JP2006060054A - Method for forming metal plate pattern and circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metal plate pattern which can form a metal pattern having a high aspect ratio by conducting the etching processes of multiple stages with the masking of metal. <P>SOLUTION: A silver plating layer (12) is formed to both surfaces or a single surface of a copper plate (10). A copper plating layer (14) is formed thereon thicker than the silver plating layer. The DFR is coated thereon and then it is patterned. The copper plating layer is etched using this resist pattern as a masking. A silver plating pattern (14a) is formed by etching the silver plating layer using the plating copper pattern (14a) as the masking. Moreover, after the half etching of the copper plate, coating of the positive resist, and exposure/development using this silver plating pattern (14a) as the masking; the half-etching is conducted again by protecting the positive resist under the silver plating pattern. Finally, a metal pattern (20) can be obtained by removing the resist and silver plating pattern used as the masking. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of forming a metal plate pattern such as a lead frame or a metal mask, or a wiring pattern on a printed circuit board, and more particularly, from a metal plate to a lead frame or metal using a pattern technology based on a subtractive method. The present invention relates to a method of forming a metal plate pattern such as a mask, or a method of forming a fine conductor pattern on an insulating substrate in manufacturing a printed circuit board.

  In the case of manufacturing a printed circuit board, the subtractive method is an inexpensive and simple method and has been most widely used conventionally. On the other hand, there is a disadvantage in that a finer conductor pattern on a circuit board can be obtained with the recent increase in density and miniaturization of semiconductor devices and various electronic devices.

In the prior art as a metal etching method for obtaining a high aspect ratio,
(1) There is a multistage etching method using a dry film resist (DFR) and a light-shielding ink layer as masking. In this method, a liquid positive resist is applied on a metal patterned by DFR and developed using a developer. According to this method, there is a possibility that the patterned DFR is eluted or peeled off. Therefore, it is necessary to shorten the development time or lengthen the exposure time to facilitate the dissolution of the liquid positive resist.
(2) Another method for etching metal is to form a metal mask by plating. As a specific example, there is a “first silver plating method” by silver plating. In this method, partial silver plating is performed on a metal, and a portion of the metal not covered by the silver plating is etched using an etching solution that selectively dissolves the metal. However, as a result of the etching of the metal, a so-called side etching layer is formed under the silver plating functioning as masking, and the silver plating on the side etching is in a floating state alone. In this situation, the silver plating may be chipped or cracked due to the spray pressure of the etching solution.

JP-A-62-115891

  Therefore, in the present invention, the problem of peeling of the dry film resist (DFR) in the multistage etching method (1) of the prior art is solved, and the silver plating mask used as a mask in the method (2) is used. Metal plate pattern and circuit such as lead frame, metal mask, etc. with high aspect ratio by multi-step etching by improving the strength of metal mask and improving the metal mask formation method itself to improve strength It is an object of the present invention to provide a method for forming a conductor pattern on a substrate.

  To achieve the above object, according to the present invention, a step of forming a first metal layer made of a metal different from the metal plate on both sides or one side of the metal plate, and the metal on the first metal layer. Forming a second metal layer made of the same kind of metal as the plate thicker than the first metal layer; applying a resist on the second metal layer; and patterning the resist to form a resist pattern; Etching the second metal layer using the resist pattern as a mask to form a second metal layer pattern, etching the first metal layer using the second metal layer pattern as a mask, A step of forming a pattern of the second metal layer, a step of half-etching the metal plate using the pattern of the first metal layer and the second metal layer as a first masking, and a step from above the first masking. Applying a positive resist on the etched surface, exposing and developing from above the first masking to protect the positive resist under the first masking, and protecting the first masking and protecting Metal plate pattern formation, comprising: a step of half-etching the metal plate again through a second mask made of the positive resist; and a step of removing the first masking and the second masking. A method is provided.

  According to the present invention, the step of forming a first metal layer made of a metal different from the metal foil on the metal foil formed on both surfaces or one surface of the insulating base material; and the metal on the first metal layer. Forming a second metal layer made of the same metal as the foil thicker than the first metal layer; applying a resist on the second metal layer; and patterning the resist to form a resist pattern; Etching the second metal layer using the resist pattern as a mask to form a second metal layer pattern, etching the first metal layer using the second metal layer pattern as a mask, A step of forming a pattern of the second metal layer, a step of half-etching the metal plate using the pattern of the first metal layer and the second metal layer as a first masking, and a step from above the first masking. Applying a positive resist on the etched surface, exposing and developing from above the first masking to protect the positive resist under the first masking, and protecting the first masking and protecting Forming a circuit board comprising: a step of half-etching the metal plate again through a second masking made of the positive resist; and a step of removing the first masking and the second masking. A method is provided.

  In these cases, the first metal layer as the light-shielding layer does not dissolve in the etching solution when half-etching or selective etching is performed on the metal plate or metal foil as the base material. Must be metal.

  The step of coating, exposing and developing the positive resist to protect the positive resist under the first masking and the step of half-etching the metal plate again through the second masking are repeated. It is characterized by that.

  The metal plate and the first metal layer are copper, iron, or an iron-nickel alloy, and the second metal layer is silver or gold.

  The resist applied on the second metal layer is a dry film resist, and the positive resist is a liquid positive resist or an electrodeposited positive resist.

  In the step of half-etching the metal plate using the pattern of the first metal layer and the second metal layer as the first masking, the second metal layer is also etched simultaneously, but the second metal layer is completely The thickness of the second metal layer is defined so as not to be removed, and the conditions for the half etching are defined.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 and 2 show a method of forming a metal plate pattern, for example, a lead frame, according to the first embodiment of the present invention using a subtractive method for each step.

  First, in a 1st process, the silver plating layer (1st metal plating layer) 12 is formed by giving silver plating to the whole surface of the metal plate 10 which consists of copper. The first metal plating layer 12 is a metal material different from the copper plate 10 that is not dissolved by the etching solution when the etching or half-etching is selectively performed on the copper plate 10 that is a base material in a later step. is necessary. As long as these conditions are satisfied, not only silver plating but also other metal materials such as gold or tin plating may be formed as the first metal plating layer.

  Next, in the second step, the same metal material as that of the metal plate 10, that is, copper plating is applied to the entire surface of the silver plating layer 12 to form a copper plating layer (second metal plating layer) 14. The copper plating layer 14 is thicker than the silver plating layer 12.

  Next, in the third step, a dry film resist (DFR) 16 is applied to the entire surface of the copper plating layer (second metal plating layer) 14, exposed with a predetermined mask pattern, and developed to form a resist. Patterning is performed.

  In the fourth step, the copper plating layer (second metal plating layer) 14 is etched through the opening of the DFR 16 using the patterned DFR 16 as a mask. Thereby, a copper plating layer turns into the copper plating pattern layer 14a.

  Next, in the fifth step, the DFR 16 is peeled off by a known method.

  In the sixth step, the silver plating layer 12 is etched using the copper plating pattern layer 14a patterned by etching as a mask. Thereby, the silver plating layer 12 becomes the silver plating pattern layer 12a. Note that the composition of the etching solution for etching the silver plating layer 12 is different from the etching solution used for etching the copper plating layer 14, that is, an etching solution that dissolves silver but does not dissolve copper.

  Next, in the seventh step, half etching or selective etching is performed by spraying an etching solution toward the first masking 15 formed by overlapping both the copper plating pattern layer 14a and the silver plating pattern layer 12a. However, in this half etching, the peripheral region of the copper plate 10 below the etching solution passage portion of the first masking 15 is dissolved. And the melt | dissolution area | region of the copper plate 10 does not reach the lower surface of the copper plate 10, but also the side part of the 1st masking lower part is etched, and what is called side etching is performed. Accordingly, the half-etching conditions (etching time, etc.) are adjusted so that the area where the copper plate 10 is dissolved is within a predetermined range.

  As a result, as shown in the drawing, in the upper part of the copper plate 10 that is close to the first masking pattern 15, the dissolved portion of the copper plate 10 is inside the copper plate 10 from the width (d) of the etching solution passage portion of the first masking pattern 15. The width (e) of the melted portion is larger than the first masking pattern width (d), and the side etching portion 10b is formed. On the other hand, the portion of the groove melted by etching the copper plate 10 has a rounded cross section as a whole and becomes a substantially U-shaped groove 10a.

  In this half etching step, the upper part of the copper plating pattern layer 14a is simultaneously dissolved by the etching solution for etching the copper plate 10, but the entire thickness of the copper plating pattern layer 14a is dissolved. Instead, the thickness of the copper plating layer 14 and the etching conditions are set in advance so that a part of the thickness of the copper plating pattern layer 14a remains.

  Next, in an eighth step, a positive liquid resist 18 is applied to the entire surface of the portion that has been half-etched in the previous step. In this case, the positive liquid resist 18 is formed on the uppermost copper plating pattern layer 14a, the side surface of the silver plating pattern layer 12a, the bottom of the substantially U-shaped groove 10a of the copper plate 10 dissolved by etching, and the side etching portion 10b. It is applied over the top.

  Next, in the ninth step, exposure is performed by irradiating parallel ultraviolet rays 19 from the upper surface of the positive liquid resist 18 and then developing.

  Here, it is desirable that the ultraviolet rays 19 used for exposure be parallel light that irradiates in a direction orthogonal to the masking surface on the copper plate 10, but there is a range in which the light reaches the positive liquid resist 18. When it is deep, it does not necessarily have to be parallel light.

  By this exposure step, the portion of the positive liquid resist 18 exposed to light, that is, on the copper plating pattern layer 14a of the positive liquid resist 18, the side surface of the silver plating pattern layer 12a, and the substantially U-shaped groove 10a. The area portion 18a on the bottom is exposed. In other words, it is a region below the silver plating pattern layer 12a, and is a side etched portion that is slightly bite into the inner side of the copper foil 2 from the width (d) of the resist pattern and is dissolved during the half etching which is the previous step. The region 18b on 10b remains unexposed.

  As a method for forming the resist 18, instead of applying the liquid resist 18, positive electrodeposition (Electro Deposition) in which the resist is attached only to the portion where the metal exists may be used.

  Next, in the tenth step, the uncured liquid resist 18a is removed, and only the resist 18b on the cured side etching portion 10b is left as it is.

  In the eleventh step, an etching solution is sprayed toward the second masking 17 composed of the remaining copper plating pattern layer 14a, silver plating pattern layer 12a, and protected resist 18b, so that the second half Etching or selective etching is performed. In this second half etching, the remaining copper plating pattern layer 14a is also dissolved at the same time, so that it is almost eliminated or only a very thin layer is left. However, as the second masking 17, A groove 21 between the conductor patterns is formed by the undissolved silver plating pattern 12a and the remaining resist 18b.

  Next, in the twelfth step, the remaining positive type liquid resist 18b is peeled off.

  Here, if necessary, the steps are repeated a required number of times from the eighth step to the twelfth step.

  Finally, in the thirteenth step, the silver plating pattern 12a is removed using an etching solution that dissolves silver without dissolving copper. As a result, a lead or metal pattern 20 having a small difference in the width dimension between the upper surface and the lower surface in the cross-sectional shape of the lead 20 of the lead frame which is a conductor pattern, that is, a high aspect ratio can be obtained. As a result, lead miniaturization of the lead flare can be achieved.

  3 and 4 show a method of forming a circuit board according to the second embodiment of the present invention using the subtractive method for each step. The circuit board formation method is basically the same as the lead frame formation method according to the first embodiment of the present invention, except that the copper foil 10 is formed on the upper surface of the insulating resin substrate 30. Since it can be formed by applying the first to thirteenth steps, detailed description is omitted.

  However, in the case of forming a lead frame or the case of forming a conductor pattern on an insulating substrate, the metal pattern material, thickness, pitch, distance between patterns, and other types of etching solutions under various conditions, Needless to say, it is necessary to adjust each parameter such as etching time.

  In addition, in said 1st Embodiment, about the case where a lead frame is formed by etching from the single side | surface of the metal plate 10, Moreover, in 2nd Embodiment, the insulated substrate by which the copper foil is affixed on the single side | surface In the case of forming a conductor pattern from 30 copper foils, in both the first and second embodiments, etching is performed from both sides of the metal plate 10 or from both sides of the double-sided copper-clad insulating substrate 30. This is also possible to form a metal pattern or a conductor pattern on a circuit board.

  Moreover, although the case where copper was used as a base material which etches was demonstrated, iron, an iron-nickel alloy, etc. are applicable as a base material.

  Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, and various forms, modifications, corrections, and the like are possible within the spirit and scope of the present invention. It is.

  As described above, according to the present invention, the pitch of the conductor pattern can be narrowed in the circuit board. Moreover, the width of the upper part of the conductor pattern can be ensured, and the difference between the pattern width near the upper part and the pattern width near the lower part can be reduced. Furthermore, the subtractive method can be applied to a circuit board having a thick conductor pattern.

  Since it is used for the metal mask as the light shielding layer of the positive resist, it does not elute into the solvent that is a component of the light shielding layer. Further, in the conventional example, since the dry film resist (DFR) is patterned on the metal (copper), when developing the positive resist, it is immersed in a developing solution and is on the metal (copper). In the present invention, the masking pattern itself is extremely reduced or removed by forming a masking pattern with metal (silver) instead of DFR. No longer happen.

1 shows each step of a lead frame forming method according to a first embodiment of the present invention. Each step of the lead frame forming method subsequent to FIG. 1 is shown. Each process of the formation method of the conductor pattern of the circuit board which concerns on 2nd Embodiment of this invention is shown. Each process of the formation method of the conductor pattern of the circuit board following FIG. 3 is shown.

Explanation of symbols

10 Metal (copper) plate 12 Silver plating layer (first metal layer)
14 Copper plating layer (second metal layer)
15 First masking 16 Dry film resist (DFR)
18 Positive liquid resist 20 Lead frame (metal pattern)
30 Insulating resin substrate

Claims (10)

Forming a first metal layer made of a metal different from the metal plate on both sides or one side of the metal plate;
Forming a second metal layer made of the same kind of metal as the metal plate on the first metal layer to be thicker than the first metal layer;
Applying a resist on the second metal layer and patterning the resist to form a resist pattern;
Etching the second metal layer using the resist pattern as a mask to form a second metal layer pattern;
Etching the first metal layer using the second metal layer pattern as a mask to form a pattern of the first metal layer and the second metal layer;
Using the pattern of the first metal layer and the second metal layer as a first mask, and half-etching the metal plate;
Applying a positive resist on the first masked half-etched surface, exposing and developing from above the first masking to protect the positive masking under the first masking;
Performing half etching again on the metal plate through the first masking and the second masking made of the protected positive resist;
Removing the first masking and the second masking;
A metal plate pattern forming method comprising:   The step of coating, exposing and developing the positive resist to protect the positive resist under the first masking and the step of half-etching the metal plate again through the second masking are repeated. The metal plate pattern forming method according to claim 1.   3. The metal plate and the first metal layer are copper, iron, or an iron-nickel alloy, and the second metal layer is a silver plating layer, a gold plating layer, or a tin plating layer. The metal plate pattern formation method of description.   The resist applied on the second metal layer is a dry film resist, and the positive resist is a liquid positive resist or an electrodeposited positive resist. 2. The metal plate pattern forming method according to item 1.   In the step of half-etching the metal plate using the pattern of the first metal layer and the second metal layer as a first mask, the second metal layer is also etched at the same time, but the second metal layer is not completely removed. The metal plate pattern forming method according to any one of claims 1 to 4, wherein the thickness of the second metal layer and the conditions of the half etching are defined to a certain extent. Forming a first metal layer made of a metal different from the metal foil on the metal foil formed on both sides or one side of the insulating base;
Forming a second metal layer made of the same metal as the metal foil on the first metal layer to be thicker than the first metal layer;
Applying a resist on the second metal layer and patterning the resist to form a resist pattern;
Etching the second metal layer using the resist pattern as a mask to form a second metal layer pattern;
Etching the first metal layer using the second metal layer pattern as a mask to form a pattern of the first metal layer and the second metal layer;
Using the pattern of the first metal layer and the second metal layer as a first mask, and half-etching the metal plate;
Applying a positive resist on the first masked half-etched surface, exposing and developing from above the first masking to protect the positive masking under the first masking;
Performing half etching again on the metal plate through the first masking and the second masking made of the protected positive resist;
Removing the first masking and the second masking;
A method for forming a circuit board, comprising:   The step of coating, exposing and developing the positive resist to protect the positive resist under the first masking and the step of half-etching the metal plate again through the second masking are repeated. The method for forming a circuit board according to claim 6.   The circuit board according to claim 6 or 7, wherein the metal plate and the first metal layer are copper, iron, or an iron-nickel alloy, and the second metal layer is silver, gold, or soot. Method.   9. The resist applied on the second metal layer is a dry film resist, and the positive resist is a liquid positive resist or an electrodeposited positive resist. 2. A method for forming a circuit board according to item 1.   In the step of half-etching the metal plate using the pattern of the first metal layer and the second metal layer as the first masking, the second metal layer is also etched simultaneously, but the second metal layer is completely The method for forming a circuit board according to any one of claims 6 to 9, wherein the thickness of the second metal layer is defined so as not to be removed, and the conditions for the half etching are defined.

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