U.S. patent application number 15/177493 was filed with the patent office on 2016-10-06 for electronic component, method of manufacturing the same, and mount structure of electronic component.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Hiroshi ABE, Yoshiyuki NOMURA, Junichi SAITO.
Application Number | 20160293330 15/177493 |
Document ID | / |
Family ID | 54210356 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160293330 |
Kind Code |
A1 |
ABE; Hiroshi ; et
al. |
October 6, 2016 |
ELECTRONIC COMPONENT, METHOD OF MANUFACTURING THE SAME, AND MOUNT
STRUCTURE OF ELECTRONIC COMPONENT
Abstract
An electronic component includes a main body, first and second
external electrodes, and a water-repellent film. The first and
second external electrodes are provided on a portion of a surface
of the main body. The water-repellent film is provided on another
portion of the surface of the main body and on a surface of the
first external electrode. The water-repellent film contains a
non-cross-linked silicone resin. An angle of contact of water of
about 25.degree. C. with the water-repellent film is not less than
about 100.degree. and not greater than about 160.degree..
Inventors: |
ABE; Hiroshi;
(Nagaokakyo-shi, JP) ; NOMURA; Yoshiyuki;
(Nagaokakyo-shi, JP) ; SAITO; Junichi;
(Nagaokakyo-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Nagaokakyo-shi |
|
JP |
|
|
Family ID: |
54210356 |
Appl. No.: |
15/177493 |
Filed: |
June 9, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14667928 |
Mar 25, 2015 |
9390858 |
|
|
15177493 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K 2201/10015
20130101; Y02P 70/611 20151101; H01G 13/003 20130101; H01G 4/30
20130101; H05K 2201/0769 20130101; H01G 2/065 20130101; H01G 4/224
20130101; H05K 1/181 20130101; H01G 4/248 20130101; H05K 2201/10636
20130101; Y02P 70/613 20151101; H05K 3/3436 20130101; H01G 4/232
20130101; Y02P 70/50 20151101; H01G 4/2325 20130101 |
International
Class: |
H01G 4/224 20060101
H01G004/224; H05K 3/34 20060101 H05K003/34; H01G 4/30 20060101
H01G004/30; H01G 4/232 20060101 H01G004/232; H05K 1/18 20060101
H05K001/18; H01G 4/248 20060101 H01G004/248 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2014 |
JP |
2014-077361 |
Apr 3, 2014 |
JP |
2014-077362 |
Apr 3, 2014 |
JP |
2014-077363 |
Apr 3, 2014 |
JP |
2014-077364 |
Claims
1. An electronic component, comprising: an electronic component
main body; first and second external electrodes provided on a
portion of a surface of the electronic component main body; and a
water-repellent film provided on another portion of the surface of
the electronic component main body and on a surface of the first
external electrode and containing a non-cross-linked silicone
resin; wherein the non-cross-linked silicone resin has a
weight-average molecular weight not less than about 7400 g/mol and
not more than about 8000 g/mol.
2. The electronic component according to claim 1, wherein the
electronic component main body includes first and second main
surfaces extending along a length direction and a width direction,
first and second side surfaces extending along the length direction
and a thickness direction, and first and second end surfaces
extending along the width direction and the thickness direction; on
the second main surface, a tip end portion of the first external
electrode and a tip end portion of the second external electrode
are opposed to each other in the length direction; and the
water-repellent film is located on a portion of the second main
surface, which is located between the tip end portion of the first
external electrode and the tip end portion of the second external
electrode.
3. The electronic component according to claim 1, wherein the
water-repellent film extends across the another portion of the
surface of the electronic component main body and the surface of
the first external electrode.
4. The electronic component according to claim 1, wherein the
water-repellent film covers an entire surface of an exposed portion
of the electronic component main body and each of the first and
second external electrodes.
5. The electronic component according to claim 1, wherein each of
the first and second external electrodes includes a plurality of
layers, and an outermost layer of each of the first and second
external electrodes contains at least one of Sn, Cu, and Ag.
6. A mount structure of an electronic component, comprising: the
electronic component according to claim 1; a mount substrate on
which the electronic component is mounted; and solder joining the
electronic component and the mount substrate to each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electronic component, a
method of manufacturing the same, and a mount structure of an
electronic component.
[0003] 2. Description of the Related Art
[0004] Reduction in size and thickness has recently been
accelerated in electronic devices such as a portable telephone and
a portable music player. Concurrently, for example, reduction in
size of an electronic component contained in an electronic device
has also been demanded. Such electronic devices are used in various
environments, and improvements in the reliability of electronic
components in various environments have been desired.
[0005] As described in International Publication WO2002/082480, ion
migration in an electronic component has recently given rise to a
problem in some cases. Ion migration occurs, for example, as
follows. A temperature difference between an electronic component
and outside air causes condensation at a surface of the electronic
component, and water droplets produced due to condensation form at
the surface of the electronic component, a water film which
connects external electrodes to each other. When a voltage is
applied across the external electrodes of the electronic component
in such a state, ionized metallic species is dissolved and
precipitated from the external electrodes in the water film. This
problem occurs more noticeably when the electronic component is
mounted on a car placed in a severe environment. WO2002/082480
describes providing a water-repellent film between external
electrodes in order to suppress the occurrence of ion migration.
WO2002/082480 describes formation of a water-repellent film with
the use of a cross-linked silane coupling agent which contains
fluorine.
[0006] In general, an electronic component is used as being mounted
on a mount substrate with the use of solder. However, an electronic
component provided with a water-repellent film may have low mount
ability.
SUMMARY OF THE INVENTION
[0007] Preferred embodiments of the present invention provide an
electronic component with excellent mountability with the use of
solder while the occurrence of ion migration is significantly
reduced or prevented, a method of manufacturing the same, and
amount structure of an electronic component.
[0008] An electronic component according to a preferred embodiment
of the present invention includes an electronic component main
body, first and second external electrodes, and a water-repellent
film. The first and second external electrodes are provided on a
portion of a surface of the electronic component main body. The
water-repellent film is provided on another portion of the surface
of the electronic component main body and a surface of the first
external electrode. The water-repellent film contains a
non-cross-linked silicone resin. An angle of contact of water of
about 25.degree. C. with the water-repellent film preferably is not
less than about 100.degree. and not greater than about 160.degree.,
for example.
[0009] An electronic component according to another preferred
embodiment of the present invention includes an electronic
component main body, first and second external electrodes, and a
water-repellent film. The first and second external electrodes are
provided on a portion of a surface of the electronic component main
body. The water-repellent film is provided on another portion of
the surface of the electronic component main body and a surface of
the first external electrode. The water-repellent film contains a
non-cross-linked silicone resin. The non-cross-linked silicone
resin preferably has a weight-average molecular weight not less
than about 7400 g/mol and not greater than about 8000 g/mol, for
example.
[0010] An electronic component according to another preferred
embodiment of the present invention includes an electronic
component main body, first and second external electrodes, and a
water-repellent film. The first and second external electrodes are
provided on a portion of a surface of the electronic component main
body. The water-repellent film is provided on another portion of
the surface of the electronic component main body and a surface of
the first external electrode. The water-repellent film is soluble
in an organic solvent.
[0011] An electronic component according to another preferred
embodiment of the present invention includes an electronic
component main body, first and second external electrodes, and a
water-repellent film. The first and second external electrodes are
provided on a portion of a surface of the electronic component main
body. The water-repellent film is provided on another portion of
the surface of the electronic component main body and a surface of
the first external electrode. The water-repellent film is soluble
in a solvent contained in a solder flux.
[0012] An electronic component according to another preferred
embodiment of the present invention includes an electronic
component main body, first and second external electrodes, and a
water-repellent film. The first and second external electrodes are
provided on a portion of a surface of the electronic component main
body. The water-repellent film is provided on another portion of
the surface of the electronic component main body and a surface of
the first external electrode. The water-repellent film preferably
is a silicone resin film having a thickness not greater than about
200 nm, for example.
[0013] An outermost layer of each of the first and second external
electrodes preferably contains at least one of Sn, Cu, and Ag.
[0014] The electronic component main body preferably includes first
and second main surfaces extending along a length direction and a
width direction, first and second side surfaces extending along the
length direction and a thickness direction, and first and second
end surfaces extending along the width direction and the thickness
direction. On the second main surface, a tip end portion of the
first external electrode and a tip end portion of the second
external electrode are opposed to each other in the length
direction. The water-repellent film is located on a portion of the
second main surface, which is located between the tip end portion
of the first external electrode and the tip end portion of the
second external electrode.
[0015] The water-repellent film preferably extends across another
portion of the surface of the electronic component main body and
the surface of the first external electrode.
[0016] The water-repellent film preferably covers the entire
surface of an exposed portion of the electronic component main body
and each of the first and second external electrodes.
[0017] The solvent contained in the solder flux preferably is an
organic solvent.
[0018] The organic solvent preferably includes at least one
selected from the group consisting of an ether-based organic
solvent, an alcohol-based organic solvent, a hydrocarbon-based
organic solvent, a ketone-based solvent, an ester-based solvent,
and a glycol-ether-based solvent.
[0019] The solvent preferably has a solubility parameter (an SP
value) of not less than about 7.0 and not greater than about 14.0,
for example.
[0020] The water-repellent film preferably is a silicone resin film
having a thickness not greater than about 100 nm, for example.
[0021] The silicone resin film preferably contains a
non-cross-linked silicone resin.
[0022] A method of manufacturing an electronic component according
to another preferred embodiment of the present invention includes
the steps of forming a first external electrode and a second
external electrode on a portion of a surface of an electronic
component main body and providing on another portion of the surface
of the electronic component main body and a surface of the first
external electrode, a water-repellent film containing a
non-cross-linked silicone resin, of which an angle of contact with
water of about 25.degree. C. is not less than about 100.degree. and
not greater than about 160.degree., for example.
[0023] A method of manufacturing an electronic component according
to another preferred embodiment of the present invention includes
the steps of forming a first external electrode and a second
external electrode on a portion of a surface of an electronic
component main body and providing a water-repellent film containing
a non-cross-linked silicone resin having a weight-average molecular
weight not less than about 7400 g/mol and not more than about 8000
g/mol on another portion of the surface of the electronic component
main body and a surface of the first external electrode, for
example.
[0024] A method of manufacturing an electronic component according
to another preferred embodiment of the present invention includes
the steps of forming a first external electrode and a second
external electrode on a portion of a surface of an electronic
component main body and providing a water-repellent film soluble in
an organic solvent on another portion of the surface of the
electronic component main body and a surface of the first external
electrode.
[0025] A method of manufacturing an electronic component according
to another preferred embodiment of the present invention includes
the steps of forming a first external electrode and a second
external electrode on a portion of a surface of an electronic
component main body and providing a water-repellent film soluble in
a solvent contained in a solder flux on another portion of the
surface of the electronic component main body and a surface of the
first external electrode.
[0026] In the step of providing a water-repellent film, the
water-repellent film preferably is provided by immersing the
electronic component main body having the first and second external
electrodes formed in a treatment solution containing the
non-cross-linked silicone resin, followed by drying.
[0027] A mount structure of an electronic component according to a
preferred embodiment of the present invention includes the
electronic component described above, amount substrate, and solder.
The electronic component is mounted on the mount substrate. The
solder joins the electronic component and the mount substrate to
each other.
[0028] A water-repellent film preferably is not provided at a
junction between the electronic component and the mount
substrate.
[0029] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a perspective view showing an appearance of an
electronic component according to a first preferred embodiment of
the present invention.
[0031] FIG. 2 is a cross-sectional view of the electronic component
in FIG. 1 viewed in a direction of an arrow II-II.
[0032] FIG. 3 is a cross-sectional view of a mount structure of an
electronic component according to the first preferred embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] An electronic component, a method of manufacturing the same,
and amount structure of an electronic component according to
various preferred embodiments of the present invention will be
described hereinafter with reference to the drawings. In the
description of the preferred embodiments below, the same or
corresponding elements in the drawings have the same reference
characters allotted and description thereof will not be repeated. A
drawing referred to in a preferred embodiment is schematic. A scale
of a dimension of an object drawn in the drawings may be different
from a scale of a dimension of an actual object. A scale of a
dimension of an object may be different between the drawings. A
specific scale of a dimension of an object should be determined
with reference to the description below.
First Preferred Embodiment
[0034] FIG. 1 is a perspective view showing an electronic component
according to a first preferred embodiment of the present invention.
FIG. 2 is a cross-sectional view of the electronic component in
FIG. 1 viewed in a direction of an arrow II-II. FIG. 1 does not
depict a water-repellent film 20.
[0035] As shown in FIGS. 1 and 2, an electronic component 1
includes an electronic component main body 10 preferably having a
parallelepiped or substantially parallelepiped shape. An electronic
component main body 10 includes first and second main surfaces 10a
and 10b, first and second side surfaces 10c and 10d, and first and
second end surfaces 10e and 10f. Each of the first and second main
surfaces 10a and 10b extends along a length direction L and a width
direction W. Each of the first and second side surfaces 10c and 10d
extends along a thickness direction T and a length direction L.
Each of the first and second end surfaces 10e and 10f extends along
a thickness direction T and a width direction W. The length
direction L, the width direction W, and the thickness direction T
are orthogonal to one another.
[0036] In preferred embodiments of the present invention, a
"parallelepiped" includes a parallelepiped of which corner portions
or ridge line portions are rounded. That is, a member in a
"parallelepiped" shape includes a member including first and second
main surfaces, first and second side surfaces, and first and second
end surfaces in general. Projections and recesses may be provided
in a portion or in the entirety of the main surfaces, the side
surfaces, and the end surfaces.
[0037] A dimension of the electronic component main body 10 is not
particularly limited. For example, a dimension of a thickness of
the electronic component main body 10 is preferably not less than
about 0.1 mm and not greater than about 3.0 mm, a dimension of a
length of the electronic component main body 10 is preferably not
less than about 0.2 mm and not greater than about 3.5 mm, and a
dimension of a width of the electronic component main body 10 is
preferably not less than about 0.1 mm and not greater than about
3.5 mm. The electronic component main body 10 contains ceramics as
appropriate in accordance with a function of the electronic
component 1. Specifically, when the electronic component 1
functions as a capacitor, the electronic component main body 10
preferably contains dielectric ceramics. Specific examples of
dielectric ceramics include BaTiO3, CaTiO.sub.3, SrTiO.sub.3,
CaZrO.sub.3, and other suitable dielectric ceramics. To the
electronic component main body 10, for example, a subcomponent such
as an Mn compound, an Mg compound, an Si compound, an Fe compound,
a Cr compound, a Co compound, an Ni compound, a rare-earth
compound, and other suitable subcomponents may be added as
appropriate, in accordance with characteristics required of
electronic component 1.
[0038] When the electronic component 1 is a piezoelectric
component, the electronic component main body 10 preferably
contains piezoelectric ceramics. Piezoelectric ceramics are
specifically exemplified by PZT (lead zirconate titanate)-based
ceramics, for example.
[0039] When the electronic component 1 is, for example, a
thermistor, the electronic component main body 10 preferably
contains semiconductor ceramics. Semiconductor ceramics are
specifically exemplified by spinel-type ceramics, for example.
[0040] When the electronic component 1 is, for example, an
inductor, the electronic component main body 10 preferably contains
magnetic ceramics. Magnetic ceramics are specifically exemplified
by ferrite ceramics, for example.
[0041] As shown in FIG. 2, a plurality of first internal electrodes
11 and a plurality of second internal electrodes 12 are provided in
the electronic component main body 10. Each of the first internal
electrodes 11 preferably have a rectangular or substantially
rectangular shape in a plan view. The first internal electrodes 11
are provided in parallel or substantially in parallel to each of
the first and second main surfaces 10a and 10b. That is, the first
internal electrodes 11 are provided along the length direction L
and the width direction W. The first internal electrodes 11 are
exposed at the first end surface 10e and not exposed at the first
and second main surfaces 10a and 10b, the first and second side
surfaces 10c and 10d, and the second end surface 10f.
[0042] Each of the second internal electrodes 12 preferably has a
rectangular or substantially rectangular shape in a plan view. The
second internal electrodes 12 are provided in parallel or
substantially in parallel to each of the first and second main
surfaces 10a and 10b. That is, the second internal electrodes 12
are provided along the length direction L and the width direction
W. The second internal electrodes 12 are exposed at the second end
surface 10f. The second internal electrodes 12 are not exposed at
the first and second main surfaces 10a and 10b, the first and
second side surfaces 10c and 10d, and the first end surface
10e.
[0043] The first and second internal electrodes 11 and 12 are
provided alternately along the thickness direction T. The first
internal electrodes 11 and the second internal electrodes 12
adjacent to each other in the thickness direction T are opposed to
each other with a ceramic g interposed therebetween. The ceramic
portion 10g preferably has a thickness approximately not less than
about 0.5 .mu.m and not greater than about 10 .mu.m, for
example.
[0044] Each of the first and second internal electrodes 11 and 12
is composed of an appropriate conductive material. Each of the
first and second internal electrodes 11 and 12 is preferably
composed, for example, of a metal selected from the group
consisting of Ni, Cu, Ag, Pd, and Au or an alloy containing one or
more metals selected from the group consisting of Ni, Cu, Ag, Pd,
and Au (for example, an Ag--Pd alloy). Each of the first and second
internal electrodes 11 and 12 preferably has a thickness, for
example, of approximately not less than about 0.3 .mu.m and not
greater than about 2.0 .mu.m.
[0045] The electronic component 1 further includes a first external
electrode 13 and a second external electrode 14. The first external
electrode 13 and the second external electrode 14 are provided on a
portion of the surface of electronic component main body 10.
Specifically, the first external electrode 13 extends across the
entire surface of the first end surface 10e and a portion of the
surface of each of the first and second main surfaces 10a and 10b
and the first and second side surfaces 10c and 10d. The first
external electrode 13 is electrically connected to the first
internal electrode 11 at the first end surface 10e.
[0046] The second external electrode 14 extends across the entire
surface of the second end surface 10f and a portion of the surface
of each of the first and second main surfaces 10a and 10b and first
and the second side surfaces 10c and 10d. The second external
electrode 14 is electrically connected to the second internal
electrode 12 at the second end surface 10f.
[0047] In each of the first and second main surfaces 10a and 10b
and the first and second side surfaces 10c and 10d, a tip end
portion of the first external electrode 13 in the length direction
L and a tip end portion of the second external electrode 14 in the
length direction L are opposed to each other in the length
direction L.
[0048] An outermost layer of the first external electrode 13
preferably contains at least one of Sn, Cu, and Ag, for example.
Specifically, the first external electrode 13 includes a first
electrode layer 13a, a second electrode layer 13b, and a third
electrode layer 13c.
[0049] The first electrode layer 13a is provided on a portion of
the surface of the electronic component main body 10. The first
electrode layer 13a is defined by a fired electrode layer. The
fired electrode layer refers to an electrode layer obtained by
firing a paste layer obtained by applying a paste containing
conductive particles. The conductive particles contained in the
fired electrode layer may preferably be, for example, particles
containing at least one of Cu, Ni, Ag, Pd, an Ag--Pd alloy, and
Au.
[0050] The second electrode layer 13b is provided on a surface of
the first electrode layer 13a. The second electrode layer 13b may
preferably be defined by a plated layer. In the present preferred
embodiment, the second electrode layer 13b is preferably defined by
a Ni plated layer.
[0051] The third electrode layer 13c is provided on a surface of
the second electrode layer 13b. The third electrode layer 13c may
preferably be defined by a plated layer. In the present preferred
embodiment, the third electrode layer 13c preferably is defined by
a Sn plated layer.
[0052] An outermost layer of the second external electrode 14
preferably contains at least one of Sn, Cu, and Ag. Specifically,
the second external electrode 14 includes a first electrode layer
14a, a second electrode layer 14b, and a third electrode layer
14c.
[0053] The first electrode layer 14a is provided on a portion of
the surface of the electronic component main body 10. The first
electrode layer 14a is preferably defined by a fired electrode
layer. The fired electrode layer refers to an electrode layer
obtained by firing a paste layer obtained by applying a paste
containing conductive particles. The conductive particles contained
in the fired electrode layer may preferably be, for example,
particles containing at least one of Cu, Ni, Ag, Pd, an Ag--Pd
alloy, and Au.
[0054] The second electrode layer 14b is provided on a surface of
the first electrode layer 14a. The second electrode layer 14b may
preferably be defined by a plated layer. In the present preferred
embodiment, the second electrode layer 14b preferably is defined by
a Ni plated layer.
[0055] The third electrode layer 14c is provided on a surface of
the second electrode layer 14b. The third electrode layer 14c may
preferably be defined by a plated layer. In the present preferred
embodiment, the third electrode layer 14c is preferably defined by
a Sn plated layer.
[0056] The electronic component 1 further includes a
water-repellent film 20. The water-repellent film 20 is a solid of
a polymer containing a non-cross-linked silicone resin but not
containing a cross-linking agent. The water-repellent film 20 may
be defined by only a non-cross-linked silicone resin or may be
defined by a resin composition containing a filler, for
example.
[0057] The non-cross-linked silicone resin is preferably made of a
silicone oligomer or a silicone polymer not containing a
cross-linking agent, and further preferably made of a solution in
which a silicone polymer is dispersed in an organic solvent. As a
silicone oligomer or a silicone polymer not containing a
cross-linking agent, for example, a material having a trade name
such as FZ-3704, BY16-846, SF8416, SH203, 230FLUID, SF8419, and
SF8422 (all of which are manufactured by Dow Corning Toray),
XC96-B0446, XR31-B1410, XR31-B2230, and XC96-C2813 (all of which
are manufactured by Momentive Performance Materials Japan LLC), and
KC-89S, KR-500, X-40-9225, X-40-9246, X-40-9250, KR-9218, K213, and
KR-510 (all of which are manufactured by Shin-Etsu Chemical Co.,
Ltd.) can be used alone or in combination. A preferable filler is
exemplified by silica particles, for example.
[0058] The water-repellent film 20 is provided on another portion
of the surface of the electronic component main body 10 (on a
surface of an exposed portion where the first and second external
electrodes 13 and 14 are not provided) and on a surface of at least
one of the first and second external electrodes 13 and 14. Thus,
the formation of a water film on the electronic component main body
10 is significantly reduced or prevented. Therefore, the occurrence
of ion migration is significantly reduced or prevented.
[0059] Ion migration accompanies ionization of a metallic component
in an external electrode and migration of the ionized metallic
component to an opposing electrode. Therefore, contact between the
external electrode and moisture is preferably prevented so as to
prevent the occurrence of ion migration. Accordingly, in order to
more effectively prevent the occurrence of ion migration, the
water-repellent film 20 preferably covers at least a portion of the
first and second external electrodes 13 and 14. The water-repellent
film 20 more preferably covers the tip end portions of the first
and second external electrodes 13 and 14. The water-repellent film
20 further preferably extends across the surface of at least one of
the first and second external electrodes 13 and 14 and the surface
of the electronic component main body 10.
[0060] In order to prevent ions generated at one of the first and
second external electrodes 13 and 14 from reaching the other of the
external electrodes, the water-repellent film 20 is preferably
provided on at least one of the first and second main surfaces 10a
and 10b and the first and second side surfaces 10c and 10d, so as
to separate the first external electrode 13 and the second external
electrode 14 from each other.
[0061] The water-repellent film 20 further preferably covers the
entire surface of the exposed portion of the electronic component
main body 10 and the first and second external electrodes 13 and
14. Here, the water-repellent film 20 covering the entire surface
of the exposed portion of the electronic component main body 10 and
the first and second external electrodes 13 and 14 indicates that
the water-repellent film 20 covers about 90% or more of the entire
surface of the exposed portion of the electronic component main
body 10 and the first and second external electrodes 13 and 14. For
example, in a case in which the water-repellent film 20 is made of
a silicone resin, when the exposed portion of the electronic
component main body 10 and the first and second external electrodes
13 and 14 are subjected to Si mapping in a field of view of about
50 .mu.m.sup.2 with the use of time-of-flight secondary ion mass
spectrometry (TOF-SIMS), ions including Si are detected from a
portion covered with the water-repellent film 20. Namely, the
water-repellent film 20 covering the entire surface of the exposed
portion of the electronic component main body 10 and the first and
second external electrodes 13 and 14 indicates that, in an analysis
with TOF-SIMS, ions including Si are detected in a portion
occupying about 90% or more of the entire surface of the exposed
portion of the electronic component main body 10 and the first and
second external electrodes 13 and 14.
[0062] FIG. 3 is a cross-sectional view of a mount structure of an
electronic component according to the first preferred embodiment of
the present invention. As shown in FIG. 3, a mount structure 2 of
the electronic component includes the electronic component 1, a
mount substrate 30, and solder 32. The electronic component 1 is
mounted on the mount substrate 30. A land 31 provided on a mount
surface 30a of the mount substrate 30 and the first and second
external electrodes 13 and 14 are joined to each other by solder
32. A solder member 32 (for example, a solder ball) includes solder
and a solder flux. The solder flux contains a solvent. The solvent
contained in the solder flux may be an aqueous solvent or an
organic solvent.
[0063] For example, when a surface of the electronic component main
body is modified with a cross-linked silane coupling agent, there
is an upper limit to an amount of the silane coupling agent per
unit area with which the surface can be modified. In particular, as
a water-repellent group having a long straight chain is introduced
in order to obtain an excellent liquid repellent property, steric
hindrance between adjacent silane coupling agents is more
significant, and thus, an amount of silane coupling agent per unit
area with which the surface of the electronic component main body
can be modified decreases. Therefore, it is difficult to modify the
surface densely with the silane coupling agent having a
water-repellent group with a long straight chain.
[0064] Specifically, as a straight chain of a water-repellent group
of the silane coupling agent is increased in length, steric
hindrance is more significant and repulsive force between straight
chains of the silane coupling agent is increased. Therefore, since
an interval between the straight chains of the silane coupling
agent inevitably increases, the capability to cover an electrode
portion is reduced, moisture produced by condensation is more
likely to form a water film, and ion migration may occur through
the generation process described above.
[0065] Since a treatment film formed with the silane coupling agent
is provided on a surface of an electronic component in a state of
an elementary substance (a monomer) having one Si (silicon) atom, a
portion where monomers are not bonded to each other is produced.
Therefore, it is difficult for the treatment film defined by the
silane coupling agent to have a dense film structure. Accordingly,
it is difficult to provide a dense water-repellent film if a
surface of an electronic component main body is modified with a
silane coupling agent.
[0066] International Publication WO2002/082480 proposed a method of
providing high water repellency by using a silane coupling agent
including F (fluorine) in a functional group. With this method, the
length of a straight chain of a silane coupling treatment film can
be reduced. However, even with the silane coupling treatment, there
is a portion where bonding between silicon and silicon is
insufficient. Thus, the capability to cover an electrode portion is
insufficient in a silane coupling treatment film including F
(fluorine) in a functional group, and resistance to ion migration
cannot sufficiently be produced. A molecular weight of a
water-repellent film including a cross-linked silane coupling agent
is undesirably high. Therefore, it becomes difficult for the
water-repellent film to be dissolved in a solvent contained in a
solder flux. Therefore, when a water-repellent film includes a
cross-linked silane coupling agent, the mountability of an
electronic component is reduced.
[0067] In the electronic component 1, a water-repellent film 20
containing a non-cross-linked silicone resin is provided. This is
because, by using a water-repellent film containing a
non-cross-linked silicone resin as the water-repellent film 20,
unlike a cross-linked silane coupling treatment film, no
cross-linking reaction occurs during film formation, and thus,
control of the number of repeating units in siloxane bond is
facilitated and a molecular weight of a treatment agent is
prevented from undesirably increasing. Thus, a problem in that the
water-repellent film 20 is not dissolved in a solvent contained in
a solder flux and the mountability of an electronic component being
reduced are avoided, and a dense treatment film is provided. A
water-repellent film containing a non-cross-linked silicone resin
is preferably composed of a polymer constituted of such siloxane
bond as being expressed as --Si--O--Si, and silicon is connected to
form a high-polymer structure in a chain or lump. Therefore, a
water-repellent film containing a non-cross-linked silicone resin
has a dense structure. Thus, the water-repellent film 20 is denser
and more water-repellent than a water-repellent film including a
cross-linked silane coupling agent. Therefore, by providing the
water-repellent film 20, as compared to a water-repellent film
including a silane coupling agent, the occurrence of ion migration
is effectively reduced or prevented.
[0068] Whether a water-repellent film is of a cross-linked type or
a non-cross-linked type can be determined by heating a treatment
agent used for the water-repellent film under a condition, for
example, of about 150.degree. C. for about 30 minutes and checking
a molecular weight. Here, the determination of a non-cross-linked
water-repellent film can be made when no increase in molecular
weight as compared to a molecular weight before heating is
observed.
[0069] However, the inventors of the present invention have
unexpectedly discovered that the occurrence of ion migration cannot
sufficiently be reduced or prevented in some cases even when the
water-repellent film 20 containing a non-cross-linked silicone
resin is provided. The inventors of the present invention have
conducted further dedicated studies, and have surprisingly and
unexpectedly discovered that, when an angle of contact of a
water-repellent film with water of about 25.degree. C. is
increased, from a certain angle, an effect of reducing or
preventing the occurrence of ion migration is drastically
improved.
[0070] Then, in the present preferred embodiment, the
water-repellent film 20 is provided such that an angle of contact
(a static angle of contact) of water of about 25.degree. C. with
the water-repellent film 20 is not less than about 100.degree. and
not greater than about 160.degree., for example. Thus, the
occurrence of ion migration is effectively reduced or
prevented.
[0071] An angle of contact of water of about 25.degree. C. with the
water-repellent film 20 can be measured, for example, in the
following manner, with the use of a microscopic contact angle meter
(MCA-3 manufactured by Kyowa Interface Science Co., Ltd.).
Initially, an electronic component is arranged on a horizontal base
such that a second main surface faces the base. Then, an angle of
contact of water of about 25.degree. C. with the water-repellent
film 20 can be determined by dropping water droplets at about
25.degree. C. onto the water-repellent film 20 on a first main
surface of the electronic component of which surface temperature is
about 25.degree. C. in an environment in which an ambient
temperature of the electronic component is set to about 25.degree.
C., and thereafter photographing a water film formed on the main
surface in a lateral direction. This angle of contact is a static
angle of contact measured immediately after dropping.
[0072] As described above, in order to reduce or prevent the
occurrence of ion migration, a water-repellent film is preferably
also provided on a surface of at least one of the first and second
external electrodes. However, as a result of dedicated studies
conducted by the inventors of the present invention, it has been
discovered that the mountability of an electronic component reduces
when a water-repellent film includes a cross-linked silane coupling
agent described in International Publication WO2002/082480. This is
because, though treatment with a silane coupling agent containing
fluorine (a perfluoroalkyl group) is performed in the technique
described in International Publication WO2002/082480, fluorine has
oil repellence and repels a flux in a solder paste, which has led
to reduced wettability of solder during mounting and reduced mount
ability.
[0073] In contrast, in the electronic component 1, the
water-repellent film 20 contains a non-cross-linked silicone resin.
The non-cross-linked silicone resin does not have oil repellence
and blends well with a flux in a solder paste. In addition, unlike
the silane coupling agent, the non-cross-linked silicone resin is
not directly coupled to the first and second external electrodes 13
and 14. Therefore, since the water-repellent film 20 is dissolved
in a solvent contained in a solder flux during mounting, it is
readily removed from the surface of the first and second external
electrodes 13 and 14. Accordingly, a solder melt and the first and
second external electrodes 13 and 14 tend to be in direct contact
with each other. Thus, the first and second external electrodes 13
and 14 and the solder 32 are suitably joined to each other.
Therefore, the electronic component 1 has excellent
mountability.
[0074] In the present preferred embodiment, an example in which the
first external electrode 13 extends across the surface of the first
end surface 10e and the surface of each of the first and second
main surfaces 10a and 10b and the first and second side surfaces
10c an 10d is described. An example in which the second external
electrode 14 extends across the surface of the second end surface
10f and the surface of each of the first and second main surfaces
10a and 10b and the first and second side surfaces 10c an 10d is
described. The arrangement of the first and second external
electrodes is not limited to the above-described arrangement, and
for example, the first and second external electrodes may be
provided only on the first and second end surfaces 10e and 10f of
the electronic component main body 10. The first and second
external electrodes may be provided only on the second main surface
10b of the electronic component main body 10. The first and second
external electrodes may extend across the surfaces of the first and
second end surfaces 10e and 10f and the surface of second main
surface 10b of the electronic component main body 10. In the
present preferred embodiment, an example in which an electronic
component includes two external electrodes is described. The
present preferred embodiment is not limited thereto, and an
electronic component may include three or more external
electrodes.
[0075] A method of manufacturing the electronic component 1 is not
particularly limited. The electronic component 1 can be
manufactured, for example, in the following manner. Initially, the
electronic component main body 10 including the first and second
internal electrodes 11 and 12 is prepared. The electronic component
main body 10 can be manufactured with a known method. Specifically,
the electronic component main body 10 can be manufactured, for
example, in the following manner. Initially, a ceramic green sheet
is prepared. Then, a conductive paste layer is formed by printing a
conductive paste on the ceramic green sheet. Then, after a
plurality of ceramic green sheets not including a conductive paste
layer printed thereon are stacked, a ceramic green sheet including
a conductive paste printed is stacked, and further thereon, a
ceramic green sheet including a conductive paste layer printed
thereon is stacked. A mother stack is thus fabricated. The mother
stack may be pressed with isostatic pressing. Then, by cutting and
dividing the mother stack in a plurality of pieces, a plurality of
soft ceramic elements are fabricated. Then, the electronic
component main body 10 can be completed by firing the soft ceramic
elements.
[0076] Then, the first and second external electrodes 13 and 14 are
formed on the surface of the electronic component main body 10. The
first and second external electrodes 13 and 14 can be formed, for
example, in the following manner. The first electrode layers 13a
and 14a are formed by applying a conductive paste onto a portion of
the surface of the electronic component main body 10 and baking the
conductive paste. The second electrode layers 13b and 14b are
formed on the surface of the first electrode layers 13a and 14a by
providing Ni plating. The third electrode layers 13c and 14c are
formed on the surface of the second electrode layers 13b and 14b by
providing Sn plating. Through the steps described above, the first
and second external electrodes 13 and 14 are formed.
[0077] Then, the water-repellent film 20 is formed on another
portion of the surface of the electronic component main body 10 and
the surface of the first and second external electrodes 13 and 14.
Specifically, initially, a treatment agent is prepared by diluting
a resin for forming the water-repellent film 20 with a solvent such
as an alkane-based solvent, an isoparaffin-based solvent, or a
xylene-based solvent. The water-repellent film 20 can be formed by
immersing the electronic component main body 10 including first and
second external electrodes 13 and 14 formed thereon in the
treatment agent, followed by drying. Alternatively, a treatment
agent may be applied to the electronic component main body 10
including first and second external electrodes 13 and 14 formed
thereon. A concentration of a resin in a treatment agent is
preferably, for example, not lower than about 1 mass % and not
higher than about 50 mass %, more preferably not lower than about 3
mass % and not higher than about 50 mass %, and further preferably
not lower than about 3 mass % and not higher than about 10 mass %.
A time period of immersion in the treatment agent is, for example,
approximately not shorter than about 1 minute and not longer than
about 10 minutes. Regarding conditions for drying, for example, the
electronic component main body is held, for example, at a
temperature approximately not lower than about 100.degree. C. and
not higher than about 200.degree. C. during a period approximately
not shorter than 10 minutes and not longer than about 60
minutes.
[0078] An angle of contact of the water with water-repellent film
20 can be controlled, for example, by adjusting a material used for
the water-repellent film 20 or a thickness of the water-repellent
film 20. Normally, as the thickness of the water-repellent film 20
increases, an influence caused by underlying ceramics is less
likely and, thus, an angle of contact of water with the
water-repellent film 20 tends to be greater. A thickness of the
water-repellent film 20 can be controlled, for example, by
adjusting a concentration of a water-repellent resin in a treatment
agent. Specifically, a thickness of water-repellent film 20 can be
adjusted by using a treatment solution in which a concentration of
a non-cross-linked resin is from about 1 mass % to about 60 mass
%.
[0079] An Experimental Example 1 in which the influence of an angle
of contact between water of about 25.degree. C. and a
water-repellent film on each of whether or not ion migration in an
electronic component occurs and the mountability of an electronic
component will be described below.
Experimental Example 1
[0080] In Experimental Example 1, nine types of electronic
components and mount structures of the electronic components in
Example 1 to Example 5 and Comparative Example 1 to Comparative
Example 4 were fabricated. A stack ceramic capacitor was fabricated
as the electronic component.
Example 1
[0081] An electronic component and a mount structure of the
electronic component according to Example 1 substantially the same
as the electronic component 1 according to the first preferred
embodiment were fabricated under the conditions described below. A
dimension (a design value) of the electronic component was set to
about 1.6 mm in length, about 0.8 mm in width, and about 0.8 mm in
thickness. A ceramic portion was composed of BaTiO.sub.3. The first
and second internal electrodes 11 and 12 were composed of Ni. The
first electrode layers 13a and 14a were formed from a fired
electrode layer containing Cu. The second electrode layers 13b and
14b were formed from a Ni plated layer. The third electrode layers
13c and 14c were formed from a Sn plated layer. A distance along
the length direction between the first external electrode 13 and
the second external electrode 14 in each of the first and second
main surfaces 10a and 10b was set to about 0.8 mm. A liquid
obtained by diluting a silicone polymer dispersion liquid
containing a non-cross-linked silicone resin (SD-8002 DISPERSION
manufactured by Dow Corning Toray) such that a concentration of the
non-cross-linked silicone resin was about mass % was used as a
treatment solution. For forming the water-repellent film 20, after
the electronic component main body 10 including the first and
second external electrodes 13 and 14 was immersed in the treatment
solution for about 5 minutes, the electronic component main body
was taken out of the treatment solution and dried at about
150.degree. C. for about 30 minutes. Consequently, a
water-repellent film having a thickness of approximately 5 nm was
formed. The mount structure of the electronic component was
fabricated by solder-mounting the electronic component on a
substrate with the use of solder (96.5 Sn-3 Ag-0.5 Cu paste,
M705-GRN360-K2-V manufactured by Senju Metal Industry Co.,
Ltd.).
Example 2
[0082] An electronic component and a mount structure of the
electronic component according to Example 2 were fabricated as in
Example 1 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 5 mass %.
The formed water-repellent film had a thickness of approximately 50
nm.
Example 3
[0083] An electronic component and a mount structure of the
electronic component according to Example 3 were fabricated as in
Example 1 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 20 mass
%. The formed water-repellent film had a thickness of approximately
100 nm.
Example 4
[0084] An electronic component and a mount structure of the
electronic component according to Example 4 were fabricated as in
Example 1 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 40 mass
%. The formed water-repellent film had a thickness of approximately
200 nm.
Example 5
[0085] A non-cross-linked silicone resin (SD-8002 DISPERSION
manufactured by Dow Corning Toray) was diluted with isoparaffin
such that a concentration of the non-cross-linked silicone resin
was about 5 mass %. A dispersion liquid was prepared by adding
about 1.0 mass % of hydrophobic fumed silica (RX50 manufactured by
Nippon Aerosil Co., Ltd. and having a BET specific surface area of
35 m.sup.2/g) to the liquid resulting from dilution and dispersing
silica with the use of an ultrasonic homogenizer. An electronic
component and a mount structure of the electronic component
according to Example 5 were fabricated as in Example 1 except that
a water-repellent film was formed by using this dispersion liquid
as a treatment solution. The formed water-repellent film had a
thickness of approximately 5 nm.
Comparative Example 1
[0086] An electronic component and a mount structure of the
electronic component according to Comparative Example 1 were
fabricated as in Example 1 except that no water-repellent film was
formed.
Comparative Example 2
[0087] An electronic component and a mount structure of the
electronic component according to Comparative Example 2 were
fabricated as in Example 1 except that a concentration of the
non-cross-linked silicone resin in the treatment solution was set
to about 0.1 mass %.
Comparative Example 3
[0088] An electronic component and a mount structure of the
electronic component according to Comparative Example 3 were
fabricated as in Example 1 except that a water-repellent film was
formed with the use of a treatment solution obtained by diluting an
alkoxysilane-based silane coupling agent (KBM-3063 manufactured by
Shin-Etsu Chemical Co., Ltd.) with propanol to about 5 volume
%.
Comparative Example 4
[0089] An electronic component and a mount structure of the
electronic component according to Comparative Example 4 were
fabricated as in Example 1 except that a water-repellent film was
formed with the use of a treatment solution made of a
fluorine-based silane coupling agent.
[0090] A measurement method and an evaluation method in the present
Experimental Example will be described below.
Method of Measuring Thickness
[0091] A method of measuring a thickness of a water-repellent film
in a sample electronic component fabricated in each of Examples 1
to 5 and Comparative Examples 1 to 4 was performed as follows.
Initially, in a main surface opposite to a mount surface of the
electronic component (an LW surface), a cross-section of a
water-repellent film was partially exposed by using a focused ion
beam (FIB) emitted under a condition of an angle of about
45.degree. with respect to a vertical direction such that a process
range extending, starting from a central position in the width
direction W and a central position in the length direction L (a
portion circled in FIG. 2) of one external electrode along the
length direction L formed on the LW surface, by about 30 .mu.m
along the length direction L toward the other external electrode
and by about 30 .mu.m along the thickness direction T is obtained.
Then, a water-repellent film at the central position in the length
direction L of the water-repellent film which was exposed at the
exposed cross-section was projected with SEM and a thickness
thereof was measured. The measurement value was adopted as a
thickness of the water-repellent film.
Measurement of Angle of Contact
[0092] Tables 1 and 2 show results of a measurement of an angle of
contact of water of about 25.degree. C. with the water-repellent
film in the sample electronic component fabricated in each of
Examples 1 to 5 and Comparative Examples 2 to 4. In Comparative
Example 1 where no water-repellent film was formed, an angle of
contact of water of about 25.degree. C. with a main surface of the
electronic component main body was measured. Table 1 shows results,
with samples having achieved a target value being extracted from
among a plurality of samples which had been fabricated to aim at
each angle of contact shown in Table 1.
Evaluation of Ion Migration
[0093] A cycle test for condensation in the mount structure of the
electronic component in each of Examples 1 to 5 and Comparative
Examples 1 to 4 was conducted under the following conditions. The
fabricated mount structure of the electronic component was held for
about 1 hour in an environment at a temperature as low as about
-30.degree. C. Thereafter, the mount structure was held for about 1
hour in an environment at a high temperature of about 25.degree. C.
and a high humidity of about 90%. Finally, the mount structure of
the electronic component was dried while about 1.5 hour elapsed to
lower humidity to about 50% at a temperature of about 25.degree. C.
This process was defined as 1 cycle and 48 cycles were carried
out.
[0094] Thereafter, a portion of the second main surface was
observed as being magnified by 100 times with the use of a
microscope. Consequently, a case in which the presence of a white
or black product was observed on the second main surface was
determined as an occurrence of ion migration or "bad". A case in
which a white or black product was not observed on the second main
surface was evaluated as an absence of an occurrence of ion
migration or "good". Tables 1 and 2 show a ratio of the number of
samples determined as "bad" to the total number of samples ((the
number of samples determined as "bad")/(the total number of
samples)). Here, the number of tested samples was set to n=18.
[0095] Sn, Ni, or Cu could be detected as a result of analysis of a
product with a wavelength-dispersive X-ray spectrometer (WDX).
Therefore, the observed white or black product was confirmed as a
product resulting from ion migration.
Evaluation of Mountability
[0096] Mountability of the sample mount structure of the electronic
component fabricated in each of Examples 1 to 5 and Comparative
Examples 1 to 4 was evaluated with the use of a solder wettability
tester "SAT-5100 manufactured by Rhesca Corporation" in accordance
with JIS C 60068-2-69 "Environmental testing-Part 2-69: Tests-Test
Te: Solderability testing of electronic components for surface
mounting devices (SMD) by the wetting balance method."
[0097] Specifically, the electronic component was mounted on a
glass epoxy substrate with unleaded solder (96.5 Sn-3 Ag-0.5 Cu). A
solder pellet manufactured by Rhesca Corporation was used as the
solder. A solution of about 25% of solid rosin (pine resin) and
about 75% of isopropyl alcohol (IPA) (a weight ratio) was used as a
flux. A temperature for the test was set to about 245.degree. C.
Based on the obtained test results, a sample of which zero crossing
time (representing a time at which wetting starts) was within about
1.5 second was evaluated as "good" and a sample of which zero
crossing time was equal to or greater than about 1.5 second was
evaluated as "bad". Table 1 shows a ratio of the number of samples
determined as "bad" to the total number of samples ((the number of
samples determined as "bad")/(the total number of samples)). Here,
the number of tested samples was set to n=10.
TABLE-US-00001 TABLE 1 Static Contact Angle Between Ratio of
Water-Repellent Occurrence Ratio of Film and of Ion Defective Water
at 25.degree. C. (.degree.) Migration Mountability Comparative 82
18/18 0/10 Example 1 Comparative 95 9/18 0/10 Example 2 Example 1
100 2/18 0/10 Example 2 110 0/18 0/10 Example 3 120 1/18 0/10
Example 4 130 1/18 0/10 Example 5 160 0/18 0/10
TABLE-US-00002 TABLE 2 Static Contact Angle Between Ratio of
Water-Repellent Occurrence Ratio of Film and of Ion Defective Water
at 25.degree. C. (.degree.) Migration Mountability Comparative 93
16/18 10/10 Example 3 Comparative 160 8/18 10/10 Example 4
[0098] As shown in Table 1, a ratio of the occurrence of ion
migration drastically changed, with an angle of contact of about
100.degree. of water of about 25.degree. C. with the
water-repellent film defining a threshold. It could be confirmed
from the results in the present Experimental Example that the
occurrence of ion migration could suitably be reduced or prevented
by setting an angle of contact of water of about 25.degree. C. with
the water-repellent film to about 100.degree. or greater.
[0099] As shown in Table 2, when the water-repellent film was
formed with the silane coupling agent, the occurrence of ion
migration could not be sufficiently reduced or prevented even
though an angle of contact of water of about 25.degree. C. with the
water-repellent film was set to about 100.degree. or greater. It
was discovered therefrom that the formation of a water-repellent
film, of which the angle of contact of water of about 25.degree. C.
with the water-repellent film is about 100.degree. or greater, with
the use of a non-cross-linked silicone resin was important for
effective reduction or preventions of the occurrence of ion
migration. In addition, as shown in Table 2, mountability was not
satisfactory when a water-repellent film was formed of a
cross-linked silane coupling agent.
[0100] It was confirmed from the results described above that, by
forming a water-repellent film, of which the angle of contact with
water of about 25.degree. C. was not less than about 100.degree.
and not greater than about 160.degree., with the use of a
non-cross-linked silicone resin, the occurrence of ion migration
could effectively be reduced or prevented and excellent
mountability could be obtained.
[0101] An electronic component, a method of manufacturing the same,
and a mount structure of the electronic component according to a
second preferred embodiment of the present invention will be
described below. Since the electronic component, the method of
manufacturing the same, and the mount structure of the electronic
component according to the present preferred embodiment are
different from the electronic component, the method of
manufacturing the same, and the mount structure of the electronic
component according to the first preferred embodiment in that the
occurrence of ion migration is reduced or prevented and good
mountability with solder is achieved by defining a weight-average
molecular weight of a non-cross-linked silicone resin contained in
a water-repellent film, description of features the same as or
similar to those in the first preferred embodiment will not be
repeated.
Second Preferred Embodiment
[0102] In the second preferred embodiment of the present invention,
a water-repellent film is provided such that an angle of contact (a
static angle of contact) of water of about 25.degree. C. with the
water-repellent film is not less than about 90.degree., for
example. A non-cross-linked silicone resin contained in the
water-repellent film has a weight-average molecular weight not less
than about 7400 g/mol and not more than about 8000 g/mol, for
example.
[0103] An Experimental Example 2 in which the influence of a
weight-average molecular weight of a non-cross-linked silicone
resin on each of whether or not ion migration in an electronic
component occurs and mountability of an electronic component will
be described below.
Experimental Example 2
[0104] In Experimental Example 2, six types of electronic
components and mount structures of the electronic components in
Example 6 to Example 8 and Comparative Example 5 to Comparative
Example 7 were fabricated. A stacked ceramic capacitor was
fabricated as the electronic component.
Example 6
[0105] An electronic component and a mount structure of the
electronic component according to Example 6 substantially the same
as the electronic component according to the second preferred
embodiment were fabricated under the conditions described below. A
dimension (a design value) of the electronic component was set to
about 1.6 mm in length, about 0.8 mm in width, and about 0.8 mm in
thickness. A ceramic portion was composed of BaTiO.sub.3. The first
and second internal electrodes were composed of Ni. The first
electrode layer was made of a fired electrode layer containing Cu.
The second electrode layer was made of a Ni plated layer. The third
electrode layer was made of a Sn plated layer. A distance along the
length direction between the first external electrode and the
second external electrode in each of the first and second main
surfaces was set to about 0.8 mm. A liquid obtained by diluting a
silicone polymer dispersion liquid (SD-8002 DISPERSION manufactured
by Dow Corning Toray) containing a non-cross-linked silicone resin
having a weight-average molecular weight not less than about 7400
g/mol and not more than about 8000 g/mol such that a concentration
of the non-cross-linked silicone resin was about 1 mass % was used
as the treatment solution. For forming a water-repellent film,
after the electronic component main body 10 including the first and
second external electrodes was immersed in the treatment solution
for about 5 minutes, the electronic component main body was taken
out of the treatment solution and dried at about 150.degree. C. for
about 30 minutes. Consequently, a water-repellent film having a
thickness of approximately 5 nm was formed. The mount structure of
the electronic component was fabricated by solder-mounting the
electronic component on a substrate with the use of solder (96.5
Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-V manufactured by Senju Metal
Industry Co., Ltd.).
Example 7
[0106] An electronic component and a mount structure of the
electronic component according to Example 7 were fabricated as in
Example 6 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 5 mass %.
The water-repellent film had a thickness of approximately 50
nm.
Example 8
[0107] An electronic component and a mount structure of the
electronic component according to Example 8 were fabricated as in
Example 6 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 60 mass
%. The formed water-repellent film had a thickness of approximately
250 nm.
Comparative Example 5
[0108] An electronic component and a mount structure of the
electronic component according to Comparative Example 5 were
fabricated as in Example 6 except that no water-repellent film was
formed.
Comparative Example 6
[0109] An electronic component and a mount structure of the
electronic component according to Comparative Example 6 were
fabricated as in Example 6 except that a water-repellent film was
formed with the use of a treatment solution obtained by diluting an
alkoxysilane-based silane coupling agent (KBM-3063 manufactured by
Shin-Etsu Chemical Co., Ltd.) with propanol to 5 volume %.
Comparative Example 7
[0110] An electronic component and a mount structure of the
electronic component according to Comparative Example 7 were
fabricated as in Example 6 except that a water-repellent film was
formed with the use of a silicone-based cross-linked polymer
coating liquid (KR-400 manufactured by Shin-Etsu Chemical Co.,
Ltd.). The formed water-repellent film had a thickness of
approximately 5 .mu.m.
[0111] A measurement method and an evaluation method in the present
Experimental Example will be described below. Ion migration and
mountability were evaluated as in Experimental Example 1.
Measurement of Weight-Average Molecular Weight
[0112] In each of Examples 6 to 8 and Comparative Example 6, three
thousand samples were created. Three thousand samples were immersed
in isoparaffin to thereby dissolve the water-repellent film in
isoparaffin. To 10 g of tetrahydrofuran, 0.02 g of the isoparaffin
solution in which the water-repellent film had been dissolved was
added. Tetrahydrofuran to which the isoparaffin solution had been
added was analyzed with a high performance liquid chromatograph
(HPLC manufactured by Shimadzu Corporation) with a measurement mode
being set to size exclusion chromatography (SEC), and a
weight-average molecular weight was measured based on a result
thereof.
[0113] Table 3 shows results of measurements of a weight-average
molecular weight of the non-cross-linked silicone resin in the
sample electronic component fabricated in each of Example 6 to
Example 8 and Comparative Examples 6 and 7. In the sample
fabricated in Comparative Example 7, the water-repellent film was
not dissolved in isoparaffin. Therefore, a weight-average molecular
weight of the water-repellent film of the sample electronic
component according to Comparative Example 7 could not be
measured.
TABLE-US-00003 TABLE 3 Weight-Average Ratio of Molecular Weight of
Occurrence Ratio of Non-Cross-Linked of Ion Defective Silicone
Resin (g/mol) Migration Mountability Example 6 7400 0/18 0/10
Example 7 8000 0/18 0/10 Example 8 7800 0/18 0/10 Comparative --
18/18 0/10 Example 5 Comparative 260 16/18 0/10 Example 6
Comparative -- 0/18 10/10 Example 7
[0114] As shown in Table 3, it was confirmed that, when a
weight-average molecular weight of the non-cross-linked silicone
resin was within a range not less than about 7400 g/mol and not
more than about 8000 g/mol, the occurrence of ion migration was not
observed, and the occurrence of ion migration was effectively
reduced or prevented and excellent mountability was obtained. In
the electronic component according to Comparative Example 7, the
occurrence of ion migration was not observed, however, mountability
was not satisfactory.
[0115] An electronic component, a method of manufacturing the same,
and a mount structure of the electronic component according to a
third preferred embodiment of the present invention will be
described below. The electronic component, the method of
manufacturing the same, and the mount structure of the electronic
component according to the present preferred embodiment achieve
good mountability with solder while the occurrence of ion migration
is reduced or prevented, by providing a water-repellent film
soluble in a solvent contained in a solder flux or an organic
solvent. Description of features the same as or similar to those in
the first preferred embodiment or the second preferred embodiment
will not be repeated.
Third Preferred Embodiment
[0116] In the third preferred embodiment of the present invention,
a water-repellent film is preferably composed, for example, of a
resin. A water-repellent film is preferably composed, for example,
of a silicone resin or a fluorine-based resin. A resin included in
a water-repellent film is preferably a non-cross-linked resin. A
non-cross-linked resin does not produce cross-linking reaction.
With a non-cross-linked resin, a molecular weight of a resin is
readily be controllable and a molecular weight is prevented from
undesirably increasing. Therefore, a water-repellent film hardened
by drying a non-cross-linked resin is soluble in an organic solvent
or a solvent contained in a solder flux. A water-repellent film may
be composed, for example, only of resin, or may be composed of a
resin composition containing a filler. A water-repellent film is
formed such that an angle of contact (a static angle of contact) of
water of about 25.degree. C. with the water-repellent film is not
less than about 100.degree..
[0117] A solder member forming solder included in the mount
structure of the electronic component includes solder and a solder
flux. The solder flux contains a solvent. The solvent contained in
the solder flux may be an aqueous solvent or an organic solvent. A
preferred organic solvent is exemplified by an organic solvent
including at least one selected from the group consisting of an
ether-based organic solvent, an alcohol-based organic solvent, a
hydrocarbon-based organic solvent, a ketone-based organic solvent,
an ester-based organic solvent, and a glycol-ether-based organic
solvent. A solubility parameter (an SP value) of the solvent
contained in the solder flux is preferably, for example, from about
7.0 to about 14.0.
[0118] In the present preferred embodiment, a water-repellent resin
soluble in a solvent contained in a solder flux is used for a
water-repellent film. By using a solvent closer in solubility
parameter (SP value) to the solvent contained in the solder flux as
a solvent for diluting a resin for forming the water-repellent
film, a highly homogenous treatment agent is provided. Therefore, a
water-repellent film high in homogeneity is manufactured. The
water-repellent film is soluble in the solvent contained in the
solder flux during mounting of an electronic component. Therefore,
when an electronic component is mounted, the water-repellent film
located on a surface of a portion of the first and second external
electrodes joined by solder is removed. Thus, no water-repellent
film is provided at an interface between the first and second
external electrodes and the solder in the mount structure of the
electronic component. That is, no water-repellent film is provided
at a junction between the electronic component and the mount
substrate. Accordingly, direct contact between a solder melt and
the first and second external electrodes is likely to occur. Thus,
the first and second external electrodes and solder are suitably
joined to each other. Therefore, the electronic component has
excellent mount ability.
[0119] An Experimental Example 3 in which an influence of
solubility of a water-repellent film in a solvent contained in a
solder flux on each of whether or not ion migration in an
electronic component occurs and mountability of an electronic
component will be described below.
Experimental Example 3
[0120] In Experimental Example 3, seven types of electronic
components and mount structures of the electronic components in
Example 9 to Example 12 and Comparative Example 8 to Comparative
Example 10 were fabricated. A stacked ceramic capacitor was
fabricated as the electronic component.
Example 9
[0121] An electronic component and a mount structure of the
electronic component according to Example 9 substantially the same
as the electronic component according to the third preferred
embodiment were fabricated under the conditions below. A dimension
(a design value) of the electronic component was set to about 1.6
mm in length, about 0.8 mm in width, and about 0.8 mm in thickness.
A ceramic portion was composed of BaTiO.sub.3. The first and second
internal electrodes were composed of Ni. The first electrode layer
was made of a fired electrode layer containing Cu. The second
electrode layer was made of a Ni plated layer. The third electrode
layer was made of a Sn plated layer. A distance along the length
direction between the first external electrode and the second
external electrode in each of the first and second main surfaces
was set to about 0.8 mm. A liquid obtained by diluting a silicone
polymer dispersion liquid containing a non-cross-linked silicone
resin (SD-8002 DISPERSION manufactured by Dow Corning Toray) such
that a concentration of the non-cross-linked silicone resin was
about 1 mass % was used as the treatment solution. For forming a
water-repellent film, after the electronic component main body 10
including the first and second external electrodes was immersed in
the treatment solution for about 5 minutes, the electronic
component main body was taken out of the treatment solution and
dried at about 150.degree. C. for about 30 minutes. Consequently, a
water-repellent film having a thickness of several nm was formed.
The mount structure of the electronic component was fabricated by
solder-mounting the electronic component on a substrate with the
use of solder (96.5 Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-V
manufactured by Senju Metal Industry Co., Ltd.).
Example 10
[0122] An electronic component and a mount structure of the
electronic component according to Example 10 were fabricated as in
Example 9 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 5 mass
%.
Example 11
[0123] An electronic component and a mount structure of the
electronic component according to Example 11 were fabricated as in
Example 9 except that a concentration of the non-cross-linked
silicone resin in the treatment solution was set to about 60 mass
%.
Example 12
[0124] An electronic component and a mount structure of the
electronic component according to Example 12 were fabricated as in
Example 9 except that a water-repellent film was formed of a
fluorine-based non-cross-linked resin coating liquid (WOP-019XPC
manufactured by Noda Screen Co., Ltd.). The formed water-repellent
film had a thickness of several nm.
Comparative Example 8
[0125] An electronic component and a mount structure of the
electronic component according to Comparative Example 8 were
fabricated as in Example 9 except that no water-repellent film was
formed.
Comparative Example 9
[0126] An electronic component and a mount structure of the
electronic component according to Comparative Example 9 were
fabricated as in Example 9 except that a water-repellent film was
formed using a treatment solution obtained by diluting an
alkoxysilane-based silane coupling agent (KBM-3063 manufactured by
Shin-Etsu Chemical Co., Ltd.) with propanol to about 5 volume
%.
Comparative Example 10
[0127] An electronic component and a mount structure of the
electronic component according to Comparative Example 10 were
fabricated as in Example 9 except that a water-repellent film was
formed using a silicone-based cross-linked polymer coating liquid
(KR-400 manufactured by Shin-Etsu Chemical Co., Ltd.). The formed
water-repellent film had a thickness of approximately 5 .mu.m.
[0128] A measurement method and an evaluation method in the present
Experimental Example will be described below. Ion migration and
mountability were evaluated as in Experimental Example 1.
Evaluation of Solubility in Solvent Contained in Solder Flux
[0129] Whether or not the water-repellent film in the electronic
component fabricated in each of Examples 9 to 12 and Comparative
Examples 8 to 10 was dissolved in the solvent contained in the
solder flux was evaluated. A case in which the fabricated
electronic component was immersed in a solder flux containing about
25% of rosin and about 75% of propanol (flux F manufactured by
Sasaki Chemical Co., Ltd.) and the water-repellent film was
dissolved and removed was defined as "good" and a case in which no
change was observed in the water-repellent film was defined as
"bad". Here, the number of tested samples was set to n=10. Table 4
shows results of the present experiment.
TABLE-US-00004 TABLE 4 Solubility of Water-Repellent Ratio of Film
in Solvent Occurrence Ratio of Contained in of Ion Defective Solder
Flux Migration Mountability Example 9 good 0/18 0/10 Example 10
good 0/18 0/10 Example 11 good 0/18 0/10 Example 12 good 0/18 0/10
Comparative -- 18/18 0/10 Example 8 Comparative bad 16/18 0/10
Example 9 Comparative Example 10 bad 0/18 10/10
[0130] As shown in Table 4, it was confirmed that the
water-repellent film containing a non-cross-linked silicone resin
was dissolved in the solvent contained in the solder flux. It was
confirmed that, in the electronic component including the
water-repellent film dissolved in the solvent contained in the
solder flux, the occurrence of ion migration was not observed, and
the occurrence of ion migration could effectively be reduced or
prevented and excellent mountability was obtained. In the
electronic component according to Comparative Example 9,
mountability was satisfactory, however, the occurrence of ion
migration was observed. In the electronic component according to
Comparative Example 10, the occurrence of ion migration was not
observed, however, mountability was not satisfactory.
[0131] An electronic component, a method of manufacturing the same,
and a mount structure of the electronic component according to a
fourth preferred embodiment of the present invention will be
described below. The electronic component, the method of
manufacturing the same, and the mount structure of the electronic
component according to the present preferred embodiment achieve
good mountability with solder while the occurrence of ion migration
is effectively reduced or prevented, by providing a water-repellent
film defined by a silicone resin film having a thickness not
greater than about 200 nm. Description of features the same as in
the first to third preferred embodiments will not be repeated.
Fourth Preferred Embodiment
[0132] An electronic component according to the fourth preferred
embodiment of the present invention includes a silicone resin film
as a water-repellent film. The silicone resin film should only be a
film containing a silicone resin. The silicone resin may be formed,
for example, only of a silicone resin or of a silicone resin
composition containing a filler.
[0133] When the inventors of the present invention actually
fabricated an electronic component provided with a silicone resin
film, in some cases, disadvantageously, electronic components
adhered to each other when a plurality of electronic components
were in contact with each other, and an electronic component was
not detached from a suction and attraction mechanism when the
electronic component was transported with the use of the suction
and attraction mechanism. The inventors of the present invention
discovered as a result of further dedicated studies that, by
setting a thickness of a silicone resin film to about 200 nm or
less, the adhesiveness of an electronic component was reduced, the
problems described above were solved, and the mountability of the
electronic component was improved.
[0134] In the electronic component according to the present
preferred embodiment, a thickness of a silicone resin film
preferably is set to about 200 nm, for example. Therefore, an
adhesion force of an electronic component to another member is low.
Accordingly, for example, adhesion of a plurality of electronic
components to each other or difficulty in detachment thereof from a
suction and attraction mechanism are effectively prevented. In
order to further reduce the adhesion force of an electronic
component to another member, a silicone resin film has a thickness
preferably not greater than about 100 nm, for example. When the
thickness of a silicone resin film is too small, the occurrence of
ion migration may not be sufficiently reduced or prevented.
Therefore, the silicone resin film has a thickness preferably not
less than about 1 nm. A thickness of a silicone resin film can be
controlled, for example, by appropriately adjusting a concentration
of a silicone resin in a treatment agent.
[0135] A silicone resin film can be formed, for example, in the
following manner. Initially, a treatment agent is prepared by
diluting a silicone resin by adding a solvent such as a
paraffin-based solvent thereto. In the treatment agent, a
concentration of the silicone resin can be, for example, from about
0.01 mass % to about 10 mass %. Then, an electronic component main
body including the first and second external electrodes provided
thereon is immersed in the treatment agent, for example, for
approximately 1 to 10 minutes. Thereafter, a silicone resin film
can be formed, for example, by drying the electronic component main
body in a heated atmosphere from about 100.degree. C. to about
200.degree. C. for approximately 10 to 60 minutes, for example.
[0136] An Experimental Example 4 in which the influence of a
thickness of a silicone resin film on each of whether or not ion
migration in an electronic component occurs and adhesive force of a
water-repellent film (mountability of an electronic component) will
be described below.
Experimental Example 4
[0137] In Experimental Example 4, six types of electronic
components and mount structures of the electronic components in
Example 13 to Example 15 and Comparative Example 11 to Comparative
Example 13 were fabricated. A stacked ceramic capacitor was
fabricated as the electronic component.
Example 13
[0138] An electronic component and a mount structure of the
electronic component according to Example 13 that are the same or
substantially the same as the electronic component according to the
fourth preferred embodiment were fabricated under the conditions
below. A dimension (a design value) of the electronic component was
set to about 1.6 mm in length, about 0.8 mm in width, and about 0.8
mm in thickness. A ceramic portion was composed of BaTiO.sub.3. The
first and second internal electrodes were composed of Ni. The first
electrode layer was made of a fired electrode layer containing Cu.
The second electrode layer was made of a Ni plated layer. The third
electrode layer was made of a Sn plated layer. A distance along the
length direction between the first external electrode and the
second external electrode in each of the first and second main
surfaces was set to about 0.8 mm. A concentration of a silicone
resin in a treatment solution was set to about 0.008 mass %. For
forming the water-repellent film 20, immersion of the electronic
component main body including the first and second external
electrodes provided thereon in the treatment solution and drying
thereof were repeated seven times. A formed water-repellent film
had a thickness of about 60 nm. The mount structure of the
electronic component was fabricated by solder-mounting the
electronic component on a substrate with the use of solder (96.5
Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-V manufactured by Senju Metal
Industry Co., Ltd.).
Example 14
[0139] An electronic component and a mount structure of the
electronic component according to Example 14 were fabricated as in
Example 13 except that a concentration of a silicone resin in the
treatment solution was set to about 0.01 mass %. The
water-repellent film had a thickness of about 90 nm.
Example 15
[0140] An electronic component and a mount structure of the
electronic component according to Example 15 were fabricated as in
Example 13 except that a concentration of a silicone resin in the
treatment solution was set to about 0.013 mass %. The
water-repellent film had a thickness of about 100 nm.
Comparative Example 11
[0141] An electronic component and a mount structure of the
electronic component according to Comparative Example 11 were
fabricated as in Example 13 except that a concentration of a
silicone resin in the treatment solution was set to about 0.042
mass %. The water-repellent film had a thickness of about 300
nm.
Comparative Example 12
[0142] An electronic component and a mount structure of the
electronic component according to Comparative Example 12 were
fabricated as in Example 13 except that a concentration of a
silicone resin in the treatment solution was set to about 0.057
mass %. The water-repellent film had a thickness of about 500
nm.
Comparative Example 13
[0143] An electronic component and a mount structure of the
electronic component according to Comparative Example 13 were
fabricated as in Example 13 except that a water-repellent film was
formed with the use of a treatment solution obtained by diluting an
alkoxysilane-based silane coupling agent (KBM-3063 manufactured by
Shin-Etsu Chemical Co., Ltd.) with propanol to about 10 volume
%.
[0144] A measurement method and an evaluation method in the present
Experimental Example will be described below. A method of measuring
a thickness and evaluation of ion migration were the same as in
Experimental Example 1.
Evaluation of Adhesive Force of Water-Repellent Film
[0145] Two electronic components fabricated in each of Examples 13
to 15 and Comparative Examples 11 to 13 were sandwiched such that
first main surfaces thereof were opposed to each other, a pressure
of about 5N was applied thereto in a direction of a thickness
thereof, and thereafter, the two electronic components were dropped
onto a base from a height of about 2 cm above the base. A case in
which the two electronic components were separated as a result of
dropping was evaluated as low in adhesive force or "good". A case
in which the two electronic components were not separated after
dropping was evaluated as high in adhesive force or "bad". This
evaluation of adhesive force was conducted 100 times for each of
Examples 13 to 15 and Comparative Examples 11 to 13. Table 5 shows
the number of times of evaluation as "bad" in evaluation of
adhesive force which was conducted 100 times.
TABLE-US-00005 TABLE 5 Ratio of Defective Thickness Ratio of
Adhesive Force of of Silicone Occurrence Water-Repellent Film Resin
of Ion (Ratio of Defective Film (nm) Migration Mountability)
Example 13 60 0/18 0/100 Example 14 90 0/18 0/100 Example 15 100
0/18 1/100 Comparative 300 0/18 15/100 Example 11 Comparative 500
0/18 60/100 Example 12 Comparative 100 16/18 0/100 Example 13
[0146] As shown in Table 5, it was confirmed that, within a range
of a thickness of a silicone resin film not greater than about 100
nm, the occurrence of ion migration was effectively reduced or
prevented, the adhesive force of a water-repellent film was low,
and excellent mountability was obtained. In the electronic
components according to Comparative Examples 11 and 12, the
occurrence of ion migration was not observed, however, the adhesive
force of a water-repellent film was high and the mountability was
not satisfactory. In the electronic component according to
Comparative Example 13, the mountability was satisfactory, however,
the occurrence of ion migration was observed.
[0147] In each of the first to fourth preferred embodiments and
Examples 1 to 15 above, features can be combined with each other as
appropriate.
[0148] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *