U.S. patent application number 09/771399 was filed with the patent office on 2001-12-13 for manufacturing method and plating apparatus for film carrier tape.
Invention is credited to Kobayashi, Toshihiko.
Application Number | 20010051211 09/771399 |
Document ID | / |
Family ID | 18545884 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051211 |
Kind Code |
A1 |
Kobayashi, Toshihiko |
December 13, 2001 |
Manufacturing method and plating apparatus for film carrier
tape
Abstract
Embodiments include a manufacturing method and a plating
apparatus for film carrier tapes, in which the plating process does
not cause hollowed-out portions in a copper foil at end sections of
the solder resist or of the adhesive. A plating apparatus 44 is
formed from a first plating bath 46, a second plating bath 48 and a
transfer path 54. Plating liquid 60 in the first plating bath 46 is
set to a liquid temperature level lower than that of the plating
liquid 60 in the second plating bath 48. The transfer path 54 is
formed from sprockets that can transfer the film carrier tape 20.
In the plating apparatus 44 thus constructed, the deposition amount
is small in the first plating bath 46, and therefore a plated layer
may be uniformly formed on exposed portions. After a plated layer
is formed, the film carrier tape 20 is brought in the second
plating bath 48 to form a new plated layer over the plated layer
that has been formed. As a result, a uniform plated layer having a
sufficient thickness can be formed on the exposed portions.
Inventors: |
Kobayashi, Toshihiko;
(Chino-shi, JP) |
Correspondence
Address: |
KONRAD RAYNES & VICTOR, LLP
315 SOUTH BEVERLY DRIVE
SUITE 210
BEVERLY HILLS
CA
90212
US
|
Family ID: |
18545884 |
Appl. No.: |
09/771399 |
Filed: |
January 27, 2001 |
Current U.S.
Class: |
205/85 ; 118/419;
204/202; 204/206; 205/87; 257/E23.054; 427/97.1; 427/99.5 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/49582 20130101; C23C 18/54 20130101; H01L 2924/0002
20130101; C23C 18/1651 20130101; C23C 18/31 20130101; C23C 18/168
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
427/98 ;
205/87 |
International
Class: |
C25D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2000 |
JP |
2000-019125 |
Claims
What is claimed:
1. A method for manufacturing a film carrier tape in which a wiring
pattern is formed on a flexible substrate, the method comprising
the steps of: dipping the film carrier tape in a first temperature
plating liquid to form a plated layer in an exposed portion of the
wiring pattern by a substitution reaction; and then dipping the
film carrier tape in a second temperature plating liquid having a
higher temperature than the first temperature plating liquid, to
increase the thickness of the plated layer.
2. A method for manufacturing a film carrier tape in which a wiring
pattern is formed on an elongated flexible substrate, the method
comprising the steps of: transferring the film carrier tape in a
longitudinal direction thereof; dipping the film carrier tape in a
first temperature plating liquid to form a plated layer in an
exposed portion of the wiring pattern by a substitution reaction;
and then dipping the film carrier tape in a second temperature
plating liquid to increase the thickness of the plated layer,
wherein the second temperature plating liquid has a higher
temperature than the first temperature plating liquid.
3. A method for manufacturing a film carrier tape according to
claim 1, wherein the exposed portion defines at least one of an
input terminal and an inner lead.
4. A method for manufacturing a film carrier tape according to
claim 2, wherein the exposed portion defines at least one of an
input terminal and an inner lead.
5. A method for manufacturing a film carrier tape according to
claim 1, wherein the plated layer comprises tin.
6. A method for manufacturing a film carrier tape according to
claim 2, wherein the plated layer comprises tin.
7. A method for manufacturing a film carrier tape according to
claim 3, wherein the plated layer comprises tin.
8. A method for manufacturing a film carrier tape according to
claim 4, wherein the plated layer comprises tin.
9. A method for manufacturing a film carrier tape according to
claim 1, wherein the first temperature plating liquid is set at a
temperature of 10-40.degree. C. and the second temperature plating
liquid is set at a temperature of 65-70.degree. C.
10. A method for manufacturing a film carrier tape according to
claim 2, wherein the first temperature plating liquid is set at a
temperature of 10-40.degree. C. and the second temperature plating
liquid is set at a temperature of 65-70.degree. C.
11. A method for manufacturing a film carrier tape according to
claim 5, wherein the first temperature plating liquid is set at a
temperature of 10-40.degree. C. and the second temperature plating
liquid is set at a temperature of 65-70.degree. C.
12. A method for manufacturing a film carrier tape according to
claim 6, wherein the first temperature plating liquid is set at a
temperature of 10-40.degree. C. and the second temperature plating
liquid is set at a temperature of 65-70.degree. C.
13. A plating apparatus comprising a first plating bath containing
a plating liquid at a first temperature level, a second plating
bath containing a plating liquid at a second temperature level that
is higher than the first temperature level, and a transfer path for
a film carrier tape in which a wiring pattern is formed on an
elongated flexible substrate, wherein the transfer path passes
through the first plating bath and the second plating bath.
14. The method of claim 1, wherein the first temperature plating
liquid has the same composition as the second temperature plating
liquid.
15. The method of claim 2, wherein the first temperature plating
liquid has the same composition as the second temperature plating
liquid.
16. The apparatus of claim 13, wherein the first plating bath has
the same composition as the second plating bath.
17. A plating apparatus comprising: means for delivering a film
carrier tape to a first plating bath at a first temperature along a
transfer path; and means for delivering the film carrier tape along
the transfer path to a second plating bath at a second temperature
that is higher than the first temperature; wherein the first
plating bath and the second plating bath have the same
composition.
18. The plating apparatus of claim 17, wherein the first plating
bath comprises tin.
19. The plating apparatus of claim 17, wherein the first plating
bath is at a temperature in the range of about 10.degree. C. to
about 40.degree. C. and the second plating bath is at a temperature
in the range of about 65.degree. C. to about 70.degree. C.
Description
[0001] Japanese Patent Application No. 2000-19125(P), filed Jan.
27, 2000, is hereby incorporated by reference in its entirety.
[0002] 1. Technical Field
[0003] The present invention relates to high-density mounting, and
more particularly, preferred embodiments relate to a manufacturing
method and a plating apparatus for a film carrier tape that uses an
elongated flexible substrate.
[0004] 2. Related Art
[0005] Mounting a semiconductor chip on a film carrier is
conventionally known as one of the high-density mounting methods.
After a semiconductor chip is mounted on a film carrier, an area
surrounding the semiconductor chip in the film carrier is punched
out to form a TAB (tape automated bonding) package, which is widely
used for, for example, drivers for driving liquid crystal panels
and the like.
[0006] FIG. 4 shows a configuration of a conventional film carrier
tape. As shown in the figure, a film carrier tape 1 is formed from
an elongated flexible substrate 2. Holes and the like are punched
out in the elongated substrate 2, and then wiring patterns are
formed thereon. The elongated substrate 2 is formed from a
polyimide material and has sprocket holes on both sides thereof
(formed in areas a) continuously formed along the longitudinal
direction. Sprockets are provided in the transfer path and engage
the sprocket holes to enable transfer of the elongated substrate 2
in a transfer direction (in the direction of an arrow in the
figure).
[0007] Film carriers 3 are punched out from the elongated substrate
2. For this purpose, the elongated substrate 2 defines punch-out
regions 4 each corresponding to the shape of the film carrier 3.
The punch-out regions 4 are provided in plurality at equal
intervals along the transfer path of the elongated substrate 2. A
device hole 5 having a sufficient size to contain a semiconductor
chip and an input terminal hole 6 adjacent to the device hole 5 are
punched out within the punch-out region 4.
[0008] Wiring patterns 7 (a forming region therefor is shown in the
figure) composed of a copper material are formed between the device
hole 5 and the input terminal hole 6 in the number corresponding to
the number of terminals of the semiconductor chip. One end of the
wiring patterns protrude from one edge of the device hole 5 as
inner leads 9 (a forming region therefor is shown in the figure) to
establish conduction with the terminals of the semiconductor chip.
On the opposite side of the inner leads 9 in the wiring patterns 7,
the wiring patterns 7 are led out across the input terminal hole 6.
The portions of the wiring patterns 7 that extend across the input
terminal hole 6 define input terminals 8 that are to be connected
to terminals formed on an external substrate.
[0009] Wiring patterns 7 are led out from the device hole 5 on the
opposite side of the area where the input terminal hole 6 is formed
in the number corresponding to the number of terminals of the
semiconductor chip. Output terminals 10 are formed on tips of the
wiring patterns 7 for contact with another external substrate.
[0010] The film carrier tape 1 is made in the following manner.
First, holes such as the device holes 5 and the input terminal
holes 6 are punched out in the elongated substrate 2. Then a copper
foil is adhered to the elongated substrate 2 with an adhesive, and
the wiring patterns 7 and the like are formed by exposure and
etching. After the wiring patterns 7, the input terminals 8 and the
inner leads 9 are formed, solder resist for protecting the wiring
patterns 7 is coated on the wiring patterns 7. Then the film
carrier tape 1 is placed in a tin plating bath to plate surfaces of
the input terminals 8 and the inner leads 9.
[0011] FIG. 6 shows a structure of a plating apparatus for plating
tin on the film carrier tape 1. A plating apparatus 11 shown in the
figure has a plating bath 12. A plurality of follower-side
sprockets 13 are provided on the inside of the plating bath 12, and
driver-side sprockets 14 are provided before and the after the
plating bath 12. With the plating bath 12 having the structure
described above, the driver-side sprockets 14 are driven to
successively dip the film carrier tape 1 in plating liquid 15 in
the plating bath 12, such that surfaces of the input terminals 8
and the inner leads 9 are plated. For the plating process,
electroless plating (i.e., chemical plating) is conducted in order
to obtain a uniform film thickness.
[0012] After the plating process is completed and the film carrier
tape 1 is completed, semiconductor chips are positioned within the
respective device holes 5, and gold bumps (i.e., connection
terminals) provided on the semiconductor chips and the inner leads
9 are subject to a thermocompression bonding such that they are
bonded together through a eutectic reaction.
Summary
[0013] One embodiment relates to a method for manufacturing a film
carrier tape in which a wiring pattern is formed on a flexible
substrate. The method includes dipping the film carrier tape in a
first temperature plating liquid to form a plated layer in an
exposed portion of the wiring pattern by a substitution reaction.
Then the film carrier tape is dipped in a second temperature
plating liquid having a higher temperature than the first
temperature plating liquid, to increase the thickness of the plated
layer.
[0014] Another embodiment relates to a method for manufacturing a
film carrier tape in which a wiring pattern is formed on an
elongated flexible substrate. The method includes transferring the
film carrier tape in a longitudinal direction thereof and dipping
the film carrier tape in a first temperature plating liquid to form
a plated layer in an exposed portion of the wiring pattern by a
substitution reaction. Then, the method includes dipping the film
carrier tape in a second temperature plating liquid to increase the
thickness of the plated layer, wherein the second temperature
plating liquid has a higher temperature than the first temperature
plating liquid. In one aspect of certain embodiments, the plated
layer comprises tin.
[0015] Another embodiment relates to a plating apparatus including
a first plating bath containing a plating liquid at a first
temperature level and a second plating bath containing a plating
liquid at a second temperature level that is higher than the first
temperature level. The plating apparatus also includes a transfer
path for a film carrier tape in which a wiring pattern is formed on
an elongated flexible substrate wherein the transfer path passes
through the first plating bath and the second plating bath.
[0016] Another embodiment relates to a plating apparatus comprising
means for delivering a film carrier tape to a first plating bath at
a first temperature along a transfer path, and means for delivering
the film carrier tape along the transfer path to a second plating
bath at a second temperature that is higher than the first
temperature, wherein the first plating bath and the second plating
bath have the same composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Embodiments of the invention are described with reference to
the accompanying drawings which, for illustrative purposes, are
schematic and not necessarily drawn to scale.
[0018] FIG. 1 is an explanatory view for describing steps of
manufacturing a film carrier tape using a plating apparatus in
accordance with one embodiment of the present invention.
[0019] FIG. 2 is an explanatory view of one form of a film carrier
tape that is processed in the plating apparatus in accordance with
an embodiment of the present invention.
[0020] FIG. 3 is an expanded view of a main portion taken along
lines B-B of FIG. 2.
[0021] FIG. 4 is an expanded view of one form of a conventional
film carrier tape.
[0022] FIG. 5 is an expanded view of a main portion taken along
lines B-B of FIG. 4.
[0023] FIG. 6 is an explanatory view for describing a conventional
structure of a plating apparatus for plating a film carrier tape
with tin.
DETAILED DESCRIPTION
[0024] In the plating process described above with reference to
FIGS. 4-6, the deposition amount per unit time is relatively small.
The plating liquid is normally heated to a temperature that does
not decompose the plating liquid. However, troubles may occur in
the wiring patterns composed of the copper foil when the film
carrier tape is subject to a plating process with the plating
liquid temperature being raised, although the substitution reaction
is improved and the deposition rate is increased. (For example,
when the film carrier tape is dipped in the plating liquid at
temperatures of 65-70.degree. C. for 3-4 minutes, a plating
thickness of about 0.5-0.8 .mu.m is obtained.)
[0025] FIG. 5 shows an enlarged cross-sectional view of a main area
taken along lines A-A of FIG. 4, including wiring pattern 7
attached by adhesive 17 to elongated substrate 2. As shown in the
figure, hollowed-out portions 18 are formed in the wiring patterns
7 at an end section of the solder resist 16 that is formed on the
wiring patterns 7 or at a base section of the input terminals 8
where the substitution reaction is accelerated several times more
than other parts. (It is noted that, although a plated layer 19 is
also formed at the hollowed-out portions 18 by the substitution
reaction, the plated layer 19 does not cohere to but is separated
from the hollowed-out portions 18.)
[0026] When the hollowed-out portions 18 are created in the wiring
patterns 7, the resistance value of the wiring patterns 7 may
increase. Also, when an external force is applied to the wiring
patterns 7, the hollowed-out portions 18 may act as cracks and
break the wiring patterns 7.
[0027] It is empirically known that the magnitude of the
hollowed-out portions 18 is reduced when impurities that may be
present at an end section of the solder resist 16 formed on the
wiring patterns 7 or at a base section of the input terminals 8 are
removed. However, even when a washing step is provided before the
plating step, the problem described above is not completely removed
because it is difficult to completely remove the impurities, and
the hollowed-out portions 18 still remain. Moreover, a new problem
occurs in that the washing step increases the number of
manufacturing steps.
[0028] It is an object of preferred embodiments of the present
invention to provide a manufacturing method and a plating apparatus
for film carrier tapes, in which the plating process does not cause
hollowed-out portions in a copper foil at end sections of the
solder resist or of the adhesive, and the troubles such as an
increased resistance value, breakage of wires and the like are
inhibited.
[0029] Certain embodiments of the present invention have been made
based on discoveries that dipping a film carrier tape in plating
liquids of different temperatures can change deposition rates,
prevent the generation of hollowed-out portions in the copper foil,
and form a plated layer having a sufficient film thickness.
[0030] For example, a method for manufacturing a film carrier tape
in accordance with one embodiment pertains to a method for
manufacturing a film carrier tape in which a wiring pattern is
formed on a flexible substrate. The method is characterized in that
the film carrier tape is dipped in a lower temperature plating
liquid to form a plated layer in an exposed portion of the wiring
pattern by a substitution reaction, and then the film carrier tape
is dipped in a higher temperature plating liquid to increase the
thickness of the plated layer. According to the method for
manufacturing a film carrier tape set forth in claim 1, the film
carrier tape is first dipped in a plating liquid at a lower
temperature. As exposed portions of the wiring pattern contact the
plating liquid, the wiring patterns are dissolved into the plating
liquid, and a eutectic reaction occurs with the plating liquid to
thereby form a plated layer on surfaces of the wiring patterns. In
this step, the deposition rate per unit time in the plating liquid
is small and the substitution reaction is minimal because the
plating liquid is set to a lower temperature. As a result, the
substitution reaction is suppressed in corner sections of the
exposed portions of the wiring patterns, in other words, in areas
of the wiring patterns that are located at end sections of a
coating member that covers the wiring patterns. Accordingly, the
substitution reaction takes place at a rate similar to those in the
other areas of the wiring patterns, and a plated layer preferably
having a uniform thickness is formed on the exposed portions of the
wiring patterns.
[0031] After the plated layer having a uniform thickness is formed
on the exposed portions of the wiring patterns, the film carrier
tape is dipped in a plating liquid set at a higher temperature. In
the plating liquid at the higher temperature, the deposition amount
per unit time is greater. Accordingly, the plating material may
newly deposit in the thickness direction of the plated layer
through pinholes in the plated layer formed by the plating liquid
set at the lower temperature level, and the thickness of the plated
layer increases. When the plated layer reaches a predetermined
thickness (which is normally controlled by the dipping time), the
film carrier tape is pulled out from the plating liquid set at the
higher temperature level. In this manner, by dipping the film
carrier tape in the plating liquids that are set at different
temperatures, a plated layer preferably having a uniform thickness
is formed on the exposed portions of the wiring patterns. As a
result, the formation of hollowed-out portions is inhibited in
corner sections of the exposed portions of the wiring patterns, and
an increase in the resistance value of the wiring patterns and
breakage of the wiring patterns can be prevented.
[0032] Also, a method for manufacturing a film carrier tape in
accordance with another embodiment pertains to a method for
manufacturing a film carrier tape in which a wiring pattern is
formed on an elongated flexible substrate. The method is
characterized in that the film carrier tape is transferred in a
longitudinal direction thereof, the film carrier tape is dipped in
a lower temperature plating liquid to form a plated layer in an
exposed portion of the wiring pattern by a substitution reaction,
and then the film carrier tape is dipped in a higher temperature
plating liquid to increase the thickness of the plated layer. This
method for manufacturing a film carrier tape provides an effect in
that the film carrier tape can be continuously brought in the lower
temperature plating liquid and the higher temperature plating
liquid, in addition to the effects described above in connection
with the embodiment described in the immediately preceding
paragraph. Accordingly, an effective plating process can be
performed for wiring patterns that are continuously formed along
the elongated substrate.
[0033] In another aspect of certain embodiments, the exposed
portion of a film tape defines an input terminal or an inner lead.
Input terminals protruding from an edge of an input terminal hole
or inner leads protruding from an edge of a device hole for
containing a semiconductor chip can be plated to provide erosion
protections on the input terminals or the inner leads.
[0034] In another aspect of certain embodiments, the plated layer
is composed of tin. The tin and gold may undergo a eutectic
reaction to achieve a sufficient bonding strength. Accordingly, the
inner leads achieve a sufficient bonding strength with portions of
a semiconductor chip, such as, for example, connection terminals
thereof that are generally plated with gold, and the bonding
reliability is improved. Also, it goes without saying that the tin
plating can resist a variety of organic acids.
[0035] In another aspect of certain embodiments, the lower
temperature plating liquid is set at a temperature of about
10-40.degree. C. and the higher temperature plating liquid is set
at a temperature of about 65-70.degree. C. A plated layer composed
of fine deposition particles is formed on an exposed surface in the
lower temperature plating liquid. Furthermore, in the higher
temperature plating liquid, particles having large grain sizes may
be deposited above the plated layer formed in the lower temperature
plating liquid, and the plated layer can be formed to a
predetermined thickness in a short time.
[0036] Another embodiment relates to a plating apparatus comprising
a first plating bath containing a plating liquid with temperatures
thereof being set at a lower level, a second plating bath
containing a plating liquid with temperatures thereof being set at
a higher level, and a transfer path for a film carrier tape in
which a wiring pattern is continuously formed on an elongated
flexible substrate wherein the transfer path is provided to pass
the first plating bath and the second plating bath. As the film
carrier tape is transferred along the transfer path, the film
carrier tape is first brought in the first plating bath. Since the
plating liquid in the first plating bath is set at a lower
temperature, the deposition amount is restricted, and a plated
layer having a uniform thickness can be formed on exposed portions
of the wiring pattern that is formed on the film carrier. After the
plated layer is formed on the exposed portions of the wiring
pattern, the film carrier tape is brought in the second plating
bath. The plating liquid in the second plating bath is set to a
higher temperature than that of the plating liquid in the first
plating bath, such that a new plated layer can be formed in a short
time in an upper layer of the plated layer that is formed on the
exposed portions of the wiring pattern. When the plated layer is
formed to a predetermined film thickness, the film carrier tape is
pulled out from the second plating bath, and transferred to a
succeeding stage. In this manner, the first and second plating
baths are provided in the transfer path for film carriers, such
that a plated layer can be formed on exposed portions of wiring
patterns by simply transferring the film carriers.
[0037] A manufacturing method and a plating apparatus for film
carrier tapes in accordance with preferred embodiments of the
present invention are described below in detail with reference to
the accompanying drawings.
[0038] FIG. 2 shows one configuration of a film carrier tape that
is brought in a plating apparatus. As shown in the figure, a film
carrier tape 20 is formed from an elongated flexible substrate 22.
Device holes and outer lead holes are punched out in the elongated
substrate 22, and then wiring patterns are provided around these
holes.
[0039] The elongated substrate 22 is made of polyimide in the form
of a film, and has a plurality of sprocket holes on both sides
thereof, (formed in areas a in the) continuously formed at equal
intervals along a longitudinal direction of the elongated substrate
22. Sprockets are provided in the transfer path and engage the
sprocket holes to enable transfer of the elongated substrate 22 in
a transfer direction (in the direction of an arrow in the
figure).
[0040] The elongated substrate 22 defines a plurality of punch-out
regions 26 for film carriers 24 formed at equal intervals along the
longitudinal direction. Each of the punch-out regions 26
corresponds to a punch-out shape of each of the film carriers
24.
[0041] A device hole 28 having a sufficient size to contain a
semiconductor chip and an input terminal hole 30 adjacent to the
device hole 28 are provided within each of the punch-out regions
26. Wiring patterns 32 (a region where they are formed is shown in
the figure) are formed between the device hole 28 and the input
terminal hole 30. One ends of the wiring patterns 32 protrude from
one edge of the device hole 28 as input inner leads 34 (a region
where they are formed is shown in the figure) to establish
connection with connection terminals to be formed on a surface of a
semiconductor chip. On the opposite side of the input inner leads
34 in the wiring patterns 32, the wiring patterns 32 are led out
across the input terminal hole 30. Areas of the wiring patterns 32
that extend across the input terminal hole 30 define input
terminals 36 (a region where they are formed is shown in the
figure) that are to be connected to connection terminals formed on
an external substrate.
[0042] Output inner leads 38 (a region where they are formed is
shown in the figure) are formed along an opposite edge of the
device hole 28 on the opposite side of the edge where the input
inner leads 34 are formed. The output inner leads 38 may also be
also formed in the number corresponding to the number of connection
terminals of a semiconductor chip.
[0043] Wiring patterns 40 (a region where they are formed is shown
in the figure) having the output inner leads 38 defining one end
sections thereof extend to an opposite side of the area where the
input terminal hole 30 is formed. The other end sections of the
wiring patterns 40 are plated with solder to define output
terminals 42 that are to be connected to another external
substrate.
[0044] FIG. 1 is an illustration to describe a process for
manufacturing a film carrier tape using a plating apparatus in
accordance with one embodiment of the present invention. As shown
in the figure, a plating apparatus 44 for performing a plating
process for the film carrier tape 20 has two plating baths and a
transfer path that is set to pass through the two plating
baths.
[0045] The plating apparatus 44 has a first plating bath 46 and a
second plating bath 48. These plating baths may be formed by
dividing one container 50 using a partition 52. Vinyl chloride or
rubber may preferably be coated on internal surfaces of the first
plating bath 46 and the second plating bath 48 in order to prevent
corrosion by the plating liquid. The first plating bath 46 and the
second plating bath 48 are preferably provided with independent
heaters that function as independent temperature controller means.
The heaters are operated to control the temperatures of the plating
liquids in the plating baths.
[0046] A transfer path 54 for transferring the film carrier tape 20
is provided in a manner to pass the plating baths thus constructed.
The transfer path 54 preferably has driver-side sprockets 56 that
are disposed before and after the container 50, and follower-side
sprockets 58 that are disposed on the inside of the container 50,
in other words, inside the first plating bath 46 and the second
plating bath 48 (and above the partition 52). These sprockets
engage the sprocket holes provided on the elongated substrate 22 on
both sides in the width direction thereof such that the film
carrier tape 20 can be transferred along locations where the
sprockets are disposed.
[0047] The plural follower-side sprockets 58 are preferably
alternately disposed in the plating baths so that they are disposed
up, down, up, down and so on, in order to increase the area of the
film carrier tape 20 that is dipped in plating liquid 60. The
plating liquid 60 is preferably a solution for electroless tin
plating. The inner leads and outer leads composed of copper may be
dipped in the solution to plate their surfaces with tin. A
follower-side sprocket 58 is also provided over the top portion of
the partition 52 such that the follower-side sprocket 58
facilitates the transfer from the first plating bath 46 to the
second plating bath 48. The partition 52 defines plating baths
containing portions of the plating liquid 60 having different
temperatures. Therefore, the partition 52 may preferably be formed
with a heat-insulation material such that the heat is not conducted
from one to the other.
[0048] Furthermore, since the first plating bath 46 is used to form
only a thin plated layer on the exposed portions of the wiring
patterns 32 on the film carrier tape 20, a few of the follower-side
sprockets 58 (three of them in FIG. 1) are provided therein, and
the volume of the plating bath is small. On the other hand, the
second plating bath 48 is used to form a thick plated layer of the
same material on an upper surface of the plated layer formed in the
first plating bath 46. Therefore, the number of the follower-side
sprockets is greater (eleven of them in the figure), and the volume
of the plating bath 48 is greater than that of the first plating
bath 46.
[0049] One example of a plating process is conducted for the film
carrier tape 20 using the plating apparatus 44 in the following
manner.
[0050] The same plating liquid 60 is filled in the first plating
bath 46 and the second plating bath 48, and the heaters that are
provided in the respective plating baths are operated to set the
plating liquid 60 at predetermined temperatures, respectively. The
temperature of the plating liquid 60 in the first plating bath 46
is lower than the temperature of the plating liquid 60 in the
second plating bath 48. The temperatures of the plating liquid 60
in the first plating bath 46 and the second plating bath 48 are
independently determined in view of factors, such as, for example,
the length of the film carrier tape 20 that is dipped in the
plating liquid 60, the transfer speed, and the like. Various
conditions were considered and it was discovered that good results
can be obtained when the plating liquid 60 in the first plating
bath 46 is set at temperatures of 10-40.degree. C. and the plating
liquid 60 in the second plating bath 48 is set at temperatures of
65-70.degree. C.
[0051] After filling the plating baths with the plating liquid 60
and setting the temperatures of the plating liquid 60, the film
carrier tape 20 is transferred along the transfer path 44. The film
carrier tape 20 is first brought in the first plating bath 46 and
dipped in the plating liquid 60 whose temperature is set at a lower
level. Portions for the input inner leads 34, the input terminals
36 and the output inner leads 38 (hereafter referred to as "lead
sections") in the wiring patterns of the film carrier tape 20 are
exposed. When the exposed portions are dipped in the plating liquid
60 in the first plating bath 46, a substitution reaction takes
place on their surfaces. As a result, copper is dissolved from the
lead sections and tin is deposited on the surfaces of the lead
sections to form a plated layer. As described above, the plating
liquid 60 is set to a lower temperature, the deposition amount is
small and the substitution reaction is minimal. As a result, the
plated layer formed in the first plating bath 46 is substantially
thin as compared to a predetermined thickness of the plated layer.
(When the dipping lasts 20 seconds, a layer having a film thickness
of about 0.1 .mu.m is formed.)
[0052] FIG. 3 shows an enlarged view of a main portion taken along
lines B-B in FIG. 2. The input inner leads 34 protrude from the
input terminal hole 30 formed in the elongated substrate 22. Base
sections of the input inner leads 34 define wiring patterns 32 that
are adhered to the elongated substrate 22 by an adhesive 62. In the
first plating bath 46, the substitution reaction is suppressed at
the base sections of the input terminals 36 and the substitution
reaction becomes similar to those at the other portions, such that
a plated layer having a uniform thickness is formed on the input
terminals 36. In other words, in the first plating bath 46, the
substitution reaction rate is low, and the substitution reaction at
the bases of the input terminals does not become excessive.
Therefore the occurrence of hollowed-out portions at the base
sections of the input terminals 36 is inhibited. Referring to FIG.
3, solder resist 64 is coated over the wiring patterns 32. In this
case, hollowed-out portions are not formed and a plated layer
having a uniform thickness in a manner similar to the other regions
is formed at end sections (border sections) of the solder resist
64.
[0053] After the plated layer having a uniform thickness is formed
on the exposed portions in the first plating bath 46, the film
carrier tape 20 is brought in the second plating bath 48. As
described above, the plating liquid 60 in the second plating bath
48 is set to a higher temperature than that of the plating liquid
60 in the first plating bath 46, and thus the deposition amount per
unit time is greater. The same plating material is newly deposited
through pinholes in a plated layer formed in the first plating bath
46, such that a plated layer 66 is formed. Since the plated layer
that has already been formed in the first plating bath 46 is
present as a lower layer when the plated layer 66 is formed, the
base sections of the input terminals 36 or the end sections (border
sections) of the solder resist 46 are prevented from forming
hollowed-out portions. When the film carrier tape 20 comes closer
to a last stage of the transfer path 54 in the second plating bath
48, the plated layer 66 reaches the predetermined thickness. Then,
the film carrier tape 20 is pulled out from the second plating bath
48. (The plated layer formed in the second plating bath 48 reaches,
for example, a thickness of about 0.5-0.8 .mu.m, and the dipping
time in the second plating bath 48 is about 3-4 minutes.) In the
film carrier tape 20 manufactured through the steps described
above, the plated layer 66 formed on the input terminals 36 and the
like shown in the figure has a uniform thickness. As a result,
problems such as an increase in the wiring resistance value,
breakage of wirings and the like can be inhibited.
[0054] In the manner described above, the plating apparatus 44 is
disposed in the transfer path 54 for the film carrier tape 20. As a
result, a plating process can be continuously performed by simply
transferring the film carrier tape 20, and therefore the process
efficiency is improved.
[0055] In the embodiment described above, the single container 50
is divided by the partition 52 to form the first plating bath 46
and the second plating bath 48. However, the present invention is
not limited to this embodiment. For example, these plating baths
can be formed from independent baths, and the transfer path may be
set to pass through the baths.
[0056] As described above, one method embodiment for manufacturing
a film carrier tape pertains to a method in which a wiring pattern
is formed on a flexible substrate. The film carrier tape is dipped
in a lower temperature plating liquid to form a plated layer in an
exposed portion of the wiring pattern by a substitution reaction,
and then the film carrier tape is dipped in a higher temperature
plating liquid to increase the thickness of the plated layer. As a
result, hollowed-out portions are not formed at the exposed portion
of the wiring pattern, and problems such as an increase in the
wiring resistance value, breakage of the wirings and the like can
be prevented.
[0057] Also, in an aspect of certain embodiments, the elongated
substrate is transferred along its longitudinal direction and is
continuously processed, with the result that an effective plating
process can be performed.
[0058] Furthermore, a plating apparatus according to certain
embodiments has a first plating bath containing a plating liquid
with temperatures thereof being set at a lower level, a second
plating bath containing a plating liquid with temperatures thereof
being set at a higher level, and a transfer path for a film carrier
tape in which wiring patterns are continuously formed on an
elongated flexible substrate, wherein the transfer path is provided
to pass the first plating bath and the second plating bath. As a
result, a uniform plated layer is formed on exposed portions of the
wiring patterns in the film carriers.
[0059] While the description above refers to particular embodiments
of the present invention, it will be understood that many
modifications may be made without departing from the spirit
thereof. For example, embodiments may include variations in the
temperature and time for carrying out the plating operations and a
variety of plating chemicals used may be used in addition to those
described above.
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