Patent Application
20090001140
This invention relates to a method for soldering an interconnector to a photovoltaic cell, in the process of manufacturing a photovoltaic module, which makes it possible to significantly inhibit or almost eliminate deformation of the photovoltaic cell due to the heat of the soldering when soldering the interconnector (hereinafter, referring also to as “lead wire”) to the photovoltaic cell (hereinafter, simply referring to as “cell”) that forms the module.
Conventionally, in order to attach the interconnector to the photovoltaic cell, the interconnector is welded by solder which is previously coated to the interconnector and is thereafter cooled at room temperature so as to be soldered.
It has been known that if the interconnector is soldered to the photovoltaic cell, warp is resulted in the photovoltaic cell due to the difference of the coefficient of thermal expansion between the cell and the interconnector or the like.
The photovoltaic module technical field is recently making progress in the direction in which the thickness of the photovoltaic cell is reduced; thus, the warping of the cell side resulted by the soldering of the interconnector has become one of the important problems to be solved.
That is, for the conventional photovoltaic cell having sufficient thickness and strength in the cell itself, since a force generated by thermal strain intending to warp the cell side on the basis of the difference of coefficient of thermal expansion between the photovoltaic cell and the interconnector is also absorbed by the strength in the cell side, there is no resultant warp, and even if the warp is resulted no large warp can be resulted.
However, in the recent photovoltaic cell in which the cell itself is thinly formed, the cell tends to be deformed after soldering the interconnector, and the cell may be cracked in the case where the deformation occurs, as described above.
Further, if the photovoltaic cell, in which the warp is resulted, is processed to the photovoltaic module, the deformation such as the warp or the like is mechanically corrected right at the time of processing, the deformation forms a stress applied to the cell so as to cause a crack, and the crack can also be caused at the time of handling the photovoltaic cell, in which the deformation such as the warp or the like is resulted, to the next process.
The cost of the photovoltaic cells is extremely high in consideration of the cost of the entire photovoltaic module, and there are problems that the defect due to cracking not only causes reduction of the productivity but also increases the overall cost for the defective work.
On the other hand, since the soldering work of the interconnector is achieved by positioning the interconnector constituted by a fine, narrow metal wire, with respect to the cell on the cell so as to be soldered, the heating technique for dissolving the solder by pressing the interconnector by a bar-like or rod-like rigid pressing member is disclosed in patent documents 1 and 2; however, these prior arts mainly aim to position and fix the interconnector and do not describe anything about the warp of the cell resulted after the soldering of the thin photovoltaic cell is completed and warp prevention measures.
Accordingly, an object of the present invention is to provide a soldering method that does not warp a photovoltaic cell by heating for soldering an interconnector to the photovoltaic cell even if the cell is thin.
[Patent Document 1] Japanese Unexamined Patent Publication No. 11-87756
[Patent Document 2] Japanese Unexamined Patent Publication No. 2003-168811
The soldering method of the present invention is made for the purpose of resolving the above-described problems and is characterized in the steps of positioning the interconnector at a predetermined position of the photovoltaic cell at the time of soldering the interconnector to the photovoltaic cell; holding the cell in a flat state while the cell is under the heating atmosphere in which the solder is dissolved; and simultaneously, tightly holding the interconnector and the photovoltaic cell.
Also, the present invention teaches the soldering method for the interconnector to the photovoltaic cell, which is characterized in that the interconnector is positioned on the photovoltaic cell and held flat; and under the heat atmosphere, in which the solder is dissolved while the interconnector is being held in the cell, the interconnector and the photovoltaic cell are heated overall so as to solder while tightly holding the interconnector against the photovoltaic cell.
Also, in the above-mentioned soldering method, it is possible to employ a configuration whereby the interconnector is soldered at a predetermined position on the photovoltaic cell by entirely heating the photovoltaic cell under the heating atmosphere so as to dissolve the solder and thereafter slowly cooling the photovoltaic cell.
In the method of the present invention, since the photovoltaic cell to be soldered is held flat, it is possible to effectively inhibit the warp, which may be resulted in the photovoltaic cell after soldering the interconnector, in advance. The retention of the interconnector allows the cell to be held flat by pressing and supporting the interconnector to the photovoltaic cell side at a plurality of points on the interconnector, which does not cause unevenness in welding in the soldering because the cell and the interconnector can be held in a tight state.
As the pressing means for the interconnector for this purpose, it is preferable to employ an elastic stick-shaped member.
Further, on the photovoltaic cell side, in order to prevent the warping, it is preferable to constrain and hold the cell flatly in a direction at least extending along the interconnector to be soldered on a carrier holder or both side-edges extending along the interconnector from both surfaces.
If the photovoltaic cell, which is held flat in the manner mentioned above in the soldering step, is supported in a lower surface of the cell by a surface-shaped member or a crosspiece-shaped member on the carrier holder of the cell, it is possible to more effectively achieve the warp prevention according to the method of the present invention.
According to the present invention, when soldering the interconnector to the photovoltaic cell, the soldering the interconnector is carried out by setting the cell and the whole of the interconnector arranged in the cell under the heating atmosphere capable of dissolving the solder and entirely heating under the heating atmosphere, thereby dissolving the solder.
In the above-mentioned soldering step, since the solder is dissolved in the mechanical flat holding state of the photovoltaic cell in which the whole of the interconnector is arranged, it is possible to effectively prevent the deformation (the warp) of the photovoltaic cell at the time of soldering.
Also, according to the soldering method of the present invention, the interconnector can be pressed at multiple points and intervals of the pressing support can appropriately be adjusted such that the interconnector does not move up from the cell at the time of soldering.
Accordingly, uneven solder welding and defects can be eliminated.
Further, according to the present invention, since the photovoltaic cell is slowly cooled after entirely heating the photovoltaic cell so as to dissolve the solder, the interconnector moves within the dissolving solder when the solder is solidified, even if the heat contraction difference exists between the photovoltaic cell and the interconnector.
Accordingly, the deformation (warp) due to the difference of coefficient of thermal expansion between the photovoltaic cell and the interconnector and the thermal strain due to temperature distribution can be effectively prevented.
The above and other objects of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
Next, embodiments for the soldering method of the present invention are explained with examples of the embodiments and comparative examples with reference to the accompanying drawings and tables.
First,
The heating space 2 is formed in the following configurations. The heating space 2 is configured to be vertically dividable and is capable of opening and closing. The above-described carrier conveyor 1 is positioned at an intermediate position in a vertical direction of an upper chamber 2a and a lower chamber 2b. The carrier holders 3-10, which are holding cells Ce and interconnectors Tr, (not shown in FIG. 1,) together, run on the carrier conveyor 1. The carrier holders 3-10 are explained in detail later.
In the illustrated embodiment, four pairs of upper and lower heaters 2c, 2d, 2e and 2f are arranged in such a manner as to sandwich the conveyor 1 within a space formed by the chamber bodies 2a and 2b.
In the embodiment of the heating space 2 in
In
Directivity can be given to solidification of the dissolved solder of the interconnector which is arranged at a predetermined position of the photovoltaic cell by adjusting temperature and the gas volume of air blown from the cooling fan 2h and conveyor speed of the carrier conveyor 1. More preferably, the slow cooling desirably progresses from one end of the photovoltaic cell Ce toward the other side in such a manner as to prevent the warp and deformation of the photovoltaic cell Ce caused by the contraction force of interconnectors Tr because the movement of the interconnectors Tr in the dissolved solder progresses from one direction. Accordingly, “slow cool” in the present invention means phenomenon, contracting the interconnectors Tr within the solder and reducing a pulling force applied to the cell on the basis of the contraction of the interconnectors Tr while soldering is in progress as gradually cooling down.
In this case, the slow cooling means is not limited to the cooling fan but may be configured such as to set the temperatures of the heaters 2c to 2f within the heating space 2 to gradually lower the temperature toward the outlet side.
In the present invention, in order to find the soldering method that does not warp the cell Ce, in the soldering step of
Also, the carrier holders 3-10 in each embodiment and the comparative example is constituted by the upper holders and the lower holders as shown in the summary configuration in
Embodiment 1 of the carrier holder 3 of the photovoltaic cell Ce with the interconnectors Tr arranged at the predetermined position is as shown in
The cell support bodies 3a and 3b exemplified in
In
Embodiment 3 of the carrier holder of the cell Ce to which the interconnectors Tr are soldered is as shown in
In the present invention, the soldering steps of the interconnectors Tr to the cell Ce is executed by causing the carrier holders 3 to 5 exemplified in
Also, the cell Ce and the interconnectors Tr are set to the tightly held state by the upper and lower support bodies 3a and 3b (refer to
The above-described holding method of the cell Ce and the interconnectors Tr at the time of soldering the cell Ce is arranged to achieve a good result with no warping of the cell Ce after being soldered as shown in Table 1 and no unevenness in welding of the soldering in the embodiments 1 to 3.
Next, the comparative examples are used to explain the effectiveness of the embodiments of the present invention is such that the method of the present invention can remove the warp and unevenness in welding in the soldering between the photovoltaic cell Ce and the interconnectors Tr.
Also, in the comparative examples, the interconnectors Tr are arranged at the upper side and the lower side of the cell Ce.
The carrier holder 6 of the comparative example 1 is configured as shown in
A support of the lower surface of the cell Ce is constructed by attaching a plurality of round rod shaped support crosspieces 61a, which are orthogonal to the cell carrier direction, in almost equal pitches, to an approximately rectangular frame 62a ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
On the other hand, the press of the cell Ce and the interconnectors Tr from above is constructed by attaching a plurality of round rod shaped press bars 61b, which are orthogonal to the cell carrier direction, in almost equal pitches, to the approximately rectangular frame 62b ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
According to this configuration, a gap g is generated at the thickness of the interconnectors Tr between the cell Ce and the support crosspiece 61a on the one hand, and between the cell Ce and the press bar 61b on the other hand. The upper carrier holder and the lower carrier holder with the above-described configurations are fixed by the heat resistant tape Ft or the like. The cell Ce and the interconnectors Tr all together (in
In the condition of the soldering between the cell Ce and the interconnectors Tr after being soldered, since the right and left side-edges of the cell Ce are not flatly held, the warp is resulted as described in Table 1.
The carrier holder 7 of the comparative example 2 is configured as shown in
That is, a support of the lower surface of the cell Ce is constructed by attaching a plurality of round rod shaped support crosspieces 71a, which are orthogonal to the cell carrier direction, in almost equal pitches, to an approximately rectangular frame 72a ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
On the other hand, the pressing the cell Ce and the interconnectors from above is constructed by arranging a plurality of round rod shaped press bars 71b which are orthogonal to the cell carrier direction. Each round rod shaped press bars 71b is configured such that a spring 76b is connected to both ends thereof and are attached in almost equal pitches to an approximately rectangular frame 72b ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
The upper carrier holder and the lower carrier holder with the above-described configurations are fixed by the heat resistant tape Ft. The cell Ce and the interconnectors Tr all together (in
In the condition of the soldering between the cell Ce and the interconnectors Tr, unevenness in welding of the soldering after being soldered appeared as described in Table 1 depending upon the existence of the press bar 71b and its expanded spring.
The carrier holder 8 of the comparative example 3 is configured as shown in
That is, a support of the lower surface of the cell Ce is constructed by attaching a plurality of the springs 81a, which are orthogonal to the cell carrier direction, in almost equal pitches, to an approximately rectangular frame 82a ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
On the other hand, the pressing the cell Ce and the interconnectors Tr from above is constructed by attaching a plurality of springs 81b, which are orthogonal to the cell carrier direction, in almost equal pitches, to the approximately rectangular frame 82b ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
The upper carrier holder and the lower carrier holder with the above-described configurations are fixed by the heat resistant tape Ft or the like. The cell Ce and the interconnectors Tr all together (in
In the condition of the soldering between the cell Ce and the interconnectors Tr, many portions with attachment defect after being soldered appeared as described in Table 1.
This is believed to occur because the tight holding degree between the cell Ce and the interconnectors Tr fall short because of an insufficient holding force generated by the springs 81a and 81b in the horizontal position.
The carrier holder 9 of the comparative example 4 is configured as shown in
That is, the support of the lower surface of the cell Ce is constructed by arranging a metal net-shaped or grid-shaped support body 91a having a heat resistance in an approximately rectangular frame 92a ample enough for the cell Ce to fit as seen from (with reference to) the plan view of
On the other hand, the pressing the cell Ce and the interconnectors Tr from above is constructed by arranging a metal net-shaped or grid-shaped press body 91b having a heat resistance in the same manner as the lower surface of the cell Ce in an approximately rectangular frame 92b ample enough for the cell Ce to fit therein as seen from (with reference to) the plan view of
In the condition of the soldering between the cell Ce and the interconnectors Tr, uneven welding appeared in addition to the large warp after being soldered, as described in Table 1. This is because the right and left side-edges of the cell Ce are not flatly held, and the pressing force for tightly holding the interconnectors Tr against the cell surface becomes insufficient.
Comparative example 5 is not illustrated in the figures. Although it is not shown in the figures, the carrier holder described hereinbelow is used in this example. The carrier holder 9, which is the same as the comparative example 4, is used to press each side of frames 92a and 92b of the support body 91a and the pressing body 91b by the heat resistant tape Ft to mount a weight (not shown in the figures) to the center portion of the net-shaped or grid-shaped body 91b, thereby holding the cell Ce and the interconnectors Tr together. Thereafter, the soldering is carried out by mounting the carrier holder 9 on the conveyor 1 so as to travel within the heating space 2.
In the condition of the soldering between the cell Ce and the interconnectors Tr, uneven welding appeared after being soldered, as described in the Table 1. This is because the tightly holding degree between the interconnectors Tr and the cell Ce becomes insufficient.
The carrier holder 10 of the comparative example 6 is configured as shown in
That is, the support of the lower surface of the cell Ce is constructed, in the same manner as the comparative example 4, by arranging a metal net-shaped or grid-shaped support body 101a having a heat resistance in an approximately rectangular frame 102a ample enough for the cell Ce to fit as seen from (with reference to) the plan view of
On the other hand, the pressing cell Ce and the interconnectors from above is constructed by arranging a plurality of an almost fork claw shape or stick shape elastic press bar 101b to the frame 102b in the same manner as the embodiment 2.
In addition, the upper surface of the cell Ce is constructed by pressing both side-edges thereof by a press plate 104b. In addition, an attaching screw 103 is to attach and detach the press bar 101b.
The upper carrier holder and the lower carrier holder with the above-described configurations are fixed by the heat resistant tape Ft or the like. The cell Ce and the interconnectors Tr all together (in
In the condition of the soldering between the cell Ce and the interconnectors Tr, the warp after being soldered appeared as described in the Table 1. This is because the lower surface support of the cell Ce cannot smoothly support an expansion and contraction strain in the soldering processing of the cell Ce, and a residual heat strain results in the large warp.
The above-description is made for the case that the interconnectors Tr are tightly held against the cell Ce by utilizing the elasticity of the press bar provided in the carrier holders 3 to 5 shown in
In addition to the case that the interconnectors Tr is actively pressed to tightly hold the interconnectors Tr against the cell Ce, the present invention may have the configuration whereby the holding condition is such that the press force is approximately zero by selecting the holding intervals of the interconnectors Tr by the press bar in order to hold the interconnectors Tr as abutting against the cell Ce.
The soldering method of the photovoltaic cell and the interconnector of the present invention is configured as follows.
1) The soldering method comprises the steps of: positioning the interconnector at the predetermined position of the photovoltaic cell at the time of soldering the interconnector to the photovoltaic cell; setting the cell under the heating atmosphere in which the solder is dissolved in that state so as to hold the cell flat while heating entirely; and simultaneously holding the interconnector and the photovoltaic cell tightly.
2) The interconnector positioned at the predetermined position of the photovoltaic cell is soldered by dissolving the solder while entirely heating the photovoltaic cell under the heating atmosphere and thereafter slowly cooling the photovoltaic cell.
Accordingly, even if the deformation caused by the different expansion and contraction is generated in the cell and the interconnector having the different coefficients of thermal expansion due to the heating and the cooling of the soldering step, the entire cell and interconnector are constrained flat and are tightly held, so that it is possible to achieve the specific effect whereby there is no resultant warp in the cell during soldering and at the room temperature after the end of the soldering.
Further, since the photovoltaic cell is cooled slowly after entirely heating the photovoltaic cell under the heating atmosphere so as to dissolve the solder, the interconnector moves within the dissolving solder at a time as the solder solidifis, and therefore it is possible to effectively prevent the deformation (the warp) caused by the heat strain due to the difference of coefficient of thermal expansion between the photovoltaic cell and the interconnector and the temperature distribution thereof.
Accordingly, the method of the present invention is extremely useful as the soldering method of the interconnector at the time of processing the photovoltaic module without resulting in the warp in the thin photovoltaic cell which is increased in recent years.
1. carrier conveyor in soldering step, 2. heating space for soldering, 3. carrier holder of photovoltaic cell in which interconnectors are arranged in the embodiment 1, 4. carrier holder of photovoltaic cell in which interconnectors are arranged in the embodiment 2, 5. carrier holder of photovoltaic cell in which interconnectors are arranged in the embodiment 3, 6. carrier holder of photovoltaic cell in which interconnectors are arranged in the comparative example 1, 7. carrier holder of photovoltaic cell in which interconnectors are arranged in the comparative example 2, 8. carrier holder of photovoltaic cell in which interconnectors are arranged in the comparative example 3, 9. carrier holder of photovoltaic cell in which interconnectors are arranged in the comparative example 4, 10. carrier holder of photovoltaic cell in which interconnectors are arranged in the comparative example 6, 2c-2f. heater, 3a. support body (lower surface side), 3b. support body (upper surface side), 41a. support crosspiece, 41b. elastic press bar, 42a, 42b. frame, 43. attaching screw, 44b. press plate, 55a. support body, 55b. press plate, 61a. support crosspiece, 61b. press bar, 62a, 62b. frame, 71a. support crosspiece, 71b. press bar, 72a, 72b. frame, 76b. spring, 81a, 81b. spring, 82a, 82b. frame, 91a. net-shaped or grid-shaped support body, 91b. net-shaped or grid-shaped press body, 92a, 92b. frame, 101a. net-shaped or grid-shaped support body, 101b. elastic press bar, 102a, 102b. frame, 103. attaching screw, 104b. press plate, Ce. Photovoltaic cell, Tr. Interconnector
While the embodiments of the present invention disclosed herein are presently considered to be preferred embodiments, various changes and modifications can be made without departing from the spirit and scope of the present invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-001592 | Jan 2006 | JP | national |
| 2006-135822 | May 2006 | JP | national |
This is a National Phase Application in the United States of International Patent Application No. PCT/JP2006/325266 filed on Dec. 19, 2006, which claims priorities on Japanese Patent Application No. 2006-001592, filed on Jan. 6, 2006 and Japanese Patent Application No. 2006-135822, filed on May 15, 2006. The entire disclosures of the above patent applications are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/325266 | 12/19/2006 | WO | 00 | 7/7/2008 |
