U.S. patent application number 12/298633 was filed with the patent office on 2009-09-24 for adhesive tape and solar cell module using the same.
This patent application is currently assigned to HITACHI CHEMICAL COMPANY, LTD.. Invention is credited to Naoki Fukushima, Takahiro Fukutomi, Takehiro Shimizu.
Application Number | 20090235972 12/298633 |
Document ID | / |
Family ID | 38655429 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090235972 |
Kind Code |
A1 |
Fukushima; Naoki ; et
al. |
September 24, 2009 |
ADHESIVE TAPE AND SOLAR CELL MODULE USING THE SAME
Abstract
The present invention provides an adhesive tape 10 for
electrically connecting a plurality of solar battery cells, which
adhesive tape has a metal foil 1 and an adhesive layer 2 composed
of an adhesive provided on at least one surface of the metal foil
1, and a solar battery module using the adhesive tape. The adhesive
tape of the present invention can suppress the decrease in the
product yield and can improve the connection workability of solar
battery cells.
Inventors: |
Fukushima; Naoki; (Ibaraki,
JP) ; Shimizu; Takehiro; (Tokyo, JP) ;
Fukutomi; Takahiro; (Ibaraki, JP) |
Correspondence
Address: |
GRIFFIN & SZIPL, PC
SUITE PH-1, 2300 NINTH STREET, SOUTH
ARLINGTON
VA
22204
US
|
Assignee: |
HITACHI CHEMICAL COMPANY,
LTD.
Tokyo
JP
|
Family ID: |
38655429 |
Appl. No.: |
12/298633 |
Filed: |
April 27, 2007 |
PCT Filed: |
April 27, 2007 |
PCT NO: |
PCT/JP2007/058818 |
371 Date: |
February 9, 2009 |
Current U.S.
Class: |
136/244 ;
428/344 |
Current CPC
Class: |
C09J 9/00 20130101; C09J
11/04 20130101; C09J 163/00 20130101; H01B 1/22 20130101; Y02E
10/50 20130101; H01L 31/022425 20130101; Y10T 428/2804 20150115;
C09J 9/02 20130101; H01L 31/0512 20130101 |
Class at
Publication: |
136/244 ;
428/344 |
International
Class: |
H01L 31/042 20060101
H01L031/042; B32B 7/12 20060101 B32B007/12; C09J 7/02 20060101
C09J007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2006 |
JP |
2006-121930 |
Claims
1-6. (canceled)
7. An adhesive tape for electrically connecting a plurality of
solar battery cells, comprising: a metal foil; and (an) adhesive
layer(s) comprising an adhesive provided on at least one surface of
the metal foil.
8. The adhesive tape according to claim 7, wherein the adhesive
comprises a conductive particle.
9. The adhesive tape according to claim 7, wherein the adhesive
further comprises a thermosetting resin.
10. The adhesive tape according to claim 7, wherein the metal foil
is a copper foil or an aluminum foil.
11. The adhesive tape according to claim 7, wherein the adhesive
layers are provided on both surfaces of the metal foil.
12. A solar battery module comprising a plurality of solar battery
cells, wherein the plurality of solar battery cells are
electrically connected through a connection member, and wherein the
connection member is formed using the adhesive tape according to
claim 7.
13. The adhesive tape according to claim 8, wherein the adhesive
further comprises a thermosetting resin.
14. The adhesive tape according to claim 8, wherein the metal foil
is a copper foil or an aluminum foil.
15. The adhesive tape according to claim 8, wherein the adhesive
layers are provided on both surfaces of the metal foil.
16. A solar battery module comprising a plurality of solar battery
cells, wherein the plurality of solar battery cells are
electrically connected through a connection member, and wherein the
connection member is formed using the adhesive tape according to
claim 8.
Description
TECHNICAL FIELD
[0001] The present invention relates to an adhesive tape for
electrically connecting a plurality of solar battery cells and a
solar battery module using the same.
BACKGROUND ART
[0002] Solar battery modules are solar photovoltaic power
generation apparatuses to directly convert light energy to an
electric energy. The solar battery modules attract attention as a
clean energy in resent years, and their market is anticipated to
rapidly expand from now. Such solar battery modules generally have
a structure in which a plurality of solar battery cells are
electrically connected.
[0003] As methods of electrically connecting solar battery cells,
methods using solders are conventionally known (for example, see
Patent Documents 1 and 2). Solders are broadly used because they
are excellent in connection reliability such as conductivity and
fixing strength, and inexpensive and versatile.
[0004] On the other hand, as methods of electrically connecting
solar battery cells without using solders, methods using a
conductive adhesive are also disclosed (for example, see Patent
Documents 3, 4, 5 and 6).
Patent Document 1: Japanese Patent Laid-Open No. 2004-204256
Patent Document 2: Japanese Patent Laid-Open No. 2005-050780
Patent Document 3: Japanese Patent Laid-Open No. 2000-286436
Patent Document 4: Japanese Patent Laid-Open No. 2001-357897
Patent Document 5: Japanese Patent Laid-Open No. 7-147424
Patent Document 6: Japanese Patent Laid-Open No. 2005-101519
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] However, in connection methods using solders, since a high
temperature (the fusing temperature of solders is usually 230 to
260.degree. C.) is involved on connection, volume shrinkage and the
like are generated in adherends (solar battery cells), causing
characteristic degradation of solar batteries in some cases. There
is therefore a problem of the decreased product yield.
[0006] Particularly in solar battery modules, the price of solar
battery cells accounts for nearly 40% of the price of a solar
battery module and rapid expansion of the solar battery market is
anticipated, so the thickness reduction of solar battery cells will
inevitably be demanded in future. Advancement of the thickness
reduction of solar battery cells causes warping and cracking in the
solar battery cells due to a high temperature involved on
connection, and also raises a problem of a remarkably decreased
product yield.
[0007] Further, in connection methods using a solder, it is
difficult to control the thickness of the connection interface with
an adherend because of solder characteristics, and it is difficult
to provide a sufficient dimensional precision on packaging. The
case where a sufficient dimensional precision is not provided leads
to a decrease in the product yield on the packaging process.
[0008] On the other hand, methods using a conductive adhesive are
suitable for the electric connection of thickness-reduced solar
battery cells because the connection can be performed at a lower
temperature than methods using a solder. However, conventional
methods using a conductive adhesive necessitate a process to
transfer the conductive adhesive to an adherend, and have a problem
of a low connection workability of solar battery cells.
[0009] Then, the present invention has been achieved in
consideration of the above-mentioned situations, and has an object
to provide an adhesive tape which can suppress the decrease in the
product yield and can improve the connection workability of solar
battery cells, and a solar battery module using the adhesive
tape.
Means for Solving the Problems
[0010] The present invention provides an adhesive tape for
electrically connecting a plurality of solar battery cells, which
adhesive tape has a metal foil and an adhesive layer composed of an
adhesive provided on at least one surface of the metal foil.
[0011] According to the adhesive tape of the present invention,
since an adhesive layer is provided on at least one surface of a
metal foil, when solar battery cells are connected, the work of
transferring an adhesive layer on an insulating base material from
the base material to each solar battery cell can be omitted.
Further, the connection can be performed at a sufficiently lower
temperature than in cases of connecting solar battery cells using a
solder. Therefore, warping and cracking of solar battery cells on
connection can be sufficiently prevented and the yield of solar
battery modules can be sufficiently enhanced in its turn.
[0012] The adhesive preferably contains conductive particles. With
this, a plurality of solar battery cells can easily be electrically
connected.
[0013] The adhesive preferably contains further a thermosetting
resin for improving the connection reliability after the
connection.
[0014] The metal foil is preferably a copper foil or an aluminum
foil because of its excellent conductivity.
[0015] In the adhesive tape of the present invention, the adhesive
layers are preferably provided on both surfaces of a metal foil.
With this, since solar battery cells can be connected to both
surfaces of an adhesive tape, solar battery cells can easily be
connected in either of series connection and parallel
connection.
[0016] The present invention further provides a solar battery
module which has a plurality of solar battery cells, which cells
are electrically connected through a connection member, which
member is formed using the above-mentioned adhesive tape. Since
such a solar battery module uses the adhesive tape of the present
invention, the product yield can be enhanced and the connection
workability of solar battery cells can be improved. Therefore, the
cost reduction on fabricating solar battery modules can be
achieved.
EFFECT OF THE INVENTION
[0017] According to the present invention, there are provided an
adhesive tape which can suppress the decrease in the product yield
and can improve the connection workability of solar battery cells,
and a solar battery module using the adhesive tape.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an illustrative sectional view showing an
embodiment of an adhesive tape according to the present
invention.
[0019] FIG. 2 is an illustrative sectional view showing another
embodiment of an adhesive tape according to the present
invention.
[0020] FIG. 3 is a partial plan view showing an embodiment of the
solar battery module according to the present invention.
[0021] FIG. 4 is a bottom view of the solar battery module in FIG.
3.
[0022] FIG. 5 is a sectional view taken on line V-V of FIG. 3.
EXPLANATION OF SYMBOLS
[0023] 1: Metal foil, 2, 2a, 2b: adhesive layer, 3: conductive
particle, 4: insulating adhesive composition, 5a, 5b: bus
electrode, 6: power generating section, 7: finger electrode, 8:
rear surface electrode, 10, 20: adhesive tape, 100: solar battery
module, 101: solar battery cell, 102a, 102b: connection layer, 120:
connection member.
BEST MODES FOR CARRYING OUT THE INVENTION
[0024] Hereinafter, preferable embodiments of the present invention
will be described in detail by way of drawings, but the scope of
the present invention is not limited to the following embodiments.
In drawings, the same reference character is given to the same
element and duplicated description will be omitted. The positional
relationship with respect to top and bottom and left and right and
the like is based on the positional relationship shown in drawings
as long as not otherwise specified. Besides, the dimensional ratios
of the drawings are not limited to those shown in the drawings.
[0025] FIG. 1 is an illustrative sectional view showing a first
embodiment of an adhesive tape according to the present invention.
The adhesive tape 10 shown in FIG. 1 has a structure having an
adhesive layer 2 provided on one surface of a metal foil 1.
[0026] FIG. 2 is an illustrative sectional view showing a second
embodiment of an adhesive tape according to the present invention.
The adhesive tape 20 shown in FIG. 2 has a structure having
adhesive layers 2a and 2b provided on both surfaces of a metal foil
1.
[0027] The adhesive layers 2, 2a and 2b are each composed of an
adhesive containing a conductive particle 3 and an insulating
adhesive composition 4. In the first and second embodiments,
embodiments in which the adhesive layers 2, 2a and 2b contain a
conductive particle 3 are shown, but the adhesive layers 2, 2a and
2b may not contain a conductive particle 3. That is, in the case
where a metal foil 1 and an electrode of a solar battery cell
described later can directly be contacted by pressing the metal
foil 1 to the electrode of the solar battery cell though an
adhesive layer, the adhesive layers 2, 2a and 2b may not contain a
conductive particle. However, that the adhesive layers 2, 2a and 2b
contain a conductive particle 3 allows for more stably electrically
connecting solar battery cells.
[0028] The metal foil 1 includes, for example, a foil of copper,
aluminum, iron, gold, silver, nickel, palladium, chromium and
molybdenum or an alloy thereof. Above all, copper foil and aluminum
foil are preferable because of their excellent conductivity. The
thickness of such a metal foil 1 is preferably 10 to 200 .mu.m in
view of the connection reliability and the like.
[0029] The conductive particle 3 includes, for example, a gold
particle, silver particle, copper particle, nickel particle,
gold-plated nickel particle, gold/nickel-plated plastic particle,
copper-plated particle and nickel-plated particle. These conductive
particles preferably have a chestnut shape or a spherical shape in
view of the embeddability of the conductive particle in the
irregularity of an adherend surface on connection. That is, the
chestnut-shaped or sphere-shaped conductive particle is preferable
because it has a high embeddability in a complicate irregular shape
of an adherend surface and a high followability to fluctuations
such as vibration and expansion after connection.
[0030] Such a conductive particle has preferably an average
particle size of 2 to 20 .mu.m in view of securing the
conductivity. The content of the conductive particle is preferably
0.1 to 20% by volume to the whole adhesive volume. With the content
of the conductive particle of less than 0.1% by volume, the
conductive particle is likely not to sufficiently exhibit an effect
on the connection stability. By contrast, with the content of the
conductive particle exceeding 20% by volume, the formability of the
adhesive layer is likely to decrease.
[0031] The insulating adhesive composition 4 to be usable is a
thermoplastic material or a material exhibiting curability to heat
and light. The insulating adhesive composition 4 preferably
contains a thermosetting resin in view of improving the connection
reliability at a high temperature and high humidity after
connection. The thermosetting resin includes, for example, epoxy
resins, polyimide resins, unsaturated polyester resins,
polyurethane resins, bismaleimide resins, triazine-bismaleimide
resins and phenol resins. Above all, epoxy resins are preferable in
view of improving heat resistance. The epoxy resin includes
bisphenol epoxy resins derived from epichlorohydrin, and bisphenol
A, bisphenol F, bisphenol AD, and/or bisphenol AF or the like;
epoxy novolac resins derived from epichlorohydrin, and phenol
novolacs and/or cresol novolacs; naphthalene epoxy resins having a
skeleton containing a naphthalene ring; and various types of epoxy
compounds having two or more glycidyl groups in one molecule, such
as glycidylamines, glycidyl ethers, biphenyls and alicyclics. These
are used singly or as a mixture of two or more.
[0032] The content of such a thermosetting resin is preferably 10
to 80% by mass, more preferably 15 to 70% by mass, to the total
amount of the insulating adhesive composition 4. With the content
of less than 10% by mass, the fluidity and workability of the
adhesive is likely to decrease as compared with cases in the
above-mentioned range. With the content exceeding 80% by mass, the
adhesiveness of the adhesive tape is likely to decrease as compared
with cases in the above-mentioned range.
[0033] The insulating adhesive composition 4 may further contain a
curing agent for a thermosetting resin with the thermosetting
resin.
[0034] A curing agent for a thermosetting resin indicates a curing
agent to promote curing of the thermosetting resin when it is
heated together with the thermosetting resin. Specific examples
include imidazole curing agents, hydrazide curing agents, amine
curing agents, phenol curing agents, acid anhydride curing agents,
boron trifluoride-amine complexes, sulfonium salts, iodonium salts,
polyamine salts, amine imides and dicyandiamide. When an epoxy
resin is used as a thermosetting resin, among these suitably used
are imidazole curing agents, hydrazide curing agents, boron
trifluoride-amine complexes, sulfonium salts, amine imides,
polyamine salts and dicyandiamide.
[0035] The content of such a curing agent for a thermosetting resin
is preferably 2 to 10% by mass, more preferably 4 to 8% by mass, to
the total amount of the insulating adhesive composition 4. With the
content of less than 2% by mass, the adhesiveness of the adhesive
tape is likely to decrease as compared with cases in the
above-mentioned range. With the content exceeding 10% by mass, the
stability when the adhesive tape is preserved is likely to decrease
as compared with cases in the above-mentioned range.
[0036] The adhesive layers 2, 2a and 2b are preferably film-shaped
in view of the layer thickness precision and the pressure
distribution on pressure bonding. In this case, the insulating
adhesive composition 4 constituting the adhesive layers 2, 2a and
2b further contains a film forming material other than the
above-mentioned thermosetting resin and curing agent for the
thermosetting resin.
[0037] The film forming material is preferably a thermoplastic
polymer such as a phenoxy resin, a polyester resin and a polyamide
resin, more preferably a phenoxy resin, in view of the better film
formability. The weight-average molecular weight of these
film-formable polymers is preferably 10,000 to 10,000,000 in view
of the fluidity of the adhesive film. With the weight-average
molecular weight of the film-formable polymer of less than 10,000,
the formability of the adhesive layer 2 is likely to decrease as
compared with cases in the above-mentioned range. With the
weight-average molecular weight of the film-formable polymer
exceeding 10,000,000, the stress relaxation effect and the
workability on curing of the adhesive layer are likely to decrease
as compared with cases in the above-mentioned range.
[0038] The content of such a film-formable polymer is preferably 2
to 80% by mass, more preferably 5 to 70% by mass, to the total
amount of the insulating adhesive composition 4. With the content
of the film-formable polymer of less than 2% by mass, the stress
relaxation effect and the adhesiveness improvement effect on curing
are likely to decrease and with the content exceeding 80% by mass,
the fluidity and the workability of the adhesive layer are likely
to decrease as compared with cases in the above-mentioned
range.
[0039] The insulating adhesive composition 4, as required, may
further contain additives such as a coupling agent, a dispersant
and a chelate material.
[0040] A coupling agent is used for improving the adhesiveness and
wettability with an adherend. Specific examples thereof include
silane coupling agents and titanate coupling agents. A dispersant
is used for improving the dispersibility of the conductive particle
3. Specific examples thereof include calcium phosphate and calcium
carbonate. A chelate material is used for suppressing metal
migration and the like of silver, copper and the like. Specific
examples thereof include inorganic ion exchangers.
[0041] When these additives are used, the content is preferably 0.1
to 10% by mass, more preferably 0.2 to 8% by mass, to the total
amount of the insulating adhesive composition 4. With the content
of less than 0.1% by mass, an effect of containing the additive is
small as compared with cases in above-mentioned range. With the
content exceeding 10% by mass, the stability when the adhesive tape
is preserved is likely to decrease as compared with cases in the
above-mentioned range.
[0042] The insulating adhesive composition 4 may contain a
thermoplastic resin, a radically polymerizable compound and a
radical polymerization initiator.
[0043] The thermoplastic resin to be usable is polyamides, phenoxy
resins, poly(meth)acrylates, polyimides, polyurethanes, polyesters
and polyvinylbutyrals. These resins may be used, as required,
singly or as a mixture of two or more. The common weight-average
molecular weight of these thermoplastic resins is 5,000 to
150,000.
[0044] The radically polymerizable compound to be usable is not
especially limited, and includes well-known compounds as long as
they are compounds having an olefin in their molecule such as a
(meth)acryl group, a (meth)acryloyl group and a vinyl group. Above
all, radically polymerizable compounds having a (meth)acryloyl
group are preferable.
[0045] Specific examples of radically polymerizable compounds
include oligomers such as epoxy (meth)acrylate oligomers, urethane
(meth)acrylate oligomers, polyether (meth)acrylate oligomers and
polyester (meth)acrylate oligomers, and polyfunctional
(meth)acrylate compounds such as trimethylolpropane
tri(meth)acrylate, polyethylene glycol di(meth)acrylates,
polyalkylene glycol di(meth)acrylates, dicyclopentenyl
(meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, neopentyl
glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
isocyanuric acid-modified bifunctional (meth)acrylate, isocyanuric
acid-modified trifunctional (meth)acrylate,
2,2'-di(meth)acryloyloxydiethyl phosphate and
2-(meth)acryloyloxyethyl acid phosphate. These compounds may be
used, as required, singly or as a mixture of two or more.
[0046] The radically polymerizable initiators to be usable include
conventionally well-known compounds such as peroxides and azo
compounds, and specifically include cumyl peroxyneodecanoate,
1,1,3,3-tetramethylbutyl peroxyneodecanoate,
1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl
peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl
peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate,
2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexyl
peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl
peroxyneoheptanoate, t-amyl peroxy-2-ethylhexanoate, di-t-butyl
peroxyhexahydroterephthalate, t-amyl
peroxy-3,5,5-trimethylhexanoate, 3-hydroxy-1,1-dimethylbutyl
peroxyneodecanoate, 1,1,3,3-tetramethylbutyl
peroxy-2-ethylhexanoate, t-amyl peroxyneodecanoate, t-amyl
peroxy-2-ethylhexanoate, 2,2'-azobis-2,4-dimethylvaleronitrile,
1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobisisobutyronitrile,
2,2'-azobis(2-methylbutyronitrile),
dimethyl-2,2'-azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric
acid), 1,1'-azobis(1-cyclohexanecarbonitrile), t-hexyl
peroxyisopropylmonocarbonate, t-butyl peroxymaleic acid, t-butyl
peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylaurate,
2,5-dimethyl-2,5-di(3-methylbenzoylperoxy)hexane, t-butyl
peroxy-2-ethylhexylmonocarbonate, t-hexyl peroxybenzoate,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxybenzoate,
dibutyl peroxytrimethyladipate, t-amyl peroxy-n-octoate, t-amyl
peroxyisononanoate and t-amyl peroxybenzoate. These compounds may
be used singly or as a mixture of two or more.
[0047] The insulating adhesive composition 4 containing a
thermoplastic resin, a radically polymerizable compound and a
radical polymerization initiator may further contain additives, as
required.
[0048] The thickness of the above-mentioned adhesive layers 2, 2a
and 2b is preferably 5 to 50 .mu.m in consideration of the
adhesiveness and the conductivity. Further, the thickness thereof
2, 2a and 2b is more preferably 8 to 40 .mu.m in consideration of
the connection reliability. The thickness thereof 2, 2a and 2b can
be controlled by adjustment of the amount of involatile components
in an adhesive and adjustment of the gap of an applicator or a lip
coater.
[0049] According to the above-mentioned adhesive tape, decrease in
product yield can be suppressed and connection workability of solar
battery cells can be improved.
[0050] Such an adhesive tape can be fabricated by a conventional
well-known method, for example, the following method.
[0051] An adhesive composition containing constituents of the
above-mentioned insulating adhesive composition 4 is dissolved or
dispersed in an organic solvent to liquefy the composition, to
prepare a coating liquid. The coating liquid is applied on one
surface or both surfaces of a metal foil, and thereafter, the
solvent is removed to form an adhesive layer(s). At this time, if
the constituents of the insulating adhesive composition 4 include a
thermosetting resin and a curing agent for the thermosetting resin,
the coating liquid is dried at a temperature of less than the
activity temperature of the curing agent. The metal foil having the
adhesive layer(s) formed on one surface or both surfaces thereof in
such a way is slit into an appropriate width to obtain the
above-mentioned adhesive tape.
[0052] The organic solvent usable at this time includes, for
example, ester solvents such as ethyl acetate. The coating liquid
can be applied using a coating device such as a roll coater, a slit
die coater, a dip coater, a spin coater, an applicator or a lip
coater. In the case of fabricating an adhesive tape having adhesive
layers formed on both surfaces of a metal foil, an adhesive layer
is formed on one surface of the metal foil, and thereafter, an
adhesive layer may be formed on the other surface thereof; or a
coating liquid may be applied on both surfaces of a metal foil
using a dip coater or the like, and thereafter, is dried.
[0053] The adhesive tape of the present invention can be suitably
used for connection of solar battery cells. In solar battery
modules, generally, a plurality of solar battery cells equipped
with surface electrodes are in series and/or parallelly connected.
The connected solar battery cells are interposed by tempered glass
or the like for environment resistance and a gap between the solar
battery cell and the tempered glass is filled with a transparent
resin. The adhesive tape of the present invention is especially
suitably used for applications to connect a plurality of solar
battery cells in series and/or parallelly.
[0054] The solar battery module of the present invention has a
plurality of solar battery cells, which are electrically connected
using the above-mentioned adhesive tape.
[0055] Here, FIGS. 3, 4 and 5 are diagrams showing principal parts
of a solar battery module according to an embodiment of the present
invention, and show the structural outlines in which a plurality of
solar battery cells are connected to one another. FIG. 3 is a
partially broken plan view of the solar battery module according to
the embodiment; FIG. 4 is a partially broken bottom view of the
solar battery module in FIG. 3; and FIG. 5 is a sectional view
taken on line V-V in FIG. 3. In FIG. 3 and FIG. 4, a connection
member 120 described later is partially broken.
[0056] As shown in FIGS. 3, 4 and 5, the solar battery module 100
according to the embodiment has a plurality of solar battery cells
101. Each solar battery cell 101 has a power generating section 6.
The power generating section 6 generates an electromotive force by
solar light, and for example, is formed using a semiconductor
wafer. On the front surface of the power generating section 6, a
plurality of finger electrodes 7 (in FIGS. 3 to 5, six finger
electrodes) are parallelly provided. On the finger electrodes 7, a
plurality of bus electrodes 5a (in FIGS. 3 to 5, two bus
electrodes) are provided so as to intersect the finger electrodes
7. Here, the finger electrodes 7 and the bus electrodes 5a are
contacted.
[0057] On the other hand, on the rear surface of the power
generating section 6, a rear surface electrode 8 is provided, on
which 8 a plurality of bus electrodes 5b (in FIGS. 3 to 5, two bus
electrodes) are provided. Then, the rear surface electrode 8 and
the bus electrodes 5b are contacted.
[0058] Then, two solar battery cells 101 are connected through a
connection member 120. Specifically, one end of the connection
member 120 is connected to the bus electrodes 5a of one solar
battery cell 101; and the other end of the connection member 120 is
connected to the bus electrodes 5b of the other solar battery cell
101. That is, the solar battery cells 101 are connected in series.
The connection member 120 is constituted of a metal foil 1 and
connection layers 102a, 102b provided on both surfaces thereof,
respectively. The layer contacting with the bus electrodes 5b is
the connection layer 102a; and the layer contacting with the bus
electrodes 5a is the connection layer 102b.
[0059] Here, the connection member 120 is formed using an adhesive
tape 20. The connection layers 102a, 102b correspond to the
adhesive layers 2a, 2b in the adhesive tape 20, respectively. At
this time, if constituents of the insulating adhesive composition 4
include a thermosetting resin and a curing agent for the
thermosetting resin, portions of the connection layers 102a, 102b
corresponding to at least the bus electrodes 5a, 5b have been
subjected to a curing process by a method described later or the
like. Therefore, portions of the connection layers 102a, 102b
corresponding to at least the bus electrodes 5a, 5b are each
constituted of a conductive particle 3 and a cured body of the
insulating adhesive composition 4.
[0060] Then, in the solar battery module 100, the solar battery
cells 101 connected through the above-mentioned connection member
120 are interposed by tempered glass (not shown in figure) or the
like and a gap between the solar battery cells 101 and the tempered
glass is filled with a transparent resin (not shown in figure).
[0061] A material for the semiconductor wafer includes, for
example, a semiconductor of a single crystal, polycrystal and
non-crystal of silicon.
[0062] Materials for the finger electrodes 7, the bus electrodes 5a
and 5b, and the rear surface electrode 8 include common well-known
materials having conductivity, for example, a glass paste
containing silver, a silver paste, gold paste, carbon paste, nickel
paste and aluminum paste, in which various types of conductive
particles are dispersed in an adhesive resin, and ITO formed by
baking or deposition. Above all, an electrode composed of a glass
paste containing silver is suitably used in view of the heat
resistance, conductivity, stability and costs. The finger
electrodes 7, the bus electrodes 5a and 5b, and the rear surface
electrode 8 can be formed, for example, by screen printing.
[0063] If constituents of the insulating adhesive composition 4
include a thermosetting resin and a curing agent for the
thermosetting resin, the above-mentioned curing process of the
adhesive tape 20 can be performed by heat pressing, for example, at
140 to 200.degree. C. and 0.5 to 4 MPa for 5 to 20 sec. If
constituents of the insulating adhesive composition 4 include a
thermoplastic resin, a radically polymerizable compound and a
radical polymerization initiator, the above-mentioned curing
process of the adhesive tape 20 can be performed by heat pressing,
for example, at 140 to 200.degree. C. and 0.1 to 10 MPa for 0.5 to
120 sec. This curing process can pressure-bond the adhesive tape 20
to the bus electrodes 5a and 5b; and portions of the adhesive
layers 2a and 2b in the adhesive tape 20 corresponding to at least
the bus electrodes 5a and 5b are cured and the adhesive tape 20
becomes the connection member 120.
[0064] The solar battery module 100 having such a constitution
allows for an enhanced product yield and an improved connection
workability of solar battery cells because the above-mentioned tape
is used. Thereby, the cost when a solar battery module is
fabricated can be reduced.
EXAMPLES
[0065] Then, the present invention will be described in detail by
way of Examples, but the scope of the present invention is not
limited thereto.
Example 1
(1) Fabrication of an Adhesive Tap
[0066] 50 g of a phenoxy resin (high molecular epoxy resin)(made by
Union Carbide Chemical & Plastics Technology Corp., trade name:
PKHC), 20 g of an epoxy resin (made by Japan Epoxy Resins Co.,
Ltd., trade name: YL-980) and 5 g of imidazole were added to ethyl
acetate to prepare a 30 mass % ethyl acetate solution; and
chestnut-shaped Ni particles of 2.5 .mu.m in average particle size
of 5% by volume to the total volume of the solid components were
added to the solution. The obtained mixed solution was applied on
one surface of a copper foil of 75 .mu.m in thickness using a roll
coater. The applied solution was dried at 110.degree. C. for 5 min
to obtain a metal foil having an adhesive layer of 30 .mu.m in
thickness formed on the one surface. The resultant metal foil was
slit into a width of 2.0 mm to obtain an adhesive tape. Here, the
thickness of the adhesive layer was measured using a micrometer
(made by Mitutoyo Corp., ID-C112).
(2) Connection of Solar Battery Cells Using the Adhesive Tape
[0067] The adhesive tape was aligned in the width direction of the
electrode wiring (material: silver glass paste, 2 mm.times.15 cm,
Rz=10 .mu.m, Ry=14 .mu.m) formed on a solar battery cell
(thickness: 150 .mu.m, 15 cm.times.15 cm), and heat pressed at
170.degree. C. and 2 MPa for 20 sec using a pressure bonding tool
(tool name: AC-S300, made by Nikka Equipment & Engineering Co.,
Ltd.) to obtain a solar battery cell with an adhesive tape of
Example 1.
Example 2
[0068] A solar battery cell with an adhesive tape of Example 2 was
obtained as in Example 1, except for the thickness of the adhesive
layer of 40 .mu.m.
Example 3
[0069] A solar battery cell with an adhesive tape of Example 3 was
obtained as in Example 1, except for using gold-plated Ni particles
of 5 .mu.m in average particle size in place of the chestnut-shaped
Ni particles of 2.5 .mu.m in average particle size.
Example 4
[0070] A solar battery cell with an adhesive tape of Example 4 was
obtained as in Example 1, except for using gold/Ni-plated plastic
particles (styrene-butadiene copolymer) of 10 .mu.m in average
particle size of 0.5% by volume to the total volume of the solid
components in place of the chestnut-shaped Ni particles of 2.5
.mu.m in average particle size.
Example 5
[0071] A solar battery cell with an adhesive tape of Example 5 was
obtained as in Example 1, except for using an aluminum foil in
place of the copper foil.
Example 6
[0072] A solar battery cell with an adhesive tape of Example 6 was
obtained as in Example 1, except for using a copper foil of 175
.mu.m in thickness in place of the copper foil of 75 .mu.m in
thickness.
Example 7
[0073] A solar battery cell with an adhesive tape of Example 7 was
obtained as in Example 1, except for no addition of the Ni
particles.
Comparative Example 1
[0074] A solar battery cell with an adhesive tape of Comparative
Example 1 was obtained by using a TAB wiring in place of an
adhesive tape and connecting the Tab wiring and the electrode
wiring using a solder.
[0075] (Evaluation of Solar Batteries)
[0076] The solar battery cells with an adhesive tape obtained in
Examples 1 to 7 and Comparative Example 1 were measured for the
F.F. (curve factors) of solar batteries (initial values). Values of
the F.F. after exposure of cells to 85.degree. C. and 85% RH for
1,500 hours were also measured (final values). The IV curves were
measured using a solar simulator made by Wacom Electric Co., Ltd.
(WXS-155S-10, AM1.5G) and a value obtained by subtracting a final
value from an initial value was defined as a Delta (F.F.). Here, if
the Delta (F.F.) is not less than 0.2, the connection reliability
is not sufficient.
[0077] Further, the cell yield, the adhesive layer formability and
the adhesive tape formability were also evaluated. The cell yield
indicates a proportion (%) obtained by excepting cases exhibiting
cracks and exfoliations in 10 sheets of the solar battery cells as
a result of observing cell situations after the adhesive tape was
pressure bonded. The adhesive layer formability was evaluated as A
when there was observed no fault of not less than .phi.50 .mu.m;
and it was evaluated as B when there were observed faults of not
less than .phi.50 .mu.m. The adhesive tape formability was
evaluated as A when there was observed no floating and exfoliation
of the adhesive layer on the metal foil; and it was evaluated as B
when there was floating and exfoliation of the adhesive layer on
the metal foil. Constitutions of materials of the adhesive tapes in
Examples 1 to 7 above are shown in Table 1; and the evaluation
results about Examples 1 to 7 and Comparative Example 1 are shown
in Table 2.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Insulating Phenoxy 50 50 50 50 50 50
50 adhesive resin (g) Epoxy 20 20 20 20 20 20 20 resin (g)
Imidazole 5 5 5 5 5 5 5 (g) Thickness 30 40 30 30 30 30 30 (.mu.m)
Conductive Kind Chestnut-shaped Chestnut-shaped Gold-plated
Gold/Ni-plated Chestnut-shaped Chestnut-shaped None particle Ni
particle Ni particle Ni particle plastic particle Ni particle Ni
particle Average 2.5 2.5 5 10 2.5 2.5 -- particle size (.mu.m)
Content 5 5 5 0.5 5 5 0 (% by volume) Metal foil Kind Copper foil
Copper foil Copper foil Copper foil Aluminum foil Copper foil
Copper foil Thickness 75 75 75 75 75 175 75 (.mu.m)
TABLE-US-00002 TABLE 2 Comparative Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Example 7 Example 1 Delta (F. F.)
0.03 0.03 0.02 0.04 0.04 0.02 0.05 0.03 Cell yield (%) 100 100 100
100 100 100 100 60 Adhesive layer A A A A A A A -- formability Tape
formability A A A A A A A --
* * * * *