JPH07316845A - Surface treating solution for silver plated member - Google Patents

Abstract

PURPOSE:To obtain a surface treating soln. less liable to cause the damage to a spot Ag plated part and to extremely facilitate process control. CONSTITUTION:This surface treating soln. has such a compsn. as the rate of removal of silver plating becomes low in accordance with the reduction of the ratio of the area of a silver plated part to the area of an exposed base or has such a compsn. as the rate of removal of silver plating is kept constant independently of the ratio of the area of a silver plated part to the area of an exposed base. For example, this surface treating soln. has a compsn. contg. 0.5-2mol/l alkali cyanide as a principal component, 0.1-0.2mol/l alkali ferricyanide or oxidizing agent as a substitute for the alkali ferricyanide, 0.5-20% alkali hydroxide and 0.01-1.0% org. inhibitor. The addition of the alkali ferricyanide or oxidizing agent can be made unnecessary by impressing positive voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment solution for a silver (Ag) plated member, and particularly to a plate material having partial Ag plating, for example, a surface treatment suitable for dissolving and removing leakage silver of a lead frame. Regarding liquid.

[0002]

2. Description of the Related Art In a manufacturing process of a material having a partial Ag plating such as a lead frame, there is an "Ag plating peeling process" step. That is, as shown in FIG. 2, the spot Ag plating portion 2 is provided on the base plate 1, but an extremely thin leak Ag plating portion 3 is inevitably present around the spot Ag plating portion 2 due to the Ag plating solution leaking from the plating mask. , Ag
In this step, Ag of the plated portion 3 is removed by melting and peeling.

Here, the area of the Ag-plated portion (including the leakage Ag-plated portion 3) and the exposed area of the base (for example, copper (C
The ratio with u)) is such that it is 10/1 immediately after Ag plating, 1/1 during immersion in the Ag plating stripping solution, and the final stage thereof changes about 1/10 every moment. Conventionally, a surface treatment liquid containing an alkali cyanide as a main component has been used as the Ag plating stripping liquid (for example, Japanese Patent Publication No. 55-9463). According to this, the Ag plating peeling rate changes from small → medium → large corresponding to the change of the above ratio, and the spot Ag plated portion 2 is excessively melted and damaged (the thickness is reduced and the surface roughness is increased). There are not a few cases where In addition, it was difficult to adjust the liquid.

The composition of the conventional surface treatment liquid is as follows.

(1) 0.2-1 mol / l of alkali cyanide salt (2) 0.2-1 mol / l of ferricyanide salt (3) 10-40% or more of alkali hydroxide salt (4 ) Organic inhibitors are generally more than 1%

[0006]

As described above, in the conventional surface treatment liquid for a silver-plated member containing alkali cyanide as a main component, the ratio of the Ag-plated partial area / underlying exposed area changes momentarily. As a result, the Ag plating peeling rate changed from small to medium to large, and there were many cases where the spot Ag plated portion 2 was excessively dissolved and damaged, and it was difficult to adjust the solution.

The reason why this type of dissolution behavior occurs is explained very simply. That is, the base (eg Cu) and A
It is known that when the g-plated part is electrically connected and immersed in a solution, the dissolution rate of both materials is determined as an electrochemical interaction called galvanic corrosion. The surface area ratio of each material has a strong influence. If the area ratio of Ag (noble potential material) and Cu (base potential material) is 10/1, 1/1, 1/10.
, The dissolution rate of the noble potential material Ag normally changes from small to medium to large. It is theoretically known that this is the same even when Fe is replaced with Ag and Zn is replaced with Cu and the corrosive liquid is, for example, 1% sulfuric acid, seawater, or tap water. ing.

Therefore, as long as the conventional Ag plating stripping solution is used, the above-mentioned dissolution behavior can be said to be very general, and as long as that solution is used, the Ag spot portion is likely to be damaged at the final stage.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a surface treatment liquid for a silver-plated member, in which partial damage is basically unlikely to occur and process control is extremely easy. .

[0010]

A first aspect of the present invention is a surface treatment of a silver-plated member having a composition such that the removal rate of silver-plating peeling decreases as the ratio of the silver-plated partial area / underlying exposed area decreases. It is a liquid.

A second aspect of the present invention is a surface treatment liquid for a silver-plated member having a composition such that the removal rate of silver-plating peeling is substantially constant regardless of the ratio of the silver-plated partial area / underlying exposed area.

A third aspect of the present invention comprises a surface treatment solution for a silver-plated member, which has the following composition. (1) 0.5 to 2 mol / l alkali cyanide (2) 0.1 to 0.2 mol l ferricyanide or an alternative oxidant (3) alkali hydroxide. 5 to 20% (4) The organic inhibitor is set to 0.01 to 1.0%.

The lower limit of the alkali cyanide salt is 0.5 mol / l from the viewpoint of giving a large dissolution and peeling rate of Ag, and the upper limit is to prevent the ratio of the dissolution rate of Ag and Cu from unnecessarily decreasing. To 2 mol / l. The lower limit of the ferricyanide alkali salt or an oxidant instead thereof is 0.1 mol / l from the viewpoint of increasing the dissolution and peeling rate of Ag,
The upper limit is 0.2 mol / l in order to prevent the ratio of the dissolution rate of Ag and Cu from unnecessarily decreasing. The lower limit of the alkali hydroxide salt is 0.5% from the viewpoint of preventing the dissolution rate of Cu and Ag from decreasing, and the upper limit is 20% from the viewpoint of preventing discoloration after the material is dissolved. The lower limit of the organic inhibitor is 0.01% from the viewpoint of preventing the lowering of the dissolution rate of the Cu underlayer with respect to Ag, and the upper limit thereof is 1.0% mainly in the economical sense because the effect is saturated.

Here, the alkali cyanide salt is sodium cyanide, potassium cyanide or the like. The ferricyanide alkali salt is sodium ferricyanide, potassium ferricyanide, or the like. The oxidizing agent which replaces the ferricyanide alkali salt is hydrogen peroxide solution, potassium persulfate and the like. The alkali hydroxide salt is sodium hydroxide, potassium hydroxide or the like.

A fourth aspect of the invention is the same as the third aspect (2).
Of the alkali ferricyanide salt or its substitute oxidizing agent is set to 0.

In a fifth aspect of the invention, in the third and fourth aspects, the organic inhibitor is ethylenediamine, triethanolamine, piperazine, benzotriazole,
The succinimide, methylaminomercaptin, phenylmercaptoacetamide, aminorhodanine, thiouramyl, thiourazole, and thiohexahydropyridine are contained alone or in combination.

The present invention is not limited to the surface treatment liquid containing an alkali cyanide as a main component, and a treatment liquid containing any component may be used as long as it exhibits the above-mentioned dissolution behavior. For example, it can be applied to a processing solution containing no alkali cyanide salt.

[0018]

The preferred surface treatment liquid for Ag-plated members is that when the Ag area is large, the Ag dissolution rate is high, then gradually decreases, and finally when the Ag area becomes small, A
g lysis is either stopped or reduced to a negligible degree (see bottom column of Figure 2). That is, if the treatment liquid has a composition that behaves in such a manner, partial damage is basically unlikely to occur, and process control becomes extremely easy.

Although this is a little inferior in performance, this also applies to a surface treatment solution having a composition in which the removal rate of silver plating peeling is substantially constant regardless of the ratio of the silver plating partial area / underlying exposed area.

Next, the reason why the composition of the surface treatment liquid for the silver-plated member is specifically set as described above will be explained based on experiments.

FIG. 1 shows three kinds of surface treatment liquids a, b and c for three samples in which an Ag plate and a Cu plate are connected and the area ratio thereof is changed to 10/1, 1/1 and 1/10. It is the dissolution rate ratio of the Ag plate to the Cu plate when is used. Here, the compositions of the liquid a, the liquid b, and the liquid c are as follows.

Solution a: a mixed solution of 0.1% triethanolamine, 0.10 mol / l sodium ferricyanide, 10% sodium hydroxide, and 55 g / l sodium cyanide.

Solution b; triethanolamine 0.5%, sodium ferricyanide 0.2 mol / l, other than the same as solution a.

Solution c: triethanolamine 1%, sodium ferricyanide 0.5 mol / l, otherwise the same as solution a.

From FIG. 1, the dissolution rate of Ag and Cu is Na
A-c liquid composition excluding CN, NaCN concentration, sample combination,
It can be seen that it has changed in various ways.

From this, first, looking at the liquid c, the change in the ratio R of Ag dissolution rate / Cu dissolution rate is that the Ag / Cu area ratio is 1
There is a tendency that the number increases as it goes from 0/1 (○ mark), 1/1 (Δ mark), and 1/10 (□ mark). That is, c
As described with reference to FIG. 2, the liquid can be said to be a liquid that tends to be more likely to be melt-damaged at the spot Ag plated portion in the final stage of the actual process.

On the other hand, in the liquid b, the above three samples show almost the same R value, which can be said to be a liquid which is easier to use than the liquid c and whose process control is easy. Therefore, although the necessary condition is satisfied, the condition is not sufficiently satisfied in that the mark ○ and the mark Δ or the mark □ are not reversed.

In that respect, the liquid a shows a more preferable tendency, which is the reverse of the liquid c. Especially NaCN concentration is 20g / l
In the following, since the dissolution rate ratio is relatively large, it tends to be more preferable.

However, the only difficulty of the liquid a is that the absolute value of the dissolution rate is small, as shown in FIG. However, this point can be easily solved by taking measures such as prolonging the immersion time or raising the liquid temperature as a process configuration. In any case, as long as the treatment liquid of the present invention is used, even if the leak Ag plating area in each lead frame fluctuates to some extent, the leak Ag plating around the spot Ag plating is promptly dissolved and disappears, and the Ag spot portion is It hardly dissolves and the process control becomes extremely easy.

The above-mentioned dissolution behavior was accurately recognized in the liquid composition range shown in the third invention (corresponding to the liquids a and b in FIG. 1), and it was not always preferable if it was out of the respective component ranges.

Although the ferricyanide alkali salt was used as the oxidizer component in the third invention, if a positive voltage is applied to the non-treated film material instead, a similar effect can be expected, so that it is not always necessary. . Therefore, it is not necessary to contain an oxidizing agent as in the fourth invention.

Next, as a result of the same examination as the inhibitor for each of the chemicals of the fifth invention, it was confirmed that all of them were effective except for the large and small fluctuations of the effect.

Therefore, according to the present invention, the leakage Ag plated portion can be dissolved and removed, and the spot Ag plated portion can be soundly retained.

(1) Simplification of process management, labor saving of processes, unmanned management.

(2) The liquid management cost is reduced by reducing the liquid update frequency.

(3) Improving yield by improving product quality,
Cost reduction.

(4) Liquid composition cost is low because of low concentration of liquid composition components.

[0038]

【Example】

Example 1 Solution a was used as the surface treatment solution for the silver-plated member. The treatment conditions are a liquid temperature of 50 ° C and an immersion time of 15 seconds.
The actual leadframe was treated with very thin leaky Ag plated areas around the spot Ag plated areas.

As a result, compared with the conventional liquid (close to liquid c),
The surface roughness of spot Ag plated part is 1/10, Ag
The control value for the reduction of the plating film was in the range of 1/3.

(Embodiment 2) A lead frame whose Ag leakage area fluctuates greatly (1/50 to 2/3 times as much as the base material area) is flowed under the same process conditions as in Embodiment 1, and no trouble occurs. There wasn't.

(Comparative Example) A lead frame was run under the same process conditions as in Example 1 except that the liquid c was used. The lead frame immersion time and the liquid temperature were not finely changed according to the size of the Ag leakage area. Then, there is a problem that the Ag leak portion remains, and conversely, the Ag spot portion is melted and damaged.

[0042]

According to the present invention, the composition of the surface treatment solution is set so that the removal rate of the silver plating peeling becomes smaller as the ratio of the silver plating partial area / underlying exposed area becomes smaller, or Regardless of the ratio of the partial area to the exposed area of the undercoat, the removal rate of the silver plating peeling is set to be substantially constant, so that partial damage is basically unlikely to occur and the process control becomes extremely easy.

[Brief description of drawings]

FIG. 1 is an Ag plate and Cu according to an example of the present invention and a conventional example.
It is a figure which shows the dissolution rate ratio regarding NaCN density | concentration which made various solutions the parameter in the sample which connected the board,
The horizontal axis is NaCN (g / l), the vertical axis is Ag dissolution rate / Cu
It is the ratio R of the dissolution rate.

FIG. 2 is an explanatory diagram of a dissolution behavior of an Ag-plated portion in a partial Ag-plated plate material and an Ag-plating peeling removal rate related to the conventional method and the present invention.

[Explanation of symbols]

 1 Base plate (eg Cu) 2 Spot Ag plated part 3 Leakage Ag plated part

Claims (5)

[Claims] 1. A surface treatment liquid for a silver-plated member having a composition in which the rate of peeling and removing silver plating decreases as the ratio of the silver-plated partial area / underlying exposed area decreases. 2. A surface treatment liquid for a silver-plated member having a composition such that the removal rate of silver-plating peeling is substantially constant regardless of the ratio of the silver-plated partial area / underlying exposed area. 3. Alkali cyanide salt 0.5-2 mol / l
And 0.1 to 0.2 mol / l of an alkali ferricyanide salt or an alternative oxidant, and an alkali hydroxide of 0.5
˜20%, and organic inhibitor 0.01-1.0
%, A surface treatment liquid for a silver-plated member. 4. The surface treatment solution for a silver-plated member according to claim 3, which does not contain the alkali ferricyanide salt or an oxidant in place thereof. 5. The organic inhibitor contains ethylenediamine, triethanolamine, piperazine, benzotriazole, succinimide, methylaminomercaptin, phenylmercaptoacetamide, aminorodanine, thiouramyl, thiourazole, thiohexahydropyridine, either alone or in combination. The surface treatment liquid for a silver-plated member according to claim 3 or 4.