10 BATTERIES Korean aluminium alloy boosts thermal stability Researchers in Korea have developed an aluminium alloy for EVs that dramatically improves thermal stability, writes Nick Flaherty. The team at the Korea Institute of Material Science (KIMS) identified a new mechanism by which the nanostructures inside aluminium alloys work, and the alloys they have developed improve thermal stability by up to 140%, compared with existing aluminium ones. Aluminium enclosure materials deteriorate due to the heat emitted by batteries, leading to a significantly increased risk of accident as EVs age. Dr. Hyeon-woo Son and his team from the Department of Aluminium in the Advanced Metals Division at KIMS added trace elements to the existing 6000 series aluminium alloy. They set up a new database by introducing dozens of trace elements and analysing nanostructures using state-of-the-art techniques such as transmission electron microscopy (TEM) and 3D atom-probe tomography (APT). They confirmed that several elements can improve thermal stability. The team assessed the thermal performance of the AA6061 alloy with trace amounts of silver and germanium using hardness measurements, electrical conductivity tests, TEM and APT. Trace addition of Ge can increase electrical conductivity and thermal stability, but it also slightly deteriorates hardness during the early and peak ageing stages. Trace addition of Ag can enhance hardness during ageing, especially in the overageing stage, but it deteriorates electrical conductivity. As the ageing time was increased, the Ge atoms were incorporated into the precipitates in the alloy, resulting in better thermal stability. The research is significant in that it expands the database of thermal stability enhancement techniques and introduces new directions for alloy design. Stackable connectors that simply snap in place ENNOVI has developed a stackable, multi-row, boardto-board (BTB) automotive connector that snaps together without soldering, writes Nick Flaherty The ENNOVI-MB2B system uses a proprietary ‘snap-in biscuit’ design, which allows multiple connector units to be stacked together without soldering, and it is reliable enough to use in EVs. The design enables different pin count requirements to be accommodated via the same basic interconnect without any extra expense or engineering effort. The BTB connectors are based on ENNOVI’s patented, 0.4 mm miniPLX press-fit terminals, which are made from a copper alloy that exhibits low levels of contact resistance at under 1 mΩ. These have an insertion force of under 70 N and a ‘push-out’ force of over 15 N. Each pin has a 3 A current carrying capability and can be covered with ENNOVI’s IndiCoat plating technology to mitigate the build-up of tin whiskers, which can cause short circuits. The coating extends operational lifespan. ENNOVI-MB2B connectors come in board-stacking heights of 7-30 mm for Electric Power Steering (EPS) and Electronic Control Unit (ECU) functions in EVs. The connectors can have one to six rows, with up to 30 contact terminals being incorporated into each one. Conforming with automotive performance requirements, these rugged products can withstand high humidity levels (eight-hour cycling up to 10% RH), mechanical shock (35 g for 5-10 ms across 10 axes) and vibration (eight hours per axis). A working temperature range of -40 C to 150 C is supported. “Being able to fit enough interconnect terminal pins into a small space while not having any excess is a priority for clients [and] keeping total cost of ownership down is vital,” says Ralph Semmeling, product portfolio director at ENNOVI. CONNECTORS July/August 2024 | E-Mobility Engineering KIMS thermal materials ENNOVI’s connector doesn’t need soldering
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