JP4412338B2 - Pattern formation method - Google Patents

Description

  The present invention relates to a method for removing a resist used for manufacturing a printed wiring board using a build-up manufacturing method. More particularly, the present invention relates to a method for forming a pattern on a printed wiring board in which a residue remaining after a resist is stripped with an alkaline stripping solution is removed.

FIG. 2 shows a conventional method for forming a conductor circuit of a printed wiring board.
1 is a printed wiring board, 2 is an insulating film as a substrate, 3 is a seed layer, 4 is a resist layer, 5 is a plating layer, 6 is a residue, and 7 is a conductor circuit.

First, FIG. 2A is a process of providing the seed layer 3.
As shown in the figure, a seed layer 3 is formed to a thickness of about 0.1 μm to 0.5 μm on an insulating film 2 as a substrate by an electroless copper plating method.

Next, FIG. 2B is a step of providing a resist layer.
A resist layer 4 is provided on the seed layer 3, and a desired pattern is provided on the resist layer 4. Specifically, a photosensitive dry film type resist is attached to the resist at low cost and easy to handle, and a conductive circuit is formed by forming a pattern on the photosensitive resist 4 by photographic method.

Further, FIG. 2C is a process of providing the plating layer 5.
An electroplating process is performed to provide a copper plating layer 5 in a desired thickness on the pattern on the seed layer 3.

Subsequently, FIG. 2D is a process of stripping the resist layer.
The resist 4 is stripped with a resist stripping solution. This resist stripping solution is an inorganic alkaline aqueous solution of sodium hydroxide or an organic alkaline aqueous solution of monoethanolamine. These resist stripping solutions are selected according to the material of the resist used.

Subsequently, FIG. 2E is a step of etching the seed layer 3.
The seed layer 3 exposed from the conductor circuit 7 is stripped by an etching method. Therefore, a desired conductor circuit 7 is formed on the insulating film 2 as a substrate.

However, if the residue 6 remains on the seed layer 3 after the resist stripping process as shown in FIG. 2D, the process of etching the seed layer 3 as shown in FIG. Thus, the seed layer 3 at a desired position is not removed, and the conductor circuits 7 are short-circuited to each other. Or it becomes defects, such as the space | interval of the adjacent conductor circuit 7 becoming narrow. In particular, the higher the density of the conductor circuit, the easier it is to cause defects.

As a technique for solving this problem, there is a method in which the printed wiring board 1 having a residue is immersed in a strong acid and then removed by brushing with an acid-resistant brush.
However, if the residue 6 is removed using mechanical means such as brushing as in the above method, the wiring is damaged, peeled off and cut.

  And in order to solve this subject, the inventor investigated the component of the residue 6. As a result, the residue 6 is light mainly composed of an imidazole dimer such as 2,2′-bis (o-chlorophenyl) -4, 4 ′, 5,5′-tetraphenyl-1,2′-biimidazole. It was found to be a reaction initiator. And it became clear that this residue 6 cannot be removed with an alkaline resist stripping solution.

  An object of the present invention is to completely remove the residue 6 and prevent a short circuit between the conductor circuits of the seed layer 3 and a decrease in the interval between adjacent conductor circuits. It is another object of the present invention to provide a method of manufacturing a conductor circuit that can completely remove a residue of a dry film resist component without cutting or scratching the conductor circuit when removing the resist.

  In order to achieve the above object, according to the first aspect of the present invention, in the pattern forming method, a resist layer corresponding to the pattern is formed on the underlying metal layer with 2, 2'-bis (o-chlorophenyl) -4, 4 '. A photoreaction initiator having 5,5′-tetraphenyl-1,2′-biimidazole, formed of a resist material soluble in an alkaline solution, and provided with a conductor circuit by plating on the pattern, The layer is stripped with an alkaline resist stripper, and the residue remaining after stripping is 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-biphenyl Contains nitrogen-containing compounds containing imidazole, an organic acid containing at least one of acetic acid, citric acid, formic acid and lactic acid, and at least one of benzotriazole, 2-ethylbenzimidazole and 3-hydroxy-2-pyrone Remove the residue with a removing solution Method for forming a pattern characterized by having a that process. As a result, the residue can be completely removed to prevent a short circuit of the copper in the seed layer, that is, a short circuit between the conductor circuits and a decrease in the interval between adjacent conductor circuits. Moreover, it is possible to prevent the conductor circuit from being cut or damaged when the resist is removed.

  As described above, by using the present invention, it is possible to completely remove residues and prevent a short circuit between conductor circuits and a narrow interval between adjacent conductor circuits. Moreover, when removing the resist, the residue of the dry film resist component can be completely removed without cutting or scratching the conductor circuit.

  Examples of the present invention will be described.

<Example 1>
FIG. 1 shows a method for forming a conductor circuit of a printed wiring board according to the present invention.
In the drawings, the same reference numerals are assigned to the same components.

First, FIG. 1A shows a step of providing a seed layer 3.
The laminated plate 2 is formed with a copper pattern on both sides, and an epoxy insulating layer is formed on the pattern. A via hole with a diameter of 100 μm is made by a carbon dioxide laser. Further, as a pretreatment agent, it was immersed in a product name conditioner manufactured by Shipley Co., Ltd. at 60 ° C. for 10 minutes, and then immersed in a product name promoter, an oxidizing agent manufactured by Shipley Co., Ltd., at pH 11, 70 ° C. for 10 minutes. It is immersed in a product name Neutizer, a neutralizer made by the company, at 60 ° C. for 10 minutes and desmeared so as to form surface irregularities. A seed layer 3 (underlying metal layer) was formed to a thickness of about 0.2 μm on the laminate 2 by an electroless copper plating method.

Further, FIG. 1B shows a step of providing a resist layer.
A photosensitive dry film was laminated on the seed layer 3. The resist layer 4 is a product name NIT-250 manufactured by Nichigo Morton Co., Ltd., and has a film thickness of 50 μm. Next, after exposure using a photomask, development was performed with an aqueous sodium carbonate solution to form a pattern of L / S = 50/50 μm.

Next, FIG. 1C is a step of providing a plating layer 5.
A plating layer 5 having a thickness of about 20 μm was formed on the resist layer 4 by electrolytic copper plating.

Further, FIG. 1D shows a step of peeling the resist layer.
The resist layer 4 was stripped with a 3 wt% aqueous sodium hydroxide solution using an ultrasonic dip method. In this step, residue was visually observed.

Further, FIG. 1E is a step of removing the residue.
Most of the residue removing liquid used is an organic acid, a nitrogen-containing compound, alcohol and water.
For details, use acetic acid (50wt%) and citric acid (15wt%) as organic acids, benzotriazole (0.5wt%) and 2-ethylbenzimidazole (0.5wt%) as nitrogen-containing compounds, and alcohol Isopropyl alcohol (20 wt%) is used as water, and water (14 wt%). The printed wiring board 1 was treated by the dip method in this residue removing solution to completely remove the residue. At this time, the L / S side etching amount of the conductor circuit was 0.5 μm or less on both sides.

  In order to remove the resist residue more effectively, ultrasonic waves can be applied to the stripping residue removal processing solution, or the stripping residue removal processing solution can be sprayed onto the substrate by spraying. If foaming occurs during spraying, a small amount of an antifoaming agent such as polyalkylene glycol can be added.

Finally, FIG. 1F shows a step of etching the seed layer 3.
The seed layer 3 was etched to form a conductor circuit.

The residue removing liquid described above contains an organic acid and a nitrogen-containing compound. For this purpose, the organic acid removes residues and simultaneously side-etches the conductor circuit. However, since it contains a nitrogen-containing compound, the organic acid can be prevented from side-etching the conductor circuit.
<Example 2>
The second embodiment is a method of manufacturing the circuit board shown in FIG.
However, Example 2 is different from Example 1 in that the resist layer shown in FIG. 1 (b) is provided, the resist layer shown in FIG. 1 (d) is stripped, and the residue shown in FIG. 1 (e) is removed. It is. Only these different steps will be described in detail.

  Following the step of providing the seed layer 3 as in Example 1, a photosensitive dry film was laminated on the seed layer 3 as shown in FIG. This resist is a product name SPG manufactured by Asahi Kasei Co., Ltd., and its film thickness is 30 μm. Next, after exposure using a photomask, development was performed with an aqueous sodium carbonate solution to form a pattern of L / S = 30/30 μm.

  Further, after providing the same plating layer 5 as in Example 1, as shown in FIG. 1D, the resist layer 4 was stripped with a monoethanolamine aqueous solution using a spray method. When foaming occurs during this spraying process, a predetermined amount of an antifoaming agent such as polyalkylene glycol can be added. In this step, peeling residue was visually observed.

Next, FIG.1 (e) is a process of removing a residue.
Most of the residue removing liquid used is an organic acid, a nitrogen-containing compound and water. For details, formic acid (40 wt%) and lactic acid (20 wt%) are used, and 3-hydroxy-2-pyrone (2 wt%) and benzimidazole (2 wt%) are used as nitrogen-containing compounds. (36wt%) is used. The printed wiring board 1 was treated in this residue removing liquid by a spray method to remove the residue. At this time, the L / S side etching amount of the conductor circuit was 0.5 μm or less on both sides.

Finally, the same step of etching the seed layer 3 as in Example 1 is performed.
Therefore, as in Example 1, the organic acid removes the residue and simultaneously side-etches the conductor circuit. However, the nitrogen-containing compound can prevent the organic acid from side-etching the conductor circuit.
<Comparative Example 1>
The residue removing solution used in Comparative Example 1 differs from Example 1 only in that it does not contain a nitrogen-containing compound. Except for this point, the same procedure as in Example 1 was performed. That is, the organic acid removes the residue and simultaneously side-etches the conductor circuit. However, side etching cannot be prevented by adding no nitrogen-containing compound. As a result, the residue could be removed, but the L / S side etching amount of the conductor circuit was 3 μm or more on both sides.

  As a result of the above, a residue mainly composed of an imidazole dimer such as 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-biimidazole was obtained. The removal treatment liquid to be removed is preferably an organic acid such as formic acid, acetic acid, citric acid and lactic acid. However, even if these organic acids are used alone or diluted with water or alcohol, the residue and the conductor circuit are etched when the residue is removed. When this conductor circuit is etched, the conductor circuit is thinned, making it difficult to secure a prescribed conductor circuit width. Etching of this conductor wiring can be prevented by containing a nitrogen-containing compound.

  As organic acids other than the above, organic acids such as malic acid, phthalic acid, benzoic acid, succinic acid, tartaric acid, oxalic acid, propionic acid and maleic acid can be used. At least one of these may be used.

  As nitrogen-containing compounds other than those described above, nitrogen-containing compounds such as 2-pyrrolidone, indole, indoline, imidazole, imidazolidine, 2-benzimidazolinone, purine, 1H-tetrazole, pyrone, and derivatives thereof can be used. At least one of these may be used.

  Next, as alcohols other than the above, alcohols such as methanol and ethanol can be used. At least one of these may be used.

  The composition of the residue removing solution is 20 to 95 wt%, preferably 40 to 70 wt% for the organic acid, 0.01 to 10 wt%, preferably 0.1 to 5 wt% for the nitrogen-containing compound, and 0 to 60 wt% for water, preferably The effective amount is 10 to 50 wt%, and the alcohol is 0 to 60 wt%, preferably 10 to 50 wt%.

Process drawing of the manufacturing method of the printed wiring board concerning the present invention, It is process drawing of the manufacturing method of the printed wiring board which concerns on a prior art.

Explanation of symbols

1 printed wiring board,
2 laminates and insulating films,
3 Seed layer,
4 resist layer,
5 plating layer,
6 residue,
7 Conductor circuit.

Claims (1)

In the pattern formation method,
Photoinitiator with 2, 2'-bis (o-chlorophenyl) -4, 4 ', 5, 5'-tetraphenyl-1, 2'-biimidazole corresponding to the pattern on the underlying metal layer Formed with a resist material soluble in an alkaline solution,
A conductive circuit is provided by plating on the pattern,
Strip the resist layer with an alkaline resist stripper,
2, 2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-biimidazole, the residue remaining after peeling, is added to acetic acid, citric acid, formic acid, and lactic acid. Removing the residue with a removing solution containing a nitrogen-containing compound containing at least one of an organic acid containing at least one of benzotriazole, 2-ethylbenzimidazole, and 3-hydroxy-2-pyrone A method for forming a pattern, comprising:

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