JPH1079561A - Wiring board and forming method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable wiring to be lessened in transmission loss through its routing part and enhanced in adhesive strength by a method, wherein the surface of an insulating resin layer where a thin-film resistor is formed is set rougher than that of the insulating resin layer where a wiring is formed. SOLUTION: An insulating photosensitive resin layer 13 is formed on a base 11, then exposed to light, and developed into a shape conforming to a wiring board. Then, the insulating photosensitive resin layer 13 is exposed to light through a mask 21. This exposure is carried out under such conditions that the thin-film resistor forming a predetermined regions 13b of the insulating photosensitive resin layer 13 is further improved in resistance with respect to a roughening process than the other region of the photosensitive resin layer 13. Then, the photosensitive resin layer 13 is subjected to a roughening process, so as to improve a wiring in adhesion to it. By this setup, the thin-film resistor forming predetermined region 13b of the insulating photosensitive resin layer 13 can be made smaller than the other region of the photosensitive resin layer 13, so that the region 13b is more slowly roughened than the other region, and thus the surface of the thin-film resistor forming predetermined region 13b is roughened less.

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 an insulating resin layer and having a wiring and a thin-film resistor on the insulating resin layer, and a method suitable for forming the wiring board. It is about.

[0002]

2. Description of the Related Art There is a wiring board formed by a build-up method as a wiring board compatible with high-density mounting (for example, Document I: Electronic Materials, October 1995 (Industrial Research Council), p.84).
). This type of wiring board forming method is described in, for example,
It is described on page 6. This forming method includes a step of forming an insulative photosensitive resin layer on a base (double-sided copper-clad laminate or lower wiring), and a step of exposing and developing the photosensitive resin layer to have a shape conforming to a wiring board. And a step of roughening the surface of the exposed and developed photosensitive resin layer, and a step of forming wiring components such as copper wiring on the roughened photosensitive resin layer. . Here, the roughening treatment was performed for the purpose of roughening the surface of the resin layer in order to secure the adhesion strength of the copper wiring to the photosensitive resin layer. In the field of this type of wiring board, a thin film resistor is preliminarily formed on the resin layer together with the copper wiring. This is because a wiring board that can be mounted at a high density and has a circuit function can be realized. In that case, a thin film resistor is formed by a suitable method on a predetermined portion of the resin layer on which the roughening process has been completed.

[0003]

However, it has been clarified by the inventor of the present application that the above-mentioned prior art has the following problems.

As described above, the surface of the resin layer is roughened in order to increase the adhesion of the copper wiring to the photosensitive resin layer. This roughening is generally performed to such an extent that irregularities of 1 to 2 μm (maximum roughness of approximately 5 μm) can be formed on the surface of the resin layer. Then, in the prior art, the thin film resistor is also formed on the resin layer surface thus roughened.
However, when a thin film resistor is formed on the surface of the resin layer having such irregularities, the resistance value of the thin film resistor hardly becomes a desired value due to the influence of the irregularities. Particularly, when a high-resistance thin-film resistor is manufactured, the width of the thin-film resistor is reduced or the thickness thereof is reduced, so that the above-mentioned unevenness is affected. Therefore, the resistance value of the thin-film resistor is less likely to be a desired value. . Therefore, a step of separately adjusting the width and the film thickness of the thin film resistor using a laser or the like to obtain a thin film resistor having a desired resistance value is required. Therefore, in the related art, there are problems that the number of processes increases, the manufacturing yield decreases, and the cost of the wiring board increases. Further, when the degree of the roughening is made small (weak), there arises a problem that the copper wiring is peeled off from the resin layer. To avoid these,
It is also conceivable to separately form a resin layer on the roughened resin layer on the region where the thin film resistor is to be formed. However, even if it does so, the improvement of the reproducibility of the resistance value cannot be obtained so much, and the problem that the number of manufacturing steps is further increased occurs.

It is desired to provide a wiring board having a wiring and a thin-film resistor on an insulating resin layer and having a structure in which a desired resistance value is easily obtained, and a method for easily forming such a wiring board. It is.

[0006]

According to the invention of the wiring board of the present application, a wiring board having an insulating resin layer and wiring and a thin film resistor provided on the insulating resin layer is provided with an insulating substrate. The surface roughness of the portion where the thin film resistor is formed in the conductive resin layer is smaller than the surface roughness of the portion where the wiring is formed in the insulating resin layer (the flatness is improved). ).

According to the wiring board of the present invention, since the thin film resistor is provided on the base portion having a small surface roughness,
Compared with the case where it is not the case, the thin film resistor has a uniform film thickness and a desired shape of the edge.

In practicing the present invention, the surface roughness of the region of the insulating resin layer where the wiring routing portion is formed is compared with the surface roughness of the region where the external component connection portion of the wiring is formed. It is preferable to keep it small. In this way, even when handling high-speed signals, it is possible to reduce the deterioration of the signal transmission loss in the routing of the wiring, and to secure the adhesion strength of the external component connection part in the wiring, for example, the wiring soldering part to the resin layer. The obtained wiring board is obtained.

Further, according to the method of forming a wiring board of the present invention, a step of forming an insulating photosensitive resin layer on a base, and exposing and exposing the photosensitive resin layer to a shape suitable for the wiring board.
Developing, roughening the exposed and developed photosensitive resin layer surface, and forming wiring components (for example, wiring, thin film resistor, etc.) on the roughened photosensitive resin layer. In the method of forming a wiring board including the step of, before the roughening step, for a partial region of the photosensitive resin layer, to make the resistance of the partial region to the roughening step different from other regions It is characterized in that selective exposure is performed. However, the present invention includes a case where a plurality of partial regions are exposed under different exposure conditions.

According to the method of forming a wiring board of the present invention,
After the roughening step, regions having at least two types of surface roughness are formed in the resin layer. That is, regions having at least two types of surface roughness are formed in the resin layer in one roughening step. In the present invention, when a plurality of partial regions are exposed under different exposure conditions, regions having at least three types of surface roughness are formed in the resin layer in one roughening step. Therefore, the method of the present invention can be used, for example, as a technique for controlling the surface roughness of a region where a thin film resistor is to be formed in a resin layer or the surface roughness of a region where a wiring is to be formed in a resin layer. Specifically, it can be used as the following method.

That is, a step of forming an insulating photosensitive resin layer on a base, a step of exposing and developing the photosensitive resin layer so as to have a shape conforming to a wiring board, and a step of exposing and developing the photosensitive resin layer In a method for forming a wiring board including a step of roughening a resin layer surface and a step of forming a wiring and a thin film resistor on the roughened photosensitive resin layer, before the roughening step, A method including a step of selectively exposing the photosensitive resin layer to a region where a thin-film resistor is to be formed in the photosensitive resin layer so that the resistance to the roughening step is higher than that of other regions. According to this specific method for forming a wiring board, after the roughening step is completed, the degree of roughening of the region where the thin-film resistor is to be formed in the insulating photosensitive resin layer is smaller than in other regions. Therefore, a portion having a low surface roughness as desired can be easily formed. A thin film resistor formed on a region having a small surface roughness has a more uniform thickness than that formed on a region having a large surface roughness. Further, the patterning of the thin film resistor formed on the region having the small surface roughness can be more accurately performed than the patterning of the thin film resistor formed on the region having the large surface roughness.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a wiring board and a method of forming a wiring board according to an embodiment of the present invention; The drawings used in the description merely show the dimensions, shapes, and arrangements of the components so that the present invention can be understood. Also, in each of the drawings, the same components are denoted by the same reference numerals, and redundant description thereof may be omitted.

1. First Embodiment An example in which the present invention is applied to a wiring board forming method called a build-up method will be described. 1 to 3 are manufacturing process diagrams for explanation thereof. The finished wiring board in these figures is shown in FIG. In addition, all the figures except the plan view in FIG. 3 are shown by cross-sectional views.

First, an insulating photosensitive resin layer 1 is formed on a base 11.
3 (FIG. 1A). Here, the underlayer 11 can be various types such as a core substrate or a wiring substrate intermediate in which the lower layer wiring is already formed. Insulating photosensitive resin layer 13
Is formed by applying a negative-type and alkali-developable photosensitive epoxy resin on the base 11, followed by drying.

Next, the insulating photosensitive resin layer 13 is exposed and developed so as to have a shape conforming to the wiring board. Here, an example in which a via hole is formed in the resin layer 13 is considered.
Therefore, after covering the resin layer 13 with the mask 15 that can shield the via-hole formation region 13a of the insulating photosensitive resin layer 13 and expose other regions, the insulating photosensitive resin layer 13 is removed. Exposure is performed with ultraviolet rays (UV) 17 (FIG. 1B).

The exposed sample is developed using a sodium carbonate solution or the like. Then, the unexposed portion of the insulating photosensitive resin layer 13 is removed to form a via hole 19 (FIG. 1C).

Next, the resin layer 13 is covered with a mask 21 capable of exposing an area 13b of the insulating photosensitive resin layer 13 where a thin film resistor is to be formed and shielding other areas (FIG. 2A). ). However, it is preferable that the mask 21 be designed so that an area slightly larger than the original thin film resistor forming area 13b can be exposed. In this case, even if there is a mask shift at the time of exposure, deformation of the base due to elongation or shrinkage of the substrate occurring during the manufacturing process, and a patterning shift of the thin film for forming the thin film resistor performed later, the thin film resistor can be used. Can be formed in the thin film resistor formation scheduled area 13b as planned. Next, the insulating photosensitive resin layer 13 is exposed through a mask 21 (also FIG. 2A). This exposure is performed under such a condition that the resistance of the region 13b where the thin film resistor is to be formed of the insulating photosensitive resin layer 13 to the roughening step is improved as compared with the other regions. More specifically, even after the roughening process, the surface roughness of the thin film resistor formation scheduled region 13b is maintained in a state where the surface roughness is small enough not to substantially cause a variation in the resistance value of the thin film resistor. Exposure conditions that can provide the roughening treatment resistance to the region 13b. Here, the region 1 where the thin film resistor is to be formed in the insulating resin layer 13 is to be formed.
3b, a sufficient exposure dose (for example, several thousand mJ / cm) to substantially completely crosslink the unreacted photosensitive group.
² ) Exposure. The chemical resistance and the like of the resin layer portion 13b that has been sufficiently exposed as described above are improved as compared with the portion that does not. For example, the resistance during the treatment with an alkaline treatment liquid in the subsequent roughening treatment is improved.

Next, in order to improve the adhesion of the wiring to be formed later to the insulating photosensitive resin layer 13, the sample is subjected to a roughening treatment. Here, the surface is roughened by swelling the insulative photosensitive resin layer 13 with an alkaline treatment liquid and etching with an etchant containing permanganate. In addition, a neutralization treatment is also performed on the used chemicals. In this roughening process, the thin-film resistor forming region 13b in the insulating photosensitive resin layer 13, that is, the previously selectively exposed region is less likely to swell than other regions, so that the progress of the roughening is slowed down. Therefore, after the roughening treatment,
The surface roughness of the region 13b where the thin-film resistor is to be formed in the insulating photosensitive resin layer 13 can be made smaller (that is, the flatness is better) as compared with other regions. On the other hand, the region 13b of the insulating photosensitive resin layer 13 where the thin film resistor is to be formed is formed.
Since the regions other than the region 13 swell with the alkaline processing liquid more than the region 13b, the degree of roughening is also increased.
This is a region having a surface roughness sufficient to secure a desired adhesion of the wiring to be formed later to the resin layer 13. FIG. 2B shows these states. In FIG. 2B, a region I is a region where the surface roughness is small and a thin film resistor is formed later, and a region II is a region where the surface roughness is large and a wiring is formed later.

Insulating photosensitive resin layer 13 after roughening treatment
The thin film 23 for forming a thin film resistor is formed thereon by a suitable film forming method.
To form Further, a thin film 25 for forming a wiring is formed on the thin film 23 by a suitable film forming method (FIG. 2C).
The method for forming the thin film 23 is not particularly limited, and may be any suitable method such as an electroless plating method and a vapor deposition method. The method for forming the thin film 25 is not particularly limited, and may be, for example, an electrolytic plating method,
Any suitable method such as a vapor deposition method can be used. Also, the constituent material of the thin film 23 can be any suitable material. For example, Ni (nickel) -P (phosphorus), Ni-W (tungsten) -P,
Ni-Fe (iron) -P, Ni-B (boron) or the like can be used as a constituent material of the thin film 23 for forming a thin-film resistor. As a constituent material of the thin film 25, for example, copper (C
u) is used.

Next, each of the thin film 23 for forming the thin film resistor and the thin film 25 for forming the wiring is patterned into a predetermined shape. This can be performed by, for example, a known lithography technique and etching technique. Thereby, the thin film resistor 23a and the wiring 25a are formed (FIG. 3). As can be seen from FIG. 3, the thin film resistor 23a is formed on a region of the insulating resin layer 13 where the surface roughness is smaller than other regions.

Here, a thin film 2 for forming a thin film resistor is used.
3 and a thin film 25 for forming a wiring are sequentially formed, and an example of patterning them is described. However, after forming a thin film 23 for forming a thin film resistor, this patterning is performed first, and then a thin film for forming a wiring is formed. 25 may be formed and patterned.

Next, in order to stabilize the wiring substrate, the entire surface of the insulating photosensitive resin layer 13 is exposed with an exposure amount sufficient to cause the unreacted photosensitive groups to react. After that, if a further upper wiring is to be formed, FIG.
3 are repeated.

2. Second Embodiment In the first embodiment, the insulating photosensitive resin layer includes:
The example in which two types of regions having different resistances to the roughening process are generated by the selective exposure has been described. However, according to the present invention, three types of regions having different resistances to the roughening treatment can be formed in the insulating photosensitive resin layer by selective exposure. Here, the resistance to the roughening process is different.
An example in which types of regions are generated by selective exposure will be described. This description will be made with reference to FIGS.

First, in the first embodiment, FIG.
(A) to (C), an insulating photosensitive resin layer 13 is formed on a base 11, and the resin layer 1
A via hole 19 is formed in 3 (FIG. 4A).

Next, as in the first embodiment, the insulating photosensitive resin layer 13 is covered with a mask 21 and the insulating photosensitive resin layer 13 is exposed through the mask 21 (FIG. 4B). ). Here, as in the first embodiment, a sufficient exposure amount (for example, several thousand mJ / cm) enough to substantially completely cross-link unreacted photosensitive groups in the thin-film resistor formation scheduled region 13b of the insulating resin layer 13 is obtained. ² ) Exposure.

Next, a mask 3 that can shield light in the connection area of the insulating photosensitive resin layer 13 where wiring is to be formed and in which connection parts such as external parts (for example, wiring parts to be soldered or the like) are to be formed.
1 to cover the resin layer 13, and then expose the insulating photosensitive resin layer 13 through the mask 31 (FIG. 4).
(C)). The exposure amount at this time is a predetermined exposure amount that is smaller than the exposure amount at the time of exposing the thin film resistor formation scheduled area 13b. The predetermined exposure amount is such that the surface is roughened in a later roughening process to secure the necessary minimum adhesion of the wiring formed later to the insulating photosensitive resin layer 13. It is an exposure amount that can provide the resin layer 13 with oxidation resistance. The area of the light-shielding portion of the mask 31 used for this exposure is preferably slightly larger than the design area of the wiring portion to be soldered or the like. In such a case, even if there is a mask shift at the time of exposure, a deformation of a base caused by elongation or shrinkage of a substrate occurring during a manufacturing process, or a patterning shift of a thin film for forming a wiring to be performed later, this wiring portion is determined by a predetermined amount. This is because it can be formed as expected in the region of the surface roughness.

Next, this sample is subjected to a roughening treatment in the same procedure as described in the first embodiment. In this roughening treatment, the thin-film resistor forming region 13b in the insulating photosensitive resin layer 13 is most difficult to be roughened. Next, the portion that was shielded when exposed through the mask 31 is hardly roughened. Since the light-shielded portion is hardly roughened when exposed through the mask 21 and the light-shielded portion is hardly roughened even when exposed through the mask 31, the insulating photosensitive resin layer 13 has a rough surface. Three types of regions with different degrees occur. FIG. 5A shows these states.
In FIG. 5A, a region I is a region where the surface roughness is small and a thin film resistor is to be formed later, and a region II is a region where the surface roughness is large and the wiring is later soldered or the like. III is a region where the surface roughness is medium (surface roughness that ensures the minimum required adhesion of the wiring) and, for example, a region where the wiring routing portion is formed later It is.

On the roughened insulating photosensitive resin layer, a thin film 23 for forming a thin film resistor and a thin film 25 for forming a wiring are formed by the same procedure as that described in the first embodiment. Then, the thin film resistor 23a and the wiring 25a are respectively formed by patterning them (FIG. 5C). As can be seen from FIG. 5C, the thin film resistor 23a is formed on the region of the insulating resin layer 13 where the surface roughness is the smallest, and the wiring 2
3a is formed on a region of the insulating resin layer 13 where the surface roughness is the highest, and the leading portion of the wiring 23a is formed of the insulating resin layer 1.
3 is formed on a region where the surface roughness is medium.

Next, in order to stabilize the wiring substrate, the insulating photosensitive resin layer 13 is exposed to light at an exposure amount sufficient to cause the unreacted photosensitive groups to react. Thereafter, if a further upper layer wiring is to be formed, the steps described with reference to FIGS. 4A to 5 are repeated.

According to the wiring forming method of the second embodiment, the wiring 25a is formed on the resin layer having a medium surface roughness.
Can be easily formed. Therefore, even when a high-speed signal is handled, a wiring board with less transmission loss at the wiring routing portion than in the related art can be obtained.

Although some embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, an example is described in which a negative-type and alkali-developable epoxy resin layer is used as the insulating photosensitive resin layer. However, the photosensitive resin layer can adjust the resistance of the roughening step by adjusting the exposure amount If so, other things may be used. Further, the invention according to the method for forming a wiring board is not limited to the formation of a wiring board having a thin film resistor, and it is necessary to form a region having a different surface roughness in a part of an insulating photosensitive resin layer. Widely applicable to the formation of

[0032]

As is apparent from the above description, according to the invention of the wiring board of the present application, the wiring board including the insulating resin layer, the wiring and the thin film resistor provided on the insulating resin layer In (2), the surface roughness of the portion of the insulating resin layer where the thin film resistor is formed is smaller than the surface roughness of the portion where the wiring is formed in the insulating resin layer (the flatness is low). Better). Therefore, a wiring board having a thin film resistor having a uniform thickness and a desired edge shape can be obtained. Further, in the invention of this wiring board, in the configuration in which the surface roughness of the region where the wiring routing portion is formed in the resin layer is smaller than that of the portion where the external component connection portion of the wiring is formed, the wiring routing portion may be used. Thus, a wiring board is obtained in which the required adhesion strength is secured while reducing the signal transmission loss.

Further, according to the method for forming a wiring board of the present invention, a step of forming an insulating photosensitive resin layer on a base, and a step of exposing the photosensitive resin layer to a shape suitable for the wiring board.
A method of forming a wiring board, comprising: a step of developing; a step of roughening the surface of the exposed and developed photosensitive resin layer; and a step of forming wiring components on the roughened photosensitive resin layer. In the method, prior to the roughening step, selective exposure is performed on a partial region of the photosensitive resin layer so that the partial region has different resistance to the roughening step from other regions. Therefore, at least two resin layers are formed in one roughening step.
Regions having different types of surface roughness are formed. Therefore, according to the formation method of the present invention, the surface roughness of the insulating resin layer in the region where the thin film resistor is to be formed and the surface roughness of the region where the wiring is to be formed in the resin layer can be easily controlled. Therefore, since the thin film resistor can be formed on the insulating resin layer portion having a flat surface roughness, the formed thin film resistor has a smaller variation in resistance value than before. Therefore, it is possible to eliminate the need for trimming the resistance value, thereby simplifying the manufacturing process of the wiring board and reducing the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment, illustrating a manufacturing process of a wiring board;

FIG. 2 is an explanatory diagram of the first embodiment, and is a manufacturing process diagram following the FIG. 1 of the wiring board;

FIG. 3 is an explanatory diagram of the first embodiment, and is a manufacturing process diagram subsequent to FIG. 2 of the wiring board;

FIG. 4 is an explanatory diagram of the second embodiment, and is a view illustrating a manufacturing process of a wiring board;

FIG. 5 is an explanatory diagram of the second embodiment, and is a manufacturing process diagram following FIG. 4 of the wiring board;

[Explanation of symbols]

 11: Base 13: Insulating photosensitive resin layer 13a: Via hole formation planned area 13b: Thin film resistor formation planned area 15: Mask 17: Ultraviolet light 19: Via hole 21: Mask 23: Thin film for forming a thin film resistor 25: Wiring Forming thin film 23a: Thin film resistor 25a: Wiring 31: Mask I: Area with low surface roughness II: Area with high surface roughness III: Area with medium surface roughness

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Ho Nakashiki 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. Circuit Corporation

Claims (9)

[Claims] 1. A wiring board comprising an insulating resin layer, and a wiring and a thin film resistor provided on the insulating resin layer, a surface of a region of the insulating resin layer where the thin film resistor is formed. A wiring substrate, wherein the roughness is smaller than the surface roughness of a region of the insulating resin layer where the wiring is formed. 2. The wiring board according to claim 1, wherein the surface roughness of a region of the insulating resin layer where the thin-film resistor is formed causes a variation in the resistance value of the thin-film resistor. A wiring board characterized in that the wiring board is reduced to such an extent that the wiring board is not substantially reduced. 3. The wiring board according to claim 1, wherein the surface roughness of a region of the insulating resin layer where a wiring routing portion is formed is a region where an external component connection portion of the wiring is formed. A wiring board characterized in that the surface roughness is smaller than the surface roughness of the wiring board. 4. The wiring board according to claim 1, wherein the wiring board has roughened the surface roughness of the insulating resin layer to such an extent that the adhesive strength of the wiring to the insulating resin layer can be secured. A wiring board, wherein the thickness of the thin-film resistor is reduced to such an extent that the resistance value accuracy of the thin-film resistor is reduced due to the unevenness. 5. The wiring board according to claim 1, wherein the insulating resin layer is an insulating resin layer formed by processing a negative photosensitive resin. 6. A step of forming an insulative photosensitive resin layer on a lower ground, a step of exposing and developing the photosensitive resin layer so as to have a shape conforming to a wiring board, and a step of exposing and developing the photosensitive resin layer. A method for forming a wiring board, comprising: a step of roughening a surface of a resin layer; and a step of forming wiring components on the roughened photosensitive resin layer. A method for forming a wiring substrate, wherein a selective exposure is performed on a partial region of the resin layer so as to make the partial region resistant to the roughening process different from other regions. (Includes a case where a partial region is exposed under different exposure conditions.) 7. A step of forming an insulative photosensitive resin layer on an underlayer, a step of exposing and developing the photosensitive resin layer to have a shape conforming to a wiring substrate, and a step of exposing and developing the photosensitive resin layer. In a method for forming a wiring board, comprising: a step of roughening a resin layer surface; and a step of forming a wiring and a thin-film resistor on the roughened photosensitive resin layer, wherein before the roughening step, A method for forming a wiring board, comprising: selectively exposing the photosensitive resin layer to a region where a thin-film resistor is to be formed in the photosensitive resin layer so that the resistance to the roughening step is higher than in other regions. . 8. The method for forming a wiring board according to claim 7, wherein the selective exposure is performed such that the surface roughness of the thin film resistor formation scheduled area is equal to the resistance of the thin film resistor even after the roughening process. A method for forming a wiring substrate, comprising: performing exposure to impart the roughening treatment resistance to the formation scheduled region so as to be maintained in a small state that does not substantially cause a variation in value. 9. The method for forming a wiring board according to claim 6, wherein a negative photosensitive resin is used as the insulating photosensitive resin, and the resistance is the photo-crosslinking with the negative photosensitive resin. A method for forming a wiring board, wherein the reaction is provided by adjusting the amount of exposure to the resin.