JPWO2007060824A1 - Etching solution for thermoplastic polyimide resin - Google Patents

Abstract

An etching solution for a thermoplastic polyimide resin containing an alkali metal hydroxide, water and ethanolamine, wherein the relationship between the alkali metal hydroxide concentration (X wt%) and the water concentration (Y wt%) is [1], [2] and [3]: X> 20 [1] Y <−X + 60 [2] Y> 0.25X + 17.5 [3] (provided that alkali metal hydroxide, water and ethanolamine) By using the etching solution represented by the coordinate points in the region indicated by X) and Y), a good etching result is obtained even for the thermoplastic polyimide resin. [Selection] Figure 1

Description

  The present invention relates to an etching solution used for etching processing of a resin having thermoplastic polyimide by a wet process.

  2. Description of the Related Art Conventionally, in a two-layer CCL (copper clad layer) polyimide base material, which has been widely used as an insulating material for electronic component base materials, the market needs for low-cost base materials are increasing. In order to meet such demands, recently, a laminated base material obtained by bonding a metal layer such as a copper foil layer or a stainless steel layer and a polyimide layer via a thermoplastic polyimide has been expanding its share.

  Many such base materials are commercially available from related companies. For example, Espanex (trade name manufactured by Nippon Steel Chemical Co., Ltd.), Neoprex (trade name manufactured by Mitsui Chemicals, Inc.), Upilex VT ( Product name of Ube Industries, Ltd.).

  Among these laminated base materials of metal layers and polyimide layers, those used as circuit boards for electronic components are provided with through holes, device holes, etc. in the polyimide layer.

Conventionally, they have been drilled by processing light energy (UV irradiation, CO ₂ laser, etc.). However, post-processing (using potassium permanganate, etc.) is required, and time is required for fine hole processing. For example, an etching solution such as that described in Japanese Patent No. 3251515, Japanese Patent Application Laid-Open No. 2003-082135, or the like is used because of low productivity and risk of damaging the metal layer. Drilling by the chemical etching method used has become common.

  The etching solution for polyimide resin described in the above-mentioned Japanese Patent No. 3251515 consists of an aqueous solution containing 5 to 40% ethanolamine, 20 to 45% potassium hydroxide and the balance water. As a result of trying the etching of the laminated base material with an etching solution having a concentration by a number of combinations in the region of the composition ratio of the etching solution, an effect was observed for the completely imidized polyimide layer. The thermoplastic polyimide, which is the medium for bonding the metal layer and the polyimide layer, has an extremely slow etching rate, and further remains adaptable to materials containing thermoplastic polyimide, such as residual thermoplastic polyimide particles remaining. There was no at all.

  In addition, the component concentration of the etching solution in the etching method of the laminate including the polyimide layer described in Japanese Patent Application Laid-Open No. 2003-082135 is insufficient for the moisture concentration compatible with the alkali metal hydroxide and the axylalkylamine. Therefore, when the components are not mixed evenly and the dry film is used as a mask material at the time of etching, there is a problem that the dry film swells and peels and does not serve as a mask.

  The present invention specifies a component concentration region that is different from the component concentration region of the etching solution used for etching for conventional polyimide resin, thereby making it possible to obtain thermoplastic polyimide resins having poor etching results. Another object of the present invention is to provide an etching solution for a thermoplastic polyimide resin that can provide good etching results.

The etching solution for thermoplastic polyimide resin of the present invention contains an alkali metal hydroxide, water and ethanolamine, and the alkali metal hydroxide concentration (X wt%) and the water concentration (Y wt%) The following relations [1], [2] and [3]:
X> 20 [1]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
(However, the total weight of the alkali metal hydroxide, water, and ethanolamine is defined as 100, and X and Y are defined.) The etching solution is represented by coordinate points in a region that satisfies the conditions.

However, the following equations [1 ′], [1 ″], [2] and [3]:
X> 21 [1 ']
Y <35 [1 ″]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
It is preferable that the etching solution is represented by coordinate points in a region that satisfies the above.

  In the etching process of the thermoplastic polyimide resin using the etching solution in the component concentration region of the present invention, the time required for etching of the conventional thermoplastic polyimide resin is significantly shortened, and the particulate residue of the thermoplastic polyimide is also reduced. A complete etching result is obtained which does not remain at all.

  Furthermore, since the etching liquid does not pass through the dry film used as a mask material during etching, the polyimide surface of the portion to be protected by the dry film is not roughened.

It is a graph which shows the component density | concentration area | region of the alkali metal hydroxide and water in the etching liquid in this invention. It is a microscope picture which shows the etching state of Example 1 of this invention. It is a microscope picture which shows the etching state of the comparative example 1 with this invention. It is a microscope picture which shows the etching state of the comparative example 2 with this invention. It is a figure which shows the result of having etched the CCL polyimide base material containing a thermoplastic polyimide layer using the etching liquid which changed the component density | concentration of an alkali metal hydroxide and water. CCL polyimide including a thermoplastic polyimide layer using an etching solution in which the component concentration region of alkali metal hydroxide and water in the etching solution and the concentration of components of alkali metal hydroxide and water are changed in the present invention It is a graph which shows the result of having etched a substrate. It is a longitudinal cross-sectional view explaining each state of an etching in-progress, an etching shortage, an etching slightly shortage, an etching completion, and DF (dry film) damage.

The laminated base material used for the circuit board for electronic components is formed by bonding a metal layer such as a copper foil layer or a stainless steel layer and a polyimide layer which is an insulating layer via a thermoplastic polyimide resin, In order to make the metal layer play a role as an electrical circuit, drilling a through hole or a device hole in a desired portion of the polyimide layer containing the thermoplastic polyimide resin, or
Etching is performed to form an electric circuit pattern.

  Therefore, the etching solution for thermoplastic polyimide resin in the present invention has been intensively studied in view of the fact that there is no optimum etching solution for the etching process of the thermoplastic polyimide part contained in the laminate, and as a result, the polyimide layer is In other words, the present inventors have found a component concentration region in which good etching results can be obtained even when the thermoplastic polyimide layer is reached.

  The present invention specifies a certain component concentration region different from the component concentration region of an etching solution effective for conventional polyimide etching, and the component concentration region is as follows.

That is, it contains an alkali metal hydroxide, water and ethanolamine, and the relationship between the alkali metal hydroxide concentration (X wt%) and the water concentration (Y wt%) is the alkali in the etching solution of FIG. In the graph showing the concentration region of metal hydroxide and water, X = 20, Y = −X + 60 and Y = 0.25X + 17.5 in a region surrounded by a straight line, that is, the following formula [ 1], [2] and [3]:
X> 20 [1]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
(However, X and Y are defined with the total weight of alkali metal hydroxide, water, and ethanolamine being defined as 100).

  In addition, it is preferable to use potassium hydroxide or sodium hydroxide as the alkali metal hydroxide.

  Hereinafter, the example at the time of using the etching liquid of this invention and the comparative example at the time of using another etching liquid are demonstrated.

Laminated dry film is laminated on a laminated base material that is coated with thermoplastic polyimide on a stainless steel layer that is a metal layer, and polyimide is adhered to the laminated substrate, and the wiring pattern is patterned by exposure and development. The thermoplastic polyimide was etched for 3 minutes at a temperature of 80 ° C. with an etching solution having a concentration relationship of 25% potassium hydroxide, 30% water, and 45% ethanolamine. (Refer to the position of the coordinate point of Example 1 in FIG. 1)
As a result of etching, the polyimide on the stainless steel layer and the thermoplastic polyimide were completely etched, and no granular residue of the thermoplastic polyimide was observed, and the straightness of the etched surface was also obtained. (See Figure 2.)

Comparative Example 1

Etching was performed for 3 minutes at a temperature of 80 ° C. using an etching solution having a concentration relationship of 25% potassium hydroxide, 22.5% water, and 52.5% ethanolamine, using a laminated base material under the same conditions as in Example 1. . (Refer to the position of the coordinate point of Comparative Example 1 in FIG. 1.)
The etching result shows that the concentration of ethanolamine is higher than that of the example, so that the dry film swells and the etching solution passes through the dry film, and the polyimide surface that is to be protected by the dry film is partially It was confirmed that a patchy depression was formed in that portion. (See Figure 3.)

Comparative Example 2

Etching was performed for 3 minutes at a temperature of 80 ° C. using an etching solution having a concentration relationship of 25% potassium hydroxide, 37.5% water, and 37.5% ethanolamine using the laminated base material under the same conditions as in Example 1. . (Refer to the position of the coordinate point of Comparative Example 2 in FIG. 1.)
As a result of etching, the thermoplastic polyimide was not completely etched, and the residue of the granulated thermoplastic polyimide remained without being completely removed. Further, even if the etching time is extended, only the side etching of the polyimide portion becomes large, and a newly semi-dissolved thermoplastic polyimide remains as a granular material. (See Figure 4.)
As described above, in the etching process of the polyimide laminated substrate containing the thermoplastic polyimide used for electronic components, the etching solution in the component concentration region of the present invention is superior to the etching of the thermoplastic polyimide. It can be seen that the effect is exhibited.

  Moreover, the laminated base material which apply | coated thermoplastic polyimide to the copper layer which is a metal layer using the etching liquid of the range of 20-40% of water, and the alkali metal hydroxide 15-35%, and adhere | attached the polyimide on it. Further, the polyimide film and the thermoplastic polyimide in the opening portion of the dry film were etched by laminating the dry film and patterning the wiring pattern by exposure and development. And the etching result was evaluated corresponding to each state shown in FIG. 7A shows a state in which etching has not progressed (etching has started, but the depth of etching is thin, so the distinction from other parts is not clear), and FIG. In the etching deficient state (etching has progressed to a considerable depth but has not yet reached the bottom copper), (C) in FIG. 7 is slightly deficient in etching (the etching depth has reached the bottom copper). However, in FIG. 7, (D) shows the state where the etching is completed (the etching depth reaches the bottom copper, and the bottom also has the copper surface). (E) in FIG. 7 shows the DF damage state (etching solution passes through the DF mask and the etching solution enters the region, and traces that are considered to be partially etched are observed in various places). ) In pairs and ending state and quenching start state, respectively.

  The evaluation results are shown in FIG. 5 and FIG. FIG. 6 shows an etching solution region described in JP-A-10-97081, an etching solution region described in JP-A-2003-082135, and an etching solution region of the present invention. JP-A-10-97081, JP-A-2003-082135, and claims.

When the alkali metal hydroxide is 30% and the water is 35%, the alkali metal hydroxide is 35% and the water is 40%. A) see)
When alkali metal hydroxide is 15%, water is 20%, 25%, 30%, 35%, 40%, alkali metal hydroxide is 20%, water is 20%, 25%, 30%, 40% In the case of 25% alkali metal hydroxide, 20% water, 40%, 30% alkali metal hydroxide, 20%, 25%, 40% water, the alkali metal hydroxide In the case of 35%, water 20%, 25%, 30%, 35%, even if etching is performed for 12 minutes, the etching is insufficient (see FIG. 7B), and the alkali metal hydroxide is 20%. %, Water 30%, 40%, alkali metal hydroxide 25%, water 40%, alkali metal hydroxide 30%, water 40%, dry film damage ( (Referred to as DF damage) (see (E) in FIG. 7)
20% alkali metal hydroxide, 35% water, 21% alkali metal hydroxide, 35% water, 22% alkali metal hydroxide, 35% water, alkali metal When the hydroxide is 25% and the water is 35%, even if etching is performed for 12 minutes, the etching is slightly insufficient (see (C) in FIG. 7) and dry film damage (referred to as DF damage) ( (See (E) in FIG. 7)
When alkali metal hydroxide is 21% and water is 30%, alkali metal hydroxide is 22%, when water is 25% and 30%, alkali metal hydroxide is 25%, water is 25%, 34 %, When the alkali metal hydroxide is 29% and the water is 30%, even if etching is performed for 12 minutes, the etching is slightly insufficient (see (C) in FIG. 7).
When the alkali metal hydroxide is 22% and the water is 34%, the etching is completed by performing etching for 10 minutes (see (D) in FIG. 7), the alkali metal hydroxide is 25%, water Was 30%, etching was completed for 6 minutes (see FIG. 7D).

From these evaluation results, alkali metal hydroxide, water and ethanolamine are contained, and the relationship between the alkali metal hydroxide concentration (X wt%) and the water concentration (Y wt%) is shown in FIG. A region surrounded by a straight line represented by an equation in the graph showing the concentration region of alkali metal hydroxide and water in the liquid, X = 21, Y = 35, Y = −X + 60 and Y = 0.25X + 17.5 Of the following, [1 ′], [1 ″], [2] and [3]:
X> 21 [1 ']
Y <35 [1 ″]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
(However, the total weight of the alkali metal hydroxide, water, and ethanolamine is defined as 100, and X and Y are defined.) Both improvement and elimination of DF damage can be achieved.

Claims (2)

An etching solution for a thermoplastic polyimide resin containing alkali metal hydroxide, water and ethanolamine, wherein the relationship between the alkali metal hydroxide concentration (X wt%) and the water concentration (Y wt%) is The following equations [1], [2] and [3]:
X> 20 [1]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
(However, the total weight of the alkali metal hydroxide, water, and ethanolamine is defined as 100, and X and Y are defined.) A thermoplastic that is an etching solution represented by coordinate points in the region indicated by Etching solution for polyimide resin. The region is represented by the following formulas [1 ′], [1 ″], [2] and [3]:
X> 21 [1 ']
Y <35 [1 ″]
Y <−X + 60 [2]
Y> 0.25X + 17.5 [3]
The etching solution for thermoplastic polyimide resin according to claim 1, which is a region represented by

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