WO2016060515A1 - Rear electrode-type solar cell module and method for manufacturing same - Google Patents

Abstract

The present invention relates to a rear electrode-type solar cell module and a method for manufacturing the same, wherein a rear substrate, a wire, an anisotropic conductive adhesive having a conductive ball, a battery cell having electrodes, and a front substrate are sequentially stacked, the conductive ball electrically connects the wire and the electrodes, the conductive ball fixed between the wire and the electrodes has an elliptical spherical shape transformed from a spherical shape, and the minor axis diameter of the transformed ellipse of the conductive ball is 25-95% of the diameter of a sphere before transformation.

Description

Back electrode solar cell module and manufacturing method

The present invention relates to a back electrode solar cell module and a method of manufacturing the same.

The anisotropic conductive adhesive is a structure in which conductive balls are evenly distributed in the polymer matrix. When bonding, the conductive ball does not pass through the substrate in the horizontal direction but conducts electricity through the conductive ball in the vertical direction. It is used mainly. Anisotropic conductive adhesives are essential for the electrical bonding of microcircuits such as liquid crystal displays because of their high conductivity and insulation reliability without short circuiting and damage to circuit patterns even when connecting bumps or circuits with small pitches. Material.

In the back electrode solar cell module, a rear substrate, a wiring substrate having wiring, a battery cell in which electrodes are formed, and a front substrate are sequentially stacked, and the wiring and the electrodes are connected to allow electricity. Although the process temperature was high and the possibility of cell breakage due to stress was high when connecting between the back electrode solar cells using the conventional soldering method, by applying an anisotropic conductive adhesive to the connection between the back electrode solar cell and the wiring board By eliminating the soldering process, the possibility of cell breakage is reduced, and since lead is not used, there is an environmentally friendly advantage. Therefore, there is a need to manufacture a high efficiency back electrode solar cell using an anisotropic conductive adhesive.

The present invention provides a back-electrode solar cell module and a method of manufacturing the same that can reduce the production cost and maximize the output by applying a conductive ball different from the conventional art.

In the back electrode solar cell module according to an embodiment of the present invention, a back substrate, a wiring, an anisotropic conductive adhesive having a conductive ball, a battery cell having an electrode, and a front substrate are stacked in this order, and the conductive ball is connected to the wiring. The conductive ball is electrically connected to the electrode, and the conductive ball fixed between the wire and the electrode is deformed from a spherical shape to an elliptic spherical shape, and the short axis diameter of the deformed ellipse of the conductive ball is 25 To 95%.

The back substrate, the wiring, the anisotropic conductive adhesive having the conductive ball, the battery cell having the electrode, and the structure in which the front substrate were laminated in this order were applied in a closed space in a vacuum state and applied a pressure of 0.05 MPa to 0.5 MPa. It may be to change the diameter of the conductive ball.

The conductive ball may have a strain of 50 to 95% at a force of 100 mN or less.

The conductive ball may include a body and a conductive layer surrounding the body, and the conductive layer may be made of nickel.

The conductive ball may have a size of 8 μm to 40 μm.

Method of manufacturing a back electrode solar cell module according to an embodiment of the present invention comprises the step of stacking a back substrate, a wiring, an anisotropic conductive adhesive having a conductive ball, a battery cell having an electrode and a front substrate in order to form a structure, the Placing a structure in a vacuum state, and applying a pressure and heat of 0.05 MPa to 0.5 MPa to the structure placed in a vacuum state, wherein the conductive ball placed in a conductive region facing the wiring and the electrode is controlled by the pressure. The shape is deformed, and the short axis diameter of the deformed conductive ball is 25 to 95% of the corresponding diameter before deformation.

The conductive ball may have a strain of 25 to 95% at a force of 20 to 100mN.

According to the embodiment of the present invention, it is possible to manufacture a highly efficient back electrode solar cell without changing the existing module lamination process conditions, to simplify the cell manufacturing process, and to reduce the manufacturing cost.

According to an embodiment of the present invention, a structure in which a back substrate, wiring, an anisotropic conductive adhesive having a spherical conductive ball having a size of 8 μm to 40 μm, a battery cell having an electrode, and a front substrate are sequentially stacked in a vacuum-closed space is provided. The pressure of 0.05MPa to 0.5MPa is applied to change the spherical conductive ball into elliptic sphere to connect the electrode and the wire. The contact area between the electrode and the wire is increased so that the output of the back electrode solar cell module is maximum. Becomes

According to an embodiment of the present invention, the filling rate was maximized by applying a conductive ball having a strain of 50% or more at a force of 100mN or less or a conductive ball having a strain of 25 to 95% at a force of 20 to 100mN.

When the electrode and the wiring are connected under the above conditions, even if the conductive layer of the conductive ball is formed of nickel instead of gold, a difference in charge rate does not occur. Therefore, the conductive layer can be formed of inexpensive nickel instead of expensive gold, thereby reducing the cost of the anisotropic conductive adhesive and further lowering the manufacturing cost of the back electrode solar cell module.

1 is a back electrode solar cell module structure according to an embodiment of the present invention.

2 is a cross-sectional view of a back electrode solar cell module formed by combining the structure shown in FIG.

FIG. 3 is an enlarged view of a portion A shown in FIG. 2; FIG.

4 is a cross-sectional view showing a modified conductive ball shown in FIG.

5 is an experimental result table comparing the filling rate according to the strain of the conductive ball of different strength.

6 is a table showing a comparative comparison of the filling rate according to the conductive ball strain when the number of conductive balls are the same.

Figure 7 is a result of the experiment of the change of the filling rate according to the size of the conductive ball.

8 is a test result table comparing the filling rate by changing the material of the conductive layer.

9 is a result table comparing the output reduction rate over the heat cycle according to the material of the conductive layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Like parts are designated by like reference numerals throughout the specification.

Next, a back electrode solar cell module according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 3.

1 is a back electrode solar cell module structure according to an embodiment of the present invention, Figure 2 is a cross-sectional view of the back electrode solar cell module formed by combining the structure shown in Figure 1, Figure 3 is shown in Figure 2 A section enlargement is also.

1 to 3, the back electrode solar cell module according to the present embodiment includes a back substrate 10, a wiring substrate 30, a battery cell 50, an anisotropic conductive adhesive 40, and a front substrate ( 60). Furthermore, the present embodiment may further include a charging unit 20.

The rear substrate 10 and the front substrate 60 face each other with a gap therebetween, and the charging unit 20, the wiring substrate 30, the battery cell 50, and the anisotropic conductivity are disposed between the rear substrate 10 and the front substrate 60. Adhesive 40 is located. The rear substrate 10 and the front substrate 60 protect the wiring board 30, the battery cell 50, and the like from foreign matters such as dust and rainwater, impact, and the like.

The rear substrate 10 supports the wiring substrate 30, the battery cell 50, and the like, and may be made of plastic, glass, metal, polyethylene terephthalate (PET), or the like. The front substrate 60 may be made of a transparent material through which sunlight can pass.

The charging unit 20 connects the rear substrate 10 and the front substrate 60, and fixes the wiring substrate 30 and the battery cell 50 positioned between the rear substrate 10 and the front substrate 60 to prevent movement. At the same time, it is protected from foreign substances. The charging unit 20 includes a first filler 21 connected to the rear substrate 10 and a second filler 22 connected to the front substrate 60, and the first filler 21 and the second filler 22 are respectively The wiring board 30, the battery cell 50, and the like are positioned between the first filler 21 and the second filler 22. Although the charging unit 20 is described as the first filler 21 and the second filler 22, when the lamination process is performed during the manufacturing process of the back electrode solar cell module, the first filler 21 and the second filler 22 are described. ) Are combined with each other to form a single member.

The charging unit 20 may be made of ethylene vinyl acetate, poly vinyl butyral, or the like.

The wiring board 30 includes a wiring sheet 31 connected to the first filler 21 and a plurality of wirings 32 formed on one surface of the wiring sheet 31. The wirings 32 are connected to each other at one side of the wiring sheet 31. The wiring sheet 31 may be made of polyethylene terephthalate (PET), polyimide (PI), or the like. The wiring 32 may be made of metal such as copper, aluminum, gold, etc., through which electricity can pass.

However, the wiring sheet 31 may be omitted, and in this case, the wiring 32 may be directly formed on one surface of the rear substrate 10. In this case, an insulating layer (not shown) may be formed between the rear substrate 10 and the wiring 32.

The battery cell 50 includes a main body 51 and an electrode 52. The main body 51 is connected to the front substrate 60 by the second filler 22 and faces the wiring substrate 30. The main body 51 collects sunlight passing through the front substrate 60 to generate electrons and holes by the photoelectric effect to produce electricity.

The electrode 52 is formed on one surface of the main body 51 facing the wiring board 30 and is electrically connected to the wiring 32. The electricity produced in the body 51 may flow to the electrode 52.

Although only one battery cell 50 is illustrated in FIGS. 1 and 2, a plurality of battery cells 50 may be arranged along the length direction of the wiring board 30. The number of battery cells 50 may vary depending on the design conditions of the back electrode solar cell module 1.

The anisotropic conductive adhesive 40 is disposed between the wiring board 30 and the battery cell 50, and connects the wiring board 30 and the battery cell 50. The anisotropic conductive adhesive 40 includes the resin layer 41 and the conductive balls 42a and 42b.

The resin layer 41 has adhesiveness and connects the battery cell 50 and the wiring board 30. In addition, the resin layer 41 connects the electrode 52 and the wiring 32 to each other. The resin layer 41 may be made of epoxy, urethane, acrylic, or the like.

The conductive balls 42a and 42b are formed in a particulate form and are arranged in the resin layer 41, and are concentrated in the conductive region B between the wiring 32 and the electrode 52. The number of conductive balls 42b located in the insulating region C between the conductive region B and the adjacent conductive region B is smaller than the number of conductive balls 42a in the conductive region B. Furthermore, the conductive ball 42b may not be located in the insulating region C.

The conductive ball 42a of the conductive region B electrically connects the wiring 32 and the electrode 52, so that electricity flowing from the main body 51 to the electrode 52 flows to the wiring 32 and the wiring 32. Can be collected in a junction box connected to the

When a plurality of battery cells 50 are arranged on the wiring board 30, the electricity produced in all battery cells 50 may be collected in the junction box through the wiring sheet 31.

The diameters of the conductive balls 42a and 42b are smaller than the thickness of the resin layer 41 and larger than the distance between the wiring 32 and the electrode 52. In addition, the diameters of the conductive balls 42a and 42b are smaller than the width of the insulating region C. FIG. The conductive ball 42a positioned in the conductive region B is deformed from a spherical shape to an elliptic sphere shape while the wiring 32 and the electrode 52 are pressed. The conductive ball 42b disposed in the insulating region C is not deformed and is not connected to the wiring 32 and the electrode 52. Therefore, the neighboring electrode 52 and the electrode 52, the wiring 32, and the wiring 32 are not energized with each other.

In FIG. 3, two conductive balls 42a are positioned in the conductive region B, and one conductive ball 42b is positioned in the insulating region C. However, the number of conductive balls 42a and 42b is the rear electrode. It may vary depending on the design conditions of the type solar cell module (1). The number of conductive balls 42a disposed per unit area of the conductive region B is larger than the number of conductive balls 42b disposed per unit area of the insulating region C. FIG. However, the conductive ball 42b may not be disposed in the insulating region C.

The conductive balls 42a and 42b include bodies 421a and 421b made of resin series, and conductive layers 422a and 422b which surround and support the bodies 421a and 421b. The strength of the conductive balls 42a and 42b is less than that of the electrode 52 and the wiring 32 so that when pressure is applied from the outside, the conductive ball 42a is deformed by the electrode 52 and the wiring 32. Can be.

The conductive balls 42a and 42b are formed to have a size of 8 μm to 40 μm. At atmospheric pressure, the conductive balls 42a and 42b may have a strain of 50% or more at a force of 100 mN or less, or a strain of 25 to 95% at a force of 20 to 100mN.

As shown in FIG. 1, a conductive ball before applying pressure to a structure in which a back substrate 10, a charging unit 20, a wiring board 30, an anisotropic conductive adhesive 40, a battery cell 50, and a front substrate 60 are stacked. 42a and 42b are spherical. However, when the pressure of 0.05 MPa to 0.5 MPa is applied to the structure in a space enclosed in a vacuum state by lamination or the like, the charging unit 20 and the anisotropic conductive adhesive 40 are compressed to the conductive region B. The conductive balls 42a positioned are in contact with the wirings 32 and the electrodes 52 and are deformed into elliptical spheres. In addition to pressure, the structure may also be heated.

At this time, the deformation rate of the conductive ball 42a is 25 to 95%. The above strain means that the uniaxial diameter D1 of the deformed elliptic sphere shape is 25 to 95% of the diameter D2 of the deformed sphere shape (see FIG. 4).

If the conductivity of the conductive ball 42a is less than 25%, the contact area between the wiring and the electrode is weak and the connection resistance is large. If the connection resistance is large, the charge rate is low and the output is low.

If the strain of the conductive ball 42a exceeds 95%, cracks may occur on the surface of the conductive ball 42a. When the conductive ball 42a is deformed under pressure, a crack in the vertical direction is mainly generated at first, but a crack in the horizontal direction is generated when the conductive ball 42a is severely pressed. If the direction of the crack is vertical, it is not a big problem because it is parallel to the direction of charge movement. However, if a crack occurs in the horizontal direction, an increase in resistance or a short circuit occurs because the direction prevents the movement of charge.

The conductive ball applied in this embodiment is a soft material having a strain of 25 to 95% when a pressure of 0.05 MPa to 0.5 MPa is applied while the structure is placed in a closed space in a vacuum state. However, relatively hard conductive balls have little or no strain when the above pressure is applied, which reduces the area of contact between the electrodes and the wiring. As the contact area decreases, the charge rate decreases, resulting in lower power. Therefore, the conductive ball must be deformed more than 25% to increase the filling rate and output power. Preferably, the filling rate is further improved when the conductive ball has a strain of 50 to 95%.

The conductive ball 42b positioned in the insulating region C does not contact the wiring sheet 31 and the wiring 32, the main body 51, the electrode 52, and the like, and thus is not deformed.

The method of applying pressure and heat to the structure can be implemented by methods other than lamination.

In the conductive ball 42a deformed into an elliptic sphere shape, the area of contact with the electrode 52 and the wiring 32 increases more than that of the spherical shape. Accordingly, if the conductive ball 42a before the pressure is in point contact with the wiring 32 and the electrode 52, the deformed conductive ball 42a is in planar contact with the wiring 32 and the electrode 52. The contact area is increased.

As the contact area of the electrode 52 and the wiring 32 decreases due to an increase in the contact area, the connection resistance, which may increase, may be increased, thereby improving the fill factor (FF). The filling rate is a measure of how well the wiring 32 and the electrode 52 are electrically connected. If the wiring 32 and the electrode 52 are well connected due to the conductive ball 40, the charging rate is increased.

5 and 6, it can be seen that the filling rate is affected by the magnitude of the force applied to the conductive ball and the degree of deformation thereof.

First, referring to Figure 5, by applying a force of 100mN or 120mN to the conductive ball to make a 50% strain of the conductive ball to compare the filling rate.

If the conductive ball has a strain of 50% or less at a force of 100mN or less, the strength is soft, and if the strain is 50% at a force exceeding 100mN, the strength is relatively hard.

According to the above experiment, the strength of the conductive ball affects the module efficiency. If the size of the conductive ball is smaller than the distance between the electrodes of the adjacent conductive region as in the present embodiment, and the conductive ball of such a size is 50 mm or more at a force of 100 mN or less, a highly efficient rear electrode module can be manufactured. However, it can be seen that the use of conductive balls with 50% strain at a force of 120mN decreases the efficiency.

Referring to FIG. 6, when the number and the strength of the conductive balls are the same, it can be seen that the filling rate increases from 25% or more of the conductive ball strain. If the strain rate is 50% or more, there is no significant difference in the filling rate to 0.5%, but as the strain rate increases, the filling rate increases little by little. The preferred strain of the conductive ball can be seen as 50 to 95%. In other words, the greater the strain of the conductive ball, the lower the connection resistance and the better the charging rate, thereby increasing the output.

7 is a result of experiments in the change of the filling rate according to the size of the conductive ball. In this experiment, the strength and strain of the conductive ball were used in the range of this embodiment.

Referring to FIG. 7, the charging rate is high when the size of the conductive ball is about 8 μm or more when the charging rate of the back electrode type solar cell module having the size of the conductive ball is 8 μm to 40 μm, and the charging rate is highest when the size of the conductive ball is 20 μm. Able to know. However, when the size of the conductive ball is less than 8㎛ or more than 40㎛ it can be seen that the filling rate is reduced.

In addition, when the number of conductive balls is the same, when the size is less than 8 μm, the contact area between the electrode 52 and the wiring 32 is small, and the filling rate is drastically reduced, and when the size of the conductive ball exceeds 40 μm, It can be seen that the pressure applied per unit area of the ball is reduced and is less pressed, thereby reducing the filling rate due to the decrease of the contact area.

According to the design conditions of the module, it is preferable to use conductive balls having a size of 8 μm to 40 μm, and as the size of the conductive balls becomes smaller, the number of conductive balls can be increased.

8 is a conductive ball having the same strength and size as in the present embodiment, but comparing the filling rate by changing the material of the conductive layer. Referring to FIG. 8, it can be seen that there is almost no difference when the filling rate is compared between the conductive layer of the conductive ball formed of gold and nickel.

In other words, the conductive ball is applied to a structure in which a sphere-shaped conductive ball having a size of 8 μm to 40 μm is applied in a vacuum-tight space with a pressure of 0.05 MPa to 0.5 MPa. When forming a back electrode solar cell module in which an electrode and a wire are connected by deforming to an elliptic sphere with a strain of 95% to 95%, even though the conductive layer material of the conductive ball is formed of nickel, the charging rate is almost insignificant. Able to know.

Thus, the conductive layer may be formed of inexpensive nickel instead of expensive gold. In this way, the cost of the anisotropic conductive adhesive 40 can be lowered, and the cost of the back electrode solar cell module can be lowered.

The output is = Isc x Voc x charge rate. The filling rate is mainly changed by the resistive component, and Isc is mainly changed by the amount of light, and Voc is mainly changed by the type of substrate, the amount of impurities, p-n junction characteristics, temperature, and the like. In other words, the charging rate is checked to check whether the solar cells constituting the module are well connected. This is to remove the influence of other variables such as the characteristics of the module and the temperature during measurement. Thermal cycle reliability tests can verify the reliability results by measuring the output.

Referring to FIG. 9, the conductive layer material of the conductive balls is made of gold and nickel, and a structure in which a spherical conductive ball having a size of 8 μm to 40 μm is applied is placed in a closed space in a vacuum state to a pressure of 0.05 MPa to 0.5 MPa. It can be seen that the difference in the output power of energy generated when light is applied to the module under the condition of connecting the electrode and the wiring by deforming the conductive ball into an elliptic sphere shape with a strain of 25 to 95%.

9 is a comparison of the output reduction rate with the heat cycle according to the material of the conductive layer.

Thermal Cycling Reliability (T / C Reliability) The results show that the difference between gold and nickel in the output reduction rate is less than 1% after 200 cycles. Accordingly, it can be seen that there is no difference in reliability between the conductive ball made of gold and the conductive ball made of nickel.

Therefore, in the case of the conductive ball meeting the conditions of the present embodiment, since the conductive layer can be formed of nickel instead of gold, it is possible to reduce the cost of the anisotropic conductive adhesive, which is the production cost of the back electrode solar cell module Lowers the result.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (7)

The back substrate, the wiring, the anisotropic conductive adhesive having the conductive balls, the battery cell having the electrodes and the front substrate are stacked in this order, and the conductive balls electrically connect the wirings and the electrodes, and between the wirings and the electrodes. The conductive ball fixed to the one is deformed from a spherical shape to an elliptic sphere shape, the short axis diameter of the deformed ellipse of the conductive ball is 25 To 95% of the back electrode solar cell module. In claim 1, The back substrate, the wiring, the anisotropic conductive adhesive having the conductive balls, the battery cell having the electrodes, and the front substrate laminated structure were sequentially placed in a closed space in a vacuum state, and a pressure of 0.05 MPa to 0.5 MPa was applied thereto. Back electrode type solar cell module that changes the diameter of the conductive ball. In claim 1, The conductive ball has a back electrode type solar cell module having a strain of 50 to 95% at a force of 100mN or less. In claim 1, The conductive ball includes a body and a conductive layer surrounding the body, wherein the conductive layer is made of nickel back electrode solar cell module. In claim 1, A size of the conductive ball is 8㎛ to 40㎛ back electrode type solar cell module. Forming a structure by sequentially stacking a back substrate, wiring, an anisotropic conductive adhesive having a conductive ball, a battery cell having an electrode, and a front substrate; Placing the structure in a vacuum, and Applying pressure and heat of 0.05 MPa to 0.5 MPa to the structure in vacuum; Including, The conductive ball placed in the conductive region facing the wiring and the electrode is deformed by the pressure, and the short axis diameter of the deformed conductive ball is 25 to 95% of the corresponding diameter before deformation. Method of manufacturing a back electrode solar cell module. In claim 6, The conductive ball is a method of manufacturing a back electrode solar cell module having a strain of 25 to 95% at a force of 20 to 100mN.

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