WO2013012071A1 - Electrically conductive material - Google Patents

Abstract

The present invention provides an electrically conductive material which is used for connecting an electrode of a solar battery cell and a wiring member and contains a resin binder and electrically conductive particles dispersed in the resin binder; the electrically conductive particles comprise phosphorus-containing copper alloy in which the phosphorus content is 0.01 mass% to 8 mass%.

Description

Conductive material

The present invention relates to a conductive material.

In recent years, solar cells have attracted attention as a means for solving problems such as global warming and depletion of fossil energy. This solar cell is usually formed by connecting a plurality of solar cells in series or in parallel. A plurality of linear electrodes (finger electrodes) made of Ag for obtaining an output are formed in parallel on the surface (light receiving surface) of the solar battery cell. A back electrode made of Al is formed on the back surface so as to cover the entire surface. Then, among adjacent solar cells, a metal wiring member (tab wire) is connected to the light receiving surface of one solar cell so as to be orthogonal to each finger electrode, and this tab wire is connected to the other solar cell. Adjacent solar cells are connected to each other by being connected to the back electrode. For this connection, a solder exhibiting good conductivity has been conventionally used. (Patent Documents 1 and 2).

On the other hand, from the viewpoint of environmental protection and the like, a method of connecting the solar cell electrode and the tab wire without using solder has been studied. For example, Patent Documents 3 to 8 below propose methods for electrically connecting the electrodes of the solar battery cells and the tab wires using a paste-like or film-like conductive adhesive (conductive material).

JP 2002-263880 A JP 2004-204256 A JP 2000-286436 A JP 2001-357897 A JP-A-7-147424 JP 2005-101519 A JP 2007-158302 A JP 2007-214533 A

However, when solder is used to connect solar cell tab wires, it is necessary to connect fine patterns individually, and heat of about 220 ° C. or more is applied. There is a limit to space saving.

Moreover, when the above-described conductive material is used, these problems can be solved to some extent. As the anisotropic conductive material or conductive material, conventionally, conductive particles mainly composed of gold or nickel are used for the purpose of reducing the connection resistance after connection and for stability. Thereby, the miniaturization of the device and the corrosion failure during use can be prevented.

However, in the case of gold, there is a problem that the manufacturing cost increases. Further, in the case of nickel, there is a problem that an environmental load increases. In addition, when conductive particles whose main component is other than these metals are used, it is difficult to obtain a stable connection resistance equivalent to the case where nickel or the like is used.

The present invention has been made to solve such a problem, and provides a conductive material that can be connected at a low temperature with a stable connection resistance and can suppress an increase in manufacturing cost. The purpose is to do.

The present invention contains a resin binder and conductive particles dispersed in the resin binder, and the conductive particles include a phosphorus-containing copper alloy having a phosphorus content of 0.01% by mass or more and 8% by mass or less. Provided is a conductive material used for connecting an electrode of a solar battery cell and a wiring member.

According to such a conductive material, it is possible to connect with high accuracy at a low temperature with a stable connection resistance, and it is possible to suppress an increase in manufacturing cost.

The average particle diameter of the conductive particles is preferably 0.4 μm to 30 μm. In the present specification, the “average particle size” refers to a particle size (hereinafter also referred to as “D50”) when the accumulated weight is 50%. In addition, as for the particle diameter of the conductive particles, when the shape of the conductive particles is other than spherical, the diameter of the smallest sphere circumscribing the conductive particles is defined as the particle diameter of the conductive particles.

The conductive particles are preferably conductive particles manufactured using a water atomization method.

The present invention also includes a resin binder and conductive particles dispersed in the resin binder, and the conductive particles include a phosphorus-containing copper alloy having a phosphorus content of 0.01% by mass to 8% by mass. Application of the composition as a conductive material for connecting the electrode of the solar battery cell and the wiring member, or for manufacturing a conductive material for connecting the electrode of the solar battery cell and the wiring member of the composition It may be related to the application.

According to the present invention, it is possible to provide a conductive material that can be accurately connected at a low temperature with a stable connection resistance and can suppress an increase in manufacturing cost.

It is a typical top view which shows the light-receiving surface in the one aspect | mode of the photovoltaic cell which can be connected with the electrically conductive material of this invention. It is a typical top view which shows the light-receiving surface in the one aspect | mode of the photovoltaic cell which can be connected with the electrically conductive material of this invention. It is a typical top view which shows the light-receiving surface in the one aspect | mode of the photovoltaic cell which can be connected with the electrically conductive material of this invention. It is a typical perspective view which shows the state which connected the several photovoltaic cell.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

The conductive material of the present invention includes a resin binder and conductive particles dispersed in the resin binder.

The conductive particles include a phosphorus-containing copper alloy containing copper and phosphorus. The phosphorus content in this phosphorus-containing copper alloy is 0.01% by mass or more and 8% by mass or less. When the phosphorus content is 8% by mass or less, a lower resistivity can be achieved, and the productivity of the phosphorus-containing copper alloy is excellent. Moreover, the more outstanding oxidation resistance can be achieved because the said phosphorus content rate is 0.01 mass% or more. The phosphorus content is more preferably 0.5% by mass to 7.8% by mass, and more preferably 1% by mass to 7.5% by mass from the viewpoint of oxidation resistance and low resistivity. More preferred. The phosphorus content is more preferably such that the peak temperature of the exothermic peak showing the maximum area in the differential thermal-thermogravimetric simultaneous measurement is 280 ° C. or higher.

The phosphorus-containing copper alloy is an alloy containing copper and phosphorus, but may further contain other atoms. Examples of other atoms include Sb, Si, K, Na, Li, Ba, Sr, Ca, Mg, Be, Zn, Pb, Cd, Tl, V, Sn, Al, Zr, W, Mo, Ti, Co, Ni, Au, etc. can be mentioned. Among these, Al is preferable from the viewpoint of adjusting characteristics such as oxidation resistance and melting point.
Moreover, the content rate when a phosphorus containing copper alloy contains another atom can be 3 mass% or less, for example, and it is preferable that it is 1 mass% or less from a viewpoint of oxidation resistance and a low resistivity. .

As the particle diameter of the conductive particles, the average particle diameter (D50) is preferably 0.4 μm to 30 μm, and more preferably 1 μm to 10 μm. When the thickness is 0.4 μm or more, the oxidation resistance is more effectively improved. Moreover, long-term connection stability is more effectively obtained by being 30 micrometers or less.
The shape of the conductive particles is not particularly limited, and may be any of a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like. The shape of the conductive particles is preferably substantially spherical, flat or plate-like from the viewpoint of oxidation resistance and low resistivity.

The phosphorus-containing copper alloy can be manufactured by a commonly used method. In addition, the conductive particles can be prepared using a normal method of preparing a metal powder using a phosphorus-containing copper alloy prepared so as to have a desired phosphorus content, for example, using a water atomization method. It can be produced by a conventional method. Details of the water atomization method are described in Metal Handbook (Maruzen Publishing Division).

Specifically, for example, a desired conductive particle can be produced by dissolving a phosphorus-containing copper alloy, pulverizing this by nozzle spraying, and drying and classifying the obtained powder. Moreover, the electroconductive particle which has a desired particle diameter can be manufactured by selecting classification conditions suitably.

The conductive particles may be those obtained by coating a metal or metal alloy such as silver, silver, palladium, or gold on the outside of the conductive particles produced from the phosphorus-containing alloy. The metal to coat | cover is preferable the metal which has silver as a main component from a viewpoint of cost. As a coating method, a conventional method such as plating or vapor deposition can be applied. The thickness of the coating is not particularly limited, but can be, for example, 1 μm or less, more preferably 0.5 μm or less from the viewpoint of cost.

Further, the above conductive particles may be used singly or in combination of two or more, or a combination of two or more containing conductive particles other than the phosphorus-containing copper alloy.

The content of the conductive particles contained in the conductive material can be, for example, 0.1 to 20% by volume, preferably 1 to 20% by volume, and more preferably 1 to 15% by volume. preferable. When the content is less than 0.1% by volume, the initial value of the connection resistance as the conductive material is increased as compared with the case where the content is within the above range. Moreover, when the said content rate exceeds 20 volume%, compared with the case where it exists in the said range, long-term connection stability as a electrically-conductive material will fall.
Further, when the content is 1 to 15% by volume, even if the bus bar of the solar battery cell is thin or not (bus barless), or there is no bus bar and the finger electrode is thin, long-term Connection stability can be more fully exhibited.

The resin binder is not particularly limited as long as it exhibits adhesiveness, but is preferably a resin composition containing a thermosetting resin from the viewpoint of further improving the connectivity.

As the thermosetting resin, known resins can be used, and examples thereof include an epoxy resin, a phenoxy resin, an acrylic resin, a polyimide resin, a polyamide resin, and a polycarbonate resin. These thermosetting resins can be used alone or in combination of two or more. Among these, from the viewpoint of further improving connection reliability, one or more thermosetting resins selected from the group consisting of epoxy resins, phenoxy resins, and acrylic resins are preferable.

Further, the resin composition as the adhesive component may contain a known curing agent and curing accelerator as optional components in addition to the above thermosetting resin.

Further, this resin composition contains a modifying material such as a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent in order to improve the adhesion and wettability to the adherend. In order to improve the uniform dispersibility of the conductive particles, a dispersant such as calcium phosphate and calcium carbonate may be contained.
Furthermore, this resin composition may contain a rubber component such as acrylic rubber, silicon rubber, and urethane in order to control the elastic modulus and tackiness, and is contained in the metal and conductive particles contained in the adherend. In order to suppress migration of metals (particularly silver and copper), a chelate material or the like may be contained.

For the conductive material, together with the above-mentioned resin binder and conductive particles, for example, an extender, a softener (plasticizer), an adhesive improver, an antioxidant, as long as the object of the present invention is not hindered. One or more of various additives such as an agent (anti-aging agent), a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant, a flame retardant, and an organic solvent may be used in combination.

The shape of the conductive material is not particularly limited. Specific examples thereof include (anisotropic) conductive paste, (anisotropic) conductive ink, (anisotropic) conductive adhesive, (anisotropic) conductive film, and (anisotropic) conductive sheet.

FIGS. 1 to 3 are schematic plan views showing light receiving surfaces of solar cells that can be connected by the conductive material of the present invention.

As shown in FIG. 1, a plurality of solar cells 100 are electrically connected in series or in parallel to form one solar cell module, and have a substrate 2. The substrate 2 has a substantially square shape, and its four corners have an arc shape. One surface of the substrate 2 is a light receiving surface 21. The substrate 2 is made of, for example, at least one of a silicon single crystal cell, a polycrystalline cell, an amorphous silicon cell, and a heterojunction cell. The substrate 2 may be an n-type semiconductor or a p-type semiconductor on the light receiving surface 21 side. For example, the distance between two opposing sides of the substrate 2 is 125 mm.

A plurality of (for example, 48) linear finger electrodes 3 are disposed on the surface of the light receiving surface 21 so as to be spaced apart from each other in parallel. Further, a bus bar 6 </ b> A is arranged so as to be orthogonal to the finger electrode 3. The finger electrode 3 and the bus bar 6A are formed of a metal paste such as silver, an electrolytic deposition conductive film, a conductive thin film, or the like.

When such a solar battery cell 100 is connected using the above-described conductive material, a conductive material is disposed in the adhesion region SF, and a wiring member is further disposed thereon. Furthermore, you may heat-press as needed. Examples of the heating and pressing conditions include 140 to 220 ° C., 1 to 30 minutes, and 0.1 to 0.3 MPa.

If the conductive material is in a liquid state, the conductive material may be applied and disposed by a dispensing method, a screen printing method, a stamping method, or the like.

The wiring member (tab wire) is not particularly limited. Specifically, the surface of a ribbon mainly made of copper having a thickness of 0.1 mm to 0.4 mm and a width of 0.5 mm to 10.0 mm is covered with leaded solder, lead-free solder, silver, tin or the like. Some tab lines can be used. It is also possible to use a tab line of a type in which the surface shape is a light diffusing surface, the sunlight rays irradiated on the tab line are diffusely reflected and retroreflected at the interface between the glass of the solar cell module and the atmosphere.

In addition, the photovoltaic cell of FIG. 2 is a thing which made the bus bar thin (bus bar 6B), and the photovoltaic cell of FIG. 3 is a thing which eliminated the bus bar. In any case, it is possible to connect the electrode of the solar battery cell and the wiring member by disposing the conductive material in the adhesion region SF.

When a plurality of solar cells are connected by the above-described method, a connection body in which a plurality of solar cells are connected can be obtained as shown in the schematic perspective view of FIG. In the connection body of FIG. 4, the solar cells 100A to 100D are connected via the wiring member 4, and the electrodes of the solar cells and the wiring member 4 are connected by the conductive material described above.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

<Conductive particles 1>
A phosphorus-containing copper alloy was prepared, dissolved, powdered by the water atomization method, dried and classified. The classified powders were blended and subjected to deoxygenation / dehydration treatment to produce phosphorus-containing copper alloy particles (conductive particles 1) containing 1% by mass of phosphorus. The average particle diameter (D50) of the phosphorus-containing copper alloy particles was 1.5 μm.

<Conductive particles 2>
A phosphorus-containing copper alloy was prepared, dissolved, powdered by the water atomization method, dried and classified. The classified powders were blended and subjected to deoxygenation / dehydration treatment to produce phosphorus-containing copper alloy particles (conductive particles 2) containing 6.57% by mass of phosphorus. The average particle size (D50) of the phosphorus-containing copper alloy particles was 4.4 μm.

<Conductive particles 3>
A phosphorus-containing copper alloy was prepared, dissolved, powdered by the water atomization method, dried and classified. The classified powder was blended and subjected to deoxygenation / dehydration treatment to produce phosphorus-containing copper alloy particles (conductive particles 3) containing 7.95% by mass of phosphorus. The average particle diameter (D50) of the phosphorus-containing copper alloy particles was 4.8 μm.

<Conductive particles 4>
Silver-coated phosphorus-containing copper alloy particles (conductive particles 4) in which silver was plated on the conductive particles 1 to a thickness of 0.1 μm were prepared.

<Conductive particles 5>
A commercially available nickel particle (conductive particle 5) having an average particle diameter (D50) of 5 μm was prepared.

<Conductive particles 6>
A commercially available silver-coated copper particle (conductive particle 6) having a particle diameter of 6 μm was prepared. Copper contains less than 0.01% by mass of phosphorus.

Example 1
(1) Production of conductive material layer:
The mass ratio of a liquid epoxy resin (epoxy equivalent 185) containing a phenoxy resin (high molecular weight epoxy resin) and a microcapsule-type latent curing agent was 30/70, and these were dissolved in ethyl acetate to obtain 30 masses of ethyl acetate. % Solution was obtained.
8% by mass (based on the total amount of the liquid conductive material) of the conductive particles 1 was added to this solution, and mixed and dispersed to obtain a liquid conductive material. This liquid conductive material was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 50 μm) with a bar coater and dried at 80 ° C. for 10 minutes to obtain a laminate in which a conductive material layer having a thickness of 25 μm was formed.
Thereafter, this laminate was cut into a width of 1.5 mm to obtain a conductive material in which a conductive material layer (thickness 25 μm) was provided on a strip-shaped separator.

(2) Connection:
All bus bars and tab wires (solder-plated copper wire, width 1.5 mm, thickness 0.2 mm) of solar cells (silicon substrate, 125 mm square, thickness 0.2 mm, two each on the front and back bus bars) It was sandwiched and electrically connected through the peeled conductive material. The connecting method is to arrange each material, and then use a crimping tool (trade name “AC-S300” manufactured by Nikka Engineering Co., Ltd.), heating temperature 180 ° C., pressurizing pressure 2 MPa, heating / pressurizing time 10 Heating and pressurizing were performed under the condition of seconds. All the bus bars of the solar cells were connected with a conductive material to obtain solar cells with tab wires.

(3) Evaluation:
The IV curve of the obtained solar cell with a tab line was measured using a solar simulator (trade name: WXS-155S-10, AM: 1.5G, manufactured by Wacom Denso Co., Ltd.), and a curve factor (fill factor, (Hereinafter abbreviated as FF). Furthermore, the conversion efficiency (η) was also derived at this time. Furthermore, long-term connection stability is "good" when the change in conversion efficiency (η) is within 5% before and after a 1000 hour exposure to 85 ℃, 85RH% constant temperature room environment. The case where it exceeded was determined as “bad”. The results are shown in Table 1.

Example 2
A conductive material was obtained in the same manner as in Example 1 except that 4% by mass (based on the total amount of the liquid conductive material) of the conductive particle 2 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 3
A conductive material was obtained in the same manner as in Example 1 except that 15% by mass (based on the total amount of the liquid conductive material) of the conductive particle 2 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 4
A conductive material was obtained in the same manner as in Example 1 except that 1% by mass (based on the total amount of the liquid conductive material) of the conductive particle 3 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 5
Instead of the conductive particles 1, the conductive material 2 was added in the same manner as in Example 1 except that 9% by mass (based on the total amount of the liquid conductive material) was added and the thickness of the conductive material layer was 35 μm. Obtained.
Thereafter, connection and evaluation were performed in the same manner as in Example 1 except that solar cells without a bus bar on the surface were used. The results are shown in Table 1.

Example 6
A conductive material was obtained in the same manner as in Example 1 except that 3% by mass (based on the total amount of the liquid conductive material) of the conductive particle 4 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
A conductive material was obtained in the same manner as in Example 1 except that 10% by mass (based on the total amount of the liquid conductive material) of the conductive particle 5 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2
The connection of the tab wire was tried using the solder to the solar cell without the bus bar on the surface. Specifically, the tab wires were arranged directly on the finger electrodes, and connection was attempted with a soldering iron at 300 ° C. while supplying the solder and melting the solder coated on the tab wire surface. However, the tab line was partially lifted and could not be connected.

Comparative Example 3
A conductive material was obtained in the same manner as in Example 1 except that 10% by mass (based on the total amount of the liquid conductive material) of the conductive particle 6 was added instead of the conductive particle 1. Thereafter, connection and evaluation were performed in the same manner as in Example 1. The results are shown in Table 2.

In addition, in the said embodiment, although the film-form conductive material is used as a conductive material, a liquid conductive material may be directly apply | coated to a photovoltaic cell.

3 ... finger electrode, 4 ... wiring member, 6A, 6B ... bus bar, 21 ... light receiving surface, 100 ... solar cell, SF ... adhesion region.

Claims (3)

Containing a resin binder and conductive particles dispersed in the resin binder,
The conductive particles include a phosphorus-containing copper alloy having a phosphorus content of 0.01% by mass or more and 8% by mass or less, and is a conductive material used for connecting an electrode of a solar battery cell and a wiring member. 2. The conductive material according to claim 1, wherein an average particle diameter of the conductive particles is 0.4 μm to 30 μm. The conductive material according to claim 1 or 2, wherein the conductive particles are conductive particles produced using a water atomization method.

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