Interview with Dr. Svenja Müller, TE Connectivity, and Dr. Marcella Oberst, TE Connectivity
“Standardised interfaces can reduce complexity”
Dr. Svenja Müller, left, studied engineering and management sciences and built her career at the intersection of product strategy, innovation and industrial technology development. Dr. Marcella Oberst studied electrical engineering at TU Dresden and earned her PhD at the Chair of High Current and High Voltage Engineering, focusing on electrical connections.
TE Connectivity
As electrification increases current loads and complexity in vehicle power distribution, reliable high-current connections become critical for safety and lifecycle cost. Dr. Svenja Müller and Dr. Marcella Oberst from TE Connectivity explain design rules, joining strategies and the new VDI 2231 guideline.
As electric vehicles require ever higher current levels and
more complex power distribution architectures, the reliability of high-current
connections in the wiring harness system becomes a
critical engineering challenge. Materials, joining technologies and
assembly quality increasingly determine lifecycle performance, safety and
serviceability.
Dr. Svenja Müller and Dr. Marcella Oberst, both from TE
Connectivity, work at the intersection of product strategy, development and
standardization for high-current connectivity solutions
in electromobility. Müller leads regional product management for
e-mobility solutions across Europe and India, while Oberst focuses on the
development of cell connectivity systems and high-current connection
technologies.
At the Bordnetzkongress 2026 in
Ludwigsburg, they will present their joint talk “Bolted High-Current
Connections in Electromobility – Market Overview and Contents of the new VDI
Guideline 2231”, providing insight into design principles, reliability
challenges and the upcoming industry guideline for high-current bolted joints.
In this interview, they discuss the future of wiring harness
automation, key joining decisions for copper and aluminium systems and the
engineering challenges behind reliable high-current connections in electrified
vehicles.
ADT: Looking ahead five years, what will be the single biggest challenge for the wiring
harness and EDS industry and why?
Dr. Müller and Dr. Oberst: Looking ahead five years,
the single biggest challenge for the wiring harness and EDS industry will be
the end-to-end automation of wiring harnesses. With an increased focus on
sustainability and the risks of disruption associated with global supply
chains, localised production is becoming more desirable. To achieve this while
facing intense and sustained cost pressure, full automation of EDS components
is necessary, despite high variant complexity and historically manual
production processes. In parallel, alternative conductor materials such as
aluminium or hybrid solutions must be deployed to reduce cost and CO₂ emissions
while maintaining long-term quality and reliability. Both
harness manufacturing and vehicle installation need to become more modular and
automation-friendly, enabled by zonal and simplified E/E architectures.
OEMs will continue to require just-in-time delivery, even as supply chains
become more fragile and transformation investments increase. CO₂ reduction must
be driven by lighter architectures, shorter wire lengths, lower scrap rates and
more energy-efficient production. At the same time, quality requirements are
rising, as the EDS is becoming increasingly safety-critical for ADAS and autonomous driving functions. Autonomous
driving further increases the need for reliability, functional safety and
controlled power and signal distribution, where automation can help eliminate
unnecessary redundancies. Overall, the core challenge is to deliver a highly
automated, low-carbon, cost-efficient and zero-defect wiring harness system at
scale.
Which material or joining decision being made today will
have the longest-lasting impact on reliability and lifecycle cost?
The choice of conductor material and, even more critically,
the joining technology between copper and aluminium will have the
longest-lasting impact on both reliability and lifecycle cost of wiring harness
systems. Aluminium-to-copper interfaces are unavoidable for cost, weight and
packaging reasons, but they represent the highest long-term risk if the joining
concept is incorrect. Mechanical bolted connections at aluminium–copper
interfaces offer major advantages for high-current and continuous-load applications:
they provide extremely low and stable contact resistance, are robust in
long-term operation and can be inspected, retightened or replaced over the
vehicle lifecycle if implemented correctly. Compared with permanent joints,
screwed connections provide superior serviceability, and compared with plug-in
connections they offer greater ageing robustness, especially under thermal
cycles and vibration. Plug-in connections remain essential where modularity and
assembly speed dominate, but they come with higher contact resistances due to
the significantly lower normal forces. Joints with atomic bonds, such as welded
or soldered connections, are indispensable for limited installation space and
weight-optimised designs, but they are irreversible and place very high demands
on material compatibility and process control. The key long-term decision is
therefore where to plug, where to screw and where to weld, based on current
load, safety relevance, accessibility and expected lifecycle stress. There is
no single best joining method; all are required, applied deliberately and
consistently. Getting this balance right today determines electrical stability,
serviceability, redundancy strategy and total lifecycle cost for decades,
especially in autonomy-ready vehicles with continuous operation and higher
safety requirements.
What problem is the new VDI 2231 guidance solving for
e-mobility high-current connections?
The most commonly used guideline when designing a bolted
connection is VDI 2230. However, this guideline applies to bolted connections
with purely mechanical loads and clamped parts made of high-strength materials.
Relatively soft materials such as aluminium and copper, as well as the function
of carrying high currents, are not within the scope of this guideline. As the
challenges for such connections are different, for example due to the high
thermal loads caused by electrical currents, many OEMs and suppliers have
developed their own internal guidelines for how such connections should be
designed and tested. VDI 2231 will be the first publicly available guideline
specifically addressing these high-current connections. Questions such as which
conductor and plating material combinations can be safely combined in a bolted
joint, how the very small contact resistances of a bolted connection can be
measured reliably, and which steps should be taken to ensure long-term
stability of the electrical and mechanical properties of the connection will
all be addressed in the guideline. The goal is to create a common understanding
and enable high-quality connections with minimal additional effort for the
engineers working on such joints.
Which design and assembly mistakes cause most field
failures in bolted joints and how can they be prevented systematically?
Most field failures in bolted joints are caused by design
and assembly mistakes. A common error is joining materials that are not
compatible for long-term electrical stability, as well as insufficient
attention to surface contamination. In contrast to plug-in connections, where
sliding motion during insertion can displace some surface contamination, in a
bolted connection the surfaces are simply pressed together. In addition, the
surfaces are typically not plated as they often are in plug-in connections. Contamination
from external materials, such as oils and dust, as well as oxide layers that
are naturally present on surfaces, especially on bare aluminium and copper
busbars, can significantly affect electrical performance. Even thin films on
contact surfaces can degrade electrical performance and long-term reliability.
Awareness of surface cleanliness and sufficient surface pre-treatment to ensure
low contact resistance initially and throughout the lifetime of the connection
are therefore critical. Another common issue arises during assembly. If, for
instance, a screw is inserted at an angle, the required torque might be reached
without achieving the necessary contact normal force. Such misalignments can be
prevented through highly controlled assembly processes or through system
designs that prevent them entirely, as can be seen for example in TE
Connectivity’s BCON+ connector with its guiding elements. Systematic prevention
therefore requires joint designs that take expected challenges into account as
well as clean and controlled assembly processes.
How should engineers think about preload retention over
lifetime under thermal cycles, vibration and relaxation?
Over the lifetime of each connection, the preload must
remain sufficient to ensure stable electrical performance. The tension
introduced during assembly will gradually decrease due to creep and force
relaxation. A very important influencing factor is the selection of the alloy,
including its composition and temper condition, which determines the softening
temperature of the system. Depending on material selection and the stresses
experienced by the system over its lifetime, measures can be taken to ensure
sufficient preload retention, for example through the use of spring elements.
These are particularly important when relatively soft aluminium conductors are
exposed to high temperatures or when structured surfaces are used to break up
oxide films, as in the uniTE contact element. Adequate testing should always
accompany the design of a bolted connection. In addition to long-term testing
under thermal load, hysteresis testing can be helpful to determine not only how
resistance decreases with increasing force but also the point at which the
contact spots become unstable again and therefore which force needs to be
maintained. A common mistake is to test vibration and relaxation separately. A
better approach is to first conduct thermal ageing to induce creep and
relaxation in the system and then perform vibration testing. This approach
tests the more critical path and increases the probability of ensuring the
stability of the connection.
Where do you see the market moving, towards more
standardisation of interfaces or more OEM-specific connection concepts?
The market is moving in both directions, but not uniformly
across all voltage and application areas. Several years ago, there were serious
attempts to standardise tab sizes and interfaces, but progress was slow and
often limited in impact. One reason is that optimisation through
standardisation takes time, while OEMs are simultaneously pushing rapid E/E and
architecture evolution. As a result, there is currently limited interest in
strict standardisation in areas that are still undergoing strong technical development.
OEMs increasingly favour OEM-specific connection concepts to differentiate
architectures, packaging and performance. This is especially true for
high-power and safety-critical applications, where requirements differ
significantly. In contrast, the low-voltage domain continues to see ongoing
standardisation efforts, driven by cost pressure, economies of scale and mature
technology. Here, standardised interfaces can reduce complexity and improve
supplier flexibility without limiting innovation. Although standardisation has
clear benefits in accelerating automation and reducing costs through simplified
processes and scale effects, the current near-term trend favours OEM-specific
system solutions with only selective standardisation at the component and
low-voltage interface level.
Finally, what do you personally hope to take away from
the Bordnetzkongress 2026 in Ludwigsburg?
We are particularly excited about the networking
opportunities at Bordnetzkongress 2026. The conference provides an invaluable
platform to exchange practical experience on integrating high-voltage systems,
discuss emerging technologies and gain cross-industry perspectives from OEMs,
suppliers and technology providers.
