Joerg Franke

Optimized thin-film diffusion soldering for power-electronics production

This paper gives an overview on diffusion soldering or transient liquid-phase soldering (TLPS), where the conventional electronic production processes have been optimized for being capable of producing highly durable pore-free TLPS bonds. The growth of intermetallic phases (IMP) with control of temperature and time has been investigated in production line perspective. The samples processed under optimized vacuum based vapor-phase soldering along with realization of thin solder layers down to less than 10μm are demonstrated. As a result, pore-free diffusion soldered joints filled with Cu6Sn5 and Cu3Sn phases near the chip-substrate interface have been realized. Formations of IMP with changes in optimized solder profile, solder paste, chip metallization, substrate roughness and solder paste thickness are discussed.

Capability of biopolymers in electronics manufacturing

The present study aims to display new opportunities for flexible printed circuit boards (FPC) in electronic manufacturing by using biopolymers based on renewable materials as substrate material. Therefore, four different biopolymers, polyhydroxybutyrate (PHB), cellulose acetate (CA) and two different copolymers of polylactid acid and thermoplastic polyester elastomer (PLA+TPC), were processed with the standard process chain of the electronic manufacturing. Thereby, the main focus of attention was the thermal behavior during the hot embossing and reflow soldering in a vapor phase reflow soldering oven. Furthermore, manufactured FPCs were put in a temperature-humidity-test for 200 hours. The aim is to identify the weaknesses of current available biopolymers in order to improve future biopolymers for using in the electronic manufacturing.

Innovative needle winding method using curved wire guide in order to significantly increase the copper fill factor

The increase of the copper fill factor is an essential production goal in stator winding technology in order to increase the degree of efficiency and the power density of electrical machines. Orthocyclic winding patterns allow the highest packing density. Currently for round-wire-windings there are only systems available on the market that facilitate random windings, which leads to a decrease of the fill factor. Therefore this paper introduces a concept allowing high fill factors for distributed windings by using the needle winding technology.

Electrical functionalization of thermoplastic materials by Aerosol Jet Printing

Aerosol-Jet-Printing is an interesting approach to apply circuit tracks on three dimensional thermoplastic circuit carriers used for Molded Interconnect Devices. Therefore, possibilities for printing nanoparticle silver inks on substrate materials that meet the requirements for basic automotive applications were investigated from the view of manufacturing. Out of four different substrate thermoplastics (grades PA6.6, PA6, special PA6, and PBT/ASA) commonly used in automotive applications plate specimens with three different levels of surface quality according to molding tool manufacturing were generated. Conductor tracks printed onto the substrates consist of eight single printed lines arranged with different pitches. The setting of the pitch turns out to be an important influence on the conductivity that can be achieved at the thermoplastics substrates. Hereby the influence of irregular wetting due to the surface characteristic of the molded circuit carriers can be reduced. The investigated materials and different surface roughness show a constant performance during thermal shock for 1000 cycles in the range of −40 °C and +125 °C. While an exposure to humidity heat (85% r.h / 85 °C) for 504 h has only marginal effects on the conductivity, the adhesion of the printed structures on the thermoplastics substrates is reduced significantly during this test. Nevertheless, the highly promising results provide base for further investigations to achieve sufficient adhesion for mounting electronic components and to evaluate new inks and adaptions of the Aerosol-Jet-Process.

Advanced substrate and packaging concepts for compact system integration with additive manufacturing technologies for high temperature applications

Additive manufacturing is one of the key technologies which poses as an energy and resource efficient alternative of conventional subtractive and formative technologies. In this contribution, additive layered manufacturing mainly selective laser melting (SLM) is investigated to check the potential for system integration and packaging concepts. This paper gives an overview on the limitations of conventional molded integrated devices for high temperature applications. For high temperature stability, ceramic substrates were additively functionalized with copper based powder material using SLM technique. Focus of the work lies in the melting of the metal powder directly on ceramic substrate and producing a reliable metal-ceramic bond. The process influencing parameters such as laser power, velocity, scan concepts were tested to check the bonding characteristics. Initial shear tests and current carrying tests were performed to check the mechanical and electrical stability. The proof-of-concept was demonstrated by developing a prototype in automotive lighting application. The potential of SLM for high-temperature applicability is further discussed.

Investigations on ultrasonic copper wire wedge bonding for power electronics

Driven by applications in the field of renewable energy, power distribution, consumer electronics and the automotive industry, the demand for reliable and economic power electronics packaging solutions is growing rapidly. The present study aims to display a new technology for chip top-side interconnects by using heavy wire copper wedge/wedge bonding. Therefore a response surface design of experiment study was set up to evaluate the influence of the main parameters time, ultrasonic power and bond force on the bond process quality. With this information an optimized set of machine parameters was derived, with respect to maximized pull and shear forces. Furthermore, investigations on the correlation between the bond parameters and the destructive test failure modes were conducted. All tests were accompanied by a monitoring of the tool wear-out. This allows to assess the process stability as well as the process reliability. The aim is to identify the most significant parameters and to find an optimized parameter set in order to improve future die interconnection technologies for power electronics manufacturing.

Energy-efficient production strategies and technologies for electric drives

Due to the scarcity of resources the sustainable production of electric drives has become more and more important. In the context of a potentially huge increase in the demand for electric traction drives by the market of e-mobility, this topic is even more challenging. For this, new topologies with lower requirements for the needed valuable resources, new energy efficient drive concepts, optimized production, and logistic processes in terms of their resource requirements and integrated recycling strategies are presented in this paper.

Electrical functionalization of thermoplastic materials by cold active atmospheric plasma technology

Plasmadust® is a new technology using cold active plasma for additive metallization of different substrate materials. For electronics production, in particular Molded Interconnect Devices (MID), thermoplastic materials can be structured with copper as power electronic conductive pattern. The main advantages of Plasmadust® are the controllable process temperature range between about 90°C and 180°C, the good adhesion of the metallization, the fast process speed of about 100 mm/s and the fast growing conductor tracks with about 15 microns thickness per cycle. Plate specimens were made of PA, a thermoplastic commonly used in automotive applications, with different process parameters. Conductor tracks applied onto the substrates consist of one line with different electrical and mechanical properties according to the process temperature and process speed. Additionally, the thickness and the width of the conductor track depend on the process parameters. The setting of the process speed turns out to be an important influence on the thickness and roughness of the conductor track that can be achieved on thermoplastic substrates. The investigated combination of thermoplastic and copper shows a constant bonding performance during thermal shock testing for 1000 cycles in the range of -40°C and +125°C. An exposure to humidity heat (85% r.h / 85°C) for 500 h has only marginal effects on the adhesion of the printed structures on the thermoplastic substrates, too. This highly promising results provide the base for further investigations to achieve a sufficient ampacity related to standard chemical PCB metallization processes.

Methodical integration of assembly specific influences concerning high-voltage components into the virtual validation process

The future competitive situation in the automotive industry and the increasing market demands will inevitably lead to higher complexity in product development, production planning and pre-series. Longer lifecycles of assembly systems based on highly flexible production cells with a rising number of integrated processes call for new challenges, especially for production engineering. One key challenge for gaining important time and cost potentials in production engineering projects is an early virtual validation during the pre-series. Under the premise to replace physical mock-ups by digital mock-ups, we will present requirements and solutions of a virtual validation focused on manual assembly of high-voltage components in the automotive industry. We want to integrate the electric drive used for electric and hybrid vehicles into the computer aided design based virtual validation process. This paper presents a product and process validation methodology for a prototype electric drive, using a virtual human model. For this, an electric drive is dismantled and the necessary assembly steps are identified. Further, two process-steps, i.e. packaging of electrical sheets and insertion of magnets, are selected and a virtual validation concept is developed. Using a virtual human model, ergonomics are included as an essential part of the product and process validation methodology.

Production concepts for inductive power transfer systems for electric vehicles

Constantly rising fuel prices more and more encourage the development of innovative electric vehicle concepts. In order to follow this trend and to increase customer acceptance and the practicality of electro-mobility, vehicle concepts with inductive power transfer systems are developed. These have to be integrated into the production lines of the car manufacturers with in each case several adaptations depending on the different types of electric vehicles. Therefore, different vehicle integration concepts and cost-efficient value chains need to be created in order to allow an early start of production to sell such vehicles.