U.S. patent application number 10/778122 was filed with the patent office on 2004-12-30 for method and apparatus for managing plating interruptions.
Invention is credited to Choi, Young Cheol, Han, Sang-Hun, Lee, Do-Woo, Lee, Jun Eui, Um, Tea Seog.
Application Number | 20040262164 10/778122 |
Document ID | / |
Family ID | 33536245 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040262164 |
Kind Code |
A1 |
Han, Sang-Hun ; et
al. |
December 30, 2004 |
Method and apparatus for managing plating interruptions
Abstract
A plating method and apparatus including at least one plating
bath including a plating solution used for plating at least one
workpiece and a source providing a first current, wherein the first
current is supplied to the plating solution when plating the at
least one workpiece, and providing a second current, lower than the
first current, wherein the second current is supplied to the
plating solution during an interruption. The plating method and
apparatus may include at least one main bath, at least one main
anode, at least one auxiliary bath, at least one auxiliary anode,
and/or a conveying unit. A portion of the conveying unit or the at
least one workpiece may act as a cathode or anode. The plating
method and apparatus may continuously expose a workpiece to a
plating solution.
Inventors: |
Han, Sang-Hun; (Cheonan-si,
KR) ; Lee, Jun Eui; (Cheonan-si, KR) ; Lee,
Do-Woo; (Cheonan-si, KR) ; Choi, Young Cheol;
(Cheonan-si, KR) ; Um, Tea Seog; (Cheonan-si,
KR) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 8910
RESTON
VA
20195
US
|
Family ID: |
33536245 |
Appl. No.: |
10/778122 |
Filed: |
February 17, 2004 |
Current U.S.
Class: |
205/96 |
Current CPC
Class: |
C25D 5/08 20130101; C25D
17/02 20130101; C25D 5/18 20130101; C25D 17/28 20130101; C25D 17/00
20130101; C25D 17/10 20130101 |
Class at
Publication: |
205/096 |
International
Class: |
C25D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2003 |
KR |
2003-41445 |
Claims
What is claimed is:
1. A plating method comprising: immersing at least one workpiece in
a plating solution held in at east one plating bath; supplying a
plating current to at least one anode in the plating solution to
plate the at least one workpiece; decreasing the plating current
supplied to the at least one anode upon interruption of the
plating; and returning the plating current a previous amount after
the interruption has ended to resume plating.
2. The plating method of claim 1, wherein, the plating current is
decreased to 5% to 40% of an original value.
3. The plating method of claim 1, wherein the plating solution
includes tin and bismuth and a tin-bismuth layer is plated on the
at least one workpiece.
4. A plating apparatus comprising: a plurality of main plating
baths which are aligned and each holding a plating solution; a
plurality of anodes in the plating solution of the plurality of
main plating baths; a plurality of auxiliary plating baths
interconnected between the plurality of main plating baths for
allowing the plating solution to flow therethrough; a conveying
unit, which sequentially conveys workpieces to the plurality of
main plating baths and the plurality of auxiliary plating baths to
be plated; and a power source for selectively supplying a plating
current to the plurality of anodes which is reduced when the
plating is interrupted.
5. The plating apparatus of claim 4, further comprising a plurality
of auxiliary anodes connected to the power source and disposed in
the plurality of auxiliary plating baths.
6. The plating apparatus of claim 5, wherein the plurality of
auxiliary anodes are commonly connected to the plurality of anodes
which are connected to the power source.
7. The plating apparatus of claim 4, wherein each of the plurality
of auxiliary anodes extends into a corresponding one of the
plurality of auxiliary plating baths.
8. The plating apparatus of claim 4, further comprising a plurality
of sensors, each inserted into one of the plurality of auxiliary
plating baths for sensing the plating solution flowing into the
plurality of auxiliary plating baths.
9. The plating apparatus of claim 4, wherein the plating current is
decreased to 5% to 40% of an original value.
10. A plating method of using a plating apparatus, which includes a
plurality of main plating baths aligned for holding a plating
solution, a plurality of anodes in the plating solution of the
plurality of main plating baths, a plurality of auxiliary plating
baths interconnected between the plurality of main plating baths
for allowing the plating solution to flow therethrough, a conveying
unit acting as a cathode to the plurality of anodes for
sequentially conveying workpieces to the plurality of main plating
baths and the plurality of auxiliary plating baths, and a power
source for applying current to the plurality of anodes, the plating
method comprising: sequentially and continuously supplying the
workpieces to the plating apparatus, which includes using the
conveying unit, to pass the workpieces through the plurality of
main plating baths and the plurality of auxiliary plating baths;
supplying a plating current provided by the power source to the
plurality of anodes to plate the workpieces; reducing the plating
current supplied by the power source upon interruption of the
plating; and returning the plating current to a previous amount
after the interruption has ended to resume plating.
11. The plating method of claim 10, wherein the plating solution
includes tin and bismuth, and a tin-bismuth layer is plated on the
workpieces.
12. The plating method of claim 10, wherein, the plating current is
decreased to 5 to 40% of an original value.
13. The plating method of claim 10, wherein the plating apparatus
further includes a plurality of auxiliary anodes disposed inside
the plurality of auxiliary plating baths, and the plating current
supplied by the power source when an interruption occurs is applied
both to the plurality of anodes and the plurality of auxiliary
anodes.
14. The plating method of claim 13, wherein the plating apparatus
further includes a plurality of auxiliary anodes, each of the
plurality of auxiliary anodes extending into a corresponding one of
the plurality of auxiliary plating baths, and the plating current
supplied by the power source is applied both to the plurality of
anodes and the plurality of auxiliary anodes.
15. An apparatus comprising: at least one plating bath including a
plating solution used for plating at least one workpiece; and a
source providing a first current, wherein the first current is
supplied to the plating solution when plating the at least one
workpiece, and providing a second current, lower than the first
current, wherein the second current is supplied to the plating
solution during an interruption.
16. The apparatus of claim 15, wherein the source provides the
first current after the interruption has ended.
17. The apparatus of claim 15, wherein the plating solution
includes tin and bismuth and a tin-bismuth layer is plated on the
at least one workpiece.
18. The apparatus of claim 15, wherein the second current is 5% to
40% of the first current.
19. The apparatus of claim 15, wherein the second current is low
enough to not induce plating and high enough so as to not induce at
least one of substitution and precipitation of elements in the
plating solution.
20. A method comprising: plating at least one workpiece by passing
the at least one workpiece through at least one plating bath; and
changing a first current to a second current during an interruption
in the plating.
21. The method of claim 20, further comprising: increasing the
second current to the first current after the interruption has
ended.
22. The method of claim 20, wherein the plating further includes
submerging the at least one workpiece in the plating solution, and
exposing the first current to the workpiece in the plating
solution.
23. The method of claim 22, wherein the plating solution includes
tin and bismuth and the plating forms a tin-bismuth layer on the at
least one workpiece.
24. The method of claim 20, wherein the second current is 5% to 40%
of the first current.
25. The method of claim 20, wherein the second current is low
enough to not induce plating and high enough so as to not induce at
least one of substitution and precipitation of elements in the
plating solution.
26. An apparatus comprising: at least one main plating bath; and at
least one auxiliary plating bath, arranged such that a plating
solution may flow from the at least one main plating bath into the
at least one auxiliary plating bath, wherein at least one workpiece
plated by the apparatus is not exposed to the environment outside
of the plating bath solution.
27. A method comprising: providing at least one plating bath and at
least one auxiliary bath such that a plating solution may flow from
the at least one main plating bath into the at least one auxiliary
plating bath; and passing at least one workpiece through the at
least one main plating bath and the at least one auxiliary plating
bath such that the at least one workpiece is not exposed to the
environment outside of the plating solution.
28. An apparatus comprising: at least one main plating bath; at
least one auxiliary plating bath, arranged such that a plating
solution, with a current applied thereto, may flow from the at
least one main plating bath into the at least one auxiliary plating
bath; and a conveying unit for providing at least one workpiece to
the plating solution with the current applied thereto, at least a
portion of the conveying unit or the at least one workpiece acting
as one of a cathode and anode to conduct the current.
29. A method comprising: passing at least one workpiece though at
least one plating bath and at least one auxiliary bath arranged
such that a plating solution, with a current applied thereto, may
flow from the at least one main plating bath into the at least one
auxiliary plating bath; and conducting the current using at least a
portion of the conveying unit or the at least one workpiece as one
of a cathode and anode.
Description
BACKGROUND OF THE INVENTION
[0001] This application claims the priority of Korean Patent
Application No. 2003-41445, filed on Jun. 25, 2003, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
plating an integrated circuit device, and more particularly, to a
method and apparatus for plating an integrated circuit device, by
reducing an electrical plating current when an interruption in
plating occurs.
[0004] 2. Description of the Related Art
[0005] A process of plating a semiconductor lead with a layer of
metal (or other material) is carried out when fabricating an
integrated circuit device, such as a semiconductor device. The
plating process is usually based on an electroplating technology in
which tin is layered onto a lead. In Korean Patent Publication No.
2001-0015412 filed on Jul. 22, 2000, entitled "A Plating Apparatus
and Method for Preventing Substitution and Precipitation" a
conventional plating method employing electroplating technology is
described to plate workpieces with a metal alloy.
[0006] A plating process for a semiconductor device is performed
through a continuous plating procedure according to demands for
fabricating semiconductor devices in large quantities. While
semiconductor workpieces, which are the portion of the
semiconductor device that requires plating, are placed onto a
conveying unit, and are continuously conveyed, a layer of metal
including tin may be coated onto the lead of the semiconductor
workpieces. In a conventional example, a plating apparatus includes
a plurality of plating baths aligned for performing the plating
function. The plating process is performed by passing the
semiconductor workpieces through the plating baths, while they are
disposed on a conveying unit.
[0007] The plating apparatus may further include a plurality of
preprocessing baths, such as chemical deflashing, rinsing,
descaling, and/or activating baths, and/or rinsing baths
respectively interposed between the preprocessing baths which are
aligned next to the plating baths. Furthermore, the plating
apparatus may include rinsing baths, neutralizing baths, and/or a
drier disposed after the plating baths. All the solution baths and
plating baths may be aligned, and thus, allow the semiconductor
workpieces hung from a chain belt of the conveying unit to pass
therethrough, thereby performing a plating process.
[0008] When the plating process is performed by a continuous
plating procedure, undesirable situations may occur. For example,
when the plating process stops due to an error, for example,
generated in the plating apparatus, the semiconductor workpieces
may not be conveyed for a duration of time. During this time, some
semiconductor workpieces which are dipped in the plating baths may
be subjected to over-plating. To avoid over-plating, most plating
apparatuses which use electroplating technology are configured to
cut off a current supply to anodes of the plating baths when the
plating process has stopped, namely, when the semiconductor
workpieces do not move due to an interruption in the plating
process.
[0009] However, if the current supply is cut off, a semiconductor
workpiece may be poorly plated. For example, in the case of lead
free plating, a solution supplied to tin plating baths contains
bismuth (Bi). Bi has a strong metal substitution property such that
when current being supplied to the anode(s) is cut off, the bismuth
Bi will bond to the lead of the semiconductor workpieces and
accordingly, the lead being plated will become oxidized. In
addition, since the lead of the semiconductor workpieces interposed
between the plating baths is exposed to air, the lead of the
semiconductor workpieces may become oxidized due to air
exposure.
[0010] For example, during a conventional plating process, about 30
semiconductor workpieces are interposed in the plating baths at one
time. In the case of an interruption, all 30 semiconductor
workpieces may become oxidized or overplated and thus, must be
re-plated. During the re-plating process, portions of lead which
are undesirably plated or oxidized should be stripped and then
rinsed and plated again, thereby adversely affecting the entire
plating process.
SUMMARY OF THE INVENTION
[0011] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which can reduce the errors
associated with workpieces being poorly plated, underplated, and/or
overplated.
[0012] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which reduce undesirable results
that may occur from interruptions in the plating process.
[0013] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which can improve the effective
yield of a process of semiconductor fabrication.
[0014] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which plates at least one
workpiece by passing the at least one workpiece through at least
one plating bath and decreases an electrical current supplied to
the at least one workpiece during interruptions in the plating
process.
[0015] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which decrease the applied
current during an interruption such that the current is low enough
to not induce plating and high enough so as to not induce at least
one of substitution and precipitation of elements in the plating
solution.
[0016] Exemplary embodiments of the present invention provide a
method and apparatus for plating, which plates at least one
workpiece by passing the at least one workpiece through at least
one main plating bath and at least one auxiliary plating bath and
decreases an electrical current supplied to the at least one
workpiece during interruptions in the plating process.
[0017] Exemplary embodiments of the present invention provide an
apparatus for plating including at least one plating bath including
a plating solution used for plating at least one workpiece and a
source providing a first current, wherein the first current is
supplied to the plating solution when plating the at least one
workpiece, and providing a second current, lower than the first
current, wherein the second current is supplied to the plating
solution during an interruption.
[0018] Exemplary embodiments of the present invention provide a
method including plating at least one workpiece by passing the at
least one workpiece through at least one plating bath and changing
a first current to a second current during an interruption in the
plating.
[0019] Exemplary embodiments of the present invention provide an
apparatus including at least one main plating bath and at least one
auxiliary plating bath, arranged such that a plating solution may
flow from the at least one main plating bath into the at least one
auxiliary plating bath, wherein at least one workpiece plated by
the apparatus is not exposed to the environment outside of the
plating bath solution.
[0020] Exemplary embodiments of the present invention provide a
method including providing at least one plating bath and at least
one auxiliary bath such that a plating solution may flow from the
at least one main plating bath into the at least one auxiliary
plating bath and passing at least one workpiece through the at
least one main plating bath and the at least one auxiliary plating
bath such that the at least one workpiece is not exposed to the
environment outside of the plating solution.
[0021] Exemplary embodiments of the present invention provide an
apparatus including at least one main plating bath, at least one
auxiliary plating bath, arranged such that a plating solution, with
a current applied thereto, may flow from the at least one main
plating bath into the at least one auxiliary plating bath, and a
conveying unit for providing at least one workpiece to the plating
solution with the current applied thereto, at least a portion of
the conveying unit or the at least one workpiece acting as one of a
cathode and anode to conduct the current.
[0022] Exemplary embodiments of the present invention provide a
method including passing at least one workpiece though at least one
plating bath and at least one auxiliary bath arranged such that a
plating solution, with a current applied thereto, may flow from the
at least one main plating bath into the at least one auxiliary
plating bath and conducting the current using at least a portion of
the conveying unit or the at least one workpiece as one of a
cathode and anode.
[0023] Exemplary embodiments of the present invention supply a
current between 5% and 40% of the original electrical plating
current before the interruption.
[0024] Exemplary embodiments of the present invention utilize a
plating solution containing tin and bismuth, such that a
tin-bismuth layer is formed on the workpieces during the plating
process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other examples and exemplary embodiments of
the present invention will become more apparent by describing in
detail exemplary embodiments thereof with reference to the attached
drawings in which:
[0026] FIG. 1 is a flow chart illustrating a plating method
according to an exemplary embodiment of the present invention;
[0027] FIG. 2 is a schematic diagram of a plating apparatus
according to an exemplary embodiment of the present invention;
[0028] FIG. 3 is an exemplary schematic view of main plating baths
and auxiliary plating baths comprised in the plating apparatus of
FIG. 2;
[0029] FIG. 4 is an exemplary schematic view illustrating
electrodes installed in the main plating baths and the auxiliary
plating baths comprised in the plating apparatus of FIG. 3;
[0030] FIG. 5A is an exemplary schematic sectional view
illustrating a state in which current is supplied to the main
plating baths of FIG. 3;
[0031] FIG. 5B is an exemplary schematic sectional view
illustrating a state in which current is supplied to the auxiliary
plating baths of FIG. 3;
[0032] FIG. 6A is an exemplary perspective view of the auxiliary
plating bath of FIG. 3; and
[0033] FIG. 6B is an exemplary side view of the auxiliary plating
bath of FIG. 3.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0034] Exemplary embodiments of the present invention will now be
described more fully with reference to the accompanying drawings,
in which exemplary embodiments of the invention are shown.
[0035] According to an exemplary embodiment of the present
invention, a plurality of plating baths are aligned and workpieces
are conveyed by a chain belt 500 or other conveying unit. When a
plating apparatus stops or an interruption in plating occurs,
possibly due to an error in the plating apparatus, current supplied
from a power supply and through anodes in a plating solution held
in the plating baths is reduced. The reduction in current may be a
amount sufficient to avoid undesirable results that may occur from
the workpieces being overexposed during the plating process.
[0036] Moreover, in addition to the current reduction process, the
plating process may include auxiliary plating baths interposed
between the main plating baths to help keep the workpieces from
being oxidized, even when the plating process stops. The auxiliary
plating baths, which also contain the plating solution, help manage
the workpieces' exposure to the plating solution contained in both
the main and auxiliary plating baths. Further, the plating
apparatus employs auxiliary anodes in the auxiliary plating baths,
such that when the plating process stops, an amount of current to
avoid a metal substitution reaction is supplied through the
auxiliary anodes to the plating solution.
[0037] According to an exemplary embodiment of the present
invention, even though the plating apparatus or the conveying unit
may stop, thereby interrupting the plating process, causing poor
plating, such as metal substitution, precipitation, over-plating
and oxidation of the workpieces due to their exposure to metals,
that may be in the plating solution and air can be reduced. As a
result, the workpieces being plated can avoid poor plating and
over-plating by reducing the amount of current being provided to
the plating solution at the time the interruption occurs
[0038] FIG. 1 is a flow chart illustrating a plating method
according to an exemplary embodiment of the present invention.
FIGS. 2 through 6B are schematic diagrams illustrating a plating
apparatus according to an exemplary embodiment of the present
invention.
[0039] Referring to FIG. 1, when a plating process stops, for
example, due to an error, an electrical plating current supplied to
a plating solution held in the plating baths is decreased.
Workpieces, for example, leads of integrated circuit devices being
plated in the plating baths, may be able to avoid undesirable metal
substitution that may occur from the duration of exposure incurred
from the interruption in the plating process.
[0040] In an exemplary embodiment of the present invention, for
example, in the case of lead free tin-bismuth plating, when the
plating process stops due to an interruption in the plating
apparatus, current supplied to the workpieces immersed in the
plating baths may be cut off. If a plating current is continuously
supplied, the workpieces conveyed by a conveying unit, will be
continuously immersed in the plating solution. Consequently, since
the plating reaction is continuously performed on the workpieces, a
plating layer, composed of the metal contained in the plating
solution, might become thicker than required. To avoid such
over-plating, the plating current may be reduced when the plating
process stops.
[0041] An exemplary embodiment of the present invention provides
for decreasing the plating current supplied to the plating solution
in the plating baths when the plating process stops to avoid
substitution and/or precipitation from occurring. The substitution
and/or precipitation occur from prolonged exposure elements in the
plating solution, for example, bismuth.
[0042] In an exemplary embodiment of the present invention, during
an interruption in the plating the process, the plating current may
be reduced to a level sufficient to avoid plating, in addition to
substitution and/or precipitation. The level of the current should
be high enough to avoid substitution and/or precipitation but low
enough to not induce plating.
[0043] In an exemplary embodiment of the present invention, the
plating current is approximately between 75 A to 100 A during
normal operation, and the plating current used to avoid metal
substitution and precipitation is approximately between 5 A to 30
A. Thus the plating current needs to be decreased to a level
between 5% to 40% of the plating current during normal operation.
In an exemplary embodiment the plating current is decreased to
approximately 15 A when the plating current was originally, for
example approximately 75 A.
[0044] In an exemplary embodiment of the present invention a
plating procedure is performed by sequentially conveying workpieces
in a plating apparatus in which plating baths are aligned. Solution
baths are disposed at front and rear sides of the plating baths.
This example is be explained below in detail.
[0045] FIG. 2 is a schematic diagram of a plating apparatus
according to an exemplary embodiment of the present invention. FIG.
3 is a schematic diagram of plating baths and auxiliary plating
baths of the plating apparatus in FIG. 2.
[0046] Referring to FIG. 2, the plating apparatus includes a
plurality of plating baths 300 which are aligned, and a plurality
of solution baths 250 aligned before and after the plating baths
300. Lead frames composed of packaged workpieces, for example,
semiconductor workpieces, are sequentially and continuously
conveyed to the plating baths 300 and the solution baths 250 by a
conveying unit, such that the workpieces are attached to the
conveying unit, so as to be plated by being immersed in the plating
bath solution of the plating baths 300.
[0047] The workpieces may be attached to the conveying unit at a
load point 210 and then input into the plating apparatus. The
workpieces may be first chemically deflashed, rinsed, high-pressure
rinsed, and/or descaled. The workpieces may be rinsed again,
activated, by being dipped in a solution containing an activator,
and/or pre-dipped in a pre-processing bath 290. The workpieces may
then be conveyed to the plating baths 300 to be plated. The
workpieces may then continue on to the rest of the solution baths
to be neutralized, hot rinsed, air rinsed, and/or dried. The
workpieces may be removed from the plating apparatus at an unload
point 230. It is appreciated that a plating process is performed
when the workpieces pass through the plating baths 300.
[0048] Referring to FIG. 3, the plating baths 300 include a
plurality of main plating baths, for example, four (although there
may be another number) main plating baths, 310, 320, 330, and 340
and a plurality of auxiliary plating baths, for example, three
(although there may be another number, but generally one less than
the number of main plating baths) auxiliary plating baths 400,410,
and 420. The auxiliary plating baths 400, 410, and 420 pass through
connection parts 350 which interconnect the main plating baths 310,
320,330, and 340. Thus, the auxiliary plating baths 400, 410, and
420 allow a plating solution to flow in spaces between the main
plating baths 310, 320, 330, and 340. That is to say, the auxiliary
plating baths 400, 410, and 420 are interconnected between the main
plating baths 310, 320, 330, and 340 in order to allow the plating
solution to flow through as well, so that the workpieces conveyed
by the chain belt 500, which are dipped in the plating solution,
are not separated from the plating solution and are therefore not
exposed to air, in the spaces between the main plating baths 310,
320, 330, 340. Accordingly, the plating solution provided to the
main plating baths 310, 320, 330, and 340 can also flow into the
auxiliary plating baths 400, 410, and 420.
[0049] Referring to FIG. 1, in step 110, the main plating baths
310, 320,330, and 340 and the auxiliary plating baths 400, 410, and
420 are aligned. In step 120, the workpieces are continuously
conveyed to the plating baths to be plated. A plating current is
supplied to the workpieces and anodes 700 in the main plating baths
310, 320, 330, and 340 through a power source 600 to plate the
workpieces. In an exemplary embodiment of the present invention,
the plating current may range from 75 A to 100 A and is supplied by
the power source 600 which may comprise a rectifier to induce the
plating reaction.
[0050] In step 130, the plating current is applied to the anodes
700 which may be flat panels, and which are disposed in each of the
main plating baths 310, 320, 330, and 340. The workpieces, attached
to the conveying unit are electrically connected thereto, and thus
contact the power source 600. As a result, either the workpieces or
the conveying unit may act as a cathode.
[0051] Metal contained in the plating solution is bonded to the
workpieces during the plating process, with the electrical current
produced by the plating current. In an exemplary embodiment of the
present invention, lead-free tin-plating is used. The lead-free
tin-plating may be accomplished by plating the workpieces in a
plating solution containing tin and bismuth. The tin and bismuth
may be plated on the workpieces at any desired atomic ratio by the
plating current.
[0052] The plating process may stop or an interruption may occur
for various reasons during the plating process. Upon interruption,
the chain belt does not operate, such that the workpieces remain
immersed in the plating solution for the duration of the
interruption.
[0053] If the workpieces continue to be immersed in the plating
solution while the normal amount of current is supplied,
over-plating may occur on the workpieces, which is undesirable. In
step 130 of FIG. 1, when the plating process stops or an
interruption occurs, the power source 600 will be decreased to
decrease the plating current supplied to the workpieces through the
anodes 700.
[0054] In an exemplary embodiment of the present invention, the
plating current automatically decreases in response to a program
which is set by an controller (not shown), when the plating process
stops or is interrupted. The program would modify the plating
process by adjusting the amount of current being supplied to the
workpieces in the event of an interruption. The resulting plating
current will be reduced, by the program to a rate which is
approximately 5% to 40% of the original plating current used during
the normal operation.
[0055] The plating current is decreased to avoid over-plating the
workpieces, which remain in the plating solution. Such over-plating
may result in the workpieces acquiring a plating layer which is
excessively thick. Since the plating current is a factor in
determining the thickness of the plating layer through the plating
reaction, the plating reaction can be substantially reduced by
reducing the plating current.
[0056] If metals, for example, bismuth, which have a strong metal
substitution property, are present in the plating solution, as in
the case of the lead free tin-plating, when no plating current is
applied, substitution and/or precipitation can occur on the
workpieces.
[0057] However, if instead of no current, a lower ampere rating
plating current is supplied through the anodes 700 than in the
normal operation, then the bismuth may be substantially prevented
from being substituted, precipitated and/or bonded onto the
workpieces.
[0058] As shown in FIG. 3, the anodes 700 in the main plating baths
310, 320, 330, and 340 are not extended into the auxiliary plating
baths 400, 410, and 420. Thus, when the plating process stops, the
workpieces positioned in the auxiliary plating baths 400, 410, and
420, that is, in the connection parts 350 between the main plating
baths 310, 320, 330, and 340 may suffer from an unbalanced
composition ratio of tin-bismuth.
[0059] Referring to FIGS. 4, 5A and 5B, auxiliary anodes 750, which
may be flat panels, are located within the auxiliary plating baths
400, 410, and 420. FIG. 4 is an exemplary schematic plan view
illustrating electrodes in the main plating baths 310, 320, 330,
and 340 and the auxiliary plating baths 400. FIG. 5A is an
exemplary schematic sectional view illustrating a state in which
current is applied to the main plating baths 310, 320, 330, and
340. FIG. 5B is a schematic sectional view illustrating a state in
which current is applied to the auxiliary plating baths 400, 410,
and 420.
[0060] Referring to FIG. 4, the auxiliary plating bath 400 passes
through the connection part 350 to interconnect the main plating
baths 310 320. Referring to FIG. 3, since the area of the first
main plating bath 310 is divided by a plating solution partition
311, the plating solution in the first main plating bath 310 is
held within the plating solution partition 311. The plating
solution partition 311 allows a drain (not shown) for discharging
the plating solution to be disposed between the plating solution
partition 311 and the wall of the main plating bath 310.
[0061] The auxiliary plating bath 400 extends to the area of the
main plating bath 310, which holds the plating solution such that
the plating solution can flow into the auxiliary plating bath 400.
Therefore, as shown in FIGS. 5A and 5B, when the plating process
stops and the chain belt 500 does not move, the workpieces 550,
which are not immersed in the main plating bath 310 or 320, are
positioned and halted inside the auxiliary plating baths 400, 410,
and 420 and thus, continue to be immersed in the plating solution
390 in the auxiliary plating baths 400, 410, and 420.
[0062] The auxiliary anodes 750 are located inside the auxiliary
baths 400, 410, and 420. The auxiliary anodes 750 may have a flat
panel shape and may be the same length as the auxiliary plating
baths 400, 410, and 420. The auxiliary anodes 750 may be used to
provide a continuous movement of the workpieces being passed
through the plating solution, and to avoid metals which have strong
metal substitution and/or precipitation properties, such as BI,
from bonding to the workpieces 550, which are immersed in the
auxiliary plating baths 400, 410, and 420. Thus, the auxiliary
anodes 750 can be connected to the power source 600 together with
the main anodes 700 disposed inside the first main plating bath
310. Accordingly, when the plating process stops, a plating current
which is less than the plating current supplied during normal
operation is provided to the auxiliary anodes 750 as well as the
main anodes 700. In another exemplary embodiment, the main anodes
700 may be extended inside the auxiliary plating baths 400, 410,
and 420 to perform the same function as the auxiliary anodes 750,
either to replace or augment the function of the auxiliary anodes
750.
[0063] Since the auxiliary anodes 750 are disposed in the auxiliary
plating baths 400, 410, and 420, protection of the workpieces from
substitution and/or precipitation can be continuously provided,
even during an interruption in the plating process.
[0064] During the operation of plating the workpieces, as shown in
FIG. 5B, as the plating solution 390 is also contained in the
auxiliary plating baths 400, 410, and 420, the workpieces 550 can
be continuously conveyed while being immersed in the plating
solution 390 during the series of plating processes described with
reference to FIG. 2. Therefore, in an exemplary embodiment, even
though the plating process stops, the workpieces 550 need not be
exposed to air, thereby reducing or avoiding oxidation due to
exposure to air.
[0065] Furthermore, since the auxiliary plating baths 400, 410, and
420 allow the plating solution 390 to pass through the separate
plating baths 310, 320, 330, and 340, the auxiliary plating baths
400, 410, and 420 can achieve the same plating effect as when a
regular plating bath, for example, 310 is used. That is to say,
plating uniformity may be improved by virtue of the introduction of
the separate main plating baths 310, 320, 330, and 340 an/or the
auxiliary plating baths 400, 410, and 420.
[0066] If the auxiliary plating baths 400, 410, and 420 are not
used, no plating is actually carried out between the main plating
baths 310, 320, 330, and 340. By introducing the auxiliary plating
baths 400, workpieces 550 can be continuously plated while being
conveyed and problems caused as a result of the main plating baths
310, 320, 330, and 340 being separated in the plating apparatus can
be solved.
[0067] In fact, since each of the main plating baths 310, 320, 330,
and 340 has a length of about 1.5 meters, the entire plating bath
300 is longer than 6 meters. Practically, it is not sound to
construct one single plating bath at this length. The plating
apparatus according to an exemplary embodiment of the present
invention has substantially the same effect as a single plating
bath by employing the auxiliary plating baths 400, 410, and
420.
[0068] The auxiliary plating baths 400, 410, and 420 are
constructed as shown in FIGS. 6A and 6B. FIGS. 6A and 6B are
respectively a perspective view and a side view of one of the
auxiliary plating baths 400.
[0069] Referring to FIGS. 6A and 6B, the auxiliary plating bath 400
may be constructed to have a bottom plate 420 and two walls 410
which may have a flat panel shape and are perpendicularly attached
to bottom plate 420 supported by legs 430. The walls 410 may be
supported on the bottom plate 420 by supports 460. A hole 440 may
be formed in one of the walls 410, and a sensor 470 may be inserted
into the hole 440 to detect whether or not the plating solution
exists.
[0070] The walls 410 of the auxiliary plating bath 400 may be long
enough for the auxiliary plating bath 400 to reach at least the
plating solution held in the main plating baths 310 and 320 when
the auxiliary plating bath 400 is interposed between the main
plating baths 310 and 320 as shown in FIG. 4. In an exemplary
embodiment of the present invention, the walls 410 of the auxiliary
plating bath 400 are sufficiently long to allow the auxiliary
plating bath 400 to pass beyond and/or contact the plating solution
partition 311.
[0071] Referring to FIG. 1, after the interruption in the plating
process is resolved, the plating current may be increased back up
to a level sufficient for plating according to normal operation,
and is supplied to the main anodes 700 or the auxiliary anodes 750
to resume the plating process. Poor plating such as over-plating,
metal substitution and/or precipitation can be avoided during
interruption periods. Less reworking of the workpieces that have
been subjected to poor plating is, therefore, required.
[0072] As described above, even though a plating process stops or
an interruption occurs, the exemplary embodiments of the present
invention can effectively maintain workpieces, for example, lead
frames, so they are properly plated. Accordingly, reworking is
reduced, leading to improved productivity and rate of operation of
the plating apparatus.
[0073] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *