U.S. patent application number 11/708613 was filed with the patent office on 2007-10-04 for solid electrolytic capacitor.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Masaaki Kobayashi.
Application Number | 20070230093 11/708613 |
Document ID | / |
Family ID | 38558577 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070230093 |
Kind Code |
A1 |
Kobayashi; Masaaki |
October 4, 2007 |
Solid electrolytic capacitor
Abstract
A multiterminal-pair solid electrolytic capacitor employing a
two-terminal type capacitor element is provided. In the solid
electrolytic capacitor 10 in accordance with the present invention,
anode terminal patterns 42A (and anode terminals 43A) are connected
to an anode part 24 of a capacitor element 12 through anode vias
44A formed in a substrate 14 and an anode pattern 38D formed on a
element carrying surface 14a. On the other hand, cathode terminal
patterns 42B (and cathode terminals 43B) are connected to a cathode
part 28 on the surface of an accumulator 26 of the capacitor
element 12 through cathode vias 44B formed in the substrate 14 and
cathode patterns 38A to 38C formed on the element carrying surface
14a. Therefore, when the solid electrolytic capacitor 10 is mounted
on a packaging substrate from the mounting surface 14b side while a
predetermined voltage is applied to four pairs of anode terminals
43A and cathode terminals 43B formed on the mounting surface 14b,
the solid electrolytic capacitor 10 functions as a
four-terminal-pair solid electrolytic capacitor.
Inventors: |
Kobayashi; Masaaki; (Tokyo,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TDK CORPORATION
TOKYO
JP
|
Family ID: |
38558577 |
Appl. No.: |
11/708613 |
Filed: |
February 21, 2007 |
Current U.S.
Class: |
361/540 |
Current CPC
Class: |
H01G 9/15 20130101; H01G
9/14 20130101; H01G 9/012 20130101 |
Class at
Publication: |
361/540 |
International
Class: |
H01G 9/00 20060101
H01G009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2006 |
JP |
2006-088412 |
Claims
1. A solid electrolytic capacitor comprising a capacitor element
having only one anode part and one cathode part, and a substrate
for carrying the capacitor element; wherein a surface of the
substrate carrying the capacitor element is formed with an anode
pattern connected to the anode part and a cathode pattern connected
to the cathode part, while the rear face of the substrate opposite
to the surface carrying the capacitor element is formed with a
plurality of terminal pairs each constituted by an anode terminal
and a cathode terminal; and wherein, through a conduction path
extending along a thickness of the substrate, each of the plurality
of anode terminals and each of the plurality of cathode terminals
formed on the rear face are connected to the anode and cathode
patterns on the surface carrying the capacitor element,
respectively.
2. A solid electrolytic capacitor according to claim 1, wherein a
region of the rear face corresponding to a element carrying region
carrying the capacitor element in the surface carrying the
capacitor element is formed with a plurality of terminal pairs.
3. A solid electrolytic capacitor according to claim 2, wherein at
least a part of the plurality of anode terminals is arranged in a
region of the rear face corresponding to a cathode part region
opposing the cathode part of the capacitor element in the element
carrying region.
4. A solid electrolytic capacitor according to claim 1, wherein one
and the other species of the anode and cathode patterns on the
surface carrying the capacitor element are formed singly and
plurally, respectively, the plurally formed patterns being
connected to a plurality of anode or cathode terminals formed on
the rear face through the conduction path.
5. A solid electrolytic capacitor according to claim 1, wherein the
anode and cathode patterns are formed adjacent to each other on the
surface carrying the capacitor element; and wherein the anode and
cathode patterns are connected to the anode and cathode terminals,
respectively, through a plurality of conduction paths, the
conduction paths for the anode pattern being located in an edge
region on the cathode pattern side, the conduction paths for the
cathode pattern being located in an edge region on the anode
pattern side.
6. A solid electrolytic capacitor according to claim 1, wherein at
least a part of the plurality of terminal pairs formed on the rear
face are such that the anode and cathode terminals alternate with
each other along a predetermined direction.
7. A solid electrolytic capacitor according to claim 1, comprising
the plurality of capacitor elements, stacked in a plurality of
stages, having the anode parts connected to each other and the
cathode parts connected to each other; wherein the anode pattern of
the substrate is connected to the respective anode parts of the
plurality of capacitor elements, while the cathode pattern of the
substrate is connected to the respective cathode parts of the
plurality of capacitor elements.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a solid electrolytic
capacitor.
[0003] 2. Related Background Art
[0004] In general, capacitor elements used in solid electrolytic
capacitors are made by employing a metal (so-called valve metal)
such as aluminum, titanium, or tantalum capable of forming an
insulating oxide film as an anode; anode-oxidizing a surface of the
valve metal, so as to form an insulating oxide film; then forming a
solid electrolyte layer made of an organic compound or the like
substantially functioning as a cathode; and providing a conductive
layer such as graphite or silver as a cathode.
[0005] For lowering the impedance of such a solid electrolytic
capacitor, there are methods of reducing equivalent series
inductance (ESL) and equivalent series resistance (ESR). Japanese
Patent Application Laid-Open No. 2001-102252 discloses a solid
electrolytic capacitor omitting a lead frame in order to reduce
ESR. The solid electrolytic capacitor disclosed in this publication
is a solid electrolytic capacitor in which a two-terminal type
capacitor element having a pair of electrodes is carried on one
surface of a substrate, whereas an electrode on the surface of the
substrate carrying the capacitor element and an electrode on the
rear face thereof are connected to each other through a through
hole.
SUMMARY OF THE INVENTION
[0006] The above-mentioned capacitor elements encompass those of
two-terminal and multiterminal types. A two-terminal type capacitor
element has only one anode part, and is used for a solid
electrolytic capacitor (single-terminal-pair solid electrolytic
capacitor) having only one pair of anode and cathode terminals
(terminal pair) in general. On the other hand, a multiterminal type
capacitor element has a plurality of anode parts, and is used for a
solid electrolytic capacitor (multiterminal-pair solid electrolytic
capacitor) having a plurality of terminal pairs in general. The
two-terminal type capacitor elements are inexpensive and easily
available, since they are simple in element form and are easy to
make.
[0007] Though such a two-terminal type capacitor element can easily
be employed for the above-mentioned single-terminal-pair solid
electrolytic capacitor, no techniques have conventionally been
known for applying it to the above-mentioned multiterminal-pair
solid electrolytic capacitors for which demands have recently been
increasing. Therefore, the development of such techniques has been
awaited.
[0008] For solving the problem mentioned above, it is an object of
the present invention to provide a multiterminal solid electrolytic
capacitor employing a two-terminal type capacitor element.
[0009] The present invention provides a solid electrolytic
capacitor comprising a capacitor element having only one anode part
and one cathode part, and a substrate for carrying the capacitor
element; wherein a surface of the substrate carrying the capacitor
element is formed with an anode pattern connected to the anode part
and a cathode pattern connected to the cathode part, while the rear
face of the substrate opposite to the surface carrying the
capacitor element is formed with a plurality of terminal pairs each
constituted by an anode terminal and a cathode terminal; and
wherein, through a conduction path extending along a thickness of
the substrate, each of the plurality of anode terminals and each of
the plurality of cathode terminals formed on the rear face are
connected to the anode and cathode patterns on the surface carrying
the capacitor element, respectively.
[0010] In this solid electrolytic capacitor, the rear face is
formed with a plurality of pairs of anode and cathode terminals.
Each anode terminal is connected to an anode part of a capacitor
element through a conduction path formed in the substrate and an
anode pattern formed on the surface carrying the capacitor element.
On the other hand, each cathode terminal is connected to a cathode
part of the capacitor element through a conduction path formed in
the substrate and a cathode pattern formed on the surface carrying
the capacitor element. Therefore, this solid electrolytic capacitor
can function as a multiterminal solid electrolytic capacitor when
mounted to a packaging substrate from the rear side while a
predetermined voltage is applied to a plurality of pairs of anode
and cathode terminals formed on the rear face, for example. Namely,
this solid electrolytic capacitor is a multiterminal solid
electrolytic capacitor employing a two-terminal type capacitor
element.
[0011] A region of the rear face corresponding to a element
carrying region carrying the capacitor element in the surface
carrying the capacitor element may be formed with a plurality of
terminal pairs.
[0012] At least a part of the plurality of anode terminals may be
arranged in a region of the rear face corresponding to a cathode
part region opposing the cathode part of the capacitor element in
the element carrying region.
[0013] One and the other species of the anode and cathode patterns
on the surface carrying the capacitor element may be formed singly
and plurally, respectively, the plurally formed patterns being
connected to a plurality of anode or cathode terminals formed on
the rear face through the conduction path.
[0014] The anode and cathode patterns may be formed adjacent to
each other on the surface carrying the capacitor element, the anode
and cathode patterns being connected to the anode and cathode
terminals, respectively, through a plurality of conduction paths,
the conduction paths for the anode pattern being located in an edge
region on the cathode pattern side, the conduction paths for the
cathode pattern being located in an edge region on the anode
pattern side. When a predetermined voltage is applied to the solid
electrolytic capacitor in this case, currents directed opposite to
each other flow through the conduction paths for the anode and
cathode patterns, respectively. Here, the conduction paths for the
anode pattern are located in the edge region on the cathode pattern
side, and thus are significantly close to the conduction paths
formed in the cathode pattern. The conduction paths for the cathode
pattern are located in the edge region on the anode pattern side,
and thus are significantly close to the conduction paths formed in
the anode pattern. Since the conduction paths for the anode pattern
and the conduction paths for the cathode pattern are thus formed in
proximity to each other, this solid electrolytic capacitor realizes
a lower ESL, thereby reducing its impedance.
[0015] At least a part of the plurality of terminal pairs formed on
the rear face may be such that the anode and cathode terminals
alternate with each other along a predetermined direction. In this
case, the solid electrolytic capacitor realizes a further lower
ESL.
[0016] The solid electrolytic capacitor may comprise a plurality of
capacitor elements, stacked in a plurality of stages, having anode
parts connected to each other and cathode parts connected to each
other, the anode pattern of the substrate being connected to the
respective anode parts of the plurality of capacitor elements, the
cathode pattern of the substrate being connected to the respective
cathode parts of the plurality of capacitor elements. This can
increase the capacitance of the solid electrolytic capacitor while
suppressing its outer size.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view showing a solid electrolytic
capacitor in accordance with an embodiment of the present
invention;
[0018] FIG. 2 is a schematic sectional view showing a major part of
the solid electrolytic capacitor shown in FIG. 1;
[0019] FIG. 3 is a view showing a state where an aluminum foil to
become a capacitor element is subjected to an anode-oxidizing
process;
[0020] FIG. 4 is a plan view showing the element carrying surface
of a substrate;
[0021] FIG. 5 is a transparent view showing the mounting surface of
the substrate;
[0022] FIG. 6 is a plan view showing the element carrying surface
of a substrate in a mode different from that shown in FIGS. 4 and
5;
[0023] FIG. 7 is a transparent view showing the mounting surface of
the substrate shown in FIG. 6;
[0024] FIG. 8 is a plan view showing the element carrying surface
of a substrate in a mode different from the substrate shown in
FIGS. 4 and 5 and the substrate shown in FIGS. 6 and 7; and
[0025] FIG. 9 is a transparent view showing the mounting surface of
the substrate shown in FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] In the following, modes which seem to be the best for
carrying out the invention will be explained in detail with
reference to the accompanying drawings. Constituents identical or
equivalent to each other will be referred to with numerals
identical to each other without repeating their overlapping
descriptions if any.
[0027] FIG. 1 is a perspective view showing an electrolytic
capacitor in accordance with an embodiment of the present
invention. As shown in FIG. 1, this electrolytic capacitor 10
comprises a capacitor element 12, a substrate 14 shaped like a
rectangular thin piece carrying the capacitor element 12, and a
resin mold 16 molding the capacitor element 12 and substrate
14.
[0028] The capacitor element 12 is a two-terminal type capacitor
element having one anode part 24 and one cathode part 28, and is
formed by successively laminating a solid polymer electrolyte layer
and a conductor layer in a part of a region (which will be
explained later) on a foil-shaped aluminum support (valve metal
support) whose surface is roughened (caused to increase its area)
and subjected to a chemical process. This will be explained more
specifically with reference to FIG. 2. FIG. 2 is a schematic
sectional view showing a major part of the electrolytic capacitor
10 shown in FIG. 1. As shown in FIG. 2, the aluminum support 18
roughened by etching has a surface 18a formed with an insulating
aluminum oxide 20 by chemical processing, i.e., anode oxidation. A
solid polymer electrolyte layer 21 infiltrates into depressions in
the aluminum support 18 having increased its area. The solid
polymer electrolyte layer 21 infiltrates into the depressions of
the aluminum support 18 while in a monomer state, and then is
polymerized by chemical oxidation or electrolytic oxidation.
[0029] A graphite paste layer 22 and a silver paste layer 23
(conductor layer) are successively formed on the solid polymer
electrolyte layer 21 by any of screen printing, infiltration
(dipping), and spray coating. The solid polymer electrolyte layer
21, graphite paste layer 22, and silver paste layer 23 construct a
cathode electrode of the capacitor element 12.
[0030] As shown in FIG. 1, the capacitor element 12 is shaped like
an oblong thin piece and is constituted by an anode part 24 which
is one longitudinal end part and an accumulator 26 which is the
remainder of the anode part 24. For convenience, the following will
be explained while referring to the longer and shorter side
directions of the capacitor element 12 as X and Y directions,
respectively, and a direction orthogonal to the X and Y directions
as Z direction.
[0031] As shown in FIG. 2, the anode part 24 is constituted by the
aluminum support 18 formed with the aluminum oxide film 20. On the
other hand, the accumulator 26 has a structure in which the outer
peripheral face of the aluminum support 18 formed with the aluminum
oxide film 20 functioning as a dielectric is covered with a cathode
part 28 made of the solid polymer electrolyte layer 21, graphite
paste layer 22, and silver paste layer 23. A band-like region at
the boundary between the anode part 24 and accumulator 26 is formed
by an insulating resin layer 27 made of an epoxy resin or a
silicone resin.
[0032] The capacitor element 12 having the form mentioned above is
shaped by punching the aluminum foil whose surface is roughened and
chemically processed. Thus shaped aluminum foil is dipped into a
chemical liquid, whereby an aluminum oxide film is formed at end
faces of the foil exposing aluminum. A preferred example of the
chemical liquid is an aqueous solution containing 3% of ammonium
adipate.
[0033] The processing for the aluminum foil to become the capacitor
element 12 will now be explained with reference to FIG. 3. FIG. 3
is a view showing a state where an aluminum foil 30 to become a
capacitor element is being subjected to an anode-oxidizing process.
First, in the surface region of a part 24A to become the anode part
24 in the aluminum foil 30, a band-like edge region on the side of
a part 26A to become the accumulator 26 is formed with the
insulating resin layer 27. Thus forming the insulating resin layer
27 in a predetermined region reliably insulates and separates the
anode part 24 and cathode part 28, which will be formed in a later
stage, from each other.
[0034] Subsequently, while being supported at the part 24A to
become the anode part 24, the aluminum foil 30 is dipped into a
chemical solution 36 made of an aqueous ammonium adipate solution
contained in a stainless beaker 34. Then, a voltage is applied such
that thus supported aluminum foil part 24A and stainless beaker 34
are held positive and negative, respectively. The value of applied
voltage can appropriately be determined according to the thickness
of the aluminum oxide film 20 to be formed, and is typically on the
order of several to 20 volts when forming the aluminum oxide film
20 having a thickness of 10 nm to 1 .mu.m.
[0035] When anode oxidation is started by voltage application, the
chemical solution 36 rises from the liquid level by capillary
action through the roughened surface of the aluminum foil 30.
Therefore, the aluminum oxide film 20 is formed over the whole
roughened surface of the aluminum foil 30 including its end faces.
The cathode part 28 is formed on thus made aluminum foil 30 by a
known method, whereby the making of the above-mentioned capacitor
element 12 is completed.
[0036] The support 14 for carrying the capacitor element 12 will
now be explained with reference to FIGS. 4 and 5. FIG. 4 is a plan
view of the element carrying surface (capacitor element carrying
surface) 14a of the substrate 14 seen from the element carrying
surface 14a side, whereas FIG. 5 is a transparent view of the rear
face (mounting surface) 14b of the element carrying surface 14a of
the substrate 14 seen from the element carrying surface 14a
side.
[0037] The substrate 14 is a printed board made of an FR4 material
(epoxy resin material), in which copper foil patterns having
predetermined forms are formed by etching on both faces 14a, 14b.
As shown in FIG. 4, four electrode patterns 38A to 38D are formed
close to each other on substantially the whole element carrying
surface 14a for carrying the capacitor element 12 in the substrate
14. The electrode patterns 38A to 38D are formed so as to be
included in an oblong element carrying region 15 where the
capacitor element 12 is carried in the element carrying surface
14a. In this embodiment, the element carrying region 15
substantially coincides with the whole area of the element carrying
surface 14a.
[0038] Among the four electrode patterns 38A to 38D, the electrode
patterns 38A and 38B have forms directed from one longer-side edge
part 14c of the substrate 14 toward the other longer-side edge part
14d and are separated from each other by a predetermined length. By
contrast, the electrode pattern 38C has a form directed from the
longer-side edge part 14d toward the longer-side edge part 14c, and
extends to the gap between the electrode patterns 38A and 38B. The
electrode pattern 38D is formed so as to integrally cover the
region left by the electrode patterns 38A, 38B, and 38C having the
above-mentioned forms.
[0039] Here, the element carrying region 15 is constituted by an
anode part region 15a facing the anode part 24 of the capacitor
element 12 and a cathode part region 15b facing the cathode part 28
on the surface of the accumulator 26 in the capacitor element 12.
The electrode pattern 38A is formed so as to overlap with both of
the anode part region 15a and cathode part region 15b of the
element carrying region 15. The electrode patterns 38B and 38C are
formed in the cathode part region 15b of the element carrying
region 15. As with the electrode pattern 38A, the electrode pattern
38D is formed so as to overlap with both of the anode part region
15a and cathode part region 15b of the element carrying region
15.
[0040] An insulating resin layer 50 (dotted part in FIG. 4) is
formed in a predetermined region in the element carrying region 15
formed with the above-mentioned electrode patterns 38A to 38D. This
insulating resin layer 50 is constructed by a material such as
epoxy resin or silicone resin, and is applied by a thickness of
several tens of microns. The insulating resin layer 50 is formed so
as to mainly cover the electrode pattern 38D in the cathode part
region 15b and the electrode pattern 38A in the anode part region
15a. In other words, parts not covered with the insulating resin
layer 50 exist in the electrode pattern 38A in the cathode part
region 15b, the electrode pattern 38B, the electrode pattern 38C,
and the electrode pattern 38D in the anode part region 15a.
[0041] Therefore, when the capacitor element 12 is mounted in the
element carrying region 15, the electrode patterns 38A to 38C are
connected to only the cathode part 28 of the capacitor element 12,
whereas the electrode pattern 38D is connected to only the anode
part 24 of the capacitor element 12. Namely, the electrode patterns
38A to 38C correspond to the cathode patterns in the present
invention, whereas the electrode pattern 38D corresponds to the
anode pattern in the present invention. Hence, in the following
explanation, the electrode patterns 38A to 38C will also be
referred to as cathode patterns, whereas the electrode pattern 38D
will also be referred to as anode pattern.
[0042] The anode part 24 of the capacitor element 12 and the
electrode pattern (anode pattern) 38D are connected to each other
by resistance welding or metal welding such as YAG laser spot, for
example. On the other hand, the cathode part 28 on the surface of
the accumulator 26 in the capacitor element 12 is connected to the
electrode patterns (cathode patterns) 38A to 38C by a conductive
adhesive (not depicted), for example.
[0043] The rear face 14b of the element carrying surface 14a of the
substrate 14 is a mounting surface opposing a packaging substrate,
whereas a region of the mounting surface 14b corresponding to the
element carrying region 15 is formed with eight terminal patterns
42A, 42B shown in FIG. 5. These eight terminal patterns 42A, 42B
are formed four by four in both longer-side edge parts 14c, 14d of
the substrate 14. The four terminal patterns 42A, 42B in each of
the longer-side edge parts 14c, 14d are aligned while being
separated from each other by a predetermined length in a direction
(depicted X direction) extending along the edge part. The terminal
patterns 42A, 42B in one edge part are paired with their
corresponding terminal patterns 42A, 42B in the other edge part,
whereas each pair of two terminal patterns 42A, 42B are aligned in
the Y direction.
[0044] The eight terminal patterns 42A, 42B formed on the mounting
surface 14b are constituted by four anode terminal patterns 42A
connected to the anode pattern 38D of the element carrying surface
14a, and four cathode terminal patterns 42B connected to the
cathode patterns 38A to 38C of the element carrying surface 14a.
Namely, the mounting surface 14b of the substrate 14 is formed with
four pairs of terminal patterns 42A, 42B each constituted by the
anode terminal pattern 42A and cathode terminal pattern 42B.
[0045] The anode terminal patterns 42A and cathode terminal
patterns 42B alternate with each other in each of the longer-side
edge parts 14c, 14d, whereas a pair of the anode terminal pattern
42A and cathode terminal pattern 42B are aligned in the Y
direction. The anode terminal patterns 42A and cathode terminal
patterns 42B are each partly covered with an insulating resin layer
51 (dotted part in FIG. 5) similar to the insulating resin layer
50, whereas exposed regions not covered with the insulating resin
layer 51 actually function as terminals (anode terminals 43A and
cathode terminals 43B). As with the anode terminal patterns 42A and
cathode terminal patterns 42B, the above-mentioned four pairs of
terminals (i.e., four anode terminals 43A and four cathode
terminals 43B) alternate with each other in a direction extending
along each longer-side edge part 14c, 14d, and align in the Y
direction to form a pair (i.e., pair of terminals 43A, 43B). Three
of the four anode terminals 43A are arranged in a region of the
mounting surface 14b corresponding to the cathode part region 15b
in the element carrying region 15.
[0046] Through a plurality of anode vias (conduction paths) 44A
penetrating through the substrate 14 in the thickness direction
(depicted Z direction), the four anode terminals 42A on the
mounting surface 14b are connected to the anode pattern 38D formed
on the element carrying surface 14a. Through a plurality of cathode
vias (conduction paths) 44B penetrating through the substrate 14 in
the thickness direction, the four cathode terminals 42B on the
mounting surface 14b are connected to their corresponding cathode
patterns 38A to 38C formed on the element carrying surface 14a.
Each of the anode vias 44A and cathode vias 44B has a circular
cross section, and is formed, for example, by drilling a through
hole in the substrate 14 and then electrolessly plating it with
copper.
[0047] As explained in detail in the foregoing, the solid
electrolytic capacitor 10 has the two-terminal type capacitor
element 12, and the substrate 14 having the mounting surface 14b
formed with the four pairs of terminal patterns 42A, 42B (terminal
pairs 43A, 43B). In this substrate 14, the anode terminal patterns
42A (and anode terminals 43A) are connected to the anode part 24 of
the capacitor element 24 through the anode vias 44A and anode
pattern 38D. On the other hand, the cathode terminal patterns 42B
(and cathode terminals 43B) are connected to the cathode part 28 on
the surface of the accumulator 26 in the capacitor element 12
through the cathode vias 44B and cathode patterns 38A to 38C.
[0048] Therefore, when the solid electrolytic capacitor 10 is
mounted on a packaging substrate from the mounting surface 14b side
while a predetermined voltage is applied to the four pairs of anode
terminals 43A and cathode terminals 43B, the solid electrolytic
capacitor 10 functions as a four-terminal-pair solid electrolytic
capacitor (multiterminal-pair solid electrolytic capacitor).
Namely, the solid electrolytic capacitor 10 is a multiterminal-pair
solid electrolytic capacitor employing the two-terminal type
capacitor element 12.
[0049] Since the capacitor element 12 is of two-terminal type, the
boundary between the anode part 24 and accumulator 26 can be made
linear. In the multiterminal type capacitor element, on the other
hand, the boundary between the anode part 24 and accumulator 26 is
hard to become linear, since anode parts are arranged in a
plurality of places. When the boundary between the anode part 24
and accumulator 26 is linear, the cathode part 28 of the
accumulator 26 can be made very easily, since the trouble of
preparing and forming complicated mask patterns and separate resist
masks or the like can be saved. Namely, the solid electrolytic
capacitor 10 employs the two-terminal type capacitor element having
the foregoing advantages in the multiterminal-pair solid
electrolytic capacitor for which demands have recently been
increasing.
[0050] Positions of the vias 44A, 44B provided in the substrate 14
will now be explained. As shown in FIG. 4, the anode vias 44A among
the vias 44A, 44B are located in edge regions of the anode pattern
38D which face the cathode patterns 38A to 38C. The cathode vias
44B among the vias 44A, 44B are located in edge regions of the
cathode patterns 38A to 39C facing the anode pattern 38D so as to
be paired with the anode vias 44A.
[0051] When the vias 44A, 44B are thus arranged, the distance
between the anode vias 44A and their corresponding cathode vias 44B
is significantly reduced, whereby each pair of the anode via 44A
and cathode via 44B approach each other. When the solid
electrolytic capacitor 10 accumulates electric charges or
discharges thus accumulated electric charges, currents directed
opposite to each other flow though the anode via 44A and cathode
via 44B, respectively. Since the anode via 44A and cathode via 44B
are close to each other as such, a magnetic field resulting from
the current flowing through the anode via 44A and a magnetic field
resulting from the current flowing through the anode via 44B
effectively cancel each other out. As a result, the equivalent
series inductance (ESL) is significantly reduced in the solid
electrolytic capacitor 10. In addition, since a plurality of (e.g.,
3) pairs of vias 44A, 44B are arranged in each pair of adjacent
edge regions of the anode pattern 38D and cathode patterns 38A to
38C, current paths are dispersed, whereby ESL is further reduced.
Since the pairs of terminals 43A, 43B are formed on the mounting
surface 14b such that the anode terminals 43A and cathode terminals
43B alternate with each other along the X direction, ESL is further
reduced in the solid electrolytic capacitor 10.
[0052] FIGS. 6 and 7 are views showing a substrate 14A in a mode
different from the above-mentioned substrate 14. This substrate 14A
differs from that of the substrate 14 in forms of electrode
patterns on the element carrying surface 14a and forms of terminal
patterns on the mounting surface 14b. Here, FIG. 6 is a plan view
of the element carrying surface 14a of the substrate 14A seen from
the element carrying surface 14a side, whereas FIG. 7 is a
transparent view of the mounting surface 14b of the substrate 14A
seen from the element carrying surface 14a side.
[0053] As shown in FIG. 6, four electrode patterns 38E to 38H are
formed close to each other on substantially the whole element
carrying surface 14a of the substrate 14A. The electrode patterns
38E to 38H are formed so as to be included in an oblong element
carrying region 15 where the capacitor element 12 is carried in the
element carrying surface 14a.
[0054] Among the electrode patterns 38E to 38H, the rectangular
electrode patterns 38E and 38F are formed so as to align in the Y
direction in their corresponding regions of both longer-side edge
parts 14c, 14d of the substrate 14 in the cathode part region 15b
of the element carrying region 15. The rectangular electrode
pattern 38G is formed in the end part region opposite to the anode
part region 15a in the cathode part region 15b of the element
carrying region 15. The H-shaped electrode pattern 38H is formed so
as to integrally cover the region left by the electrode patterns
38E to 38G having the above-mentioned forms and overlap with both
of the anode part region 15a and cathode part region 15b of the
element carrying region 15.
[0055] The insulating resin layer 50 (dotted part in FIG. 6) of the
substrate 14A is formed so as to mainly cover the electrode pattern
38H in the cathode part region 15b. In other words, parts not
covered with the insulating resin layer 50 exist in the electrode
patterns 38E to 38G and the electrode pattern 38H in the anode part
region 15a. Therefore, when the capacitor element 12 is mounted in
the element carrying region 15, the electrode patterns 38E to 38G
are connected to only the cathode part 28 of the capacitor element
12, whereas the electrode pattern 38H is connected to only the
anode part 24 of the capacitor element 12. Namely, the electrode
patterns 38E to 38G correspond to cathode patterns in the present
invention, whereas the electrode pattern 38H corresponds to the
anode pattern in the present invention.
[0056] A region of the mounting surface 14b of the substrate 14A
corresponding to the element carrying region 15 is formed with
eight terminal patterns 42A, 42B shown in FIG. 7. These eight
terminal patterns 42A, 42B are formed four by four in both
longer-side edge parts 14c, 14d of the substrate 14A, and have the
same rectangular form. The four terminal patterns 42A, 42B in each
of the longer-side edge parts 14c, 14d are aligned while being
separated from each other by a predetermined length in a direction
(depicted X direction) extending along the edge part. The terminal
patterns 42A, 42B in one edge part are paired with their
corresponding terminal patterns 42A, 42B in the other edge part,
whereas each pair of two terminal patterns 42A, 42B are aligned in
the Y direction.
[0057] The eight terminal patterns 42A, 42B formed on the mounting
surface 14b are constituted by four anode terminal patterns 42A
connected to the anode pattern 38H of the element carrying surface
14a, and four cathode terminal patterns 42B connected to the
cathode patterns 38E to 38G of the element carrying surface 14a.
Namely, the mounting surface 14b of the substrate 14A is formed
with four pairs of terminal patterns 42A, 42B constituted by anode
terminal patterns 42A and cathode terminal patterns 42B.
[0058] The anode terminal patterns 42A and cathode terminal
patterns 42B alternate with each other in each of the longer-side
edge parts 14c, 14d. The anode terminal patterns 42A or cathode
terminal patterns 42B align with each other in the Y direction. All
the cathode terminal patterns 42B are formed in regions
corresponding to the cathode patterns 38E to 38G of the element
carrying region 15.
[0059] The anode terminal patterns 42A and cathode terminal
patterns 42B are each partly covered with an insulating resin layer
51 (dotted part in FIG. 7), whereas exposed regions not covered
with the insulating resin layer 51 actually function as terminals
(i.e., anode terminals 43A and cathode terminals 43B). As with the
anode terminal patterns 42A and cathode terminal patterns 42B, the
above-mentioned four pairs of terminals (i.e., four anode terminals
43A and four cathode terminals 43B) alternate with each other in a
direction extending along each longer-side edge part 14c, 14d,
while the anode terminals 43A or cathode terminals 43B align with
each other in the Y direction. Two of the four anode terminals 43A
are arranged in a region of the mounting surface 14b corresponding
to the cathode part region 15b in the element carrying region
15.
[0060] Through a plurality of anode vias 44A, the four anode
terminal patterns 42A of the mounting surface 14b are connected to
the anode pattern 38H formed on the element carrying surface 14a.
Through a plurality of cathode vias 44B, the four anode terminal
patterns 42B of the mounting surface 14b are connected to their
corresponding cathode patterns 38E to 38G formed on the element
carrying surface 14a.
[0061] As explained in the foregoing, the mounting surface 14b of
the substrate 14A is formed with four pairs of terminal patterns
42A, 42B (terminal pairs 43A, 43B). The anode terminal patterns 42A
(and anode terminals 43A) are connected to the anode part 24 of the
capacitor element 12 through the anode vias 44A and anode pattern
38D. On the other hand, the cathode terminal patterns 42B (and
cathode terminals 43B) are connected to the cathode part 28 on the
surface of the capacitor element 12 through the cathode vias 44B
and cathode patterns 38E to 38G. Therefore, as with the solid
electrolytic capacitor 10 equipped with the above-mentioned
substrate 14, the solid electrolytic capacitor 10 equipped with the
substrate 14A functions as a four-terminal-pair solid electrolytic
capacitor (multiterminal solid electrolytic capacitor). Namely, the
solid electrolytic capacitor 10 equipped with the substrate 14A is
also a multiterminal-pair solid electrolytic capacitor employing
the two-terminal type capacitor element 12.
[0062] As with the vias 44A, 44B provided in the substrate 14, the
vias 44A, 44B provided in the substrate 14A are arranged such that
each pair of the anode via 44A and cathode via 44B are close to
each other. Namely, as shown in FIG. 6, the anode vias 44A in the
vias 44A, 44B are arranged three by three aligning in the Y
direction so as to be located in edge regions of the anode pattern
38H facing the cathode patterns 38E to 38G. The cathode vias 44B in
the vias 44A, 44B are arranged three by three, in pairs with the
anode vias 44A, aligning in the Y direction so as to be located in
edge regions of the cathode patterns 38E to 38G facing the anode
pattern 38H.
[0063] When the vias 44A, 44B are thus arranged, the anode via 44A
and cathode via 44B are close to each other, whereby ESL is also
significantly reduced in the solid electrolytic capacitor 10 having
the substrate 14A. In addition, since a plurality of (e.g., 3)
pairs of vias 44A, 44B are arranged in each pair of adjacent edge
regions of the anode pattern 38H and cathode patterns 38E to 38G,
current paths are dispersed, whereby ESL is further reduced. Since
the pairs of terminals 43A, 43B are formed on the mounting surface
14b such that the anode terminals 43A and cathode terminals 43B
alternate with each other along the X direction, ESL is further
reduced in the solid electrolytic capacitor 10.
[0064] FIGS. 8 and 9 are views showing a substrate 14B in a mode
different from the above-mentioned substrates 14, 14A. This
substrate 14B differs from that of the substrates 14, 14A in forms
of electrode patterns on the element carrying surface 14a and forms
of terminal patterns on the mounting surface 14b. Here, FIG. 8 is a
plan view of the element carrying surface 14a of the substrate 14B
seen from the element carrying surface 14a side, whereas FIG. 9 is
a transparent view of the mounting surface 14b of the substrate 14B
seen from the element carrying surface 14a side.
[0065] As shown in FIG. 8, four electrode patterns 38I to 38L are
formed close to each other on substantially the whole element
carrying surface 14a of the substrate 14B. The electrode patterns
38I to 38L are formed so as to be included in an oblong element
carrying region 15 where the capacitor element 12 is mounted in the
element carrying surface 14a.
[0066] Among the electrode patterns 38I to 38L, the rectangular
electrode patterns 38I and 38J are formed in one longer-side edge
part 14c of the substrate 14B in the cathode part region 15b of the
element carrying region 15, while being separated by a
predetermined length from each other. The rectangular electrode
pattern 38K is formed in the longer-side edge part 14d at a
position corresponding to the midpoint between the electrode
patterns 38I and 38J in the cathode part region 15b of the element
carrying region 15. The electrode pattern 38L is formed so as to
integrally cover the region left by the electrode patterns 38I to
38K having the above-mentioned forms and overlap with both of the
anode part region 15a and cathode part region 15b of the element
carrying region 15.
[0067] The insulating resin layer 50 (dotted part in FIG. 8) of the
substrate 14B is formed so as to mainly cover the electrode pattern
38L in the cathode part region 15b. In other words, parts not
covered with the insulating resin layer 50 exist in the electrode
patterns 38I to 38K and the electrode pattern 38L in the anode part
region 15a. Therefore, when the capacitor element 12 is mounted in
the element carrying region 15, the electrode patterns 38I to 38K
are connected to only the cathode part 28 of the capacitor element
12, whereas the electrode pattern 38L is connected to only the
anode part 24 of the capacitor element 12. Namely, the electrode
patterns 38I to 38K correspond to cathode patterns in the present
invention, whereas the electrode pattern 38L corresponds to the
anode pattern in the present invention.
[0068] A region of the mounting surface 14b of the substrate 14B
corresponding to the element carrying region 15 is formed with five
terminal patterns 42A, 42B shown in FIG. 9. These five terminal
patterns 42A, 42B are constituted by four anode terminal patterns
42A connected to the anode pattern 38L on the element carrying
surface 14a, and one cathode terminal pattern 42B connected to the
cathode patterns 38I to 38K on the element carrying surface
14a.
[0069] The cathode terminal pattern 42B is constituted by four
terminal parts 45 positioned in the longer-side edge parts 14c, 14d
of the substrate 14B and a connecting part 47 integrally connecting
the terminal parts 45 together. The anode terminal patterns 42A and
the terminal parts 45 of the cathode terminal pattern 42B alternate
with each other in each of the longer-side edge parts 14c, 14d,
whereas the anode terminal pattern 42 and the terminal part 45 of
the cathode terminal pattern 42B align in the Y direction, so as to
form a pair. The anode terminal patterns 42A are formed in regions
corresponding to the anode pattern 38L in the element carrying
region 15, while three of the four terminal parts 45 of the cathode
terminal pattern 42B are formed in regions corresponding to the
cathode patterns 38I to 38K in the element carrying region 15.
[0070] The connecting part 47 of the cathode terminal pattern 42B
is totally covered with an insulating resin layer 51 (dotted part
in FIG. 9) similar to the insulating resin layer 50, whereas the
anode terminal patterns 42A and the terminal parts 45 of the
cathode terminal pattern 42B are each partly covered with the
insulating resin layer 51 (dotted part in FIG. 9). The exposed
regions of the anode terminal patterns 42A and the terminal parts
45 of the cathode terminal pattern 42B, which are not covered with
the insulating resin layer 51, actually function as terminals
(anode terminals 43A and cathode terminals 43B). As with the anode
terminal patterns 42A and the terminal parts 45 of the cathode
terminal pattern 42B, the above-mentioned four pairs of terminals
(i.e., four anode terminals 43A and four cathode terminals 43B)
alternate with each other in a direction extending along each
longer-side edge part 14c, 14d, while aligning in the Y direction
in pairs (i.e., pairs of terminals 43A, 43B). Three of the four
anode terminals 43A are arranged in a region of the mounting
surface 14b corresponding to the cathode part region 15b in the
element carrying region 15.
[0071] Through a plurality of anode vias 44A, the four anode
terminal patterns 42A of the mounting surface 14b are connected to
the anode pattern 38L formed on the element carrying surface 14a.
Through a plurality of cathode vias 44B, the four anode terminal
patterns 42B of the mounting surface 14b are connected to their
corresponding cathode patterns 38I to 38K formed on the element
carrying surface 14a.
[0072] As explained in the foregoing, the mounting surface 14b of
the substrate 14B is formed with four pairs of terminal pairs 43A,
43B. The anode terminals 43A are connected to the anode part 24 of
the capacitor element 12 through the anode vias 44A and anode
pattern 38L. On the other hand, the cathode terminals 43B are
connected to the cathode part 28 on the surface of the capacitor
element 12 through the cathode vias 44B and cathode patterns 38I to
38K. Therefore, as with the solid electrolytic capacitors 10
equipped with the above-mentioned substrates 14, 14A, the solid
electrolytic capacitor 10 equipped with the substrate 14B functions
as a four-terminal-pair solid electrolytic capacitor (multiterminal
solid electrolytic capacitor). Namely, the solid electrolytic
capacitor 10 equipped with the substrate 14B is also a
multiterminal-pair solid electrolytic capacitor employing the
two-terminal type capacitor element 12.
[0073] As with the vias 44A, 44B provided in the substrates 14,
14A, the vias 44A, 44B provided in the substrate 14B are arranged
such that each pair of the anode vias 44A and cathode via 44B are
close to each other. Namely, as shown in FIG. 8, a part of the
anode vias 44A in the vias 44A, 44B are located in edge regions of
the anode pattern 38L facing the cathode patterns 38I to 38K. The
cathode vias 44B in the vias 44A, 44B are arranged in edge regions
of the cathode patterns 38I to 38K facing the anode pattern
38L.
[0074] When the vias 44A, 44B are thus arranged, each pair of the
anode via 44A and cathode via 44B are close to each other, whereby
ESL is also significantly reduced in the solid electrolytic
capacitor 10 having the substrate 14B. Since the pairs of terminals
43A, 43B are formed on the mounting surface 14b such that the anode
terminals 43A and cathode terminals 43B alternate with each other
along the X direction, ESL is further reduced in the solid
electrolytic capacitor 10.
[0075] Without being restricted to the above-mentioned embodiments,
the present invention can be modified in various ways. For example,
the number of terminal pairs on the mounting surface is not limited
to 4, but can appropriately be decreased or increased to 3, 5, and
so forth. The cross-sectional forms of anode vias and cathode vias
are not limited to perfect circles, but may be flat circles,
quadrangles, and the like. The number of vias may also be decreased
or increased as appropriate. The via may be changed to via-hole
which is pierced in the central part, if need arises.
[0076] Though the above-mentioned embodiments relate to only a
solid electrolytic capacitor including one capacitor element, it
can be changed to a solid electrolytic capacitor including a
plurality of capacitor elements as appropriate. Namely, the
above-mentioned capacitor elements are stacked in a plurality of
stages, their anode parts are connected to each other while their
cathode parts are connected to each other, the anode parts of the
capacitor elements are connected to the anode pattern of the
substrate, and the cathode parts of the capacitor elements are
connected to the cathode pattern of the substrate. Laser welding
can be used for connecting the anode parts to each other, whereas a
conductive adhesive can be used for connecting the cathode parts to
each other.
[0077] In a solid electrolytic capacitor in which a plurality of
capacitor elements are thus stacked in a plurality of stages, the
size of the element carrying region 15 is unchanged, so that the
outer size of the solid electrolytic capacitor does not
substantially change, while the number of capacitor elements
connected in parallel increases, thereby enhancing the
capacitance.
EXAMPLES
[0078] The present invention will now be explained with reference
to examples in order to further clarify its effects.
[0079] In the following manner, an electrolytic capacitor similar
to the electrolytic capacitor 10 shown in FIG. 1 was made.
[0080] First, from a roughened aluminum foil sheet having a
thickness of 100 .mu.m and yielding a capacitance of 270
.mu.F/cm.sup.2, formed with an aluminum oxide film, an aluminum
anode electrode body was made by punching such as to have the same
form as the aluminum foil 30 shown in FIG. 3 and such that the part
excluding the part corresponding to the anode part (corresponding
to numeral 24A in FIG. 3) attained a size of 4.7 mm.times.3.5 mm
(area: 0.165 cm.sup.2). In the punched electrode body, the
roughened structure in the region formed with the insulating resin
layer (region corresponding to numeral 27 in FIG. 3) was destroyed
by pressing. In thus made electrode body, only the surface of the
pressed region (region corresponding to numeral 27 in FIG. 3) was
coated with an epoxy resin applied thereto.
[0081] Further, thus obtained electrode body was set into an
aqueous ammonium adipate solution adjusted to a pH of 6.0 having a
concentration of 3 wt % such that the roughened aluminum foil
formed with the aluminum oxide film was completely immersed
therewith. Here, the electrode body was dipped into the aqueous
ammonium adipate solution up to a part of the region coated with
the epoxy resin.
[0082] Subsequently, using the part not coated with the epoxy resin
(corresponding to numeral 24A in FIG. 3) corresponding to the anode
part as an anode, the electrode body dipped in the aqueous solution
was oxidized under the condition of a processing current density of
50 to 100 mA/cm.sup.2 and a processing voltage of 12 V, so as to
form an aluminum oxide film at the cut end faces of the electrode
body.
[0083] Thereafter, the electrode body was lifted from the aqueous
solution, and a solid polymer electrolyte layer made of polypyrrole
was formed by chemical oxidation polymerization on the roughened
surface of the aluminum foil. More specifically, the electrode body
was set into a cell of an ethanol/water mixed solution containing
purified 0.1 mol/l of pyrrole monomer, 0.1 mol/l of sodium
alkylnaphthalene sulfonate, and 0.05 mol/l of iron sulphate (III)
such that only the roughened aluminum foil part (corresponding to
numeral 26A in FIG. 3) formed with the aluminum oxide film was
dipped therein, they were stirred for 30 minutes, so as to advance
the chemical oxidation polymerization, and the same operation was
repeated three times, whereby the solid polymer electrolyte layer
made of polypyrrole was produced. As a result, the solid polymer
electrolyte layer having the maximum thickness of about 50 .mu.m
was formed.
[0084] A carbon paste and a silver paste were successively applied
to the surface of thus laminated solid polymer electrolyte layer,
whereby a cathode part similar to the cathode part 28 of the
capacitor element 12 shown in FIG. 1 was formed.
[0085] Six capacitor elements made as mentioned above were stacked,
so as to form a element multilayer body. Thirty such element
multilayer bodies were prepared. Using these element multilayer
bodies, thirty solid electrolytic capacitors were made. Laser
welding was used for connecting the anode parts to each other,
whereas a silver-epoxy-based conductive adhesive was used for
connecting the cathode parts to each other.
[0086] The substrate used for each solid electrolytic capacitor was
an electrolytic capacitor packaging substrate (7.3 mm.times.4.3 mm)
whose front and rear faces were formed with copper foil electrode
patterns shown in FIG. 4 (the element carrying surface) and FIG. 5
(the rear face of the element carrying surface), and patterning was
effected by using a known photolithography technique. It was
prepared by the following technique. Here, the substrate was a
glass-cloth-containing, heat-resistant epoxy resin substrate (FR4
substrate) with a substrate thickness of 0.5 mm and a copper foil
pattern thickness of 36 .mu.m.
[0087] Through holes (having a diameter of 0.2 mm) were formed at
via positions of the substrate 14 in FIG. 4, whereas the inner
walls of the through holes, the electrode pattern surface on the
substrate surface, and the terminal pattern surface on the rear
face of the substrate were electrolessly plated with 3 .mu.m of
nickel. Further, the nickel plating was plated with 0.08 .mu.m of
gold. Furthermore, copper plating was performed so as to fill all
of the above-mentioned through holes, thereby forming vias.
[0088] After forming the vias, a coating of an epoxy resin having a
thickness of 50 .mu.m was applied by screen printing in order to
form an insulating resin layer in a predetermined region
(corresponding to the region of numeral 50 in FIG. 4 and the region
of numeral 51 in FIG. 5).
[0089] The capacitor elements of the element multilayer body were
mounted on the substrate with a silver-based conductive adhesive
such that their cathode parts overlapped with the cathode patterns
on the substrate surface. The anode parts of the capacitor elements
of the element multilayer body were connected by welding to the
anode patterns on the substrate surface with a YAG laser spot
welder manufactured by NEC.
[0090] In the foregoing manner, 30 four-terminal-pair solid
electrolytic capacitors #1 such as the one shown in FIG. 1 were
prepared.
[0091] For comparison, using the element multilayer bodies made by
the above-mentioned method, 30 each of conventional
one-terminal-pair solid electrolytic capacitors #2 in which a
element multilayer body was mounted on a resin substrate and
conventional (one-terminal-pair) lead-frame type solid electrolytic
capacitors #3 were prepared.
[0092] For each species of the solid electrolytic capacitors #1,
#2, and #3, average values of electric characteristics per 30
pieces were evaluated. Specifically, each of the solid electrolytic
capacitors #1, #2, and #3 was mounted on a predetermined evaluation
substrate, and the capacitance and S.sub.21 characteristic were
measured by using an impedance analyzer 4194A and network analyzer
8753D manufactured by Agilent Technologies. According to thus
obtained S.sub.21 characteristic, equivalent circuit simulation was
performed, so as to determine ESR and ESL values. The results were
as shown in the following Table 1.
TABLE-US-00001 TABLE 1 Number of ESR(m.OMEGA.) Capacitance(.mu.F)
Sample terminal pairs ESL(pH) <100 kHz> <120 Hz> Sample
#1 4 450.3 6.5 225.6 Sample #2 1 876.4 7.3 223.4 Sample #3 1 1237.5
8.5 226.4
[0093] As can be seen from Table 1, ESL was greatly reduced in the
solid electrolytic capacitor #1 as compared with the conventional
solid electrolytic capacitors #2, #3. The solid electrolytic
capacitor #1 also yielded a better characteristic for ESR as
compared with the conventional solid electrolytic capacitors #2,
#3. Thus, the present invention not only provides a
multiterminal-pair solid electrolytic capacitor employing a
two-terminal-type capacitor element, but also improves electric
characteristics of the solid electrolytic capacitor.
[0094] The present invention provides a multiterminal-pair solid
electrolytic capacitor employing a two-terminal-type capacitor
element.
* * * * *