface metal treatment and Ni and Zn adhered to the surface (thickness 18 μm, Rz = 0.71 μm, Ni adhesion amount 7.4 μg / cm ² , Ni / (Ni + Zn) = 0 .81) is applied on the surface with a dimethylacetamide solution of polyamic acid shown in Synthesis Example 1 (12 to 18%) and dried, and then cured using the polyamic acid solution shown in Synthesis Example 4. The polyimide film was uniformly coated using a bar coater so that the polyimide film thickness was 40 μm.
Next, after the copper foil A coated with polyamic acid was dried at 120 ° C. to 150 ° C. for 30 minutes in an open atmosphere, the oxygen concentration in the mixed gas of nitrogen and oxygen was 2% (vol%) with a precision flow meter. ) 160 ° C. × 20 minutes, 250 ° C. × 30 minutes, 350 using a small vacuum electric furnace (Miwa Seisakusho Co., Ltd., MT-1100A + G, vacuum attainment level 60 Pa, the same applies below) with controlled atmosphere A laminate was obtained by curing by heating at 10 ° C. for 10 minutes.

  A pattern of 1 mm width was processed on the copper foil in the laminate obtained above, the copper foil was peeled off in the 90 ° direction, and the 90 ° peel strength was measured. The initial adhesive strength was 2.30 kN / m. It was. Moreover, when the laminated body was subjected to a heat resistance test and the adhesive strength after each time passed was measured, it was 1.62 kN / m after 168 hours passed. A graph summarizing the initial adhesive strength and the adhesive strength by the heat resistance test is shown in FIG.

  Moreover, about the obtained laminated body, the oxidation scale of the back surface of copper foil was confirmed with the color tone using the laser microscope. Since the oxidation degree of the surface corresponding to the resist surface of the copper foil is thought to affect the line linearity during circuit processing, color tone observation is performed on the resist surface of the copper foil of the laminate obtained by heat treatment. When the oxide scale was confirmed, no change in color tone before the heat treatment was observed. Furthermore, in order to confirm the linearity of the line at the time of circuit processing, when it evaluated using the laser microscope (2000-times multiplication factor), it turned out that favorable linearity is shown (FIG. 2). In the laser micrograph shown in FIG. 2, two relatively dark colored pieces are copper foils of the circuit portion, and are shown at the center between the two circuits and at the end of each circuit. The thin part of the relatively thin color is the exposed part of the polyimide resin.

A laminate was manufactured in the same manner as in Example 1 except that the heat treatment was performed with the oxygen concentration in the mixed gas of nitrogen and oxygen being 5 vol%.
When the pattern of 1 mm width was processed into the copper foil in the obtained laminate and the 90-degree peel strength was measured, the initial adhesive strength was 1.97 kN / m. Moreover, when the heat resistance test was done about this laminated body and the adhesive force after each time progress was measured, it was 1.64 kN / m after 168 time progress. A graph summarizing the initial adhesive strength and the adhesive strength by the heat resistance test is shown in FIG.

A laminate was manufactured in the same manner as in Example 1 except that the heat treatment was performed with the oxygen concentration in the mixed gas of nitrogen and oxygen being 10 vol%.
When the pattern of 1 mm width was processed into the copper foil in the obtained laminate and the 90-degree peel strength was measured, the initial adhesive strength was 1.84 kN / m. Moreover, when the heat resistance test was done about this laminated body and the adhesive force after each time progress was measured, it was 1.62 kN / m after 168 time progress. A graph summarizing the initial adhesive strength and the adhesive strength by the heat resistance test is shown in FIG.

Copper foil B with Ni / Zn surface metal treatment applied and Ni and Zn adhered to the surface (thickness 18 μm, Rz = 1.1 μm, Ni adhesion amount 15 μg / cm ² , Ni / (Ni + Zn) = 0.40 ) Is applied to the surface of the polyamic acid dimethylacetamide solution (12-18%) shown in Synthesis Example 2 and dried, and then cured using the polyamic acid solution shown in Synthesis Example 5 to cure the polyimide. It applied uniformly using the bar coater so that a film thickness might be set to 40 micrometers.
Next, after drying by air open for 30 minutes from 120 ° C to 150 ° C, small vacuum electric whose atmosphere is controlled so that the oxygen concentration in the mixed gas of nitrogen and oxygen becomes 2% (vol%) with a precision flow meter Using a furnace, heat treatment was performed at 160 ° C. for 20 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 10 minutes to obtain a laminate.
When the pattern of 1 mm width was processed into the copper foil in the obtained laminate and the 90-degree peel strength was measured, the initial adhesive strength was 1.46 kN / m. Moreover, when the heat resistance test was done about this laminated body and the adhesive force after each time progress was measured, it was 1.38 kN / m after 168 time progress. A graph summarizing the initial adhesive strength and the adhesive strength by the heat resistance test is shown in FIG.

Copper foil C with Ni / Zn-based surface metal treatment and Ni and Zn adhered to the surface (thickness 18 μm, Rz = 0.6 μm, Ni adhesion amount 14 μg / cm ² , Ni / (Ni + Zn) = 0.79) ) Is coated with a dimethylacetamide solution (12 to 18%) of the polyamic acid shown in Synthesis Example 3 and dried, and then further cured using the polyamic acid solution shown in Synthesis Example 4 to cure the polyimide. It applied uniformly using the bar coater so that a film thickness might be set to 40 micrometers.
Next, after drying by air open for 30 minutes from 120 ° C to 150 ° C, small vacuum electric whose atmosphere is controlled so that the oxygen concentration in the mixed gas of nitrogen and oxygen becomes 2% (vol%) with a precision flow meter Using a furnace, heat treatment was performed at 160 ° C. for 20 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 10 minutes to obtain a laminate.
When the pattern of 1 mm width was processed into the copper foil in the obtained laminate and the 90-degree peel strength was measured, the initial adhesive strength was 1.14 kN / m. Moreover, when the heat resistance test was done about this laminated body and the adhesive force after each time progress was measured, it was 0.88 kN / m after 168 time progress. A graph summarizing the initial adhesive strength and the adhesive strength by the heat resistance test is shown in FIG.

[Comparative Example 1]
In the same manner as in Example 1, the surface of the copper foil A was uniformly applied using a bar coater so that the polyimide film thickness after curing was 40 μm using the polyamic acid solution shown in Synthesis Examples 1 and 4. .
Next, after drying by air open for 30 minutes from 120 ° C to 150 ° C, heat treatment at 160 ° C for 20 minutes, 250 ° C for 30 minutes, 350 ° C for 10 minutes using a small vacuum electric furnace in a nitrogen atmosphere. And cured to obtain a laminate.
A 1 mm wide pattern was processed on the copper foil in the obtained laminate, and the initial 90 degree peel strength (initial adhesive strength) and the adhesive strength by the heat resistance test were measured. . The results are shown in FIG.

[Comparative Example 2]
Comparison except that heat treatment is performed at 160 ° C for 20 minutes, 250 ° C for 30 minutes, and 350 ° C for 10 minutes using a small vacuum electric furnace in an atmosphere where the oxygen concentration in the mixed gas of nitrogen and oxygen is 1 vol%. A laminate was obtained in the same manner as in Example 1.
A 1 mm wide pattern was processed on the copper foil in the obtained laminate, and the initial 90 degree peel strength (initial adhesive strength) and the adhesive strength by the heat resistance test were measured. . The results are shown in FIG.

[Comparative Example 3]
Compared to heat treatment at 160 ° C for 20 minutes, 160 ° C for 30 minutes, and 350 ° C for 10 minutes using a small vacuum electric furnace in an atmosphere where the oxygen concentration in the mixed gas of nitrogen and oxygen is 20 vol%. A laminate was obtained in the same manner as in Example 1.
When a 1 mm width pattern was processed on the copper foil in the laminate obtained above, the copper foil was peeled off in the 90 ° direction and the 90 ° peel strength was measured. The initial adhesive strength was 1.7 kN / m. It was. Moreover, when the heat resistance test was done about this laminated body and the adhesive force after each time passage was measured, it was 1.2 kN / m after 168 hours passage. FIG. 1 shows a graph summarizing the initial adhesive strength and the adhesive strength obtained from the heat resistance test. The decrease in the adhesive strength after 96 hours of the heat resistance test was confirmed, and the oxidation on the back side of the copper foil was severe. As shown in FIG. 5, the linearity of the line during circuit processing was evaluated using a laser microscope (magnification 2000 times), and it was found that excellent linearity was not obtained. In the laser micrograph shown in FIG. 5, the two relatively thick colored copper foils are the copper foils of the circuit portion, and are shown at the center between the two circuits and at the ends of the respective circuits. The thin part of the relatively thin color is the exposed part of the polyimide resin.

[Comparative Example 4]
In the same manner as in Example 4, using the polyamic acid solution shown in Synthesis Examples 2 and 5 uniformly on the surface of the copper foil B, using a bar coater so that the polyimide film thickness after curing is 40 μm. did.
Next, after drying at 120 ° C. to 150 ° C. for 30 minutes in an open atmosphere, heat treatment is performed at 160 ° C. × 20 minutes, 250 ° C. × 30 minutes, 350 ° C. × 10 minutes using a small vacuum electric furnace in a nitrogen atmosphere. And cured to obtain a laminate.
A 1 mm wide pattern was processed on the copper foil in the obtained laminate, and the initial 90-degree peel strength (initial adhesive strength) and the adhesive strength according to the heat resistance test were measured. . The results are shown in FIG.

[Comparative Example 5]
In the same manner as in Example 4, using the polyamic acid solution shown in Synthesis Examples 2 and 5 uniformly on the surface of the copper foil B, using a bar coater so that the polyimide film thickness after curing is 40 μm. did.
Next, after drying by air open from 120 ° C to 150 ° C for 30 minutes, the atmosphere is controlled so that the oxygen concentration in the mixed gas of nitrogen and oxygen becomes 20% (vol%) with a precision flow meter. Using a furnace, heat treatment was performed at 160 ° C. for 20 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 10 minutes to obtain a laminate.
A 1 mm wide pattern was processed on the copper foil in the obtained laminate, and the initial 90-degree peel strength (initial adhesive strength) and the adhesive strength according to the heat resistance test were measured. . The results are shown in FIG.

[Comparative Example 6]
In the same manner as in Example 5, using the polyamic acid solution shown in Synthesis Examples 3 and 5 on the surface of copper foil C, uniformly apply using a bar coater so that the polyimide film thickness after curing is 40 μm. did.
Next, after drying at 120 ° C. to 150 ° C. for 30 minutes in an open atmosphere, heat treatment is performed at 160 ° C. × 20 minutes, 250 ° C. × 30 minutes, 350 ° C. × 10 minutes using a small vacuum electric furnace in a nitrogen atmosphere. And cured to obtain a laminate.
A 1mm width pattern was processed on the copper foil in the resulting laminate, and the initial 90 degree peel strength (initial adhesive strength) and the adhesive strength by the heat resistance test were measured. Although there was no, the initial adhesive strength and the adhesive strength after the heat resistance test were both low. The results are shown in FIG.

[Comparative Example 7]
In the same manner as in Example 5, using the polyamic acid solution shown in Synthesis Examples 3 and 5 on the surface of copper foil C, uniformly apply using a bar coater so that the polyimide film thickness after curing is 40 μm. did.
Next, after drying by air open from 120 ° C to 150 ° C for 30 minutes, the atmosphere is controlled so that the oxygen concentration in the mixed gas of nitrogen and oxygen becomes 20% (vol%) with a precision flow meter. Using a furnace, heat treatment was performed at 160 ° C. for 20 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 10 minutes to obtain a laminate.
A 1mm width pattern was processed on the copper foil in the obtained laminate, and the initial 90 degree peel strength (initial adhesive strength) and the adhesive strength by the heat resistance test were measured. However, as a result of evaluating the linearity of the line during circuit processing using a laser microscope (magnification 2000 times), it was found that excellent linearity was not obtained.

  According to the method for producing a laminate in the present invention, the laminate as described above can be easily provided at low cost, and various production methods for flexible printed wiring boards such as casting, laminating, sputtering, and spin coating methods. Application to is possible.

FIG. 1 is a graph showing initial adhesive strength and adhesive strength in a heat resistance test for the laminates according to Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 2 is a laser micrograph for confirming the linearity of the line during circuit processing of the laminate in Example 1. FIG. 3 is a graph showing the initial adhesive strength and the adhesive strength in the heat resistance test for the laminates according to Example 4 and Comparative Examples 4 to 5. FIG. 4 is a graph showing the initial adhesive strength and the adhesive strength in the heat resistance test of the laminates according to Example 5 and Comparative Examples 6-7. FIG. 5 is a laser micrograph for confirming the linearity of the line during circuit processing of the laminate in Comparative Example 3.

Claims (4)

  A polyimide precursor resin solution is applied to a copper foil having at least Ni and Zn attached to the surface, and the polyimide precursor resin solution is dried and cured by heat treatment in an atmosphere having an oxygen concentration of 1 to 10 vol%. A method for producing a laminate for a flexible printed wiring board in which a polyimide resin layer is formed on a copper foil, and the copper foil after the laminate obtained above is held at 150 ° C. for 168 hours is peeled off in the 90 ° direction. The manufacturing method of the laminated body for flexible printed wiring boards characterized by having adhesive strength of 1.0 kN / m or more. The Ni adhesion amount on the surface of the copper foil is 2.5 to 5.0 µg / cm ² , and Ni / (Ni + Zn) representing the adhesion amount ratio of Ni and Zn is 0.70 to 0.90. The manufacturing method of the laminated body for flexible printed wiring boards as described in any one of.   The method for producing a laminate for a flexible printed wiring board according to claim 1 or 2, wherein the surface of the copper foil on the side on which the polyimide precursor resin solution is applied has a surface roughness Rz of 1.0 µm or less.   It is a laminated board for flexible printed wiring boards obtained using the manufacturing method of the laminated body for flexible printed wiring boards of Claims 1-3, Comprising: 90 degree direction pulling of the copper foil after hold | maintaining at 150 degreeC for 168 hours A laminate for a flexible printed wiring board, wherein the peel adhesive strength is 1.0 kN / m or more.