SEMI PV38 - Test Method for Mechanical Vibration of c-Si PV Cells in Shipping Environment
This Standard was technically approved by the Photovoltaic Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on March 19, 2018. Available at www.semiviews.org and www.semi.org in August 2018; originally published September 2012.
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.
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.
The test result also can evaluate cell package performance during transportation.
Basic Test System Requirements — This Standard states the basic vibration test system requirements.
This Test Method covers the random vibration test of filled transportation unit, will be used to assess the performance of package design for mono/multicrystalline cells during shipping by different transportation vehicles.
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).
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.
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 the Appendix.
Referenced SEMI Standards
SEMI PV23 — Test Method for Mechanical Vibration of Crystalline Silicon Photovoltaic (PV) Modules in Shipping Environment