JPH1121660A - Connection line for solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in an effective power generating area caused by flow-out of molten solder to out of an Ag coated range of an Si wafer by making at least one surface of a Cu rod flat and forming solder coated layer on this surface as arch state of the cross section. SOLUTION: For example, both surfaces of the Cu rod 1 having about 125 μm thickness (t) and about 1.5 mm width W are made flat and on both surfaces thereof, the arch state solid coated layers 2a, 2b having about 1.0-50 μm the max. thickness of the center position are arranged. The solder coated layers 2a, 2b can be formed by dipping the lower part of a die having a gap according to the thickness of solder coated layer into the solder bath having the surface covered with non-oxidizing gas, passing the Cu rod into this die, pulling up and forming the stuck solder as the arch state by surface tension. This connecting line is arranged in the Ag coated range of the Si wafer and pressurized while heating, and then, the solder is fluidized to break the oxide film, and the good soldering is executed by flowing to the whole body of the contacting surface with a little quantity of the solder while exhausting gas bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a connection line for a solar cell, and more particularly to a solder plating connection line connected to a silicon (Si) wafer of a solar cell.

[0002]

2. Description of the Related Art FIG. 5 shows a Si wafer 20 constituting a solar cell.
0 is connected. FIG. 6A shows a solder plating connection line 10, wherein a smooth solder plating layer 2 is formed on both surfaces of a Cu strip 1.
a, 2b are formed. The thickness t 1 of the Cu strip ₁ is, for example, 125 μm, and the width W is, for example, 1.5 mm.
It is. Also, the thickness t of the solder plating layers 2a, 2b
₂ is, for example, 20 to 30 μm. FIG. 6B shows a state where the solder plating connection wire 10 is connected to the Ag plating area 3 of the Si wafer 20. In this connection, the solder plating connection line 10 is arranged in the Ag plating region 3 of the Si wafer 20, and the solder plating connection line 10 is pressed and heated to such an extent that the Si wafer 20 is not damaged. Si wafer 2
0 is connected to the Ag plating region 3.

[0003]

However, according to the conventional connection line for a solar cell, as shown in FIG. 6B, the solder plating layers 2a and 2b melt and flow to exceed the Ag plating region 3. As a result, the solder inflow portion 2c becomes Si
Since it covers the effective power generation area of the wafer 20,
The power generation efficiency will be reduced. To prevent this,
When the thickness of the solder plating layers 2a and 2b is reduced, the solder flow is insufficient at the time of melting due to the small capacity of the solder, so that the oxide film formed on the surfaces of the solder plating layers 2a and 2b does not break well, and the solder covers the entire contact surface. It does not flow well and also traps bubbles to increase the connection resistance and lower the output efficiency of generated power.

Accordingly, it is an object of the present invention to provide a connection line for a solar cell in which molten solder does not flow beyond the Ag plating area of a Si wafer.

Another object of the present invention is to provide a connection line for a solar cell which suppresses a decrease in effective power generation area and prevents a decrease in power generation efficiency.

Another object of the present invention is to provide a connection line for a solar cell in which an oxide film formed on a surface of a solder plating layer is surely broken so that solder flows over the entire contact surface.

Another object of the present invention is to provide a connection line for a solar cell which reduces the connection resistance by eliminating the confinement of air bubbles and increases the output efficiency of generated power.

[0008]

In order to achieve the above object, the present invention provides a Cu strip having at least one flat surface,
A connection line for a solar cell, comprising a solder plating layer having an arc-shaped cross section formed on the one surface.

According to another aspect of the present invention, there is provided a solar cell comprising a Cu strip having a flat surface on both sides, and a solder plating layer having an arc-shaped cross section formed on both sides. Provide connection lines for

[0010]

FIG. 1 shows a first embodiment of a connection line for a solar cell according to the present invention, in which a Cu strip 1 having a thickness t of 125 μm and a width W of 1.5 mm is formed. It is composed of arc-shaped solder plating layers 2a and 2b formed on both surfaces. The solder plating layers 2a and 2b have w /
2 has a maximum thickness of 1.0 to 50 μm at the center position A. According to this, the capacity of the solder in the solder plating layers 2a and 2b is reduced as compared with the conventional case shown in FIG.

FIG. 2A shows a state in which the connection lines for the solar cell shown in FIG. 1 are arranged in the Ag plating region 3 of the Si wafer 20. In this state, when a pressure P is applied to the center position A while heating, a solder flow F is generated, whereby the oxide film on the surface of the solder plating layer 2b is broken, and S
Connected to Ag plating area 3 of i-wafer 20. When the solder flow F occurs, in addition to the destruction of the oxide film described above, it becomes possible to drive out the destructed oxide film, bubbles and dirt, and a fresh face-to-face bonding is performed. FIG. 2B shows a state of connection by the joining method of FIG.
Since the above facilitates the joining, the solder plating layer 2
As a result, the capacity of the solders a and 2b can be reduced, and as a result, the molten solder does not exceed the inside of the Ag plating region 3, and the effective power generation area of the Si wafer 20 does not decrease.

FIG. 3 shows a second embodiment of a connection line for a solar cell according to the present invention, in which solder layers 2a and 2b having two arc surfaces are formed on both surfaces of a Cu strip 1 having a thickness t and a width W. It is configured. When this connection line for a solar cell is connected to the Ag plating region 3 of the Si wafer 20 shown in FIG. 2A, solder flows F ₁ and F ₂ are generated in the solder plating layer 2b, so that the first embodiment is used. As before, the desired connection is obtained.

FIG. 4 shows an apparatus for manufacturing a connection line for a solar cell according to the present invention. A solder bath whose surface is covered with a non-oxidizing gas (for example, a common 60Sn-40Pb solder or Sn- 3.5% Ag-0.7% Cu, Sn-2.0
% Ag-7.5% Bi-0.5% Cu, etc.) and a die 4 arranged in the solder bath 2. The die 4 has an interval g corresponding to the thickness of the solder plating layers 2a and 2b formed on both sides of the Cu strip 1 between the die 4 and the level H ₂ of the exit of the solder bath 2. which is below the bath surface H _1. Solder plating layer 2
The shapes of the arc surfaces a and 2b are as follows: the width W of the Cu strip 1, the temperature of the solder bath, the pulling speed of the Cu strip 1, the die 4 and the Cu strip 1
, The shape of the dice 4 and the surface tension of the solder. Among them, the influence of the surface tension of the solder is the largest.

The connection line for a solar cell manufactured by the apparatus shown in FIG. 4 is free from aging and has excellent bonding characteristics as compared with the one manufactured by electroplating. Since the solder layer becomes porous in those manufactured by electroplating, aging occurs. To prevent this, the solder layer must be heated and melted after electroplating.

In the above embodiment, Sn is used as the solder.
-Pb type was used.
b-free solder can be used. Further, although the configuration is such that the solder layer is formed on both sides of the Cu strip, it may be formed on only one side. Further, although the Cu strip is manufactured from tough pitch copper, oxygen-free copper, or the like, it may be used as it is, or may be plated with Sn, Ag, Ni, or the like.

[0016]

As described above, according to the solar cell connection line of the present invention, since the solder layer having the arc surface is formed on the flat joint surface of the Cu strip, the maximum thickness can be controlled. Solder can be accurately prevented from flowing beyond the Ag plating area of the Si wafer, whereby a decrease in the effective power generation area of the Si wafer can be suppressed and a decrease in power generation efficiency can be prevented. Also, since a solder flow is formed in the molten solder layer at the time of joining, destruction and discharge of the oxide film and discharge of bubbles are reliably performed, thereby obtaining a connection portion having a small contact resistance and increasing generated power. It can output with efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a connection line for a solar cell according to the present invention.

FIG. 2A is an explanatory diagram showing a state when a solar cell connection line is connected according to the first embodiment of the present invention. (B) Explanatory drawing which shows the state after connection of the connection line for solar cells of 1st Embodiment of this invention.

FIG. 3 is a cross-sectional view showing a second embodiment of the connection line for a solar cell of the present invention.

FIG. 4 is an explanatory view showing a manufacturing apparatus for manufacturing the connection line for a solar cell according to the first embodiment of the present invention.

FIG. 5 is an explanatory view showing a state in which a solar cell connection line is connected to a solar cell Si wafer.

FIG. 6A is a sectional view showing a conventional connection line for a solar cell. (B) Sectional drawing which shows the connection state of the conventional connection line for solar cells.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cu strip 2 Solder bath 2a, 2b Solder plating layer 2c Solder inflow part 3 Ag plating area 4 Dice 10 Connection line for solar cells 20 Si wafer for solar cells

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayoshi Aoyama 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Power Systems Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Takaro Ichikawa 5 Hidaka-cho, Hitachi City, Ibaraki Prefecture Hitachi Power Systems Research Institute, Hitachi Cable Co., Ltd. (72) Inventor Hiroyuki Akutsu 4-1-1 Kawajiri-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Cable Co., Ltd.

Claims (6)

[Claims] 1. A connection line for a solar cell, comprising: a Cu strip having at least one surface flat, and a solder plating layer having an arc-shaped cross section formed on the one surface. 2. A connection line for a solar cell, comprising: a Cu strip having both surfaces made flat; and a solder plating layer having an arc-shaped cross section formed on both surfaces. 3. The connection line for a solar cell according to claim 2, wherein said Cu strip has both side surfaces exposed or covered with a thin solder plating layer. 4. The connection line for a solar cell according to claim 2, wherein said Cu strip has one surface of said both surfaces joined to an Ag plating region of a silicon (Si) wafer by melting said solder plating layer. 5. The connection line for a solar cell according to claim 4, wherein the solder plating layer is configured not to reach the power generation region beyond the Ag plating region of the wafer due to melting. 6. The connection line for a solar cell according to claim 1, wherein the solder plating layer is made of a lead-free solder.