JP2000236145A - Wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the thickness of a wiring board and to form a photoresist layer without producing air bubbles and exposed portions, by making a conductive wire layer embedded in a recessed portion formed in one surface of an insulating layer and a conductive wire layer embedded in a through hole, extending from the bottom surface of the insulating layer to the embedded conductive wire layer. SOLUTION: Because the formed top surfaces of embedded conductive layers 2, 3 are flush with the top surface of an insulating layer 1, when a photoresist layer or a solder-resist layer is formed on these embedded conductive layers 2, 3, a level difference is not produced on the photoresist layer or the solder- resist layer. Accordingly, this will produces neither air bubbles or reduce the thickness of the photoresist layer or the solder-resist layer at the top shoulder portions of the embedded conductive layers 2, 3 or expose the top shoulder portions of the embedded conductive layers 2, 3. Furthermore, this can make it possible to use a sheet-like photoresist layer or solder-resist layer, which facilitates the formation of the layer and does not stain the formation environment of the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for electronic equipment and the like and a method for manufacturing the same. More specifically, a film such as a single-sided wiring board, a double-sided wiring board, or a build-up wiring board is laminated in multiple layers. And a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a wiring board used for assembling various electronic devices, a hard base material such as glass epoxy,
After bonding a conductive layer such as a copper foil, the conductive layer is processed into a desired circuit wiring pattern shape, and a wiring board using a resin film has recently been awarded.
Examples of this type of wiring board include, for example, Japanese Patent Application Laid-Open No. 10-209.
No. 224. Such a wiring board will be described below. FIG. 6 is a longitudinal sectional view of a conventional wiring board. In FIG. 6, reference numeral 21 denotes an insulating layer made of a polyimide resin or the like, on which conductive layers 22, 232 of copper or the like are formed in a predetermined pattern. Here, the conductive layer 22 is a conductive layer serving as an independent circuit wiring, and 23 is a conductive layer for establishing conduction with the back side of the insulating layer 21. The conductive layer 2
2 and 23 are formed, for example, by etching a copper foil or the like bonded to the insulating layer 21 via an adhesive into a desired pattern. In the insulating layer 21 below the conductive layer 23, there is formed a through-hole 24 extending from the back surface of the insulating layer 21 to the conductive layer 23. 25 are buried.

However, in the wiring board having the above structure, since the conductive layers 22 and 23 are formed so as to protrude from the surface of the insulating layer 21, the thickness of the entire wiring board is increased, which is an obstacle to the reduction in thickness. In addition to the above, when a photoresist or a solder resist layer (not shown) is formed on these conductive layers 22 and 23, bubbles are formed at lower corners of the conductive layers 22 and 23, The photoresist or solder resist layer on the upper shoulder of 23 becomes thinner,
In an extreme case, the upper shoulders of the conductive layers 22 and 23 may be exposed, which causes a problem that various inconveniences caused by the bubbles and the exposure occur in a subsequent etching process, a chemical solution treatment process, and the like. Was. When the photoresist layer is formed by a coating method, a method is generally used in which a liquid photoresist liquid is dropped on the insulating layer 21 using a spin coater, but this method is troublesome. In addition, there is a problem that the working environment becomes dirty. Further, since the conductive through-holes 24 are deep, it takes a long time to form the conductive through-holes 24, which may cause inconveniences such as peeling in other parts, and the formation of the conductive conductive material 25 takes a long time by the plating method. In addition, there is a problem that it is difficult to form the conductive material 25 for conduction to the corners.

[0004]

SUMMARY OF THE INVENTION Therefore, according to the present invention, it is possible to reduce the thickness of a wiring board and to form a photoresist layer or a solder resist layer on a conductive layer without generating bubbles or exposed portions. An object of the present invention is to provide a wiring board which enables use of a sheet-like photoresist layer or a solder resist layer. Another object of the present invention is to provide a manufacturing method capable of manufacturing a wiring board having the above various excellent features.

[0005]

According to the present invention, there is provided a wiring board comprising: an embedding recess formed on one surface of an insulating layer; a conductive layer embedded in the embedding recess; and a back surface of the insulating layer. A wiring substrate having a through hole reaching a buried conductive layer and a conductive conductive layer buried in the through hole. The method of manufacturing a wiring board according to the present invention includes the steps of forming a recess for embedding on the surface of the insulating layer,
A step of burying a conductive layer in the burying recess, a step of forming a through hole reaching the burying conductive layer from the back surface of the insulating layer, and a step of burying and forming a conductive layer in the through hole. A method for manufacturing a wiring board, comprising:

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION
A buried recess formed on one surface of the insulating layer; a buried conductive layer formed in the buried recess; a through hole reaching the buried conductive layer from the other surface of the insulating layer; A wiring board comprising: a conductive layer formed for conduction.

According to a second aspect of the present invention, there is provided the wiring board according to the first aspect, wherein the buried conductive layer is formed by plating.

According to a third aspect of the present invention, the buried conductive layer is formed by an electroless plating method or an electrolytic plating method on the electroless plating layer. 2. The wiring board according to 2.

The invention according to claim 4 of the present invention is the wiring board according to any one of claims 1 to 3, wherein the buried conductive layer is formed substantially flush with an upper surface of the insulating layer.

The invention according to claim 5 of the present invention is the wiring substrate according to any one of claims 1 to 4, wherein the buried conductive layer is formed of copper.

The invention according to claim 6 of the present invention is the wiring substrate according to any one of claims 1 to 5, wherein the insulating layer is a wholly aromatic polyester liquid crystal polymer film.

The invention according to claim 7 of the present invention is the wiring board according to any one of claims 1 to 6, wherein the inner wall surface of the embedding recess is formed with a rough surface.

The invention according to claim 8 of the present invention is characterized in that the conductive layer for conduction is formed by either an electroless plating method, an electrolytic plating method on the electroless plating layer, or a method of applying a conductive paste. 2. The semiconductor device according to claim 1, wherein:
8. The wiring board according to any one of items 7 to 7.

According to a ninth aspect of the present invention, there is provided a method for forming a photoresist layer on a surface of an insulating layer, etching the insulating layer exposed from the photoresist layer to form a recess for burying, Forming a conductive layer in the recess for use, forming a through hole reaching the buried conductive layer from the back surface of the insulating layer, and forming a conductive layer for conduction in the through hole. Is a method of manufacturing a wiring board.

According to a tenth aspect of the present invention, there is provided a step of roughening the inner surface of the embedding recess formed on the surface of the insulating layer by a wet blast method or a liquid honing method, and the step of roughening the roughened surface. Forming a conductive layer by an electroless plating method or an electrolytic plating method on the electroless plating layer.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a wiring board A according to a first embodiment of the present invention.
FIG. In FIG. 1, reference numeral 1 denotes an insulating layer having, for example, a coefficient of thermal expansion of 5 to 20 × 10 ⁻⁶ / ° C., a water vapor transmission rate of 1 g · 20 μ / m ² · day or less, a water absorption rate of 0.1% or less, and a melting point of 1%. A resin film having a thickness of 260 ° C. or more and a thickness of about 25 to 50 μm, for example, a wholly aromatic polyester liquid crystal polymer film is used. The wholly aromatic polyester liquid crystal polymer film is, for example, NP / CT manufactured by K Company and has a coefficient of thermal expansion of 15 to 20 × 10 ⁻⁶ / ° C. and a water vapor transmission rate of 0.13 g · 20 μ / m ² · day (40). ℃, 90% R
H), having a water absorption of 0.04% (23 ° C., 24H 3), melting points of 280 ° C. (NP type) and 325 ° C. (CT type). In the present invention, as the insulating layer 1,
The use of the above-mentioned wholly aromatic polyester liquid crystal polymer film has various excellent features described later, but in addition, a flexible resin film such as polyester, epoxy, or polyimide may be used. 2 and 3 are insulating layers 1
Is a buried conductive layer made of, for example, copper and having a thickness of about 18 μm, which is buried in the burying recesses 4 and 5 formed on the surface of the substrate. Here, the buried conductive layer 2 is to be an independent circuit wiring, and 3 is for conduction with the back side of the insulating layer 1. The upper surfaces of both conductive layers 2 and 3 are flush with the upper surface of insulating layer 1. Reference numeral 6 denotes a conductive conductive layer buried in a through-hole 7 extending from the back surface of the insulating layer 1 to the buried conductive layer 3. The above is the embodiment of the wiring board A of the present invention.

FIG. 2 is an enlarged longitudinal sectional view of a main part of the wiring board A of the present invention. That is, the inner wall surfaces 4a, 5a of the embedding recesses 4, 5 formed on the surface of the insulating layer 1 have a surface roughness of about 0.1 to 1.0 [mu] m, preferably 0.5 to 5.0.
It is formed on a rough surface of about μm, and thin metal layers 8 and 9 such as copper are formed on the rough surface by electroless plating. The buried conductive layers 2 and 3 made of copper or the like are formed on the thin metal layers 8 and 9. In such a configuration of the buried conductive layers 2 and 3, since the insulating layer 1 and the buried conductive layers 2 and 3 are fixed on the bottom surface and side surfaces, they are fixed only on the conventional bottom surface shown in FIG. As compared with the conductive layers 22 and 23, the bonding strength is significantly higher. In addition, the bonding strength between the embedded recesses 4 and 5 of the insulating layer 1 and the thin metal layers 8 and 9 is significantly increased by the rough surfaces 4a and 5a. No delamination occurs at each interface.

As shown in FIGS. 1 and 2, the upper surfaces of the buried conductive layers 2 and 3 are formed flush with the upper surface of the insulating layer 1, so that In the case where a photoresist layer or a solder resist layer (not shown) is formed, no step is formed in the photoresist layer or the solder resist layer, so that not only bubbles which are problematic in the conventional wiring board shown in FIG. In addition, the photoresist layer or the solder resist layer is not thinned at the upper shoulders of the buried conductive layers 2 and 3, and the upper shoulders of the buried conductive layers 2 and 3 are not exposed. There is a feature that it does not occur at all. Further, it becomes possible to use a sheet-like photoresist layer or a solder resist layer, which not only greatly facilitates these forming steps but also eliminates contamination of the forming environment. .

Next, a method of manufacturing the wiring board A according to the present invention will be described. FIGS. 3A to 3J are process block diagrams of the method for manufacturing the wiring board A of the present invention, and FIGS.
(F) and FIGS. 5 (g) to (j) are longitudinal sectional views showing the state of the insulating layer and the like in each of the steps. Hereinafter, FIG.
(A)-(j), FIGS. 4 (a)-(f) and FIG. 5 (g)
The method of manufacturing the wiring board A of the present invention will be described with reference to (j). First, the coefficient of thermal expansion is 5-20 × 10 ⁻⁶ /
° C, the water vapor transmission rate is 1 g · 20 μ / m ² · day or less,
An insulating layer 1 made of a wholly aromatic polyester liquid crystal polymer film having a water absorption of 0.1% or less and a melting point of 260 ° C. or more and a thickness of about 25 to 50 μm is prepared [FIG.
FIG. 4 (a)]. Since the surface of the insulating layer 1 is smooth,
The conductive layers 2 and 3 cannot be directly formed on this surface by electroless plating. Next, a photoresist layer 11 having a predetermined pattern is formed on the surface of the insulating layer 1 [FIG.
(B), FIG. 4 (b)], the insulating layer 1 not covered with the photoresist layer 11 is etched by a dry or wet etching method to form recesses 4 and 5 for filling [FIG. 3 (c)]. 4 (c)]. Next, the inner surfaces of the embedding recesses 4 and 5 are subjected to wet blasting or liquid honing to obtain rough surfaces 4a and 5a having a surface roughness of about 0.1 to 10 μm, preferably about 0.5 to 5.0 μm. [FIG. 3 (d), FIG. 4 (d)]. In this wet blasting or liquid honing treatment, for example, when the particle size is 1
Hardness is 1300-2 in Knoop hardness at about 0-300 μm
Pump pressure of 1 to 5 kg / c using polygonal abrasive grains in the range of 500 (or in the range of 7 to 15 in Mohs hardness)
m ² , the ratio between the abrasive grains and the liquid is about 5 to 40 vol%. Since the recessed recesses 4 and 5 of the roughened insulating layer 1 are activated by the roughened surfaces 4a and 5a, direct electroless plating is possible. Therefore, for example, electroless copper plating is applied to the entire inner surfaces of the embedding recesses 4 and 5 of the insulating layer 1 to form the thin metal layer 89. At this time, in the roughening step, the photoresist layer 1
Since the surface of 1 is also roughened and activated, a thin metal layer 89 is also formed on the photoresist layer 11 [FIGS. 3 (e) and 4 (e)]. Next, the photoresist layer 11 is removed together with the thin metal layer 89 thereon (lift-off). Then, the thin metal layer 89 remains on the inner surfaces of the embedding recesses 4 and 5 of the insulating layer 1, that is, the bottom surface and the inner wall surface, and the thin metal layer 8 is formed on the inner surface of the embedding recess 4. A thin metal layer 9 is formed on the inner surface. [FIG. 3 (f), FIG. 4 (f)]. Next, the buried conductive layers 2 and 3 are formed in the burying recesses 4 and 5 by an electroless plating method or an electrolytic plating method using the thin metal layers 8 and 9 (FIG. 3G). , FIG. 5 (g)], and then
A photoresist layer 12 is formed on the back surface of the insulating layer 1 [FIG.
(H), FIG. 5 (h)], the insulating layer 1 not covered with the photoresist layer 12 is dry- or wet-etched to form a through-hole 7 reaching from the back surface to the lower surface of the buried conductive layer 3 [FIG. 3 (i), FIG. 5 (i)]. Next, with or without removing the photoresist layer 12, the conductive layer 6 for conduction is formed in the through hole 7 by an electroless plating method or by an electrolytic plating method on the electroless plating layer. [FIG. 3 (j), FIG. 5 (j)]. In the above step, if the conductive layer 6 is formed without removing the photoresist layer 12, the photoresist layer 12 is removed thereafter. Thus, the wiring board A of the present invention is manufactured.

According to the wiring board A using the insulating layer 1 made of the wholly aromatic polyester liquid crystal polymer film shown in the above embodiment, the water absorption of the insulating layer 1 is 0.04% (2
3 ° C., 24H) and about 70% of the water absorption of the conventional polyimide resin film of 2.9% (23 ° C., 24H).
Accordingly, etching for forming the concave portions 4 and 5 of the insulating layer 1 and wet blasting or liquid honing for roughening the inner surfaces of the concave portions 4 and 5 are accompanied. The rate of change in the moisture absorption of the insulating layer 1 in the process and the process of forming the through hole 7 is 4 × 10 ⁻⁶ / ° C. (R
H) and the rate of change in moisture absorption dimension 22 × 10 ⁻⁶ / ° C. (RH) of the conventional polyimide resin film can be reduced to about one-fifth, and the wiring board A that does not cause deformation of the circuit wiring pattern can be obtained. There is a feature that can be provided.

In the above embodiment, [(FIGS. 3 (e), 4 (e)]] shows the embedding recess 4 of the insulating layer 1;
5, the case where the electroless copper plating thin layer 89 is formed by the electroless plating method after roughening the inner surface of the electroless plating method is described. It is convenient to form the thin metal layer 89 by the sputtering method, but if necessary, after roughening or without roughening the inner surfaces of the embedding recesses 4 and 5 of the insulating layer 1, the metal is formed by sputtering. The thin layer 89 may be formed.

In the above embodiment, the case where only the embedding recesses 4 and 5 are roughened has been described.
The inner wall surface of the through hole 7 may be roughened.

Further, in the above embodiment, the inner wall surfaces of the embedding recesses 4 and 5 and the through hole 7 are shown as being vertical, but they may be formed in a tapered shape. In such a case, there is a feature that the inner wall surface can be easily roughened by utilizing the taper in each inner wall surface roughening step.

[0024]

As described above, according to the present invention, the buried recess on one surface of the insulating layer, the buried conductive layer formed in the buried recess, and the buried conductive layer reaching from the back surface of the insulating layer. Since the wiring board is characterized by having a through-hole and a conductive conductive layer buried in the through-hole, the upper surface of the buried conductive layer can be flush with the upper surface of the insulating layer, When a photoresist layer or a sol-resist layer is formed on the buried conductive layer, the photoresist layer or the solder resist layer at the upper shoulder of the buried conductive layer becomes thinner or the upper shoulder of the buried conductive layer is exposed. And the inconvenience caused by these can be eliminated. In addition, since the upper surface of the buried conductive layer can be flush with the upper surface of the insulating layer, a wiring board that can use a sheet-shaped photoresist layer or a solder resist layer can be provided. The present invention also provides a step of forming a photoresist layer on the surface of the insulating layer, a step of etching the insulating layer exposed from the photoresist layer to form a buried recess, and forming a buried conductive layer in the buried recess. A method of manufacturing a wiring board, comprising: a step of forming a through hole reaching the buried conductive layer from a back surface of the insulating layer; and a step of forming a conductive layer for conduction in the through hole. Accordingly, it is possible to provide a manufacturing method capable of manufacturing a wiring board having the above various excellent features.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a wiring board A according to an embodiment of the present invention.

FIG. 2 is an enlarged longitudinal sectional view of a main part of a wiring board A according to one embodiment of the present invention.

FIG. 3 is a process block diagram illustrating a method for manufacturing the wiring board A of FIG. 1;

FIG. 4 is a longitudinal sectional view showing a state of an insulating layer and the like in each of the first half of a series of steps for explaining a method of manufacturing the wiring board A of FIG. 1;

FIG. 5 is a longitudinal sectional view showing a state of an insulating layer and the like in each of the latter half of a series of steps for explaining a method of manufacturing the wiring board A of FIG. 1;

FIG. 6 is a partial longitudinal sectional view of a conventional wiring board.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating layer 2, 3 conductive layer (copper layer) 4, 5 recess for embedding 4 a, 5 a rough surface of inner surface of recess for embedding 6 conductive layer for conduction 7 through hole 8, 9 thin metal layer 11, 12 photoresist layer 89 metal Thin layer

Claims (10)

[Claims] A buried recess formed on one surface of the insulating layer; a buried conductive layer formed in the buried recess; a through hole reaching the buried conductive layer from the other surface of the insulating layer; A wiring substrate, comprising: a conductive layer for conduction buried in a through hole. 2. The wiring board according to claim 1, wherein said buried conductive layer is formed by plating. 3. The buried conductive layer is formed by an electroless plating method,
3. The wiring board according to claim 1, wherein the wiring board is formed on the electroless plating layer by an electrolytic plating method. 4. The wiring board according to claim 1, wherein the buried conductive layer is formed substantially flush with an upper surface of the insulating layer. 5. The wiring substrate according to claim 1, wherein said buried conductive layer is formed of copper. 6. The wiring board according to claim 1, wherein said insulating layer is a wholly aromatic polyester liquid crystal polymer film. 7. The wiring board according to claim 1, wherein the inner wall surface of the recess for embedding is formed with a rough surface. 8. The method according to claim 1, wherein the conductive layer for conduction is formed by an electroless plating method, an electrolytic plating method on the electroless plating layer, or a method of applying a conductive paste. The wiring board according to claim 1. 9. A step of forming a photoresist layer on the surface of the insulating layer, a step of etching the insulating layer exposed from the photoresist layer to form a recess for embedding, and embedding a conductive layer in the recess for embedding. A method of manufacturing a wiring board, comprising: a step of forming a through hole reaching the buried conductive layer from the back surface of the insulating layer; and a step of forming a conductive layer for conduction in the through hole. 10. A step of roughening the inner surface of the embedding recess formed on the surface of the insulating layer by wet blasting or liquid honing, and electroless plating or electroless plating on the roughened surface. Forming a conductive layer on the layer by an electrolytic plating method.
The method for manufacturing the wiring board according to the above.