U.S. patent application number 10/221616 was filed with the patent office on 2003-03-13 for printed-circuit board with fuse.
Invention is credited to Nakamura, Satoshi, Nishimura, Kohshi, Suzuki, Saizou.
Application Number | 20030048620 10/221616 |
Document ID | / |
Family ID | 27342663 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030048620 |
Kind Code |
A1 |
Nishimura, Kohshi ; et
al. |
March 13, 2003 |
Printed-circuit board with fuse
Abstract
A printed wiring board includes a substrate (20) on which a
wiring pattern (12) has been formed, and a fuse (6) provided on the
substrate (20). One end of the fuse (6) is directly connected to a
first pad (12a) of the wiring pattern (12), and the other end of
the fuse (6) is directly connected to a second pad (12b) of the
wiring pattern (12). The fuse (6) is covered by a protective
material (7).
Inventors: |
Nishimura, Kohshi; (Kyoto,
JP) ; Nakamura, Satoshi; (Kyoto, JP) ; Suzuki,
Saizou; (Kyoto, JP) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Family ID: |
27342663 |
Appl. No.: |
10/221616 |
Filed: |
September 12, 2002 |
PCT Filed: |
March 13, 2001 |
PCT NO: |
PCT/JP01/01990 |
Current U.S.
Class: |
361/760 |
Current CPC
Class: |
H05K 1/0293 20130101;
H05K 3/4697 20130101; H05K 2203/049 20130101; H05K 2201/0989
20130101; H01H 85/0047 20130101; H01H 2085/0275 20130101; H01H
85/046 20130101; H01H 2069/027 20130101; H01H 85/0411 20130101;
H05K 3/4611 20130101; H05K 2201/09063 20130101; H05K 2201/10181
20130101; H05K 2201/0305 20130101; H05K 2201/0394 20130101; H05K
1/0272 20130101; H05K 2201/10037 20130101; H01H 85/463 20130101;
H05K 2201/062 20130101; H05K 3/28 20130101; H05K 2201/09727
20130101 |
Class at
Publication: |
361/760 |
International
Class: |
H05K 007/02; H05K
007/06; H05K 007/08; H05K 007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2000 |
JP |
2000-70733 |
Mar 14, 2000 |
JP |
2000-70734 |
Mar 21, 2000 |
JP |
2000-77641 |
Claims
1. A printed wiring board, comprising: an insulating substrate on
which a wiring pattern has been formed; and a fuse including
circuit breaking means, the circuit breaking means being directly
connected to the wiring pattern.
2. The printed wiring board according to claim 1, wherein the
wiring pattern includes two conductor pads that are apart from each
other, and the circuit breaking means bridges the two conductor
pads.
3. The printed wiring board according to claim 1, wherein the
circuit breaking means is covered with a protective material.
4. The printed wiring board according to claim 1, further
comprising at least one electronic part mounted on the substrate,
and the circuit breaking means being disposed lower than the
electronic part.
5. The printed wiring board according to claim 1, wherein the
circuit breaking means is a solder wire.
6. The printed wiring board according to claim 1, further
comprising heat insulating means disposed in the vicinity of the
circuit breaking means.
7. The printed wiring board according to claim 1, wherein the
circuit breaking means is formed integrally with the wiring
pattern.
8. The printed wiring board according to claim 7, wherein the
circuit breaking means is a relatively narrow portion of the wiring
pattern.
9. The printed wiring board according to claim 8, wherein the
wiring pattern is composed of copper.
10. The printed wiring board according to claim 6, further
comprising a resist layer that covers the wiring pattern, and the
heat insulating means including an opening formed in the resist
layer.
11. The printed wiring board according to claim 6, wherein the heat
insulating means is a through hole provided to the substrate.
12. The printed wiring board according to claim 11, wherein the
circuit breaking means bridges the through hole.
13. The printed wiring board according to claim 11, wherein the
circuit breaking means is provided inside the through hole.
14. The printed wiring board according to claim 6, the heat
insulating means being a recess provided to the substrate.
15. The printed wiring board according to claim 14, wherein the
circuit breaking means bridges the recess.
16. The printed wiring board according to claim 6, further
comprising an additional insulating substrate, and the heat
insulating means including a through hole formed in the additional
insulating substrate.
17. The printed wiring board according to claim 6, further
comprising an additional insulating substrate, and the heat
insulating means including a recess formed in the additional
insulating substrate.
Description
TECHNICAL FIELD
[0001] This invention relates to a printed wiring board equipped
with a fuse.
BACKGROUND ART
[0002] Printed wiring boards equipped with fuses for circuit
protection have been used in the past in a wide variety of
electronic devices. FIG. 16 of this application illustrates a
printed wiring board 101 used in a battery pack for a cellular
telephone. This printed wiring board 101 is equipped with an
insulating substrate 102, on which a specific wiring pattern (not
shown) is formed. Also, a protection circuit 10 and a fuse 110 are
mounted on this insulating substrate 102. The protection circuit 10
serves to prevent the overcharging of a battery 2, and consists of
transistors or various other such electronic parts 11. The fuse 110
works as a failsafe device in the event that the protection circuit
10 should not function properly, and keeps excess current from
flowing into the circuit.
[0003] The printed wiring board 101 is further provided with a
charging terminal 3 for bringing electricity from a household
outlet or the like to the battery 2. This electricity is supplied
from a metal terminal 4, through the protection circuit 10 and the
fuse 110, and to the battery 2.
[0004] As shown in FIG. 17, the fuse 110 is equipped with a package
111 composed of an epoxy resin or the like, and leads 112a and 112b
which protrude in opposite directions from this package 111. The
package 111 is hollow, and an electroconductive material that will
melt at a specific temperature is disposed on the inside thereof.
The leads 112a and 112b are electrically connected to each other
via this conductive member inside the package 111.
[0005] A problem encountered with the conventional printed wiring
board 101 described above was that the size of the fuse 110 was
different from that of the electronic parts 11. Consequently, some
chip mounters for mounting the electronic parts 11 were unable to
mount the fuse 110 on the insulating substrate 102, which meant
that the fuse 110 had to be mounted manually, and this lowered the
working efficiency. Furthermore, the fuse 110 tended to be bulky
because it had the package 111. This hindered efforts at reducing
the size of the printed wiring board 101.
DISCLOSURE OF THE INVENTION
[0006] The present invention has been conceived in light of the
above situation, and it is an object thereof to provide a compact,
fused printed wiring board by a simple and inexpensive means.
[0007] The printed wiring board provided by the present invention
comprises an insulating substrate on which a wiring pattern has
been formed, and a fuse including a circuit breaking means. The
circuit breaking means is directly connected to the wiring
pattern.
[0008] In a preferred embodiment of the present invention, the
wiring pattern includes two conductor pads that are apart from each
other, and the circuit breaking means bridges the two conductor
pads.
[0009] Preferably, the circuit breaking means is covered with a
protective material.
[0010] Preferably, the printed wiring board further comprises at
least one electronic part mounted on the substrate, and the circuit
breaking means is disposed lower than the electronic part.
[0011] Preferably, the circuit breaking means is a solder wire.
[0012] Preferably, the printed wiring board further comprises a
heat insulating means disposed in the vicinity of the circuit
breaking means.
[0013] In another preferred embodiment of the present invention,
the circuit breaking means is formed integrally with the wiring
pattern. In this case, the circuit breaking means is a relatively
narrow portion of the wiring pattern, for example.
[0014] Preferably, the wiring pattern is composed of copper.
[0015] Preferably, the printed wiring board further comprises a
resist layer that covers the wiring pattern, and the heat
insulating means includes an opening formed in the resist
layer.
[0016] Preferably, the heat insulating means is a through hole or a
recess provided to the substrate. The circuit breaking means
bridges the through hole or recess. Alternatively, the circuit
breaking means may be provided inside the through hole.
[0017] In another preferred embodiment of the present invention,
the printed wiring board further comprises an additional insulating
substrate. The heat insulating means includes a through hole or
recess formed in the additional insulating substrate.
[0018] Other features and advantages of the present invention
should become clearer from the following detailed description
through reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view of the main portion of a
battery pack that incorporates the printed wiring board pertaining
to a first embodiment of the present invention;
[0020] FIG. 2 is a detail view of the fuse provided to the
above-mentioned printed wiring board;
[0021] FIG. 3 is a diagram illustrating how the fuse in FIG. 2 is
formed;
[0022] FIGS. 4A and 4B are diagrams of an example of how the fuse
in FIG. 2 is disposed;
[0023] FIG. 5 is a perspective view of the main portions of a
battery pack that incorporates the printed wiring board pertaining
to a second embodiment of the present invention;
[0024] FIG. 6 is a detail view of the fuse provided to the printed
wiring board in FIG. 5;
[0025] FIG. 7 is a detail view of the resist layer provided in the
vicinity of the fuse in FIG. 6;
[0026] FIG. 8 is a cross section along the F8-F8 line in FIG.
7;
[0027] FIG. 9 is a detail view of the main part of the printed
wiring board pertaining to a third embodiment of the present
invention;
[0028] FIG. 10 is a cross section along the F10-F10 line in FIG.
9;
[0029] FIG. 11 is a detail view of the main part of the printed
wiring board pertaining to a fourth embodiment of the present
invention;
[0030] FIG. 12 is a cross section of the portion shown in FIG.
11;
[0031] FIG. 13 shows a modification of the structure shown in FIG.
12;
[0032] FIG. 14 is another modification of the structure shown in
FIG. 12;
[0033] FIG. 15 is an exploded view of the structure of the fuse in
FIG. 11;
[0034] FIG. 16 is a perspective view of the structure of a
conventional battery pack; and
[0035] FIG. 17 is a perspective view of a conventional fuse.
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] Preferred embodiments of the present invention will now be
described in specific terms through reference to the appended
drawings.
[0037] FIG. 1 illustrates the main portion of a battery pack A that
incorporates the printed wiring board 1 pertaining to a first
embodiment of the present invention. The battery pack A is equipped
with a chargeable battery 2, which can be used, for instance, as a
drive power source of a cellular telephone. The battery 2 is
connected via two metal conductors 4 to a wiring pattern 12 (only
partially depicted) formed on the wiring board 1. The wiring board
1 includes a substrate 20 composed of an insulating material (such
as glass epoxy) , and on the back side thereof are formed four
terminals 3 for receiving the supply of electricity from an
external power source and charging the battery 2. Four terminals 5
for supplying electricity from the battery 2 to the outside are
provided on the top side of the wiring board 1.
[0038] A protection circuit 10 for preventing excess current from
flowing into the battery 2 during charging is provided to the
wiring board 1. The protection circuit 10 consists of transistors
or various other such electronic parts 11. A fuse 6 is also
provided to the wiring board 1. As shown in FIG. 2, two conductor
pads 12a and 12b are formed as part of the wiring pattern 12 on the
substrate 20. The fuse 6 bridges these conductor pads 12a and 12b.
The fuse 6 melts and breaks the circuit when current over the safe
level flows through the wiring pattern 12.
[0039] The wiring pattern 12 can be formed, for example, by forming
a thin film of copper on the substrate 20, then removing the
unnecessary portion by photolithography. Preferably, the surface of
the conductor pads 12a and 12b are plated with gold, for instance,
after the formation of the wiring pattern 12. This allows the fuse
6 to be connected well to the conductor pads 12a and 12b.
[0040] As shown in FIG. 3, the fuse 6 can be formed by bridging the
conductor pads 12a and 12b with a wire W by wire bonding method.
More specifically, the wire W (such as a solder wire) is first
inserted into a capillary 80, and the tip thereof is made to stick
out from the capillary 80. Next, the tip of the wire W is melted
with a hydrogen flame or the like to form a ball 61. The capillary
80 is then operated so that the ball 61 is press-bonded to the
conductor pad 12a. Preferably, the capillary 80 is subjected to
high-frequency vibration at this point. This results in the wire W
being more securely connected to the conductor pad 12a.
[0041] The capillary 80 is then moved to where the other conductor
pad 12b is located. The wire W remains connected to the first
conductor pad 12a, and is played out from the tip of the capillary
80 according to the movement of the capillary 80. The capillary 80
is then operated so that the wire W is press-bonded to the second
conductor pad 12b (preferably, the capillary 80 is subjected to
high-frequency vibration at this point). Finally, the capillary 80
is moved laterally (to the right in FIG. 3) without playing out the
wire W from the capillary 80. This breaks the wire W at the
location of the second conductor pad 12b, and the fuse 6 is
obtained. As shown in FIG. 2, the fuse 6 obtained in this manner
may be covered with a potting material 7 for protection. The
potting material 7 can be formed, for example, by dropping the
liquefied glass epoxy resin from above the fuse 6.
[0042] With the first embodiment given above, the fuse 6 can be
easily formed on the substrate 20 by a conventional wire bonding
process. Therefore, no special mounting equipment is needed for the
fuse 6, which lowers the manufacturing cost and improves
manufacturing efficiency.
[0043] Also, the fuse 6 consists of just a single piece of wire,
and doesn't take up much space on the wiring board 1. Thus, as
shown in FIG. 4A, it is also possible to provide the fuse 6 between
two adjacent electronic parts 11a and 11b. Preferably, as shown in
FIG. 4B, the fuse 6 does not stick up above the tops of the
electronic parts 11a and 11b. If [the fuse 6] is thus surrounded by
the electronic parts 11a and 11b, the fuse 6 can be protected
without providing the potting material 7 (FIG. 2).
[0044] FIG. 5 the main portions of a battery pack A1 that
incorporates the printed wiring board 1' pertaining to a second
embodiment of the present invention. Just as with the printed
wiring board 1 described above, the printed wiring board 1' in FIG.
5 includes an insulating substrate 20, over which four charging
terminals 3, a fuse 6', electronic parts 11, a wiring pattern 12,
and so forth are provided.
[0045] As shown in FIG. 6, the fuse 6' is realized by making part
of the wiring pattern 12 relatively narrow in width. The wiring
pattern 12 including the fuse 6' can be formed subjecting the
conductor film formed on the substrate 20 to etching in a specific
pattern by photolithography.
[0046] With the second embodiment of the present invention, a
plurality of through holes 21 are formed in the substrate 20 in the
vicinity of the fuse 6' The illustrated through holes 21 (eight of
them in FIG. 6) are divided into two equal groups, and sandwich the
fuse 6' on either side. With this configuration, the air inside the
through holes 21 acts as a thermal insulator, making it less likely
that joule heat generated by the fuse 6' will be transmitted
through the substrate 20. Accordingly, the fuse 6' will always be
melted by the generated joule heat when excess current flows into
the fuse 6'. The through holes 21 are formed by drilling, for
example. The extent to which the joule heat generated by the fuse
6' is diffused through the substrate 20 can be adjusted by varying
the shape, size, and number of the through holes 21.
[0047] After the formation of the wiring pattern 12, as shown in
FIG. 7, a resist layer 30 made of an epoxy or acrylic resin, for
example, is formed on the substrate 20. This prevents the wiring
pattern 12 from being corroded or damaged. Preferably, the fuse 6'
is exposed on the outside by providing an opening 31 in the resist
layer 30. This keeps the heat generated by the fuse 6' from
escaping through the resist layer 30.
[0048] FIGS. 9 and 10 illustrate the main parts of a printed wiring
board 1" in a third embodiment of the present invention. In this
embodiment, the printed wiring board 1" includes first to third
insulating substrates 20a, 20b, and 20c. Although not shown in the
drawings, specific wiring patterns are formed on the upper and/or
lower sides of the substrates 20a to 20c. The same fuse 6' and
through holes 21 as in the second embodiment are formed in the
second substrate 20b (see FIG. 6). In the third embodiment, though,
nothing is provided corresponding to the resist layer 30 in FIG.
7.
[0049] As shown well in FIG. 10, a recess 40 facing the fuse 6' is
formed in the first substrate 20a. With this configuration, joule
heat generated by the fuse 6' can be prevented from being directly
transmitted to the first substrate 20a. If an additional insulating
substrate is provided over the first substrate 20a, through holes
may be formed in the first substrate 20a instead of the recess
40.
[0050] FIGS. 11 and 12 illustrate a fuse 6" provided to a printed
wiring board 1'" pertaining to a fourth embodiment of the present
invention. The printed wiring board 1'" includes first to fourth
substrates 21a to 21d, and a specific wiring pattern is formed on
the upper and/or lower side of each of these substrates. These
wiring patterns are electrically connected to each other via
through holes provided in the substrates 21a to 21d (see 13 in FIG.
15).
[0051] As shown in FIG. 12, the fuse, 6" is provided to the third
substrate 21c. The fuse 6" is exposed to the outside via through
holes 71 consisting of openings 71a to 71d formed in the substrates
21a to 21d, respectively.
[0052] The fuse 6" is provided as part of the wiring pattern formed
on the third substrate 21c, and bridges the opening 21c. The fuse
6" can be formed by first forming the specific wiring pattern on
the substrate 21c, and then making the opening 21c in the substrate
21c. An etching technique that acts only on the substrate 21c, for
example, can be used to form this opening.
[0053] The openings 71a to 71d are provided to each of the
respective substrates 21a to 21d in the embodiment illustrated in
FIGS. 11 and 12, but the present invention is not limited to this.
For instance, as shown in FIG. 13, openings 71c and 71d that
communicate with each other can be provided to just the second and
third substrates 21b and 21c. Alternatively, as shown in FIG. 14,
recesses 71b' and 71c' that communicate with each other may be
provided to the second and third substrates 21b and 21c.
[0054] Also, the fuse 6" is formed as part of the wiring pattern in
the embodiment illustrated in FIGS. 11 and 12, but the present
invention is not limited to this. For instance, as shown in FIG.
15, a fuse 6 readied separately from the 2p may be used. In this
case, the opening 71c can be formed by drilling or another such
mechanical means. In the illustrated embodiment, the fuse 6'"
comprises two terminals 60a'' and a middle portion 12b that extends
between these terminals. The terminals 60a'" are electrically
connected to the wiring pattern 12 on the second substrate 21b via
the through holes 13.
[0055] The present invention was described above, but it is obvious
that this can be modified into other embodiments. These
modifications are within the concept and scope of the present
invention, and all changes that would be obvious to a person
skilled in the art are encompassed in the claims given below.
* * * * *