JP2006269502A - Printed wiring board and electronic circuit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board in which, even when a circuit pattern is miniaturized using "a semi-additive method", adhesion strength of the circuit pattern to an insulating base material is ensured, and the circuit pattern is prevented from being peeled off from the insulating material in processes, after the formation of the circuit pattern such as a terminal plating process and the mounting process of an electronic component or the like, or is prevented from being peeled off from the insulating material in a usage environment after completion of mounting. <P>SOLUTION: The printed wiring board is provided with the insulating base material 1 consisting of an insulating material; the circuit pattern 2 consisting of a conductive material and formed on the surface of the insulating base material 1; a cover layer 4 consisting of an insulating material and formed on the insulating base material to cover the circuit pattern 2, and having an opening 6 corresponding to a mounting position 5 of an electronic component 101 in this circuit pattern 2; and an oxygen preventing film 7 formed on a portion corresponding to the opening 6 of at least the cover layer 4 of the rear surface of the insulating material 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board having a circuit pattern on which an electronic component is mounted and an electronic circuit device using the printed wiring board, and more particularly to a printed wiring which ensures adhesion of a circuit pattern to an insulating substrate at a component mounting position. The present invention relates to a substrate and an electronic circuit device.

  Conventionally, “semi-additive method” and “subtractive method” are generally used as a method for manufacturing a printed wiring board (for example, FPC). Among these, the “subtractive method” uses a copper-clad laminate in which a copper foil is attached to the entire surface of an insulating base material made of an insulating material (for example, polyimide), and an unnecessary portion of copper foil is removed. This is a method of removing and creating a circuit pattern. As a copper clad laminated board, there exists what laminated | stacked copper foil on the flexible thin film (CCL), and there exist single-sided CCL and double-sided CCL. This “subtractive method” is a production method that has been widely used in the production of printed wiring boards, and has a lot of results.

  On the other hand, as described in Patent Document 1, the “semi-additive method” is a thin metal layer (conductive seed layer) of several tens to several hundreds of nanometers on a surface portion of an insulating base material by a sputtering method or the like. This is a manufacturing method in which a circuit pattern is formed by applying copper plating to only necessary portions. This “semi-additive method” can create a finer circuit pattern than the “subtractive method”, for example, a fine pitch circuit having a pitch of 30 μm or less.

  This “semi-additive method” has the following steps.

(1) First, a conductive seed layer is formed on the surface portion of an insulating base made of an insulating material. This conductive seed layer is a layer for imparting electrical conductivity to the surface portion of the insulating base material, and is formed by electroless copper plating, sputtering film formation, or the like.

(2) Next, on the conductive seed layer, a resist agent is applied to form a resist layer, and exposure and development are performed to form a plating resist layer in a portion other than a portion that becomes a circuit pattern.

(3) Then, by performing electrolytic copper plating, a circuit pattern is created by attaching copper having a predetermined thickness to a portion to be a circuit pattern.

(4) Next, the plating resist layer is removed.

(5) Furthermore, the circuit pattern is completed by removing the unnecessary portion of the conductive seed layer other than the portion where the circuit pattern is created.

(6) When the circuit pattern is completed in this way, a cover layer made of an insulating material is formed on the insulating substrate. The cover layer is formed so as to cover the circuit pattern. The cover layer is formed with an opening at a component mounting position where an electronic component is mounted in the circuit pattern.

  An electronic component such as an IC chip is mounted at a component mounting position where such an opening is located. There are several methods for mounting electronic components. Generally, the terminals (bumps) of electronic components are connected to the circuit pattern by applying heat or pressure between the circuit pattern and the electronic components. By doing.

(7) Then, if necessary, an electronic circuit device is completed by attaching a reinforcing material or the like. In this electronic circuit device, when the single-sided CCL is used, the insulating base is generally exposed on the back surface on which the electronic component is not mounted.

JP 2003-309337 A

  In the printed wiring board as described above, in recent years, there is an increasing demand for circuit pattern miniaturization, and the pattern width is becoming narrower. In the future, miniaturization of circuit patterns will further advance, and the pattern widths of circuit patterns are becoming increasingly narrower. In order to miniaturize the circuit pattern, it is better to form the conductive seed layer by sputtering. However, the conductive seed layer formed by sputtering film formation has low adhesion strength to an insulating base material made of, for example, polyimide resin. In particular, the conductive seed layer mainly used in the semi-additive method has low adhesion strength to the insulating substrate after heating. For example, when heated at 180 ° C. for 2 hours, the adhesion strength decreases by about 50%. There are things to do. If the adhesion strength of the conductive seed layer to the insulating substrate is low, the adhesion strength of the completed circuit pattern to the insulating substrate will also be low. In general, products that have a copper layer formed directly on an insulating substrate by sputtering, electroless plating, etc. (metalized products) are more closely attached than those in which the copper layer and insulating substrate are bonded with an adhesive. The mosquito is weak.

  If the adhesion strength of the circuit pattern to the insulating substrate is low, heat or pressure is applied in the process after the circuit pattern is formed, that is, the terminal plating process, the electronic component mounting process, the cover layer forming process, or the like. When the chemical solution is used or when heat or pressure is applied in the use environment after completion, the circuit pattern may be peeled off from the insulating substrate. Moreover, if the circuit pattern is peeled off from the insulating base material in the mounting process of the electronic component, there is a possibility that the electronic component cannot be mounted.

  In the metallized product described above, pre-treatment such as modifying the surface of the insulating base material in advance is performed as a measure for improving the adhesion. Plasma treatment, ion gun treatment, corona treatment, and alkali treatment are used for this pretreatment. By performing these pretreatments, the chemical state of the surface of the insulating base material is changed, and the adhesion strength with the metal element is improved, or the adhesion strength is improved by the anchor effect due to the roughening of the surface of the insulating base material. It has been reported. However, when the circuit pattern is miniaturized, sufficient adhesion strength between the circuit pattern and the insulating base material has not been obtained.

  The present invention has been made in view of the above, and the purpose thereof is to ensure the adhesion strength of the circuit pattern to the insulating substrate even when the circuit pattern is miniaturized using a “semi-additive method” or the like. Prevents the circuit pattern from being peeled from the insulating substrate in the process after the circuit pattern is formed, such as the terminal plating process and the electronic component mounting process, or the circuit pattern from being peeled from the insulating substrate in the use environment after completion. Another object of the present invention is to provide a printed wiring board and an electronic circuit device using such a printed wiring board.

  In general, the adhesion strength of a circuit pattern to an insulating substrate is reduced by heating because copper (Cu) forming the circuit pattern diffuses to the insulating substrate side, and copper oxide is formed at the interface between the circuit pattern and the insulating substrate. It is said that it is formed. Therefore, in the conventional printed wiring board, the circuit pattern is obtained by using nickel (Ni), chromium (Cr), cobalt (Co) or the like as the material of the conductive seed layer between the circuit pattern and the insulating base material. Thus, the diffusion of copper is reduced, and the decrease in adhesion strength due to heating is suppressed. However, as described above, sufficient adhesion strength between the circuit pattern and the insulating base material has not been obtained.

  Therefore, the present inventors have studied to improve the adhesion strength of the circuit pattern to the insulating substrate after heating, other than the method of suppressing the diffusion of copper and the modification treatment of the polyimide resin forming the insulating substrate. did. As a result, it is effective for the present inventors to form an oxygen-preventing film in advance on the back surface of the insulating base material on which the circuit pattern is not formed before a process involving heating such as mounting of an electronic component. It came to the knowledge that it is. That is, when the element concentration analysis of the interface between the conductive seed layer and the insulating base material after heating was performed, and there was no oxygen prevention film on the back surface of the insulating base material on which the circuit pattern was not formed, heating was performed. It was found that oxygen diffuses at the interface, whereas when an oxygen prevention film is present on the back surface of the insulating substrate, oxygen does not diffuse at the interface even when heated. By forming the oxygen prevention film on the back surface of the insulating base material, it was possible to suppress a decrease in the adhesion strength of the circuit pattern to the insulating base material due to heating to about 20%.

  Therefore, the printed wiring board and the electronic circuit device according to the present invention have at least one of the following configurations.

[Configuration 1]
The printed wiring board according to the present invention includes an insulating base material made of an insulating material, a circuit pattern made of a conductive material formed on the surface of the insulating base material, and a circuit formed on the insulating base material made of the insulating material. A cover layer covering the pattern and having an opening corresponding to the mounting position of the electronic component in this circuit pattern, and formed at a position corresponding to at least the opening of the cover layer on the back surface of the insulating substrate And an oxygen prevention film.

[Configuration 2]
The printed wiring board according to the present invention is a printed wiring board having configuration 1, and the oxygen prevention film is a metal layer.

[Configuration 3]
The printed wiring board according to the present invention is a printed wiring board having Configuration 2, and the metal layer is made of a material containing at least one of chromium, cobalt, nickel, copper, platinum, or gold.

[Configuration 4]
The printed wiring board according to the present invention is a printed wiring board having any one of configurations 1 to 3, and the oxygen prevention film has a thickness of 20 nm or more.

[Configuration 5]
The printed wiring board according to the present invention is a printed wiring board having any one of configurations 1 to 4, and the oxygen prevention film is formed by a laminating method, a sputtering method, a vapor deposition method, an electroless plating method, or It is formed by any one of electrolytic plating methods or a combination thereof.

[Configuration 6]
A printed wiring board according to the present invention is a printed wiring board having any one of configurations 1 to 5, wherein the circuit pattern is formed of a conductive material on a conductive seed layer formed on a surface portion of an insulating base material. In the conductive seed layer, unnecessary portions other than the portion where the circuit pattern is formed are removed, and the conductive seed layer remains only between the circuit pattern and the insulating substrate.

[Configuration 7]
An electronic circuit device according to the present invention includes a printed wiring board having any one of Configurations 1 to 6, and an electronic component having a terminal portion connected to a circuit pattern and disposed at a mounting position.

  In the present invention, the oxygen-preventing film on the back surface of the insulating substrate is formed with a film thickness of several nm (several tens of thousands) or more by sputtering or vapor deposition after the circuit pattern is formed, or The circuit pattern may be formed only on one side of the double-sided CCL.

  In addition, when a problem arises due to the presence of the oxygen prevention film on the back surface of the insulating base material, this oxygen treatment is performed by etching or the like after the surface treatment process such as mounting of the electronic component to which heat is applied. The prevention film may be removed.

  In the printed wiring board according to the present invention, oxygen is diffused by heating at the interface between the conductive seed layer and the insulating base material by forming an oxygen prevention film on the back surface of the insulating base material on which the circuit pattern is not formed. And the adhesion strength of the circuit pattern to the insulating substrate after heating can be improved. Therefore, in this printed wiring board, even when creating a narrow-pitch circuit pattern using the “semi-additive method” or the like, the circuit pattern from the insulating base material when heated in a process such as mounting of an electronic component is removed. Peeling can be prevented. Further, in this printed wiring board, reliability can be improved even when the printed wiring board is produced as a printed wiring board used in a high temperature environment.

  The effects of the present invention are not limited to a printed wiring board in which a circuit pattern is formed on only one side of an insulating base material, and the circuit pattern is peeled even in a printed wiring board in which a circuit pattern is formed on both sides of the insulating base material. It can be obtained in the same manner by designing the circuit so that the oxygen prevention film is present on the back side of the narrow pitch portion where it is likely to occur.

  That is, the present invention ensures the adhesion strength of the circuit pattern to the insulating base material even when the circuit pattern is miniaturized using a “semi-additive method” or the like, and a terminal plating process, an electronic component mounting process, etc. A printed wiring board in which peeling of the circuit pattern from the insulating substrate in the process after forming the circuit pattern or peeling of the circuit pattern from the insulating substrate in the use environment after completion is prevented, and such printed wiring An electronic circuit device using a substrate can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In this embodiment, a printed wiring board created using the “semi-additive method” will be described.

  FIG. 1 is a cross-sectional view showing a configuration of a printed wiring board in the present embodiment.

  As shown in FIG. 1, this printed wiring board has an insulating base 1 made of an insulating material. A circuit pattern 2 is formed on the surface portion of the insulating substrate 1. The circuit pattern 2 is formed on the conductive seed layer 3 formed on the surface portion of the insulating substrate 1. That is, in this circuit pattern 2, first, a conductive seed layer 3 is formed on the surface portion of the insulating substrate 1, and a resist agent is applied to the conductive seed layer 3 to form a resist layer. Development is performed to form a plating resist layer on a portion other than the portion to be a circuit pattern, and then electrolytic copper plating is performed to attach copper having a predetermined thickness to a predetermined portion on the conductive seed layer 3 Has been created.

  The conductive seed layer 3 is a layer for imparting electrical conductivity to the surface portion of the insulating substrate 1, and is formed by electroless copper plating, vapor deposition, or sputtering film formation. Then, the unnecessary portion of the conductive seed layer 3 other than the portion where the circuit pattern 2 is formed is removed after the plating resist layer is removed. That is, in this printed wiring board, the conductive seed layer 3 remains between the circuit pattern 2 and the insulating base material 1 only in the portion where the circuit pattern 2 is formed.

  A cover layer 4 made of an insulating material is formed on the insulating substrate 1. The cover layer 4 is formed so as to cover the circuit pattern 2. The cover layer 4 is formed with an opening 6 at a component mounting position 5 where the electronic component 101 is mounted. An electronic component 101 such as an IC chip is mounted at the component mounting position 5 where the opening 6 is located. The thickness of the cover layer 4 is a thickness that does not contact the mounted electronic component 101 so as not to hinder mounting of the electronic component 101, that is, is thinner than the protruding amount of the terminal portion (bump) 102 of the electronic component 101. Has been made.

  And in this printed wiring board, the oxygen prevention film 7 is formed in the location corresponding to the opening part 6 of the cover layer 4 in the back surface part of the insulating base material 1 at least. As the oxygen prevention film 7, a metal layer is preferable, and at least one of chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), platinum (Pt), or gold (Au) is used. It is preferable that it is formed from the material which contains. The metal layer is more preferably made of a metal on which a passive film is formed, and is preferably made of a material containing chromium (Cr), nickel (Ni), and copper (Cu). The thickness of the oxygen prevention film 7 is preferably at least 5 nm (50 Å) or more, and more preferably 20 nm (200 Å) or more.

  The oxygen prevention film 7 can be satisfactorily formed by any of a laminating method, a sputtering method, a vapor deposition method, an electroless plating method, or an electrolytic plating method. The oxygen prevention film 7 is formed after the circuit pattern 2 is formed. Note that only the copper foil on one side of the double-sided CCL may be formed as the circuit pattern 2, and the copper foil on the other side may be formed as the oxygen prevention film 7.

  The oxygen prevention film 7 may be removed by an etching process or the like after the step of heating the insulating base material 1.

  FIG. 2 is a cross-sectional view showing a configuration of a printed wiring board according to another embodiment.

  Furthermore, when this printed wiring board is configured as a printed wiring board in which the circuit pattern 2 is formed on both surfaces of the insulating base material 1, as shown in FIG. In addition, by designing the circuit so that the metal layer serving as the oxygen prevention film exists on the back side of the narrow pitch portion, the same effect as the case where the oxygen prevention film 7 is formed as described above can be obtained. Further, when a problem arises due to the presence of the oxygen prevention film 7 on the back surface of the insulating base material 1, this oxygen treatment is performed by etching or the like after the process of applying heat such as mounting of the electronic component 101 is completed. At least a part of the prevention film 7 may be removed.

  In this printed circuit board, at the component mounting position 5, as shown in FIGS. 1 and 2, the terminal portion (bump) 102 of the electronic component 101 is a bump connection position that is a terminal connection portion with respect to the circuit pattern 2. 2b is connected by ACF connection or the like. In this way, the electronic circuit device is configured by mounting the electronic component 101 on the printed wiring board.

  Examples of the printed wiring board according to the present invention will be given below.

[Example 1]
In Example 1, “Kapton EN” (trade name: manufactured by Toray DuPont), which is a polyimide film, was used as the insulating substrate 1 in the embodiment shown in FIG. The insulating substrate 1 was set in a sputtering chamber, and argon was used as a plasma gas, and a conductive seed layer 3 was formed on the surface portion of the insulating substrate 1 by sputtering under a vacuum of 7 × 10 ⁻³ Torr. . The conductive seed layer 3 is composed of a nickel-chrome layer (film thickness 10 nm (100 mm)) and a copper layer (film thickness 200 nm (2000 mm)).

  Next, “dry film resist” (trade name: manufactured by Hitachi Chemical Co., Ltd.) was laminated as a resist agent on the conductive seed layer 3 formed on the insulating base material 1 to obtain a resist layer. A circuit design drawing is exposed and developed with respect to this resist layer, so that a portion of the resist layer where the circuit pattern 2 is formed is removed, and only a non-formation portion of the circuit pattern 2 is covered with the plating resist layer It was. Then, copper was deposited on the portion of the conductive seed layer 3 where the resist layer was removed by electrolytic copper plating to form the circuit pattern 2. In the electrolytic copper plating, the following copper sulfate plating bath is used, and electricity is passed through the conductive seed layer 3 on the insulating base material 1 immersed in the copper sulfate plating bath so that it is covered with the plating resist layer. Copper was deposited on the missing part.

[Copper sulfate plating bath]
Copper sulfate pentahydrate ... 75g / L
Sulfuric acid ... 190g / L
Chlorine ion ... 50mg / L
Capre Grime "CLX-A" (trade name: manufactured by Meltex) ··· 5mL / L
Capre Grime "CLX-C" (trade name: manufactured by Meltex) ··· 5mL / L
Next, the plating resist layer was removed using a 3% aqueous sodium hydroxide solution. Further, the conductive seed layer 3 in the non-formed part of the circuit pattern 2 was removed by etching using an etching solution such as iron chloride solution or copper chloride solution. In this way, a circuit pattern 2 having a line width of 5 mm was formed.

  After the circuit pattern 2 was formed, a copper (Cu) layer 7 having a film thickness of 20 nm (200 mm) was formed on the back surface portion of the insulating base material 1 on which the circuit pattern was not formed by a sputtering method. And the cover layer 4 was formed using the photo solder resist agent which is an insulating material. The cover layer 4 is formed on the insulating substrate 1 so as to cover the circuit pattern 2 and has an opening 6 at the component mounting position 5 where the electronic component 101 is mounted. Note that the thickness of the cover layer 4 formed in this way is a thickness that does not contact the electronic component 101 when the electronic component 101 is mounted at the component mounting position 5 (that is, the terminal portion (bump) 102 of the electronic component 101). The thickness is smaller than the protrusion amount of

[Example 2]
A printed wiring board was prepared in the same manner as in Example 1 except that the thickness of the copper layer 7 on the back surface of the insulating base 1 was changed. That is, the printed wiring board which formed the copper layer 7 with a film thickness of 5 nm (50?), 10nm (100?), 100nm (1000?) And 500nm (5000?) By the sputtering method was created.

Example 3
A printed wiring board was prepared in the same manner as in Example 1 except that the method and material for forming the oxygen prevention film 7 on the back surface of the insulating base material 1 were changed. That is, a printed wiring board on which a chromium (Cr) layer, a cobalt (Co) layer, a nickel (Ni) layer, a platinum (Pt) layer, and a gold (Au) layer having a film thickness of 20 nm (200 mm) are formed by vapor deposition. Each was created.

[Comparative Example 1]
A printed wiring board was prepared in the same manner as in Example 1 except that the oxygen-preventing film 7 was not formed on the back surface of the insulating base material 1 and the rest was not formed.

[Contrast between Example 1 to Example 3 and Comparative Example 1]
About the printed wiring board in Example 1 thru | or Example 3 and the comparative example 1 which were produced as mentioned above, the normal state of a circuit pattern and heating (180 degrees) using a tensile testing machine ("TG * 200N" by NMB). The tensile strength (peel strength) after 2 hours at C) was measured. The measurement results are shown in [Table 1] below.

  From this [Table 1], in order for the circuit pattern to maintain sufficient tensile strength after heating, the material forming the oxygen-preventing film 7 on the back surface of the insulating substrate 1 is not only copper but also chromium, cobalt, nickel It can be understood that any of platinum and gold may be used, and the thickness of the oxygen prevention film is preferably 20 nm or more.

  FIG. 3 is a side view showing the procedure for measuring the element concentration ratio on the surface of the conductive seed layer 3 that is in contact with the insulating substrate 1.

  In this printed wiring board, as shown in FIG. 3, the circuit pattern 2 and the conductive seed layer 3 are peeled from the insulating base material 1, and the element concentration on the surface of the conductive seed layer 3 that is in contact with the insulating base material 1 The ratio was measured using X-ray. This measurement was performed for the above-described Examples and Comparative Examples.

  FIG. 4 is a graph showing the abundance of oxygen on the surface of the conductive seed layer 3 that is in contact with the insulating substrate 1.

  In the example in which the oxygen prevention film 7 is formed on the back surface of the insulating base material 1, as shown in FIG. 4, the conductive seed layer 3 can be obtained even if heating at 180 ° C. is continued for 10 hours or more. The abundance of oxygen (element concentration ratio) does not increase on the surface in contact with the insulating substrate 1. On the other hand, in the comparative example in which the oxygen prevention film 7 is not formed on the back surface portion of the insulating base material 1, as shown in FIG. 4, when heating at 180 ° C. is continued, the insulating group of the conductive seed layer 3 The abundance of oxygen (element concentration ratio) on the surface in contact with the material 1 increases to 16% in 2 hours and close to 30% in 10 hours.

It is sectional drawing which shows the structure of the printed wiring board which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the printed wiring board in other embodiment of this invention. It is a side view which shows the procedure which measures the element concentration ratio in the surface which was in contact with the insulating base material of the electroconductive seed layer. It is a graph which shows the abundance of oxygen in the surface which was in contact with the insulating base material of the electroconductive seed layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation base material 2 Circuit pattern 3 Conductive seed layer 4, 4a Cover layer 5 Component mounting position 6 Opening 7 Oxygen prevention film

Claims (7)

An insulating substrate made of an insulating material;
A circuit pattern made of a conductive material formed on the surface of the insulating substrate;
A cover layer made of an insulating material and formed on the insulating base material to cover the circuit pattern, and having an opening corresponding to the mounting position of the electronic component in the circuit pattern;
A printed wiring board comprising: an oxygen-preventing film formed on at least a portion of the back surface of the insulating base material corresponding to the opening of the cover layer. The printed wiring board according to claim 1, wherein the oxygen prevention film is a metal layer. The printed wiring board according to claim 2, wherein the metal layer is made of a material containing at least one of chromium, cobalt, nickel, copper, platinum, or gold. The printed wiring board according to any one of claims 1 to 3, wherein the oxygen prevention film has a thickness of 20 nm or more. The oxygen prevention film is formed by any one of a laminating method, a sputtering method, a vapor deposition method, an electroless plating method, an electroplating method, or a combination thereof. The printed wiring board as described in any one of Claim 1 thru | or 4. The circuit pattern is created by attaching a conductive material on a conductive seed layer formed on the surface portion of the insulating substrate,
The conductive seed layer is formed by removing unnecessary portions other than the portion where the circuit pattern is formed, and remaining only between the circuit pattern and the insulating base material. Item 6. The printed wiring board according to any one of Items 5. A printed wiring board according to any one of claims 1 to 6,
An electronic circuit device comprising: a terminal portion connected to the circuit pattern; and an electronic component disposed at the mounting position.

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