JPH077245A - Water-soluble resist - Google Patents

Abstract

PURPOSE:To prevent precipitation of lead on a board at the time of releasing by incorporating a specific organic material or an ingredient for generating its salt. CONSTITUTION:An organic material or an ingredient for generating its salt to be dissolved or decomposed in release liquid and represented by the formula is included in watersoluble resist which can be released with strong alkaline water solution (where, in the formula, N is tertiary amine bonded directly to a -CH2COOH group, R, R' are substituent groups or molecular chains). Thus, dissolution of solder plating can be suppressed, and precipitation of lead can also be suppressed. Thus, excellent wirings without wiring defect can be formed. As the other effects, even if inorganic alkali such as low-cost sodium hydroxide, potassium hydroxide, etc., is used as the releasing liquid for releasing this resist, damage of the solder is small, and it is not necessary to use expensive organic alkali. It is not necessary to add dissolution inhibitor of the solder to the release liquid, and the management of the releasing liquid is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble resist used for manufacturing wiring boards.

[0002]

2. Description of the Related Art As one of the methods for manufacturing a wiring board, a method is known in which wiring is formed by using solder as an etching resist. Taking the general case of this method as an example, on a substrate with copper foil laminated on both sides, after drilling, copper plating is performed,
After that, with the organic resist film, the portion other than the plated portion is covered, solder plating is performed, and after peeling the organic resist film,
The unnecessary portion of copper is removed by etching.

There is a method of using a water-soluble resist for this organic resist film and peeling it with an alkaline aqueous solution. The resin of such an organic resist is, for example, acrylic acid,
Some are composed of a copolymer of methacrylic acid or its ester and a vinyl monomer such as styrene, a photopolymerizable monomer such as acrylic acid ester or methacrylic acid ester, and a photoreaction initiator, and are often used as a dry film. .

The stripping solution used for stripping the water-soluble resist is generally a strong alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, and is often used at a pH of 13 or more. The temperature at this time is 40 to 50 ° C., and the time required for peeling is generally about 2 to 3 minutes.

The actual stripping time is almost the time required for stripping the resist (about 40 to 40%) because the stripping residue and the like do not remain on the high density pattern portion and the water-soluble resist is stripped completely.
(50 seconds). For this reason, copper (the part where the water-soluble resist is peeled off) and the solder plating are exposed to the peeling liquid at the same time for a long time of the peeling work.

Since the stripping solution is a strong alkaline solution as described above, it should serve as an etching resist, the solder is dissolved, and its thickness becomes insufficient.
Further, one of the constituent metals of the solder (tin) may be excessively melted. In particular, in the peripheral portion of the substrate or in a sparse pattern, the current density of the solder plating becomes large, the tin component in the solder plating increases, and it tends to be easily dissolved. For this reason, in the subsequent alkaline etching step, it may not be possible to sufficiently function as an etching resist, and defects such as disconnection or chipping may be created in the wiring. Further, the local battery action due to the contact between copper and solder at the time of peeling the water-soluble resist is also a factor for promoting the corrosion and dissolution of the solder described above.

Therefore, in order to prevent this corrosion and dissolution, a reducing substance, a method of further adding sodium aryl sulfonate, an organic sulfur compound, etc., a method of adding a borohydride compound, a method of adding an imidazole compound. Alternatively, the method of adding 3,5 dimethylpyrazole is disclosed in JP-A-63-183445 and JP-A-64-2425.
No. 4, JP-A-64-81295 and JP-A-62-151589, respectively.

Further, when the water-soluble resist is peeled off, lead ions are deposited on the copper surface after the water-soluble resist is peeled off, which hinders etching, which may cause a short circuit between wirings. Therefore, a method of adding an oxidizing agent in order to prevent the precipitation of lead is disclosed in JP-A-63-38588.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No. 3445, No. 64-24254, No. 64-81295, and No. 62-1515.
With the stripping solution disclosed in Japanese Patent Laid-Open No. 89, a sufficient effect cannot be obtained if the stripping operation is performed by a spray method.

Further, in JP-A-63-38588, a method using an oxidizing agent, which is shown as a method for preventing the precipitation of lead, and in JP-A-63-183445 and JP-A-64-81295 are disclosed. It is not compatible with the method using a reducing substance, which is shown as a method for suppressing the melting of solder. That is, until now, it has been difficult to simultaneously suppress the dissolution of solder and prevent the precipitation of lead.

The present invention provides a water-soluble resist capable of preventing the deposition of lead on a substrate during peeling.

[0012]

The water-soluble resist of the present invention comprises a substrate on which a copper foil is laminated, a plating resist formed with the water-soluble resist, solder plating, and then peeling with a strong alkaline aqueous solution. The water-soluble resist that can be formed is characterized by containing a component that dissolves or decomposes in a stripping solution to form an organic compound represented by formula (1) or a salt thereof.

[Chemical 2] (N in the above chemical formula is a tertiary amine that is directly bonded to a —CH ₂ COOH group, and R and R ′ represent a substituent or a molecular chain.)

Regarding the precipitation of lead which hinders the formation of wiring, Japanese Patent Application Laid-Open No. 63-38588 describes the effect of remaining components of the solder plating solution. However, according to the results of studies by the authors, it is considered that the precipitation of lead is caused in the stripping solution. This will be described in detail below.

Tin and lead, which are the constituent metals of the solder used for the etching resist of copper, dissolve at pH of 13 or more. It is shown in FIG. 17-11 in "Introduction to Corrosion and Corrosion of Metals" p242, Kagaku Dojin, 1984. "Tin potential-p
H diagram ”, FIGS. 17-12 in p243,“ lead potential-pH diagram ”, and the like. Actually, when a high-density solder plating pattern having a wiring width and a space width of about 100 to 150 μm is formed on the copper surface and a droplet of a sodium hydroxide aqueous solution of about 40 g / l containing 400 ppm of lead ions is dropped, After leaving at room temperature for a few minutes, it is easy to observe that the exposed part of copper turns gray.
The authors have found it. In addition, lead is detected when this gray portion is analyzed.

This is considered to occur because the lead ions dissolved in the liquid are deposited. It should be noted that, regarding lead, dissolution and precipitation occur simultaneously or sequentially in the droplet. The detailed mechanism is unknown. Such a phenomenon seems to occur because there are three kinds of metals, that is, lead and tin of the solder-plated metal, and copper (a portion not solder-plated). Thus, the precipitation phenomenon of lead in the alkaline stripping solution is easily confirmed.

Japanese Patent Application Laid-Open No. Sho 63-63, which shows a method for suppressing the dissolution of solder.
-183445, JP 64-81295, JP 62-151589 and JP 63.
In Japanese Patent Laid-Open No. 38588/1985, actual examples of dissolution rate and dissolution amount at room temperature at room temperature are shown as Examples and Comparative Examples. As shown in the respective examples of these four publications, although it is possible to suppress dissolution to some extent,
It can be seen that the dissolution cannot be completely suppressed.

In practice, 1-2 kg /
With a spray pressure of cm ² , a stripping solution having a temperature of 40 to 50 ° C. is brought into contact with the substrate being conveyed using a conveyor,
A spray method for removing the water-soluble resist is often used. Thus, when a new liquid is constantly supplied to the surface of the substrate, the apparent diffusion coefficient becomes incomparably larger than that in the stationary state, and the melting rate of the solder is much higher than the values in the examples of the above publications. It is easily estimated to be large. Therefore, even if the dissolution suppressing method as described above is adopted, the solder dissolves in the stripping solution and the amount of metal ions increases with the number of processed substrates.

Actually, using a spray type water-soluble resist stripping device, OPC Parsori (manufactured by Okuno Seiyaku Co., Ltd., trade name, which is a drug containing a reducing agent corresponding to the method disclosed in JP-A-63-183445) is used. ) To the stripper,
After peeling off the dry film HF450 (trade name, manufactured by Hitachi Chemical Co., Ltd.) on the substrate (solder area: 25%) of 200 cm ² , the lead ion in the liquid was measured, and the concentration was 300 to 400 ppm. It was

The authors have found that the amount of lead ions in the stripping solution is 40
At about 0 ppm, it has been found that precipitation of lead on the surface of the substrate begins to be visually observed, and residual copper is caused by subsequent alkali etching.

Then, as a result of earnest studies, it was found that when lead ions increased in the solution, the dissolution was accelerated, and further, JP-A-63-183445 and JP-A-64-2425.
No. 4, JP-A-64-81295, and JP-A-62-151589, the results showed that the presence of lead ions in the solution resulted in an increase in dissolution.
It was found that a sufficient suppressing effect cannot be obtained. It is presumed that the reason why the dissolution is accelerated in the presence of lead ions is that the above-described lead precipitation reaction is a counter electrode reaction of corrosion and dissolution.

Further, when the dissolution current was measured, it was found that when the amount of lead ions in the liquid was 50 to 100 ppm, the precipitation of lead could not always be visually confirmed, but such an acceleration phenomenon of dissolution occurred. That is, in general peeling work, it is considered that the dissolution of solder is particularly problematic due to such an acceleration phenomenon in addition to the simple dissolution phenomenon in which the solder is dissolved in the alkaline solution.

Therefore, as a result of studying a method of forming a complex with lead ions and suppressing the precipitation of lead, it was found that an organic substance represented by the formula (1) or a salt thereof may be added to the alkaline stripping solution. It turned out to be effective, and the authors have developed a method of adding these organic substances to the stripping solution.

[0023]

[Chemical 3] (N in the above chemical formula is a tertiary amine directly bonded to the -CH2COOH group, and R and R'represent a substituent or a molecular chain.)

Further, in order to simplify the peeling work,
In advance, by including in the water-soluble resist, a component that produces the above compound in an alkaline aqueous solution at the time of stripping,
It is possible to prevent wiring defects due to subsequent alkali etching.

As the compound of the formula (1), specifically,
1,2-cyclohexanediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, triethylenetetraminehexaacetic acid and salts thereof can be mentioned.

In general, the range of effective component amounts differs depending on the ratio of lead ions to lead in the complex formed and the molecular weight of the organic substance. However, it is practically effective in the range of 0.1 to 20% by weight in the water-soluble resist. Also, 20
It is not desirable to use it in an amount exceeding 5% by weight, because it causes deterioration of the film-forming property of the water-soluble resist, plating solution resistance, and developability. On the other hand, if it is 0.1% by weight or less, the effect is recognized, but the effect is limited. A more desirable range is 0.1 to 10% by weight.
This complex may be bound to the resin or simply in a mixed state. In addition, the said organic substance may be used individually and may be used in multiple numbers. When a plurality of components are used, the above component amounts indicate the total component amounts.

Here, the resin component of the water-soluble resist to which the present invention can be applied is basically composed of a polymer binder and a photopolymerization initiator, which can be swelled or dissolved in an alkaline aqueous solution and peeled off. Such organic resist resins include, for example, copolymers of acrylic acid, methacrylic acid and their esters as polymers, copolymers obtained by adding vinyl monomers such as styrene to these, and acrylic acid esters. , A photopolymerizable monomer such as methacrylic acid ester and a photoreaction initiator such as benzophenone. The water-soluble resist of the present invention may be a photoreactive resin that can be developed with a low alkaline aqueous solution and can be stripped with a highly alkaline aqueous solution after desired treatment such as plating or etching. It is not limited to one. Further, if necessary, a thermal polymerization inhibitor, a plasticizer, a dye, a discoloring agent, and an adhesion promoter may be contained.

[0028]

Action: Until now, countermeasures have been taken by adding a substance for suppressing the dissolution of solder in the stripping solution, but under conditions where a new solution is constantly in contact, such as spraying, it is sufficient. The effect was not obtained. As a result, lead ions in the stripping solution increase, and 50-100ppm
Even in the presence of lead ions, the effect of the conventional dissolution inhibiting method was hindered. Furthermore, the amount of lead ions is 400 ppm
When it increased to a certain degree, the problem of lead precipitation also occurred.

A specific substance capable of forming a complex with a metal ion can be used to block lead ions or a copper surface, and a component which is dissolved or decomposed in a stripping solution to form this substance is dissolved in water. It was found that the stripping solution can be simplified by including it in a photosensitive resist,
The present invention has been made. In this way, the problem of lead precipitation and dissolution is solved at the same time by an approach from a water-soluble resist, which has never been carried out in the past.

[0030]

[Embodiment] (Dissolution inhibiting effect of solder of resist component alone) NaOH aqueous solution (NaOH concentration: 40 g / l)
Lead sulfate was mixed so that the lead concentration was 150 mg / l (150 ppm), and the solution was adjusted by stirring for about 2 hours to completely dissolve lead sulfate. 50 ml of this solution was poured into a beaker having a capacity of 100 ml, and copper and a solder plate coated so that each exposed area was 4 cm ² were immersed in the solution to prepare an electrode for measuring current flowing in the solution. The copper and solder electrodes were connected via a 10 ohm resistor between the lead wires from the electrodes. The melting current can be measured by measuring the voltage across the resistor. At room temperature (about 20
(° C), the liquid was stirred with a magnetic stirrer.

Further, 0.2 g of the organic substance shown in Table 1 was added to a small amount (2 to 3 ml) of an aqueous NaOH solution (NaOH concentration: 40).
A solution dissolved in g / l) was prepared. These solutions were poured into a beaker under stirring, and changes in the dissolution current were measured. As a result, the current value after the introduction of the organic matter (organic matter concentration: about 4 g / l) was 20% or more lower than the current value before the introduction.
When the decrease in the current value is less than 20% or, conversely, the decrease is indicated as ×, and Table 1 (Example: Table 1-1, Comparative Example: Table 1-2).
It was shown to. In addition, in almost all the cases of ×, no decrease in current value was observed.

Particularly, regarding the contained sulfur compounds in Comparative Examples 20 to 23, the nitro compounds in Comparative Examples 32 to 35, and the sodium bromate in Comparative Example 54, these compounds were added to a sodium hydroxide solution containing no lead ion. Only by doing so, the melting current was greatly increased, and on the contrary, the melting of the solder was promoted. From this result, it can be seen that the organic substances of the examples have the effect of suppressing the melting of the solder.

[0033]

[Table 1]

(Lead Precipitation Suppressing Effect) A copper-clad laminate was exposed and developed using a water-soluble dry film HF450 (trade name, manufactured by Hitachi Chemical Co., Ltd.) to form a pattern. This was electrosolder plated to a thickness of about 5 μm. This substrate was cut out to have a size of 2 cm × 5 cm. At this time, half of the substrate (2 cm × 2.5 cm) was covered with the dry film, and the remaining portion was solder-plated. This was immersed in an aqueous NaOH solution containing 400 ppm of lead ions and organic matter, and the dry film was peeled off. The peeling was performed in a beaker, and was performed at a temperature of 50 ° C. with a magnetic stirrer for about 2 minutes while stirring. The precipitation of lead at this time was visually observed. The one in which a gray discolored portion was observed on the exposed copper was marked as X, and the one in which no discoloration was observed and which had copper luster was marked as O. The results are shown in Table 2 (Example: Table 2-1, Comparative Example: Table 2-2). From this result, it can be seen that the organic substances of the examples have the effect of suppressing the precipitation of lead.

[0035]

[Table 2]

(Water-soluble resist of the present invention) As a polymer, methacrylic acid / methyl methacrylate / acrylic acid 2
-Copolymer 60 of ethylhexyl (23:57:20)
Parts, 30 parts of bisphenol A polyoxyethylene dimethacrylate and 10 parts of tetraethylene glycol dimethacrylate as monomers, 1 part of tribromomethylphenyl sulfone and 1 part of leuco crystal violet as an imaging agent, 6 parts of benzophenone and N as a photoinitiator. Dry film of resist composition consisting of 0.2 part of N'tetraethyl 4,4 'aminobenzophenone and 0.05 part of malachite green as a dye (Comparative Example 65)
And 100 parts by weight of this composition and 10 parts by weight of DTPA in a dry film (Example 8), and EDTA
A dry film (Example 9) containing 10 parts by weight of was prepared.

It was confirmed that exposure, development, copper plating, solder plating, and resist stripping were possible with all of the dry films of Comparative Example 65, Example 8 and Example 9. Next, after curing these dry films by ultraviolet irradiation, a NaOH aqueous solution containing 400 ppm of lead ions (Na
OH concentration: 40 g / l) 5 g each in 100 ml
Was dissolved. Substrate 3 obtained by developing a pattern on a copper-clad laminate with a dry film of Comparative Example 65 and then solder plating
The substrates were prepared, and the substrates were individually immersed in the above liquids one by one, and the dry film was peeled off. As a result, in the liquid in which 5 g of the dry film of Comparative Example 65 was dissolved, precipitation of lead was observed, but in the liquid in which 5 g of the dry film of Examples 8 and 9 was dissolved, precipitation of lead was observed in any liquid. There wasn't.

[0038]

By applying the present invention to a water-soluble resist, the dissolution of solder plating can be suppressed and the precipitation of lead can be suppressed. Therefore, it is possible to form a good wiring without a wiring defect. As another effect, the stripping solution for stripping the present resist does not require the use of expensive organic alkali because the damage to the solder is small even if an inexpensive inorganic alkali such as sodium hydroxide or potassium hydroxide is used. . It is not necessary to add a solder dissolution inhibitor to the stripping solution, and the stripping solution can be easily managed. Also,
Since the precipitation of lead is eliminated, the area of the substrate that can be treated with the same amount of stripping solution increases. Therefore, the amount of stripping liquid used per unit area of the substrate is reduced, and the amount of waste liquid is reduced. For this reason,
The waste liquid treatment cost spent for the treatment is reduced, and the waste liquid treatment is easy because the waste liquid composition is simple.

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[Procedure amendment]

[Submission date] August 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

This means that the dissolution of the solder plating metal component and the precipitation of lead ions occur simultaneously or sequentially in the droplet. The detailed mechanism is unknown. Such a phenomenon seems to occur because there are three kinds of metals, that is, lead and tin of the solder-plated metal, and copper (a portion not solder-plated). Thus, the precipitation phenomenon of lead in the alkaline stripping solution is easily confirmed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Actually, using a spray type water-soluble resist stripping device, OPC Parsori (manufactured by Okuno Seiyaku Co., Ltd., trade name, which is a drug containing a reducing agent corresponding to the method disclosed in JP-A-63-183445) is used. ) To the stripper,
After peeling off a dry film HF450 (trade name, manufactured by Hitachi Chemical Co., Ltd.) on a 200 m ² substrate (solder area: 25%), the lead ion in the liquid was measured, and the concentration was 300 to 400 ppm. It was

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Then, as a result of earnest study, when lead ions increase in the solution, the melting of the solder is accelerated.
Further, JP-A-63-183445, JP-A-64-
As a result of testing with a stripping solution disclosed in JP-B No. 24254, JP-A No. 64-81295 and JP-A No. 62-151589, the dissolution was increased in the presence of lead ions in the solution, and a sufficient suppressing effect was obtained. I found that I could not get.
It is presumed that the reason why the dissolution is accelerated in the presence of lead ions is that the above-described lead precipitation reaction is a counter electrode reaction of corrosion and dissolution.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

Further, in order to simplify the peeling work,
In advance, by including in the water-soluble resist, a component that produces the above compound in an alkaline aqueous solution at the time of stripping,
This is intended to prevent wiring defects due to subsequent alkali etching.

Claims (2)

[Claims] 1. A water-soluble resist that can be stripped with a strong alkaline aqueous solution, containing a component that dissolves or decomposes in a stripping solution to produce an organic compound represented by formula (1) or a salt thereof. A water-soluble resist characterized by: [Chemical 1] (N in the above chemical formula is a tertiary amine that is directly bonded to a —CH ₂ COOH group, and R and R ′ represent a substituent or a molecular chain.) 2. Organic substances are 1,2-cyclohexanediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid,
The water-soluble resist according to claim 1, which is one of ethylenediaminetetraacetic acid and triethylenetetraminehexaacetic acid.