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September, 2019 Blind Spot: Battery Interconnect Strength Testing Continued from page 60 Using micron-precise x, y, and z


axes the tool is optically aligned next to the test point. Next a test proce- dure is programmed that defines the measurement parameters, including test height, speed, over-travel, and the end-of-test detection point. The most advanced bondtesters


can be programmed to automatically align, test and even record images or videos of the entire test. The test equipment is sensitive enough to per- form non-destructive testing to extremely low forces. While production ready, these


tests are also an invaluable tool for R&D personnel when testing and validating new battery designs that combine different connection materi- als, along with new types of cell forms or layouts.


Identifying Cause of Failure To understand how an intercon-


Example images of wirebonds, ribbons and tabs.


nect has failed, the bonded site can be analyzed post-test to give detailed information on the adhesion and reli- ability of the original interconnect. This means a process engineer can record and understand which ele- ment of an upstream process may need settings altered to improve the bond adhesion. Testing the bond in more than


Error Free Bond Testing


one direction is required to fully characterize a bond’s quality and reliability. Both shear and pull tests simulate different loading conditions that could be experienced by a bat- tery within a vehicle, which experi- ences bumps and shunts from all directions. The pack design considerations,


such as cell orientation and bond length and direction, will not always be the same. Cells are often “float- ing,” loosely held within flexible poly- mers in a pack for thermal expansion purposes, which can exert 3D stress- es on the interconnect. Geometries of the connection itself can lean towards only shearing or only pulling on the connection. However it is still important not to neglect the opposing load condition. Shear loading of the intercon-


Remove all errors with our automated Bondtesters


nect will help to imitate a lateral load, whereas pull will simulate a tensile load. The battery connections can be characterized in two modes and each given different levels of information. Destructive testing is used for new product development to characterize new welds or bond processes or batch quality tests. Non-destructive testing is used for safety assurance by testing 100 percent of all connections, before use in a final product. Emerging automobile technolo-


Take control with automation


Operator free handling Eliminate alignment errors Remove handling issues Maximum traceability


Find out more at www.nordsondage.com/4600


Operator free testing Take away operator bias No tool displacement errors Highest test repeatability


gies like electric powertrains, autonomous control systems, driver health monitoring, remote engine shut down, and live car tracking require high levels of battery power. As vehicles integrate more electron- ics, the need for more advanced bat- teries is increasing. In addition, vehi- cles move in a harsh, ever-changing environment of vibration so any loose connections could be dislodged and lead to battery failure and potential- ly even burst into flame. Battery interconnects between


cells can become the weak link in the entire EV if the bonding process has not been successful. Similar to the bondtesting quality assurance proce- dures that are well established in the semiconductor industry, the emer- gence of mechanical stress testing of cell interconnects can play a pivotal role in ensuring EVs achieve the high- est safety standards, as part of a wider test suite in a battery production line. Contact: Nordson DAGE, 2370


Oakridge Way, Suite B, Vista, CA 92081 % 510-683-3930 E-mail: sales@nordsondage.com Web: www.nordson.com r


See at The Battery Show,


Booth 2901, and at SMTAI, Booth 407


See at SMTAI, Booth 407, The Battery Show, Booth 2901, and IMAPS, Booth 210


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