JP2008135570A - Method of manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently manufacturing a wiring board having wiring layers different in wiring thickness control levels on two faces. <P>SOLUTION: Plating feeding layers are formed on insulating layers 3 on both faces of an insulating substrate 1 and resist films 5 are laminated on them at uniform thickness. The respective resist films 5 are patterned and the plating feeding layers are exposed to openings. The wiring layers 6a exceeding thickness of the resist films 5 are formed on one exposed feeding layer and the wiring layers 6b smaller than thickness of the resist film 5 are formed on the other feeding layer by deposition of a wiring material by electrolytic plating. Part of the wiring layers 6a on one feeding layer is removed to thickness similar to the resist film 5. The wiring layers 6a are made into the same thickness as the resist films 5 and the resist films 5 on both faces and the feeding layers below them are removed. Thus, the wiring layers 6a and 6b are formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a wiring board, and more particularly to a method for manufacturing a wiring board including a wiring forming process using a film resist.

  The electrical characteristics required for wiring boards are becoming stricter year by year, and it is indispensable to produce wiring thicknesses that have a great influence on the electrical characteristics as designed and to reduce variations between products. . On the other hand, in designing a wiring board, wirings having different widths are required in one product in order to obtain predetermined electrical characteristics. In the method of manufacturing a wiring board, in order to improve productivity, processing is performed with a large work in which a plurality of individual products are arranged until the final stage. Since these designs and processes reduce the uniformity of individual products in one substrate, it causes an increase in the variation in plating thickness for forming the wiring.

  In the formation of the wiring on the wiring substrate, the wiring plating is usually formed lower than the thickness of the dry film resist (DFR) film for forming the wiring pattern. In this case, variations in wiring thickness for each product are likely to occur. On the other hand, by forming plating with protrusions protruding from the surface of the DFR that can be supplied with a controlled uniform thickness, and removing the protrusions by polishing or etching, the wiring thickness can be reduced. A technique for making it uniform has been proposed.

  A conventional technique for adjusting the wiring thickness to the designed thickness by polishing or etching will be described with reference to FIG.

  In FIG. 4, a DFR 42 is coated on a substrate 41 of a wiring board, the DFR 42 is exposed and developed by photolithography to form a groove pattern 43, and copper 44 as a wiring material is formed in the pattern groove 43 by electrolytic copper plating. The copper 44 is formed so as to be thicker than the final wiring thickness and to protrude from the surface of the DFR 42 by a thickness t, for example. Thereafter, the copper plating protrusions protruding from the surface of the DFR 42 are polished or processed by etching to reduce the wiring thickness to the design thickness. For polishing, a buff, a belt sander or the like is used.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 06-053660), after plating a resist, the plating performed by the semi-additive method is deposited to be thicker than the thickness of the resist, and then the plating protrusions are removed and planarized by polishing. Is described.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2002-0776620), after the resist patterning, plating performed by the semi-additive method is deposited to be thicker than the resist thickness, and then the thickness of the plating is polished by using a stopper metal disposed on the resist. It is described that the same.

  In Patent Document 3 (Japanese Patent Application Laid-Open No. 2003-258410), after patterning a resist, the plating is deposited to be thicker than the resist thickness by a semi-additive method, and then the plating protrusions are removed by mechanical polishing, and the resist thickness is adjusted. As a reference, it is described that the height of the wiring is made uniform.

  In Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-277258), after patterning a plating resist, a plating seed layer is formed on the entire surface including the resist, plating is deposited higher than the resist, and then plated by physical or chemical polishing. Is exposed to expose the resist, and then the resist is peeled off.

Japanese Patent Laid-Open No. 06-053660 Japanese Patent Laid-Open No. 2002-076620 JP 2003-258410 A JP 2005-277258 A

  It is very difficult to process only the wiring material to the same thickness as the DFR film without processing a DFR that is very easy to process compared to a wiring such as copper (Cu). For example, in the case of mechanical polishing, since the processing speed of DFR is much higher than that of plated metal, it is very difficult to complete the processing along the surface using the DFR film as a processing stop layer.

  Therefore, the inventors of the present application have made a method of making the wiring thickness uniform based on the thickness of the DFR by forming a wiring by plating higher than the DFR and then polishing using a resin pad and acid-based slurry. Was proposed (Japanese Patent Application No. 2006-036530).

  Each surface of the wiring board is usually connected to a separate electric / electronic component (for example, one side is connected to a semiconductor chip and the other side is connected to another mounting board). Therefore, it is rare that the same wiring thickness control level is required on both sides. However, a resin wiring board is usually manufactured by applying a simultaneous process one layer on each side of a central core board. Therefore, even when a high degree of control of the wiring thickness is necessary only for the wiring layer on one side, the wiring is usually formed with the same plating thickness using the DFR having the same thickness on both sides. Therefore, both in the case of the prior art described above and in the case of the new technique proposed by the inventors, an additional process such as polishing occurs for the wiring layer that does not require a very high wiring thickness control. This is a cause of reduced productivity and increased manufacturing costs.

  An object of the present invention is to solve such a problem and to provide a method that enables efficient production of a wiring board having wiring layers having different wiring thickness control levels on two surfaces. is there.

A wiring board manufacturing method provided by the present invention is a method for manufacturing a wiring board by laminating a predetermined number of wiring layers on both sides of an insulating substrate (core substrate) with an insulating layer interposed therebetween, Formation,
Forming a plating power supply layer on the insulating layers on both sides, and laminating a resist film thereon with a uniform thickness;
Patterning each resist film and exposing the power feeding layer for plating in the opening formed thereby,
A step of depositing a wiring material by electrolytic plating and forming a wiring layer exceeding the thickness of the resist film on the exposed one power supply layer and forming a wiring layer lower than the thickness of the resist film on the other power supply layer;
Removing a part of the wiring layer on one power feeding layer to the same thickness as the resist film, and making the wiring layer the same thickness as the resist film;
Removing the resist film on both sides and the plating power feeding layer underneath,
It is characterized by performing by.

  In one aspect of the wiring board manufacturing method of the present invention, in the step of laminating a resist film, a thin resist film is laminated on one power feeding layer, and a thick resist film is laminated on the other power feeding layer. Thus, a wiring layer exceeding the thickness of the resist film can be formed on one power supply layer, and a wiring layer lower than the thickness of the resist film can be formed on the other power supply layer. In this case, the height of the wiring material deposited on the power feeding layers on the two surfaces may be the same or different.

  In another aspect of the wiring board manufacturing method of the present invention, in the step of forming the wiring layer by depositing the wiring material by electrolytic plating, the wiring material is deposited thickly on one power feeding layer, and the other power feeding layer By depositing a thin film on the top, a wiring layer exceeding the thickness of the resist film can be formed on one power supply layer, and a wiring layer lower than the thickness of the resist film can be formed on the other power supply layer. The wiring materials having different thicknesses can be deposited on the two surfaces by subjecting each surface to electrolytic plating treatment under different conditions. In this case, the thicknesses of the resist films on the two surfaces may be the same or different.

  According to the present invention, it is possible to efficiently manufacture a wiring board having wiring layers having different wiring thickness control levels on the two surfaces.

The basic concept of the present invention will be described with reference to FIGS. 1 (a) to 1 (c).
An important feature of the method for manufacturing a wiring board of the present invention is that, in the step of forming a wiring layer by electrolytic plating using a resist film as a mask, the wiring layer exceeds the thickness of the resist film on one side, and the resist film on the other side. It is to form a wiring layer lower than the thickness. FIG. 1A shows an example of a wiring substrate being manufactured in which a wiring layer 6a exceeding the thickness of the resist film 5 is formed on one side and a wiring layer 6b lower than the thickness of the resist film 5 is formed on the opposite side. In this figure, wiring layers 6a and 6b are formed on a resist film 5 on a seed layer (not shown) serving as a plating power supply layer on the insulating layer 3 on each surface of the core substrate 1 by using a semi-additive method. It is formed by the electroplating which uses as a mask. The upper part of the wiring as formed by the deposition of the wiring material by electrolytic plating is somewhat rounded. In FIG. 1 (a) (and the figure referred to below), this is shown by being formed by electrolytic plating. An exaggerated round is added to the top of the wiring.

  The wiring layer 6a on the upper surface of the wiring board that requires a high degree of thickness control has a portion protruding beyond the thickness of the insulating film 3, for example, even if the deposition height of the wiring material after electrolytic plating varies. By removing by polishing, the thickness is adjusted to the controlled thickness of the insulating film 3 as shown in FIG. The wiring layer 6b on the lower surface of the wiring board that does not require much thickness control is used as it is without being subjected to a treatment such as polishing.

  Thereafter, as shown in FIG. 1C, the insulating films 3 on both sides and the seed layer (not shown) thereunder are removed to complete the formation of the wiring layers 6a and 6b.

  In order to form a wiring layer exceeding the thickness of the resist film on one side of the substrate and a wiring layer lower than the thickness of the resist film on the other side, it is necessary to form one resist film thin and the other resist film thick. It is valid. It is also effective to deposit the wiring material thinly on one side of the substrate and thickly on the other side.

  In the method of the present invention, it is preferable to use a dry film resist (DFR) supplied with a controlled uniform thickness as the resist film. However, in some cases, a resist film made of a material other than DFR may be used.

  As a wiring material, the material used with a normal wiring board can be used. A typical wiring material is copper.

  Since the thickness of one wiring layer is made equal to the thickness of the resist film, general methods such as polishing and etching can be used to remove a part of the wiring layer. Preferably, the present invention preferentially removes the wiring material protruding beyond the thickness of the resist film without damaging the resist film, and uniform wiring thickness based on the resist film thickness. It is a method that can be further polished. An example of such a method is chemical mechanical polishing (CMP) using a resin polishing pad.

  In such chemical mechanical polishing, it is preferable to use a polyester nonwoven fabric fiber impregnated with polyurethane or a polyurethane resin foam as a polishing pad. Thus, the pad material containing polyurethane has an air layer inside, which is advantageous in that the retention of the polishing slurry is improved.

As the polishing slurry, those having an organic acid such as acetic acid, citric acid, malic acid, tartaric acid, or a mixture thereof as a main component are suitable. As the abrasive grains, SiO ₂ powder, alumina powder, or a mixture thereof can be suitably used.

  A substrate on which wiring is formed according to the present invention is completed by forming a protective insulating layer covering the uppermost wiring layer and a pad exposed on the surface thereof. The completed wiring board can be connected to another electronic / electrical component such as a semiconductor chip or another mounting board.

The present invention will be described in more detail by way of examples, but the following examples are not intended to limit the present invention.
All the techniques themselves used in each step of the production method of the present invention are known and will not be described more than necessary. The material used in the present invention is not particularly limited, and materials used in ordinary wiring boards can be used in addition to those described in the following examples.

[Example 1]
As shown in FIG. 2 (a), copper is electrolessly plated on the entire surface of the insulating layer 21 (both holes 22 for connecting the upper and lower wiring layers) on both sides of the wiring substrate 20 in the manufacturing process. After a thin (Cu) seed layer (not shown) is formed, resist films 23a and 23b patterned for forming a wiring layer are formed. The resist films 23a and 23b can be formed by attaching a dry film resist (DFR) having a predetermined thickness on the seed layer on each surface and patterning it by a photolithography technique. The upper and lower DFRs have different thicknesses so that the upper resist film 23a is thicker than the lower resist film 23b.

  By electrolytic plating using a seed layer (not shown) exposed in the openings 24a and 24b of the resist films 23a and 23b as a power feeding layer, the resist film 23b exceeds the thickness of the thin resist film 23a on the upper surface and is thick on the lower surface. The copper (Cu) wiring materials 25a and 25b are deposited on the seed layer (not shown) (FIG. 2B). The heights of the wiring materials 25a and 25b on both sides may be the same.

  The portion of the wiring material protruding above the resist film 23a on the upper surface is removed by polishing, and the thickness is made equal to the thickness of the resist film 23a as shown in FIG. 2C to form the upper wiring layer 26a. To do. For example, the wiring material protruding from the resist film 23a is damaged to the resist film 23a by chemical mechanical polishing using a polishing pad of polyester nonwoven fabric fiber impregnated with polyurethane and a polishing slurry of organic acid (for example, acetic acid) and alumina abrasive grains. Can be removed without giving.

  The resist films 23a and 23b on both sides are peeled and removed, and then the seed layer (not shown) is removed by etching to complete the formation of the upper wiring layer 26a and the lower wiring layer 26b (FIG. 2D). ). The thickness of the wiring layer 26a on the upper surface is reduced during the etching for removing the seed layer, but the thickness corresponds to the thickness of the seed layer under the resist film 23a. The thickness of the wiring layer 26a is the same as the thickness of the resist film 23a. The wiring layer 26b on the lower surface also decreases during the etching for removing the seed layer, but inherits the shape of the wiring material 25b deposited by electrolytic plating.

[Example 2]
As shown in FIG. 3A, copper (Cu) is formed by electroless plating on the entire surface of the insulating layer 31 (both upper and lower wiring layer connection holes 32 are formed) on both sides of the wiring substrate 30 in the manufacturing process. After forming a thin seed layer (not shown), resist films 33a and 33b patterned for forming a wiring layer are formed using DFR as in the first embodiment. The upper and lower resist films 33a and 33b may have the same thickness.

  Copper (Cu) wiring materials 35a and 35b are formed on the seed layer (not shown) by electrolytic plating using a seed layer (not shown) exposed in the openings 34a and 34b of the resist films 33a and 33b as a power feeding layer. Is deposited (FIG. 3B). The height at which the wiring material 35a on the upper surface and the wiring material 35b on the lower surface are deposited changes the plating conditions (for example, by changing the current density), and the upper wiring material 35a protrudes beyond the thickness of the resist film 33a. The wiring material 35b remains in the opening 34b of the resist film 33b.

  By polishing in the same manner as in Example 1, the wiring material in the portion protruding above the resist film 33a on the upper surface was removed, and the thickness was made equal to the thickness of the resist film 33a as shown in FIG. A wiring layer 36a on the upper surface is formed.

  The resist films 33a and 33b on both sides are peeled and removed, and then the seed layer (not shown) is removed by etching to complete the formation of the upper wiring layer 36a and the lower wiring layer 36b (FIG. 2D). ). Also in this example, the thickness of the wiring layer 36a on the upper surface decreases during the etching for removing the seed layer, but this amount corresponds to the thickness of the seed layer under the resist film 33a. The thickness of the wiring layer 36a thus formed is the same as the thickness of the resist film 33a. The wiring layer 36b on the lower surface also decreases during the etching for removing the seed layer, but takes over the shape of the wiring material 35b deposited by electrolytic plating.

It is a figure explaining the basic concept of this invention. FIG. 5 is a diagram illustrating a process of Example 1. 6 is a diagram illustrating a process of Example 2. FIG. It is a figure explaining the prior art which adjusts wiring thickness.

Explanation of symbols

1 Core substrate 3 Insulating layer 5 Resist film 6a, 6b Wiring layer 20, 30 Wiring substrate 21, 31 Insulating layer 23a, 23b, 33a, 33b Resist film 25a, 25b, 35a, 35b Wiring material 26a, 26b, 36a, 36b Wiring layer

Claims (8)

A method of manufacturing a wiring board by sandwiching a predetermined number of wiring layers on both sides of an insulating substrate and sandwiching the insulating layers therebetween, and forming the wiring layer,
Forming a plating power supply layer on the insulating layers on both sides, and laminating a resist film thereon with a uniform thickness;
Patterning each resist film and exposing the power feeding layer for plating in the opening formed thereby,
A step of depositing a wiring material by electrolytic plating and forming a wiring layer exceeding the thickness of the resist film on the exposed one power supply layer and forming a wiring layer lower than the thickness of the resist film on the other power supply layer;
Removing a part of the wiring layer on one power feeding layer to the same thickness as the resist film, and making the wiring layer the same thickness as the resist film;
Removing the resist film on both sides and the plating power feeding layer underneath,
The wiring board manufacturing method characterized by performing by this.   The wiring board manufacturing method according to claim 1, wherein in the step of laminating the resist film, a thin resist film is laminated on one power supply layer and a thick resist film is laminated on the other power supply layer.   The wiring board manufacturing method according to claim 1, wherein in the step of forming the wiring layer by depositing the wiring material, the wiring material is deposited thickly on one power feeding layer and thinly deposited on the other power feeding layer.   The wiring board manufacturing method according to claim 1, wherein the resist film is formed using a dry film resist.   The wiring board manufacturing method according to any one of claims 1 to 4, wherein a part of the wiring layer on one power feeding layer is removed by chemical mechanical polishing.   The chemical mechanical polishing uses a polyester non-woven fabric fiber or polyurethane resin foam polishing pad impregnated with polyurethane, and a polishing slurry containing an organic acid and abrasive grains. The wiring board manufacturing method as described in 2.   The wiring substrate manufacturing method according to claim 6, wherein the organic acid is acetic acid, citric acid, malic acid, tartaric acid, or a mixture thereof. The wiring board manufacturing method according to claim 6, wherein the abrasive grains are SiO ₂ powder, alumina powder, or a mixture thereof.

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