JPS5852034B2 - Partial plating method and device - Google Patents

Description

Detailed Description of the Invention The present invention is a partial plating method in which a plating solution is sprayed onto a surface to be plated to plate only a specific minute portion, and the plating solution generated between the surface to be plated and a plating injection nozzle is The present invention relates to a partial plating method and an apparatus for the same, which forcibly removes stagnation and improves plating efficiency by increasing plating current density.

Normally, when partially plating precious metals such as gold or platinum onto lead frames of integrated circuit elements or contacts of miniaturized electronic components, the common method is to spray a plating solution onto the surface to be plated. Conventional partial plating methods have disadvantageous problems such as poor plating quality and workability, and increased plating processing and equipment costs.

As a solution to this problem, the 10th patent application of 1972
No. 0772 (Japanese Unexamined Patent Publication No. 56-102590) provides "a method and apparatus for plating a small area".

The present invention includes a process of masking a minute area of a material to be plated, a process of sealing the inside of this masking part having an outside air introduction means and a fluid removal means, and a process of masking a part of the material to be plated in a sealed space within the masking part. The method includes a process of arranging a nozzle for plating, and uses the nozzle and the material to be plated as an anode and a cathode, plating a minute area, and sucking and removing excess plating solution along with the atmosphere in the closed space and air from the outside air introducing means. It is.

This prevents halation at the plating interface, stabilizes the metal deposition rate, and provides high-quality plating.

In this way, high-precision plating can be processed in large quantities and at a low location, but when the plating liquid column sprayed from the nozzle collides with the opposite surface to be plated, the vector that acts on the fluid particles is At the top of the column, the vector in the vertical (+ZZ-axis direction) becomes zero, and it flows along the inner surface of the surface to be plated (mask), changing its velocity vector.

However, certain fluids intersect at one point on the surface to be plated and from there flow downward in the radial direction while sliding along the surface to be plated.

This point of intersection is called a stagnation point, and the characteristic curve of the fluid becomes as shown in FIG. 1 by solving the Laplace equation.

That is, since the streamline of the plating liquid flow changes its direction to be approximately parallel to the plated surface T, the momentum of the plating liquid column sprayed from the nozzle N in the Z-axis direction decreases.

In other words, a force equal to the momentum decreased in the −Z-axis direction is always generated, and a back pressure is generated against the liquid pressure of the plating solution.

In this state, if the plating solution flowing away in the X-axis direction is not removed sufficiently, the plating solution sprayed later will accumulate in the space between the tip of the nozzle N and the surface to be plated T, causing further damage later. This creates resistance to the plating solution sprayed from the surface, increasing back pressure.

As a result, the flow rate of the sprayed plating solution decreases and the surface to be plated T
1, that is, stagnation of the plating solution occurs on the cathode surface.

As a result, the thickness of the plating diffusion layer increases, the plating current decreases, the current density becomes low, and the plating efficiency is greatly reduced, which is an inconvenient problem.

The present invention was developed in view of the above-mentioned problems, and it forcibly removes the stagnation of the plating solution that occurs on the cathode surface, eliminates the back pressure against the plating solution newly sprayed from the nozzle, and performs plating. It was used for the purpose of increasing the current density.

Specifically, in partial plating, a sealed space is formed on the surface to be plated, a plating solution is sprayed inside the space, and after plating only a specific area, the plating solution is suctioned away. By supplying gas from the outside parallel to and opposite to the injection direction to form an air column around the outer circumference of the plating solution, the stagnation of the plating solution that occurs between the surface to be plated and the tip of the plating solution injection nozzle is forcibly removed. The first object of the present invention is to provide a partial plating method that improves plating current density.

Another object of the present invention is to provide a partial plating device that increases the removal efficiency of the plating solution and does not impair the masking function of the nozzle. , A through hole is formed in the mask body and/or the mask mounting base facing the surface to be plated, corresponding to the surface to be plated and the plating solution injection nozzle, and near the hole, outside air parallel to the injection nozzle is provided. An object of the present invention is to provide a partial plating device equipped with a mask forming an introduction path.

Hereinafter, several embodiments of the present invention will be described with reference to FIG. 2 and subsequent figures.

A nozzle 1 for injecting a plating solution is disposed at the bottom of a mantle tube 4 having a chamber 2 of a predetermined capacity and an evacuation tube 3 communicating with the chamber 2 via a nozzle holder 5 so as to be detachable and adjustable in elevation. be.

A mask 6 is detachably disposed at the top of the mantle tube 4, and the mask 6 is composed of a mask body 7 and a mask mounting base 8.

A through hole 9 is bored in the center of the mask body 7 and the mask mounting base 8 in the vertical axis direction (Z-axis direction), facing the nozzle 1 and having an inner peripheral surface that is a tapered surface. Four arc-shaped outside air introduction passages 10 are bored at equal intervals in a direction parallel to the nozzle 1 (Z-axis direction) on concentric circles centered on the through hole 9.

The mask body 7 is made of ceramic or the like, and has a step between the surface where the through holes 9 are formed and the surface where the outside air introduction path 10 is formed, so that the outside air introduction path 10 is communicated with the outside air or It can be connected to piping (not shown).

This piping is used when supplying pressurized gas (air or inert gas) to the outside air introduction path 10 as required.

Further, the evacuation pipe 3 is connected to an exhaust pump (not shown), and is driven to bring the inside of the chamber 2 into a negative pressure state during plating processing.

The surface to be plated 11 opposite to the mask body 7 is connected to the (-) pole of the DC power supply to serve as the cathode (A) side, while the nozzle 1 is connected to the (+) pole to serve as the anode (4) side. shall be.

When performing plating in the configuration described above, first, the exhaust pump is driven to drain the chamber 2 to the exhaust pipe 3.
A negative pressure condition is established inside the tube, and then a DC voltage is applied between the anode (4) and the cathode (2).

On the other hand, pressurized plating liquid is injected from the nozzle 1 toward the surface to be plated 11, and pressurized gas is supplied from the piping as necessary.

The plating liquid sprayed from the nozzle 1 forms a column with an outer diameter approximately similar to the inner diameter of the nozzle 1 and is applied to the surface to be plated 1 through the mask 6.
1, metal is deposited there, and partial plating corresponding to the through hole 9 is performed.

On the other hand, since the inside of the exclusion pipe 3 and chamber 2 is under negative pressure,
The plating solution and excess plating solution are quickly forcibly removed to the outside in a gas-liquid mixture.

Moreover, since there is always a fresh liquid phase at the boundary between the surface to be plated 11 (solid phase) and the plating solution (liquid phase), the thickness of the diffusion layer that tends to occur at this boundary becomes extremely thin and the ion concentration is uniform. This is the same as forming an electrolyte column formed only by the electrical resistivity specific to the plating solution, and the current value becomes steady and stable, so the metal deposition rate is also stabilized and high-quality plating can be obtained. .

However, since the plating solution is a fairly highly viscous liquid, when it flows over the inner surface of the mask 6 or the surface of the surface to be plated 11, its flow rate is significantly reduced due to its viscous resistance.

Therefore, if the surface to be plated 11 and the nozzle 1 are simply opposed to each other, the plated solution will stagnate in the space between them as described above, creating back pressure against the subsequent plating solution, and as a result, plating Since the current density decreases, the plating function gradually deteriorates in the case of continuous plating processing.

Therefore, in the present invention, the outside air or pressurized gas flows from the outside air introduction path 10 into the mask 6 or the chamber 2 due to the pressure difference, and also flows in parallel and in the opposite direction (i.e., in the opposite direction) to the plating liquid column. , -2 axial direction), a columnar airflow is formed around the plating liquid column.

As a result, the lateral pressure of the plating liquid column decreases, and the plating liquid that diffuses in the X-axis direction is either sucked into this columnar airflow, as theorized by Bernoulli's law, or directly touches the columnar airflow and flows into the removal pipe 3. They were forcibly transferred to and eliminated.

That is, the friction generated between the opposing air streams and the plating solution injected from the nozzle 1 forcibly eliminates the stagnation of the injected plating solution.

Therefore, even if the highly viscous plating solution stagnates on the surface of the cathode, it is forcibly removed by the gas or pressurized gas from the outside air introduction path 10, so there is no risk of creating back pressure. Even when plating is performed continuously, the plating current density is always maintained at a high level, and a large amount of high-quality plating can be performed.

Next, a second embodiment will be described with reference to FIG. 4 and subsequent figures.

This embodiment relates to a multi-system, in which when a large number of surfaces to be plated are arranged in succession, partial plating is performed on them at once.

The mask 21 has a rectangular thin plate-shaped mask body 22 made of ceramic, and a predetermined number of through holes 23 corresponding to the objects to be plated are arranged in series, and each through hole 23 has a funnel-shaped cross section. , and a large number of cylindrical outside air introduction passages 24 are bored at equal intervals at a predetermined distance corresponding to each through hole 23.

The shape of the outside air introduction passage 24 is not limited to a circular plane, but may be an ellipse, an ellipse, or a long slit, and the number may be arbitrary, as long as it can accommodate all the through holes 23. good.

In this embodiment, the through hole 23 and the outside air introduction path 24 are provided only in the mask body 22, but the outside air introduction path 24 may be formed in a stand (not shown) that holds the mask body 22. Of course.

The effects of the mask 21 having the above configuration are the same as those of the embodiment described above, and therefore the explanation thereof will be omitted.

In both the above and the embodiments described above, the shape, number, arrangement interval, etc. of the outside air introduction passages 10°24 are determined as appropriate depending on the object to be plated and the type. , 23, the effect remains the same.

Furthermore, the inner circumferential surface of the through hole is not limited to a tapered shape, but may be formed into a through hole 23' whose inner circumferential surface is hemispherical, as shown in FIG. When the plating solution flows out after plating, it may be streamlined so that the outside air introduction passage 24' faces vertically within the hemispherical surface.

As described above, according to the present invention, outside air can be introduced in any form and in any number into the through holes drilled in the mask, that is, near the stagnation point of the plating liquid, in a direction parallel to the plating liquid column sprayed from the nozzle. The plating solution flowing in the X-axis direction inside the mask is forcibly peeled off from the X-axis surface by forming a channel and the pressurized gas flowing from the channel causes the plating solution to be forcibly removed. Since it is designed to prevent the generation of back pressure, the current density is significantly high, and the plating efficiency does not decrease even during continuous plating processing, so it is highly effective in achieving high-quality plating processing. It is.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the flow of the matting liquid after it collides with the surface to be plated in the conventional partial plating means, and Fig. 2 and the following are related to embodiments of the present invention. FIG. 3 is a plan view of a mask with a single through hole; FIG. 3 is a cross-sectional view taken along the vertical line I-I;
FIG. 6 is a longitudinal sectional view of a mask according to another embodiment. 1...nozzle, 3...exclusion pipe, 4...
・・・・Outer tube, 6.21.21′・・・・Mask, 7,22,22′・・・・Mask body, 8…
...Mask mounting base, 9,23゜23'...Through hole, 10,24,24'...Outside air introduction path, 11
・・・・・・Surface to be plated.

Claims (1)

[Claims] 1. In partial plating, in which a mask is used to form a sealed space on the surface to be plated, and a plating solution is sprayed inside the space to plate only a specific area, the outer periphery of the sprayed plating liquid column is By supplying gas from outside parallel to and opposite to the injection direction to form a columnar airflow, the stagnation of the plating solution that occurs between the surface to be plated and the tip of the plating solution injection nozzle is forcibly removed.
A partial plating method characterized by improving plating current density. 2. A through hole is bored in the mask body and/or the mask mounting base facing the surface to be plated, facing the surface to be plated and the plating solution injection nozzle, and near the hole, outside air parallel to the injection nozzle is provided. A mask having an introduction path formed therein, a mantle tube in which a plating liquid spray nozzle facing the mask is disposed, and a sealed space is formed by fixing the mask; A partial plating device comprising a discharge pipe for pressurizing and discharging a plating solution. 3. The partial plating apparatus according to claim 2, wherein an arbitrary number of outside air introduction passages of the mask are formed on concentric circles around a single through hole. 4 Opposing all of the many through holes in the mask body,
3. The partial plating apparatus according to claim 2, wherein an arbitrary number of said outside air introduction passages are arranged in parallel. 5. The partial plating apparatus according to any one of claims 2 to 4, wherein the outside air introduction path is formed in a straight or curved line in the form of a mesh.