JP3490309B2 - Wiring board and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board having a structure in which a wiring pattern surface is covered with insulation, and a method for manufacturing the wiring board.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices, there is a demand for downsizing or high-density wiring of a wiring board for forming a circuit. In response to such a demand, a wiring board has been developed in which an essential configuration is enlarged and shown in cross section in FIG. In FIG. 4, 1 is 25 μ thick
A polyimide resin film (insulating support) with an adhesive of about m 2 is a wiring pattern formed on the main surface of the polyimide resin film 1, and 3 is a required area of the wiring pattern 2.
Thickness that exposes 2a and covers the wiring pattern 2 formation surface
A polyimide resin film (cover film) with an adhesive of about 25 μm, 4 is a through-hole connecting portion. In addition, 5
Each of a and 5b is an adhesive layer, and the exposed area 2a of the wiring pattern 2 is an electrical connection portion with an electronic component or another circuit wiring.

The wiring board having the structure shown in FIG. 4 is manufactured as follows. Ie thickness
A copper foil sticking sheet is prepared by sticking a copper foil having a thickness of about 12 to 18 μm to the main surface of the polyimide resin film 1 having a thickness of about 25 μm via the adhesive layer 5a. Then, a perforation process is performed on a predetermined area of this copper foil-clad sheet to form a through hole for interlayer connection, and then a conductor layer is formed on the inner wall surface of the perforation of the copper foil.
You. Then, photo-etching treatment is performed to form the wiring pattern 2, and the polyimide resin film 1 with the wiring pattern 2 in which the wiring patterns 2 on both surfaces are connected to each other is obtained.

On the other hand, a polyimide resin film (cover film) 3 having a thickness of about 12 μm with an adhesive layer having a thickness of about 15 μm prepared by punching and pressing in a required area is prepared. After that, the polyimide resin film (cover film) 3 is aligned, laminated, and arranged on the wiring patterning 2 surface of the polyimide resin film 1 and pressure-bonded and integrated on the wiring patterning 2 surface.

[0005]

However, in the case of the above wiring board, there are advantages such as compactness and flexibility, but on the other hand, there are the following disadvantages. That is, (a) polyimide resin film (insulating support) 1 and wiring pattern 2
Adhesive layers 5a and 5b are respectively interposed in order to join / integrate with (such as copper foil) and (b) join / integrate the cover film 3 on the surface on which the wiring pattern 2 is formed. . Incidentally, the adhesive layers 5a and 5b are generally required to have flame retardancy, and in response to this requirement, for example, a flame retardant such as a halogen compound or a phosphorus compound is added / blended. There is.

Here, the adhesive layer 5a containing a flame retardant,
The presence / absence of 5b not only adversely affects the electrical characteristics of the configured wiring board itself, but also the flame retardant is environmentally friendly in the manufacturing process of the wiring board or in the disposal of the wiring board. It may pose a problem.

The present invention has been made in consideration of the above circumstances and has high practicability by omitting the constitution of joining and unifying with an adhesive, reduces environmental problems, and has electric characteristics more than conventional substrates. In particular, it is an object of the present invention to provide a wiring board that can transmit a high-speed signal without deteriorating and a manufacturing method thereof.

[0008]

The invention according to claim 1 is the first
A core wiring board having an insulating layer made of the liquid crystal polymer and a wiring pattern formed on at least one main surface of the insulating layer ; and a melting point lower than the first liquid crystal polymer.
Consists of two liquid crystal polymers, said wiring pattern of the core wiring board is integrated in the formed surface, and includes a insulation coating layer that have a perforation for exposing the desired portions of the wiring pattern The wiring board is characterized in that

[0009] In the wiring board according to claim 1, the core wiring board may be a multilayer wiring pattern type. Core distribution
Due to the multilayer wiring pattern type of the wire board, the liquid crystal polymer has
Moisture resistance, high electrical insulation and high-speed signals
Highly functional wiring while making the most of transmission stability
A circuit can be provided.

Further , in the wiring board according to the first aspect , the wiring pattern layers of the core wiring board may be joined by a conductive bump having an insulating layer inserted therethrough . Of core wiring board
The connection between the wiring pattern layers is conductive with the insulation layer inserted.
Fine and highly reliable because it is made of bumps
A wired circuit with connections can be provided.

[0011]

Further, in the wiring board according to claim 1 , the wiring pattern of the core wiring board may be made of copper foil.
Can . If the wiring pattern of the core wiring board is made of copper foil,
We can provide a wiring circuit that is easy to measure and has good circuit characteristics.
It

Further, in the wiring board according to claim 1 , the wiring pattern of the core wiring board in contact with the insulating coating layer is:
You may make it a flat surface with the core wiring board surface.
The wiring pattern of the core wiring board is press-fitted into the core wiring board.
And is a flat surface with respect to the core wiring board surface,
Good adhesion with the insulation coating layer ensures high reliability.
A line circuit can be provided.

[0014] According to a second aspect of the invention, the steps of a conductive metal foil on at least one major surface of the insulating layer composed of the first liquid crystal polymer is placed, integrated pressure and heat to the front Kishirube the integrated the insulator a conductive metal foil is patterned
A step of forming a layer and the conductive metal foil into a core wiring board, and forming a core wiring board on the conductive metal foil patterning surface of the core wiring board.
Insulation sheet made of the second liquid crystal polymer having a lower melting point than that of the first liquid crystal polymer is positioned and arranged , and pressure / heating is performed.
And further integration with the core wiring board
A predetermined area of the formed insulating sheet is perforated to form the pattern.
And a step of exposing a required portion of the conductive metal foil subjected to the aging . Original characteristics of liquid crystal polymer
Long moisture resistance, high electrical insulation and high-speed signal transmission stability
Yield a highly functional wiring circuit
Can be provided.

Here, the conductive metal foil should be a copper foil .
You can Use copper foil to form the wiring pattern
This makes it easier to yield high-performance wiring circuits.
Can be better provided.

In each of the above aspects , the liquid crystal polymer forming the insulating layer (insulating support) of the core wiring board and the insulating coating layer (cover film or cover sheet) that covers the wiring pattern forming surface is, for example, kishdal ( Trade name. Made by Dartco, Vectra (trade name. Celanese
Manufactured by the company). Here, the liquid crystal polymer, by its molecular structure,
The melting points and the like are also different, and even with the same molecular structure, the melting points vary depending on the crystal structure and additives. For example, Vectran A type (melting point, 285 ° C), Vectran C type (melting point, 325 ° C), BIAC film (melting point, 335 ° C)
Are exemplified.

Further, the thickness of the insulating layer for insulating and separating the wiring pattern layers of the core wiring board is generally 25 to 100 μm.
On the other hand, the thickness of the cover film or cover sheet is generally about 10 to 50 μm. here,
When the insulating layer is formed by laminating a plurality of layers, a combination of insulating sheets and liquid crystal polymers of the same kind or a combination of different insulating sheets and liquid crystal polymers may be used. Especially when a heating step or the like is required, it is preferable to combine an insulating sheet or liquid crystal polymer having a relatively high melting point with an insulating sheet or liquid crystal polymer having a relatively low melting point.

In general, liquid crystal polymers have almost no hygroscopicity, a dielectric constant of about 3.0 (1 MHz), are stable in a wide frequency range, and are thermally deformed by, for example, hot pressing. Also, it is easily joined and integrated with the opposing wiring pattern surface or liquid crystal polymer layer (insulating support) surface. In this case, if the wiring pattern surface or the liquid crystal polymer surface is a roughened surface, the fixing and integration will be stronger.

Further, in each of the above aspects , the core wiring board is preferably a single-sided pattern type or a double-sided pattern type in order to meet the requirement of flexibility, but a multilayer wiring type is required for the requirement of high functionality of the wiring circuit. desired. In the case of a structure that requires electrical connection between the wiring pattern layers, the insulation layer is inserted at the tip of the conductive bumps arranged at a predetermined position on the wiring pattern surface so that the other wiring pattern surface is insulated and separated. By adopting the contact structure, the manufacturing process can be simplified, and moreover, fine and highly reliable connection between the wiring pattern layers can be obtained.

The conductive bumps recommended for connection between the wiring pattern layers can be arranged / formed by printing a conductive paste or the like. Here, the conductive paste is, for example, a paste prepared by mixing conductive powder such as silver, gold, copper, solder powder, alloy powder or composite (mixed) metal powder of these, and a resin binder component. Can be mentioned. Examples of the resin binder component generally include thermoplastic resins such as polycarbonate resin, polysulfone resin, polyester resin and phenoxy resin, and thermosetting resins such as phenol resin, polyimide resin, melamine resin and epoxy resin.

In each of the above aspects , the wiring pattern of the core wiring board is generally formed by photoetching a conductive metal foil such as copper or aluminum having a thickness of about 5 to 35 μm. That is, the wiring pattern is formed by selectively etching the conductive metal foil attached to the surface of the liquid crystal polymer film. Therefore, in general, the wiring pattern protrudes from the liquid crystal polymer film surface by the thickness thereof, but if this is pressed into the liquid crystal polymer film surface to form a flat surface with the liquid crystal polymer film surface, the cover will be covered. In addition to facilitating the placement and coating of the film, a dense coating layer such as a pattern with no irregularities is formed, so that the inclusion of voids can be reduced and the reliability of the cover coat can be improved. The adhesion strength to In the present invention, the insulating layer that supports the wiring pattern and the insulating coating layer that covers the wiring pattern forming surface are both formed of a liquid crystal polymer, and since an adhesive layer does not need to be interposed, the adhesive layer is It significantly reduces environmental problems such as flame retardants. That is, it is possible to provide a highly reliable wiring circuit having the moisture resistance, high electrical insulation, and high-speed signal transmission stability, which are the original features of the liquid crystal polymer. In addition, the insulation layer and the insulation coating layer have melting points
Associated with the formation by the selection of different liquid crystal polymers
And, because the precise integration is ensured, the reliability is higher.
It is possible to provide a good wiring circuit.

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIGS. 1, 2 and 3.

FIG. 1 is a sectional view showing the structure of the main part of a wiring board according to the first embodiment. In FIG. 1, 6 is the melting point 3
Liquid crystal polymer film (insulator layer or insulating support) with a thickness of about 25 ° C. and a thickness of about 50 μm, and 7a and 7b are wiring patterns made of electrolytic copper foil with a thickness of about 12 μm provided on both sides of the liquid crystal polymer film 6. , 8a, 8b are the wiring patterns 7a,
7b Forming surface is integrated and covered Melting point: 285 ℃, Thickness: 30
It is a liquid crystal polymer film of about μm.

Here, the liquid crystal polymer film 6 and the wiring patterns 7a and 7b constitute a core wiring board 9, and the liquid crystal polymer films 8a and 8b are perforated at required portions (or areas) to form the wiring pattern. Connected parts of 7a and 7b
A cover coat is formed exposing 10a and 10b.
Reference numeral 11 is an interlayer connecting portion that connects between the wiring patterns 7a and 7b formed on both surfaces of the core wiring board 9. As the perforation method, a method of irradiating excimer, YAG or semiconductor laser light to volatilize the liquid crystal polymer in the selected region is suitable. Of course, other methods may be used, for example, a mask may be arranged in advance in a selected area, a cover film may be attached, and then the mask may be removed.

FIG. 2 is a sectional view showing the structure of the main part of a wiring board according to the second embodiment. In this embodiment, the core wiring board 9 is of a multi-layer wiring pattern type, and the wiring pattern layers are connected by through-holes or vias. In FIG. 2, 6a, 6b and 6c have a melting point of about 325 ° C. and a thickness of about 100 μm, and are laminated / integrated liquid crystal polymer films (insulator layers), and 7a ′ and 7b ′ are the liquid crystal polymer film 6a,
Inner layer wiring patterns formed on the surfaces 6b and 6c, and 7a and 7b are outer layer wiring patterns formed on the liquid crystal polymer films 6b and 6c. The inner layer wiring patterns 7a ′, 7b ′ and the outer layer wiring patterns 7a, 7b are both made of electrolytic copper foil with a thickness of about 12 μm, and these wiring patterns 7a, 7b, 7a ′, 7b
The b's are connected by the conductive bumps 12.

Further, 8a and 8b are integrated with the wiring pattern 7a and 7b forming surface and have a melting point of about 285 ° C. and a thickness of 25 μm.
It is a liquid crystal polymer film of a degree.

Here, the liquid crystal polymer films 6a, 6b, 6
c and the wiring patterns 7a, 7b, 7a ', 7b' constitute a core wiring board 9 '. Also, liquid crystal polymer film
8a and 8b are perforations at required locations (or areas) with harmonics of a YAG laser, and the connected portions 10 of the wiring patterns 7a and 7b.
A cover coat is formed exposing a and 10b. Reference numeral 11 denotes an interlayer connecting portion that connects the wiring patterns 7a and 7b formed on both surfaces of the core wiring board 9 '.

Next, an example of a method of manufacturing a wiring board in which the core wiring board 9'is a multilayer wiring pattern type will be described.

A metal mask is positioned and arranged on one main surface of an electrolytic copper foil having a thickness of 12 μm, a conductive paste is printed,
After drying, the same metal mask was used to print the conductive paste at the same position and the drying was repeated to form a conical conductive bump having a height of about 200 μm. The metal mask has a diameter of approximately 250 μm and is applied to the required location on a stainless steel plate.
250 μm holes are formed, and the conductive paste is a conductive composition composed of silver powder and an epoxy resin.

The electro-deposited copper foil provided with the above-mentioned conductive bumps at required positions is made to face one end of a liquid crystal polymer film having a thickness of about 100 μm prepared in advance with the tip end side of the conductive bumps being opposed to the other. Place copper foil on the surface. In this state,
A vacuum hot press process was performed, and electrolytic copper foils were pressure bonded to both sides of the liquid crystal polymer film to prepare a double-sided copper foil-bonded sheet in which electrolytic copper foils on both sides were electrically connected by conductive bumps.

After that, a dry film type photosensitive resist is adhered to both copper foil surfaces of the double-sided copper foil adhering sheet, a wiring pattern film mask is positioned, an exposure process is performed, and then an etching process is performed to perform wiring patterning. By doing so, a double-sided wiring type core wiring board is produced. Next, a liquid crystal polymer film with a thickness of about 50 μm and an electrolytic copper foil with a thickness of 12 μm are sequentially laminated on both sides of the core wiring board, and vacuum heat press processing is applied to form a multilayer base plate with copper foil on both sides. Create. At this time, conductive bumps are provided in advance at the required positions on one main surface of the electrolytic copper foil by the above-mentioned means.

Thereafter, a photosensitive resist is attached to each of the copper foil surfaces of the double-sided copper foil-adhered multilayer base plate, a wiring pattern film mask is positioned, an exposure process is performed, and an etching process is performed to perform wiring patterning. Then, a multilayer wiring pattern type core wiring board is produced. Here, in the case where a copper through hole is additionally provided, it is possible to carry out a method of patterning after through hole drilling and through hole plating.

Next, a liquid crystal polymer film having a thickness of about 30 μm was joined and integrated with the main surface of the multilayer wiring pattern type core wiring board to form a cover coat layer. Then, a desired portion (position) of the cover coat is selectively irradiated with excimer laser light through the metallization layer to form a hole to expose the required portion of the wiring pattern, and the inner wall surface of the through hole and the wiring pattern exposed surface are exposed. A wiring board is obtained by growing a copper plating layer.

[0041] In the manufacturing method of the wiring substrate, bonding of the copper foil at the time of manufacture of the core wiring board, and when bonding the cover film, because it is thermally utilizing the characteristics of liquid crystal polymers, adhesives Is unnecessary and the manufacturing process is greatly simplified. In addition, when disposing of the wiring board, since harmful substances including halogen and phosphorus are not generated by combustion, it is advantageous in terms of environmental hygiene, and because of the simple configuration of the combination of thermoplastic resin and metal, It also has the feature that it can be easily separated into a resin component and a metal component by heat melting, and that the resin and metal can be separated and recycled.

FIG. 3 is a sectional view showing the structure of the main part of a wiring board according to the third embodiment. The wiring board of this embodiment is basically the same as the case of the first embodiment, in which the wiring patterns 7a and 7b are press-fitted into the insulating layer 6 and the main surface of the core wiring board 9 is made flat. Differences in points. If you take this configuration,
Since the cover films 8a and 8b are pressed and integrated on a flat surface, not only the covering operation of the cover coat is easy, but also the pattern surface has no unevenness and the insulating coating has good flatness and good adhesion. Is done. In addition, since the insulator layer 6 and the cover coat (insulating coating layer) are formed of a liquid crystal polymer having a low dielectric constant, excellent high-frequency characteristics are obtained, and low hygroscopicity and good flexibility allow Constructing a light, thin, short, and highly reliable wiring board.

The present invention is not limited to the above examples, and various changes can be made without departing from the spirit of the invention. For example, the thickness of the insulating layer (insulating support), the thickness of the insulating coating layer (cover coat), the material of the wiring pattern, the number of wiring pattern layers of the core wiring board, the material for forming the conductive bumps, etc. -It can be appropriately selected and used according to the purpose.

[0044]

According to the present invention, since it is not necessary to interpose an adhesive layer, not only the environmental problem caused by the flame retardant due to the inclusion of the adhesive layer is solved but also the liquid crystal polymer is used. Provided is a highly reliable wiring board and a method for manufacturing the same, which makes use of the original characteristics such as moisture resistance and excellent high-frequency characteristics.

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main-part configuration of a wiring board according to a first embodiment.

FIG. 2 is a cross-sectional view showing a main-part configuration of a wiring board according to a second embodiment.

FIG. 3 is a cross-sectional view showing a main part configuration of a wiring board according to a third embodiment.

FIG. 4 is a cross-sectional view showing a configuration of a main part of a conventional wiring board.

[Explanation of symbols]

6 ... Insulator layers 7a, 7b, 7a ', 7b' made of liquid crystal polymer ... Wiring patterns 8a, 8b ... Insulating coating layer (cover coat) made of liquid crystal polymer 9, 9 '... Core wiring board 10a, 10b …… Wiring pattern exposed part 11 …… Through hole connection part 12 …… Via connection part (conductive bump)

Continuation of the front page (56) Reference JP-A-10-190231 (JP, A) JP-A-8-78845 (JP, A) JP-A-8-97565 (JP, A) JP-A-8-264939 (JP , A) JP-A-11-289165 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/46

Claims (2)

(57) [Claims] 1. An insulator layer made of a first liquid crystal polymer .
And a core wiring board having a wiring pattern formed on at least one main surface of the insulator layer , and a second liquid crystal poly having a melting point lower than that of the first liquid crystal polymer.
Consists mer, the wiring pattern of the core wiring board is integrated into the surface that is shaped <br/> formed, and the insulation coating layer that have a perforation for exposing the desired portions of the wiring pattern A wiring board characterized by being provided. 2. A conductive metal foil is placed on at least one main surface of an insulator layer made of a first liquid crystal polymer, and pressure / heating is performed.
A step of integrating and was the integrated front Kishirube conductive metal foil is patterned
A step of forming the insulating layer and the conductive metal foil into a core wiring board, and on the conductive metal foil patterning surface of the core wiring board ,
A step of positioning and arranging an insulating sheet made of a second liquid crystal polymer having a melting point lower than that of the first liquid crystal polymer , and pressing and heating to further integrate the insulating sheet; and an insulating sheet integrated with the core wiring board. And a step of exposing a predetermined portion of the patterned conductive metal foil to form a predetermined area, and a method of manufacturing a wiring board.