**4. Production Concepts for Inductive Power Transfer Pads**

ter, process chains will be explained and suitable processes shown.

*4.1. Process Chain for IPT Pads* Charging pads consist of different components and materials which are manufactured, handled, and assembled in several production steps (Figure 4 (right)). The first step is the preproduction of the base parts and the housing. The functions of these parts are to position coils, electronics, and ferrites and to encapsulate the system (mechanically, chem-The current state of IPT pad production is characterized by small lot sizes and manual work. This often results in fluctuations of quality, which can induce lower power transfer efficiency, damage, or reduced service life expectancy. On the other hand, a higher demand leads to higher lot sizes and automated processes. In the following chapter, process chains will be explained and suitable processes shown.

#### ically, thermal, etc.). The following steps (winding and contacting of the high-frequency (HF) litz wires) *4.1. Process Chain for IPT Pads*

will be discussed in Sections 4.2 and 4.3. In another step, the mentioned ferrites and electronic packages must be assembled. The challenges of this production step include the careful handling and most precise dropping of the ferrites, which have tight tolerances, because the position influences the magnetic field. Charging pads consist of different components and materials which are manufactured, handled, and assembled in several production steps (Figure 4 (right)). The first step is the preproduction of the base parts and the housing. The functions of these parts are to position coils, electronics, and ferrites and to encapsulate the system (mechanically, chemically, thermal, etc.).

The following steps (winding and contacting of the high-frequency (HF) litz wires) will be discussed in Sections 4.2 and 4.3.

In another step, the mentioned ferrites and electronic packages must be assembled. The challenges of this production step include the careful handling and most precise dropping of the ferrites, which have tight tolerances, because the position influences the magnetic field.

With rapidly increasing demand for solutions for wireless charging systems, adaptive value chains with a gradually increasing degree of automation have to be created. To reach short cycle times, it is important to process a wide variety of materials safely and with high process stability. The multitude of fields of action for wireless charging systems from a production and material perspective also requires interdisciplinary manufacturing process development. With an initially low level of integration of the electronics in the charging modules, partial pre-assembly and separate delivery of the individual components (coil module, compensation, rectification, etc.) may be necessary, which is accompanied by complex final assembly. Since, above all, the logistics processes and the associated

costs have a significant influence on the further design of the modules, a higher level of integration is to be aimed at in later stages of development. It is also conceivable to integrate the systems into the battery modules, which for reasons of logistics (costs and safety of transport) tend to be produced very close to the final assembly plants. *Energies* **2022**, *15*, x 5 of 13

**Figure 4.** CAD model of a value-added chain [21] (**left**) and process chain of the IPT pad production (**right**). **Figure 4.** CAD model of a value-added chain [21] (**left**) and process chain of the IPT pad production (**right**).

With rapidly increasing demand for solutions for wireless charging systems, adaptive value chains with a gradually increasing degree of automation have to be created. To reach short cycle times, it is important to process a wide variety of materials safely and with high process stability. The multitude of fields of action for wireless charging systems Additional advantages arise in the case of integration of the electronics close to the target site by minimizing the high-voltage cabling expenditure and the synergetic use of already integrated cooling concepts to be able to ensure the required heat dissipation, especially in higher performance systems.

from a production and material perspective also requires interdisciplinary manufacturing process development. With an initially low level of integration of the electronics in the charging modules, partial pre-assembly and separate delivery of the individual components (coil module, compensation, rectification, etc.) may be necessary, which is accompanied by complex final assembly. Since, above all, the logistics processes and the associated costs have a significant influence on the further design of the modules, a higher level of integration is to be aimed at in later stages of development. It is also conceivable to integrate the systems into the battery modules, which for reasons of logistics (costs and safety of transport) tend to be produced very close to the final assembly plants. Additional advantages arise in the case of integration of the electronics close to the In the case of highly automated processing and handling of magnetic field guidance materials, e.g., ferrites, the risk of breakage of the brittle material must be considered. In addition to the development and construction of suitable litz-wire laying techniques for optimized winding patterns for better heat dissipation, methods for process-stable, large-series-capable contacting of the several hundred individual wires are to be developed for the high-frequency strands used. Current methods of thermal stripping and contacting via tin baths are not suitable for large series and automotive applications. For the following processes, appropriate buffer systems must be used to meet the required conditions for the curing process of insulation and potting materials and to ensure an approximately constant flow of the material.

target site by minimizing the high-voltage cabling expenditure and the synergetic use of already integrated cooling concepts to be able to ensure the required heat dissipation, especially in higher performance systems. In the case of highly automated processing and handling of magnetic field guidance materials, e.g., ferrites, the risk of breakage of the brittle material must be considered. In addition to the development and construction of suitable litz-wire laying techniques for optimized winding patterns for better heat dissipation, methods for process-stable, large-In the vehicle final assembly plant, the charging modules are installed in the underbody of the vehicle. At present, there are no vehicle concepts that have been completely designed for a contactless charging option, especially with regard to the body structures including the battery module in the underbody area. Optimal integration, ideally in the center of the underbody to ensure interoperability between vehicle models while preserving mechanical, electrical, chemical and thermal boundary conditions, will only be possible in future generations of vehicles.

series-capable contacting of the several hundred individual wires are to be developed for the high-frequency strands used. Current methods of thermal stripping and contacting via tin baths are not suitable for large series and automotive applications. For the follow-Within the next sections, the focus of the IPT pad production will be set on the winding, contacting and insulating technologies of HF litz wires.

#### ing processes, appropriate buffer systems must be used to meet the required conditions *4.2. Winding Technologies*

ble in future generations of vehicles.

for the curing process of insulation and potting materials and to ensure an approximately constant flow of the material. In the vehicle final assembly plant, the charging modules are installed in the underbody of the vehicle. At present, there are no vehicle concepts that have been completely designed for a contactless charging option, especially with regard to the body structures The difficulty in automated production of coils is represented by the various coil parameters. Particularly worthy of mention here are the 3D contour, the structure as a multi-coil system, multipole coils, systems with several HF-litz wires, the winding distance, various radii, winding tolerances, wire intersections and the positioning of the coil ends.

including the battery module in the underbody area. Optimal integration, ideally in the center of the underbody to ensure interoperability between vehicle models while preserving mechanical, electrical, chemical and thermal boundary conditions, will only be possi-
