U.S. patent application number 09/864650 was filed with the patent office on 2001-11-29 for electroplating method using combination of vibrational flow in plating bath and plating current of pulse.
Invention is credited to Omasa, Ryushin.
Application Number | 20010045360 09/864650 |
Document ID | / |
Family ID | 27343513 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045360 |
Kind Code |
A1 |
Omasa, Ryushin |
November 29, 2001 |
Electroplating method using combination of vibrational flow in
plating bath and plating current of pulse
Abstract
In an electroplating method, a plating target article (X)
disposed so as to be in contact with plating bath (14) is set as a
cathode while a metal member disposed so as to be in contact with
the plating bath (14) is set as an anode, and a voltage is applied
between the cathode and the anode while vibrational flow is induced
by vibrating vibrational vanes (16f) which are fixed in multi-stage
style to a vibrating rod (16e) vibrating in the plating bath (14)
interlockingly with vibration generating means (16d). Plating
current flowing from the anode through the plating bath (14) to the
cathode is pulsed and alternately set to one of a first state where
the plating current keeps a first value I1 for a first time T1 and
a second state where the plating current keeps a second value I2
having the same polarity as the first value I1 for a second time
T2, the first value I1 being five or more times larger than the
second value I2, and the first time T1 being three or more times
longer than the second time T2.
Inventors: |
Omasa, Ryushin; (Kanagawa,
JP) |
Correspondence
Address: |
Ronald R. Santucci
Pitney, Hardin, Kipp & Szuch, LLP
20th Floor
711 Third Avenue
New York
NY
10017
US
|
Family ID: |
27343513 |
Appl. No.: |
09/864650 |
Filed: |
May 23, 2001 |
Current U.S.
Class: |
205/108 ;
205/137; 205/145; 205/148 |
Current CPC
Class: |
B01F 31/441 20220101;
C25D 5/627 20200801; C25D 7/123 20130101; C25D 21/10 20130101; C25D
5/18 20130101 |
Class at
Publication: |
205/108 ;
205/137; 205/148; 205/145 |
International
Class: |
C25D 005/18 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2000 |
JP |
2000-155046 |
Aug 10, 2000 |
JP |
2000-243249 |
Apr 26, 2001 |
JP |
2001-129994 |
Claims
What is claimed is:
1. An electroplating method, characterized in that a plating target
article disposed so as to be in contact with plating bath is set as
a cathode while a metal member disposed so as to be in contact with
the plating bath is set as an anode, and a voltage is applied
between the cathode and the anode while vibrational flow is induced
by vibrating vibrational vanes which are fixed in one-stage or
multi-stage style to a vibrating rod vibrating in the plating bath
interlockingly with vibration generating means, wherein plating
current flowing from the anode through the plating bath to the
cathode is pulsed and alternately set to one of a first state where
the plating current keeps a first value I1 for a first time T1 and
a second state where the plating current keeps a second value I2
having the same polarity as the first value I1 for a second time
T2, the first value I1 being five or more times larger than the
second value I2, and the first time T1 being three or more times
longer than the second time T2.
2. The electroplating method as claimed in claim 1, wherein the
first value I1 is 6 to 25 times as large as the second value I2,
and the first time T1 is 4 to 25 times as long as the second time
T2.
3. The electroplating method as claimed in claim 1, wherein the
first value I1 is set to 0.01 to 300 seconds.
4. The electroplating method as claimed in claim 1, wherein the
vibrational vanes are vibrated at an amplitude of 0.05 to 10.0 mm
and a vibration frequency of 200 to 1500 revolutions per
minute.
5. The electroplating method as claimed in claim 1, wherein the
vibrational vanes are vibrated so that the vibrational flow of the
plating bath has a three-dimensional flow rate of 150 mm/second or
more.
6. The electroplating method as claimed in claim 1, wherein the
vibration generating means vibrates at 10 to 500 Hz.
7. The electroplating method as claimed in claim 1, wherein the
plating target article is vibrated at an amplitude of 0.05 to 5.0
mm and a vibration frequency of 100 to 300 revolutions per
minute.
8. The electroplating method as claimed in claim 1, wherein the
plating target article is swung at a swinging width of 10 to 100 mm
and a swinging frequency of 10 to 30 times per minute.
9. The electroplating method as claimed in claim 1, wherein the
plating target article has a face to be plated having a
microstructure of a dimension of 50 .mu.m or less.
10. The electroplating method as claimed in claim 1, wherein a
plurality of plating target articles are accommodated in a holding
container, said holding container having small holes through which
liquid of the plating bath is allowed to pass and being equipped
with an electrically conductive member which is brought into
contact with the plating target articles to make current flow
through the plating target articles, and wherein said holding
container is rotated around the rotational center corresponding to
a non-vertical direction in the plating bath to roll the plating
target articles in said holding container to thereby repeat the
contact and separation between each of the plating target articles
and said electrically conductive member.
11. The electroplating method as claimed in claim 10, wherein the
width of each of the plating target articles is equal to 5 mm or
less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plating method, and
particularly to a plating method using a specific combination of a
physical condition of a plating bath and an electric condition of
plating current.
[0003] 2. Description of the Related Art
[0004] An electroplating technique of forming a film of
electrically conductive material on the surface of an article has
been broadly used in the manufacturing industry of articles such as
electronic parts, etc. Particularly, in order to satisfy
requirements of miniaturization and high functionality to
electronic parts, conductive patterns to be formed on the surfaces
(containing the inner surface of through hole, the inner surface of
blind via hole) of articles have been required to be formed
finely.
[0005] For example, the microstructure design of wiring patterns is
promoted in connection with decrease of the pitches of input/output
terminals due to the high-integration design of semiconductor
devices, and in connection with this promotion, it has been
required that the through hole and the blind via hole are designed
to have an inner diameter of 100 .mu.m or less, further 50 .mu.m or
less, still further 30 .mu.m or less. Further, a large aspect ratio
of 5 or more, further 8 or more has been required to the through
hole and the blind via hole.
[0006] For example, in order to reduce the capacity between wires
which occurs due to the microstructure design of wires required in
connection with the high-integration design, copper wires are used
in place of aluminum wires which have been hitherto used, and a
damascene method using electroplating to form copper multi-layered
wires has been used. In this method, it has been required to
perform copper deposition in very small blind via holes having the
inner diameter of 1 .mu.m or less.
[0007] Further, it has been required that a pair of electrode films
are formed on the surface of a chip part having a dimension of
about 0.3 mm.
[0008] Particularly, the applicant of this application has proposed
a plating method that is effectively applicable to articles having
microstructured parts such as fine holes, etc. (see
JP(A)-11-189880). According to this method, vibrational flow
induced in a plating bath and bubbling induced by a diffusing pipe
are used in combination. This method is also effectively applicable
to electroless plating as well as electroplating.
[0009] However, in this method, it is required to dispose the
diffusing pipe in a plating tank in which the plating bath is
accommodated, and also it is required to establish an air pipe to
the diffusing pipe. Therefore, the amount of the plating bath and
the dimension of the plating tank must be relatively increased, so
that the plating apparatus itself must be designed in large
size.
[0010] Besides, DC power source is generally used as power source
for the electroplating. In order to enhance the quality of plating
films, there has been proposed a technique of carrying out plating
while the plating current is periodically varied. In this method,
positive-polarity current and negative-polarity current alternately
flows. That is, a plating film is temporarily formed by supplying
the positive-polarity current, and then projecting portions of
minute uneven portions on the surface of the plating film thus
formed are concentratively and partially melted by supplying the
negative-polarity current. The above operation is repeated to
achieve a high-quality plating film that has a flat surface and no
defects such as minute voids or the like. According to this method,
however, the surface portion of the plating film which is
temporarily formed is removed and thus this method has a
disadvantage in enhancement of the film forming speed (that is, the
enhancement of the plating treatment speed).
[0011] It is a recent tendency that conductive patterns are
designed in a further microstructure design, and when a plating
film having such a conductive pattern is formed, defects or
unevenness in film thickness is liable to occur. Therefore, it has
been more and more difficult to keep the excellent quality of the
plating film.
[0012] The applicant of this application has also proposed a
plating method of carrying out chrome-plating while vibrationally
stirring the plating bath, and a plating method of accommodating
many articles to be plated (hereinafter referred to as "plating
target articles") in a barrel and carrying out chrome-plating while
vibrationally stirring the plating bath (see JP(A)-7-54192 and
JP(A)-6-330395).
[0013] However, these methods use direct current as plating
current, and these publications have no specific disclosure on the
application of these methods to minute plating target articles such
as articles each of which has a width (the dimension in the
traverse direction to the longitudinal direction) of 5 mm or less,
for example, 0.3 to 1.0 mm. In the barrel plating process for these
minute plating target articles, the plating target articles are
overlapped with one another in the barrel, and thus the
distribution of plating liquid to desired plating film forming
portions of the plating target articles is extremely lowered.
Therefore, there are a lot of technical difficulty for these minute
plating target articles beyond comparison with plating target
articles having relatively large widths, and a further improvement
must be made in point of the film forming speed and the evenness of
film thickness.
SUMMARY OF THE INVENTION
[0014] Therefore, an object of the present invention is to provide
a plating method which can form a plating film having a
microstructured conductive pattern with high quality so that the
plating film has no defect and is not uneven in film thickness.
[0015] Another object of the present invention is to provide a
plating method which can form a high-quality plating film having a
microstructured conductive pattern at high speed.
[0016] Another object of the present invention is to provide a
plating method which can efficiently form a high-quality plating
film having a microstructured conductive pattern by a relatively
small apparatus.
[0017] In order to attain the above objects, according to the
present invention, there is provided an electroplating method,
characterized in that a plating target article disposed so as to be
in contact with plating bath is set as a cathode while a metal
member disposed so as to be in contact with the plating bath is set
as an anode, and a voltage is applied between the cathode and the
anode while vibrational flow is induced by vibrating vibrational
vanes which are fixed in one-stage or multi-stage style to a
vibrating rod vibrating in the plating bath interlockingly with
vibration generating means, wherein plating current flowing from
the anode through the plating bath to the cathode is pulsed and
alternately set to one of a first state where the plating current
keeps a first value I1 for a first time T1 and a second state where
the plating current keeps a second value I2 having the same
polarity as the first value I1 for a second time T2, the first
value I1 being five or more times larger than the second value I2,
and the first time T1 being three or more times longer than the
second time T2.
[0018] In an aspect of the present invention, the first value I1 is
6 to 25 times as large as the second value I2, and the first time
T1 is 4 to 25 times as long as the second time T2. In an aspect of
the present invention, the first value I1 is set to 0.01 to 300
seconds. In an aspect of the present invention, the vibrational
vanes are vibrated at an amplitude of 0.05 to 10.0 mm and a
vibration frequency of 200 to 1500 revolutions per minute. In an
aspect of the present invention, the vibrational vanes are vibrated
so that the vibrational flow of the plating bath has a
three-dimensional flow rate of 150 mm/second or more. In an aspect
of the present invention, the vibration generating means vibrates
at 10 to 500 Hz.
[0019] In an aspect of the present invention, the plating target
article is vibrated at an amplitude of 0.05 to 5.0 mm and a
vibration frequency of 100 to 300 revolutions per minute. In an
aspect of the present invention, the plating target article is
swung at a swinging width of 10 to 100 mm and a swinging frequency
of 10 to 30 times per minute.
[0020] In an aspect of the present invention, the plating target
article has a face to be plated having a microstructure of a
dimension of 50 .mu.m or less.
[0021] In an aspect of the present invention, a plurality of
plating target articles are accommodated in a holding container,
the holding container having small holes through which liquid of
the plating bath is allowed to pass and being equipped with an
electrically conductive member which is brought into contact with
the plating target articles to make current flow through the
plating target articles, and wherein the holding container is
rotated around the rotational center corresponding to a
non-vertical direction in the plating bath to roll the plating
target articles in said holding container to thereby repeat the
contact and separation between each of the plating target articles
and the electrically conductive member.
[0022] In an aspect of the present invention, the width of each of
the plating target articles is equal to 5 mm or less.
[0023] According to the electroplating method of the present
invention, even when a plating conductive pattern is minute, a
plating film having uniformity in thickness and no defect can be
formed with high quality. Further, according to the present
invention, a high-quality plating film of microstructured
conductive pattern can be obtained at high speed. Still further,
according to the present invention, a high-quality plating film of
microstructured conductive pattern can be efficiently obtained by a
relatively small apparatus.
BRIEF DESCRIPFION OF THE DRAWINGS
[0024] FIG. 1 is a cross-sectional view showing the construction of
a plating apparatus to which a first embodiment of a plating method
according to the present invention is applied;
[0025] FIG. 2 is a cross-sectional view showing the construction of
the plating apparatus to which the first embodiment of the plating
method according to the present invention is applied;
[0026] FIG. 3 is a plan view showing the construction of the
plating apparatus to which the first embodiment of the plating
method according to the present invention is applied;
[0027] FIG. 4 is an enlarged cross-sectional view showing the
fixing portion of a vibration transmitting rod to a vibrating
member;
[0028] FIG. 5 is an enlarged cross-sectional view of the fixing
portion of a vibrating vane to the vibration transmitting rod;
[0029] FIG. 6 is a diagram showing a modification of the fixing
portion of the vibrating vane to the vibration transmitting
rod;
[0030] FIG. 7 is a cross-sectional view showing a modification of
fixing a plating target article to a cathode bus bar;
[0031] FIG. 8 is a graph showing variation of plating current
flowing through the plating target article;
[0032] FIG. 9 is a cross-sectional view showing the construction of
a plating apparatus to which a second embodiment of the plating
method of the present invention is applied;
[0033] FIG. 10 is a cross-sectional view showing the construction
of the plating apparatus to which the second embodiment of the
plating method of the present invention is applied;
[0034] FIG. 11 is a plan view showing the construction of the
plating apparatus to which the second embodiment of the plating
method of the present invention is applied;
[0035] FIG. 12 is a cross-sectional view showing a plating
apparatus used for the embodiment of the plating method of the
present invention;
[0036] FIG. 13 is a partially-notched plan view of the plating
apparatus of FIG. 12;
[0037] FIG. 14 is a cross-sectional view showing the fixing of a
vibrational flow inducing portion constituting the plating
apparatus to a plating tank;
[0038] FIG. 15 is a cross-sectional view showing the fixing of the
vibrational flow inducing portion constituting the plating
apparatus to the plating tank;
[0039] FIG. 16 is a plan view showing the fixing of the vibrational
flow inducing portion constituting the plating apparatus to the
plating tank;
[0040] FIGS. 17A to 17C are plan views showing a laminated
member;
[0041] FIGS. 18A and 18B are cross-sectional views showing a state
that the top portion of the plating tank is closed by the laminated
member;
[0042] FIGS. 19A to 19E are diagrams showing the laminated
memeber;
[0043] FIG. 20 is a graph showing variation of plating current
flowing through a plating target article;
[0044] FIG. 21 is a cross-sectional view showing a modification of
the vibrational flow inducing portion;
[0045] FIG. 22 is a plan view showing the vibrational flow inducing
portion of FIG. 21; and
[0046] FIG. 23 is a diagram showing an example of a power source
for pulse plating.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] Preferred embodiments according to the present invention
will be described hereunder with reference to the accompanying
drawings. In the figures, the members or portions having the same
functions are represented by the same reference numerals.
[0048] FIGS. 1 and 2 are cross-sectional views showing the
construction of a plating apparatus to which a first embodiment of
a plating method according to the present invention will be
applied, and FIG. 3 is a plan view of the plating apparatus shown
in FIGS. 1 and 2.
[0049] In these figures, reference numeral 12 represents a plating
tank, and plating bath 14 is stocked in the plating tank 12.
Reference numeral 16 represents a vibrational flow generator or
vibrational flow inducing portion. The vibrational flow generator
16 includes a base stand 16a fixed to the plating tank 12 through a
vibration proof rubber, coil springs 16b serving as vibration
absorption members which are fixed to the base stand at the lower
ends thereof, a vibrating member 16c fixed to the upper ends of the
coil springs 16b, a vibrating motor 16d serving as vibration
generating means fixed to the vibrating member 16c, a vibration
transmitting rod 16e fixed to the vibrating member at the upper end
thereof, and vibrating vanes 16f fixed to the lower half portion of
the vibration transmitting rod so as to be immersed in the plating
bath 14. Further, a rod-shaped guide member may be disposed in each
of the coil springs 16b as shown in FIG. 12.
[0050] The vibrating motor 16d vibrates at frequencies of 10 to 500
Hz, preferably 20 to 60 Hz, more preferably 30 to 50 Hz under the
control based on an inverter, for example. The vibration generated
by the vibrating motor 16d is transmitted through the vibrating
member 16c and the vibration transmitting rod 16e to the vibrating
vanes 16f. The tip edge of each vibrating vane 16f vibrates at a
desired oscillation frequency in the plating bath 14. The vibration
is generated as if each vibrating vane 16f bends from the base
portion fixed to the vibration transmitting rod 16e toward the tip
edge thereof. The amplitude and frequency of the vibration are
different from those of the vibrating motor 16d, and determined in
accordance with the dynamical characteristics of the vibration
transmission passage and the mutual action characteristics between
each vibrating vane and the plating bath 14. In the present
invention, the amplitude is preferably in the range of 0.05 to 10.0
mm, for example 0.1 to 10.0 mm, and the frequency is preferably in
the range of 200 to 1500 revolutions per minute, for example 200 to
800 revolutions per minute.
[0051] FIG. 4 is an enlarged cross-sectional view showing the
fixing portion of the vibration transmitting rod 16e to the
vibrating member 16c. Nuts 16i1, 16i2; 16i3, 16i4 are fixed through
vibrational stress dispersing members 16g1, 16g2 and washers 16h1,
16h2 to a male screw portion of the upper portion of the vibration
transmitting rod 16e from both the upper and lower sides of the
vibrating member 16c. The vibrational stress dispersing members
16g1, 16g2 are formed of rubber, for example.
[0052] FIG. 5 is an enlarged cross-sectional view showing the
fixing portions of the vibrating vanes 16f to the vibration
transmitting rod 16e. Vibrating vane fixing members 16j are
disposed at both the upper and lower sides of each of seven
vibrating vanes 16f. Further, a spacer ring 16k for setting the
interval between the vibrating vanes 16f is interposed between the
neighboring vibrating vanes 16f through the fixing members 16j.
Nuts 16m which are fitted to male screws formed on the vibration
transmitting rod 16e are disposed at the upper side of the
uppermost vibrating vane 16f and the lower side of the lowermost
vibrating vane 16f.
[0053] FIG. 6 is a diagram showing a modification of the fixing
portions of the vibrating vanes 16f to the vibration transmitting
rod 16e.
[0054] In this modification, each vibrating vane 16f is
individually fixed to the vibration transmitting rod 16e by nuts
16n disposed at both the upper and lower sides of each vibrating
vane 16f. An elastic member sheet 16p formed of fluororesin or
fluorinated rubber may be interposed between each vibrating vane
16f and the fixing member 16j to prevent the vibrating vanes 16f
from being damaged.
[0055] As shown in FIG. 6, the lower surface (press face) of the
upper fixing member 16j is designed to have a convex cylindrical
shape, and the upper surface (press face) of the lower fixing
member 16j is designed to have a concave cylindrical shape
corresponding to the above convex cylindrical shape. Therefore, a
part of each vibrating vane 16f which is pressed by the fixing
members 16j from the upper and lower sides is bent, and the tip
portion of the vibrating vane 16f intersects the horizontal plane
at an angle .alpha.. The angle .alpha. may be set to a value in the
range from -30.degree. to 30.degree. , preferably in the range from
-20.degree. to 20.degree.. Particularly, the angle .alpha. is
preferably set to a value in the range from -30.degree. to
-5.degree. or from 5.degree. to 30.degree., preferably in the range
from -20.degree. to -10.degree. or from 10.degree. to 20.degree..
When the press faces of the fixing members 16j are the plane face,
the angle .alpha. is set to 0.degree. . The angle .alpha. is not
necessarily equal to the same value among all the vibrating vanes
16f. For example, as shown in FIG. 1, a negative angle value may be
set to one or two lower vibrating vanes 16f (i.e., the vibrating
vanes 16f are bent downwardly, that is, they are bent in the
opposite direction to that of FIG. 6) while a positive angle value
is set to the other vibrating vanes 16f (i.e., they are bent in the
same direction as that of FIG. 6).
[0056] The vibrating vanes 16f may be formed of elastic metal
plates, synthetic resin plates or rubber plates. The thickness of
each vibrating vane 16f is set so that the tip edge portion of each
vibrating vane 16f exhibits a flutter phenomenon (a state as if the
vibrating vanes are fluttered). When the vibrating vanes 16f are
formed of metal plates such as stainless steel plate or the like,
the thickness thereof may be set to 0.2 to 2 mm. When the vibrating
vanes 16f are formed of synthetic resin plates or rubber plates,
the thickness thereof may be set to 0.5 to 10 mm.
[0057] In FIGS. 1 to 3, a swinging motor 20 is connected to a
swinging frame 24 through a link rod 22. The swinging frame 24 is
disposed so as to be reciprocally movable in the horizontal
direction (the right-and-left direction in FIG. 1) on rails 26. A
vibrating motor 28 is fixed to the swinging frame 24. Further, a
cathode bus bar 30 and an anode bus bar 32 are fixed to the
swinging frame 24 while they are kept insulated from the swinging
frame 24, and they are connected to a negative-electrode terminal
and a positive-electrode terminal of a power source circuit 34. The
power source circuit 34 can generate a rectangular voltage from an
AC voltage. Such a power source circuit has a rectifying circuit
using a transistor and it is known as a pulse power source
device.
[0058] In the present invention, a circuit for rectifying AC
current (containing adding DC components) and then outputting the
rectified current is used as the power source circuit (power source
device) used to generate plating current. As such a power source
device or rectifier may be used a transistor adjustment type power
source, a dropper type power source, a switching power source, a
silicon rectifier, an SCR rectifier, a high-frequency type
rectifier, an inverter digital control type rectifier (for example,
Power Master produced by Chuo Seisakusho Co., Ltd.), KTS series
produced by Sansha Denki Seisakusho Co., Ltd., an RCV power source
produced by Shikoku Denki Co., Ltd., a device which comprises a
switching regulator type power source and a transistor switch and
supplies rectangular pulse current by switching on/off the
transistor switch, a high-frequency switching power source (in
which AC current is converted to DC current through a diode, then
high frequency of 20 to 30 KHz are applied to a transformer to
carry out the rectification and smoothing again, and then the
output is taken out), a PR type rectifier, a high-frequency control
type high-speed pulse PR power source (for example, HiPR series
produced by Chiyoda Co., Ltd. or the like.
[0059] Here, the current waveform will be described. In order to
implement both the increase in plating speed and the improvement of
the characteristics of plating films, it is important to select the
wave form of plating current. The voltage and current conditions
required for the electroplating are varied in accordance with the
type of plating, the composition of plating bath and the dimension
of the plating tank, and thus they cannot be sweepingly specified.
However, if the plating voltage is set to a DC voltage of 2 to 15V,
it can sufficiently cover the whole at present. Therefore, four
kinds of rated output voltage of the plating DC current (6V, 8V,
12V, 15V) are standardized in the industry. The voltage below the
above rated can be adjusted, and thus a power source for generating
a rated voltage which has a slightly extra voltage with respect to
a desired voltage value required for plating is preferably
selected. In the industry, the rated output current from 500 A,
1000 A till about 2000 A to 10000 A are standardized as the rated
output current of the power source, and the other current values
are provided in the form of production to order. It is better that
the required current capacity of the power source is determined as
the desired current density of plating target article x the surface
area of the plating target article in accordance with the type and
surface area of the plating target article, and a proper standard
power source satisfying the above required current capacity is
selected.
[0060] The pulse wave is originally defined as a pulse having a
sufficiently shorter width w than its period T. However, this
definition is not strict. The pulse wave contains waves other than
the square wave. The operating speed of elements used in a pulse
circuit is increased, and the pulse width of ns (10.sup.-9s) or
less can be treated. As the pulse width is smaller, it is more
difficult to keep the front and rear edges of the waves sharp. This
is because the pulse contains high-frequency components.
[0061] A saw-tooth wave, a ramp wave, a triangular wave, a
composite wave, a rectangular wave (square wave), etc. are known as
the types of pulse waves, and particularly the present invention
preferably uses the rectangular wave in consideration of the
efficiency of electricity and smoothing.
[0062] FIG. 23 shows an example of a pulse plating power source. As
shown in FIG. 23, it contains a switching regulator type DC power
source and a transistor switch, and rectangular pulse current is
supplied to a load by switching on/off the transistor switch at
high speed.
[0063] The cathode bus bar 30 is mechanically and electrically
connected to the upper portion of an electrically conductive
holding member 40 for holding a plating target article X. The lower
portion of the plating target article holding member 40 is immersed
in the plating bath 14, and the plating target article X is
electrically connected to this portion and held by a clamp or the
like. As not shown, an anode metal member (for example, which is
accommodated in a plastic basket) is mechanically and electrically
connected to the anode bus bar 32, and the lower portion thereof is
immersed in the plating bath 14. Various well-known methods, shapes
and structures may be used as the methods of fixing the plating
target article to the cathode bus bar and fixing the anode metal
member to the anode bus bar and the shapes and structures of the
cathode bus bar and the anode bus bar.
[0064] FIG. 7 is a cross-sectional view showing a modification of
the fixing of the plating target article to the cathode bus bar. In
this modification, the electrically conductive holding member 40 is
designed to have a hook portion 40a which is provided at the upper
portion thereof and fitted to the cathode bus bar 30, a clamp
portion 40b which is provided at the lower portion thereof and
pinches the plating target article X, and a compression spring 40c
for generating the clamp force of the clamp portion.
[0065] In FIGS. 1 to 3, the swinging frame 24 and the holding
member 40, and further the plating target article X secured to the
swinging frame 24 and the holding member 40 are swung at a swinging
width of 10 to 100 mm and a swinging frequency of 10 to 30 times
per minute by actuating the swinging motor 20. Further, the
vibrating motor 28 is vibrated at a frequency of 10 to 60 Hz,
preferably at a frequency of 20 to 35 Hz under the control using an
inverter, for example. The vibration occurring in the vibrating
motor 28 is transmitted to the plating target article X through the
swinging frame 24 and the holding member 40, whereby the plating
target article X is vibrated at an amplitude of 0.05 to 5.0 mm, for
example 0.1 to 5.0 mm, and a vibration frequency of 100 to 300
revolutions per minute.
[0066] FIG. 8 is a graph showing the variation of plating current
(current density) flowing through the plating target article X due
to a voltage applied across the cathode bus bar 30 and the anode
bus bar 32 by the power source circuit 34.
[0067] As shown in FIG. 8, the plating current is shaped to have
such a rectangular pulse train that a first state where the plating
current keeps a first value I1 for a first time T1 and a second
state where the plating current keeps a second value I2 (<I1)
for a second time T2 appear alternately. Here, the first value I1
and the second value I2 have the same polarity. I1 is five or more
times as large as I2 (for example, six or more times, e.g. six
times to 25 times), preferably eight times to 20 times. T1 is three
or more times as long as T2 (for example, four or more times, e.g.
4 times to 25 times), preferably six times to 20 times. Such
plating current and the vibrational flow of the plating bath 14
caused by the vibrational flow generator 16 are combined with each
other, whereby excellent quality and a high film forming speed can
be achieved even for the plating of minute conductive structure
patterns.
[0068] The first value I1 and the first time T1 are properly
determined in accordance with the type of plating (for example,
copper sulfate plating, copper cyanide plating, copper
pyrophosphate plating, nickel plating, black nickel plating, nickel
sulfamate plating, chromium plating, zinc cyanide plating, no
cyanide zinc plating, alkaline tin plating, acidic tin plating,
silver plating, gold cyanide plating, acidic gold plating,
copper-zinc alloy plating, nickel-iron alloy plating, tin-lead
alloy plating, palladium plating, solder plating or the like), the
composition of the plating bath or the like. For example, I1 may be
set to a value in the range of 0.01 to 100[A/dm.sup.2], and T1 may
be set to a value in the range from 0.01 to 300[Second], e.g. from
3 to 300[Second]. However, these parameters are not limited to
specific values. The optimum I1, I2, T1, T2 may vary in a broad
range in accordance with the type of plating, the composition of
the plating bath or the like. For example, they may vary due to
variation of the composition of the plating bath in the progress of
the plating treatment.
[0069] The plating bath 14 is selected in the same way as the
well-known electroplating method in accordance with a plating film
to be formed. For example, in the case of the copper sulfate
plating, the following may be used as through hole bath:
[0070] Copper sulfate: 60 to 100 g/L (liter)
[0071] Sulfuric acid: 170 to 210 g/L
[0072] Brightener: proper amount
[0073] Chlorine ion: 30 to 80 mL/L
[0074] The following may be used as normal bath for the copper
sulfate plating:
[0075] Copper sulfate: 180 to 250 g/L
[0076] Sulfuric acid: 45 to 60 g/L
[0077] Brightener: proper amount
[0078] Chlorine ion: 20 to 80 m/L
[0079] Further, in the case of the nickel plating, the following
may be used as barrel bath:
[0080] Nickel sulfate: 270 g/L
[0081] Nickel chloride: 68 g/L
[0082] Boric acid: 40 g/L
[0083] Magnesium sulfate: 225 g/L
[0084] The following may be used as normal bath for the nickel
plating:
[0085] Nickel sulfate: 150 g/L
[0086] Ammonium chloride: 15 g/L
[0087] Boric acid: 15 g/L
[0088] The following may be used as Watts bath for the nickel
plating:
[0089] Nickel sulfate: 240 g/L
[0090] Ammonium chloride: 45 g/L
[0091] pH: 4 to 5
[0092] bath temperature: 45 to 55.degree. C.
[0093] Further, in the case of the acidic tin plating, the
following may be used as sulfate bath:
[0094] Stannous sulfate: 50 g/L
[0095] Sulfuric acid: 100 g/L
[0096] Cresolsulfonic acid: 100 g/L
[0097] Gelatin: 2 g/L
[0098] .beta.-naphthol: 1 g/L
[0099] Electronic parts, mechanical parts, etc. may be used as
articles X to be plated, and the articles X are not limited to
specific ones. The present invention is remarkably effectively
applied to a case where a plating film having a microstructure is
formed. Particularly, the following cases may be considered as the
plating of these articles X: formation of a plating conductive film
onto the inner surface of a minute blind via hole or through hole
having an inner diameter of 100 .mu.m or less (for example, 20 to
100 .mu.m, or particularly 50 .mu.m or less, further 30 .mu.m or
less, e.g. 10 .mu.m, 5 .mu.m, 3 .mu.m, etc.) and having a depth of
10 to 100 .mu.m for example in a multi-layered wiring board;
formation of a conductive film in a minute groove to form a
high-density wiring pattern having a pitch of 50 .mu.m or less (for
example, 20 to 50 .mu.m, or particularly 30 .mu.m or less, further
20 .mu.m or less, e.g. 10 .mu.m, 5 .mu.m, etc.), the minute groove
having a width of 30 .mu.m or less (particularly 20 .mu.m or less,
further 10 .mu.m or less, e.g. 5 .mu.m, 3 .mu.m, etc.) and depth of
7 to 70 .mu.m for example; formation of an embedded conductive film
into an extremely minute blind via hole having an inner diameter of
about 0.3 .mu.m or less or into an extremely minute groove having a
width of 0.1 .mu.m and depth of 1.5 .mu.m by copper damascene
method when multi-layered wires of a semiconductor device are
formed; formation of minute electrode bumps disposed in a
high-density arrangement in a semiconductor device; etc. The
improving effect of the present invention is particularly
remarkable when it is applied to the structure having a high aspect
ratio, for example 3 or more, especially 5 or more.
[0100] Further, an extremely small article having an average
diameter of 5 to 500 .mu.m may be used as the plating target
article X. Here, the average diameter is defined as the average
value of representative dimensions in the three directions that
cross to one another at right angles. As this type of plating
target article X may be provided metal powder such as copper
powder, pre-treated aluminum powder or iron powder, synthetic resin
powder such as ABS resin powder or the like which is treated to
have electrical conductivity, ceramic chips which are treated to
have electrical conductivity, etc. Further, other electronic parts,
mechanical parts, metal powder alloy, minute particulate
inorganic/organic pigment, metal balls, etc. may be also
provided.
[0101] For example, Ni plating films may be formed on metal
particles such as Cu particles each having a diameter of about 300
.mu.m, or an Au plating film or an Ag plating film may be formed on
an Ni plating film to form a composite plating film.
[0102] Further, when a plating target article is made of
electrically insulating material such as plastic or the like, a
conductive base (primer) forming treatment is carried out as a
pre-treatment of the electroplating. However, in the case of a
microstructured plating face having a high aspect ratio, an uniform
and excellent conductive base could not be formed even if the
conductive base forming treatment is carried out by normal
electroless plating. Therefore, the thickness of the plating film
obtained by the electroplating is liable to be non-uniform. In
order to avoid this problem, the conductive base forming treatment
may be carried out by sputtering or vacuum deposition. However, in
this case, since the treatment is carried out in a pressure-reduced
apparatus, there occur such difficulties that the cost of the
treatment apparatus rises up and a mass-production treatment and a
continuous treatment cannot be performed. On the other hand, if the
conductive base forming treatment using the electroless plating or
the like is carried out while vibrational flow is induced in
treatment liquid by using the same means as the vibrational flow
generating means used in the present invention, a highly uniform
conductive base can be formed on even a microstructured plating
face having a high aspect ratio. Accordingly, by combining the
conductive base forming treatment and the electroplating method of
the present invention, the process from the pre-treatment to the
electroplating treatment can be continuously carried out, and thus
the productivity can be enhanced more and more.
[0103] According to the plating method of the present invention,
the distribution of the plating bath into microstructure recess
portions can be enhanced by the vibrational flow which is induced
in the plating bath 14 by the vibrational flow generator 16, and
also the uniformity in film thickness can be enhanced by pulsing
the plating current density so that a first pulse state and a
second pulse state where the pulsed current density has the same
polarity as that of the first pulse state although it is
sufficiently lower than that of the first state. Therefore, there
can be suppressed occurrence of non-uniformity in film thickness
due to concentrated plating film formation at the projecting
portions or edge portions and also occurrence of defects such as
gas pits, etc. in through holes or via holes as in the case of the
DC plating process, and high surface glossiness can be achieved.
Further, there can be prevented such a phenomenon that a plating
film which has been temporarily formed is partially dissolved as in
the case of the pulse plating current whose polarity is inverted.
Therefore, a high-speed film forming process can be carried out and
the construction of the manufacturing apparatus can be simplified.
Accordingly, desired plating films can be efficiently formed with
low fraction defective at high speed on broad plating target
articles.
[0104] Further, according to the present invention, short-circuit
can be prevented by the action of the vibrational flow occurring in
the plating bath 14 even when the distance between the plating
target article X and the anode metal member is short to increase
the current density. This is considered as a factor to form a
plating film with an excellent yield and at high speed without
inducing disadvantages such as burning, scorching, etc.
[0105] In order to attain such an excellent action, it is
remarkably preferable that the three-dimensional flow rate of the
vibrational flow of the plating bath 14 is equal to or greater than
150 mm per second. Such a high three-dimensional flow rate can be
effectively implemented by inducing the vibrational flow in the
plating bath. It is difficult to implement this three-dimensional
flow rate by using a normal stirrer, and even when it is
implemented, an extremely large scale apparatus is needed.
[0106] In this embodiment, the effect can be further enhanced by
swinging and/or vibrating the plating target article X through the
swing and/or vibration of the swinging frame 24. However, an
excellent effect can be obtained even when the plating target
article X is neither swung nor vibrated. If the cathode bus bar 30,
the anode bus bar 32, the plating target article X, the anode metal
member, etc. are supported without using the swinging frame 24, the
swinging motor 20 and the vibrating motor 28, the construction of
the apparatus can be further simplified. When the plating target
article X has a plate shape of a relatively large dimension or
length as a whole such as a multi-layered wiring board or the like,
the effect can be enhanced by swinging the plating target article X
along the in-plane direction thereof.
[0107] FIGS. 9 and 10 are cross-sectional views showing the
construction of a plating apparatus to which a second embodiment of
the plating method according to the present invention is applied,
and FIG. 11 is a plan view showing the plating apparatus shown in
FIGS. 9 and 10. This embodiment is different from the first
embodiment shown in FIGS. 1 to 8 in the way to hold the plating
target article X and the way to supply current to the plating
target article, and it uses a so-called barrel plating method.
[0108] In FIGS. 9 to 11, a vibrating frame 44 is fitted to a
plating tank 12 through a coil spring 46 as a vibration absorption
member. The vibrating frame 44 is fitted to a vibrating motor 48
and a balance weight 49 used to keep a weight balance with the
vibrating motor 48. A barrel 52 is fitted to the vibrating frame 44
through a support member 50. The barrel 52 is rotatably fitted to
the support member 50, and rotated in the direction indicated by an
arrow of FIG. 9 by driving means (not shown). Many minute plating
target articles X are accommodated in the barrel 52. Many small
holes are formed on the outer peripheral surface of the barrel 52
so that the plating target articles X are prevented from passing
through the small holes, but the liquid of the plating bath 14 is
allowed to pass through the small holes. A cathode conductive
member 54 is disposed in the barrel 52 so as to extend to the lower
portion of the barrel 52. The cathode conductive member 54 is
connected to a negative-electrode terminal of a power source
circuit 34 via an insulated coated wire 54' which passes through a
pipe member 52a fixed to the barrel 52 at the rotational center of
the barrel 52. The cathode conductive member 54 is not rotated even
when the barrel is rotated, and thus the plating target articles X
which are rolled through the rotation of the barrel repetitively be
in contact with and separate from the cathode conductive member
54.
[0109] Reference numeral 56 represents an anode metal member having
a lower portion immersed in the plating bath 14. The anode metal
member 56 is accommodated in a plastic cage, for example, and is
connected to a positive-electrode terminal of the power source
circuit 34 through an insulated coated wire 56'. As shown in FIG.
9, the anode metal member 56 is disposed at both the sides of the
barrel 52, however, it may be disposed at one side of the anode
metal member 56.
[0110] The vibrating motor 48 is vibrated at the same amplitude and
frequency as the vibrating motor 28 described above, and the
plating target articles X are vibrated at an amplitude of 0.05 to
5.0 mm, for example 0.1 to 5.0 mm, and a vibrational frequency of
100 to 300 revolutions per minute. In this embodiment, the effect
is also further enhanced by vibrating the plating target articles
through the vibration of the vibrating frame 44. However, an
excellent effect can be achieved without vibrating the plating
target articles X. The construction of the apparatus can be further
simplified by supporting the support member 50 and the barrel 52
without using the vibrating frame 44, the vibrating motor 48,
etc.
[0111] In this embodiment, the plating current density is set in
the same way as described with reference to FIG. 8. In this
embodiment, the plating current in the first pulse state or second
pulse state or the plating current varying in the shift process
between the first pulse state and the second pulse state is
supplied to each plating target article X when each plating target
article X is brought into contact with the cathode conductive
member 54. If only the current density at the contact time is
continuously displayed, the same current density as shown in FIG. 8
is obtained on average, and thus the same effect as the first
embodiment can be obtained.
[0112] This embodiment is more effectively applied to a case where
formation of electrode films on plating target articles X having
extremely small dimensions, for example, chip parts such as ceramic
chip capacitors of about 0.6 mm.times.0.3 mm.times.0.2 mm in
dimension or the like, or formation of plating films on pins of
about 0.5 mm in diameter x about 20 mm in length is carried out on
a large number of plating target articles at the same time. As
described above, when such a minute article that the dimension in
the direction traversing the longitudinal direction, that is, the
width is equal to 5 mm or less, further 2 mm or less, still further
1 mm or less is used as the plating target article, the improving
effect in the uniformity of the plating film thickness and the film
forming speed is greater. Besides, metal powder alloy,
inorganic/organic pigment particulates, metal balls may be targeted
as the plating target articles.
[0113] As a matter of course, a desired pre-treatment is carried
out before the electroplating method of the present invention is
carried out. The pre-treatment is carried out in the same manner as
the well-known electroplating method.
[0114] Further, a vibrational flow generator disclosed in
JP(A)-11-189880 (in which vibrating vanes are disposed at the
bottom portion of a plating tank, and vibration is transmitted from
a vibrating motor through a vibration transmitting frame to the
vibrating vanes to vibrate the vibrating vanes in the horizontal
direction, as described with reference to FIGS. 7 and 8 of this
publication) or ones disclosed in publications other than the above
publication may be properly used as the vibrational flow generator
having the vibrating vanes for generating vibrational flow in the
plating path in the method of the present invention.
[0115] For example, vibrational flow generators shown in FIGS. 21
and 22 may be used. In FIGS. 21 and 22, two vibrational flow
generators 16 are supported by a support frame 15 fixed to a
support stand 13 on which a plating tank 12 is mounted. In each of
the vibrational flow generators 16, the upper end portion of a
vibration transmitting rod 16e" extending in the up-and-down
direction is fixed to a vibrating member 16c' for receiving
vibration transmitted from a vibrating motor 16d. The vibration
transmitting rod 16e" extends into the plating tank 12, and the end
portion of the vibration transmitting rod 16e' in the horizontal
direction is fixed to the lower end of the vibration transmitting
rod 16e". The vibration transmitting rods 16e' are commonly used by
the two vibrational flow generators 16, and vibrating vanes 16f
extending in the up-and-down direction are fixed to the vibration
transmitting rods 16e'. The vibration is transmitted from the
vibrating motors 16d through the vibrating members 16c' and the
vibration transmitting rods 16e" and 16e' to the vibrating vanes
16f to vibrate the vibrating vanes 16f in the horizontal
direction.
[0116] FIG. 12 is a cross-sectional view showing another embodiment
of the plating apparatus used in the embodiment of the plating
method according to the present invention, and FIG. 13 is a
partially notched plan view of the plating apparatus of FIG. 12. In
this embodiment, the construction of the vibrational flow generator
16 is different from that of the above embodiment. That is, the
lower end of a coil spring 16d is fixed to a fixing member 118
fixed to the upper end edge portion of the plating tank 12, and a
vibrating motor 16d is fixed to the lower side of a vibrating
member 16c to which the upper end of the coil spring 16b is fixed.
A lower guide member 124 whose lower end is fixed to the fixing
member 118 and an upper guide member 123 whose upper end is fixed
to the vibrating member 16c are disposed in the coil spring 16b so
as to be spaced from each other at a proper distance.
[0117] FIGS. 14 and 15 are cross-sectional views of another
embodiment of the fixing portion of the vibrational flow generator
to the plating tank in the plating apparatus used in the embodiment
of the plating method according to the present invention, and FIG.
16 is a plan view of this embodiment. FIGS. 14 and 15 are views
taken along lines X-X' and Y-Y' of FIG. 16, respectively. In these
figures, the cathode, anode, power source circuit, etc. for plating
are not shown.
[0118] In this embodiment, a laminated member 3 made of a rubber
plate 2 and metal plates 1, 1' is used as a vibration absorbing
member instead of the coil spring 16b of the above embodiments. The
laminated member 3 is formed by fixing the metal plate 1' via a
rubber vibration insulator 112 to a support member 118 connected to
the upper end of the plating tank 12 by means of a bolt 131,
disposing the rubber plate 2 on the metal plate 1', disposing the
metal plate 1 on the rubber plate 2, and fixing the metal plates 1,
1' and rubber plate 2 by means of a bolt 116 and nut 117 to be
integrated.
[0119] A vibrating motor 16d is fixed to the metal plate 1 via a
support member 115 by a bolt 132. The upper end portion of a
vibration transmitting rod 16e is connected via a rubber ring 119
to the laminated member 3, especially to the metal plate 1 and
rubber plate 2. That is, the upper side metal plate 1 functions as
the vibrating member 16c of the embodiment of FIG. 1, etc., and the
lower side metal plate 1' functions as the base stand 16a of the
embodiment of FIG. 1, etc. The laminated member 3 containing the
metal plate 1, 1', especially the rubber plate 2, has the same
vibration absorbing function as the coil spring 16b of the
embodiment of FIG. 1, etc.
[0120] FIGS. 17A to 17C show schematic plan views of an embodiment
of the laminated member 3. In the embodiment of FIG. 17A
corresponding to the above embodiment of FIGS. 14 to 16, there is
provided a hole 5 through which the vibration transmitting rod 16e
passes. In the embodiment of FIG. 17B, the laminated member 3
comprises a first portion 3a and a second portion 3b, the facing
edges of which are contacted with each other. According to this
embidiment, the vibration transmitting rod 16e can be easily set to
the laminated member 3 through the hole 5 thereof when assembling
the apparatus. In the embodiment of FIG. 17C, the laminated member
3 is formed so as to have a ring shape corresponding to the shape
of the upper edge portion of the plating tank 12, and has an
opening 6 positioned at the center thereof.
[0121] According to the embodiments of FIGS. 17A and 17B, the
plating tank 12 is sealed with the laminated member 3, and
therefore gas evaporated from the plating bath 14 and plating
liquid splashed from the plating bath 14 are prevented from leaking
to the environment.
[0122] FIGS. 18A and 18B show cross-sectional views of the above
sealing of the plating tank with the laminated member 3. In the
embodiment of FIG. 18A, the sealing of the plating tank 12 is
performed by contacting the inner surface of the hole 5 of the
rubber plate 2 with the vibration transmitting rod 16e. In the
embodiment of FIG. 18B, there is provided a flexible sealing member
136 attached to the opening 6 of the laminated member 3 and the
vibration transmitting rod 16e to seal the space existing
therebetween.
[0123] FIGS. 19A to 19E show examples of the laminated member 3 as
the vibration absorbing member. The laminated member 3 of FIG. 19B
is the same as that of FIGS. 14 to 16. The laminated member 3 of
FIG. 19A comprises metal plate 1 and rubber plate 2. The laminated
member 3 of FIG. 19C comprises upper metal plate 1, upper rubber
plate 2, lower metal plate 1' and lower rubber plate 2'. The
laminated member 3 of FIG. 19D comprises upper metal plate 1, upper
rubber plate 2, intermediate metal plate 1", lower rubber plate 2'
and lower metal plate 1'. The number of the metal plate or rubber
plate is 1 to 5 for example. In the present invention, the
vibration absorbing member may be formed only of the rubber
plate(s).
[0124] Examples of material of the metal plates 1, 1', 1" are
stainless steel, iron, copper, aluminum, suitable alloys, etc. The
thickness of the metal plates 1, 1', 1" is 10 to 40 mm for example.
However, the metal plate, for example the intermediate metal plate
1", which is not fixed to any member other than the member
constituting the laminated member may be made so thinner as to have
the thickness of 0.3 to 10 mm for example.
[0125] Material of the rubber plate 2, 2' is, for example,
synthetic rubber or vulcanized natural rubber, and preferably
rubber vibration isolator defined in JIS K6386 (1977), especially
having static modulus of elasticity in shear of 4 to 22
kgf/cm.sup.2, preferably 5 to 10 kgf/cm.sup.2, and ultimate
elongation of 250% or more.
[0126] Examples of synthetic rubber are chloroprene rubber, nitrile
rubber, nitrile-chloroprene rubber, styrene-chloroprene rubber,
acrylonitrile-butadiene rubber, isoprene rubber,
ethylene-propylene-diene rubber, epichlorohydrin rubber, alkylene
oxide rubber, fluororubber, silicone rubber, urethane rubber,
polysulfide rubber, phosphorus rubber (flame-retarded rubber). The
thickness of the rubber plate is 5 to 60 mm for example.
[0127] The laminated member 3 of FIG. 19E comprises upper metal
plate 1, lower metal plate 1', and rubber plate 2 which comprises
an upper solid rubber layer 2a, sponge rubber layer 2b and lower
solid rubber layer 2c. One of the upper and lower solid rubber
layers 2a, 2c may be omitted. Alternatively, a plurality of sponge
rubber layers and a plurality of solid rubber layers may be used in
the rubber plate.
[0128] FIG. 20 is a graph showing a modification of the variation
of the plating current (current density) flowing through the
plating target article X due to the voltage applied across the
cathode bus bar 30 and the anode bus bar 32 by the power source
circuit 34. In this modification, the current density waveforms of
the first and second states are not the rectangular form as shown
in FIG. 8, but contain a little pulsation as shown in FIG. 20. Such
pulsation is based on the construction of the power source circuit
34, and the plating current used in the present invention may be
pulsated current as shown in FIG. 20. The peak values in the first
and second states may be used as the current values I1 and I2 in
the first and second states, respectively.
[0129] In the present invention, the power source circuit 34 may
comprise a voltage supply system for the first state and another
voltage supply system for the second state. In this case, the
voltages of these voltage supply systems are alternately output
(i.e., this power source circuit is functionally equivalent to the
switching operation of two power source devices).
[0130] The combination technique of the vibrational flow of the
plating bath and the pulsed plating current as described above may
be applied to an anodizing method, an electrolytic polishing
method, an electrolytic degreasing method, etc. in which the
surface treatment of target objects is carried out by utilizing
current flow in a treatment bath. The target objects are disposed
at the anode side or cathode side in accordance with the treatment
content. By using this combination technique, the surface treatment
on target articles having microstructures can be excellently
performed.
[0131] The present invention will be described in more detail with
the following examples.
EXAMPLE 1
[0132] The apparatus described with reference to FIGS. 1 to 3 was
used. Here, a vibrating motor of 150 W.times.200V.times.3.phi. was
used as the vibrating motor 16d, a plating tank having a volume of
300 liters was used as the plating tank 12, and Power Master
(available from Chuo Seisakusho, Co., Ltd.) was used as the power
source circuit 34.
[0133] 8-Inch (diameter of 200 mm) silicon wafers which were
subjected to a predetermined pre-treatment by the conventional
method were used as the plating target articles X, and a process of
forming copper-embedded conductive film in blind via holes coated
with a copper seed layer in the copper damascene method was carried
out. Many blind via holes were formed in a titanium nitride
insulation layer of 0.35 .mu.m in thickness to have an inner
diameter of 0.24 .mu.m.
[0134] The following through hole bath of copper sulfate plating
was used as the plating bath 14:
[0135] Copper sulfate: 75 g/L
[0136] Sulfuric acid: 190 g/L
[0137] Brightener: proper amount
[0138] Chlorine ion: 40 mL/L
[0139] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 45 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.2 mm and a vibration frequency of 650 revolutions
per minute in the plating bath 14. Further, the vibrating motor 28
was vibrated at 25 Hz to vibrate the plating target articles X at
an amplitude of 0.15 mm and a vibration frequency of 200
revolutions per minute in the plating bath 14. The
three-dimensional flow rate in the plating bath at this time was
measured as 200 mm/second by a three-dimensional electromagnetic
flowmeter ACM300-A (available from Alec Electronics Co., Ltd.).
[0140] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=6[A/wafer]=3[A/dm.sup.2], I2=0.6[A/wafer],
T1=10[second], T2=1[second].
[0141] When the treatment was carried out for 10 minutes, it was
found on the basis of a current flowing test, microscopy and other
tests that excellent copper plating films of about 10 .mu.m in
thickness were formed and embedded in all the blind via holes.
COMPARATIVE EXAMPLE 1-1
[0142] The same treatment as Example 1, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that excellent embedding
of copper plating film was carried out in some (58%) of the many
blind via holes, however, was not carried out in the other blind
via holes.
COMPARATIVE EXAMPLE 1-2
[0143] The same treatment as Example 1, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the current flowing test, microscopy and other tests that
excellent embedding of copper plating film was carried out in some
(10%) of the many blind via holes, however, was not carried out in
the other blind via holes (defectives due to burning, scorching or
the like occurred).
EXAMPLE 2
[0144] The plating conductive films were formed on the inner
surfaces of through holes by using the apparatus described with
reference to FIGS. 1 to 3 (the vibrating motor 16d, the plating
tank 12 and the power source circuit 34 were the same as Example 1)
and using as the plating target article X an A4-size multi-layered
wiring board which was subjected to the pre-treatment by the
conventional method. Many through holes had an inner diameter of 30
.mu.m.phi. and an aspect ratio of 10.
[0145] The following normal bath of copper sulfate plating was used
as the plating bath 14:
[0146] Copper sulfate: 200 g/L
[0147] Sulfuric acid: 50 g/L
[0148] Brightener: proper amount
[0149] Chlorine ion: 60 mL/L
[0150] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 50 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.2 mm and a vibration frequency of 700 revolutions
per minute in the plating bath 14. Further, the vibrating motor 28
was vibrated at 25 Hz to vibrate the plating target articles X at
an amplitude of 0.15 mm and a vibration frequency of 200
revolutions per minute in the plating bath 14. Further, the
swinging motor 20 was driven to swing the plating target articles X
at a swinging width of 30 mm and a swinging frequency of 20 times
per minute. The three-dimensional flow rate in the plating bath at
this time was measured as 200 mm/second by the three-dimensional
electromagnetic flowmeter ACM300-A.
[0151] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=4[A/dm.sup.2], I2=0.4[A/dm.sup.2], T1=180[second],
T2=20[second].
[0152] When the treatment was carried out for 10 minutes, it was
found on the basis of a current flowing test, microscopy and other
tests that excellent copper plating films were formed in 99.9%
through holes.
COMPARATIVE EXAMPLE 2-1
[0153] The same treatment as Example 2, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that excellent copper
plating films were formed over the overall length in some (50%) of
the many through holes, however, no excellent copper plating film
was formed in the other through holes.
COMPARATIVE EXAMPLE 2-2
[0154] The same treatment as Example 2, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the current flowing test, microscopy and other tests that
excellent copper plating films were formed in some (10%) of the
many through holes, however, no excellent copper plating film was
formed in the other through holes (defectives due to burning,
scorching or the like occurred).
EXAMPLE 3
[0155] The apparatus described with reference to FIGS. 9 to 11 (the
vibrating motor 16d, the plating tank 12 and the power source
circuit 34 were the same as Example 1), and 800 ceramic chips of
0.6 mm.times.0.3 mm.times.0.2 mm in dimension which were subjected
to the pre-treatment by the conventional method were used as
plating target articles X. Nickel plating films to form electrode
films were formed on the end surfaces at both ends of each ceramic
chip in the longitudinal direction thereof and on a part (an area
located within 0.1 mm from both the end surfaces) of the 0.6
mm.times.0.3 mm surface adjacent to the end surfaces.
[0156] The following barrel bath was used as the nickel plating
bath 14:
[0157] Nickel sulfate: 270 g/L
[0158] Nickel chloride: 68 g/L
[0159] Boric acid: 40 g/L
[0160] Magnesium sulfate: 225 g/L
[0161] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 55 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.2 mm and a vibration frequency of 750 revolutions
per minute in the plating bath 14. The vibrating motor 48 was
vibrated to vibrate the target plating articles at an amplitude of
0.15 mm and a vibration frequency of 250 revolutions per minute in
the plating bath 14. The three-dimensional flow rate in the plating
bath at this time was measured as 210 mm/second by the
three-dimensional electromagnetic current meter ACM300-A. The
barrel 52 having a mesh opening ratio of 20% was used, and the
rotational number of the barrel was set to 10 rpm.
[0162] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=0.4[A/dm.sup.2], I2=0.04[A/dm.sup.2], T1=20[second],
T2=2[second].
[0163] When the treatment was carried out at 50.degree. C. for 30
minutes, it was found on the basis of a current flowing test,
microscopy and other tests that excellent nickel plating films of
about 2 .mu.m in thickness were formed in all the ceramic
chips.
COMPARATIVE EXAMPLE 3-1
[0164] The same treatment as Example 3, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that excellent nickel
plating films were formed in some (12%) of the ceramic chips,
however, no excellent nickel plating film was formed in the other
ceramic chips.
COMPARATIVE EXAMPLE 3-2
[0165] The same treatment as Example 3, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the current flowing test, microscopy and other tests that
excellent nickel plating films were formed in some (60%) of the
ceramic chips, however, no excellent nickel plating film was formed
in the other ceramic chips.
EXAMPLE 4
[0166] In place of the nickel plating, tin plating was carried out
in the same way as Example 3. The following sulfate bath of acidic
tin plating was used as the plating bath 14:
[0167] Stannous sulfate: 50 g/L
[0168] Sulfuric acid: 100 g/L
[0169] Cresolsulfonic acid: 100 g/L
[0170] Gelatin: 2 g/L
[0171] .beta.-naphthol 1 g/L
[0172] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=0.4[A/dm.sup.2], I2=0.04[A/dm.sup.2], T1=20[second],
T2=2[second].
[0173] When the treatment was carried out at 50.degree. C. for 60
minutes, it was found on the basis of a current flowing test,
microscopy and other tests that excellent tin plating films were
formed in all the ceramic chips.
COMPARATIVE EXAMPLE 4-1
[0174] The same treatment as Example 4, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that excellent tin plating
films were formed in some (10%) of the ceramic chips, however, no
excellent tin plating film was formed in the other ceramic
chips.
COMPARATIVE EXAMPLE 4-2
[0175] The same treatment as Example 4, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the current flowing test, microscopy and other tests that
excellent tin plating films were formed in some (57%) of the
ceramic chips, however, no excellent tin plating film was formed in
the other ceramic chips.
EXAMPLE 5
[0176] The apparatus described with reference to FIGS. 9 to 11 (the
vibrating motor 16d, the plating tank 12 and the power source
circuit 34 were the same as Example 1), and 30 brass pins of 0.5
mm.phi. in outer diameter and 20 mm in length which were subjected
to the pre-treatment by the conventional method were used as
plating target articles X. Nickel plating films were formed on the
outer surfaces of the pins.
[0177] The following barrel bath was used as the nickel plating
bath 14:
[0178] Nickel sulfate: 270 g/L
[0179] Nickel chloride: 68 g/L
[0180] Boric acid: 40 g/L
[0181] Magnesium sulfate: 225 g/L
[0182] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 45 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.2 mm and a vibration frequency of 500 revolutions
per minute in the plating bath 14. The vibrating motor 48 was
vibrated to vibrate the target plating articles at an amplitude of
0.15 mm and a vibration frequency of 200 revolutions per minute in
the plating bath 14. The three-dimensional flow rate in the plating
bath at this time was measured as 200 mm/second by the
three-dimensional electromagnetic current meter ACM300-A. The
barrel 52 having a mesh opening ratio of 20% was used, and the
rotational number of the barrel was set to 10 rpm.
[0183] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=3[A/dm.sup.2], I2=0.3[A/dm.sup.2], T1=30[second],
T2=3[second].
[0184] When the treatment was carried out at 50.degree. C. for 20
minutes, it was found on the basis of the measurement of the
thickness of the nickel plating films, current flowing test,
microscopy and other tests that excellent nickel plating films
having excellent uniformity in thickness were formed in all the
pins.
COMPARATIVE EXAMPLE 5-1
[0185] The same treatment as Example 5, except for the condition:
T2=0[second], was carried out. It was proved from the measurement
of the thickness of the nickel plating films, the current flowing
test, microscopy and other tests that excellent nickel plating
films were formed on some (17%) of the pins, however, no excellent
nickel plating film was formed on the other pins.
COMPARATIVE EXAMPLE 5-2
[0186] The same treatment as Example 5, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the measurement of the thickness of the nickel plating films,
the current flowing test, microscopy and other tests that excellent
nickel plating films were formed in some (60%) of the pins,
however, no excellent nickel plating film was formed on the other
pins (defectives due to burning, scorching or the like
occurred).
EXAMPLE 6
[0187] The apparatus described with reference to FIGS. 9 to 11 (the
vibrating motor 16d, the plating tank 12 and the power source
circuit 34 were the same as Example 1), and about 30000 spheres of
acrylonitrile-butadiene-styrene copolymer (ABS resin) each of which
had a diameter of 3 mm.phi. and was subjected to the pre-treatment
(containing a degreasing treatment and a charging treatment) by the
conventional method were used as plating target articles X. Copper
plating films were formed on the outer surfaces of the spheres.
[0188] The following was used as the plating bath 14:
[0189] Copper sulfate: 200 g/L
[0190] Sulfuric acid: 50 g/L
[0191] Brightener: proper amount
[0192] Chlorine ion: 40 mL/L
[0193] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 40 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.2 mm and a vibration frequency of 700 revolutions
per minute in the plating bath 14. The vibrating motor 48 was
vibrated to vibrate the target plating articles X at an amplitude
of 0.15 mm and a vibration frequency of 250 revolutions per minute
in the plating bath 14. The three-dimensional flow rate in the
plating bath at this time was measured as 210 mm/second by the
three-dimensional electromagnetic current meter ACM300-A. The
barrel 52 having a mesh opening ratio of 20% was used, and the
rotational number of the barrel was set to 10 rpm.
[0194] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=0.5[A/dm.sup.2], I2=0.04[A/dm.sup.2], T1=30[second],
T2=3[second].
[0195] When the treatment was carried out at 50.degree. C. for 30
minutes, it was found on the basis of the measurement of the
thickness of the copper plating films, current flowing test,
microscopy and other tests that excellent copper plating films
having excellent uniformity in thickness were formed in 99.5%
spheres.
COMPARATIVE EXAMPLE 6-1
[0196] The same treatment as Example 6, except for the condition:
T2=0[second], was carried out. It was proved from the measurement
of the thickness of the copper plating films, the current flowing
test, microscopy and other tests that excellent copper plating
films were formed in some (40%) of the spheres, however, no
excellent copper plating film was formed in the other spheres.
COMPARATIVE EXAMPLE 6-2
[0197] The same treatment as Example 6, except that the vibrational
flow generator 16 was not actuated, was carried out. It was proved
from the measurement of the thickness of the copper plating films,
the current flowing test, microscopy and other tests that excellent
copper plating films were formed in some (50%) of the spheres,
however, no excellent copper plating film was formed in the other
spheres.
EXAMPLE 7
[0198] The apparatus described with reference to FIGS. 1 to 3 was
used. Here, a vibrating motor of 150 W.times.200V.times.3.phi. was
used as the vibrating motor 16d, a plating tank having a volume of
300 liters was used as the plating tank 12, and Power Master PMD1
(available from Chuo Seisakusho, Co., Ltd.) was used as the power
source circuit 34.
[0199] A silicon wafer having a size of 40 mm.times.40 mm and a
thickness of 1 mm which was subjected to a predetermined
pre-treatment by the conventional method was used as the plating
target article X, on the surface of which many blind via holes each
having an inner diameter of 20 .mu.m and a depth of 70 .mu.m were
formed.
[0200] The following through hole bath of copper sulfate plating
was used as the plating bath 14:
[0201] Copper sulfate: 75 g/L
[0202] Sulfuric acid: 190 g/L
[0203] Brightener: proper amount
[0204] Chlorine ion: 40 mL/L
[0205] In the plating tank 12, an aeration tube made of ceramics
having an outer diameter of 75 mm.phi., an inner diameter of 50
mm.phi., a length of 500 mmm, a pore size of 50 to 60 .mu.m and a
porosity of 33 to 38% was disposed to generate air bubbles in the
plating bath 14.
[0206] The vibrating motor 16d of the vibrational flow generator 16
was vibrated at 40 Hz to vibrate the vibrating vanes 16f at an
amplitude of 0.1 mm and a vibration frequency of 650 revolutions
per minute in the plating bath 14. Further, the vibrating motor 28
of 75 W.times.200V.times.3.phi. was vibrated at 25 Hz to vibrate
the plating target articles X at an amplitude of 0.15 mm and a
vibration frequency of 200 revolutions per minute in the plating
bath 14. The three-dimensional flow rate in the plating bath at
this time was measured as 200 mm/second by the three-dimensional
electromagnetic flowmeter ACM300-A.
[0207] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=1.5[A/wafer], I2=0.1[A/wafer], T1=0.08[second],
T2=0.02[second].
[0208] When the treatment was carried out for 2.5 hours, it was
found on the basis of the current flowing test, microscopy and
other tests that copper plating films having a uniform thickness of
about 7 .mu.m were formed in all the inner surfaces of the blind
via holes.
COMPARATIVE EXAMPLE 7
[0209] The same treatment as Example 7, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that the openings of the
blind via holes were sealed with the copper plating films.
EXAMPLE 8
[0210] The same treatment as Example 7, except that a high
frequency vibrating motor was used as the vibrating motor 16d, the
vibrating motor 16d was vibrated at 150 Hz to vibrate the vibrating
vanes 16f at an amplitude of 0.2 mm and a vibration frequency of
1200 revolutions per minute in the plating bath 14, and the
treatment time was 1.5 hours.
[0211] It was proved from the current flowing test, microscopy and
other tests that the copper plating films having a uniform
thickness of about 7 .mu.m were formed in all the inner surfaces of
the blind via holes.
EXAMPLE 9
[0212] An epoxy resin plate for wiring board was used as the
plating target article X, on the surface of which many blind via
holes each having an inner diameter of 15 .mu.m and a depth of 40
.mu.m were formed.
[0213] As the pre-treatment for the electroplating treatment,
degreasing water washing-etching-water washing-neutralizing-water
washing-catalyst-water washing-accelarator-water
washing-electroless copper plating were conducted to make the
plating target article X electically conductive. Furthermore, water
washing-activating-water washing strike plating were conducted. In
the electroless copper plating and strike plating, the vibrational
flow was generated in the plating treatment liquid by means of the
same vibrational flow generator as described with reference to
FIGS. 1 to 3.
[0214] The electroplating treatment was carried out in the same
manner as Example 7, except that the swinging motor 20 was actuated
to swing the plating target article X at a swinging width of 30 mm
and a swinging frequency of 20 times per minute in the plating bath
14. The three-dimensional flow rate in the plating bath was
measured as 200 mm/second by the three-dimensional electromagnetic
flowmeter ACM300-A.
[0215] The plating current of rectangular waveform was supplied by
the power source circuit 34 so that I1, I2, T1, T2 shown in FIG. 8
satisfied I1=4.5[A/dm.sup.2], I2=0.4[A/dm.sup.2], T1=0.08[second],
T2=0.015[second].
[0216] When the treatment was carried out for 1 hour, it was found
on the basis of the current flowing test, microscopy and other
tests that copper plating films were excellently formed and
embedded in all the blind via holes.
COMPARATIVE EXAMPLE 8
[0217] The same treatment as Example 9, except for the condition:
T2=0[second], was carried out. It was proved from the current
flowing test, microscopy and other tests that the openings of the
blind via holes were sealed with the copper plating films, however,
voids remained in the innermost of the blind via holes.
* * * * *