JP2000138422A - Wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the practicability of a wiring board by omitting a bonded integral configuration by means of an adhesive, to reduce environmental issues, and to transmit high-speed signals without further degrading electric characteristics, particularly, the signals. SOLUTION: A wiring board is provided with a core wiring board 9 carrying wiring patterns 7a and 7b formed on at least one main surface of an insulating layer 6 made of a liquid crystal polymer. The wiring board is also provided with insulating coating layers 8a and 8b which are integrated with the surfaces of the wiring board 9 on which the wiring pattern 7a and 7b are formed, have bored holes for exposing required portions 10a and 10b of the pattern 7a and 7b, and are made of the liquid crystal polymer.

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 wiring pattern surface insulated and covered, and a method of manufacturing the wiring board.

[0002]

2. Description of the Related Art Along with the miniaturization of electronic devices and the like, a wiring board for forming a circuit is required to be compact or have high-density wiring. In response to such a demand, a wiring board has been developed as shown in FIG. In FIG. 4, 1 is 25 μ in thickness
m is a polyimide resin film with an adhesive (insulating support), 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 wiring pattern 2 formation surface
A polyimide resin film (cover film) with an adhesive of about 25 μm has a through-hole connection portion. Note that 5
Each of a and 5b is an adhesive layer, and the exposed region 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. That is, thickness 25
A copper foil-bonded sheet is prepared by bonding a copper foil having a thickness of about 12 to 18 μm to the main surface of a polyimide resin film 1 of about μm via an adhesive layer 5a. Next, a predetermined area of the copper foil-bonded sheet is perforated to provide a through-hole for interlayer connection, and then a conductive layer is formed and printed on the inner wall surface of the perforated copper foil. Thereafter, the wiring pattern 2 is formed by performing a photo-etching process, and the polyimide resin film 1 having the wiring pattern 2 is connected between the wiring patterns 2 on both surfaces.
And

On the other hand, a polyimide resin film (cover film) 3 having a thickness of about 12 .mu.m with an adhesive layer having a thickness of about 15 .mu.m is prepared by stamping and pressing a required area. Thereafter, 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 is crimped and integrated with the wiring patterning 2 surface.

[0005]

However, the above-mentioned wiring board has advantages such as being compact and flexible, but has the following disadvantages. That is, (a) a polyimide resin film (insulating support) 1 and a wiring pattern 2
(Copper foil, etc.), and (b) an adhesive layer 5a, 5b, respectively, for joining and integrating the cover film 3 to the surface on which the wiring pattern 2 is formed. . Incidentally, the adhesive layers 5a and 5b are generally required to be flame-retardant, and in response to this requirement, a flame retardant such as a halogen compound or a phosphorus compound is added or blended. I have.

[0006] Here, the adhesive layers 5a, 5a,
The insertion and presence of 5b not only adversely affects the electrical characteristics of the configured wiring board itself, but also causes the flame retardant to be used in the manufacturing process of the wiring board or in the disposal of the wiring board. It can raise issues.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has high practicability in which the structure of joining and integrating with an adhesive is omitted, reduces environmental problems, and has better electrical characteristics than conventional substrates. In particular, it is an object of the present invention to provide a wiring board capable of transmitting a high-speed signal without deteriorating it, and a method of manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a core wiring board having a wiring pattern formed on at least one main surface of an insulating layer made of a liquid crystal polymer, and a wiring pattern forming surface of the core wiring board. An insulating coating layer made of a liquid crystal polymer that is integrated and has a hole for exposing a required portion of the wiring pattern.

According to a second aspect of the present invention, in the wiring board according to the first aspect, the core wiring board is of a multilayer wiring pattern type.

According to a third aspect of the present invention, in the wiring board according to the first or second aspect, the wiring pattern layers of the core wiring board are joined by conductive bumps penetrating an insulator layer. I do.

According to a fourth aspect of the present invention, in the wiring board according to any one of the first to third aspects, the melting point of the insulating coating layer integrated with the wiring pattern forming surface of the core wiring board is:
It is characterized by being lower than the melting point of the liquid crystal polymer forming the insulator layer of the core wiring board.

According to a fifth aspect of the present invention, in the wiring board according to any one of the first to fourth aspects, the wiring pattern of the core wiring board is made of copper foil.

According to a sixth aspect of the present invention, in the wiring board according to any one of the first to fifth aspects, the wiring pattern of the core wiring board in contact with the insulating coating layer forms a flat surface with the surface of the core wiring board. It is characterized by being.

According to a seventh aspect of the present invention, a conductive metal foil is placed on at least one main surface of an insulator layer made of a liquid crystal polymer,
A step of pressurizing and heating and integrating, a step of wiring-patterning the pressure-integrated conductive metal foil to form a core wiring board, and an insulating sheet made of a liquid crystal polymer on a wiring pattern forming surface of the core wiring board. A step of positioning and arranging to integrate under pressure and heat, and a step of perforating a predetermined region of the insulating sheet on the wiring pattern forming surface to expose a required portion of the wiring pattern. It is a manufacturing method.

According to an eighth aspect of the present invention, in the method for manufacturing a wiring board according to the seventh aspect, the conductive metal foil is a copper foil.

In each of the above inventions, the insulator layer (insulating support) of the core wiring board and the insulating coating layer (cover film or cover sheet) covering the surface on which the wiring pattern is formed
The liquid crystal polymer which forms is, for example, Xidal (trade name, manufactured by Dartco), Vectra (trade name, manufactured by Clanese)
Is a multiaxially oriented thermoplastic polymer. Here, the melting point of the liquid crystal polymer differs depending on the molecular structure, and the melting point varies depending on the crystal structure and the additive even with the same molecular structure. For example, Vectran A
Type (melting point, 285 ° C), Vectran C type (melting point,
325 ° C.), BIAC film (melting point, 335 ° C.) and the like.

The thickness of the insulator layer that insulates and separates 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 insulator layer is formed by laminating a plurality of layers, a combination of the same kind of insulator sheet and liquid crystal polymer or a combination of different kinds of insulator sheets and liquid crystal polymer may be used. In particular, when a heating step or the like is required, it is preferable to combine an insulator sheet or a liquid crystal polymer having a relatively low melting point with an insulator sheet or a liquid crystal polymer having a relatively high melting point.

In general, a liquid crystal polymer has almost no hygroscopicity and a dielectric constant of about 3.0 (1 MHz), and is stable not only in a wide frequency range but also thermally deformed by, for example, a hot press. In addition, it can be easily joined and integrated with the opposing wiring pattern surface or liquid crystal polymer layer (insulating support) surface. In this case, in the case of the roughened surface of the wiring pattern surface and the liquid crystal polymer surface, the fixation / integration becomes stronger.

In each of the above-mentioned inventions, the core wiring board is preferably a single-sided pattern type or a double-sided pattern type in order to meet the requirement for flexibility. desired. In the case of a configuration that requires electrical connection between the wiring pattern layers, the insulating bump is inserted through the insulator layer at the end of the conductive bump disposed at a predetermined position on the wiring pattern surface, so that the insulating bumps are separated from other wiring pattern surfaces that are insulated and separated. When the contact structure is adopted, the manufacturing process can be simplified, and furthermore, fine and highly reliable connection between wiring pattern layers can be obtained.

The conductive bumps recommended for connection between the wiring pattern layers can be arranged and formed by printing a conductive paste or the like. Here, examples of the conductive paste include pastes prepared by mixing a conductive powder such as silver, gold, copper, and solder powder, or an alloy powder or a composite (mixed) metal powder thereof with a resin binder component. No. Examples of the resin binder component 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 inventions, the wiring pattern of the core wiring board is generally formed by photo-etching a conductive metal foil of, for example, copper or aluminum having a thickness of about 5 to 35 μm. That is, a wiring pattern is formed by selective etching of the conductive metal foil adhered to the liquid crystal polymer film surface. Therefore, in general, the wiring pattern protrudes from the liquid crystal polymer film by the thickness thereof, but if this is pressed into the liquid crystal polymer film surface to make the liquid crystal polymer film flat with the flat surface, Not only is it easy to arrange and cover the film, but also because it forms a dense coating layer such as a pattern with no irregularities, it reduces the entrapment of voids and improves the reliability of the cover coat. The adhesion strength with respect to is improved. According to the first aspect of the present invention, the insulating layer for supporting the wiring pattern and the insulating coating layer for covering the wiring pattern forming surface are both formed of a liquid crystal polymer, and it is not necessary to insert an adhesive layer. It greatly reduces environmental problems caused by the flame retardant contained in the agent layer. That is,
It is possible to provide a highly reliable wiring circuit having moisture resistance, high electrical insulation, and high-speed signal transmission stability, which are the essential features of the liquid crystal polymer.

According to the second aspect of the present invention, the multi-layer wiring pattern type of the core wiring board makes use of the inherent characteristics of the liquid crystal polymer, such as moisture resistance, high electrical insulation and high-speed signal transmission stability, while providing high performance. It is possible to provide a simplified wiring circuit.

According to the third aspect of the present invention, since the connection between the wiring pattern layers of the core wiring board is made of conductive bumps penetrating the insulator layer, a fine and highly reliable connection is provided. A wiring circuit can be provided.

According to the fourth aspect of the invention, since the insulator layer and the insulating coating layer are formed by selecting a liquid crystal polymer having different melting points, dense integration is ensured, so that a more reliable wiring is provided. Circuit can be provided.

According to the fifth aspect of the present invention, since the wiring pattern of the core wiring board is made of copper foil, it is possible to provide a wiring circuit having easy design specifications and good circuit characteristics.

According to the sixth aspect of the present invention, since the wiring pattern of the core wiring board is press-fitted into the core wiring board and forms a flat surface with respect to the core wiring board surface, the wiring pattern with the insulating coating layer is excellent. Adhesion is achieved, and a highly reliable wiring circuit can be provided.

According to the seventh aspect of the present invention, a high-performance wiring circuit can be provided with a high yield by utilizing the inherent characteristics of the liquid crystal polymer such as moisture resistance, high electrical insulation and high-speed signal transmission stability.

According to the eighth aspect of the present invention, by using a copper foil for forming a wiring pattern, it is possible to more easily provide a highly functionalized wiring circuit with a high yield.

[0029]

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

FIG. 1 is a cross-sectional view showing the structure of a main part of a wiring board according to the first embodiment. In FIG. 1, 6 is the melting point.
A liquid crystal polymer film (insulator layer or insulating support) having 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 having 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 Integrates and coats on the forming surface Melting point 285 ° C, thickness 30
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 perforate required portions (or regions). Connected parts of 7a and 7b
A cover coat exposing 10a and 10b is formed.
Reference numeral 11 denotes an interlayer connecting portion connecting 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 a selected region is suitable. Of course, another method may be used. For example, a mask may be disposed in a selected region in advance, and after the cover film is bonded, the mask may be removed.

FIG. 2 is a cross-sectional view showing a main structure of a wiring board according to the second embodiment. This embodiment employs a configuration in which the core wiring board 9 is of a multilayer wiring pattern type, and through-hole connections and via connections are made between wiring pattern layers. 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 and integrated liquid crystal polymer films (insulator layers), and 7a ′ and 7b ′ are the liquid crystal polymer films 6a and 6b.
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. Each of the inner layer wiring patterns 7a 'and 7b' and the outer layer wiring patterns 7a and 7b is made of electrolytic copper foil having a thickness of about 12 .mu.m, and these wiring patterns 7a, 7b, 7a 'and 7b are formed.
The conductive bumps 12 are connected between b ′.

Further, 8a and 8b are integrated with the surface on which the wiring patterns 7a and 7b are formed, 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 '. In addition, liquid crystal polymer film
8a and 8b are formed by drilling required portions (or regions) with harmonics of a YAG laser, and connecting portions 10a of the wiring patterns 7a and 7b.
A cover coat exposing a and 10b is formed. Reference numeral 11 denotes an interlayer connecting portion for connecting between 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, and a conductive paste is printed.
After drying, a conductive paste was printed at the same position using the same metal mask, and drying was repeated to form a conical conductive bump having a height of about 200 μm. The metal mask has a diameter of about 250 μm
The conductive paste has a hole of 250 μm, and the conductive paste is a conductive composition composed of silver powder and epoxy resin.

An electro-deposited copper foil having the conductive bumps provided at required positions is placed on one side of a liquid crystal polymer film having a thickness of about 100 μm, which is prepared in advance. Place copper foil on the surface. In this state,
Vacuum hot pressing was performed to press the electrolytic copper foil on both sides of the liquid crystal polymer film, thereby producing a double-sided copper foil-bonded sheet in which the electrolytic copper foils on both sides were electrically connected by conductive bumps.

Thereafter, a dry film type photosensitive resist is bonded to both copper foil surfaces of the double-sided copper foil-bonded sheet, a wiring pattern film mask is positioned, an exposure process is performed, and an etching process is performed to perform wiring patterning. By doing so, a double-sided wiring type core wiring board is manufactured. Next, on both sides of the core wiring board, a liquid crystal polymer film having a thickness of about 50 μm and an electrolytic copper foil having a thickness of 12 μm are sequentially laminated and arranged, and subjected to vacuum hot press processing to form a multilayer base plate having a double-sided copper foil. Make it. At this time, a conductive bump is provided in advance at a required portion of one principal face of the electrolytic copper foil by the above-described means.

Thereafter, a photosensitive resist is stuck on each of the copper foil surfaces of the multi-layer base plate with a double-sided copper foil, a wiring pattern film mask is positioned, an exposure process is performed, and an etching process is performed. Then, a multilayer wiring pattern type core wiring board is manufactured. Here, in the case where a copper through hole is provided, a method in which a hole is formed in advance and then plated with a through hole and patterned.

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. Next, a required portion (position) of the cover coat is selectively irradiated with excimer laser light through a metallization layer to perform perforation, exposing a required portion of the wiring pattern, and forming a hole on the inner wall surface of the through hole and the exposed surface of the wiring pattern. The wiring board is obtained by growing the copper plating layer.

In the above-mentioned method of manufacturing a wiring board, the bonding and bonding of the copper foil and the cover film at the time of manufacturing the core wiring board is performed by utilizing the properties of the liquid crystal polymer and being melted by heat. Is unnecessary, and the manufacturing process is greatly simplified. Also, in the disposal of wiring boards, etc., there is no generation of harmful substances including halogen and phosphorus by combustion, so it is advantageous in terms of environmental hygiene and because it has a simple configuration of a combination of thermoplastic resin and metal, Another advantage is that the resin and metal can be easily separated by heat melting, and the resin and metal can be separated and recycled.

FIG. 3 is a sectional view showing the structure of a main part of a wiring board according to the third embodiment. The wiring board of this embodiment is basically the same as that of the first embodiment, in which the wiring patterns 7a and 7b are press-fitted into the insulator layer 6 and the main surface of the core wiring board 9 is flattened. Differs in that If you adopt this configuration,
The cover films 8a and 8b are pressure-bonded and integrated on a flat surface, which not only facilitates the coating operation of the cover coat, but also has excellent flatness and good adhesion insulating coating with no unevenness on the pattern surface. Is performed. 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, low moisture absorption, and good flexibility are provided. A light, thin, short and highly reliable wiring board is constructed.

The present invention is not limited to the above examples, and various changes can be made without departing from the gist of the invention. For example, the thickness of the insulator 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 first aspect of the present invention, since there is no need to insert an adhesive layer, not only environmental problems caused by the flame retardant due to the inclusion of the adhesive layer are eliminated, but also In addition, a highly reliable wiring board utilizing the inherent characteristics of liquid crystal polymer such as moisture resistance and excellent high frequency characteristics is provided.

According to the second aspect of the present invention, a highly functional wiring board is provided while taking advantage of the inherent characteristics of the liquid crystal polymer such as moisture resistance and excellent high-frequency characteristics.

According to the third aspect of the present invention, there is provided a wiring board having fine and highly reliable connections utilizing the inherent characteristics of the liquid crystal polymer such as moisture resistance and excellent high frequency characteristics.

According to the fourth aspect of the present invention, the dense integration of the insulator layer and the insulating coating layer is ensured, and a more reliable wiring board is provided.

According to the fifth aspect of the present invention, there is provided a wiring board which can be easily designed and designed and has good circuit characteristics.

According to the sixth aspect of the present invention, a highly reliable wiring board is provided with good adhesion of the insulating coating layer to the core wiring board surface.

According to the seventh aspect of the present invention, a moisture-resistant property and excellent high-frequency characteristics, which are inherent characteristics of the liquid crystal polymer, are utilized, and a highly functionalized wiring board can be easily provided with a high yield.

According to the invention of claim 8, a highly functionalized wiring board can be provided more easily and with a higher yield.

[Brief description of the drawings]

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

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

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

FIG. 4 is a cross-sectional view showing a main part configuration 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 ... exposed wiring pattern 11 ... through-hole connection 12 ... via connection (conductive bump)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H05K 3/46 H05K 3/46 T (72) Inventor Akira Yonezawa 3-28-7 Nakamagome, Ota-ku, Tokyo No. Yamaichi Denki Co., Ltd. F-term (reference) 4F100 AB01B AB17B AB33B AK01A AK01C AR00A AR00C BA03 BA07 BA10A BA10C DC11C DC21B EA011 EA013 EG00A EG00B EJ15 EJ152 EJ17 EJ171 EJ173 J04 EJ42 J04 EJ42 EJ42 EJ42 EJ42 EJ421 CC60 CD23 CD32 GG03 GG09 GG20 5E338 AA03 AA12 AA16 BB12 BB13 BB63 BB80 EE11 EE30 EE60 5E346 AA02 AA12 AA43 AA60 CC08 CC32 DD02 DD12 FF24 GG15 HH06 HH40

Claims (8)

[Claims] A core wiring board having a wiring pattern formed on at least one principal surface of an insulator layer made of a liquid crystal polymer; and a wiring pattern forming surface of the core wiring board integrated with a required portion of the wiring pattern. An insulating coating layer made of a liquid crystal polymer having perforations for exposure. 2. The wiring board according to claim 1, wherein the core wiring board is a multilayer wiring pattern type. 3. The wiring board according to claim 1, wherein the wiring pattern layers of the core wiring board are joined by conductive bumps penetrating an insulator layer. 4. The wiring board according to claim 1, wherein the melting point of the liquid crystal polymer forming the insulating coating layer is lower than the melting point of the liquid crystal polymer forming the insulating layer. 5. The wiring board according to claim 1, wherein the wiring pattern of the core wiring board is made of copper foil. 6. The wiring board according to claim 1, wherein the wiring pattern of the core wiring board in contact with the insulating coating layer has a flat surface with the surface of the core wiring board. 7. A step of placing a conductive metal foil on at least one main surface of an insulator layer made of a liquid crystal polymer, and pressurizing and heating and integrating the conductive metal foil; Forming an insulating sheet made of a liquid crystal polymer on the wiring pattern forming surface of the core wiring board, and pressing and heating and integrating the insulating sheet; and forming an insulator on the wiring pattern forming surface. Perforating a predetermined area of the sheet to expose a required portion of the wiring pattern. 8. The method according to claim 7, wherein the conductive metal foil is a copper foil.