JP5016835B2 - Photoelectric conversion device and method of manufacturing photoelectric conversion device - Google Patents

Description

The present invention relates to a photoelectric conversion device such as an integrated solar cell and a manufacturing method thereof. The photoelectric conversion device of the present invention exhibits a particularly preferable effect when using lead-free solder for lead attachment.
Moreover, the manufacturing method of the photoelectric conversion apparatus of this invention is suitable as a manufacturing method of the photoelectric conversion apparatus which uses non-lead solder.

  Solar cells are attracting attention because they can generate power using inexhaustible solar energy, are clean without discharging exhaust gas, and are safe without danger of releasing radioactivity. Yes.

A solar cell has a glass substrate with a transparent electrode film (first electrode layer), a semiconductor film (solar cell film; actually composed of a p-layer, i-film, and n-film) and a back electrode film (second electrode). Layer) are sequentially stacked. When light is applied, a potential difference is generated between the first electrode layer and the second electrode layer.
However, the voltage generated by one solar cell is extremely low, and a single solar cell alone does not reach a practical voltage. Therefore, a device has been devised in which a plurality of grooves are provided in a thin film of a solar cell to divide it into a large number of unit cells (cells), and the cells of the large number of solar cells are electrically connected in series to increase to a practical voltage . Such a solar cell is called an integrated solar cell or an integrated thin film solar cell.

  In the integrated solar cell, lead attachment regions are provided on opposite sides of the substrate, and in one lead attachment region, the solder dip lead is soldered to the first electrode layer and / or the second electrode layer, and the other Also in the lead attachment region, the solder dip lead is soldered to the first electrode layer and / or the second electrode layer.

The solder dip lead attaching process in the manufacturing process of the integrated solar cell is generally as follows.
FIG. 13 is a cross-sectional view of an integrated solar cell showing a solder dip lead attaching step in the manufacturing process of a conventional integrated solar cell.
That is, as described above, a predetermined film 101 is formed on the glass substrate 100, a plurality of grooves are provided in the thin film, and the cells are divided into cells. After the cells are electrically connected in series, leads are attached to opposite sides of the substrate. Region 102 is provided (FIG. 13a).
Then, as shown in FIG. 13B, solder bumps 103 are formed in a row at predetermined intervals in the lead attachment region 102. Subsequently, as shown in FIG. 13C, a solder dip lead wire 105 having a solder coating applied to the solder bump 103 is placed. The solder dip lead 105 is placed in parallel with the substrate.
Subsequently, the hot iron 106 is brought close to the solder bump 103 as shown in FIG. 13D, and the solder bump 103 is pressed one by one with the iron 106 as shown in FIG.

  As a result, the solder 110 of the solder bump 103 is melted by the heat of the iron 106 and the solder dip lead wire 105 is joined. At this time, the mountain shape of the solder bump 103 collapses (FIG. 13f).

By the way, soldering is a joining technique that has been used for a long time as an electrical connection means for the solder dip lead 105, and eutectic solder having a tin / lead composition has been widely used as the solder. However, it is recognized that lead is toxic and has a great negative impact on the environment, including its impact on the human body, and its use is being regulated.
Therefore, solder that does not contain lead components or has a small composition of lead components (hereinafter referred to as non-lead solder)
The development of is urgent. For example, Patent Document 1 discloses a lead-free solder composed of 3 to 5% by weight of Ag, 0.5 to 3% by weight of Cu, and 0 to 5% by weight of Sb, with the balance being Sn.

Similarly, in the field of integrated solar cells, the use of lead-free solder has been studied (Patent Document 2).
JP-A-5-50286 JP 2002-314104 A

However, when lead-free solder is used for lead attachment of an integrated solar cell, there may be a problem that the attachment strength is inferior compared with the case where conventional lead solder is used.
Accordingly, the present invention focuses on the above-described problems of the prior art, and an object thereof is to develop a photoelectric conversion device having high lead attachment strength and a method for manufacturing the photoelectric conversion device.

In order to solve the above-described problems, the present inventors have intensively studied and changed variously the temperature of the iron, the amount of solder, the force when pressing the solder, etc. when soldering the solder dip lead to the electrode layer. We conducted experiments to solder the solder dip leads, and measured the mounting strength of each solder dip lead to examine the optimum conditions for soldering.
As a result, it was found that the attachment strength of the solder dip lead to the electrode layer has a correlation with the height of the solder, and that the attachment strength of the solder dip lead increases when the solder height is high to some extent.

  That is, it was estimated that the bonding strength between the solder dip lead and the electrode layer depends on the contact area between the solder, the solder dip lead and the electrode layer, but the bonding strength between the solder dip lead and the electrode layer is rather than the contact area. It was found that there was a strong correlation with the height of the solder.

A brief description is given below.
FIG. 14A is an enlarged cross-sectional view conceptually showing a lead attachment region of a solar cell in the prior art, and FIG. 14B shows a case where a solder dip lead is pulled in a direction perpendicular to the substrate. It is sectional drawing of the lead attachment area | region of the integrated solar cell which shows a behavior.
FIG. 15A is an enlarged cross-sectional view conceptually illustrating an integrated solar cell in which the height of the solder is higher than that in the conventional case. FIGS. 15B and 15C are views illustrating the solder dip lead with respect to the substrate. FIG. 6 is a cross-sectional view of a lead attachment region of an integrated solar cell showing the behavior when it is pulled in the vertical direction.
14 and 15 conceptually show the behavior of solder or the like, and a substrate including a film (a transparent electrode film, a semiconductor film, a back electrode film, etc.) is used as the substrate 100 for the sake of simplicity. In the following description, the substrate including the film formation may be referred to as the substrate 100 in some cases.

As described above, the inventors measured the mounting strength of the solder dip lead while changing the joining condition of the solder. The experiment was performed by pulling the solder dip lead in a direction perpendicular to the substrate.
In the conventional integrated solar cell, when the solder dip lead wire 105 is pulled, the solder 110 is peeled off from the substrate 100 side so as to follow the pulling up of the solder dip lead wire 105 as shown in FIG. The lead wire 105 is detached. Strictly speaking, the solder dip lead wire 105 is detached from the film 101 laminated on the substrate 100.

On the other hand, when the solder dip lead wire 105 is soldered by increasing the height H of the solder 110 and the solder dip lead wire 105 is pulled in the direction perpendicular to the substrate 100, the solder dip lead wire 105 shown in FIGS. Similarly, the interface between the solder 110 and the substrate (electrode film) 100 was peeled off at once, and the solder dip lead wire 105 was detached. That is, as shown in FIG. 15C, the solder dip lead wire 105 was detached with the solder 110 attached.
When the solder dip lead wire 105 is soldered by increasing the height H of the solder 110, the mounting strength of the solder dip lead wire 105 is several steps higher than that of the conventional one.

The reason for this is not clear, but when the lead mounting portion of the prior art is observed, the relationship between the end portion of the solder 110 and the solder dip lead wire 105 has a shape as shown in FIG. It is presumed that the shape is insufficient. Therefore, when the solder dip lead wire 105 is pulled in a direction perpendicular to the substrate 100, it is estimated that the tensile force may be concentrated on the solder connection end A on the substrate 100 side.
Alternatively, when the height of the solder 110 is low, the solder 110 is rapidly cooled and the solder 110 contracts, and residual stress is applied to the connection end portion between the solder dip lead wire 105 and the solder 110 and the interface between the solder dip lead wire 105 and the solder 110. It is presumed that the bonding strength between the two is reduced.

On the other hand, when the height H of the solder 110 is increased and the connection portion is observed with a microscope, a good fillet is formed at the end of the solder 110 and the solder dip lead 105 as shown in FIG. It was. That is, the solder 110 has a drum shape, the middle portion is thin, and both ends are larger in diameter than the middle portion. Therefore, when the solder dip lead wire 105 is pulled in a direction perpendicular to the substrate 100, it is estimated that the tensile force is distributed over the entire connection interface between the solder dip lead wire 105 and the solder 110.
Alternatively, it is presumed that if the height of the solder 110 is high, the cooling rate is lowered, and the residual stress at the interface between the solder dip lead 105 and the solder 110 is reduced.

  In any case, the present inventors have clarified that the mounting strength of the solder dip lead wire 105 is remarkably improved when the solder dip lead wire 105 is soldered by increasing the height H of the solder 110. .

The invention according to claim 1 based on the above knowledge is obtained by laminating at least a first electrode layer, a photoelectric conversion layer and a second electrode layer on a substrate, and applying light to the first electrode layer and the second electrode. In the photoelectric conversion device that generates a potential difference between the layers, a solder dip lead is soldered to at least one of the first electrode layer and the second electrode layer, and the material of the solder is non-lead solder, The solder before soldering is a solder bump having a diameter of 2.0 to 2.7 mm and a height of 0.2 to 0.5 mm. The solder of the soldered portion covers the solder dip lead from the laminated surface of the layer. all SANYO height to the surface of the 200~320μm solder layers, and solder shape of soldered portions is large area of the joint portion between the joint portion and the solder dipping leads the stacked surface portion, and features an intermediate portion is thin this That is a photoelectric conversion device.

  Here, the solder dip lead is a lead whose surface is covered with solder. Therefore, the solder dip lead is a combination of the core wire and the solder, and has a solder layer. The aforementioned “height to the solder dip lead” is the height to the solder dip lead including the solder layer, and is lower than the height to the core wire. That is, the above-described solder height is the height of the solder layer used for soldering, and does not include the solder layer originally attached to the solder dip lead.

  As the solder used for the solder bump, one having a lead content of less than 0.1% by weight is employed. Preferably, less than 0.05% by weight is employed.

  The invention according to claim 2 has a lead attachment region, and the solder dip lead is disposed in substantially parallel to the substrate in the lead attachment region, and the solder dip lead is provided on the first electrode layer or the second electrode layer. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is partially soldered.

  The solder dip lead is a core wire coated with solder. The solder covering the core wire is preferably a non-lead solder.

As described above, the invention according to claim 1 is characterized in that the solder shape of the soldering portion is such that the area of the joint portion between the laminated surface portion and the solder dip lead is large and the intermediate portion is thin. To do.

  In the photoelectric conversion device of the present invention, the solder shape of the soldered portion is such that the diameter of the bonded portion between the laminated surface portion and the solder dip lead is large, the area is large, and the intermediate portion is thin. The force relating to the solder dip lead is dispersed and transmitted to the substrate side. Therefore, the mounting strength of the solder dip lead is high.

  The invention relating to the manufacturing method includes a step of providing a solder bump, a step of placing a solder dip lead on the solder bump, and a heating pressing step of pressing a heating member against the solder bump. It is characterized by being stopped at a position away from the electrode layer by 100 μm or more.

  The photoelectric conversion device of the present invention has high solder dip lead attachment strength, can satisfy the mechanical strength of the joint portion between the solder dip lead and the substrate, and has an effect of high reliability. In addition, the photoelectric conversion device manufactured by the method for manufacturing a photoelectric conversion device of the present invention also has an effect of high solder dip lead attachment strength and high reliability.

Embodiments of the present invention will be further described below.
FIG. 1 is a perspective view of an integrated solar cell according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view taken along a line AA in FIG. FIG. 3 is an enlarged cross-sectional view of the BB part of FIG.
An integrated solar cell (hereinafter sometimes simply referred to as a solar cell) 1 of this embodiment includes an insulating translucent substrate 2 such as a glass substrate, a transparent conductive film (first electrode layer) 6 and a photoelectric conversion film 7. And a back conductive film (second electrode layer) 8 are laminated.
Moreover, the solar cell 1 is divided | segmented into the some photoelectric conversion cell 3 like FIG. When the solar cell 1 is observed in a plan view as shown in FIG. 1, lead attachment portions 50 and 51 are provided on opposite sides, and a strip-shaped solder dip lead wire 5 is attached to the lead attachment portions 50 and 51. ing.

2 and 3 are enlarged sectional views of the lead attachment portion. In the lead attachment portion 50 shown in FIG. 2, the solder dip lead wire 5 is attached to the back conductive film (second electrode layer) 8.
3, the solder dip lead wire 5 is attached to the transparent conductive film (first electrode layer) 6.
Here, the solder dip lead 5 is formed by coating a core 15 such as copper with solder 15 as shown in the circles of FIGS.

The solder dip lead wire 5 is attached by soldering using non-lead solder.
That is, in the lead attachment portion 50 shown in FIG. 2, solder bumps 9 that are in contact with the back conductive film (second electrode layer) 8 are provided in series and at regular intervals, and solder dip lead wires are provided on the solder bumps 9. 5 is attached.
Here, the matter to be noted in the present embodiment is the height H from the surface 52 of the multilayer body 53 to the surface of the solder dip lead wire 5 in the solder 20. In FIG. 2, the relation “H” for drawing and the arrow are illustrated at a position outside the solder 20 (the solder dip lead wire 5 stretched in a hollow shape), but the height H is the height of the solder 20. Now, it is not the position of the tensioned solder dip lead 5.

In the present embodiment, the transparent conductive film 6, the photoelectric conversion film 7, and the back conductive film 8 are laminated on the insulating translucent substrate 2. From the front surface 52 of the three-layer laminate 53, The height H reaching the back surface of the solder dip lead wire 5 is higher than the conventional one.
As described above, the solder dip lead wire 5 is formed by providing the solder layer 15 on the core wire 16 such as copper. The height of the solder layer 15 covered by the solder dip lead wire 5 is the height described above. Not included in H.
The reference on the upper end side of the height H is the surface of the solder layer 15 covered with the solder dip lead wire 5 as shown in FIG.
The reference on the upper end side of the height H is the surface of the back surface conductive film 8 of the multilayer body 53.

In other words, the height of the solder used for soldering is H.
And this height H is high compared with the past.
The above-described height H is based on the solder dip surface (coated surface) of the solder dip lead wire 5. Therefore, the position of the core wire 16 of the solder dip lead wire 5 is obtained by adding the thickness of the solder 15 coated to the height H. As will be described later, the thickness of the solder layer 15 provided on the solder dip lead 5 is about 10 to 80 μm, and usually 40 to 60 μm.
The height H is specifically a height exceeding 140 μm. The recommended height H is more than 140 μm and not more than 350 μm.
The most recommended range is 200 μm to 300 μm.

On the other hand, in the lead attachment portion 51 shown in FIG. 3, solder bumps 9 that are in contact with the transparent conductive film (first electrode layer) 6 are provided in series and spaced apart, and solder dip leads are provided on the solder bumps 9. Line 5 is attached.
Also in the lead attachment portion 51 shown in FIG. 3, the height H from the surface 52 of the multilayer body 53 in the solder 20 is higher than the conventional one. That is, also in the lead attachment part 51 shown in FIG. 3, the height from the surface of the back surface conductive film (second electrode layer) 8 to the back surface of the solder dip lead wire 5 is higher than the conventional one.
The height H is specifically 140 μm or more, and the recommended height H of the solder 20 is more than 140 μm and 350 μm or less. The most recommended range is 200 μm to 300 μm.

  In the embodiment described above, the negative side solder dip lead wire 5 is directly attached to the back surface conductive film (second electrode layer) 8, but the back surface conductive film (second electrode layer) 8 and the photoelectric conversion film 7 are scribed. A groove reaching the transparent conductive film (first electrode layer) 6 side may be provided, and the negative electrode may be taken out from the transparent conductive film (first electrode layer) 6 side. The structure in the case of taking out the negative electrode from the transparent conductive film (first electrode layer) 6 side is the same as that described in FIG.

Next, the manufacturing method of the solar cell of this embodiment is demonstrated.
FIG. 4 is a cross-sectional view of an integrated solar cell showing a solder dip lead attachment process in the manufacturing process of the integrated solar cell according to the embodiment of the present invention. FIG. 5 is a cross-sectional view of the integrated solar cell illustrating the heating and pressing step in more detail in the manufacturing process of the integrated solar cell shown in FIG.
Also for the solar cell of this embodiment, as in the prior art, a laminated body 53 in which a transparent conductive film 6, a photoelectric conversion film 7, and a back conductive film 8 are stacked on an insulating translucent substrate 2 such as a glass substrate is formed. The thin film is divided into cells by providing a plurality of grooves, and after the cells are electrically connected in series, lead attachment regions 50 and 51 are provided on opposite sides of the substrate 2 (FIG. 4a).
Then, as shown in FIG. 4B, solder bumps 9 are formed in a row at predetermined intervals in the lead attachment region. Subsequently, as shown in FIG. 4C, the solder dip lead wire 5 having the solder coating applied to the solder bump 9 is placed. The solder dip lead 5 is placed in parallel with the substrate 2.
Subsequently, as shown in FIG. 4D, the hot iron 55 is brought close to the solder bump 9, and the solder bump 9 is pressed one by one with the iron 55 as shown in FIG. A plurality of solder bumps 9 may be pressed at once using a larger iron.

Here, in the present embodiment, as shown in FIG. 5, a spacer 56 is interposed between the iron 55 and the substrate 2, and the position where the iron 55 stops is restricted. That is, the iron 55 presses the solder bump 9 to a position where it contacts the spacer 56.
The thickness of the spacer 56 determines the final height of the solder bump 9. The thickness of the solder dip lead wire 5 is taken into consideration, and then the surface 52 of the multilayer body 53 to the solder dip lead wire 5 is taken into consideration. The height H of the solder 20 is set to be in the range of 200 μm to 300 μm. That is, the thickness of the spacer 56 is obtained by adding approximately 200 μm to 300 μm to the thickness of the solder dip lead 5.

In the present embodiment, the solder 20 is melted by moving the hot iron 55 to the insulating translucent substrate 2 side. However, since the stop position of the iron 55 is determined, the height of the solder 20 becomes a constant value. Kept. Therefore, in the solar cell 1 manufactured by the manufacturing method of the present embodiment, the height of the solder 20 in the lead mounting portions 50 and 51 is high, and the mounting strength of the solder dip lead wire 5 is high.
In the above-described embodiment, the stop position of the iron 55 is regulated using the spacer 56. However, a stopper is provided on the mechanism side for operating the iron 55, or the iron 55 is operated by a robot to stop the position of the iron 55. You may let them.
It is also conceivable to use some sensor or the like to operate the iron 55 while measuring the height H of the solder 20 or to operate the iron 55 while monitoring the proximity distance to the substrate 2 with the sensor.
The stop position of the iron 55 is not necessarily coincident with the position of the height of the solder dip lead 5. According to the experiments by the present inventors, the iron 55 serving as a heating member is not less than 100 μm from the surface 52 of the laminate 53. It is desirable to stop at a distant position, and a more recommended stop position is in the range of 200 μm to 300 μm.

Although the outline of the present invention has been briefly described above, the structure of the solar cell 1 and the manufacturing method thereof according to the embodiment of the present invention will be described more specifically.
FIG. 6 is an explanatory diagram for explaining the integrated solar cell 1 according to the embodiment of the present invention. As shown in FIG. 6, the solar cell 1 is provided with a photoelectric conversion cell 3 that converts electric power on an insulating translucent substrate 2, and light incident from the insulating translucent substrate 2 side is converted into the photoelectric conversion cell 3. Is used for photoelectric conversion. Although a plurality of photoelectric conversion cells 3 are provided, the grooves and the like between the photoelectric conversion cells 3 are not shown.

The set of photoelectric conversion cells 3 is insulated from the surroundings by insulating wires 4 formed around the photoelectric conversion cells 3. The set of photoelectric conversion cells 3 has a structure for taking out the electric power generated through the solder dip lead wire 5 that has been solder dip.
Furthermore, a part of the structure in the cross-sectional direction of line A in FIG. 6 is shown in FIG. As shown in FIG. 7, the solar cell 1 is formed by sequentially laminating a transparent conductive film (first electrode layer) 6, a photoelectric conversion film 7, and a back electrode film (second electrode layer) 8 on a translucent substrate 2. It has the structure.
The solar cell 1 also has solder bumps 9 for connecting the solder dip lead 5 to the transparent conductive film 6, the photoelectric conversion film 7, and / or the back electrode film 8 in order to take out the generated electric power.

Next, each component of the solar cell 1 will be described.
As the insulating translucent substrate 2, for example, a glass plate or a transparent resin film can be used. As a glass plate, a large-area plate can be obtained at low cost, and has both transparency and high insulation, and both surfaces mainly composed of silicon dioxide (SiO ₂ ), sodium oxide (Na ₂ O) and calcium oxide (CaO) Smooth float plate glass can be used.
The transparent conductive film 6 can be composed of a transparent conductive oxide layer such as an ITO film, a tin dioxide (SnO ₂ ) film, or a zinc oxide (ZnO) film. The transparent conductive film 6 can be formed using a known vapor deposition method such as an evaporation method, a CVD method, or a sputtering method.

  The photoelectric conversion film 7 includes an amorphous and / or polycrystalline silicon-based semiconductor photoelectric conversion layer. For example, a p-type silicon-based semiconductor layer, an i-type silicon-based semiconductor layer, and an n-type silicon are formed from the transparent conductive film 6 side. It has a structure in which system-based semiconductor layers are sequentially stacked. These p-type semiconductor layer, i-type semiconductor layer, and n-type semiconductor layer can all be formed by a plasma CVD method. Moreover, a tandem structure in which these pin structures are stacked in two stages, a triple structure in which three stages are stacked, or the like may be used.

  The p-type semiconductor layer constituting the photoelectric conversion film 7 can be formed, for example, by doping silicon or a silicon alloy such as silicon carbide or silicon germanium with p conductivity type determining impurity atoms such as boron or aluminum. The i-type semiconductor layer can be formed of an amorphous silicon-based semiconductor material and a crystalline silicon-based semiconductor material, respectively. Examples of such a material include intrinsic semiconductor silicon (such as silicon hydride) and silicon carbide. In addition, silicon alloys such as silicon germanium can be fisted. In addition, if the photoelectric conversion function is sufficiently provided, a weak p-type or weak n-type silicon-based semiconductor material containing a small amount of a conductivity type determining impurity may be used. Furthermore, the n-type semiconductor layer can be formed by doping silicon or a silicon alloy such as silicon carbide or silicon germanium with n-conductivity determining impurity atoms such as phosphorus or nitrogen.

The back electrode film 8 not only has a function as an electrode, but also reflects light that enters the photoelectric conversion film 7 from the insulating translucent substrate 2 and reaches the back electrode film 8 and re-enters the photoelectric conversion film 7. It also functions as a layer. The back electrode film 8 can be formed to a thickness of, for example, about 200 nm to 400 nm by vapor deposition, sputtering, or the like using silver, aluminum, or the like.
A transparent conductive thin film (not shown) made of a nonmetallic material such as ZnO is provided between the back electrode film 8 and the photoelectric conversion film 7, for example, in order to improve the adhesion between them. be able to.

  The solder dip lead wire 5 is obtained by coating the core wire 16 with the solder 15 as described above. The solder covering the core wire 16 is preferably lead-free solder. Also, lead-free solder that can join a metal to an inorganic non-metal called ceramic solder is recommended. For example, solder composed of Sn, Zn, Sb, and Al, such as lead-free solder disclosed in Japanese Patent No. 3664308, can be used.

Alternatively, the solder 15 covering the core wire 16 includes at least one element selected from Ag, Al, Cu, Zn, Sb, In, Ge, P, Ni, and Bi, and the Sn content is 89% by weight. Solder having the above composition can also be used.
Further, as the solder, for example, solder having a composition of Ag 2.5 to 7.7 wt%, Cu 0.0 to 4.0 wt%, Sn 89 wt% or more, Zn 1.0 to 11 wt%, Sn 89 wt% or more Solder having a composition can be used. More preferably, the solder is composed of Ag 2.5 to 4.0% by weight, Cu 0.0 to 1.5% by weight, and Sn 89% by weight or more.

The solder dip lead wire 5 can be manufactured by immersing a copper foil in a melt of the above-described solder and coating the surface of the copper foil with the solder.
The thickness of the copper foil is preferably 40 μm to 120 μm, and more preferably 60 μm to 100 μm. The thickness of the solder coated on the surface of the copper foil is preferably 10 μm to 80 μm, and more preferably 20 μm to 60 μm. These solders have a lead content of less than 0.1% by weight. Preferably, less than 0.05% by weight is employed.

Since the solder bump 9 has a structure connected to the transparent conductive film 6 that is a transparent conductive oxide layer, the solder bump 9 is solder that can be soldered to metal oxide and is lead-free solder.
The solder material used for the solder bump 9 is preferably similar to the solder 15 covered with the solder dip lead 5 described above, such as lead-free solder disclosed in Japanese Patent No. 3664308, for example. , Solder composed of Sn, Zn, Sb, and Al can be used. The solder used for the solder bump 9 is also one having a lead content of less than 0.1% by weight. Preferably, less than 0.05% by weight is employed.
Also, it is possible to use a solder containing at least one element selected from Ag, Al, Cu, Sb, In, Ge, P, Ni, Bi, and having a total composition of Sn and Zn of 89% by weight or more. it can. Examples of the solder include a solder having a composition of Ag 2.5 to 7.7% by weight, Cu 0.0 to 4.0% by weight, and Sn 89% by weight, Zn 1.0 to 11% by weight, and a composition of Sn 89% by weight or more. Solder made of can be used. More preferably, the solder is composed of Ag 2.5 to 4.0 wt%, Cu 1.5 wt% or less, and Sn 89 wt% or more.
Flux can be added, but it may not be included.

Next, the manufacturing procedure of the solar cell of the embodiment will be described.
First, after forming the transparent conductive film 6 on one whole surface of the insulating translucent substrate 2, the first separation groove 10 that divides the transparent conductive film 6 into strips by, for example, irradiating YAG fundamental wave laser light. Form.
Next, over the transparent conductive film 6 in which the first separation groove 10 is formed, amorphous silicon and / or polycrystalline silicon is used as the photoelectric conversion film 7 in the order of p-type, i-type, and n-type by the plasma CVD method or the like. After being laminated more than once, for example, YAG second harmonic laser light is irradiated to form connection grooves 11 that divide the photoelectric conversion film 7 into strips.
Subsequently, after forming a transparent conductive thin film and a metal film as a back electrode film 8 over the photoelectric conversion film 7 in which the connection groove 11 is formed by a sputtering method or the like in this order, for example, YAG second harmonic laser light is insulated and transmitted. A second separation groove 12 that irradiates from the optical substrate 2 side and divides the back electrode film 8 into strips is formed.

In this way, a multilayer film including the transparent conductive film 6, the photoelectric conversion film 7 made of an amorphous and / or polycrystalline silicon-based semiconductor, and the back electrode film 8 sequentially stacked on one surface of the insulating translucent substrate 2. And a cell region including a plurality of photoelectric conversion cells connected in series is formed.
Furthermore, a solder dip lead wire 5 for taking out electric power is arranged on the solar cell 1. For example, the YAG second harmonic laser beam is irradiated from both sides of the photoelectric conversion cell 3 indicated by the broken lines B and C in FIG. 8 from the insulating translucent substrate 2 side, and the photoelectric conversion film 7 and the back electrode film 8 is removed, and the lead connection groove 13 having the shape shown in FIG. Solder bumps 9 are formed from the photoelectric conversion cell 3 side as shown in FIG.
The shape of the solder bump 9 is fixed to the transparent electrode layer 6 as shown in FIG. 11, fills the connection groove 13, and protrudes from the photoelectric conversion cell 3. A solder dip lead wire 5 is attached to the formed solder bump 9 using a heated soldering iron 55, and as shown in FIG. 7, a structure in which the solder dip lead wire 5 for power extraction is arranged on the solar cell 1 is provided. Can be made.

The first method for producing the solder dip lead 5 for taking out the power is, for example, an ultrasonic vibrator and a soldering iron directly connected to the ultrasonic vibrator and having an electric heater inside (hereinafter referred to as ultrasonic soldering). Is used). That is, using an ultrasonic soldering iron, the solder 20 used for the solder bump 9 is melted and adhered to and held on the ultrasonic soldering iron. The vibration generated by the ultrasonic vibrator is applied to the ultrasonic soldering iron. In the transmitted state, the solder bump 9 is formed by pressing against the position of the connection groove 13. In this case, the temperature of the heated ultrasonic soldering iron is 20 ° C. to 300 ° C. from the melting point of the solder 20 used for the solder bump 9 (indicating liquid phase temperature when liquid phase temperature and solid phase temperature are present). (Celsius) High range. The temperature of the ultrasonic soldering iron is more preferably in the range of 40 ° C. to 200 ° C. higher than the melting point of the solder 20 used for the solder bumps 9.
When the temperature of the ultrasonic soldering iron is close to the melting point of the solder 20 used for the solder bump 9, the melting rate of the solder 20 is slow, and the productivity may be lowered.
Further, if the temperature of the ultrasonic soldering iron is too high, the oxidation of the solder 20 proceeds and the quality may be impaired.

As a second stage, a soldering iron heated by an electric heater (hereinafter referred to as a soldering iron for a lead wire) is pressed from the solder dip lead wire 5 side to be melted and connected to the solder bump 9. In this case, the temperature of the lead wire soldering iron is in the range of 20 ° C. to 300 ° C. higher than the melting point of the solder 20 used for the solder dip lead wire 5. A further recommended temperature difference is 40 ° C to 200 ° C.
If the temperature of the soldering iron for the lead wire is close to the melting point of the solder 20 used for the solder dip lead wire 5, the melting rate of the solder 20 is slow and the productivity may be lowered. Further, if the temperature of the lead wire soldering iron is too high, the oxidation of the solder 20 proceeds and the quality may be impaired.
The difference in melting point between the solder 20 used for the solder bump 9 and the solder 20 used for the solder dip lead 5 is in the range of 0 ° C to 100 ° C, preferably 0 ° C to 50 ° C, more preferably. 0 ° C to 20 ° C. When the solder dip lead wire 5 is attached to the solder bump 9, it is possible to suppress the solder bump 9 from being held in a molten state more than necessary, and the mechanical strength of the joint portion between the solder bump 9 and the transparent electrode layer 6 from being lowered. . Further, the melting point of the solder 20 used for the solder bump 9 is preferably higher than that of the solder 20 used for the solder dip lead wire 5.

  Further, in the process of attaching the solder dip lead wire 5 to the solder bump 9 with a lead wire soldering iron, in order to improve the yield of melting and connection between the solder dip lead wire 5 and the solder bump 9, the solder dip lead wire 5 A heating process can be made into two steps or more. That is, after heating the whole or a part of the solar cell 1, the solder dip lead wire 5 is attached to the solder bump 9 with a lead wire soldering iron. In this case, the entire solar cell 1 may be heated, the lead attachment portion including the solder bump 9 may be heated, or the solder dip lead wire 5 may be heated. Preferably, the solder dip lead wire 5 is heated. The heating temperature is preferably 20 to 200 ° C. More preferably, it is 40-150 degreeC. Moreover, the number of stages in the heating process is preferably 2 to 3 stages. Two steps are particularly preferred.

Further, as a matter of special mention here, a spacer (not shown) is interposed between the lead wire soldering iron and the insulating translucent substrate 2, and the closest position of the lead wire soldering iron is regulated.
For this reason, the solder bumps 9 are melted by receiving heat from the lead wire soldering iron, but are less crushed than conventional solder bumps. The height of about 300 μm is maintained.

In this way, the solar cell 1 having the solder dip lead wire 5 for taking out electric power is formed.
For the purpose of protecting the solar cell 1 used in an outdoor environment, a protective film is sealed from the photoelectric conversion cell 3 side. The protective film is firmly adhered to the solar cell 1 through a sealing resin that can be cured through heating and softening / melting.

Examples of such a protective film include a fluororesin film such as a polyvinyl fluoride film (for example, Tedlar film (registered trademark)), an organic film such as a polyethylene terephthalate (PET) film, and a metal foil made of aluminum or the like. A laminated film having a structure laminated in a single layer structure or a multilayer structure. Examples of the sealing resin that can be cured by heating and softening / melting include, for example, ethylene / vinyl acetate copolymer (EVA), ethylene / vinyl acetate / triallyl isocyanurate (EVAT), polyvinyl butyral (PVB), A crosslinking agent such as a peroxide compound is added to a thermoplastic resin such as polyisobutylene (PIB). In addition, when the protective film is attached to the solar cell 1 in this way, the internal wiring using the solder dip copper foil, the metal foil, the cable, etc., and the external wiring agent such as the terminal box, the solder dip lead wire for taking out the power is used. The obtained electric power is taken out to the outside.
Moreover, when using a solder material for the internal wiring agent, it is preferable to use lead-free solder.

Hereinafter, although the present invention is explained in detail based on some examples, the present invention is not limited to the following description examples unless it exceeds the purpose.
A solar cell 1 was produced according to the above-described embodiment.
First, on the glass substrate 2 having an area of 980 mm × 950 mm and a thickness of 5 mm, a tin dioxide (SnO ₂ ) film having a thickness of about 700 nm was formed as the transparent conductive film 6 by a thermal CVD method. By irradiating a YAG fundamental wave laser beam from the tin dioxide (SnO ₂ ) film side, the first separation groove 10 was formed by patterning.

Next, after fine powders and the like generated by the processing were washed away, the glass substrate 2 was carried into a plasma CVD film forming apparatus, and a photoelectric conversion film 7 made of amorphous silicon having a thickness of about 300 nm was formed. After unloading the glass substrate 2 from the CVD apparatus, the connecting groove 11 was formed by irradiating the photoelectric conversion film 7 with YAG second harmonic laser light from the glass substrate 2 side.
Next, as a back electrode film 8, a ZnO film having a thickness of about 80 nm and an Ag film having a thickness of about 300 nm were formed on the photoelectric conversion film 7 in this order by a sputtering method. Furthermore, the back electrode film 8 was irradiated with YAG second harmonic laser light from the glass substrate 2 side, and divided into strips to form second separation grooves 12.

In order to insulate the cell region and the connection region from the periphery of the glass substrate 2, YAG laser light is irradiated along the periphery of the glass substrate 2 to form the SnO ₂ film, the amorphous silicon photoelectric conversion film 7, and the back electrode film 8. The insulating wire 4 was formed by removing. As described above, a solar battery in which 108 photoelectric conversion cells 3 having an area of approximately 82.67 cm ² were connected in series was obtained.
Next, Sn / Zn ceramic solder was used as the solder 20 of the solder bump 9.
Forty-six solder bumps 9 were formed at 20 mm intervals in the connection groove 13 at a solder melt adhesion portion (tip point) diameter of 1 mm, ultrasonic soldering iron temperature of 300 ° C., ultrasonic output of 3 W, and soldering time of 1 s. The formed solder bumps 9 had a diameter of 2.0 to 2.7 mm and a height of 0.2 to 0.5 mm (200 μm to 500 μm).
Next, the solder dip lead wire 5 and the solder bump 9 were melted and connected using a lead wire soldering iron. The lead wire was coated with Sn / Ag / Cu solder.
The thickness of the copper foil constituting the solder dip lead wire 5 was 80 μm and the width was 2 mm. The temperature of the lead soldering iron was set to 300 ° C. The lead soldering iron was pressed against the solder dip lead wire 5, and the solder dip lead wire 5 and the solder bump 9 were melted and connected.

In addition, a spacer 56 is interposed between the lead soldering iron and the substrate 2 to regulate the distance at which the lead soldering iron is closest to the substrate 2. Various thicknesses of the spacers 56 were changed, and the solar cells 1 having different solder 20 heights at the solder dip lead wires 5 were produced.
As a result, the height of the solder 20 at the site of the solder dip lead wire 5 (height exposed from the film and extending to the back surface of the core wire of the solder dip lead wire 5) H is as shown in Table 1. It was. The value of H in the table is an average value of 20 points extracted at random.

Subsequently, the 90 ° (degree) tensile strength (tensile speed 1 mm / s) of the attached solder dip lead wire 5 was measured. The results are shown in Table 1. In addition, the value of the tensile strength in the table is an average value of 46 points.
The relationship between the tensile strength and the solder height H is as shown in the graph of FIG.
From Table 1 and the graph, it can be understood that the connection strength of the solder dip lead wire is high when the height from the laminated surface to the solder dip lead wire exceeds 140 μm, particularly when the height is 170 μm or more.
Although not shown in the table or graph, when the solder height was 0 μm to 20 μm, the solder dip lead wire was detached at the interface with the solder, and the mounting strength was low. When the solder height was 80 μm, 120 μm, and 140 μm, peeling occurred in order to follow the solder dip lead wire.

  On the other hand, when the solder height was 200 μm or more, the solder joints were peeled off at a stretch. From this experimental data, it can be seen that when the solder height H exceeds 140 μm, preferably about 170 μm or more, the bonding strength of the solder dip lead wire is dramatically improved. There is a thickness that dramatically increases the strength of the solder between 140 μm and 200 μm, and the critical value is considered to be 170 μm.

When the solder height exceeded 350 μm, the soldering condition was poor.
As shown in Table 1, the 90 ° tensile strength of the solder dip lead wire markedly increased when the solder height was 250 μm or more, and peaked around 280 μm.
Also, when the shape of the solder is observed, in the solder height H shown in Table 1, when the solder height is 200 μm or more, the solder shape is a drum shape, the middle part is thin, and both end parts are The diameter was larger than the middle part.

1 is a perspective view of an integrated solar cell according to an embodiment of the present invention. It is an expanded sectional view of the AA part of FIG. It is an expanded sectional view of the BB part of FIG. It is sectional drawing of the integrated solar cell which shows the attachment process of the solder dip lead wire in the manufacturing process of the integrated solar cell of embodiment of this invention. It is sectional drawing of the integrated solar cell which demonstrated the heating press process in detail in the manufacturing process of the integrated solar cell shown in FIG. It is a top view of the integrated solar cell for demonstrating the integrated solar cell of embodiment of this invention. It is an expanded sectional view in the A line of FIG. It is a top view of the integrated solar cell for demonstrating the process step of the integrated solar cell of embodiment of this invention. It is an expanded sectional view in the A line of FIG. It is a top view of the integrated solar cell for demonstrating the process step of the integrated solar cell of embodiment of this invention. It is an expanded sectional view in the A line of FIG. It is a graph which shows the relationship between the height of the solder in the attaching part of a solder dip lead wire, and attachment strength. It is sectional drawing of an integrated solar cell which shows the attachment process of the solder dip lead in the manufacturing process of the integrated solar cell of a prior art. (A) is an enlarged cross-sectional view conceptually illustrating a lead attachment region of a solar cell in the prior art, and (b) is a behavior when an attempt is made to pull the solder dip lead in a direction perpendicular to the substrate. It is sectional drawing of the lead attachment area | region of the integrated solar cell which shows. FIG. 15A is an enlarged cross-sectional view conceptually illustrating an integrated solar cell in which the height of the solder is higher than that of the conventional solder. FIGS. 15B and 15C are views illustrating the solder dip lead with respect to the substrate. It is sectional drawing of the lead | attachment area | region of an integrated solar cell which shows the behavior at the time of trying to pull to a perpendicular direction.

1 Solar cell (photoelectric conversion device)
2 Insulating translucent substrate 3 Photoelectric conversion cell 5 Solder dip lead 6 Transparent conductive film (first electrode layer)
7 Photoelectric conversion film 8 Back surface conductive film (second electrode layer)
9 Solder bump 20 Solder 50, 51 Lead mounting portion 52 Surface of laminated film 55 Iron (heating member)

Claims (3)

In the photoelectric conversion device that causes at least a first electrode layer, a photoelectric conversion layer, and a second electrode layer to be laminated on a substrate and generates a potential difference between the first electrode layer and the second electrode layer by applying light, Solder dip leads are soldered to at least one of the first electrode layer and the second electrode layer, the material of the solder is non-lead solder, and the solder before soldering has a diameter of 2.0-2. A solder bump having a height of 0.2 to 0.5 mm at 7 mm, and the solder of the soldered portion has a height of 200 to 320 μm from the layered surface of the layer to the surface of the solder layer covered with the solder dip lead. der ones is, and the solder in the form of soldered parts, large area of the joint portion between the joint portion and the solder dipping leads the stacked surface portion, a photoelectric conversion device comprising an intermediate portion is thin this.   A solder dip lead is disposed in the lead attachment region and substantially parallel to the substrate, and the solder dip lead is partially soldered to the first electrode layer or the second electrode layer. The photoelectric conversion device according to claim 1, wherein: 3. The method of manufacturing a photoelectric conversion device according to claim 1, wherein a step of providing a solder bump, a step of placing a solder dip lead on the solder bump, and a heating pressing step of pressing a heating member against the solder bump. And a method of manufacturing a photoelectric conversion device, wherein the heating member is stopped at a position separated by 100 μm or more from the electrode layer in the heating and pressing step.

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