JPH0826443B2 - Partial surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] When a material to be treated is partially immersed in a treatment liquid and subjected to partial surface treatment, the treatment liquid is prevented from crawling up due to a capillary phenomenon, and fluctuations in the liquid surface of the treatment liquid are prevented. For the purpose of absorption, the object to be treated (2) continuously formed in a strip shape is immersed in a treatment liquid (5) having a free surface at a part of the lower part in the width direction of the strip, and only the soaked portion is obtained. In the surface treatment method of applying a desired surface treatment to two, the two round wire rods (3a, 3b) made of a resin material are parallel to the free surface of the treatment liquid, are in contact with each other, and are substantially half of the lower side of the round wire rod. Are arranged so as to be immersed in the treatment liquid, and the object to be treated (2) is inserted in such a manner that both sides are contacted and sandwiched between the oppositely arranged round wire rods so that they can be moved between the round wire rods. To

[Industrial applications]

The present invention relates to a method for manufacturing a lead frame of an electronic component, and more particularly to improving the accuracy of a partial surface treatment method such as partial plating or partial etching applied to high density lead terminals and the like.

In recent years, the number of signal lead-out lead terminals has increased and the arrangement pitch thereof has become finer as electronic components have become highly integrated.

In order to reduce the cost and improve the characteristics, such a dode terminal is partially subjected to partial surface treatment such as gold plating or solder plating, but with the above miniaturization, there is an increasing demand for a highly accurate partial surface treatment method. It's coming.

[Conventional technology]

As a method of partial surface treatment (partial plating, partial etching, etc.), a method of bringing only a desired portion of an object to be treated (metal) into contact with a treatment liquid has been widely used.

FIG. 3 is a diagram showing an intermediate member of a lead terminal of an electronic component.

In the figure, reference numeral 2'denotes an intermediate member to be surface-treated, which is formed by continuous pressing of a metal strip and has a terminal portion 21a which is soldered to a printed board or the like and a lower portion which is bonded to an electronic component chip by bonding. Bonding section 21b
The strip-shaped lead terminals 21 each having the above are connected at both ends thereof by the frame portion 22 having the guide holes 23.

A predetermined number (10 in the figure) of lead terminals 21 are formed as a group for one electronic component at a pitch equal to the terminal pitch of the final completed electronic component.
It is formed continuously at a pitch equal to 23.

The intermediate member 2'pressed as described above is passed through a surface treatment device to perform a desired surface treatment, for example, the terminal portion 21.
For example, the solder plating suitable for soldering is applied to a, and the bonding portion 21b is subjected to bonding gold plating.

In such a case, an immersion partial treatment method is employed in which a partial treatment is performed by immersing only a portion requiring treatment in a treatment liquid in a treatment tank which is in charge of a predetermined treatment step of the surface treatment apparatus.

[Problems to be solved by the invention]

In the above conventional immersion partial treatment method, the boundary of the partial treatment is determined by the depth of immersion in the treatment liquid in the object to be treated, so that the position of the liquid surface of the treatment liquid with respect to the object to be treated is controlled to be strictly constant. However, due to the limit of sensitivity of the liquid level sensor, it was difficult to suppress the fluctuation of the surface level of the processing liquid to ± 0.5 mm or less even in the stationary bath.

Also, due to the recent increase in the density of electronic parts, the arrangement pitch of the lead terminals has been reduced to about 0.6 mm, and the width is
If 0.25 mm lead terminals are arranged at the above pitch, the gap between the lead terminals will be extremely small, 0.35 mm.

When an object to be treated made of a metal material having such a minute gap is immersed in the treatment liquid halfway, as shown in FIG. 4 showing the rising of the treatment liquid, a predetermined liquid surface 51 is generated due to the capillary re-tube phenomenon. On the other hand, the liquid level rises in the gap portion. At the central portion (C portion) of the terminal group, the gap between the adjacent terminals is small, and thus the liquid level rise is large, and at the terminal (D portion) at the end of the group, the gap with the adjacent group is large, and thus it is small.

Therefore, the height of wetting with the treatment liquid is different in the same terminal group, so that the position of the boundary portion of the surface treatment varies.

Due to the above two reasons, it is impossible to keep the position of the boundary within ± 1 mm with the conventional partial surface treatment method by the immersion method, and the fluctuation of the boundary along the length direction of the lead terminal is ± 1 mm.
There is a problem that it cannot be applied to the lead terminal surface treatment process of the latest high-density electronic parts, which requires about 0.2 mm.

[Means for solving problems]

According to the present invention, the above-mentioned problems are caused by immersing the object to be treated (2) continuously formed in a strip shape in the treatment liquid (5) having a free surface at a part of the lower portion in the width direction of the strip, In the surface treatment method of applying a desired surface treatment only to the immersed portion, the two round wire rods (3a, 3b) made of a resin material are parallel to the free surface of the treatment liquid, are connected to each other and face each other, and About half of the sides are arranged so as to be immersed in the treatment liquid, and the object to be treated (2) is inserted in such a manner that both sides are in contact and sandwiched between the oppositely arranged round wires, and It is solved by a partial surface treatment method characterized by being moved.

[Action]

In the present invention, the two round wire rods are arranged on the free surface of the treatment liquid in a state where they are in contact with each other such that the lower half of each of them is immersed in the treatment liquid. The object to be processed is inserted between the wires so that the boundary line of the desired processing surface is located. As a result, one surface of the processing surface is connected to one round wire rod, and the other surface of the processing surface is connected and held to the other round wire rod, respectively.

Therefore, even if the treated liquid level fluctuates in such a state, if the fluctuation is within the diameter range of the round wire, the liquid in the portion sandwiched between the two round wire rods, that is, the portion in which the object to be treated is immersed. The surface will be kept at the center of the wire.

Further, since the round wire is formed of a resin material having a small surface tension, the liquid surface of the portion sandwiched by the two round wires is regulated, and the difference in the treatment liquid due to the capillary phenomenon is small. Even if the surface to be processed in the target area is a comb shape, there is almost no difference in the height of the rising of the processing liquid between the edge part and the central part, and the environmental line of the processing surface does not occur. Is constant.

Furthermore, in the present invention, since the round wire is made of a resin material, it is flexible and easy to adapt to the object to be processed,
Stable contact can be obtained, and the surface of the object to be treated is not damaged, and the movement of the object to be treated between the two round wire rods is not unreasonable. Moreover, since it is a round wire, it is easy to manufacture and inexpensive, and when the round wire is damaged or worn, it can be easily replaced.

In addition, a surfactant is used as an additive in the treatment liquid, especially the plating liquid, but in the case of the plating treatment, the treatment is performed by further increasing the temperature of the plating liquid from the surface of the object to be treated or at the plating liquid inlet to the plating tank. Bubbles tend to be generated in the liquid, and it is very difficult to eliminate the generated bubbles, and if partial treatment of the continuous workpiece is carried out in such a state, the bubbles will not be defoamed but will adhere to the workpiece and move. become.

However, in the present invention, since the round wire is used and the round wire and the object to be processed are in contact with each other, air bubbles do not enter the contact position, and the surface of the round wire and the object to be processed below the contacting position. The processing solution volume formed with the object surface is small,
On the other hand, since most of the liquid surface is a free surface, the bubbles rising along the surface of the object to be processed easily move to the outside of the round wire, and the adhesion of the bubbles to the surface to be processed becomes very small. The round wire of the book serves as a shield that separates the air bubbles floating on the liquid surface from the object to be treated.

Further, by changing the diameter of the round wire rod, it becomes possible to cope with the degree of fluctuation of the liquid surface and the accuracy of the boundary line of the processing surface.

〔Example〕

 Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 is a principle view of a partial surface treatment method according to the present invention, FIG. 2 is an enlarged view of a liquid surface portion, FIG. 2 (a) is a partially cutaway side view, and FIG. 2 (b) is It is an AA sectional view in (a).

In FIG. 1, reference numeral 1 is a processing tank which constitutes a part of a surface processing apparatus, and a processing solution 5 such as a plating solution or an etching solution.
Are stored so that the liquid surface 51 thereof has a predetermined level (height).

Reference numeral 2 is an object to be surface-treated as a final process of forming the lead terminals of the electronic component, which are arranged at a fine pitch of the terminals 21 corresponding to the number of lead wires of one electronic component. The groups are connected by the upper frame portion 22 to form a comb-shaped band, which is immersed in the treatment liquid 5 to a predetermined depth.

Then, in contact with the liquid surface 51 of the treatment liquid, the round wire rods 3a, 3b made of a resin such as tetrafluoroethylene that are easy to manufacture and inexpensive are placed in the treatment liquid. In this case, the round wire is flexible because it is made of a resin material, and it is arranged so as to contact and face each other on the surface of the processing liquid, and the object to be processed is inserted between the round wires, and the both sides of the object to be processed are round wire materials. Is contacted and pinched.

FIG. 2 is an enlarged view of the liquid surface portion for explaining the dimensional relationship of various elements in the case of this embodiment. The arrangement pitch p of the terminals 21 is 0.6 mm, the width w of the terminals is 0.25 mm, Gap s between adjacent terminals is 0.35 mm, terminal thickness t is 0.15 mm, wire rods 3a, 3b
Has a diameter of 1 mm.

In the above configuration, it is relatively easy to keep the relative positional relationship in the height direction between the object to be processed 2 and the round wire rods 3a, 3b at a desired height and with high accuracy by a holding means (not shown) relatively easily. It is possible. As shown in FIG. 2B, the height of the liquid surface 52 between the two round wire rods 3a and 3b is almost at the center of the round wire rod, and the height is within the range shown by the dotted line in FIG. Even if the entire liquid level 51 changes within the same range (equal to the diameter d), the part of the liquid level 52 is maintained at the above-mentioned constant height position.

Furthermore, for example, in the same terminal group consisting of 10 terminals, due to the effect of the water-repellent Teflon wire which is in contact with the terminals in the vicinity of the liquid surface 52, the gap between the adjacent terminals due to the capillary phenomenon is also generated in the central portion of the terminal group. Crawling of the processing liquid into the gap is reduced, and there is almost no difference in the wetting height with respect to the terminal at the end.

Therefore, unlike the above-mentioned conventional example, there is no variation in the boundaries of the surface treatment parts within the same group, and high-precision partial surface treatment is possible.

Further, in the surface treatment, bubbles are generated in the treatment liquid on the surface to be treated or the like, and in this case, even if there are bubbles rising along the surface to be treated, the surface of the substance to be treated is clearly seen as shown in FIG. 1 (b). And the round wire surface are in contact with each other, bubbles do not enter between them and the volume of the processing liquid portion formed between both surfaces is small. The air bubbles discharged to the outside of the round wire rod and levitated, and the floating air bubbles enter the atmosphere with a wide free surface liquid level, and the bubbles remaining on the lower surface of the round wire rod and the object to be treated become few, and the air bubbles adversely affect the surface treatment. It has less effect.

In addition, according to the experimental results to which the configuration of the present embodiment is applied,
Using a cyanide-based organic acid solution as a treatment liquid, a lead terminal to be treated, which was entirely plated with gold (Au) of 3 μm on a nickel base, was partially immersed to partially remove the gold plating film on the surface of the immersed portion ( As a result of etching, the fluctuation of the boundary position of partial peeling could be suppressed to ± 0.2 mm even under the normal liquid surface height control (± 0.5 mm). This value corresponds to an accuracy improvement of 5 to 10 times compared with the boundary position variation value of 1 to 2 mm for gold peeling by conventional partial immersion without using a round wire.

〔The invention's effect〕

According to the partial surface treatment method of the present invention, when a part of an object to be treated is immersed in a treatment liquid to perform a plating treatment or an etching treatment, the boundary line between the treated portion and the non-treated portion can be minutely formed with high accuracy. It is possible to suppress variations and it is possible to supply lead terminals of high-density electronic parts at low cost, and the effect is remarkable.

[Brief description of drawings]

FIG. 1 is a principle diagram of a partial surface treatment method according to the present invention, FIG. 2 is an enlarged view of a liquid surface portion, FIG. 3 is a view showing an intermediate member of a lead terminal of an electronic component, and FIG. FIG. 4 is a diagram showing the rising of the treatment liquid. In the figure, 1 ... Treatment tank, 2 ... Object to be treated, 2 '... Intermediate member, 21
...... Lead terminal, 21a ...... Terminal part, 21b …… Bonding part, 22 …… Frame part, 3a, 3b …… Wire material, 5 …… Processing liquid, 51 …… Liquid level, 52 …… Liquid level .

Claims (1)

[Claims] 1. An article to be treated (2) continuously formed in a strip shape is dipped in a treatment liquid (5) having a free surface at a part of a lower portion in the width direction of the strip to form the dipped portion. In the surface treatment method in which only the desired surface treatment is performed, the two round wire rods (3a, 3b) made of a resin material are parallel to the free surface of the treatment liquid, are in contact with each other, and face each other. Half of them are arranged so as to be immersed in the treatment liquid, and the object to be treated (2) is inserted in such a manner that both sides thereof are in contact and sandwiched between the oppositely arranged round wire rods and moved between the round wire rods. A partial surface treatment method characterized by the above.