BACKGROUND STATEMENT FOR SEMI Draft Document 5204 NEW STANDARD: TEST METHOD FOR MECHANICAL VIBRATION OF C-SI PV CELLS IN SHIPPING ENVIRONMENT Note: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document. Note: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, patented technology is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided. Background Statement The photovoltaic industry, with crystalline silicon as a dominant segment, is expanding rapidly to meet growing renewable energy demands all over the world. Recent failure-rate analysis indicates that a large portion of the accelerated PV module qualification failures are related to the failure of the cell itself1. For c-si technology, one of the current technological problems is to identify and eliminate the sources of mechanical defects such as thermo-elastic stress and cracks. That is leading to the loss of wafer integrity and ultimate breakage of as-grown and processed Si wafers and cells. A significant challenge in using thinner crystalline silicon wafers for solar cell manufacture is the reduced yield due to increased wafer breakage. Shipping/Packaging damage is always one of the top problems of the PV failures in the field2. The cell breakage mostly depends on the stresses induced in the processing, handling and transportation, and also depends on the presence of defects such as cracks. This activity presents a test method for mechanical vibration of c-si PV cells in shipping environment. These stress factors due to environment are vibration and temperature. The transportation vehicles will include truck train aircraft and ship. This standard aims to provide a common test method to evaluate the defects on the PV cells due to stress during transportation. The cell makers and buyers, or any other party interested, can thus have a common testing standard to refer to when desired. The standard expects also to accelerate the development of cell protection design during transportation as well. The results of this ballot will be discussed at the next PV Cell Vibration Test Method Task Force and adjudicated at the Taiwan PV Standards Committee during their meetings scheduled in June 2012 at ITRI in Hsinchu, Taiwan. Check www.semi.org/standards for the latest schedule update. If you have any questions, please contact the PV Cell Vibration Test Method Task Force at: Teng-Chun Wu (wtc@itri.org.tw ) or contact SEMI Staff Catherine Chang at cchang@semi.org.
SEMI Draft Document 5204 NEW STANDARD: TEST METHOD FOR MECHANICAL VIBRATION OF C-SI PV CELLS IN SHIPPING ENVIRONMENT 1 Purpose 1.1 For c-si technology, one of the problems is to identify and eliminate the sources of mechanical defects such as thermo-elastic stress and cracks leading to the loss of wafer integrity and ultimate breakage of as-grown and processed Si cells. A significant challenge in using thinner crystalline silicon wafers for solar cell manufacture is the reduced yield due to increased cell breakage. Cell breakage mostly depends on the stresses induced in the processing, handling and transportation, and also depends on the presence of defects such as micro-cracks. Shipping damage is always one of the top problems of the PV failures in the field. 1.2 This standard presents a test method for mechanical vibration of c-si PV cells in transportation environment, which might be carried by truck, train, aircraft and shipboard, etc. This standard aims to provide a common test method to evaluate the micro-cracks or defects on the PV cells due to stress during transportation. The cell makers and buyers, or any other party interested, can thus have a common testing standard to refer to when desired. 1.3 The test result also can evaluate cell package performance during transportation. 2 Scopes 2.1 Basic Test System Requirements this standard states the basic vibration test system requirements. 2.2 This test method, covers the random vibration test of filled transportation unit, will be used to assess the performance of package design for mono/multi crystalline cells during shipping by different transportation vehicles. 2.3 Testing Procedure the general testing procedures are provided with a flowchart, including the vibration test, pre-test and post-test examination of the PV cells performance, according to current IEC Standards. These specifications for the vibration, including the frequency range and power spectral density, etc, corresponding to particular means of transportation are chosen by the user according to existing Standards (e.g. ASTM, MIL-STD). 2.4 Sampling Method usually multiple PV cells are stacked as a block; multiple blocks are stacked as a box and shipped boxes together in a test specimen. It is unnecessary, time-consuming and cost-intensive to carry out full performance tests on all blocks in the same test specimen. Therefore, select suitable test blocks of cells that undergo the pre-test and post-test examinations shall be helpful. 2.5 Sample Report and Data Formats results and relevant information are stated in the final test report to the customer, and in recommended report and data formats in Appendix. NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the Documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use. 3 Limitations 3.1 This document does not specify any kind of package for shipping unit. 3.2 This test and measurement method does not provide the specifications of the vibration. The allocation and number of measurement points, PSD, intensity and the test time should be considered. 4 Referenced Standards and Documents 4.1 SEMI Standards and Safety Guidelines SEMI PV23 Test Method for Mechanical Vibration of Crystalline Silicon Photovoltaic (PV) Modules in Shipping Environment Page 1 Doc. 5204 SEMI
4.2 ASTM Standards 1 ASTM D999 Standard Test Methods for Vibration Testing of Shipping Containers ASTM D4169 Standard Practice for Performance Testing of Shipping Containers and Systems ASTM D4332 Standard Practice for Conditioning Containers, Packages, or Packaging Components for Testing ASTM D4728 Standard Test Method for Random Vibration Testing for Shipping Containers 4.3 ISO Standards 2 ISO 2233 Packaging Complete, Filled Transport Packages and Unit Loads Conditioning for Testing 4.4 IEC Standards 3 IEC 60068-2-64 Environmental Testing Part 2-64: Tests Test Fh: Vibration, Broadband Random and Guidance IEC 60904-1 Photovoltaic devices Part 1: Measurement of photovoltaic current-voltage characteristics IEC 61215 Crystalline Silicon Terrestrial Photovoltaic (PV) Modules Design Qualification and Type Approval IEC 61730-2 Photovoltaic (PV) Module Safety Qualification Part 2: Requirements for Testing 4.5 Others 4 MIL-STD-810 F Environmental Engineering Considerations and Laboratory Tests NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions. 5 Terminology 5.1 Abbreviations and Acronyms 5.1.1 PSD Power Spectral Density 5.1.2 PV Photovoltaic 5.1.3 c-si Crystalline Silicon 5.1.4 Grms Root-Mean-Square Acceleration 5.1.5 Pmpp Maximum Power 5.1.6 EL Electro-Luminescence 5.1.7 STC Standard Test Conditions 5.2 Definitions 5.2.1 customer an individual or a company who uses this standard. 5.2.2 sample cell a real cell that undergoes the pre-test and post-test examinations for the evaluation of damages induced by vibration. 5.2.3 block (see figure 1) stacked sample cells for the purposes of vibration testing. 5.2.4 test block a block of sample cells to check vibration response with vibration test, and electric performance with both pre-test and post-test examinations. 1 American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA; Telephone: 610.832.9585, Fax: 610.832.9555, http://www.astm.org 2 International Organization for Standardization, ISO Central Secretariat, 1 rue de Varembé, Case postale 56, CH-1211 Geneva 20, Switzerland; Telephone: 41.22.749.01.11, Fax: 41.22.733.34.30, http://www.iso.ch 3 International Electrotechnical Commission, 3 rue de Varembé, Case Postale 131, CH-1211 Geneva 20, Switzerland; Telephone: 41.22.919.02.11, Fax: 41.22.919.03.00, http://www.iec.ch 4 United States Military Standards, Available through the Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, PA 19120-5099, USA; Telephone: 215.697.3321. Page 2 Doc. 5204 SEMI
5.2.5 test block locations the location of the test block inside the test specimen to be placed during the vibration test. 5.2.6 test specimen (see figure 1) a complete, filled transport package or unit load during the actual transportation or shipping. 5.2.7 vibration test specification data required to perform a vibration test using the apparatus in 6, including psd - grms and test time, etc. 5.2.8 defects imperfection of c-si like broken cell, crack or micro-cracks, cell with chips, holes in cells, etc. (a) Test specimen with 32 boxes in 4 layers (2x4x4) and 8 boxes (2x4) in one layer. (b) 9 measurement points include one center point (A), 4 corner (B) and 4 middle points(c) of both long and short edges, each measurement point is within an area of 10 cm x 10 cm. (c) 10 blocks (2x5) in one box 6 Apparatus 6.1 Vibration Table (Shaker) Figure 1 Example for Test Specimen, Block and Measurement Points 6.1.1 The vibration table must be sufficiently large to contain the whole test specimen. It shall be sufficiently strong and rigid in order to deliver the vibration specification, in terms of rated force, displacement and frequency range. In cases where the test specimen might fall off the table during testing, low fences should be used to restrict sideway movements. 6.2 Instrumentation 6.2.1 Apparatuses including the accelerometers, signal conditioners, analyzers, data display, storage devices and electronic controls are required to measure and control the vibration table. In addition, the instrumentation is required for measuring the response of the tested item. Accelerometers should be miniature type and light weight enough as to not influence the results of the test or measurement. 6.3 Analytical tools for pre-test and post-test examinations 6.3.1 Defect inspection device Page 3 Doc. 5204 SEMI
6.3.1.1 A non-destructive device can be used to differentiate cell s quality. The device shall record defects, such as EL device, microscope, photo-luminescence, etc. 6.3.2 Solar Simulator 6.3.2.1 A device to simulate sunlight and measure the electrical characteristics (e.g., maximum power, short-circuit current, open-circuit voltage, current and voltage at Pmpp, etc) of the cell at STC (AM1.5, 25 and 1,000 W/m 2 ) according to IEC60904-1 NOTE 1: The first resonance of vibration table should be 2 ( 1.414) times greater than the test frequency range. NOTE 2: The response uniformity of the vibration table should be under ± 3dB in the middle of the edges of table (see 9.3.2). 7 Preconditioning and Conditioning 7.1 The test specimen shall be conditioned according to the relevant sections in the same document of which the vibration test specification is used. For general or unspecified cases, ASTM D4332 or ISO 2233 are recommended for the conditioning. 8 Vibration Test Specifications 8.1 The vibration test specification, including PSD, Grms and the test time, shall be chosen usually referring to an existing transportation test standard in 4, or by the customer. For example, ground transportation ASTM D4169 truck assurance level II random profile, or MIL-STD, etc. The measurement points of vibration response may be allocated in top layer of test specimen, including one center point, 4 corner and 4 middle points of both long and short edges (see Figure 1 (b)). 8.2 Recommend vertical vibration is the first priority test. 9 Testing Procedures (See Figure 2 and Table 1) 9.1 Determination of test blocks 9.1.1 This test indicates blocks in which locations of the test specimen shall undergo the pre-test and post-test examinations in 9.2 and 9.4, and determines the distribution of the vibration response with accelerometers at test block locations. If the required vibration tests specification changes, the test in 9 shall be performed once again. The choice of test blocks should be near the measurement points of vibration response ii 8.1. 9.2 Pre-test examination 9.2.1 The pre-test examination consists of a selection of IEC tests and measurements on the sample cells according to the items listed in Table 1. If a cell fails a test, it should be replaced by a new sample cell until all tests in 9.2 are passed. Recommend all sample cells are in the same efficiency classification. All the sample cells visual inspection, maximum power, cell condition shall be recorded. 9.3 Vibration test 9.3.1 Place the test specimen on the vibration table. The vibration table size should be large than test specimen. 9.3.2 Table strength, measured at both 1/4 and 3/4 allocations for each edge center line during vibration, should be under ±3dB (see Figure 3). The control accelerometer is accuracy ±3% and deviation ±3dB, the other measure points are < ± 6dB. 9.3.3 Vibration response of test specimen for each measurement points by accelerometer should be not greater than 3 ~ 5 times of input level. 9.3.4 For general cases, ASTM D4169 is recommended. 9.4 Post-test examination 9.4.1 Remove the test blocks from the test specimen. Perform post-test examinations according to the test items in order listed in Table 1. All the cells inspection, maximum power and cell condition shall be recorded. Page 4 Doc. 5204 SEMI
9.1 Determination of test blocks 9.2 Pre-test examination 9.3 Vibration test 9.4 Post-test examination Figure 2 Testing Procedure Flowchart Table 1 Test Items in the Pre-test and Post-test Examinations Test Title Test Conditions 1 Visual inspection Carefully inspect each cell under an illumination of not less than 1,000 lux 2 Maximum power determination See IEC 60904-1 3 Record cell condition See 6.3.1 (a) Long edge (b) short edge Figure 3 Vibration Table with 4 Measurement Points by Accelerometers O is the Control Point, is Measurement Point Page 5 Doc. 5204 SEMI
10 Reporting Results 10.1 The test report shall include, at minimum, the following: 10.1.1 Description of the test specimen, including test block and sample cell. 10.1.2 Description of the apparatus and instrumentation used, including the last date of calibration. 10.1.3 Pre-test examination results, including the maximum power, notable visual defects, and defect images. 10.1.4 Post-test examination results, including the maximum power and defect images. 10.1.5 Summary of test events, test interruptions, and test failures. 10.1.6 Description of the vibration test specification used, including a plot of the actual input PSD of vibration table. 10.1.7 Description and photographs of the fixture of the test specimen on the vibration table. 10.1.8 Measuring point and test block locations determined in 9.1 10.1.9 Vibration responses Grms measured during the test in 9.3. 10.1.10 Modifications made to the test specimen for the purpose of vibration response measurement. 10.1.11 Any observation and vibration responses that may assist in correct interpretation of results or lead to improvements in the design of test specimen. 11 Related Documents 11.1 Piersol, A. G., and Paez, T. L., Harrys Shock and Vibration Handbook, 6th Edition, McGraw-Hill, New York, NY, 2010, pp. 10.1-15.22. 11.2 K. A. Emery, "Solar Simulators and I-V Measurement Methods", Solar Cells, 18, 3-4, pp. 251-260 (1986). Solar Energy Research Institute, 1617 Cole Boulevard, Golden, CO 80401 (U.S.A.) 11.3 Kuang-Han Ke, Shu-Tsung Hsu, Tsung-Chun Hsu, Kun-Da Lee, Yean-San Long, Definition, Classification and Inspection Methods of Cracks in Photovoltaic Cell -- Cracks Induced by Vibration Caused by Transportation, 2012 CPTIC 11.4 Shu-Tsung Hsu, Yean-San Long, Teng-Chun Wu, Kun-Da Lee, Yi-Hung Chou, Characterization of Crystalline Silicon PV Cells in Truck Transportation Environment, 2012 CPTIC Page 6 Doc. 5204 SEMI
APPENDIX 1 SAMPLE REPORT AND DATA FORMS NOTICE: The material in this Appendix is an official part of SEMI Doc. 5204 and was approved by full letter ballot procedures on [A&R approval date]. Table A1-1 General Information Company: Address: TEL: FAX: Date of issue[mm/dd/yyyy]: Testing Laboratory: Tested by: Approved by: Page 7 Doc. 5204 SEMI
Table A1-2 Vibration Test Equipment, Specification and Test Specimen 1. Vibration test equipment 1.1 Vibration tester: 1.2 Controller: 1.3 Shaker model: 1.4 Control accelerometer: 1.5 Measurement accelerometer: 2. Vibration test environment 2.1 Temperature [ C]: 2.2 Relative humidity [%RH]: 3. Vibration test specification 3.1 Standard used: 3.2 PSD diagram (input): 3.3 Frequency range: 3.4 Acceleration: 3.5 Displacement: 4. (Attach) diagrams or photos to describe exterior and interior packaging Page 8 Doc. 5204 SEMI
Table A1-3 Pre-test Examination Equipments and Environment 1. Equipment model: 2. Equipment specifications: 3. Environment data: Temperature [ C]: Relative humidity [%RH]: 4. Standards / Reference used: 5. Test date [MM/DD/YYYY]: 6. Cell temperature [ C]: 7. Irradiance [W/m 2 ]: 8. Description of abnormal sample cell list (visual inspection, Pmpp, defect image, etc) Page 9 Doc. 5204 SEMI
Table A1-4 Vibration Test 1. Photographs, description or diagram of test block allocations 2. Photographs, description or diagram of the measuring points and location 3. Test block, sample cell and accelerometer Test block serial no. Sample cells serial no Accelerometer no. 4. Vibration Response 5. Observation and improvement during vibration test Page 10 Doc. 5204 SEMI
Table A1-5 Post-test Examination Equipment and Environment 1. Equipment model: 2. Equipment specifications: 3. Environment data: Temperature [ C]: Relative humidity [%RH]: 4. Standards / Reference used: 5. Test date [MM/DD/YYYY]: 6. Cell temperature [ C]: 7. Irradiance [W/m 2 ]: 8. Breakage rate (%): 9. Failure rate (%): 10. Description of abnormal sample cell list ( visual inspection, Pmpp, defect image, etc) #1 Breakage rate (%): broken cells / total sample cells #2 Failure rate (%): (Broken and non-broken power loss sample cells) / total sample cells Page 11 Doc. 5204 SEMI
RELATED INFORMATION 1 DEFECT REPORT NOTICE: This Related Information is not an official part of SEMI doc. 5204 and was derived from the work of the global PV Technical Committee. This Related Information was approved for publication by full letter ballot procedures on [A&R approval date]. NOTE 1: Please specify condition of every cell with defect by following table. Table R1-1 Defect Report (optional) 1. Cell s ID number: Layer # Box # Block # Cell # 2. Classification of defects: No. Defect Name Description Yes or No Note 1 Broken cell Cells with broken areas 2 Cracked cell Cell with visible cracks 3 Chip or divots Cells with chips 4 Holes Holes in cells 5 Others 3. Record images of abnormal sample cell (Defect inspection device may use a non-destructive device in 6.3.1 ) 4. Defect condition: 4.1 Defect size: Length μm ( Width μm ) 4.2 Defect description: (such as single simple crack, branch, multiple branches, tree-like cracks, web-like cracks, shatterlike cracks, point defect, fissure, line cracks, angled cracks, curved cracks, etc.) Page 12 Doc. 5204 SEMI
NOTICE: Semiconductor Equipment and Materials International (SEMI) makes no warranties or representations as to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The determination of the suitability of the Standard or Safety Guideline is solely the responsibility of the user. Users are cautioned to refer to manufacturer s instructions, product labels, product data sheets, and other relevant literature, respecting any materials or equipment mentioned herein. Standards and Safety Guidelines are subject to change without notice. By publication of this Standard or Safety Guideline, SEMI takes no position respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of this Standard or Safety Guideline are expressly advised that determination of any such patent rights or copyrights, and the risk of infringement of such rights are entirely their own responsibility. Page 13 Doc. 5204 SEMI