JP2006012987A - Manufacturing method of printed-wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a printed-wiring circuit capable of improving migration resistance particularly in a flexible printed circuit regarding a printed circuit with a circuit pattern in which electronic parts are mounted. <P>SOLUTION: A circuit pattern 2 composed of a conductive material is formed on the surface of an insulating base material 1a composed of an insulating material. On the surface of the circuit pattern 2, an oxide film 2a is formed by thermal oxidation processing. On this circuit pattern 2, the press cure of a cover layer 3 composed of an adhesive-bond layer 3a and an insulating layer 3b is carried out for constituting a flexible printed circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a printed wiring board having a circuit pattern on which an electronic component is mounted, and particularly relates to improvement of migration resistance in a flexible printed circuit.

  Conventionally, FPC (flexible printed circuit) is known as an electronic circuit using a printed wiring board. As shown in FIG. 3, the FPC roughly forms a circuit pattern 102 by etching a CCL (Copper Clad Lamination) 101, and then, on the CCL 201 with the circuit pattern, The cover layer (CL: Cover Lay) 103 is produced by pressure bonding (press cure).

  The CCL has a two-layer structure of an insulating base material 101a made of an insulating material such as polyimide resin and a conductive material layer 101b such as copper which is formed on the surface of the insulating base material 101a and becomes a circuit pattern 102. . The CCL 101 may also have a three-layer structure in which an adhesive layer (not shown in FIG. 3) is interposed between the insulating base material 101a and the conductive material layer 101b.

  The cover layer 103 includes an adhesive layer 103a and an insulating layer 103b made of an insulating material such as polyimide resin. The cover layer 103 is bonded to the CCL 201 with a circuit pattern with the adhesive layer 103a side as the circuit pattern 102 side.

  That is, the flexible printed circuit is configured such that the adhesive layer 103a is sandwiched between the insulating base material 101a and the insulating layer 103b, and the circuit pattern 102 is embedded in the adhesive layer 103a.

  Further, a rigid-print circuit (R-F), which is a multilayer printed circuit, is manufactured by laminating and bonding a rigid print circuit (RPC) on both sides of such a flexible printed circuit.

  By the way, in such a printed wiring board, the problem is that ion migration (hereinafter referred to as “migration”) occurs due to the application of voltage to the circuit pattern 102 and the presence of moisture in the adhesive layer 103a.

  This migration is a phenomenon in which the metal material forming the circuit pattern 102 moves into the adhesive layer 103a that is an insulating layer. That is, the metal material forming the circuit pattern 102 is ionized in the adhesive layer 103 a at the + pole in the circuit pattern 102, and the ionized metal material is deposited at the − pole in the circuit pattern 102. When this precipitation phenomenon progresses and the deposited metal material reaches the positive electrode, dielectric breakdown occurs between the positive electrode and the negative electrode in the circuit pattern 102.

  In particular, in a flexible printed circuit that is an inner layer portion of a rigid-flex printed circuit, the problem is that the progress of precipitation is faster than when the flexible printed circuit is used alone.

  Conventionally, in a multilayer printed circuit such as a rigid-flex printed circuit, as described in Patent Document 1 and Patent Document 2, the adhesion between the circuit pattern 102 and the adhesive layer 103a is improved, and migration resistance is improved. For the purpose of improvement or the like, it has been proposed to form an oxide film on the surface portion of the circuit pattern 102. It is considered that the presence of this oxide film suppresses the dissolution of the metal material at the positive electrode in the circuit pattern 102 and can suppress migration.

Such an oxide film is produced by immersing the CCL 201 with a circuit pattern in an alkaline aqueous solution containing sodium chlorite or sodium hydroxide before the cover layer 103 is pressure-bonded to the CCL 201 with a circuit pattern. .
JP-A-8-204336 JP-A-11-354923

  However, in the above-described flexible printed circuit, when the CCL 201 with a circuit pattern is immersed in an alkaline aqueous solution, depending on the pH of the alkaline aqueous solution, the insulating substrate 101a of the CCL 201 with a circuit pattern made of polyimide resin or the like, There is a possibility that the adhesive layer (not shown in FIG. 3) between the substrate 101a and the circuit pattern 102 is affected by the alkaline aqueous solution. If the insulating base material 101a or the adhesive layer is affected, there is a possibility that a hole is formed in the insulating base material 101a or the like. Therefore, if these insulating base materials 101a and the like are affected by the alkaline aqueous solution, a flexible printed circuit cannot be configured.

  It was also found that migration could not be sufficiently suppressed when the circuit pattern surface was oxidized with an alkaline aqueous solution.

  Therefore, in a flexible printed circuit, it is not appropriate to form an oxide film on the surface portion of the circuit pattern 102 using an alkaline aqueous solution.

  Accordingly, an object of the present invention is to improve migration resistance without affecting an insulating base material or an adhesive layer in a printed wiring board having a circuit pattern on which an electronic component is mounted, particularly a flexible printed circuit. It is in providing the manufacturing method of a printed wiring board.

  The present inventors have found that the above problem can be solved by forming an oxide film by thermal oxidation on the surface portion of the circuit pattern after forming the circuit pattern in the CCL.

  When an oxide film is formed by thermal oxidation, the insulating base material in CCL and the adhesive layer between the insulating base material and the circuit pattern are not affected, and a good oxide film is formed on the surface portion of the circuit pattern. can do.

  And, it is considered that the presence of such an oxide film suppresses the dissolution of the metal material at the positive electrode in the circuit pattern and suppresses migration.

  In a CCL having a two-layer structure in which a circuit pattern is formed on an insulating substrate, the temperature for performing thermal oxidation is preferably 140 ° C. to 300 ° C., and the treatment time is preferably 30 minutes or more. When the treatment is performed at 140 ° C. or lower or less than 30 minutes, a sufficient oxide film is not formed, and when the treatment is performed at a temperature higher than 300 ° C., a flexible printed circuit can be manufactured due to thermal deterioration of an insulating substrate made of polyimide or the like. Because it will disappear.

  In the CCL having a three-layer structure in which a circuit pattern is formed on an insulating substrate via an adhesive layer, the temperature for performing thermal oxidation is 140 ° C. to 200 ° C., and the processing time is 30 minutes. The above is desirable. When the treatment is performed at 140 ° C. or less or for less than 30 minutes, a sufficient oxide film is not formed. When the treatment is performed at a temperature higher than 200 ° C., the adhesive layer between the insulating substrate and the circuit pattern is thermally deteriorated. Moreover, it is because the adhesiveness of the cover layer to the adhesive layer is lowered by the reaction of the flame retardant in the adhesive layer.

  Therefore, the printed wiring board manufacturing method according to the present invention includes at least one of the following configurations.

[Configuration 1]
The method for manufacturing a printed wiring board according to the present invention includes forming a circuit pattern made of a conductive material on a surface of an insulating base material made of an insulating material, and forming an oxide film on the surface of the circuit pattern by thermal oxidation treatment. It is a feature.

[Configuration 2]
The present invention is a method for manufacturing a printed wiring board having Configuration 1, wherein the thermal oxidation treatment for forming an oxide film is performed by heating a circuit pattern to 140 ° C. to 300 ° C. It is.

[Configuration 3]
In the method for manufacturing a printed wiring board according to the present invention, an adhesive layer is formed on the surface of an insulating substrate made of an insulating material, a circuit pattern made of a conductive material is formed on the adhesive layer, and the circuit pattern An oxide film is formed on the surface by thermal oxidation treatment.

[Configuration 4]
The present invention is a method of manufacturing a printed wiring board having Configuration 3, wherein the thermal oxidation treatment for forming the oxide film is performed by heating the circuit pattern to 140 ° C. to 200 ° C. It is.

[Configuration 5]
The present invention provides a method for manufacturing a printed wiring board having any one of configurations 1 to 4, wherein a cover layer including an adhesive layer and an insulating layer is formed on a surface of a circuit pattern on which an oxide film is formed. It is characterized by.

[Configuration 6]
A printed wiring board manufacturing method according to the present invention uses a printed wiring board manufactured by the printed wiring board manufacturing method described in Structure 5 as an inner layer, and laminates a rigid printed wiring board on both sides of the printed wiring board. And a rigid-flex printed circuit board.

  In the method for manufacturing a printed wiring board according to the present invention, an oxide film is formed on the surface of the circuit pattern by thermal oxidation. This oxide film can be satisfactorily formed without destroying the insulating base material or the adhesive layer or damaging the characteristics of the insulating base material or the adhesive layer.

  That is, this invention can provide the manufacturing method of the printed wiring board which can improve migration resistance in the printed wiring board which has a circuit pattern in which an electronic component is mounted especially a flexible printed circuit. is there.

  In addition, the present invention can provide a printed wiring board, particularly a flexible printed circuit, which can provide a printed wiring board with improved migration resistance.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In this embodiment, the method for manufacturing a printed wiring board according to the present invention is a so-called flexible printed circuit (FPC) manufacturing method.

  FIG. 1 is a process diagram showing a first embodiment of a method for producing a printed wiring board according to the present invention.

  In this printed wiring board manufacturing method, as shown in FIG. 1, first, a predetermined circuit pattern 2 is formed in the CCL 1 by etching a CCL (Copper Clad Lamination) 1. This CCL 31 with a circuit pattern is composed of an insulating base material 1a made of an insulating material such as a polyimide resin, and a conductive material layer 1b such as copper which is formed on the surface of the insulating base material 1a and becomes a circuit pattern 2. It is configured as.

  Then, an oxide film 2a is formed on the surface of the circuit pattern 2 by thermal oxidation treatment. This thermal oxidation treatment is desirably performed by heating the circuit pattern 2 to 140 ° C. to 300 ° C. for 30 minutes or more.

  Next, a cover layer (CL: Cover Lay) 3 is pressure-bonded (press cured) on the CCL 31 with a circuit pattern. The cover layer 3 is composed of an adhesive layer 3a and an insulating layer 3b made of an insulating material such as polyimide resin. The cover layer 3 is bonded to the CCL 31 with a circuit pattern with the adhesive layer 3a side as the circuit pattern 2 side.

  Thus, the flexible printed circuit in which the adhesive layer 3a is sandwiched between the insulating substrate 1a and the insulating layer 3b and the circuit pattern 2 is embedded in the adhesive layer 3a is configured.

  Furthermore, a rigid-flex printed circuit (R-F), which is a multilayer printed circuit, is produced by laminating and bonding rigid printed circuits (RPC) 4, 4 on both sides of such a flexible printed circuit. .

  FIG. 2 is a process diagram showing a second embodiment of a method for manufacturing a printed wiring board according to the present invention.

  In this printed wiring board manufacturing method, as shown in FIG. 2, an insulating base material 11a made of an insulating material such as a polyimide resin, and copper or the like which is formed on the surface of the insulating base material 11a and becomes a circuit pattern 12 are used. The conductive material layer 11b and the adhesive layer 11c interposed between the insulating base material 11a and the conductive material layer 11b are used to form a flexible printed circuit using the CCL 11 configured as a three-layer structure.

  Also in this method, the CCL 11 is etched, thereby forming a predetermined circuit pattern 12 in the CCL 11 and configuring the CCL 51 with a circuit pattern.

  Then, an oxide film 12a is formed on the surface of the circuit pattern 12 by thermal oxidation treatment. This thermal oxidation treatment is desirably performed by heating the circuit pattern 2 to 140 ° C. to 200 ° C. for 30 minutes or more.

  Next, a cover layer (CL: Cover Lay) 3 is pressure-bonded (press cured) on the CCL 51 with a circuit pattern. The cover layer 3 is composed of an adhesive layer 3a and an insulating layer 3b made of an insulating material such as polyimide resin. The cover layer 3 is bonded to the CCL 51 with a circuit pattern with the adhesive layer 3a side as the circuit pattern 12 side.

  Thus, the flexible printed circuit in which the adhesive layer 3a is sandwiched between the insulating substrate 11a and the insulating layer 3b and the circuit pattern 12 is embedded in the adhesive layer 3a is configured.

  Furthermore, the rigid-print circuit which is a multilayer printed circuit is produced by laminating and bonding the rigid printed circuits 4 and 4 on both sides of such a flexible printed circuit.

  Hereinafter, the Example and comparative example about the manufacturing method of the printed wiring board concerning this invention are given.

  As the insulating substrate, “Kapton EN” (trade name: manufactured by Toray DuPont), which is a polyimide film, was used.

[Example of a two-layer structure CCL]
A comb circuit pattern of [L / S] = 80/80 μm (both the circuit width and the circuit interval were 80 μm) was formed on a CCL having a two-layer structure in which a copper foil was laminated without using an adhesive on polyimide. After that, as shown in the following [Table 1], as the thermal oxidation treatment, it is held for different treatment times at different treatment temperatures for each of Examples 1 to 6, and is applied to the surface portion of the circuit pattern. An oxide film was formed.

  A flexible printed circuit was prepared by precuring the cover layer on the CCL of each of these examples. As the cover layer, an experimentally formed layer made of an adhesive that easily migrates was used.

  For each example, a voltage of 50 V was applied at 85 ° C. and 85% RH, and the insulation resistance value after 250 hours and the occurrence of migration were examined. The presence or absence of migration was determined by observing the presence or absence of metal deposition in the circuit pattern of the flexible printed circuit with a microscope.

  These results are shown in the column of “Insulation resistance (Ω)” and “Migration” in the following [Table 1].

  The determination based on the insulation resistance value when applying a voltage of 50 V at 85 ° C. and 85% RH for 250 hours is only a guideline, and the actual use conditions do not necessarily match this standard. Absent.

In addition, a rigid-print circuit is formed by laminating a rigid-print circuit on both sides of the flexible printed circuit of each of these examples, and a voltage of 50 V is applied at 85 ° C. and 85% RH, and the resistance value is 10 ⁷ Ω or more. Investigate the time to maintain.

These results are shown in the column of “RF resistance maintenance time (h)” in the following [Table 1].

In each of these examples, the insulation resistance value after 250 hours is a sufficiently high value, the occurrence of migration is not recognized, and even when configured as a rigid-flex printed circuit, the resistance value is 10 ^It is a sufficiently long time to maintain ⁷ Ω or more.

[Comparative example of two-layer structure CCL]
Similar to the above-described two-layer structure CCL, a circuit pattern of [L / S] = 80/80 μm was formed on a two-layer CCL in which a copper foil was laminated on polyimide without using an adhesive.

  Thereafter, the thermal oxidation treatment is not performed for the comparative example 1, and the thermal oxidation treatments for the comparative examples 2 to 6 are different at different treatment temperatures for each comparative example as shown in [Table 1]. An oxide film was formed on the surface portion of the circuit pattern while maintaining the treatment time.

  A flexible printed circuit was prepared by precuring the cover layer on the CCLs of these comparative examples.

  For each comparative example, a voltage of 50 V was applied at 85 ° C. and 85% RH, and the insulation resistance value after 250 hours and the presence or absence of the occurrence of migration were examined. Judgment was made by observing the presence or absence of metal deposition in the circuit pattern of the circuit).

  These results are shown in the column of “Insulation resistance (Ω)” and “Migration” in the following [Table 1].

Also, a rigid-print circuit is formed by laminating a rigid-print circuit on both sides of the flexible printed circuit of each comparative example, and a voltage of 50 V is applied at 85 ° C. and 85% RH, and the resistance value is 10 ⁷ Ω or more. Investigate the time to maintain.

  These results are shown in the column of “RF resistance maintenance time (h)” in the following [Table 1].

In each of these comparative examples, the insulation resistance value after 250 hours cannot be said to be a sufficiently high value, the occurrence of migration is observed, and when configured as a rigid-flex printed circuit, the resistance value is 10 ^7. Sufficient time was not secured for maintaining Ω or more.

  That is, in the present invention, it was confirmed that the migration resistance can be improved in a printed wiring board, particularly in a flexible printed circuit.

[Example of three-layer structure CCL]
A circuit pattern of [L / S] = 80/80 μm (both the circuit width and the circuit interval are 80 μm) was formed on a CCL having a three-layer structure in which a copper foil was laminated on polyimide via an adhesive. Then, as shown in the following [Table 2], as thermal oxidation treatment, it is held for different treatment times at different treatment temperatures for each of Examples 1 to 4, and is applied to the surface portion of the circuit pattern. An oxide film was formed.

  A flexible printed circuit was prepared by precuring the cover layer on the CCL of each of these examples. As the cover layer, an experimentally formed layer made of an adhesive that easily migrates was used.

  For each example, a voltage of 50 V was applied at 85 ° C. and 85% RH, and the insulation resistance value after 250 hours and the presence or absence of migration were examined. Judgment was made by observing the presence or absence of metal deposition in the circuit pattern of the circuit).

  These results are shown in the column of “Insulation resistance (Ω)” and “Migration” in the following [Table 2].

  The determination based on the insulation resistance value when applying a voltage of 50 V at 85 ° C. and 85% RH for 250 hours is only a guideline, and the actual use conditions do not necessarily match this standard. Absent.

In addition, a rigid-print circuit is formed by laminating a rigid-print circuit on both sides of the flexible printed circuit of each of these examples, a voltage of 50 V is applied at 85 ° C. and 85% RH, and a resistance value is 10 ⁷ Ω or more. Investigate the time to maintain.

These results are shown in the column of “RF resistance maintenance time (h)” in the following [Table 2].

In each of these examples, the insulation resistance value after 250 hours is a sufficiently high value, the occurrence of migration is not recognized, and even when configured as a rigid-flex printed circuit, the resistance value is 10 ^It is a sufficiently long time to maintain ⁷ Ω or more.

[Comparative example of three-layer structure CCL]
Similar to the above-described three-layer structure CCL example, a circuit pattern of [L / S] = 80/80 μm was formed on a three-layer structure CCL in which a copper foil was laminated on polyimide via an adhesive.

  Thereafter, the thermal oxidation treatment is not performed for the comparative example 1, and the thermal oxidation treatments for the comparative examples 2 to 5 are different for each comparative example at different treatment temperatures as shown in [Table 2]. An oxide film was formed on the surface portion of the circuit pattern while maintaining the treatment time.

  A flexible printed circuit was prepared by precuring the cover layer on the CCLs of these comparative examples.

  For each comparative example, a voltage of 50 V was applied at 85 ° C. and 85% RH, and the insulation resistance value after 250 hours and the presence or absence of the occurrence of migration were examined. Judgment was made by observing the presence or absence of metal deposition in the circuit pattern of the circuit).

  These results are shown in the column of “Insulation resistance (Ω)” and “Migration” in the following [Table 2].

Also, a rigid-print circuit is formed by laminating a rigid-print circuit on both sides of the flexible printed circuit of each comparative example, and a voltage of 50 V is applied at 85 ° C. and 85% RH, and the resistance value is 10 ⁷ Ω or more. Investigate the time to maintain.

  These results are shown in the column of “RF resistance maintenance time (h)” in the following [Table 2].

In each of these comparative examples, the insulation resistance value after 250 hours cannot be said to be a sufficiently high value, the occurrence of migration is observed, and when configured as a rigid-flex printed circuit, the resistance value is 10 ^7. Sufficient time was not secured for maintaining Ω or more.

  That is, in the present invention, it was confirmed that the migration resistance can be improved in a printed wiring board, particularly in a flexible printed circuit.

[When the surface of the circuit pattern is oxidized with an alkaline aqueous solution]
Next, it was confirmed whether or not migration was suppressed when the surface of the circuit pattern was oxidized using an alkaline aqueous solution.

As treatment conditions, an alkaline aqueous solution of [NaClO ₂ ]; 15 g / l, [NaOH]; 5 g / l was used as a chemical solution, and the treatment temperature was 85 ° C., and the treatment was performed for 1 minute.

As in the previous example, a voltage of 50 V was applied at 85 ° C. and 85% RH, and the insulation resistance value after 250 hours was examined. As a result, it was 3.2 × 10 ⁷ Ω. Further, when the presence or absence of migration occurred was examined, migration occurred.

Also, a rigid-print circuit is formed by laminating a rigid-print circuit on both sides of the flexible printed circuit of each of these comparative examples, and a voltage of 50 V is applied at 85 ° C. and 85% RH, and the resistance value is 10 ⁷ Ω or more. It was 10.25 hours when the time which maintains this was investigated.

  That is, it was found that even if the surface of the circuit pattern was oxidized using an alkaline aqueous solution, migration could not be sufficiently suppressed. This seems to be because a dense oxide film is not formed by oxidation with an alkaline aqueous solution.

It is process drawing which shows 1st Embodiment of the manufacturing method of the printed wiring board which concerns on this invention. It is process drawing which shows 2nd Embodiment of the manufacturing method of the printed wiring board which concerns on this invention. It is process drawing which shows the manufacturing method of the conventional printed wiring board.

Explanation of symbols

1,11 CCL
DESCRIPTION OF SYMBOLS 1a, 11a Insulating base material 1b, 11b Conductive material layer 11c Adhesive layer 2,12 Circuit pattern 2a, 12a Oxide film 3 Cover layer 3a Adhesive layer 3b Insulating layer 4 Rigid printed circuit

Claims (6)

A circuit pattern made of a conductive material is formed on the surface of an insulating base material made of an insulating material,
An oxide film is formed on the surface of the circuit pattern by thermal oxidation treatment. A method for manufacturing a printed wiring board, comprising: The method for manufacturing a printed wiring board according to claim 1, wherein the thermal oxidation treatment for forming the oxide film is performed by heating the circuit pattern to 140 ° C to 300 ° C. Form an adhesive layer on the surface of an insulating substrate made of an insulating material,
A circuit pattern made of a conductive material is formed on the adhesive layer,
An oxide film is formed on the surface of the circuit pattern by thermal oxidation treatment. A method for manufacturing a printed wiring board, comprising: The method of manufacturing a printed wiring board according to claim 3, wherein the thermal oxidation treatment for forming the oxide film is performed by heating the circuit pattern to 140 ° C to 200 ° C. The printed wiring board according to any one of claims 1 to 4, wherein a cover layer made of an adhesive layer and an insulating layer is formed on a surface of the circuit pattern on which the oxide film is formed. Manufacturing method. Using the printed wiring board manufactured by the method for manufacturing a printed wiring board according to claim 5 as an inner layer,
A method of manufacturing a printed wiring board, wherein a rigid-print printed circuit board is formed by laminating a rigid printed circuit board on both sides of the printed circuit board.

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