Electroflight, a technology and engineering services organisation specialising in bespoke aerospace battery systems, approached the MTC’s Manufacturing Support Services (MSS) team to conduct a project looking into improvements in battery cell cleaning.
The business, which operates in the aerospace and defence sectors, had recently conducted a study into wire bond reliability and strength following investment into new wire bonding processes. This research identified battery cell cleanliness as a major factor. Electroflight recognised that its existing manual methods of cleaning battery cells were labour intensive and caused issues with variability and challenges with scalability.
The MTC were tasked with identifying new cleaning methods and technologies to improve the cleaning process and subsequently enhance the wire bond weld strength and bonding strength consistency.
Laser cleaning was identified as the most suitable cleaning process and in the first phase of the project, the MTC investigated the feasibility of laser cleaning of the battery cell to remove oxidisation and contamination. A series of experimental trials were conducted and a total of 36 cells were laser programmed, cleaned and characterised, to assess the impact of the cleaning method on bond strength and variability.
Phase Two of the project focused on further optimising the cleaning process on both old and new cell batches. The results were compared against Electroflight’s existing manual wet chemistry and mechanical cleaning methods, and optimum laser cleaning parameters were established.
Following completion of the testing, the MTC identified an optimum laser power output to achieve targeted improvements in wire bond strength. This output resulted in a 130% increase in bond strength of the negative terminals and 40% increase for positive terminals, and a significant reduction in variability. The optimised cleaned cells also showed significant improvement on repeatability and pull testing performance of the cells during the wire bonding process.
Other factors that impacted wire bonding test results were also identified, such as variation in oxide layer thickness due to different batches of battery cells.
Following completion of the project, MSS introduced Electroflight to laser systems manufacturer IPG Photonics to support the adoption of onsite laser technology in-line with the findings from the MTC’s study.