JP3124734B2 - Silver plating stripper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to a silver plating film (hereinafter simply referred to as "more silver") formed in a masking silver plating step by leaking to a masking portion where silver plating is not originally required. The present invention relates to a silver plating stripping solution for stripping silver plating, which does not adversely affect a required silver plating portion.

[0002]

2. Description of the Related Art In silver plating of an electronic component such as an IC lead frame, a method of masking a portion not requiring plating is generally used. However, even if masking is performed, deposition of silver plating on portions that do not require plating cannot be avoided. Usually, an alkaline stripping solution containing a cyan compound and an oxidizing agent as main components is used for stripping silver deposited on the unnecessary portion, which is called “mole silver”. However, in the case of using such a conventional stripping solution to remove "more silver", there is a disadvantage that the gloss of the surface of the silver plating portion, which is originally required, tends to change.

[0003] In general, the performance of the stripping solution of the conventional stripping solution gradually decreases due to the decomposition of components in the stripping solution over a long period of continuous use and the accumulation of dissolved metals and the like in the bath. Degradation has been reported. In this case, a certain amount of continuous operation can be realized by replenishing an appropriate replenishing solution. However, the conventional stripping solution is still limited to at most about 16 to 24 hours. The gloss change of the surface suddenly becomes so severe that there is an inconvenience that the bath must be renewed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-mentioned conventional problems and to provide a silver plating portion which is originally required. It is an object of the present invention to provide a silver plating stripping solution capable of stripping and removing unnecessary portions of silver called "molten silver" without changing gloss. Furthermore, by adding a predetermined component of the silver plating stripper to the silver plating stripper in use, the silver plating stripper can recover the performance of the silver plating stripper and realize continuous operation for an extremely long time. Is to provide.

[0005]

In order to solve the above-mentioned problems, a silver plating stripping solution of the present invention comprises an organic compound containing a nitro group, a cyanide compound, and a group V, VI, or VII element of the periodic table. Oxygen acid and / or a salt thereof.

Further, the content of the organic compound containing a nitro group is 3 to 200 g / L, and the content of the cyan compound is 5 to 200 g / L.
-100 g / L, and the content of the oxyacids and / or salts thereof of the Group V, VI, and VII elements in the periodic table is 0.003 to 2;
It is configured to be 0.0 g / L.

[0007]

Embodiments of the present invention will be described below in detail.

The silver plating stripper of the present invention comprises an organic compound containing a nitro group, a cyanide compound, and a periodic table V, VI, V
It is configured to contain a group II element oxyacid and / or a salt thereof.

Examples of the organic compound containing a nitro group (particularly, an aromatic compound) include nitrobenzoic acid such as paranitrobenzoic acid, metanitrobenzoic acid, and orthonitrobenzoic acid, and salts thereof (for example, sodium metanitrobenzoate and potassium metanitrobenzoate). ); Metanitrobenzenesulfonic acid and its salts (eg, sodium metanitrobenzenesulfonate, potassium metanitrobenzenesulfonate); metanitroaniline; and metanitrophenol. Among them, it is particularly preferable to use sodium metanitrobenzoate and sodium metanitrobenzenesulfonate.

The content of such a nitro group-containing organic compound in the silver plating stripping solution is preferably 3 to 200 g / L, more preferably 5 to 100 g / L. This value is
If the amount is less than 3 g / L, the peeling ability of “molar silver” becomes insufficient, which is not preferable. In addition, this value is 200 g / L
When the ratio exceeds the above, there arises a disadvantage that the gloss required for the surface of the silver plating portion, which is originally required, changes sharply.

As the cyanide compound contained in the silver plating stripping solution, sodium cyanide, potassium cyanide, calcium cyanide and the like are preferably used. The content of such a cyanide compound in the silver plating stripping solution is 5 to 100.
g / L, more preferably 10 to 50 g / L. If this value is less than 5 g / L, the peeling treatment capability of “Mole silver” becomes insufficient, which is not preferable. On the other hand, if this value exceeds 100 g / L, there is a disadvantage that the gloss of the surface of the silver-plated portion, which is originally required, changes sharply.

The periodic table V, which is contained in the silver plating stripper,
Examples of the oxygen acids and / or salts thereof of Group VI and VII elements include tungstic acid, sodium tungstate, molybdic acid, sodium molybdate, sodium chromate, potassium permanganate, sodium sulfate, sodium nitrate, ammonium phosphate, iodine Suitable examples include potassium acid, periodate, sodium chlorate, sodium bromate, potassium sulfate, sodium phosphate and the like. Among these, it is particularly preferable to use one or more selected from tungstic acid, sodium tungstate, molybdic acid, sodium molybdate and potassium iodate. Furthermore, it is optimal to use one or more selected from sodium tungstate and sodium molybdate in that the most stable performance is obtained. The content of such an oxygen acid and / or a salt thereof in the silver plating stripping solution is 0.003 to 20.0 g /
L, more preferably 0.01 to 1.0 g / L. If this value is less than 0.003 g / L, it becomes difficult to control the concentration and the peeling ability of “Mole silver” becomes insufficient, which is not preferable. This value is 20.0
If it exceeds g / L, there arises an inconvenience that the gloss required for the surface of the silver plating portion, which is originally required, changes sharply.

Further, the silver plating stripping solution of the present invention may contain other additives, for example, alkalis such as sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide, without departing from the effects of the present invention. It can also be contained.

The composition of the underlayer to which silver plating is applied is not particularly limited, and examples thereof include lead-frame materials such as iron-nickel alloys, copper alloys, stainless steels, and Kovar materials. Can be

[0015]

The present invention will be described below in more detail with reference to specific examples of the present invention.

(Embodiment 1) First, in order to evaluate the performance of the silver plating stripping solution of the present invention, a lead frame test piece (hereinafter simply referred to as spot silver plating) subjected to spot silver plating according to the following processing steps. This is referred to as “silver plating test piece”.

Processing steps for preparing silver-plated test pieces (1) Alkaline degreasing · Sodium carbonate ··· 10 g / L · Sodium metasilicate · · · 15 g / L · Sodium hydroxide · · · 20 g / L · Surfactant · · 3 g / L Conditions: 50 ° C, 5 minutes (2) Pickling ・ 36% hydrochloric acid ... 200mL / L Treatment conditions: Room temperature, 1 minute (3) Chemical polishing ・ 35% hydrogen peroxide ... 100mL / L ・ Ammonium hydrogen fluoride ... 50mL / L ・ Ammonium sulfate ・ ・ ・ 50mL / L Treatment condition: Room temperature, 1 minute (4) Pickling ・ 36% hydrochloric acid ・ ・ ・ 200mL / L Treatment condition: Room temperature, 1 minute (5) Copper strike ・ Cu cyanide ・ ・ ・ 60g / L ・ Cyan Sodium chloride: 80 g / L Rochelle salt: 50 g / L Potassium hydroxide: 15 g / L Potassium thiocyanate: 10 g / L Treatment conditions: 6 ℃, 2A / dm ^{2, 2} minutes (6) Spot silver plating composition 1-silver potassium cyanide ... 120 g / L-sodium nitrate ... 20 g / L, potassium carbonate ... 10 g / L Composition 2 & silver potassium cyanide ... 120 g / L · sodium nitrate ··· 20 g / L · potassium carbonate · · · 10 g / L · selenium oxide · · · 5 mg / L Treatment conditions: 60 ° C, 2 A / dm ² , 10 seconds (Note that spot silver plating was treated with the above composition 1. And a composition treated with the above-mentioned composition 2). Then, a silver plating stripper 1 of the present invention having the following bath composition was prepared.

Silver plating stripper 1 · potassium cyanide 30 g / L sodium metanitrobenzoate 10 g / L sodium tungstate 0.03 g / L Using the above silver plating stripper 1, the above “silver plating test piece” Was performed, and the time required for peeling the silver and the glossiness of the required surface of the silver-plated portion were measured in the following manner. The bath temperature of the silver plating stripper 1 was 40 ° C.

The time required for peeling the mole silver The time until the peeling of the mole silver was completely completed was visually judged.

The processing time (peeling time) within 60 seconds was evaluated as a usable range, and the processing time (peeling time) within 45 seconds was evaluated as a preferable working range.

The required glossiness of the surface of the silver-plated portion before and after the glossiness treatment was measured by a densitometer (a diffuse reflection type color densitometer "GAM RD-144 (S)" manufactured by GAM). The measurement mode was black.

The difference in gloss change before and after the treatment is ± 3
Those with 0% or less were evaluated as a usable range, and those with a difference in gloss change before and after treatment within ± 20% were evaluated as a suitable use range.

[0023] In the above (6) Spot silver plating process, the gloss of the initial (pre-release solution process) a silver plated portion treated with the treatment liquid composition 1 is 0.25, with a processing solution having the composition 2 Initial stage of treated silver plating (before stripper treatment)
Was 0.70 in glossiness.

Using the above-mentioned silver plating stripper 1, a test of the above-mentioned “silver plating test piece” for the peeling of silver was performed. As a result, the time required for the peeling of the silver was about 15 seconds, and the processing of the silver was extremely quick. Was completed. Also, the change in glossiness was 0.25 before processing, 0.25 after processing, and 0.75 before processing.
In the case of No. 0, the glossiness was hardly changed to 0.65 after the treatment, and it was confirmed that extremely good results were obtained.

Example 2 Next, an experiment was conducted to examine the effect of the concentration of a cyan compound (potassium cyanide) contained in the silver plating stripping solution of the present invention. That is, in the composition of the silver plating stripping solution 1 used in Example 1 above,
Samples in which only the concentration of potassium cyanide was variously changed (samples 2-1 to 2-9 in Table 2 below) were prepared.

With respect to each of these samples, the time required for peeling mole silver and the change in glossiness were determined as described above.

The results are shown in Table 1 below.

[0028]

[Table 1] From the results shown in Table 1, the preferred concentration range of the cyan compound is 5 to 100 g / L, more preferably 10 to 50 g.
/ L.

Example 3 Next, an experiment was conducted to examine the effect of the concentration of a nitro group-containing organic compound (sodium metanitrobenzoate) contained in the silver plating stripping solution of the present invention. That is, samples (Samples 3-1 to 3-11 in Table 2 below) were prepared in which only the concentration of sodium metanitrobenzoate was varied in the composition of the silver plating stripping solution 1 used in Example 1 above.

With respect to each of these samples, the time required for peeling mole silver and the change in gloss were determined in the above manner.

The results are shown in Table 2 below.

[0032]

[Table 2] From the results shown in Table 2, it was confirmed that the suitable concentration range of the organic compound containing a nitro group was 3 to 200 g / L, more preferably 5 to 100 g / L.

Example 4 Next, in the silver plating stripping solution of the present invention, the influence of the concentration of oxyacids or salts (sodium tungstate) of Group V, VI and VII elements contained in the stripping solution of the present invention is examined. An experiment was performed. That is, samples (Samples 4-1 to 4-12 in Table 3 below) were prepared in which only the concentration of sodium tungstate was varied in the composition of the silver plating stripping solution 1 used in Example 1 above.

For each of these samples, the time required for peeling the mole silver and the change in gloss were determined in the above-described manner.

The results are shown in Table 3 below.

[0036]

[Table 3] From the results shown in Table 3, the preferred concentration range of the oxyacids or salts thereof of Group V, VI, and VII elements is 0.003.
-20 g / L, more preferably 0.01-1.0 g / L
It was confirmed that it was.

(Example 5) The potassium cyanide of the silver plating stripping solution 1 of Example 1 was replaced with sodium cyanide (concentration 2).
0 g / L). Except for this, the silver plating stripping solution sample 5-1 was prepared in the same manner as the silver plating stripping solution 1 of Example 1. With respect to this sample 5-1, the time required for peeling mole silver and the change in glossiness were determined as described above. As a result, the time required for peeling the mole silver was about 15 seconds, and the processing of the mole silver could be performed very quickly. Also, the change in gloss was 0.25 before the processing, but 0.25 after the processing.
The gloss before the treatment was 0.70, and the gloss after the treatment was 0.65, and the glossiness hardly changed, and it was confirmed that extremely good results were obtained.

Example 6 The sodium metanitrobenzoate of the silver plating stripping solution 1 of Example 1 was changed to sodium metanitrobenzenesulfonate. Except for this, the silver plating stripper 6-1 was prepared in the same manner as the silver plating stripper 1 of Example 1. With respect to this sample 6-1, the time required for peeling mole silver and the change in gloss were determined in the above manner. As a result, the time required for peeling the mole silver was about 15 seconds, and the processing of the mole silver could be performed very quickly. The change in gloss was 0.25 before processing and 0.20 after processing.
60, respectively, the glossiness has hardly changed,
It was confirmed that extremely good results were obtained.

Example 7 The sodium tungstate of the silver plating stripper 1 of Example 1 was changed to various compounds as shown in Table 4 below. The concentration was also changed. Other than that,
Silver plating stripping solution samples 7-2 to 7-18 were prepared in the same manner as silver plating stripping solution 1 of Example 1. In addition, the thing using the sodium tungstate of Example 1 was also described as stripping liquid sample 7-1 so that comparison between compounds may become easy.

With respect to each of these samples, the time required for peeling mole silver and the change in glossiness were determined as described above.

The results are shown in Table 4 below.

[0042]

[Table 4] From the results shown in Table 4, the periodic table V, VI, V
By using an oxygen acid of Group II element or its salt,
It was confirmed that the time required for peeling the mole silver was shortened, and that the change in glossiness was extremely small.

Example 8 A long-term continuous operation experiment was performed using the silver plating stripping solution 1 of the present invention. That is, a long-term continuous operation experiment was performed in a form in which sodium tungstate and potassium cyanide were appropriately supplied to the silver plating stripping solution 1 according to the operation state. In the case of the silver plating stripping solution of the present invention, the gloss change after the silver plating process started to occur in operation for 16 to 24 hours, but at that time, the original performance of the stripping solution was improved by replenishing sodium tungstate. It was confirmed that recovery was possible and continuous operation for 100 to 150 hours could be realized. This is also a unique effect of the stripping solution of the present invention containing an oxyacid of a Group V, VI, or VII element and / or a salt thereof. Note that potassium cyanide was appropriately replenished, and no organic compound containing a nitro group (oxidizing agent) was replenished.

On the other hand, the conventional stripping solution containing a cyanide and an oxidizing agent already has
Although a satisfactory gloss cannot be obtained after the treatment, it is difficult to reduce the gloss level and to replenish the cyanide and / or the oxidizing agent, which are the components contained in the stripping solution, as appropriate. , Even if it operates continuously,
After about 24 hours of operation, the change in gloss of the silver plating became too severe, and the bath itself had to be renewed.

[0045]

The effects of the present invention are clear from the above results. That is, the silver plating stripping solution of the present invention comprises an organic compound containing a nitro group, a cyanide compound, and a periodic table V, V
It is composed of oxyacids of Group I and VII elements and / or their salts. Silver can be peeled off. Furthermore, by adding a predetermined component of the silver plating stripping solution to the silver plating stripping solution in use, the performance of the silver plating stripping solution can be recovered and continuous operation for an extremely long time can be realized.

Continued on the front page (72) Inventor Shigenori Emura 2-3-1, Yoshino-cho, Omiya City, Saitama Prefecture Inside the research department of Meltex Co., Ltd. (56) References JP-A-10-158867 (JP, A) JP-A-7- 316845 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 1/00 C23F 1/10-1/44 C25D 5/48

Claims (2)

(57) [Claims] 1. A silver plating stripper for stripping a silver plating film, comprising: a nitro group-containing organic compound; a cyanide compound; tungstic acid and its salts; molybdic acid and its salts.
Salt, chromic acid and its salts, permanganic acid and its salts
A silver plating stripper comprising at least one selected from the group consisting of a salt and a salt . 2. The content of the organic compound having a nitro group is 3 to 200 g / L, and the content of the cyan compound is 5 to 200 g / L.
~ 100 g / L, the tungstic acid and its salt,
Ribic acid and its salts, chromic acid and its salts,
At least one selected from gannic acid and its salts
The silver plating stripping solution according to claim 1, wherein the content of the seed is 0.003 to 20.0 g / L.