1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and processes that are useful for reliably forming electrical connections in a solar cell device in a solar cell production line.
2. Description of the Related Art
Photovoltaic (PV) devices or solar cells are devices which convert sunlight into direct current (DC) electrical power. Typical thin film PV devices, or thin film solar cells, have one or more p-i-n junctions. Each p-i-n junction comprises a p-type layer, an intrinsic type layer, and an n-type layer. When the p-i-n junction of the solar cell is exposed to sunlight (consisting of energy from photons), the sunlight is converted to electricity through the PV effect. Solar cells may be tiled into larger solar arrays. The solar arrays are created by connecting a number of solar cells and joining them into panels with specific frames and connectors.
Typically, a thin film solar cell includes active regions, or photoelectric conversion units, and a transparent conductive oxide (TCO) film disposed as a front electrode and/or as a back electrode. The photoelectric conversion unit includes a p-type silicon layer, an n-type silicon layer, and an intrinsic type (i-type) silicon layer sandwiched between the p-type and n-type silicon layers. Several types of silicon films including microcrystalline silicon film (μc-Si), amorphous silicon film (a-Si), polycrystalline silicon film (poly-Si), and the like may be utilized to form the p-type, n-type, and/or i-type layers of the photoelectric conversion unit. The backside electrode may contain one or more conductive layers.
With the current trend toward alternative energy sources, there is a need for a low cost way of producing electricity using a low cost solar cell device. Conventional solar cell manufacturing processes are highly labor intensive and have numerous interruptions that can affect production line throughput, solar cell cost, and device yield. Conventional solar cell fabrication processes include a number of manual operations that can cause the formed solar cell device properties to vary from one device to another. In typical solar cell electrical connection processes, formed electrical leads are manually positioned within a housing that is manually bonded to the solar cell. These manual processes are labor intensive, time consuming, and costly. Further, current solar cell electrical connection processes fail to ensure that robust and reliable bonds are formed absent physical destructive testing. Therefore, a need exists for an automated electrical connection module in a solar cell fabrication system that provides for non-destructive bond detection during the electrical connection process.
In one embodiment of the present invention, a solder bonding inspection method comprises positioning a conductive tab that is at least partially bonded to a conductive lead via solder material proximate a vision system having at least one camera. A portion of the solder material extends at least partly about the periphery of the conductive tab. The method further comprises capturing one or more images of the conductive tab and the conductive lead, analyzing the one or more images to determine the amount of the solder material extending about the periphery of the conductive tab, and determining whether an acceptable bond is formed between the conductive tab and the conductive lead by comparing the determined amount of the solder material extending about the periphery of the electrically conductive tab to a first threshold value.
In another embodiment, a solder bonding and inspection method comprises contacting a conductive tab with a heating element, wherein the conductive tab is adjacent a conductive lead, and wherein solder material is disposed between the conductive tab and the conductive lead. The method further comprises applying power to the heating element while monitoring the amount of power applied to the heating element, measuring the temperature of the heating element during the applying power to the heating element, capturing one or more images of the conductive tab and the conductive lead, analyzing the one or more images to determine an amount of the solder material extending about the periphery of the conductive tab, and determining whether an acceptable bond is formed between the conductive tab and the electrically conductive lead by comparing a profile of the monitored amount of power and the measured temperature with a profile of the expected amount of power and the expected temperature and comparing the determined amount of the solder material extending about the periphery of the conductive tab to a first threshold value.
In yet another embodiment of the present invention, a solar cell electrical connection module comprises a vision system configured to scan a solar cell device and locate a lead on the solar cell device and a robotic gripper having gripping elements configured to pick up, manipulate, and place a junction box onto the solar cell device such that a tab of the junction box is adjacent the lead using information received from the vision system, wherein solder material is disposed between the lead and the tab, and wherein the vision system is further configured to capture one or more images of the tab and the lead at an angle substantially perpendicular to the tab. The module further comprises a heating assembly comprising a heating element having a thermocouple attached thereto, wherein the heating element is configured to contact the tab. The module also comprises a controller configured to apply power to the heating element while monitoring the amount of power applied to the heating element, monitor temperature readings from the thermocouple while applying power, analyze the one or more images to determine an amount of the solder material extending about the periphery of the tab, and determine whether an acceptable bond is formed between the tab and the lead by comparing the monitored amount of power and temperature readings with expected power and temperature, and comparing the determined amount of solder material extending about the periphery of the tab to a first threshold value.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention generally relates to an automated solar cell electrical connection module that is positioned within an automated solar cell fabrication line and is configured to ensure a robust and reliable bond is formed during the electrical connection process. The automated solar cell fabrication line is generally an arrangement of automated processing modules and automation equipment used to form solar cell devices. The electrical connection module generally provides a module and process for automatically attaching a junction box to a composite solar cell structure during the fabrication of a completed solar cell device. The electrical connection module further provides a thermode assembly including heating elements for forming a soldered connection between the junction box and the composite solar cell structure.
In one embodiment, the thermode assembly further includes a temperature sensing device in thermal communication with the heating elements for detecting a temperature profile during the connection process. The heating elements and temperature sensing device are linked to a controller configured to monitor and compare the energy input into the heating elements with the temperature near the tip of the heating elements throughout the connection process. The controller is further configured to compare the actual energy versus temperature profile to an expected profile throughout the connection process and verify whether a quality bond is achieved.
In one embodiment, the electrical connection module provides a vision system configured to capture images of the soldered connection between the junction box and the composite solar cell structure. The vision system is linked to the controller configured to analyze and compare the captured images to those of properly formed bonds to verify whether a quality bond is achieved.
A system controller 290 may be used to control one or more components found in the solar cell production line 200. The system controller 290 facilitates the control and automation of the overall solar cell production line 200 and typically includes a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various system functions, substrate movement, chamber processes, and support hardware (e.g., sensors, robots, motors, lamps, etc.), and monitor the processes (e.g., substrate support temperature, power supply variables, chamber process time, I/O signals, etc.). The memory is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.
A program (or computer instructions) readable by the system controller 290 determines which tasks are performable on a substrate. Preferably, the program is software readable by the system controller 290 that includes code to perform tasks relating to monitoring, moving, supporting, and/or positioning of a substrate along with various process recipe tasks and various chamber process recipe steps performed in the solar cell production line 200. In one embodiment, the system controller 290 also contains a plurality of programmable logic controllers (PLC's) that are used to locally control one or more modules in the solar cell production and a material handling system controller (e.g., PLC or standard computer) that deals with the higher level strategic moving, scheduling, and running of the complete solar cell production line. In another embodiment, the system controller 290 includes a plurality of local controllers (i.e., CPU, memory, support circuits) contained within one or more of the processing modules within the production line 200 for local monitoring and control of the respective module and for communicating with a higher level controller within the system controller 290.
Examples of a solar cell 300 that can be formed and tested using the process sequences illustrated in
As shown in
In one configuration, the first p-i-n junction 320 may comprise a p-type amorphous silicon layer 322, an intrinsic type amorphous silicon layer 324 formed over the p-type amorphous silicon layer 322, and an n-type amorphous silicon layer 326 formed over the intrinsic type amorphous silicon layer 324. The back contact layer 350 may include, but is not limited to, aluminum (Al), silver (Ag), titanium (Ti), chromium (Cr), gold (Au), copper (Cu), platinum (Pt), alloys thereof, or combinations thereof.
The first p-i-n junction 320 may comprise a p-type amorphous silicon layer 322, an intrinsic type amorphous silicon layer 324 formed over the p-type amorphous silicon layer 322, and an n-type microcrystalline silicon layer 326 formed over the intrinsic type amorphous silicon layer 324. The second p-i-n junction 330 may comprise a p-type microcrystalline silicon layer 332, an intrinsic type microcrystalline silicon layer 334 formed over the p-type microcrystalline silicon layer 332, and an n-type amorphous silicon layer 336 formed over the intrinsic type microcrystalline silicon layer 334. The back contact layer 350 may include, but is not limited to, aluminum (Al), silver (Ag), titanium (Ti), chromium (Cr), gold (Au), copper (Cu), platinum (Pt), alloys thereof, or combinations thereof.
As shown in
As shown in
To avoid confusion relating to the actions specifically performed on the substrates 302 in the discussion below, a substrate 302 having one or more of the deposited layers (e.g., reference numerals 310-350) and/or one or more internal electrical connections (e.g., side buss 355, cross-buss 356) disposed thereon is generally referred to as a device substrate 303. Similarly, a device substrate 303 that has been bonded to a back glass substrate 361 using a bonding material 360 is referred to as a composite solar cell structure 304.
Referring to
Referring to
Next, the device substrate 303 is transported via an automation device 281 to a scribe module 208 in which step 108, or a front contact isolation step, is performed on the device substrate 303 to electrically isolate different regions of the device substrate 303 surface from each other. In step 108, material is removed from the device substrate 303 surface by use of a material removal step, such as a laser ablation process. In one embodiment, a Nd:vanadate (Nd:YVO4) laser source is used ablate material from the device substrate 303 surface to form lines that electrically isolate one region of the device substrate 303 from the next. In one embodiment, the laser scribe process performed during step 108 uses a 1064 nm wavelength pulsed laser to pattern the material disposed on the substrate 302 to isolate each of the individual cells (e.g., individual cells 382A and 382B) that make up the solar cell 300. In one embodiment, a 5.7 m2 substrate laser scribe module available from Applied Materials, Inc. of Santa Clara, Calif. is used.
Next, the device substrate 303 is transported via an automation device 281 to a processing module 212 in which step 112, which comprises one or more photoabsorber deposition steps, is performed on the device substrate 303. In one embodiment, the device substrate 303 is cleaned in a substrate cleaning module 210 prior to being transported into the processing module 212. In step 112, the one or more photoabsorber deposition steps may include one or more preparation, etching, and/or material deposition steps that are used to form the various regions of the solar cell device. Step 112 generally comprises a series of sub-processing steps that are used to form one or more p-i-n junctions. In one embodiment, the one or more p-i-n junctions comprise amorphous silicon and/or microcrystalline silicon materials. In general, the one or more processing steps are performed in one or more cluster tools (e.g., cluster tools 212A-212D) found in the processing module 212 to form one or more layers in the solar cell device formed on the device substrate 303. In one embodiment, in cases where the solar cell device is formed to include multiple junctions, such as the tandem junction solar cell 300 illustrated in
Next, the device substrate 303 is transported via an automation device 281 to a scribe module 214 in which step 114, or the interconnect formation step, is performed on the device substrate 303 to electrically isolate various regions of the device substrate 303 surface from each other. In one embodiment, In one embodiment, a 5.7 m2 substrate laser scribe module available from Applied Materials, Inc. is used ablate material from the substrate surface to form lines that electrically isolate one solar cell from the next. In one embodiment, the laser scribe process performed during step 114 uses a 532 nm wavelength pulsed laser to pattern the material disposed on the device substrate 303 to isolate the individual cells that make up the solar cell 300. As shown in
Next, the device substrate 303 is transported via an automation device 281 to a processing module 218 in which one or more substrate back contact formation steps, or step 118, are performed on the device substrate 303. In step 118, the one or more substrate back contact formation steps may include one or more preparation, etching, and/or material deposition steps that are used to form a back contact layer, such as the back contact layer 350, of the solar cell device. In one embodiment, step 118 is performed using an ATON™ PVD 5.7 tool available from Applied Materials in Santa Clara, Calif. In another embodiment, one or more CVD steps are used to form the back contact layer 350 on the surface of the device substrate 303.
Next, the device substrate 303 is transported via an automation device 281 to a scribe module 220 in which step 120, or a back contact isolation step, is performed on the device substrate 303 to electrically isolate the plurality of solar cells located on the substrate surface from each other. In step 120, material is removed from the substrate surface by use of a material removal step, such as a laser ablation process. In one embodiment, a 5.7 m2 substrate laser scribe module, available from Applied Materials, Inc., is used ablate material from the device substrate 303 surface to form lines that electrically isolate one solar cell from the next. In one embodiment, the laser scribe process performed during step 120 uses a 532 nm wavelength pulsed laser to pattern the material disposed on the device substrate 303 to isolate the individual cells that make up the solar cell 300. As shown in
Next, the device substrate 303 is transported via an automation device 281 to a quality assurance module 222 in which step 122, or quality assurance and/or shunt removal steps, are performed on the device substrate 303 to assure that the devices formed on the substrate surface meet a desired quality standard and in some cases correct defects in the formed device. In step 122, a probing device is used to measure the quality and material properties of the formed solar cell device by use of one or more substrate contacting probes.
Next, the device substrate 303 is optionally transported via an automation device 281 to the substrate sectioning module 224 in which a substrate sectioning step 124 is used to cut the device substrate 303 into a plurality of smaller device substrates 303 to form a plurality of smaller solar cell devices. In one embodiment, steps 102-122 can be configured to use equipment that is adapted to perform process steps on large device substrates 303, such as 2200 mm×2600 mm×3 mm glass device substrates 303, and steps 124 onward can be adapted to fabricate various smaller sized solar cell devices with no additional equipment required. In another embodiment, step 124 is positioned in the process sequence 100 prior to step 122 so that the initially large device substrate 303 can be sectioned to form multiple individual solar cells that are then tested and characterized one at a time or as a group (i.e., two or more at a time). In this case, steps 102-121 are configured to use equipment that is adapted to perform process steps on large device substrates 303, such as 2200 mm×2600 mm×3 mm glass substrates, and steps 124 and 122 onward are adapted to fabricate various smaller sized modules with no additional equipment required.
Next, the substrate 303 is transported via an automation device 281 to a bonding wire attach module 231 in which a bonding wire attach step 131, is performed on the substrate 303. Step 131 is used to attach the various wires/leads required to connect the various external electrical components to the formed solar cell device. In one embodiment, the bonding wire attach module 231 is used to form the side-buss 355 (
The cross-buss 356, which is electrically connected to the side-buss 355 at the junctions, can be electrically isolated from the back contact layer(s) of the solar cell by use of an insulating material 357, such as an insulating tape. The ends of each of the cross-busses 356 generally have one or more leads 362 that are used to connect the side-buss 355 and the cross-buss 356 to the electrical connections found in a junction box 370, which is used to connect the formed solar cell to the other external electrical components.
In the next step, step 132, a bonding material 360 (
Referring to
In one part of step 132, the bonding material 360 is transported and positioned over the back contact layer 350, the side-buss 355 (
Next, the device substrate 303, the back glass substrate 361, and the bonding material 360 are transported to a bonding module 234 in which step 134, or lamination steps are performed to bond the backside glass substrate 361 to the device substrate formed in steps 102-130 discussed above. In step 134, a bonding material 360, such as Polyvinyl Butyral (PVB) or Ethylene Vinyl Acetate (EVA), is sandwiched between the backside glass substrate 361 and the device substrate 303. Heat and pressure are applied to the structure to form a bonded and sealed device using various heating elements and other devices found in the bonding module 234. The device substrate 303, the back glass substrate 361, and the bonding material 360 thus form a composite solar cell structure 304 (
Next the composite solar cell structure 304 is transported via an automation device 281 to an autoclave module 236 in which step 136, or autoclave steps are performed on the composite solar cell structure 304 to remove trapped gasses in the bonded structure and assure that a good bond is formed during step 134. In step 134, a bonded solar cell structure 304 is inserted in the processing region of the autoclave module where heat and high pressure gases are delivered to reduce the amount of trapped gas and improve the properties of the bond between the device substrate 303, back glass substrate, and bonding material 360.
Next, the composite solar cell structure 304 is transported via an automation device 281 to a junction box attachment module 238 in which a junction box attachment step 138 is performed on the composite solar cell structure 304. The junction box attachment module 238, used during step 138, is used to install a junction box 370 (
Next, the solar cell structure 304 is transported via an automation device 281 to a device testing module 240 in which device screening and analysis steps 140 are performed on the solar cell structure 304 to assure that the devices formed on the solar cell structure 304 surface meet desired quality standards. In one embodiment, the device testing module 240 is a solar simulator module that is used to qualify and test the output of the one or more formed solar cells.
Next the solar cell structure 304 is transported via an automation device 281 to a support structure module 241 in which support structure mounting steps 141 are performed on the solar cell structure 304 to provide a complete solar cell device that has one or more mounting elements attached to the solar cell structure 304 formed using steps 102-140 to a complete solar cell device that can easily be mounted and rapidly installed at a customer's site.
Next the solar cell structure 304 is transported to an unload module 242 in which step 142, or device unload steps are performed on the substrate to remove the formed solar cells from the solar cell production line 200.
The junction box attachment module 238 and processing sequence 500, performed during step 138, are used to install a junction box 370 (
In one embodiment, the main structure 400 includes a support truss, or support structure 408, that is adapted to support and retain the various components used to perform the processing sequence 500. In one embodiment, the conveyor system 401 includes a plurality of conventional conveyor belts 401A that are mounted to the support structure 408 to allow the composite solar cell structure 304 to be positioned and transferred through the junction box attachment module 238. As shown in
In one embodiment, the gantry system 405, which is also supported by the support structure 408, includes structural components 405B and automation hardware that is used to move and position the head assembly 406 over the composite solar cell structure 304 that is positioned on the conveyor system 401. The gantry system 405 may include an actuator 405A, such as a servomotor controlled belt and pulley system, that is adapted to controllably position the head assembly 406 over the composite solar cell structure 304. In one embodiment, the positioning of the head assembly 406 is controlled via the system controller 290.
In one embodiment, the junction box conveyor assembly 404 is configured to receive one or more junction box components, such as junction boxes 370 and junction box lids 370A, from an operator, or an automated supply device 404A, and deliver them to a receiving region 411 of the junction box attachment module 238 in an automated fashion. Once the one or more junction box components are positioned in the receiving region 411, the head assembly 406 may receive, remove, and place these components onto the composite solar cell structure 304 positioned on the conveyor system 401 via commands sent from the system controller 290. In one embodiment, the junction box conveyor assembly 404 is adapted to receive a tray 410 of junction box components from the supply device 404A and move the tray 410 (along path “B”) to the receiving region 411 using a conveyor 404B.
In one embodiment, the gantry system 405 includes a robotic arm assembly 407. The robotic arm assembly 407 may be configured to pickup a junction box 370 from the tray 410 positioned in the receiving region 411 and move the junction box 370 into a position for dispensing adhesive and flux, as discussed below.
In one embodiment, the adhesive dispense assembly 402 includes components adapted to deliver an adhesive, such as a hot melt room temperature vulcanizing (RTV) adhesive, to a section of the junction box attachment module 238, such as a nozzle in the dispense head assembly 403A, where the adhesive can be disposed upon a sealant receiving surface of the junction box 370. In one embodiment, the adhesive dispense assembly 402 is automated and is adapted to heat and dispense the adhesive material using resistive heating elements and a pressurized fluid delivery system. The pressurized fluid delivery system may use pressurized gas or other mechanical means to deliver the heated adhesive to the dispense head assembly 403A the junction box 370.
In one embodiment, the flux dispense assembly 412 includes components adapted to deliver a flux material to a section of the junction box attachment module 238, such as a nozzle in the dispense head assembly 403A, where the flux material is dispensed onto the electrical connection tabs 354 (
In one embodiment, the potting material dispense assembly 403 includes components adapted to deliver a potting material, such as a two part RTV material, to an internal region 365 (
In one embodiment, the vision system 421 includes a camera 421A and other electronic components that are able to locate, communicate, and store the position of features found within the formed composite solar cell structure 304. For example, the vision system 421 may be used to find the position of the exposed leads 362 of the cross-buss 356 and the opening 363 found in the back glass substrate 361 of the composite solar cell structure 304 (
Once the desirable features on the composite solar cell substrate 304 are located by the vision system 421, a junction box 370 that has been received by the robotic gripper 422 may be positioned on the composite solar cell structure 304, and electrical connections between the junction box 370 and the composite solar cell structure 304 may be reliably made as discussed below. In one embodiment, the robotic gripper 422 includes gripping elements 422A, 422B adapted to mate with two or more datum surfaces 358 (
In one embodiment, the thermode assembly 423 includes two or more thermal devices that are used to deliver heat to form a good electrical connection between the leads 362 of the cross-buss 356 (
After the soldered connection is formed, the vision system 421 may be used for optical inspection of the soldered connection between the leads 362 of the cross buss and the electrical connection tabs 354 located in the junction box 370.
In one embodiment, the system controller 290 is programmed to measure the amount of exposed solder reflow material 490 extending beyond the electrical connection tabs 354 and leads 362 by summing the number of pixels found in the collected image to calculate the total area of the exposed solder material 490. The system controller 290 is then programmed to compare the calculated total area of the exposed solder reflow material 490 with known acceptable values to indicate whether the solder connection is acceptable. For instance, if the calculation of the area of the solder reflow material 490 that is visible about the perimeter of the connection tabs 354 is equal to or exceeding a threshold value, the system controller 290 indicates that the soldered connection passes the criteria for an acceptable connection. However, if the calculation is below the threshold value, the system controller 290 indicates that the soldered connection does not pass the criteria for an acceptable connection.
Additionally, the system controller 290 may be programmed to determine the continuity of the exposed solder reflow material 490 about the perimeter of each connection tab 354 and compare the result with acceptable values defined by one or more algorithms to determine whether an acceptable bond has been formed. For example, the solder reflow material 490 exposed about the perimeter of connection tab 354A in
In one embodiment, the system controller 290 may also be programmed to measure and analyze the location and orientation of the connection tabs 354 with respect to the orientation of the leads 362. The system controller 290 may be programmed to compare the measured location and orientation information with acceptable values and indicate whether the soldered connection passes the criteria for an acceptable connection.
In one embodiment, the lid retrieving robot 426 is adapted to receive the junction box lid 370A from the receiving region 411 and position it over the junction box 370 after all of the electrical connections have been made and the potting material has been positioned within the internal region 365 of the junction box 370. The lid retrieving robot 426 may include one or more vacuum end-effectors 426A that are adapted to receive and hold the junction box lid 370A as the lid retrieving robot 426 is maneuvered over the junction box 370 via the head assembly 406, the gantry system 405, and the system controller 290.
Referring to
In one embodiment, the processing sequence 500 generally begins at step 502 in which one or more junction boxes 370 and/or one or more junction box lids 370A are moved to the receiving region 411 of the junction box attachment module 238 using the conveyor assembly 404, discussed above.
In step 504, the junction box 370 is prepared for installation on the composite solar cell structure 304 that has been processed up through steps 134 and/or 136 of the process sequence 100, discussed above. During step 504 an adhesive material, such as a hot melt RTV adhesive, is disposed on a sealant receiving surface of the junction box 370. In one embodiment, the robotic arm assembly 407 receives the junction box 370 from the tray 410 positioned in the receiving region 411 and moves the junction box 370 to the dispense head assembly 403A, which dispenses the adhesive via a nozzle on the sealant surface of the junction box 370. In one embodiment of step 504, a flux material is applied to each of the electrical connection tabs 354 via another nozzle in the dispense head assembly 403A as well.
In step 506, the vision system 421 in conjunction with the gantry system 405, head assembly 406, conveyor system 401, and system controller 290 scans the composite solar cell structure 304 to locate the leads 362 of the cross-buss 356 and the opening 363 formed in the back glass substrate 361. In one embodiment, a camera 421A within the vision system 421 and the system controller 290 are used to automatically locate and store the position of the leads 362 and the opening 363 so that the other robotic components in the junction box attachment module 238 can reliably perform the remaining attachment steps.
In step 508, the junction box 370 is disposed on the composite solar cell structure 304, which is positioned on the conveyor system 401 so that the adhesive material on the sealant receiving surface can form a seal around the opening 363 contained in the back glass substrate 361. In one embodiment, during step 508 the junction box 370 is picked-up by the robotic gripper 422 from the robotic arm assembly 407, and accurately oriented and positioned over the leads 362 of the cross-buss 356 and the opening 363 by use of the information received by the vision system 421 during step 506. In one embodiment, the gripping elements 422A, 422B of the robotic gripper 422 receive the datum surfaces 358 on the junction box 370 to provide for the correct alignment and orientation of the junction box 370 with respect to the leads 362 and the opening 363. In one embodiment, the robotic gripper 422 urges the junction box 370 and adhesive material against the surface of the back glass substrate 361 during installation. The urging force may be sufficient to obtain an even spread of adhesive material as well as obtain good contact between the leads 362 and the electrical connection tabs 354.
In step 510, the thermode assembly 423 is positioned (X, Y and Z directions) to deliver heat to the leads 362 of the cross-buss 356 and the electrical connection tabs 354 in the junction box 370 to form a robust electrical connection. In one embodiment, the heating elements 424, 425 of the thermode assembly 423 simultaneously contact and apply heat to the electrical connection tabs 354 sufficient to cause the solder material and flux located between the leads 362 and the electrical connection tabs 354 to reflow and form a reliable and robust electrical connection between the junction box 370 and the composite solar cell structure 304.
In a heating step 604, electrical power to the heating elements 424 and 425 is ramped up in order to heat the elements 424 and 425 up to a desired bonding temperature as measured by the temperature sensors 450 located on the heating elements 424 and 425. In one embodiment, the system controller 290 continuously monitors and tracks the temperature measured by the temperature sensors 450 as well as the amount of power applied to the elements 424 and 425 for the duration of the heating step 604. The system controller 290 then compares a profile of the input power versus temperature obtained during the heating step 604 to an expected profile of input power versus temperature for an established, acceptable heating step 604. The system controller 290 then determines whether the heating step 604 was within desired parameters as provided by the comparison. In one embodiment, an expected power input for heating each heating element from an initial temperature of between about 50° C. and about 300° C. to a bonding temperature of between about 350° C. and about 800° C. is between about 25 W and about 500 W over a time period of between about 0.05 s and about 1 s. For example, an expected power input for heating each heating element from an initial temperature of about 50° C. to a bonding temperature of between about 400° C. and about 500° C. is between about 300 W and about 400 W over a time period of about 0.5 s. If the actual power input during the heating step 604 is outside of the expected parameters, the system controller 290 may indicate that a problem exists that may prevent a good solder bond from being achieved between the electrical connection tabs 354 of the junction box 370 and the leads 362 of the cross-buss 356. For example, if less than full contact between the elements 424, 425, the electrical connection tabs 354, and the leads 362 exists, the elements 424, 425 may heat up very quickly with less power than expected indicating that a good bond may not be achievable between the electrical connection tabs 354 and the leads 362.
In a bonding step 606, electrical power to the heating elements 424 and 425 is provided at a substantially steady state to maintain the elements 424 and 425 at a desired bonding temperature during the bonding process as measured by the temperature sensors 450 located on the heating elements 424 and 425. During the bonding step 606, the solder material located between the electrical connection tabs 354 and the leads 362 is reflowed to form an electrical and mechanical connection therebetween. In one embodiment, the system controller 290 continuously monitors and tracks the temperature measured by the temperature sensors 450 as well as the amount of power applied to the elements 424 and 425 for the duration of the bonding step 606. The system controller 290 then compares a profile of the input power versus temperature obtained during the bonding step 606 to an expected profile of input power versus temperature for an established, acceptable bonding step 606. The system controller 290 then determines whether the bonding step was within desired parameters as provided by the comparison. In one embodiment, an expected power input for maintaining a bonding temperature of between about 300° C. and about 800° C. during the bonding step 606 may be between about 25 W and about 500 W for a duration of about 0.5 s and about 5 s. For example, an expected power input for maintaining a bonding temperature of between about 400° C. and about 500° C. during the bonding step 606 may be between about 300 W and about 400 W for a duration of about 2 s. If the actual power input during the bonding step 606 is outside of the expected parameters, the system controller 290 may indicate that a good solder bond was not achieved between the electrical connection tabs 354 of the junction box 370 and the leads 362 of the cross-buss 356. For example, if less than full contact exists between the elements 424, 425, the electrical connection tabs 354, and the leads 362, the elements 424, 425 may easily maintain an acceptable bonding temperature at significantly less power than expected, indicating that a good solder bond may not have been achieved between the electrical connection tabs 354 and the leads 362.
In a cool down step 608, electrical power to the heating elements 424, 425 is decreased or stopped in order to bring the temperature of the elements 424, 425 back down to the initial temperature as measured by the temperature sensors 450 coupled to the elements 424, 425. During the cool down step 608, the solder material between the leads 362 and the electrical connection tabs 354 is solidified and a robust mechanical and electrical connection therebetween is achieved. In one embodiment, the system controller 290 continuously monitors and tracks the temperature of the elements 424, 425 measured by the temperature sensors 450 as well as the amount of amount of power applied to the elements 424 and 425 during the cool down step 608. The system controller 290 then compares a profile of the input power versus temperature obtained during the cool down step 608 to an expected profile of input power versus temperature for an established, acceptable cool down step 608. The system controller 290 then determines whether the cool down step 608 was within desired parameters as provided by the comparison. In one embodiment, no power is input during reducing the temperature of the elements 424, 425 from a bonding temperature of between about 350° C. and about 800° C. back to the initial temperature of between about 50° C. and about 300° C. during the cool down step 608 for a duration of between about 0.1 s and about 2 s. If the actual power input during the heating step 604, bonding step 606, or the cool down step 608 is outside of the expected parameters or if the time duration is substantially outside of the expected parameters, the system controller 290 may indicate that a good solder bond was not achieved between the electrical connection tabs 354 of the junction box 370 and the leads 362 of the cross-buss 356.
After the cool down step 608 is substantially completed, the thermode assembly 423 is raised such that the heating elements 424 and 425 are clear from the electrical connection tabs 354 of the junction box 370 in a final positioning step 610. If the system controller indicates that a good solder bond was not formed between the electrical connection tabs 354 and the leads 362, the composite solar cell structure 304 may be removed from the junction box attachment module 238 for further analysis, rework, or scrap. Otherwise, the next step in the processing sequence 500 is performed.
Referring back to
In one embodiment, the system controller 290 first calculates the area of the solder reflow material 490 extending around the perimeter of the connection tabs 354 and in contact with the leads 362 by summing the number of pixels corresponding to the image of the visible solder reflow material 490. The system controller 290 then compares the calculated area of the solder reflow material 490 to a predefined threshold value. If the calculated value is less than the predefined threshold value, the system controller 290 issues a command that the soldered connection is not acceptable. The corresponding composite solar cell structure 304 may be removed from the junction box attachment module 238 for further analysis, rework, or scrap.
In one embodiment, the system controller 290 next analyzes the captured images to measure the continuity of the solder reflow material 490 extending around the perimeter of the connection tabs 354 and in contact with the leads 362. The system controller 290 compares the continuity analysis to predefined threshold criteria. If the continuity analysis does not meet the predefined threshold criteria, the system controller 290 issues a command that the soldered connection is not acceptable. The corresponding composite solar cell structure 304 may be removed from the junction box attachment module 238 for further analysis, rework, or scrap.
In one embodiment, the system controller 290 next analyzes the captured images to measure the location and orientation of the connection tabs 354 with respect to the orientation of the leads 362. The system controller 290 compares the measured location and orientation information with predefined acceptable values. If the measured location and orientation information does not meet the predefined acceptable values, the system controller 290 issues a command that the soldered connection is not acceptable. The corresponding composite solar cell structure 304 may be removed from the junction box attachment module 238 for further analysis, rework, or scrap. Otherwise, the next step in the processing sequence is performed.
In step 512, the internal region 365 of the junction box 370 is filled with a desired amount of a potting material by use of the dispense nozzle 427 disposed on the head assembly 406, the gantry system 405, conveyor system 401, and the system controller 290. The potting material, such as a polymeric material, is generally used to isolate active regions of the solar cell and the electrical connections formed during step 510 from environmental attack during the life of the formed solar cell device.
In step 514, the junction box lid is placed on the junction box 370 so that the internal region 365 of the junction box 370 can be further isolated from the external environment. In one embodiment, the lid retrieving robot 426 is configured to rotationally align the junction box lid 370A with respect to the composite solar cell structure 304 to properly angularly orient the junction box lid 370A with respect to the placement of the junction box 370. After completion of this processing sequence 500 the solar cell device is transferred to the device testing module 240 where step 140 can be performed.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application is related to co-pending U.S. patent application Ser. No. 12/581,728 [Attorney Docket No. APPM/14465], filed Oct. 19, 2009, which is herein incorporated by reference.