U.S. patent application number 09/079857 was filed with the patent office on 2001-08-23 for structure of conductive bump in wiring board.
Invention is credited to OKUNO, TOSHIO, SUZUKI, ETSUJI, YONEZAWA, AKIRA.
Application Number | 20010015012 09/079857 |
Document ID | / |
Family ID | 12901195 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015012 |
Kind Code |
A1 |
SUZUKI, ETSUJI ; et
al. |
August 23, 2001 |
STRUCTURE OF CONDUCTIVE BUMP IN WIRING BOARD
Abstract
A structure of a conductive bump in a wiring board having a
wiring pattern on a surface of an insulating base, characterized in
that a local portion of the insulating base is raised from the
surface of the insulating base to form a projection and a surface
of the projection is covered with a part of a lead forming the
wiring pattern to form a conductive bump.
Inventors: |
SUZUKI, ETSUJI;
(KANAGAWA-KEN, JP) ; YONEZAWA, AKIRA; (TOKYO,
JP) ; OKUNO, TOSHIO; (KANAGAWA-KEN, JP) |
Correspondence
Address: |
WENDEROTH LIND & PONACK
SUITE 800
2033 K STREET NW
WASHINGTON
DC
20006
|
Family ID: |
12901195 |
Appl. No.: |
09/079857 |
Filed: |
May 15, 1998 |
Current U.S.
Class: |
29/876 ; 174/168;
257/E23.004 |
Current CPC
Class: |
Y10T 29/49156 20150115;
Y10T 29/49144 20150115; H05K 2201/0355 20130101; H01L 2224/05573
20130101; Y10T 29/49208 20150115; H05K 3/205 20130101; H05K
2203/0113 20130101; H01R 12/57 20130101; H01L 23/13 20130101; H05K
2201/0367 20130101; H01L 2224/05568 20130101; H01L 2224/05599
20130101; H01L 2924/00014 20130101; H05K 2201/0382 20130101; H01L
21/4853 20130101; H05K 1/0284 20130101; H01L 2924/15173 20130101;
H05K 2201/09045 20130101; H01L 2224/16225 20130101; H01L 2924/00014
20130101; H05K 3/025 20130101; Y10T 29/49155 20150115; H05K 3/4007
20130101 |
Class at
Publication: |
29/876 ;
174/168 |
International
Class: |
H01B 017/22; H05K
001/00; H01R 043/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 1997 |
JP |
9-51951 |
Claims
What is claimed is:
1. A structure of a conductive bump in a wiring board having a
wiring pattern on a surface of an insulating base, characterized in
that a local portion of said insulating base is raised from the
surface of said insulating base to form a projection and a surface
of said projection is covered with a part of a lead forming said
wiring pattern to form a conductive bump.
2. A structure of a conductive bump in a wiring board characterized
in that a bump is formed by a part of a lead forming said wiring
pattern and a cavity is formed in said bump.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a structure of a wiring board used
for contact or connection with a given electronic part such as an
IC or the like, and more particularly to a conductive bump in a
wiring board to be subjected to the above contact or
connection.
[0002] In this embodiment, the term "contact" refers to an
electrical connection through free contact surface which comes into
and out of connection freely, and the term "connection" refers to
an electrical connection disconnectably joined through solder or
the like.
[0003] Conventionally, when a given electronic part such as an IC
is to be loaded on a wiring board for electrical connection, a
wiring pattern is formed on the surface of the wiring board and an
unlike metal such as a conductive paste or the like is bulged to
form a conductive bump on the surface of a lead forming this wiring
pattern, so that a terminal of the electrical part is contacted
with or connected to the conductive bump.
[0004] Also, for achieving an electrical connection between a
wiring board and another wiring board, according to another
conventional method, the conductive bump is formed on the lead
forming the wiring pattern of one of the wiring boards and
contacted with or connected to a terminal formed on an end of the
lead of the other wiring board.
[0005] However, the above conventional method for forming the
conductive bump on the conductive lead of the wiring board by
raising an unlike metal such as a solder paste or the like has such
problems that the method for forming thereof is complicated, a
positional accuracy is difficult to obtain, the configuration of
the height of the conductive bumps is irregular, and so forth.
Although this conventional technique can effectively cope with the
requirement for a smaller pitch arrangement of terminals, actual
practice thereof is jeopardized because of the above problems.
[0006] The present invention has been accomplished in view of the
above situation.
SUMMARY OF THE INVENTION
[0007] It is, therefore, a general object of the present invention
to provide a structure of a conductive bump in a wiring board which
is capable of properly solving the above problems and enhancing the
actual practice thereof.
[0008] To achieve the above object, there is essentially provided a
structure of a conductive bump in a wiring board having a wiring
pattern on a surface of an insulating base, characterized in that a
local portion of the insulating base is raised from the surface of
the insulating base to form a projection and a surface of the
projection is covered with a part of a lead forming the wiring
pattern to form a conductive bump.
[0009] From another aspect of the present invention, there is also
provided a structure of a conductive bump in a wiring board
characterized in that a bump is formed by a part of a lead forming
the wiring pattern and a cavity is formed in the bump.
[0010] A more complete application of the present invention and
many of the attendant advantages thereof will be readily obtained
as the same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of a wiring board according to
the present invention with a given electronic part such as an IC
loaded thereon;
[0012] FIG. 2A is a sectional view of the wiring board of FIG. 1,
showing a structure of a bump in which a conductive bump is backed
up with an insulating projection, and FIG. 2B is a sectional view
of FIG. 2A, showing a structure of a bump in which the conductive
bump is backed up by a cavity;
[0013] FIG. 3A is an enlarged sectional view of FIG. 2A and FIG. 3B
is an enlarged sectional view of FIG. 2B;
[0014] FIGS. 4A to 4E are sectional views showing the first example
of a method of manufacturing a wiring board having the structure of
a bump of FIG. 2A in the sequential order of processes;
[0015] FIGS. 5A to 5E are sectional views showing the second
example of a method of manufacturing a wiring board having the
structure of a bump of FIG. 2A in the sequential order of
processes;
[0016] FIGS. 6A and 6B are sectional views showing the third
example of a process of manufacturing a wiring board having a
structure of a bump of FIG. 2A;
[0017] FIG. 7A is a sectional view of a wiring board showing a
structure of a bump in which the conductive bump is of a hollow
structure and backed up by the cavity and FIG. 7B is a plan view of
FIG. 7A;
[0018] FIGS. 8A to 8E are sectional views showing one example of a
method of manufacturing a wiring board of FIG. 7 in the sequential
order of processes;
[0019] FIG. 9 is an enlarged sectional view of a bump portion,
showing an example in which the conductive bump is made of hard
metal;
[0020] FIG. 10 is a sectional view showing a tool for forming the
conductive bump forming recesses in the transfer plate; and
[0021] FIGS. 11 A and 11B are side views showing another example of
a tool for forming the conductive bump forming recesses in the
transfer plate, and FIG. 11C is a perspective view showing still
another example thereof.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0022] As shown in FIG. 1, the wiring board 1 has a wiring pattern.
This wiring pattern is formed by a lead 3 integrally attached to
the surface of the insulating base 2 and extending in that
condition. On end of the lead 3 is concentrated in a loading area
of the IC 4 so the a conductive bump 3a is formed by one end of the
lead. The pump 3a thus formed is subjected to contact or connection
with a pad (terminal) 5 intimately contacted with the surface of
the IC 4.
[0023] As means for forming the conductive bump 3a, as shown in
FIGS. 2A, 3A and 3B, a local portion of the insulating base 2 is
raised from the surface of the insulating base 2 to form an
insulating projection 6. This projection 6 is covered with a part
of the lead 3. That is, the lead 3 is wired in such a manner as to
cover the projection, thereby forming the conductive bump 3a on an
end portion of the lead 3.
[0024] This conductive bump 3a is a bump which is formed by a known
technique for forming the lead 3 on the surface of the insulating
base 2. This bump 3a has a bump structure in which an internal
cavity, which can be formed when a part of the lead 3 is given with
a chevron-like configuration, is filled by the projection 6 formed
by locally raising the insulating base 2 and backed up.
[0025] The above conductive bump 3a can be realized, for example,
by a lead forming method of FIG. 4.
[0026] As shown in FIG. 4A, a transfer plate 8 formed of a metal
plate as represented by SUS and provided with a chevron-like bump
forming recess 7 opening at the surface, is prepared.
[0027] Then, as shown in FIG. 4B, a conductive film 10 is
integrally overlain on the surface of the transfer plate 8. This
conductive film 10 covers the entire surface of the transfer plate
8. However, where the bump forming recess 7 exists, the conductive
film 10 is intimately contacted with the bottom surface in the
recess 7 and given with a chevron-like configuration thereby to
form the conductive bump 3a and further to form the recess 7
inwardly of the conductive bump 3a.
[0028] Then, as shown in FIG. 4C, an insulating layer is formed on
the surface of the conductive film 10, thereby forming the
insulating base 2 having a uniform thickness.
[0029] This insulating layer, i.e., the insulating layer 2 is
partly filled in the recess 7 and locally raised to form the
insulating projection 6 and further to form the conductive bump 3a
which is integrally intimately contacted with the surface of the
projection 6 to cover thereof.
[0030] Then, as shown in FIG. 4D, the insulating base 2 is removed
from the transfer plate 8. Then, as shown in FIG. 4E, the surface
of the insulating base 2 thus removed is subjected to etching
treatment so that the wiring pattern is formed. Thus, the bump 3a
covering the projection 16 is formed by a part of the lead 3
forming the wiring pattern. In other words, the bump 3a covering
the projection 6 by a part of the lead 3 is formed on an end
portion of the lead 3 or at an intermediate part of the lead 3.
[0031] FIG. 5 shows another method for forming the bump 3a of FIGS.
2A, 3A and 3B.
[0032] As shown in FIG. 5A, the transfer sheet 8 made of a metal
plate as represented by SUS and provided with the chevron-like bump
forming recesses 7 opening at the surface thereof is prepared.
[0033] Then, as shown in FIG. 5B, a photoresist is applied to the
surface of the transfer plate 8, or a photoresist is laminated on
the surface of the transfer plate 8 and subjected to patterning
treatment through exposure and development so that resist patterns
11 are formed.
[0034] Then, as shown in FIG. 5C, the wiring pattern (lead 3) is
grown on the surface of the transfer plate 8 between the resist
patterns 11 through plating.
[0035] One end or an intermediate part of the lead 3 thus grown is
integrally contacted with the bottom surface in the recess 7 at its
area where the bump forming recess 7 exists and given with the
chevron-like configuration, thereby forming the conductive bump 3a
and further forming the recess 7 in the inner surface of the
conductive bump 3a.
[0036] As shown in FIG. 5D, an insulating layer having a uniform
thickness is formed in such a manner as to cover the surface of the
wiring pattern. this insulating layer, i.e., the insulating base 2
is partly filled in the bump forming recess 7 to raise a local
portion of the insulating base 2 so that the insulating projection
6 is formed. By doing so, there can be formed the conductive bump
3a which is integrally intimately contacted with the surface of the
insulating projection 6 to cover the surface.
[0037] Then, as shown in FIG. 5E, the insulating base 2 is removed
from the transfer plate 8 to obtain the wiring board 1 having a
structure of a conductive bump of FIGS. 2A, 3A and 3B.
[0038] FIG. 6 shows a method of manufacturing a wiring board having
a structure in which the conductive bump 3a is backed up by the
insulating projection 6.
[0039] As shown in FIG. 6A, a transfer plate 6 made of metal having
bump forming recesses 7 as in the abovementioned example is
prepared. Then, the transfer plate 8, a conductive film 14 of a
copper foil or the like, and an insulating base 2 are superimposed
with a conductive film 14 disposed between the transfer plate 8 and
the insulating base 2. The resultant is thermally welded together
under pressure with use of a vacuum heat pressing machine or the
like to form an integral layer structure. At the same time, a part
of the insulating base 2 and a part of the conductive film 14 are
pushed into the bump forming recesses 7 altogether and the
resultant is removed to obtain a board with bumps as shown in FIG.
6B.
[0040] By pushing a local portion of the insulating base 2 and a
local portion of the conductive film 14 into the bump forming
recesses 7, a chevron-like insulating projection 6 is formed in
each recess 7. At the same time, a chevron-like conductive film 14
is formed in the recess 7 to form the conductive bump 3a.
[0041] Then, as in the same manner as in FIG. 4E, the conductive
film 14 is subjected to patterning treatment through a
photo-etching process or the like so that a wiring pattern is
obtained.
[0042] In the embodiment of FIG. 6, as means for tightly and
positively pushing the local portions of the insulating base 2 and
the conductive film 14 into the bump forming recesses 7, as shown
in FIG. 6A, the insulating bumps 15 are provided on the surface of
the insulating base 2, i.e., the surface on the other side of the
recesses 7. Then, by flatly compressing the insulating bumps 15
through a thermal pressure welding, a part of the base is tightly
filled in the recesses 7 so that the wholesome insulating
projections 6 can be formed.
[0043] In case the configuration of each conductive bump 3a is
small and the pitch is very small, too, the bumps 15 made of
comparatively harder insulating material than the base 2 are formed
on the insulating base 2 by printing or the like and then hot
pressed. By doing so, the insulating base 2 and the conductive film
14 can more effectively be pushed into the recesses 7 and the
conductive bumps 3a can be formed into a predetermined
configuration copying the inner surface of each conductive bump
3a.
[0044] As one preferred example, in a wiring board 1 having a
structure of a bump in which the conductive bumps 3a are bucked up
with the insulating projections 6, a rubber material is used as a
material of the insulating base 2. By doing so, a bump structure in
which the conductive pumps 3a are backed up with the insulating
projections 6 made of rubber material can be formed. In case the
conductive bumps 3a are brought into contact with another wiring
board or a given electronic part such as an IC or the like, as
shown in FIG. 1, it becomes possible that an appropriate elastic
force is applied to the conductive bumps 3a to increase the
contacting pressure.
[0045] In the wiring board 1 obtained by FIGS. 4, 5 and 6, a local
portion of the insulating base 2 is raised from the surface of the
base 2 to form the projections 6. When the wiring patterns are to
be formed, the surface of each projection 6 is covered with a part
of the lead 3 to form the conductive bump 3.
[0046] In FIGS. 2A, 3A, 4, 5 and 6, another wiring pattern may be
formed on the surface of the insulating base 2 on the other side of
the wiring pattern. In this case, both the wiring patterns can be
electrically connected together through the insulating base 2.
[0047] FIGS. 2B, 7A and 7B show a structure of a conductive bump in
a wiring board, in which the wiring board 1 has a wiring pattern on
the surface of the insulating base 2 and in such a wiring board 1,
the bump 3a is formed by a part of the lead 3 forming the wiring
pattern and the cavity 12 is formed in the bump 3a.
[0048] When the lead 3 is formed, a part of the lead 3 is locally
applied with a chevron configuration and the same is intimately
contacted with the insulating base 2. By doing so, the conductive
bump 3a having a cavity 12 formed between the projection and the
insulating base by the chevron-like projection can be obtained.
[0049] The conductive bump 3a is backed up by the cavity 12 and the
cavity applies an elasticity to the conductive bump 3a. The
foregoing arrangement serves as means for increasing the contacting
pressure with respect to the terminal 5 of the electronic part such
as the IC 4 or the like. In order to ensure the elastic contacting
pressure by the cavity 12, an air hole 13 leading to the cavity 12
may be formed in the insulating base 2 in such a manner that the
air hole 13 extends through the insulating base 2.
[0050] One example of a method of forming the conductive bump 3a
backed up by the cavity 12 will now be described with reference to
FIG. 8.
[0051] As shown in FIG. 8A, a transfer plate 8 made of a metal
plate as represented by SUS and provided with chevron-like bump
forming recesses 7 opening at the surface thereof is prepared.
[0052] Then, as shown in FIG. 8B, the conductive film 10 is
integrally overlain on the surface of the transfer plate 8. This
conductive film 10 covers the entire surface of the transfer plate
8. However, where the bump forming recess 7 exists, the conductive
film 10 is intimately contacted with the bottom surface in the
recess 7 and given with a chevron-like configuration thereby to
form the conductive bump 3a and further to form the recess 7
inwardly of the conductive bump 3a.
[0053] Then, as shown in FIG. 8C, an insulating base 2 is
integrally overlain on the surface of the conductive surface 8. By
doing so, the recess 7 is tightly closed to form the cavity 12.
[0054] Then, as shown in FIG. 8D, the insulating base 2 is removed
from the transfer plate 8. Then, as shown in FIG. 8E, the surface
of the insulating base 2 thus removed is subjected to etching
treatment so that the wiring pattern is formed. Thus, the bump 3a
backed up by the cavity 12 is formed on a part of the lead 3
forming the wiring pattern, for example, on an end portion of the
lead 3 or at an intermediate part of the lead 3.
[0055] A method of forming the bump forming recesses 7 in the
transfer plate 8 of FIGS. 4, 5, 6 and 8 will now be described with
reference to FIGS. 10 and 11. The conductive bumps 3a are often so
small as 10 to 50 .mu.m in height and 20 to 100 .mu.m in bottom
side length and arranged at so small pitches as 30 to 200 .mu.m.
The bump for the test use desirably has a generally conical
configuration and is required to be uniform in configuration and
pitch with precision.
[0056] In a method of forming such recesses 7 in the transfer plate
8, as shown in FIGS. 10, 11A and 11B, a tool 16 having a conical or
generally conical tip 17 and made of ultra hard metal is vertically
hammered on to the surface of the transfer plate 8 to give
hammering traces thereon. Those hammering traces each have a
conical or a generally conical configuration depending on the
configuration of the tool tip 1 and provided as the bump forming
recesses 7.
[0057] FIG. 10 shows an example in which the tool tip 17 has a
conical configuration and the recesses having the same
configuration are formed on the surface of the transfer plate
8.
[0058] In FIGS. 11A and 11B, the tool tip 17 has a conical
configuration with a cutting head. In FIG. 11A, the top surface of
the cutting head is flat, and in FIG. 11B, the top surface of the
cutting head is formed with a plurality of teeth 18 each having a
sharpened tip portion. In the example of FIG. 11C, the recesses 7
each having a trigonal prism like configuration are formed with use
of a tool 16 having a tool tip 17 of the same configuration as the
recesses 7. Accordingly, the conductive bumps 3a formed by the
recesses 7 exhibit a trigonal prism like configuration. The
sharpened ridge lines of the conductive bumps 3a are subjected to
contact with or connected to the terminals of the electronic part
such as the IC 4 or the like.
[0059] In any of the bump structure in which the conductive bumps
3a are backed up by the conductive bumps 3a as shown in FIG. 3 and
of the bump structure in which the conductive bumps 3a are backed
up by the cavities 12 as shown in FIG. 7, only the conductive bumps
3a may be made of harder metal than other lead 3 portion, such as
Ni, Cr or the like, as shown in FIG. 9.
[0060] As a method of forming thereof, prior to formation of the
conductive film 10, 14 or prior to plating of the leads 3 of FIGS.
4B, SC, 6A and 8B, the conductive bumps 3a made of hard metal are
formed on the inner surfaces of the recesses 7 and then, the soft
conductive film 10, 14 made of copper or copper alloy or the like
is overlain or the leads 3 are formed by growth of plating. In that
case, as shown in FIG. 9, the leads made of copper or copper alloy
are partly (conductive bumps 3a) formed of a hard metal as shown in
FIG. 9 or the leads 3 are partly applied with a chevron-like
configuration by the recesses 7 to form the conductive bumps 3a and
the surfaces of the conductive bumps 3a are covered with a harder
conductive metal than the bumps, so that a composite structure is
obtained. Those can be realized by the embodiments of the
manufacturing methods of FIGS. 4, 5, 6 and 8.
[0061] The abovementioned wiring board may include a case where a
plurality of leads 3 are arranged in array on the surface of the
insulating base 2 and the conductive bumps 3a having any one of the
abovementioned bump structures are provided on the end portions of
the leads 3 and thereafter, the conductive bumps 3a are brought
into contact, under pressure, with the terminals (electronic pads)
of a given electronic part such as a liquid crystal display unit or
the like.
[0062] According to the present invention, when a wiring pattern is
formed on a wiring pattern, a conductive bump can be formed by a
part of the conductive lead forming the wiring pattern and the
conductive bumps can be formed at small pitches utilizing the
technique for forming the wiring patterns at small pitches.
[0063] Furthermore, when the wiring pattern is formed through
application of the known technique for forming the wiring pattern,
merely by employing an additional means for providing the bump
forming recesses in a local area of the pattern forming surface,
uniform conductive bumps can be formed at equal pitches with
precision.
[0064] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the present invention may be practiced otherwise than as
specifically described herein.
* * * * *