KR101840591B1 - Circular wire for solar cell module - Google Patents

Abstract

The present invention relates to an annular wire for a solar cell module, and more particularly, to an annular wire for a solar cell module which can be stably fixed to a solar cell substrate to improve an output rate of the solar cell and can suppress cracking of the substrate when fixed to the solar cell substrate by soldering to extend life of a solar cell.

Description

[0001] The present invention relates to a circular wire for a solar cell module,

The present invention relates to an annular wire for a solar cell module. Specifically, the present invention minimizes contact resistance when attached to a solar cell substrate by soldering, maximizes the output of the solar cell, stably fixes the cell to the solar cell substrate, and suppresses cracking of the solar cell substrate The present invention relates to an annular wire for a solar cell module capable of extending the lifetime of a solar cell.

A solar cell is a device that converts light energy into electric energy by using p-type semiconductor and n-type semiconductor. When electrons and holes generated in the light are moved to the p- and n-poles respectively, Is a device that uses a photoelectric effect in which a potential difference (photovoltaic power) is generated and a current flows.

1 schematically shows a conventional solar cell module.

As shown in FIG. 1, in a conventional solar cell module, a plurality of solar cells 1, which is the minimum unit for generating electric power, are arranged in a panel, and the solar cells 1 And an annular wire 10 connected in series.

2 schematically shows a cross-sectional structure of an annular wire 10 used in a conventional solar cell module.

2, the annular wire 10 for a solar cell module includes a circular conductor 11 and a solder plated layer 12 formed on the surface thereof for connection with the solar cell 1, The annular wire 10 and the solar cell 1 are connected by cooling the solder plated layer 12 after the wire 10 is melted and placed on the substrate of the solar cell 1.

As shown in FIG. 2A, as the solder plated layer 12 has a sufficient thickness, the gap between the conductor 11 and the substrate is spaced apart, thereby increasing the contact resistance between the conductor 11 and the substrate When the total thickness of the solder plated layer 12 is reduced in order to reduce the contact resistance between the conductor 11 and the substrate as shown in FIG. 2B, the total solder There is a problem that the output of the solar cell module is lowered because the area of the plating layer is reduced and the annular wire 10 is not stably fixed to the substrate and is locally peeled off.

Accordingly, when the solar cell module is attached to the solar cell cell substrate by soldering, the contact resistance is minimized over the entire mounting surface, thereby maximizing the output of the solar cell module, stably fixing the solar cell cell substrate, There is a strong demand for an annular wire for a solar cell module that can extend the lifetime of the solar cell.

An object of the present invention is to provide an annular wire of a solar cell module in which the contact resistance is minimized when the solar cell module is attached to a solar cell cell substrate by soldering, thereby maximizing the output of the solar cell module.

It is another object of the present invention to provide an annular wire of a solar cell module which can be stably fixed to a solar cell cell substrate and can suppress cracking of the solar cell cell substrate, thereby prolonging the lifetime of the solar cell.

In order to solve the above problems,

An annular wire for a solar cell module, comprising: a circular conductor and a solder plated layer formed on a surface of the circular conductor, the diameter of the circular conductor being 180 to 540 탆, the cross sectional area of the circular conductor in any cross- Wherein the cross-sectional area ratio of the solder plated layer is 10 to 30%, and the circular conductor has at least one cross-section eccentric to one side.

Wherein each of the transversely sectioned eccentricities of the circular conductor has the same direction of eccentricity of the circular conductor.

Also, the eccentricity E defined by the following Equation 1 is 0.3 x the maximum eccentricity or more, and the maximum eccentricity is the sum of the eccentricity E defined by the following equation 1 in the transverse section eccentrically to one side of the circular conductor, Is an eccentricity (E) when the minimum thickness (T _min ) of the thickness of the wire is 0.5 占 퐉.

[Equation 1]

Eccentricity _{(E) = (T max -T} min) / d

In the above equation (1)

_Tmax and _Tmin are the maximum value (占 퐉) and the minimum value (占 퐉) of the thickness of the solder plated layer in the transverse section in which the circular conductor is eccentrically located at one side,

and d is the diameter (탆) of the circular conductor.

Further, the annular wire has a circularity having a difference in the maximum outer diameter (D _max ) and the minimum outer diameter (D _min ) of 11 mu m or less at any cross section.

The circular conductor is characterized by comprising a tough pitch copper (TPC), an oxygen-free copper (OFC), a phosphorus deoxidized copper, a low-oxygen copper or a high purity copper having a purity of 99.9999% To provide an annular wire.

Further, the solder plated layer contains 59 to 65 wt% of tin (Sn), 33 to 39 wt% of lead (Pb), 1.5 to 2.5 wt% of silver (Ag) By weight of lead (Pb), 33 to 43% by weight of lead (Pb), or 93.5 to 99.5% by weight of tin (Sn) and 0.1 to 3.5% by weight of silver (Ag).

Wherein the solder plated layer further comprises 0.002 to 0.034% by weight of bismuth (Bi) and 0.07 to 1.25% by weight of copper (Cu).

The present invention also provides an annular wire characterized in that the resistance is 648 m? / M or less, the yield strength is 120 MPa or less, the tensile strength is 180 to 260 MPa, and the elongation is 10 to 50%.

On the other hand, there is provided a solar cell module including a plurality of solar cell substrates and an annular wire for the solar cell module connecting the plurality of substrates in series.

Here, a silver (Ag) paste layer is formed on the portion where the annular wire is soldered on the solar cell cell substrate, and the silver (Ag) paste layer is formed on the silver And a plurality of silver (Ag) pads having a width larger than the width of the paste layer.

In addition, the size of the solar cell substrate is 4 to 8 inches, the number of the annular wires is 8 to 30, the width of the silver (Ag) paste layer is 30 to 70 탆, Wherein the interlayer spacing is 1.4 to 2.2 mm, the silver pad area is 500 to 900 탆 ² , and the number of silver (Ag) pads is 300 to 700.

The annular wire for the solar cell module according to the present invention may at least partially control the eccentricity of the circular conductor to one side so as to reduce the contact resistance between the annular wire and the solar cell cell substrate, And exhibit excellent effects.

In addition, the annular wire for a solar cell module according to the present invention can precisely adjust the thickness of the solder plating layer and can be stably fixed to the solar cell substrate by controlling the elongation, tensile strength, electric conductivity, Cracks can be suppressed and it is possible to prolong the lifetime of the solar cell.

1 schematically shows a conventional solar cell module.
2 schematically shows a cross-sectional structure of an annular wire used in a conventional solar cell module.
3 schematically shows a cross-sectional structure of an annular wire for a solar cell module according to the present invention.
FIG. 4 is a schematic view illustrating a state in which light is irradiated to a solar cell having an annular wire for the solar cell module shown in FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Like reference numerals designate like elements throughout the specification.

The annular wire 100 for a solar cell module according to the present invention includes a circular conductor 110 for connecting a plurality of solar cells in series as shown in FIG. 3, and a circular conductor 110 formed on the surface of the circular conductor 110, And a solder plated layer 120 for fixing the circular conductor 110 to the solar cell. Here, the annular wire 100 may have a circularity having a difference between a maximum outer diameter (D _max ) and a minimum outer diameter (D _min ) of 11 μm or less in an arbitrary cross section.

The annular wire 100 according to the present invention is formed by moving the circular conductor 110 into the coating die in the process of forming the solder plated layer 120 for manufacturing the circular conductor 110 at least partly, It is possible to implement one or more cross sections in which the circular conductor 110 is eccentric to one side as shown in FIG. 3, and preferably the circular conductor 110 Each of the eccentric cross-sections may have the same direction in which the circular conductor 110 is eccentric.

The annular wire 100 having at least one transverse cross-section in which the circular conductor 110 is eccentrically formed is disposed in a state in which the gap between the eccentric portion of the circular conductor 110 and the substrate is minimized The contact resistance between the circular conductor 110 and the substrate is minimized, and as a result, the output of the solar cell module can be maximized.

Also, it is easy to place the annular wire 100 on the substrate such that the spacing between the circular conductor 110 and the substrate is at least partially, preferably entirely minimized, along the length of the annular wire 100 It is possible to add a specific indication to the eccentric position of the circular conductor 110 in the surface of the annular wire 100 to do so.

In particular, the present inventors have found that the output of the solar cell module may differ depending on the degree of eccentricity of the circular conductor 110 in the annular wire 100, and the output of the circular conductor 110 defined by Equation (1) The output of the solar cell module sharply improves when the eccentricity of the solar cell module 110 is greater than or equal to a specific threshold value, that is, 0.3 x the maximum eccentricity (E _max ).

[Equation 1]

Eccentricity _{(E) = (T max -T} min) / d

In the above equation (1)

_Tmax and _Tmin are the maximum value (占 퐉) and the minimum value (占 퐉) of the thickness of the solder plated layer in the transverse section in which the circular conductor is eccentric in the annular wire,

and d is the diameter (탆) of the circular conductor.

The maximum eccentricity E _max is the eccentricity E when the minimum thickness Tmin of the thickness of the solder plating layer is 0.5 占 퐉 in the transverse section where the circular conductor is eccentric, that is, {T _max (= Dd-0.5) -T _min (= 0.5)} / d, where D is the total diameter of the annular wire, and T _max , T _min , D and d are values in the same cross section.

Since the eccentricity as a critical value for rapidly increasing the output of the solar cell module may differ depending on the diameter of the circular conductor 110 and the thickness of the solder coating layer 120, the eccentricity defined by Equation (1) (E _max ), which is variable depending on the diameter of the circular conductor 110 and the thickness of the solder coating layer 120, that is, 0.3 x the maximum eccentricity (E _max ).

The circular conductor 110 may be made of copper (Cu), aluminum (Al), silver (Ag), gold (Au) or the like. When copper (Cu) Tough Pitch Copper (TPC), Oxygen-Free Copper (OFC), Phosphrous Deoxidized Copper, low oxygen copper, high purity copper having a purity of 99.9999% or more, and a diameter of 180 to 540 탆 .

4, the annular wire 100 for a solar cell module according to the present invention adopts the circular conductor 110 as a conductor, and thereby, when fixed to the solar cell substrate by soldering, And when light is irradiated on the surface of the annular wire 100, irregular reflection is caused, and an excellent effect of maximizing the output of the solar cell is exhibited.

In addition, since the annular wire 100 for a solar cell module according to the present invention is locally contacted with the substrate when it is fixed to the solar cell substrate by soldering, the thermal expansion of the circular conductor 10 There is an effect that cracking of the substrate is relatively less caused by the difference between the coefficient and the thermal expansion coefficient of the substrate.

The solder plated layer 120 is formed of tin (Sn) as a main component and at least one of lead (Pb), silver (Ag), indium (In), bismuth (Bi), antimony (Sb), zinc (Zn) , Cu (copper), and the like in an amount of 0.1 wt% or more. For example, the solder plated layer 120 may contain 59 to 65 wt% of tin (Sn), 33 to 39 wt% of lead (Pb), 1.5 to 2.5 wt% of silver (Ag) By weight of lead (Pb), 33 to 43% by weight of lead (Pb), 93.5 to 99.5% by weight of tin (Sn) and 0.1 to 3.5% by weight of silver (Ag), further 0.002 to 0.034% by weight of bismuth (Bi) , Preferably 0.009 to 0.034 and 0.07 to 1.25 wt% of copper (Cu).

The bismuth (Bi) reduces the overall melting point of the solder composition and interacts with other components to melt and cool the solder plated layer 120 formed from the solder composition. The bismuth (Bi) And has a function of forming a sufficient adhesion width when attached to the cell substrate.

The content of bismuth (Bi) is less than 0.002 wt% based on the total weight of the solder composition, provided that the content of tin (Sn), lead (Pb), silver (Ag) The adhesion width between the solar cell substrate and the annular wire 100 due to melting of the solder plated layer 12 formed from the solder composition is excessively narrow so that the solar cell substrate and the annular wire 100 are locally separated The output of the solar cell module may be rapidly lowered. On the other hand, in the case of more than 0.034 wt%, the bonding strength between the annular wire 100 and the silver (Ag) paste on the solar cell substrate is increased (Ag) paste can be separated from the solar cell in the process of cooling and shrinking the annular wire 100 due to the difference in thermal expansion coefficient after soldering the solar cell substrate to the solar cell substrate. Said, this is due to the increase in resistance can be drastically reduced, the output of the solar cell module. In addition, if the Ag paste is not actually separated, the resistance of the unstable junction increases when the reliability test such as a thermal cycle test or a mechanical load test is performed, and the output rate of the solar cell module may be lowered .

On the other hand, the copper (Cu) improves the adhesion of the solder composition to the conductor of the annular wire 100 to improve the coating property of the solder composition, thereby uniformly forming the thickness of the solder plating layer 120 formed from the solder composition And the like.

It is preferable that the content of copper (Cu) is less than 0.07% by weight based on the total weight of the solder composition, provided that the contents of Sn, Pb, Ag and the like are as described above. The adhesion of the solder composition to the conductors constituting the annular wire 100 is rapidly lowered so that the solder plated layer 120 having a uniform thickness can not be formed. On the other hand, when the amount of the intermetallic compound in the plating bath exceeds 1.25% The thickness of the plated layer 120 of the annular wire 100, which is produced by forming a locally protruded plated layer called a plated hump on the surface of the annular wire 100 or an intermetallic compound adhered to the inside of the die hole, May occur.

The solder plated layer 120 may have a melting point of 110 to 230 캜 depending on the above-described components and mixing ratio, the sum of the minimum thickness and the maximum thickness on the same cross section of the annular wire may be 20 to 50 탆, Sectional area of the solder plating layer 120 may be 10 to 30%.

Meanwhile, the annular wire 100 for a solar cell module according to the present invention has a resistance of 648 m? / M or less, a yield strength of 120 MPa or less, a tensile strength of 180 to 260 MPa, and an elongation of 10 to 50% It can be stably fixed to the substrate when attached to the solar cell substrate, and can suppress the crack of the solar cell substrate, thereby prolonging the lifetime of the solar cell.

The present invention relates to a solar cell module including a plurality of solar cells including a silicon semiconductor substrate having a PN junction and an annular wire (10) for connecting the solar cells in series.

Here, the number of the annular wires 100 for the solar cell module may be different according to the desired electromotive force of the solar cell module, and silver (Ag) is formed on the portion where the annular wire 100 is soldered on the solar cell cell substrate. ) Paste layer is formed on the silver (Ag) paste layer, and a plurality of silver (Ag) paste layers having a width larger than the width of the silver (Ag) A silver (Ag) pad may be additionally provided.

For example, the size of the solar cell substrate may be 4 to 8 inches, the number of the annular wires 100 may be 8 to 30 on the basis of one solar cell cell substrate, ) Paste layer has a width of 30 to 70 占 퐉 and the adjacent silver (Ag) paste interlayer spacing is 1.4 to 2.2 mm, the silver (Ag) pad area is 500 to 900 占 퐉 ² and the number of silver (Ag) To 700 < / RTI >

[Example]

A solar cell module having the annular wire specimen and the solar cell to which the annular wire was applied, having the diameter, the plated layer / conductor cross-sectional area ratio, and the eccentricity, of the examples and comparative examples, respectively, I appreciated. Here, the eccentricity ratio is the lowest value among the respective eccentricity ratios in a plurality of transverse sections at intervals of 1 cm in the longitudinal direction of the annular wire specimen.

Conductor radius
(mm) Plating layer / conductor
Cross-sectional area ratio (%) 0.3 ×
Maximum eccentricity Plating layer thickness Eccentricity Print
(W) maximum at least Example 1




0.36
10
0.014 0.0120 0.0060 0.017 318 Example 2 0.0115 0.0065 0.014 320 Comparative Example 1 0.0110 0.0070 0.011 292 Comparative Example 2 0.0105 0.0075 0.008 291 Example 3
20
0.028 0.0230 0.0120 0.031 318 Example 4 0.0225 0.0125 0.028 319 Comparative Example 3 0.0220 0.0130 0.025 292 Comparative Example 4 0.0215 0.0135 0.022 291 Example 5
30
0.041 0.0330 0.0170 0.044 321 Example 6 0.0325 0.0175 0.042 320 Comparative Example 5 0.0320 0.0180 0.039 288 Comparative Example 6 0.0315 0.0185 0.036 288 Example 7


0.20
10
0.014 0.0070 0.0030 0.020 310 Example 8 0.0065 0.0035 0.015 311 Comparative Example 7 0.0060 0.0040 0.010 282 Comparative Example 8 0.0055 0.0045 0.005 283 Example 9
30
0.041 0.0190 0.0090 0.050 309 Example 10 0.0185 0.0095 0.045 310 Comparative Example 9 0.0180 0.0100 0.040 279 Comparative Example 10 0.0175 0.0105 0.035 281 Example 11


0.50
10
0.014 0.0160 0.0080 0.016 316 Example 12 0.0155 0.0085 0.014 315 Comparative Example 11 0.0150 0.0090 0.012 286 Comparative Example 12 0.0145 0.0095 0.010 285 Example 13
30
0.041 0.0460 0.0240 0.044 315 Example 14 0.0455 0.0245 0.042 313 Comparative Example 13 0.0450 0.0250 0.040 285 Comparative Example 14 0.0445 0.0255 0.038 286

As shown in Table 1, when the diameter of the circular conductor 110 is in the range of 200 to 500 占 퐉 and the ratio of the plated layer / conductor cross-sectional area is 10 to 30%, the eccentricity of the circular conductor 110 is 0.3 x maximum The annular wires of Examples 1 to 14 having eccentricity or more were found to maximize the output of the solar cell to 300 W or more by minimizing the contact resistance as a whole in the longitudinal direction when attached to the solar cell cell substrate while the eccentricity of the circular conductor 100 The annular wires of Comparative Examples 1 to 14 having a maximum eccentricity of less than 0.3 x were excessively spaced between the circular conductor and the substrate locally in the longitudinal direction when attached to the solar cell cell substrate, It was confirmed that the solar cell output dropped sharply to less than 300 W.

In particular, as shown in Table 1, it has been experimentally confirmed that the eccentricity of the circular conductor 110 induces a significant difference in the solar cell output before and after the maximum eccentricity of 0.3 x. Therefore, It is confirmed that the numerical limitation that the eccentricity of the conductor 110 is 0.3 x the maximum eccentricity or more has a critical significance.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. . It is therefore to be understood that the modified embodiments are included in the technical scope of the present invention if they basically include elements of the claims of the present invention.

110: circular conductor 120: solder plated layer

Claims (11)

An annular wire for a solar cell module,
A circular conductor and a solder plated layer formed on a surface of the circular conductor,
The diameter of the circular conductor is 180 to 540 탆,
Sectional area ratio of the solder plated layer to the cross-sectional area of the circular conductor in any cross-section of the annular wire is 10 to 30%
The circular conductor having at least one transverse section eccentrically to one side,
Each of the transverse sections of the circular conductor eccentrically formed on one side has an eccentricity (E) defined by the following equation (1)
Wherein the maximum eccentricity is an eccentricity (E) when the minimum thickness ( _Tmin ) of the thickness of the solder plated layer is 0.5 占 퐉 in a transverse section in which the circular conductor is eccentric to one side.
[Equation 1]
Eccentricity _{(E) = (T max -T} min) / d
In the above equation (1)
_Tmax and _Tmin are the maximum value (占 퐉) and the minimum value (占 퐉) of the thickness of the solder plated layer in the transverse section in which the circular conductor is eccentric,
and d is the diameter (탆) of the circular conductor. The method according to claim 1,
Wherein each of the transversely sectioned eccentric portions of the circular conductor has the same direction of eccentricity of the circular conductor. delete 3. The method according to claim 1 or 2,
Characterized in that the annular wire has a circularity with a difference between a maximum outer diameter (D _max ) and a minimum outer diameter (D _min ) of 11 m or less in any cross-section. 3. The method according to claim 1 or 2,
Characterized in that the circular conductor is made of tough pitch copper (TPC), oxygen-free copper (OFC), phosphorus deoxidized copper, low oxygen copper or high purity copper having a purity of 99.9999% Annular wire. 3. The method according to claim 1 or 2,
(A) from 59 to 65% by weight of tin (Sn), from 33 to 39% by weight of lead (Pb) and from 1.5 to 2.5% by weight of silver (Ag) based on the total weight of the solder plated layer, ) 56 to 66% by weight of tin (Sn) and 33 to 43% by weight of lead (Pb), or 93.5 to 99.5% by weight of tin (Sn) and 0.1 to 3.5% by weight of silver , Annular wire. The method according to claim 6,
Wherein the solder plated layer further comprises 0.002 to 0.034% by weight of bismuth (Bi) and 0.07 to 1.25% by weight of copper (Cu). 3. The method according to claim 1 or 2,
A resistance of 648 m? / M or less, a yield strength of 120 MPa or less, a tensile strength of 180 to 260 MPa, and an elongation of 10 to 50%. A solar cell module comprising a plurality of solar cell substrates and an annular wire for the solar cell module according to claim 1 or 2 connecting the plurality of substrates in series. 10. The method of claim 9,
A silver (Ag) paste layer is formed on the portion where the annular wire is soldered on the solar cell cell substrate, and the silver (Ag) paste layer is formed on the silver (Ag) paste layer to improve adhesion between the annular wire and the substrate. Wherein a plurality of silver (Ag) pads having a width greater than the width of the layer are further provided. 11. The method of claim 10,
(Ag) paste layer has a width of 30 to 70 mu m, and the adjacent silver (Ag) paste layer interlayer spacing is 4 to 8 inches, the number of the annular wires is 8 to 30, Wherein the silver (Ag) pad area is 500 to 900 占 퐉 ² , and the number of silver (Ag) pads is 300 to 700.

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