KR20160045502A - Back contact solar cell module and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a back contact solar cell module and a manufacturing method thereof. A battery cell which has a back substrate, a line, an anisotropic conducive adhesive having a conductive ball, an electrode, and a front substrate are successively stacked. The conductive ball is electrically connected to the electrode and the line. The spherical shape of the conductive ball fixed between the line and the electrode is changed into an oval shape. The diameter of the minor axis of the oval of the conductive ball is 25 to 95% of the diameter of the sphere. So, manufacturing costs can be reduced.

Description

TECHNICAL FIELD [0001] The present invention relates to a back electrode type solar cell module and a method of manufacturing the same. BACKGROUND ART [0002]

The present invention relates to a rear electrode type solar cell module and a manufacturing method thereof.

The anisotropic conductive adhesive is a structure in which the conductive balls are uniformly dispersed in the polymer matrix. When the adhesive is applied to the substrate, electricity does not pass horizontally to the substrate, but electricity passes through the conductive balls in the vertical direction. It is mainly used. The anisotropic conductive adhesive is not required to have a short circuit phenomenon and does not cause damage to the circuit pattern even when a circuit having a small bump or pitch is connected, Material.

The rear electrode type solar cell module has a rear substrate, a wiring substrate having wiring, a battery cell having electrodes formed thereon, and a front substrate sequentially laminated, and the wiring and the electrode are electrically connected to each other. When the back electrode type solar cells are connected by using the conventional soldering method, the process temperature is high and the possibility of cell breakage due to stress is high. However, by applying an anisotropic conductive adhesive to the connection between the back electrode type solar cell and the wiring board The soldering process is omitted, the possibility of cell breakage is reduced, and there is an advantage that it is environmentally friendly because lead is not used. Therefore, there is a need to fabricate a back electrode type solar cell with high efficiency using an anisotropic conductive adhesive.

Patent No. 10-1194864 (Oct. 19, 2012)

The present invention provides a rear electrode type solar cell module and a method of manufacturing the same that can reduce production cost and maximize output by applying conductive balls different from conventional ones.

A back electrode type solar cell module according to an embodiment of the present invention includes a rear substrate, a wiring, an anisotropic conductive adhesive having conductive balls, a battery cell having electrodes, and a front substrate are stacked in order, Wherein the conductive ball fixed between the wiring and the electrode is deformed into an elliptic sphere from a spherical shape and the minor axis diameter of the deformed ellipse of the conductive ball is 25 To 95%.

A pressure of 0.05 MPa to 0.5 MPa was applied while keeping the vacuum chamber in a closed space with the back substrate, the wiring, the anisotropic conductive adhesive having the conductive balls, the battery cell having the electrode, and the front substrate laminated in this order The diameter of the conductive ball may be changed.

The conductive balls 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 size of the conductive balls may be 8 μm to 40 μm.

A method of fabricating a back electrode type solar cell module according to an embodiment of the present invention includes forming a structure by sequentially laminating an anisotropic conductive adhesive having a back substrate, wiring, conductive balls, a battery cell having electrodes, and a front substrate, Placing the structure in a vacuum state and applying a pressure and a pressure of 0.05 MPa to 0.5 MPa to the structure placed in a vacuum state, wherein the conductive ball placed in the conductive region where the wiring and the electrode face each other, The shape is deformed, and the minor axis diameter of the deformed conductive ball is 25 to 95% of the diameter before deformation.

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

According to the embodiment of the present invention, it is possible to manufacture a rear electrode type solar cell with high efficiency without changing the existing module lamination process conditions, to simplify the cell manufacturing process, and to reduce the manufacturing cost.

According to the embodiment of the present invention, a structure in which a back substrate, a wiring, an anisotropic conductive adhesive having spherical conductive balls of 8 to 40 탆 in size, a battery cell having electrodes, and a front substrate are stacked in order, And the electrode and the wiring are connected by changing the spherical conductive balls into an elliptic spherical shape by applying a pressure of 0.05 MPa to 0.5 MPa. The contact area between the electrode and the wiring is increased, so that the output of the rear electrode type solar cell module is maximized .

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

When the electrode and the wiring are connected with each other under the above conditions, even if the conductive layer of the conductive ball is formed of nickel instead of gold, there is no difference in the filling rate. Therefore, the conductive layer can be formed of inexpensive nickel instead of expensive gold, so that the cost of the anisotropic conductive adhesive can be reduced and the manufacturing cost of the rear electrode type solar cell module can be reduced.

1 is a rear electrode type solar cell module structure according to an embodiment of the present invention.
2 is a sectional view of a rear electrode type solar cell module formed by combining the structure shown in FIG.
3 is an enlarged view of a portion A shown in Fig.
4 is a cross-sectional view of the deformed conductive ball shown in Fig. 3;

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like parts are designated with like reference numerals throughout the specification.

A back electrode type solar cell module according to an embodiment of the present invention will now be described with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a cross-sectional view of a rear electrode type solar cell module according to an embodiment of the present invention, FIG. 2 is a sectional view of a rear electrode type solar cell module formed by combining the structure shown in FIG. 1, An enlarged view of a portion A is shown.

1 to 3, the rear electrode type solar cell module according to the present embodiment includes a rear substrate 10, a wiring substrate 30, a battery cell 50, an anisotropic conductive adhesive 40, 60). Further, the present embodiment may further include a charging unit 20. [

The rear substrate 10 and the front substrate 60 are spaced apart from each other with a space between the rear substrate 10 and the front substrate 60. The charging portion 20, the wiring substrate 30, the battery cell 50, The adhesive 40 is located. The rear substrate 10 and the front substrate 60 protect the wiring substrate 30, the battery cell 50, and the like from foreign substances such as dust, rain, and the like.

The rear substrate 10 supports the wiring substrate 30 and the battery cells 50 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 be transmitted.

The charging unit 20 connects the rear substrate 10 and the front substrate 60 and electrically connects the wiring substrate 30 positioned between the rear substrate 10 and the front substrate 60 to the battery cell 50, At the same time, it is protected from foreign substances. The charging part 20 includes a first filling material 21 connected to the rear substrate 10 and a second filling material 22 connected to the front substrate 60. The first filling material 21 and the second filling material 22 And the wiring board 30, the battery cell 50, and the like are positioned between the first filler 21 and the second filler 22. When the lamination process is performed during the manufacturing process of the back electrode type solar cell module, the first filling material 21 and the second filling material 22 are used as the first filling material 21 and the second filling material 22. However, Are formed as one member by being coupled to each other.

The charging part 20 may be made of ethylene vinyl acetate, polyvinyl 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 an electrically conductive metal such as copper, aluminum, or gold.

However, the wiring sheet 31 may be omitted, and in this case, the wiring 32 may be formed directly on one surface of the rear substrate 10. At this time, 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 board 30. [ The main body 51 collects the sunlight transmitted through the front substrate 60 and generates 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. Electricity produced in the main body 51 can flow to the electrode 52. [

Although only one battery cell 50 is shown in Figs. 1 and 2, a plurality of battery cells 50 may be arranged along the longitudinal direction of the wiring board 30. Fig. The number of the battery cells 50 may vary depending on the design conditions of the back electrode type 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 a resin layer 41 and conductive balls 42a and 42b.

The resin layer 41 has adhesiveness and connects the battery cell 50 and the wiring board 30. 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 the form of fine particles and 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 the 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 the conductive balls 42a in the conductive region B. [ Furthermore, the conductive balls 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 into the wiring 32, ) In the junction box.

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

The diameter of the conductive balls 42a and 42b is smaller than the thickness of the resin layer 41 and larger than the interval between the wiring 32 and the electrode 52. [ The diameters of the conductive balls 42a and 42b are smaller than the width of the insulating region C. The conductive ball 42a located in the conductive region B is deformed from spherical to ellipsoidal in shape while the wiring 32 and the electrode 52 are pressed. The conductive ball 42b located 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, the electrode 52, the wiring 32 and the wiring 32 are not energized.

3, two conductive balls 42a are positioned in the conductive region B and one conductive ball 42b is located in the insulating region C. However, the number of the conductive balls 42a and 42b may be different from that of the rear electrode Type solar cell module 1 according to the present invention. The number of the conductive balls 42a arranged per unit area of the conductive region B is larger than the number of conductive balls 42b arranged per unit area of the insulating region C. However, the conductive balls 42b may not be disposed in the insulating region C.

The conductive balls 42a and 42b include bodies 421a and 421b made of resin and conductive layers 422a and 422b that surround the bodies 421a and 421b and can be energized. The strength of the conductive balls 42a and 42b is smaller than the strength of the electrodes 52 and 32 so that the conductive ball 42a is pressed and deformed by the electrode 52 and the wiring 32 .

The conductive balls 42a and 42b are formed to have a size of 8 to 40 탆. Under 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 100 mN.

As shown in Fig. 1, a conductive ball (not shown) is applied to a structure in which a rear substrate 10, a charging portion 20, a wiring board 30, an anisotropic conductive adhesive 40, a battery cell 50, (42a, 42b) are spherical. However, when a pressure of 0.05 MPa to 0.5 MPa is applied to the structure in a vacuum sealed state by a method such as lamination, the charging part 20 and the anisotropic conductive adhesive 40 are pressed and pressed to the conductive area B The conductive ball 42a placed in contact with the wiring 32 and the electrode 52 is pressed and deformed into an elliptical sphere shape. In addition to pressure, heat can be applied to the structure.

At this time, the strain of the conductive ball 42a is 25 to 95%. The above strain means that the uniaxial diameter D1 of the deformed elliptical shape is 25 to 95% of the diameter D2 of the deformed precursor shape (see Fig. 4).

When the strain of the conductive ball 42a is less than 25%, the contact area between the wiring and the electrode is weak and the connection resistance becomes large. If the connection resistance is large, the filling 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, cracks in the vertical direction are mainly generated at the beginning, but cracks in the horizontal direction are generated when the conductive balls are pressed hardly. If the direction of the crack is vertical, it is parallel to the direction of charge movement, which is not a big problem. However, if cracks occur in the horizontal direction, resistance increases or short-circuit occurs because it is a direction to obstruct the movement of charges.

The conductive balls applied to the present embodiment are those having a strain of 25 to 95% when a pressure of 0.05 MPa to 0.5 MPa is applied with the structure placed in a closed space in a vacuum state. However, a relatively hard conductive ball has little or no strain when applied with the above pressure, which reduces the contact area between the electrode and the wiring. As the contact area decreases, the charge rate decreases and the output decreases. Therefore, when the conductive ball is deformed by 25% or more, the filling rate is increased and the output is increased. Preferably, when the deformation rate of the conductive ball is 50 to 95%, the filling rate is further improved.

The conductive balls 42b located in the insulating region C are not deformed because they are not in contact with the wiring sheet 31 and the wiring 32, the main body 51 and the electrodes 52 and the like.

The manner of applying pressure and heat to the structure can be realized by a method other than lamination.

The contact area of the conductive ball 42a deformed into the elliptic sphere shape to the electrode 52 and the wiring 32 is increased as compared with that of the spherical shape. Thus, if the conductive ball 42a before pressure is in point contact with the wiring 32 and the electrode 52, the deformed conductive ball 42a comes into contact with the wiring 32 and the electrode 52 in the form of a plane The contact area is increased.

As the contact area increases, the contact area between the electrode 52 and the wiring 32 is reduced. Thus, the connection resistance which can be increased can be reduced to improve the fill factor (FF). The filling rate is a measure indicating how well the wiring 32 and the electrode 52 are electrically connected. If the wiring 32 and the electrode 52 are well connected by the conductive ball 40, the filling rate is increased.

As shown in Table 1 and Table 2, it can be seen that the charging rate is influenced by the magnitude of the force applied to the conductive balls and the degree of deformation thereof.

[Table 1] shows the results of the comparison of the filling rates according to the strains of the conductive balls having different strengths.

Table 1 above compares the filling rate by making a strain of the conductive ball 50% by applying a force of 100 mN or 120 mN to the conductive ball.

If the conductive ball has a strain of 50 mN or less at a force of 100 mN or less, the strength is loose. If the strain exceeds 50 mN at a force of 100 mN or less, the strength is relatively strong.

According to the above experiment, the strength of the conductive ball affects the module efficiency. If the size of the conductive balls is smaller than the interelectrode distance of the neighboring conductive regions and the conductive ball of this size is a soft one having a strain of 50% or more at a force of 100 mN or less, a highly efficient rear electrode type module can be manufactured. However, it can be seen that using a conductive ball having a strain of 50% at a force of 120 mN degrades the efficiency.

[Table 2] shows the results of an experiment in which the filling rates according to the conductive ball strain were relatively compared when the number of the conductive balls was the same.

In the above experiment, a conductive ball having a deformation strength of 50% or more was used at a force of 100 mN or less.

In Table 2, it can be seen that when the number and the strength of the conductive balls are the same, the filling rate increases from the conductive ball strain of 25% or more. When the strain exceeds 50%, there is no significant difference in the filling rate within 0.5%, but the filling rate increases slightly as the strain increases. The preferable strain of the conductive balls is 50 to 95%. That is, the greater the strain of the conductive ball, the lower the connection resistance, the better the filling rate, and the higher the output.

As shown in Table 3 below, the results of the experiment of changing the filling rate according to the size of the conductive balls. In this experiment, the strength and strain of the conductive balls belonging to the range of this embodiment were used.

In Table 3, when the filling rate of the rear electrode type solar cell module having the conductive ball size of 8 to 40 m was compared, when the size of the conductive ball was about 8 μm or more, the filling rate was high. High. However, it can be seen that the filling rate decreases when the size of the conductive balls is less than 8 탆 or exceeds 40 탆.

In addition, when the number of conductive balls is the same, when the size is less than 8 m, the contact area between the electrode 52 and the wiring 32 is small and the filling rate sharply decreases. When the size of the conductive ball exceeds 40 m, The pressure applied per unit area of the ball becomes smaller and the pressure is reduced, so that the filling rate is reduced due to the reduction of the contact area.

It is preferable to use a conductive ball having a size of 8 to 40 탆 according to the design conditions of the module, and the smaller the size of the conductive ball, the more the number of conductive balls can be increased.

Table 4 shows the results of experiments in which the conductive balls having the same strength and size as those of the present embodiment were used, but the filling rate was compared by changing the material of the conductive layer. In Table 4, it can be seen that there is almost no difference when the filling rate is compared in the case where the conductive layer of the conductive ball is formed of gold and that of the nickel is formed.

That is, a structure to which a spherical conductive ball having a size of 8 to 40 탆 is applied is subjected to a pressure of 0.05 MPa to 0.5 MPa in a closed space to form a conductive ball 25 To 95% strain to form an elliptical sphere shape, thereby forming the rear electrode type solar cell module in which the electrode and the wiring are connected to each other, the conductive layer material of the conductive ball is formed of nickel, Able to know.

The conductive layer may be formed of cheap nickel instead of expensive gold. In this way, the cost of the anisotropic conductive adhesive 40 can be reduced, and the cost of the rear electrode type solar cell module can be reduced.

The output is = Isc x Voc x charge rate. The filling rate is mainly changed by the resistance component, and Isc is mainly a change depending on the amount of light, and Voc is a change mainly depending on the kind of the substrate, the amount of the impurity, the p-n junction property, That is, the charge rate is checked in order to confirm whether the solar cell constituting the module is electrically connected. This is to remove the influence of other parameters such as the characteristics of the module or the temperature at the time of measurement. In the thermal cycle reliability test, the output can be measured to confirm the reliability result.

Referring to Table 5 below, a structure in which a spherical conductive ball having a size of 8 to 40 μm was applied to a conductive ball made of gold and nickel was placed in a closed space in a vacuum state, It can be seen that there is hardly any difference in energy output when light is given to the module under the condition that the conductive ball is deformed into an elliptical sphere shape with a strain of 25 to 95% by applying pressure to connect the electrode and the wiring.

[Table 5] compares the output reduction rate with the passage of the heat cycle according to the material of the conductive layer.

As a result of checking the thermal cycling reliability (T / C reliability), the difference between gold and nickel 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 balls meeting the conditions of the present embodiment, the conductive layer can be formed of nickel instead of gold, so that the cost of the anisotropic conductive adhesive can be reduced, .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

1: Rear electrode type solar cell module 10: Rear substrate
20: live part 21: first filler
22: second filler 30: wiring board
31: wiring sheet 32: wiring
40: Anisotropic conductive adhesive 41: Resin layer
42a, 42b: conductive balls 421a, 421b:
422a, 422b: conductive layer 50: battery cell
51: main body 52: electrode
60: front substrate

Claims (7)

A back plate, 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, the conductive ball electrically connecting the wiring and the electrode, Wherein the reduced diameter of the deformed ellipse of the conductive ball is smaller than the diameter of the deformed bulb by 25 To 95%. The method of claim 1,
A pressure of 0.05 MPa to 0.5 MPa was applied while keeping the vacuum cleaned space between the rear substrate, the wiring, the anisotropic conductive adhesive having the conductive balls, the battery cell having the electrode, and the front substrate in this order Wherein the diameter of the conductive balls is changed. The method of claim 1,
Wherein the conductive balls have a strain of 50 to 95% at a force of 100 mN or less. The method of claim 1,
Wherein the conductive ball includes a body and a conductive layer surrounding the body, and the conductive layer is made of nickel. The method of claim 1,
And the size of the conductive balls is 8 to 40 m. A step of forming a structure by laminating a back substrate, a wiring, an anisotropic conductive adhesive having conductive balls, a battery cell having electrodes, and a front substrate in this order,
Placing the structure in a vacuum state, and
Applying a pressure and a pressure of 0.05 MPa to 0.5 MPa to the structure placed in a vacuum state
Lt; / RTI >
Wherein the conductive ball placed in the conductive region where the wiring and the electrode face each other is deformed by the pressure and the minor axis diameter of the deformed conductive ball is 25 to 95%
A method of manufacturing a back electrode type solar cell module. The method of claim 6,
Wherein the conductive balls have a strain of 25 to 95% at a force of 20 to 100 mN.

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