JP4452650B2 - Wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a wiring board composed of a rigid part and a flexible part, and a manufacturing method thereof.

There is a wiring board that includes a flexible portion having flexibility and a rigid portion that is continuous with the flexible portion and serves as a mounting portion for electronic components. Since the wiring board can be bent and deformed at the flexible portion, there is an advantage that the degree of freedom in selecting the arrangement position in the apparatus is increased and it is possible to contribute to downsizing of the entire apparatus.
FIG. 5 shows a general wiring board composed of a flexible portion 82 and a rigid portion 81. The rigid portion 81 is formed by sandwiching a flexible substrate 83 between rigid substrates 86 and 87, and the flexible portion 82 is composed of only the flexible substrate 83. The flex substrate 83 has a wiring pattern 84 formed on the surface of an insulating resin layer 91 such as a flexible polyimide resin.

Each of the rigid substrates 86 and 87 is configured by forming a wiring pattern 89 on a hard insulating resin layer 88. As the hard insulating resin layer 88, for example, a glass cloth impregnated with an epoxy resin is used. The rigid substrates 86 and 87 are fixed to the flexible substrate 83 via the adhesive layer or the adhesive layer and the film 85 so as to sandwich the flexible substrate 83 from both sides.
As a wiring board having such a configuration, for example, there is one described in Patent Document 1.

JP-A-7-307572

  In the wiring board 80 having the above-described configuration, since the flexible insulating resin layer 91 and the hard insulating resin layer 88 are formed of different materials, the adhesive strength between the different material layers may be insufficient, or different materials may be used. There is a problem that the manufacturing process becomes complicated by using.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a reliable wiring board by a simple manufacturing method.

The present invention has the following configuration in order to achieve the above object.
That is, the present invention includes a flexible portion and a rigid portion provided continuously to the flexible portion, the flexible portion is made of a flexible substrate on which a wiring pattern is laminated through an insulating resin layer, The rigid portion is formed of the flexible substrate integrally formed with the flexible portion, and a wiring density of the wiring pattern formed on the flexible substrate is set larger than a wiring density of the wiring pattern of the flexible portion . In the wiring board, the insulating resin layer has a low elasticity with a Young's modulus of 25 MPa or less, the insulating resin layer of the flexible portion and the wiring pattern are extended to the rigid portion, and the wiring pattern is Since the rigid part is partially formed in a solid pattern, the rigid part is the flexible part. Wherein the remote hardness is formed higher.

Further, the rigid part is formed of the flexible substrate formed integrally with the flexible part, and the number of wiring patterns stacked is set larger than that of the flexible part.

Further, the rigid portion is formed with a multilayer wiring structure using an insulating resin layer made of the same material as the insulating resin layer on one side or both sides of the flexible substrate. To do.
According to this, a reliable and higher-performance wiring board can be provided.
The insulating resin layer is characterized in that a conductor layer can be formed on the surface by electroless plating or a combination of electroless plating and electrolytic plating.
The insulating resin layer is made of a thermosetting epoxy resin film or a thermosetting phenol novolac resin film.

The method for manufacturing the wiring board includes a step of sequentially laminating an insulating resin layer and a wiring pattern on a metal support plate, and forming the uppermost wiring pattern, and then forming the uppermost wiring pattern and the uppermost wiring pattern. The method includes a step of covering the insulating resin layer with a protective film, and a step of peeling the protective film after removing the support plate by etching.
According to this, a wiring board can be manufactured efficiently.

  According to the present invention, a reliable wiring board can be obtained by a simple manufacturing method.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
The wiring board of the present embodiment is formed using a resin film having a function described below as the insulating resin layer.
The resin film is cured by heating at a temperature of 80 to 180 ° C. When the heating temperature is 80 to 180 ° C., the heating time is preferably 30 to 180 minutes. The heat-cured resin film (cured resin product) has flexibility and can be bent. Further, the cured resin is characterized by low elasticity. Specifically, the Young's modulus of the cured resin is 25 MPa or less.
Moreover, a conductor layer can be formed on the surface of the cured resin by plating. As a method for forming a conductor layer by plating, a method of forming a conductor layer composed of an electroless plating layer by electroless plating, and an electroplating layer is laminated on the electroless plating layer by combining electroless plating and electrolytic plating. There is a method in which a conductive layer is used.

As electroless plating, for example, there is electroless copper plating, and a general method can be used. That is, the electroless plating is a method of performing a pretreatment for precipitating the catalytic metal on the surface of the cured resin and then immersing it in a predetermined electroless plating solution. The pretreatment includes a roughening process, a catalyst process, and an accelerator process.
The roughening step is a step of roughening the surface of the cured resin by chemical etching or the like, and the catalyst step is a compound containing a catalyst metal as a core of electroless plating, such as a Pd complex, In this step, a Pd—Sn complex or an organic palladium colloid is adsorbed on the surface of the roughened resin film. The accelerator step is a step of reducing the catalytic metal component of the adsorbed compound and depositing a catalytic metal such as Pd on the surface of the cured resin. Before the roughening step, a degreasing treatment step for removing dirt such as oils and fats adhering to the surface of the cured resin is performed as necessary.
As a method of forming an electrolytic plating layer on an electroless plating layer by electroless plating, a general electrolytic plating method can be used. For example, there is electrolytic copper plating as the electrolytic plating, and a copper sulfate plating bath can be used as the plating bath.

As a method for forming a wiring pattern using the conductor layer on the cured resin, any of a subtractive method, a semi-additive method, and an additive method can be used.
In the additive method, a wiring pattern can be formed by forming a resist as a plating mask on the surface of the cured resin, forming a conductor layer only by electroless plating, and then removing the resist.
In the case of the semi-additive method, an electroplating layer is formed by providing a resist as a plating mask on the electroless plating layer provided on the surface of the cured resin. Next, the resist is removed, and the electroless plating layer exposed on the outer surface is removed by etching, whereby a wiring pattern can be formed.
In the case of the subtractive method, an electrolytic plating layer is laminated on an electroless plating layer provided on a cured resin, and a resist is further formed thereon. Then, after performing an etching process using the resist as a mask, the resist is removed to form a wiring pattern.

Furthermore, the resin cured product can be drilled with a laser.
Moreover, a resin film can be easily bonded by attaching a resin film on a metal plate, a resin film or a cured resin, heating at the above temperature, and thermosetting.
That is, the resin film can be suitably used as an insulating resin layer in a build-up method in which an insulating resin layer and a wiring pattern are sequentially laminated to form a multilayer wiring structure.
Examples of the resin film having such a function include an epoxy resin film or a phenol novolac resin film, and more specifically, an epoxy non-photosensitive resin film and a phenol novolac non-photosensitive resin film.

FIG. 4C is a cross-sectional view of a wiring board made of the resin film.
The wiring board 10 is composed of a flexible portion 14 and a rigid portion 15 that is continuous with the electronic portion such as a semiconductor element. The flexible portion 14 has flexibility and can be bent, whereas the rigid portion 15 has a higher hardness than the flexible portion 14 and is formed to be hard that cannot be easily bent. Thereby, an electronic component can be mounted on the rigid portion 15 in a stable state.
In the wiring board 10 shown in FIG. 4C, a predetermined portion of the flexible substrate 16 is a rigid portion 15, and the remaining portion is a flexible portion 14.

The flexible substrate 16 has a multilayer wiring structure in which an insulating resin layer made of a thermoset of the resin film is laminated. That is, the flexible substrate 16 is configured such that wiring patterns are stacked via an insulating resin layer, and each wiring pattern is electrically connected by a via formed through the insulating resin layer.
In the flexible substrate 16 shown in FIG. 4C, the first, second and third insulating resin layers 12a, 12b and 12c are laminated, and the upper surfaces of the first and second insulating resin layers 12a and 12b are formed. First and second wiring patterns 13a and 13b are respectively formed. And the 3rd wiring pattern 13c is formed only in the upper surface of the 3rd insulating resin layer 12c of the site | part used as the rigid part 15. FIG.
Further, the first wiring pattern 13a and the second wiring pattern 13b are electrically connected by a first via 17a penetrating the second insulating resin layer 12b. Similarly, the second wiring pattern 13b and the third wiring pattern 13c are electrically connected by a second via 17b penetrating the third insulating resin layer 12c.

  Also, the solder resist layer 18 is formed so as to cover only the upper surface (including the third wiring pattern 13c) of the portion that becomes the rigid portion 15 of the third insulating resin layer 12c. In the solder resist layer 18, an opening 19 is formed at a position corresponding to the pad portion of the third wiring pattern 13c, and a solder bump is formed as an external connection terminal on the pad portion exposed through the opening 19. ing. In order to improve the adhesiveness between the solder bump and the pad portion, a conductive film 21 such as Ni / Au may be provided on the pad portion, and the solder bump may be joined via the conductive film 21. Electronic components (not shown) such as semiconductor elements are flip-chip connected to the wiring substrate 10 via solder bumps. Furthermore, an underfill resin may be filled between the electronic component and the wiring board 10.

If the number of insulating resin layers 12 to be laminated is too large, the flexible substrate 16 loses its bendable property. Therefore, the insulating resin layer is laminated to such a thickness that the bendable property is not lost. The For example, the total thickness of the laminated insulating resin layers may be less than 200 μm, and in FIG. 4C, three insulating resin layers having a thickness of 50 μm are laminated to a total thickness of 150 μm. ing.
In addition, the portion of the flexible substrate 16 that becomes the flexible portion 14 is formed with a wiring density such that the wiring patterns 13a and 13b do not hinder the bendable property of the insulating resin layer.

And the following structure is added to the part used as the rigid part 15 of the flexible substrate 16 so that it may have sufficient hardness which can mount an electronic component in the stable state.
One is a configuration in which one or more wiring patterns are provided in the portion of the rigid portion 15 rather than the portion of the flexible portion 14. A rigid wiring pattern made of metal can increase the hardness of the portion to form the rigid portion 15.
In the wiring substrate 10 of FIG. 4C, the third wiring pattern 13c is formed only on the portion that becomes the rigid portion 15 on the third insulating resin layer 12c that is the outermost layer. In this way, the rigid portion 15 can be formed hard with respect to the flexible portion 14 that can be bent. Incidentally, each wiring pattern 13a, 13b, 13c is formed in substantially the same thickness.

Further, the rigid portion 15 is also configured by setting so that the wiring density of the wiring pattern of one layer or two or more layers in the portion that becomes the rigid portion 15 is larger than the wiring density of each wiring pattern in the portion that becomes the flexible portion 14. Can be made hard.
For example, a single-layer wiring pattern of the flexible substrate 16 is configured to be partially formed in a solid pattern at a portion that becomes the rigid portion 15.
The wiring board 10a shown in FIG. 7 has basically the same configuration as that of the wiring board 10 of FIG. 4C, but the second wiring pattern 13b is formed in a solid pattern at a portion 130b where the rigid portion 15 is formed. Is formed. The solid pattern wiring pattern can be used as a wiring pattern for a power supply. Incidentally, the solid pattern-like wiring pattern is formed only on the rigid portion 15 and is not formed on the flexible portion 14.

Next, a method for manufacturing the wiring board 10 shown in FIG. 4C will be described.
First, a copper plate is prepared as a support plate 11 made of metal (see FIG. 1A), a resin film is pasted on the support plate 11, and the first insulating resin layer 12a is applied on the support plate 11 by curing. (See FIG. 1B). The support plate 11 is used to support a low-elasticity resin film and maintain its posture when the wiring board 10 is manufactured.
The curing is performed at a temperature of 80 to 180 ° C. by heating for 30 to 180 minutes. A material that has a Young's modulus of 25 MPa or less and is flexible and bendable even after thermosetting by curing.
Thereafter, a first wiring pattern 13a is formed on the first insulating resin layer 12a (see FIG. 1C).

The method of forming the first wiring pattern 13a may be any of the above-described subtractive method, semi-additive method, and additive method. However, the semi-additive method is advantageous in that a high-definition wiring pattern can be efficiently formed. is there.
A method for forming a wiring pattern by the semi-additive method will be described. First, the pretreatment of the above-described electroless copper plating is performed on the first insulating resin layer 12a to deposit Pd as a catalyst metal. Then, the first insulating resin layer 12a is immersed in the electroless copper plating solution together with the support plate 11 to form an electroless copper plating layer on the first insulating resin layer 12a. Then, a resist layer as a plating mask is formed on the electroless copper plating layer, and electrolytic copper plating is performed. The resist layer can be formed in a predetermined pattern by providing a film-like or liquid photosensitive resist on the electroless copper plating layer, and exposing and developing it. Further, the electrolytic copper plating can be performed by immersing the support plate 11 on which the resist layer is formed in a copper sulfate plating bath, which is a plating bath for electrolytic copper plating, whereby electrolysis is performed on the electroless copper plating layer. A copper plating layer is formed. Thereafter, the resist layer is removed and copper etching is performed to remove the exposed electroless copper plating layer other than the portion where the wiring pattern 13a is to be formed, thereby forming a wiring pattern 13a made of a copper layer (FIG. 1). (C)).

Subsequently, the resin film is pasted on the first insulating resin layer 12a on which the first wiring pattern 13a is formed, and the whole is pressed and flattened, and then cured. The curing is performed by the same method as the curing. Thereby, the 2nd insulating resin layer 12b which consists of a resin film is formed (FIG.1 (d)).
Next, a via hole 20a penetrating the second insulating resin layer 12b is provided so that the first wiring pattern 13a is exposed at a predetermined position of the second insulating resin layer 12b (FIG. 2A). FIG. 2 (b)). The via hole 20a can be formed by removing a predetermined portion of the second insulating resin layer 12b with a laser.
Thereafter, the second wiring pattern 13b and the first via 17a are formed by a method similar to the method of forming the first wiring pattern 13a. That is, electroless copper plating is performed on the entire upper surface of the second insulating resin layer 12b including the inside of the via hole 20a to form an electroless copper plating layer. Then, a resist layer having a predetermined pattern is formed on the electroless copper plating layer, and electrolytic copper plating is performed using the resist layer as a plating mask. The resist layer can be formed by the same method as described above. As a result, the via hole 20a is filled with copper, and an electrolytic copper plating layer having a second wiring pattern shape is formed. Thereafter, the resist layer is removed and copper etching is performed to remove the exposed electroless copper plating layer other than the portion where the second wiring pattern 13b is to be formed. 1 via 17a is formed (FIG. 2C).

Thereafter, a third insulating resin layer 12c is formed on the second insulating resin layer 12b by the same method as described above (FIG. 2D).
Next, the second penetrating through the third insulating resin layer 12c with a laser so that the second wiring pattern 13b is exposed at a predetermined position of the third insulating resin layer 12c in the portion to become the rigid portion 15. Via hole 20b is provided (FIG. 3A).
Thereafter, the third wiring pattern 13c and the second via 17b are formed by the same method as the method for forming the second wiring pattern 13b and the first via 17a. The third wiring pattern 13c is formed only on a portion that becomes the rigid portion 15 on the upper surface of the third insulating resin layer 12c (FIG. 3B).
Then, the solder resist layer 18 having the opening 19 formed at a position corresponding to the pad portion of the third wiring pattern 13c is replaced with the third wiring pattern 13c and the rigid portion 15 of the third insulating resin layer 12c. It forms so that the site | part which becomes (FIG.3 (c)).
Next, a dry film 22 as a protective film is attached so as to cover the solder resist layer 18, the third wiring pattern 13c, and the third insulating resin layer 12c (FIG. 3D), and the support plate is etched. 11 is removed (FIG. 4A). The dry film 22 protects the solder resist layer 18, the third wiring pattern 13c, and the third insulating resin layer 12c from the etchant, and is removed after the etching (FIG. 4B).

Then, a conductive film 21 such as Ni / Au is formed by plating on the pad portion of the third wiring pattern 13 c exposed through the opening 19 (FIG. 4C), and solder is further formed on the conductive film 21. The bumps are reflowed and joined to form external connection terminals.
Of the wiring board of this embodiment, the flexible portion 14 is formed in a state having flexibility by a build-up method in which the insulating resin layer 12 and the wiring pattern 13 are sequentially laminated to form a multilayer wiring structure.

In this embodiment, the following effects can be obtained.
Since the above-mentioned wiring board does not require a conventional rigid board, there is no insufficient strength due to poor adhesion of the rigid board to the flexible board, poor electrical connection, etc., and the wiring board is reliable.
Moreover, as for the conventional wiring board, the flexible part consists of a polyimide resin film, and formed the conductor layer by bonding copper foil on the polyimide resin film with the adhesive agent. In this case, a through hole must be formed in order to electrically connect the wiring patterns, and the through hole is formed by first making a hole in the copper foil by etching and then making a hole in the insulating layer by a laser. It was a complicated process. Furthermore, in order to form a wiring pattern from a conductor layer made of copper foil, a subtractive method must be used, and there is a problem that a high-definition wiring pattern cannot be formed.
On the other hand, in the above embodiment, since the conductor layer can be formed by plating on the insulating resin layer, it is not necessary to adhere the copper foil, and the wiring pattern can be formed by the additive method or the semi-additive method. A fine wiring pattern can be formed. As a result, the wiring board becomes more advantageous for high functionality and miniaturization. In addition, since a via hole can be formed in the insulating resin layer by a laser, it is easy to form a via that electrically connects the wiring patterns.
In addition, by using a support plate during manufacturing, it is possible to form a favorable wiring pattern while maintaining the posture of the low-elasticity resin film.

As described above, the present invention has been variously described with reference to preferred embodiments. However, the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. is there.
In the above-described embodiment, a solid pattern is formed in a portion that becomes the rigid portion 15 in order to form the rigid rigid portion 15, or a wiring pattern is provided in the outermost layer. However, the present invention is not limited to this method. . For example, by forming a multilayer wiring structure using an insulating resin layer made of the same material as the insulating resin layer on one surface side or both surface sides of the portion to be the rigid portion 15 of the flexible substrate, It is good also as the rigid part 15 by raising the hardness of a site | part. By forming a multilayer wiring structure in which an insulating resin layer and a wiring pattern are partially laminated on the outside of the flexible substrate 16, the hardness of the part can be increased. According to this, since the insulating resin layers made of the same material are easily bonded and have high bonding strength, a reliable wiring board can be provided.

Specifically, there is a structure as shown in FIG.
As with the flexible substrate 16, the flexible substrate 23 is formed by laminating first to third insulating resin layers 12a, 12b, and 12c, and the first wiring pattern 13a and the second wiring pattern 13b are the first. It is electrically connected via the via 17a. The 3rd wiring pattern 13c is formed only in the site | part used as the rigid part 15, and the flexible substrate 23 can be bent freely in this state.
And the 4th insulating resin layer 12d is formed only in the outer side of the site | part used as the rigid part 15 of the flexible substrate 23, and the 4th wiring pattern 13d is formed on it. The fourth insulating resin layer 12d is made of a thermoset of the resin film. The third wiring pattern 13c and the fourth wiring pattern 13d are electrically connected by the third via 17c. A solder resist layer 18 is formed so as to cover the fourth insulating resin layer 12d and the fourth wiring pattern 13d. An opening 19 is formed in the solder resist layer 18 at a position corresponding to the pad portion of the fourth wiring pattern 13d, a Ni / Au conductor film 21 is formed on the pad portion, and further on the conductor film 21. The configuration in which the solder bump is provided and the semiconductor element is flip-chip connected is the same as described above.

In the forming method of FIG. 6, after the flexible substrate 23 is formed by the same method as described above, the resin film is thermoset by the same method to form the fourth insulating resin layer 12d, and the semi-additive method is used. 3 vias 17c and a fourth wiring pattern 13d are formed. Thereafter, a solder resist layer 18, a conductor film 21, solder bumps and the like are formed. That is, following the formation of the flexible substrate 23, the rigid portion 15 can be formed rigidly by providing a multilayer wiring structure at a site that becomes the rigid portion 15 by a build-up method.
Note that the number of insulating resin layers and wiring patterns provided in the flexible portion 14 and the rigid portion 15 is not limited to this.

  Further, as in the wiring board 10c shown in FIG. 8, multilayer wiring structures 24 and 25 may be provided on both the upper and lower surfaces so as to sandwich the flexible board 23 to form the rigid portion 15. Also at this time, the multilayer wiring structures 24 and 25 provided above and below can be formed using the build-up method following the formation of the flexible substrate 23. In this case, an electronic component such as a semiconductor element may be mounted on both sides of the rigid portion 15 by providing solder resist layers 18, conductor films 21, solder bumps, and the like on both sides of the rigid portion 15.

It is process drawing which shows the manufacturing method of a wiring board. It is process drawing which shows the manufacturing method of a wiring board. It is process drawing which shows the manufacturing method of a wiring board. It is process drawing which shows the manufacturing method of a wiring board. It is sectional drawing which shows the structure of the conventional wiring board. It is sectional drawing which shows other embodiment of a wiring board. It is sectional drawing which shows other embodiment of a wiring board. It is sectional drawing which shows other embodiment of a wiring board.

Explanation of symbols

10 Wiring board 11 Support plate
12 Insulating Resin Layer 13 Wiring Pattern 14 Flexible Part 15 Rigid Part 16 Flexible Substrate 17 Via 18 Solder Resist Layer 22 Dry Film

Claims (6)

A flexible portion and a rigid portion provided continuously to the flexible portion ;
The flexible part is composed of a flexible substrate in which wiring patterns are laminated via an insulating resin layer,
The rigid portion is formed of the flexible substrate integrally formed with the flexible portion, and a wiring density of the wiring pattern formed on the flexible substrate is set larger than a wiring density of the wiring pattern of the flexible portion . A wiring board,
The insulating resin layer has a low elasticity with a Young's modulus of 25 MPa or less,
The insulating resin layer and the wiring pattern of the flexible portion are extended to the rigid portion, and the wiring pattern is partially formed in the rigid portion so that the rigid portion is the flexible portion. A wiring board having a higher hardness than that of the wiring board. The wiring board according to claim 1, wherein the rigid portion includes the flexible substrate integrally formed with the flexible portion, and the number of wiring patterns stacked is set larger than that of the flexible portion. The rigid part is on one side or both side of the flexible substrate is characterized in that a multilayer wiring structure using an insulating resin layer made of the same material as the insulating resin layer is formed according Item 3. The wiring board according to Item 2 . 4. The wiring according to claim 1 , wherein a conductive layer can be formed on the surface of the insulating resin layer by electroless plating or a combination of electroless plating and electrolytic plating. 5. substrate. The wiring board according to claim 1 , wherein the insulating resin layer is made of a thermosetting epoxy resin film or a thermosetting phenol novolac resin film. It is a manufacturing method of the wiring board according to any one of claims 1 to 5 ,
A step of sequentially laminating an insulating resin layer and a wiring pattern on a metal support plate;
After forming the uppermost wiring pattern, covering the wiring pattern and the uppermost insulating resin layer with a protective film;
And a step of removing the protective film after removing the support plate by etching.

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