JP2002241999A - Plating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plating apparatus by which plating of high throwing power can be performed, and further, plating time can be reduced. SOLUTION: The plating apparatus has an anode plate 7, and the body 1 to be plated as the cathode having a fine-sized hole at a prescribed position; where they are arranged so as to be confronted at prescribed intervals in a plating solution 6. The apparatus has rolling means eccentrically provided with two rolling elements 4 on both sides of a supporting member 3 suspending and supporting the body 1 to be plated. The apparatus has a bubble generating means 8 generating lots of bubbles 10 rising from the lower direction of the body 1 to be plated along the upper direction in the plating solution 6. The two rolling elements 4 are synchronously rotated, so that the body 1 to be plated is circularly or elliptically shaked in the plane. Further, while forming a rising flow of the bubbles 10 from the lower direction of the body 1 to be plated along the upper direction, plating is applied to the surface including the inside face of the hole of the body 1 to be plated. In this plating apparatus, the shaking amplitude in the plating solution 6 of the body 1 to be plated is controlled to the range of 2 to 10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating apparatus, and more particularly to a plating apparatus suitable for a printed wiring board (hereinafter simply abbreviated as a substrate) having small holes such as through holes and blind holes. .

[0002]

2. Description of the Related Art In the microelectronics industry where the mounting density is increasing year by year, one of the biggest technical problems is the inner wall of a hole which is indispensable for forming circuits such as through holes and blind holes of a build-up substrate or a flexible multilayer substrate. It is an efficient embedding by electroplating and plating with high uniformity. Electroplating is a technique of applying a thin film of mainly a metal or a metal compound to the surface using an electrochemical technique. Plating has a problem that it is difficult to achieve uniform plating as a whole. Although the plating process is an application of electrochemical phenomena, industrially it is not possible to use a simplified system like theoretical electrochemistry, so plating is a technology with a long history, Not all processes are clear.

[0003] In studying plating, it is not possible to abandon the try-and-error method, but at the same time, an electrochemical approach, a metallurgical approach, a complex chloride approach, an analytical chemistry approach, etc. are required. It has been.

[0004] The plating industry has traditionally focused on electrode reaction research, but the reaction is extremely complex. Taking the acid copper plating as an example, we will limit it to only the cathode (cathode) reaction. The total apparent reactions are as follows:

[0005]

Embedded image However, even at the latest research level, it is thought that various phenomena and reactions occur not only in this total reaction but also because the plating is cathodically polarized from the outside. For example, looking at the electrodeposition of copper,

Embedded image Happened and continued

Embedded image A two-step reaction has also been considered. When the whole reaction goes through several stages of electrode reactions, it is said that these reactions may be merely chemical reactions without the entrance and exit of electrons. Since it is not possible to directly see the state of ions existing in water, it has been pointed out that various other changes may have occurred. Eventually, it will be necessary to decipher the measured data and discuss the validity, confirming the complexity of the plating technology.

[0006] When the cathode (cathode) is polarized from the outside, the ions on the surface try to receive the electrons, but the rearrangement of the electrons must occur in the ionic state and the reduced state. This requires extra energy. The state of receiving the extra energy is called an active complex, and the extra energy is called an active energy. Such a reaction of receiving electrons via the active complex (a reaction of releasing electrons in the case of an anode, ie, an anode) is called an activation reaction.

[0007] The metal in the atmosphere is said to be in a state where almost monomolecular water is adsorbed through oxygen. However, if there is a large amount of free water in the surroundings such as in a plating bath, the replacement of water and the oxygen And a partial cathode or partial anode is formed. In the bath, hydrogen is lined up in a portion with a lot of electrons, and oxygen is lined up in a portion with a little electron. However, since the electrons move around, the place is always fluctuating and apparently averaged.

[0008] When trying to polarize in the direction of the cathode (cathode), the electron density on the surface increases, and a part of the electrons is charged with electricity, so that it attracts + electricity. Water is a polar molecule and tends to be positively charged on the hydrogen side and negative on the oxygen side.
For this reason, the water molecules are arranged on the cathode side with the oxygen facing off. Therefore, near the very surface, it is as if a capacitor was made.

[0009] An ion concentration gradient is formed on the outer side, the thickness is at most about 1 µm, and it is said that the transfer of electrons is occurring somewhere in this.

This layer is called an electric double layer or a Helmholtz layer. Activation reactions in this layer, for example

Embedded image If this occurs, a deficiency of Cu ^{2+ in} the vicinity occurs. Therefore, the electric balance cannot be obtained unless Cu ²⁺ is supplied from offshore. In order for Cu ²⁺ to reach the Helmholtz layer from offshore, the concentration gradient increases as the consumption rate increases. Therefore, if the distance is constant, the moving speed increases, and if the speed is constant, the distance increases. This layer having a concentration gradient is called a diffusion layer, and has a thickness of several mm. It is generally thought that the diffusion rate is more constant. However, not only cations but also anions and water move in this layer, and although it is doubtful whether a simple diffusion equation can be applied, it is generally treated in the same way as ordinary diffusion.

[0011] In the case of plating, the process of surface diffusion, nucleation and growth of atoms electrodeposited on the surface is further added, and the process becomes more complicated. Diffusion, formation of the Helmholtz layer, chemical reaction and elementary reaction, nucleation and growth do not occur independently, but occur continuously according to the polarization conditions and the type of change. The potential and the current detected in the measurement of the steady state of the plating show values due to the slowest change called a rate-limiting step among various changes.

Although various phenomena are mixed in the plating bath, fortunately, these phenomena have different speeds. For this reason, although the phenomena are imperfect when viewed from the moment of switch-on, various phenomena are observed. There is also research to get a glimpse of the department. According to it, when there is only one reaction, at the moment when the switch is turned on, there is first a rise due to electrical resistance, followed by the formation of a Helmholtz layer, followed by the formation of a diffusion layer, It is said that phenomena related to nuclear formation occur.

Although there are many factors that determine the rate of electrochemical phenomena, it is considered that diffusion and the like are rate-determining in most cases because current density is sufficiently large in electroplating. In the case of diffusion control, it is said that the magnitude of the current density flowing depends on the number of active complexes present on the electrode surface (correctly called the outside of the Helmholtz layer).

In the case of perfect diffusion control, since the moving speed of charges is faster, the apparent surface concentration becomes zero. The current density in this state is called a limit current density. At the limit current density, since the surface concentration is close to 0, plating from a simple solution is not preferable because a powdery metal is obtained.

Usually, the diffusion speed can be usually adjusted by Nernst's approximation solution. The difference between the offshore concentration and the surface concentration multiplied by the diffusion constant is divided by the thickness of the diffusion layer. Said is said to be affected by convection and can be reduced by stirring. However, the effects of convection such as stirring require complicated calculations such as fluid dynamics, and the quantitative effects have not been sufficiently studied.

In the case of plating, in addition to a reaction for exchanging electrons with an electrode, a mere chemical change often occurs. Examples include dissociation of complex ions, formation of a film by a polymerization reaction, oxidation by dissolved oxygen, reaction with an anode (anode) reactant, and disproportionation reaction. If such a reaction becomes rate-limiting, it cannot be handled easily, but if the supply rate of ions is constant, in this case, a limiting current is observed in the same way as diffusion, and the polarization state is the same as that in the case of diffusion-limited. Will be the same. It is said that the difference from diffusion control is that the effect of temperature is large and the effect of stirring is different. It is said that when the chemical reaction is rate-determining, unexpected data is often obtained, and it is often better to reversely analyze the data to form a logical configuration. This is the current situation where the plating technology has been elucidated. Although it is said that the influence of the Helmholtz layer and the diffusion layer on the plating is great as described above, the elucidation of the mechanism in terms of fluid dynamics has not been advanced, and there are many unknown areas.

In addition to the complicated elements described above, the plating bath is industrially more complicated due to the large capacity of the plating bath. The complexity of this factor, and the plating technology that must be inherently unstable, requires higher precision due to the high-density mounting of substrates, and it is becoming increasingly difficult to deal with it. It is. In other words, when viewed from the laboratory level, an object to be plated with a much larger area has a circuit pattern printed with high density and high accuracy, and the pattern has pores of various shapes processed in the pattern. In addition, it has become increasingly complicated and difficult to adjust various conditions for uniformly plating the inside of the pores. Means for achieving microscopic plating uniformity, that is, a high micro-slow in-power, has heretofore been scarcely studied.

In the conventional plating technique, the plating solution has been agitated by bubbles to uniformly disperse the metal ions dissolved in the anode in the plating bath. The plating layer surface area is about 30 liters per minute per 0.1 m ² ,
With this degree, it is not possible to create a force for completely discharging even the remaining air bubbles in the through holes. Also, the substrate is reciprocated in a direction perpendicular to the surface thereof, or reciprocated up and down or left and right in a parallel direction (that is, a plane direction),
There is also a method in which the substrate is oscillated to cause a plating solution to flow in pores such as through holes. However, there is practically no effect in terms of fluid dynamics.

When observing the behavior of the plating bath hydrodynamically,
Since the majority of the plating bath is water, the behavior of water must be of the utmost importance. Water is a polar molecule, is in the bath does not mean that are present as H ₂ O monomolecular, 4-5 molecules are electrically loosely coupled. This loose binding state is a factor that makes water viscous. The metal ions are present in a hydrated state in the plating solution, and the hydrated metal ions are usually a hexacoordinate cation complex [M (OH
₂ ) ₆ ] It has a structure of ^{n +} . Since Cu is a divalent metal, ^{n +} is ²⁺ and is wrapped like a complex with 12 water molecules.

The water in the plating solution itself as well as the existing anions and cations are all hydrated and exhibit viscosity under the influence of water molecules. In actual plating, the precipitation reaction of the hydrated metal in the local region such as the Helmholtz layer, that is, the reduction reaction, occurs continuously, but the aggregate of water molecules remaining when reduced has viscosity, so it is located at that position. Attempts to accumulate and hinder the reactions that must occur continuously. This effect becomes more remarkable as the surface area of the object to be plated increases as in the case of industrial plating, and appears as plating variation. This is one of the reasons why the electrochemical theory, which tends to keep the electrophoresis speed causing diffusion constant, cannot fully explain the actual plating phenomenon.

Further, in the reduction reaction of the hydrated metal ions, when the fact that the viscosity of water impedes the movement of the approaching metal ions, the conditions for making the electrochemical reaction efficient and uniform are considered. You can see how important it is to arrange. If a method could be obtained in which the Helmholtz layer on the surface of the anode and cathode (substrate) and the diffusion layer on the outside of the anode and cathode (substrate) were positively destroyed by a physical external force, and the necessary and sufficient metal ions were supplied continuously and stably to the vicinity Thus, plating by an electrochemical mechanism is established as a stable technique. The present invention described below is an effective means for forming a turbulent flow in the plating solution near the cathode (substrate).

In recent years, with the progress of organic additives, great improvements have been seen in plating uniformity and physical properties. However, the need to increase the mounting density of electronic circuits is increasing, and the plated parts of through-holes and blind holes that form three-dimensional circuits due to the further refinement of circuit line widths are also becoming smaller and smaller. For this purpose, it is very important to improve the structure of the Helmholtz layer and the diffusion layer, which are extremely important for stabilizing the electrochemical reaction of plating.

As the hole diameter of the through hole or the blind hole becomes smaller, even if there is a slight difference in the ion supply amount at the plating portion, the uniformity of plating is greatly affected. In the prior art, it is almost impossible to improve the thinning of the plating at the center of the through hole, and this is a major problem in the performance and reliability of the formed circuit. When the applied current density is increased according to the electrochemical theory,
As compared with the inner wall of the hole, the plating thickness of the portion near the circuit surface and the opening of the hole is too large. Therefore, the applied current density cannot be increased, so that the plating time cannot be reduced. In addition, when filling a blind hole or the like, since plating in the hole is small, plating must be repeated after the thick plated surface is polished and thinned, resulting in an extremely large number of steps and poor production efficiency.

[0024]

As a prior art to which attention should be paid to the oscillation of the object to be plated, there is Japanese Patent No. 1572271 (Japanese Patent Publication No. 1-343039). This patent shows that applying a circular or elliptical motion to the substrate in the plating solution can effectively increase the applied current density and reduce the plating time. Further, the circular or elliptical movement of the substrate increases the turbulence of the plating solution, thereby enabling uniform plating on the inner wall of the through hole. According to an embodiment of this patent, the amplitude of the circular or elliptical motion is 100 m
m, relatively high, and the rotation speed is 2.5 to 10 times per second.
The speed is extremely fast, from 150 rpm to 600 rpm.

A vortex is generated by moving the substrate in a circular or elliptical motion in the plating solution. A region called an island region that moves regularly on a closed orbit is formed at the center of the vortex. When the amplitude of the circular or elliptical motion of the substrate is large as described above, an island region is easily formed. Further, when the substrate rotates at a high speed as in this patent, there are problems in the structure and durability of the apparatus.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art. For example, highly uniform plating can be performed even on a through hole or a blind hole having a hole diameter as small as about 0.2 mm. An object of the present invention is to provide an efficient plating apparatus capable of reducing time.

[0027]

The difference in plating thickness is mainly caused by the local variation in the supply amount of metal ions and the variation in the lines of electric force between the anode and the anode, and the surface of the substrate and the inner walls of through holes and blind holes. This is because there is a difference in the amount of precipitation in the hole, and the hole shape is complicated. If any improvement is made to the Helmholtz layer and the diffusion layer, highly uniform plating can be obtained.

The present invention has been made based on such knowledge, and in order to achieve the above object, a first means is to provide an anode plate which is disposed so as to face a plating solution at a predetermined interval. The two rotating bodies are eccentrically provided on both sides of a plate to be plated, for example, a substrate, having a small diameter hole at a predetermined position, which serves as a cathode, and a support member, such as a bar, for suspending and supporting the plate. A rotating means having, for example, an eccentric cam, a power transmission mechanism, a motor, and the like, and a bubble generating means such as an air box for generating an infinite number of bubbles rising upward from below the object to be plated in the plating solution. The object to be plated is swung in a circular or elliptical shape in the plane by synchronously rotating the two rotating bodies, and bubbles are formed along the object to be plated from below to above. In a plating apparatus for plating a surface including an inner surface of a hole of an object to be plated while forming an ascending flow, a swing amplitude of the object to be plated in a plating solution is regulated in a range of 2 mm to 10 mm. It is assumed that.

According to a second aspect of the present invention, in the first aspect, the rotational speed of the rotating body is from 60 rpm to 140 rpm.
It is characterized by being restricted to the range of m.

A third aspect of the present invention is the first aspect or the second aspect, wherein the rate of rise of bubbles in the plating solution is regulated to a range of 0.5 m / sec to 1.0 m / sec. It is characterized by having.

According to a fourth aspect of the present invention, in the first aspect, the rotation speed of the rotating body is from 60 rpm to 140 rpm.
m, and the rising speed of bubbles in the plating solution is regulated to a range of 0.5 m / sec to 1.0 m / sec.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of a plating apparatus according to an embodiment of the present invention will be described with reference to the drawings. 1 to 5 are views for explaining a plating apparatus according to an embodiment. FIG. 1 is a front view of the plating apparatus, FIG. 2 is a plan view of the plating apparatus, and FIG. FIG. 4 is a sectional view taken along line XX of FIG. 3 and FIG.
It is an enlarged view of a part.

As shown in FIG. 1, the substrate 1 is suspended vertically by a cathode power supply clamp 2 to serve as a cathode. The cathode power supply clamp 2 is attached to a bar 3, and eccentric cams 4, 4 are connected to both ends of the bar 3. Have been. The substrate 1 is immersed in a plating solution 6 in a bath 5. The eccentric cam 4 is rotationally driven through a power transmission mechanism such as a motor and a gear, not shown, and the substrate 1 rotates in a circle or an ellipse in the plating solution 6 by the rotation of the eccentric cam 4. In the present specification, the circular or elliptical motion of the substrate 1 due to the rotational motion is called swing.

As shown in FIG. 4, the substrate 1 is suspended between anode titanium baskets 7, 7 filled with a large number of phosphorous-containing copper balls arranged in two rows. As the substrate 1, for example, a copper-clad laminate in which through holes having a diameter of 0.3 mm are formed at predetermined positions and further subjected to a conductivity imparting treatment such as electroless plating is used.

An air box 8 is provided at the bottom of the bathtub 5. As shown in FIG. 5, a large number of pores 9 are provided in two rows at the top of the air box 8, and countless bubbles 10
Is discharged and rises in the plating solution 6.

Inside the air box 8, though not shown, a blower pipe 18 connected to an external high-pressure blower through a valve penetrates, and the valve is adjusted to determine the amount of air. Further, an air discharge hole 19 having a relatively large diameter is formed in the pipe 18 to make the amount of air discharged from the hole 9 of the air box 8 uniform.

As shown in FIGS. 3 and 4, the overflow bath 12 surrounds the upper four sides of the bathtub 5, and has an ascending flow accompanying the air bubbles 10 and is installed on both sides of the air box 8 (not shown). The liquid in the pipe 20 to be sent to the bath 5 is collected through the heat exchange tank and the filter, and returned to the heat exchange tank again. The plating solution 6 constantly circulates between the bath 5 and the heat exchange tank.

When the air is not agitated in the plating apparatus, the liquid level of the bath keeps the flow 5a slightly over the portion 21 which is the boundary between the bath 5 and the overflow tank 12 because the supply amount of the filter is constant. When plating the substrate 1, the eccentric cam 4 is rotated at a predetermined speed (for example, 100 rpm) to swing the substrate 1 (for example, a swing width of 2 mm), press air into the air box 8, and After an infinite number of bubbles 10 are released from the substrate, a current (for example, a cathode current density of 5 A / dm ² ) is passed through the cathode substrate 1 and the anode basket 7.

Then,

The generated bubbles 10 are divided along the current plate 11 and distributed to both sides of the substrate 1 to rise and stir the plating solution 6 (for example, the bubble rising speed is 0.5 m / sec). The liquid level of the plating solution 6 rises due to the injection of the bubbles 10, the central portion rises as shown by a curved broken line in FIG. 15, and from the lower end of the partition plate 15 to the lower end of the anode basket 7 and the depressing plate 16 again, it joins the upward flow and repeats the circulation. At this time, the air box 8
The deterrent plate 16 suppresses the downward flow from affecting the bubble flow. Thus, the flow on the surface of the substrate 1 can be kept uniform. In the drawing, 13 is an overflow pipe, 14 is a pipe drain, and 17 is a filtrate supply pipe.

In the present invention, various experiments were carried out based on turbulence generation factors considered to affect the Helmholtz layer and the diffusion layer, by setting up a test design that can clarify the correlation between the factors and the plating effect. Resulting from the result. An industrial production scale plating apparatus as shown in this embodiment was manufactured, and it was verified whether the results obtained at the experimental level had industrial practicality.

(Experimental Method) The plating apparatus used in the experiment has the same structure as that shown in FIGS. Experiments 1-3 below
The substrate 1 used for (1) has a length of 300 mm, a width of 300 mm, and a thickness of 1.6 mm. The through-hole diameter is 0.2 mm
3 mm, 1.0 mm, 5 mm each on the center line of the substrate 1 and 0.2 mm, 0.3 m on the line 9 cm on both sides of the center line
m and 1.0 mm.

These substrates were first subjected to electroless copper plating in the holes based on a commercially available direct plating plating solution and a recipe using the same. The conditions for the copper plating solution are
It is as follows.

CuSO ₄ .5H ₂ O 90 g / L H ₂ SO ₄ 190 g / L Chlorine 50 ppm Commercial brightener Small amount Bath temperature 24 ° C. To obtain a plating thickness of 25 μm, an applied current density (Dk) of 5
A / dm ² , processing for 25 minutes was applied to each of the four substrates under conditions according to the purpose of the experiment, and two ends of each hole array were cross-cut to measure the slow-in power, and the average was calculated. The values were calculated to produce the following characteristic diagrams. The throw-in power is a value of the ratio of the plating thickness (T) of the inner wall of the hole to the surface plating thickness (P) [(T / P) × 100].
(%), And the uniformity of plating can be evaluated based on the level of the slow-in power.

The conventional applied current density (Dk) is 2 A / dm
^{Since 2} or less is normal, the applied current density (Dk) of 5 A / dm ^{2 according} to the embodiment of the present invention is remarkably large as compared with the conventional one. The magnitude of the applied current density (Dk) supports the theory of the present invention, and the fact that the applied current density (Dk) is large as described above can greatly reduce the plating time.

(Experiment 1: Relationship between through-hole diameter (diameter) and bubble rising speed) In Experiment 1, the applied current density (Dk) was 5
A / dm ² , the amplitude of the substrate was fixed at 5 mm, the rotation speed of the rotation swing width variable cam (cathode) was fixed at 100 rpm, and the bubble rising speed was changed to 0.2 m, 0.5 m and 1.0 m per second. The relationship between the bubble rising speed and the slow-in power at each through-hole diameter in the case of the above was examined, and the results are shown in FIG. As is clear from this figure, when the through hole diameter is 1.0 mm, the bubble rising speed is about 80% at 0.5 m / sec.
Can be achieved, and the smaller the diameter of the through-hole, the lower the throw-in power tends to be. However, for any diameter of the through-hole, if the bubble rising speed increases to 0.5 m / sec and 1.0 m / sec, the slow-in power increases, while if the bubble rising speed is 0.2 m / sec, the slow-in power increases. It is insufficient and uniform plating cannot be obtained.

Observation of the through hole having a diameter of 1 mm revealed that the plating thickness of the inner wall of the hole was larger than the surface. This indicates that the plating solution is sufficiently distributed to the inner wall of the hole due to the turbulence effect, and that the turbulence energy increases as if approaching the inlet, so that the influence on the Helmholtz layer and the diffusion layer is reduced. It is considered that the reason is larger.

(Experiment 2: Through-hole diameter and cathode (substrate))
Next, Dk was fixed at 5 A / dm ² , the bubble rising speed was fixed at 0.5 m / sec, and the cathode rotation speed was fixed at 100 rpm.
2mm, 10mm, 50mm, 100mm cathode swing width
An experiment was conducted to see how the magnitude of the cathode swing width affected the through-hole diameter, and the results are shown in FIG.

As is apparent from this figure, the swing width of the cathode is an important factor for realizing a high slow-in power, and if the amplitude is sufficiently small, 2 mm to 10 mm, the diameter of the through hole becomes small. It can be seen that uniformity can be stably achieved even for the substrate. If the amplitude is as large as 100 mm as in the conventionally proposed one, the slow-in power is low even if the through-hole diameter is large.

(Experiment 3: Relationship between bubble rising speed and swing width of cathode (substrate)) Then, Dk was fixed at 5 A / dm ² , through-hole diameter was fixed at 0.3 mm, and cathode rotation speed was fixed at 100 rpm.
The bubble rising speed was changed to 0.2 m / sec and 0.6 m / sec, and the cathode swing width was 2 mm, 10 mm, 50 mm, 100 mm.
The experiment was conducted on the relationship between the bubble rising speed and the cathode swing width while changing the distance to mm, and the results are shown in FIG.

As is clear from this figure, it was found that the higher the bubble rising speed and the smaller the swinging width of the cathode, the higher the slow in-power achieved, and from the tendency of the two curves in the figure. It can be seen that the influence of the cathode swing width on the bubble rising speed of 0.6 m / sec is greater than the effect of the cathode swing width on the bubble rising speed of 0.2 m / sec. In consideration of the results of Experiment 1, it was found that the bubble rising speed is required to be a certain level or more, but it is more important that the cathode swing width is smaller when the bubble reaches a certain level.

From the experimental results shown in FIGS. 6 to 8 above, in order to achieve the micro-slow in power of plating of through holes and the like, the cathode swing width is in the range of 2 mm to 10 mm, and the bubble rising speed is 0.5 m / sec. It has been found that it is better to restrict the range to 1.0 m / sec. This is considered to be caused by the turbulence effect rather than the stirring effect of the plating solution, which has been conventionally called.

When the bubble rising speed is 0.5 m / sec, the air supply amount is 900 to 1000 liters in terms of the same plating bath surface area. The air supply amount is 30 times or more as compared with the air supply amount of 30 liters described in the prior art, and it is considered that a phenomenon completely different in dimension from the conventional bubble generation for stirring the plating solution is caused.

Among the effects provided by the large air supply and the accompanying high bubble rising speed, an increase in the Reynolds number and generation of turbulence must not be overlooked. In the conventional bubble rising speed, the thickness of the laminar flow formed at the boundary with the cathode (substrate) was relatively large. Although it is considered that the turbulence is caused by the effect of bubbles in a part of the transition region, it is considered that the turbulence does not affect the diffusion layer in view of the thickness of the diffusion layer.

On the other hand, at the bubble rising velocity defined in the present invention, turbulence is remarkable, and the vibration of bubbles having a three-dimensional rising behavior is fine and complicated. The bubble accompanied by the three-dimensional vibration is complicatedly deformed by the interfacial tension between the plating solution and the pressure applied to the bubble. This deformation causes a local and indeterminate vector pressure transition inside the plating solution. The repetition destroys the transition zone,
It is considered that not only the diffusion layer several mm from the surface of the cathode (substrate) but also the lightly polarized water molecule layer on the surface of the cathode (substrate), that is, the Helmholtz layer is affected.
In other words, the partial cathode of the electrode generated by normal plating,
The partial anode will be removed, stabilizing one of the important building blocks to achieve plating uniformity. Further, in the present invention, since the applied current density increases and the plating time is shortened, it is considered that the diffusion layer is extremely thin.

As is evident from Experiment 1 (see FIG. 6), the reason why the increase in bubble rising speed alone does not provide sufficient slow-in power for a small-diameter through-hole is that the turbulence caused only by the rise of bubbles inside the through-hole. It is thought that it is only the flow. By adding a fine circular or elliptical motion (vibration) of the cathode (substrate) to this, the vector effect of turbulence generated by the circular or elliptical motion is added synergistically,
The pressure relationship between the plating solutions on both sides of the through hole becomes really complicated, and the plating solution in the through hole receives the turbulence effect without staying.

The turbulence generated behind the rising bubble consists of small vortices, the direction of which is in the opposite direction to the rising direction. However, the circular or elliptical motion of the substrate, if the rotation is moderate, generates a vortex in the direction perpendicular to the axial direction of the through hole, making the transition of the plating solution pressure around the hole more complicated and reducing the retention of the plating solution. It has the effect of making it smaller.

(Experiment 4: Relationship between Cathode Rotation Speed and Slow In Power) In Experiments 1 to 3, the cathode rotation speed was set to 1
The experiment was carried out with the rotation speed fixed at 00 rpm, in order to examine the optimization of other factors with the rotation speed considered to be optimum shown in Experiment 4 as a fixed condition.

Experiment 4 was conducted at a relatively early stage. In Experiment 4, a substrate having a thickness of 1.6 mm and a through-hole diameter of 0.3 mm was used, the bubble rising speed was set to 0.6 m / sec, and the cathode swing width was set to 2 mm. Furthermore, a high current density (Dk) 5 so as to minimize the plating time
A / dm ² was applied. It is natural that a higher slow-in power can be achieved at a current density lower than 5 A / dm ^2, so that the current density (Dk) 5 A / dm ² is a strict setting for specifying the rotational speed condition. FIG. 9 shows the relationship between the cathode rotation speed and the slow-in power when the cathode rotation speed is changed under such conditions.

In particular, in the case of a substrate having a high aspect ratio such as 1.6 mm in thickness and a through-hole hole diameter of 0.3 mm used in this experiment, the difference in slow-in power depending on the cathode rotation speed clearly appears. In such hole plating with a high aspect ratio, the demand for slow-in power becomes extremely strict in terms of substrate performance and reliability. As is clear from FIG. 9, even if the cathode rotation speed is as slow as 20 rpm or 40 rpm, or even as fast as over 140 rpm, sufficient slow-in power cannot be obtained.
As described above, in order to apply a high current density and obtain a slow-in power of 80% or more, the cathode rotation speed must be set to 60 r.
It is necessary to regulate in the range of from rpm to 140 rpm, preferably in the range of from 80 rpm to 120 rpm.

From the experimental results for separating and evaluating these various factors, it was found that the improvement of the plating slow-in power had a correlation with the bubble rising speed, the swing amplitude, and the cathode rotation speed.

In the above-described embodiment, the case where a substrate is used as an object to be plated has been described. However, the present invention is not limited to this. For example, plating on a silicon wafer and other metal having pores with a high aspect ratio The present invention is also applicable to other plated objects having holes, such as and other flat plates.

[0063]

As described above, according to the present invention, an object to be plated having a hole at a predetermined position and an anode plate which is disposed so as to face a predetermined distance in a plating solution, and the object to be plated is suspended and supported. A rotating means provided eccentrically with two rotating bodies on both sides of the supporting member, and a bubble generating means for generating innumerable bubbles rising upward from below the body to be plated in the plating solution, The object to be plated is swung in a circular or elliptical shape in the plane by synchronously rotating the two rotating bodies, and the object to be plated is formed while forming a rising flow of air bubbles from below to above the object to be plated. In a plating apparatus that performs plating on the surface including the inner surface of a hole in a plated body, the swing amplitude of the body to be plated in the plating solution, the rotation speed of the rotating body, and the rising speed of bubbles in the plating solution are each regulated. More, higher throw-power achievable, yet it is possible to provide an efficient plating apparatus can be shortened plating time.

[Brief description of the drawings]

FIG. 1 is a front view of a plating apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the plating apparatus.

FIG. 3 is a perspective view in which a part of the plating apparatus is cut away.

FIG. 4 is a sectional view taken on line XX of FIG. 3;

FIG. 5 is an enlarged view of a portion shown in FIG. 4A.

FIG. 6 is a characteristic diagram showing a relationship between a through hole diameter of a substrate and a bubble rising speed.

FIG. 7 is a characteristic diagram showing a relationship between a through hole diameter of a substrate and a cathode swing width.

FIG. 8 is a characteristic diagram showing a relationship between a bubble rising speed and a cathode swing width.

FIG. 9 is a characteristic diagram illustrating a relationship between a cathode rotation speed and a slow in power.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Cathode power supply clamp 3 Bar 4 Eccentric cam 5 Bath 6 Plating solution 7 Anode titanium basket 8 Air box 9 Hole 10 Bubbles 11 Rectifier plate 12 Overflow tank 13 Overflow piping 14 Pipe drain 15 Rectifier plate 16 Suppression plate 17 Filtrate supply Pipe 18 Ventilation pipe 19 Air discharge hole 20 Filtrate supply pipe

Claims (4)

[Claims] An anode plate and a cathode, which are disposed so as to face each other at a predetermined interval in a plating solution, and have a small-diameter hole at a predetermined position to be plated. A rotating means provided eccentrically with two rotating bodies on both sides of a supporting member to be formed; and bubble generating means for generating countless bubbles rising upward from below the body to be plated in the plating solution. By rotating the two rotating bodies synchronously, the object to be plated is swung in a circle or an ellipse in the plane thereof, while forming a rising flow of air bubbles from below to above the object to be plated. A plating apparatus for plating a surface including an inner surface of a hole of a body to be plated, wherein a swing amplitude of the body to be plated in a plating solution is 2 mm.
A plating apparatus characterized by being restricted to a range of 10 to 10 mm. 2. The plating apparatus according to claim 1, wherein a rotation speed of said rotating body is regulated in a range of 60 rpm to 140 rpm. 3. The plating apparatus according to claim 1, wherein a rising speed of bubbles in the plating solution is regulated in a range of 0.5 m / sec to 1.0 m / sec. A plating apparatus characterized by the following: 4. The plating apparatus according to claim 1, wherein the rotation speed of the rotating body is regulated in a range of 60 rpm to 140 rpm, and a rising speed of bubbles in the plating solution is 0.5 m / sec to 1.0 m. A plating apparatus characterized in that the plating rate is regulated in the range of / sec.