JPH06250402A - Method for removing water-soluble resist - Google Patents

Abstract

PURPOSE:To provide a method for removing a water-soluble resist excellent in inhibition of dissolution of solder and also excellent in prevention of deposition of lead. CONSTITUTION:A plating resist is formed using a water-soluble resist on a substrate with laminated copper foil, solder plating is carried out and then the water-soluble resist is removed with a removing soln. contg. 0.5-100g/l triethyl phosphate and further contg. at least one among aminoguanidine, hydrazines, sulfurous acid and dithionous acid or their salts, borohydride, carbazinic ester, thiourea dioxide, sulfinic acids, sulfoxy acids, hydrazides and semicarbazide salt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a water-soluble resist in a wiring board manufacturing process.

[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 a general case of this method as an example, a substrate having copper foils laminated on both sides is perforated and then copper plated, and thereafter, an organic resist film is coated on a portion other than a plated portion. This is subjected to solder plating to remove the organic resist film, and then unnecessary portions of copper are removed by etching. There is a method of using a water-soluble resist for this organic resist film and peeling it off with an alkaline aqueous solution. 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. At this time, the temperature is 40 to 50 ° C., and the time required for peeling is
About 2 to 3 minutes is common.

The actual stripping time is almost the time required for stripping the resist (about 40 to 40) because the stripping residue does not remain in 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, or,
One of the constituent metals of the solder (tin) may be excessively melted. In particular, the current density of the solder plating becomes large in the peripheral area of the board and in the sparse pattern.
The tin ratio in the solder plating becomes high, and the dissolution of the solder plating tends to increase during peeling. 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, in stripping the water-soluble resist, lead ions may be deposited on the copper surface after stripping the water-soluble resist and inhibit 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.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No. 3445, No. 64-24254, No. 64-81295, and No. 62-1515.
In the method disclosed in Japanese Patent Publication No. 89, a sufficient effect cannot be obtained if the peeling work is performed by a spray method. Also,
Japanese Patent Laid-Open No. 63-38588 discloses a method using an oxidant, which is shown as a method for preventing the precipitation of lead, and Japanese Patent Laid-Open Nos. 63-183445 and 64-81295 suppress the melting of solder. It is not compatible with the method of using a reducing substance, which is shown as the method of 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 method of stripping a water-soluble resist which is excellent in suppressing the melting of solder and at the same time excellent in preventing the precipitation of lead.

[0007]

According to the present invention, a plating resist is formed of a water-soluble resist on a substrate laminated with copper foil,
A method of stripping a water-soluble resist, which comprises performing solder plating and then stripping the water-soluble resist, is characterized in that the stripping solution contains triethyl phosphate. Further, at least one of aminoguanidine, hydrazines, sulfurous acid, dithionous acid or a salt thereof, borohydride, carbazic acid ester, thiourea dioxide, sulfinic acids, sulfoxy acids, hydrazides, and semicarbazide salts is contained. Characterize.

Regarding the precipitation of lead which hinders the formation of wiring, Japanese Patent Application Laid-Open No. 63-38888 describes the effect of residual solder plating solution components. 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 13 or above. It is noted that Kagaku Dojin, 1984, "Introduction to Corrosion and Corrosion of Metals," p242, FIGS. "Tin potential-p
H diagram ”, FIGS. 17-12 in p243,“ lead potential-pH diagram ”, and the like. Actually, a high-density solder plating pattern having a wiring width and a space width of about 100 to 150 μm was formed on the copper surface, and 40 g / l
The authors have found that when a drop of a sodium hydroxide aqueous solution is dropped, it is easily observed that the exposed portion of copper turns gray after standing for several minutes at room temperature. Also,
Lead is detected when this gray area is analyzed. The reason for this is considered to be that once the solder-plated metal is dissolved, the lead ions dissolved in the solution are re-precipitated. 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 dissolution of solder and the reprecipitation phenomenon of lead in the alkaline stripping solution are easily confirmed.

Japanese Unexamined Patent Publication (Kokai) No. 63-Showa showing 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. For actual work, generally, spray pressure of 1-2 kg / c,
In many cases, a spray method is used in which a stripping solution at a temperature of 40 to 50 ° C. is brought into contact with a substrate being conveyed using a conveyor to strip the water-soluble resist. 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 Pharmaceutical Co., Ltd., trade name, which is a reducing agent-containing drug corresponding to the method disclosed in JP-A-63-183445) is used. ) To the stripper,
200 cm ² substrate (solder area: 25%) dry film HF450 (Hitachi Chemical Co., Ltd., trade name)
After peeling, the lead ion in the liquid was measured, and the concentration was 300 to 400 ppm. The authors have found that when the amount of lead ions in the stripping solution becomes about 400 ppm, precipitation of lead on the substrate surface begins to be visually observed, and the residual copper causes residual copper in the subsequent alkali etching.

[0012] Therefore, as a result of intensive studies, as lead ions increase in the solution, dissolution is 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 of the tests showed that when lead ions were present in the solution, the dissolution increased (the dissolution current value was measured. ), It was found that a sufficient suppression effect cannot be obtained. It is presumed that the reason why the dissolution is accelerated in the presence of lead ions is that the lead reprecipitation reaction described above is a counter electrode reaction of corrosion and dissolution. Also, when the dissolution current was measured, the lead ions in the liquid were 50 to 100 pp.
In the case of m, although it was not always possible to visually confirm the precipitation of lead, it was found that such a dissolution acceleration phenomenon occurs. 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.

Then, as a result of studying a method of forming a complex with lead ions and suppressing the precipitation of lead, it was found that adding triethyl phosphate to the stripping solution was effective. As a result of adding triethyl phosphate to the stripping solution, it is possible to prevent a defect such as a wiring portion being etched by a subsequent alkali etching (a chipping or a disconnection defect). Practically, the amount of triethyl phosphate added is 0.5 g / l or more. Moreover, since adding an unnecessarily large amount is disadvantageous in terms of cost, 100 g / l is the practical maximum addition amount. Practically, the more desirable range of the addition amount is 1.0 to 50 g / l.

Furthermore, at least one of aminoguanidine, hydrazines, sulfurous acid, dithionous acid or salts thereof, borohydride, carbazic acid ester, thiourea dioxide, sulfinic acids, sulfoxy acids, hydrazides, and semicarbazide salts is used. Further effects can be obtained by adding them. For aminoguanidines, aminoguanidine bicarbonate, aminoguanidine sulfate,
Aminoguanidine hydrochloride or the like can be used. For hydrazines, hydrazine hydrate, monomethylhydrazine,
Dimethylhydrazine etc. can be used, and as its salt,
Hydrazine sulfate, hydrazine carbonate and hydrazine hydrochloride can be used. As the sulfite, sodium sulfite or potassium sulfite can be used. As the dithionite salt,
Sodium hydrosulfite, potassium hydrosulfite, and ammonium hydrosulfite can be used. As the borohydride, dimethylamine borane, sodium borohydride or potassium borohydride can be used. As the carbazate ester, methyl carbazate (alias: methyl carbazate) or ethyl carbazate (alias: ethyl carbazate) can be used.
Formamidine sulfinic acid is used as sulfinic acid, and sodium formaldehyde sulfoxylate (also known as Rongalit) is used as sulfoxy acid.
Sodium hydroxymethanesulfonate) can be used. As the hydrazides, carbohydrazide, acetohydrazide and isonicotinic acid hydrazide can be used.
As the semicarbazide salt, sulfuric acid semicarbazide or hydrochloric acid semicarbazide can be used. Since thiourea dioxide is decomposed in an alkaline solution to form formamidinesulfinic acid, the same effect as that of formamidinesulfinic acid can be obtained.

The above compound shown as the second additive is
All of them show a reducing effect in the stripping solution, and the addition amount depends on the reducing equivalent of these compounds and the life (duration of the reducing effect). However, from the practical viewpoint of solubility and cost, the desirable addition amount is 0.01 to 10
It is 0 g / l. When a plurality of second additives are used, the term "added amount" should be read as "total added amount". In practical use, the more desirable range of addition amount is 0.
It is 05 to 50 g / l.

Generally, disodium hydrogen phosphite and sodium phosphinate (also known as sodium hypophosphite), which are known as reducing agents, do not show sufficient reducing properties in the stripping solution, and No dissolution inhibiting effect (measurement of dissolution current) was also obtained. The reason for this is the pH of the stripper
Under the conditions, it is considered that the reduction life is extremely short such as several minutes or less. Regarding sodium thiosulfate, the reduction life was obtained to some extent, but the dissolution inhibiting effect was not obtained. It is considered that this is because sodium thiosulfate has a low reducing ability and is insufficient for suppressing dissolution. In addition, aldehydes such as formaldehyde, terephthalaldehyde acid, o-phthalaldehyde acid, benzaldehyde-osulfonic acid, terephthalaldehyde and benzaldehyde 2,4 disulfonic acid have extremely short life as a reducing agent in the stripping solution. After 30 minutes or less, the amount of the reducing agent (measured by redox titration with iodine) was 1/10 or less of the value calculated from the initial dose, which was not practical. The phenols gallic acid, ethyl gallate, n-propyl gallate, methyl gallate, pyrogallol, sodium p-hydroxybenzenesulfonate,
With 2,4-xylenol, the reduction life was short and it was not practical. Regarding aminoguanidine,
Although a reducing effect can be obtained in the stripping solution, guanidines having no amino group such as 1,1,3,3 tetramethylguanidine and guanidine sulfate were not effective and were not suitable. As described above, the reducing substances that are effective when added to the stripping solution are very limited as shown in this patent.

[0017]

In the conventional method for suppressing the dissolution of the solder in the stripping solution, the effect was obtained under the standing condition. However, under the condition that a new solution is constantly in contact with, such as a spray, the dissolution of the solder is larger than expected, and as a result, the lead ions in the stripping solution increase as the substrate is processed.
The present invention has been achieved by obtaining knowledge that the effect of the conventional dissolution suppressing method is inhibited even in the presence of 100 ppm of lead ions. In the present invention, by adding triethyl phosphate as a specific substance capable of forming a complex with a metal ion to a stripping solution, a lead ion is blocked, or a copper surface is blocked, and a dissolution suppressing effect of solder plating can be obtained. It is thought that Among phosphoric acid esters, the present invention has been completed based on the fact that this effect is specifically obtained with triethyl phosphate. Also,
A specific reducing agent was added in order to obtain a further dissolution suppressing effect. In the method of adding only a known reducing agent,
A sufficient effect was not obtained due to the action of the lead ions that melted from the solder plating. However, in the case of the present invention, the action of precipitating lead ions is prevented by the substance capable of forming a complex with the metal ions, and as a result, the dissolution suppressing effect by the addition of the reducing agent can be obtained. Here, as one of the reasons why the melting of the solder is suppressed by the reducing agent, it is estimated as follows. The oxygen demand reaction is a reaction in which the metal (lead, tin) in the solder dissolves in ions such as zinc acid, lead acid, stannous acid, and stannic acid. The reducing agent added to the stripper is
It reduces dissolved oxygen in the liquid and reduces the dissolved oxygen concentration in the liquid. Therefore, the melting reaction of the solder is suppressed. Actually, the dissolved oxygen concentration was measured with some reducing agents.
As a result, sodium hydrosulfite, sodium sulfite, formamidinesulfinic acid and hydrazine showed a decrease in dissolved oxygen concentration at room temperature. In addition, from the measurement of the melting current value, the effect was small at room temperature, but
Sodium aldehyde sulfoxylate, aminoguanidine sulfate, sodium borohydride, etc., which had a dissolution inhibiting effect at 0 ° C, did not show much decrease in dissolved oxygen concentration at room temperature, but showed a large decrease at 50 ° C. Was given. Thus, there was a correlation between the decrease in dissolved oxygen concentration due to the addition of the reducing agent and the effect of suppressing the dissolution of solder. As is clear from the above, the present invention solves the problems of lead precipitation and dissolution at the same time.

[0018]

【Example】

(Examples and Comparative Examples of Dissolution Inhibiting Additive) In a NaOH aqueous solution (NaOH concentration: 40 g / l), a lead concentration of 150 m
Lead sulphate is mixed so that it becomes g / l (150ppm),
After stirring for about 2 hours, the lead sulfate was completely dissolved and a solution was prepared. 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 form an electrode for measuring a 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. The measurement is at room temperature (about 20 ° C)
The liquid was stirred with a magnetic stirrer. In addition, 0.5 g of the additive shown in Table 1 was added in a small amount (2 to 3 ml).
A solution dissolved in an aqueous solution of NaOH (NaOH concentration: 40 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 adding the additive (additive concentration: about 10 g / l) was reduced by 20% or more compared to the current value before adding, ◯, the current value decrease was less than 20%, or vice versa. Table 1 shows the increase
(Example: Table 1-1, Comparative example: Table 1-2). In addition, in almost all the cases of ×, no decrease in current value was observed. In particular, regarding the sulfur-containing compounds of Comparative Examples 22 to 25, the nitro compounds of Comparative Examples 34 to 37, and the sodium bromate of Comparative Example 56, it is possible to add these compounds to a sodium hydroxide solution containing no lead ion. , Which resulted in a large increase in the melting current and, on the contrary, accelerated the melting of the solder.

[0019]

[Table 1]

(Examples and Comparative Examples of Second Additive) Next, the dissolution inhibiting effect of the second additive (reducing agent) was examined.
The presence or absence of the effect was confirmed by measuring the melting current while stirring the liquid with a magnetic stirrer while using the solder and the copper electrode while keeping the liquid temperature at 50 ° C. More specifically, 0.2 g of a reducing agent previously dissolved in 10 ml of an aqueous NaOH solution (NaOH concentration: 40 g / l) was added at 50 ° C.
The solution was heated to 50 ° C.
It was performed by adding to 0 ml of an aqueous NaOH solution (concentration: 40 g / l) containing triethyl phosphate (concentration: 10 g / l). The results are shown in Table 2. In the evaluation, when the addition of the second additive was observed, a current value reduction of 20% or more was observed.

[0021]

[Table 2]

(Effect of Lead Precipitation Suppression) A copper-clad laminate was exposed and developed using a water-soluble dry film HF450 (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 a NaOH aqueous solution containing 400 ppm of lead ions and additives, 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 3 (Examples: Table 3-1, Comparative Examples: Table 3-2, Table 3-3).
It was shown to.

[0023]

[Table 3]

[0024]

When the water-soluble resist is stripped with an alkaline stripping solution, by applying the present invention, the dissolution of solder plating can be suppressed and the precipitation of lead can also be suppressed. Therefore, it is possible to form a good wiring without a wiring defect. As another effect, the stripping solution used in this method can use an inexpensive inorganic alkali such as sodium hydroxide or potassium hydroxide in order to obtain a strong alkali. Further, 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. This reduces the cost of processing and also
Since it is not necessary to use an organic alkali, waste liquid treatment is easy.

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[Procedure amendment]

[Submission date] April 28, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Tin and lead, which are the constituent metals of the solder used for the etching resist of copper, dissolve at pH 13 or above. It is noted that Kagaku Dojin, 1984, "Introduction to Corrosion and Corrosion of Metals," p242, FIGS. "Tin potential-p
H diagram ”, FIGS. 17-12 in p243,“ lead potential-pH diagram ”, and the like. Actually, a high-density solder plating pattern with a wiring width and a space width of about 100 to 150 μm was formed on the copper surface, and 400 pp
It was observed that when a droplet of about 40 g / l sodium hydroxide aqueous solution containing lead ions of m was dropped, the exposed part of copper discolored to gray after being left for several minutes at room temperature.
The authors have found it. In addition, lead is detected when this gray portion is analyzed. The reason for this is that the dissolution of the solder plating metal component and the reprecipitation 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 dissolution of solder and the reprecipitation phenomenon of lead in the alkaline stripping solution are easily confirmed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Japanese Unexamined Patent Publication (Kokai) No. 63-Showa showing 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. For actual work, generally, spray pressure of 1-2 kg / cm ²
In many cases, a spray method is used in which a stripping solution at a temperature of 40 to 50 ° C. is brought into contact with a substrate being conveyed using a conveyor to strip the water-soluble resist. 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.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Actually, using a spray type water-soluble resist stripping device, OPC Parsori (manufactured by Okuno Pharmaceutical Co., Ltd., trade name, which is a reducing agent-containing drug 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 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 The authors have found that when the amount of lead ions in the stripping solution becomes about 400 ppm, precipitation of lead on the substrate surface begins to be visually observed, and the residual copper causes residual copper in the subsequent alkali etching.

Claims (3)

[Claims] 1. A plating resist is formed on a substrate laminated with copper foil with a water-soluble resist such as a dry film,
A method for stripping a water-soluble resist, which comprises performing solder plating and stripping the water-soluble resist with a strong alkaline aqueous solution, wherein the stripping solution contains triethyl phosphate in an amount of 0.5 to 100 g / l. . 2. As a second additive to the stripping solution, aminoguanidine, hydrazines, sulfurous acid, dithionous acid or salts thereof, borohydrides, carbazates, thiourea dioxide, sulfinic acids, sulfoxy acids. At least one of hydrazides and semicarbazide salts
The method for stripping a water-soluble resist according to claim 1, wherein the method comprises 1 to 100 g / l. 3. The method for stripping a water-soluble resist according to claim 1, wherein the stripping solution is brought into contact with the substrate by spraying to strip the water-soluble resist.