Prototype Circuit Boards: Design in the Morning, Test in the Evening

Solar Car Project of the Bochum University of Applied Sciences Utilizes LPKF Circuit Board Plotter

Solar Car Project of the Bochum University of Applied Sciences

© LPKF Laser & Electronics AG · 2014 2

Ultra-fine structures with up to 100 µm

Shorter development time for the PowerCore SunCruiser

For over a decade now the Bochum University of Applied Sciences’ Solar Car Project has been conceiving, design-ing and manufacturing solar vehicles. When developing highly precise electrical systems, prototype circuit boards are critical. The students rely on production of circuit board prototypes for the “PowerCore SunCruiser,” the fifth model from the school. This is important, particularly for checking the circuits. LPKF Laser & Electronics AG sup-ports the Bochum Solar Car team with milling tools, drills and chemical-free through-hole plating.

Since the end of the 1990s, the Solar Car Project of the Bochum University of Applied Sciences has been develop-ing vehicles that are powered exclusively with solar ener-gy, initially as a research training project together with a partner institution, London South Bank University (LSBU), and since 2003 as an independent problem-based learn-ing (PBL) research training project. With this special teaching concept, the students assume more and more responsibility in the accumulation of knowledge, while the teacher mostly accompanies them, but also provides the infrastructure and materials.

The participants are students from the third semester and above, from the most varied disciplines including Electri-cal Engineering, Mechatronics, Mechanical Engineering and Computer Science. Each year the 30-member team changes but the know-how is passed on from solar car to solar car so that a regular transfer of knowledge takes place on a technologically high level.

The victorious five

Under the direction of the first German Professor of Electromobility, Prof. Friedbert Pautzke, the Bochum Solar Car Project has conceived, planned and produced five solar-powered light-weight electric vehicles over the last decade. All of them are energy self-sufficient, so there is no power input or additional combustion of fossil fuels. While the first models with the distinctive “rolling Ping Pong table design” are race cars, the latest devel-opments are going ever more in the direction of suitabil-ity for daily use. Their vehicle concepts take into account dimensions similar to those of passenger vehicles, con-ventional entrances (via side doors instead of a hinged upper shell), a self-supporting body instead of a two-shell design and a trunk, for example.

The Bochum Solar Car Project works at the cutting edge of current research and development. It and is unique in Germany, because there is no other solar car that is

Successful as a team: The committed students see the physical results of their work – here, the brand-new PowerCore SunCruiser.

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engineered and made in Germany. Their many awards and prizes reflect the fact that the vehicles from the Bochum solar car factory meet the highest technical standards. Since 2001, the solar cars such as “BOcruiser,” “Solar-World No. 1” and “HansGo!” have been receiving awards and winning international competitions (e.g. European Solar Challenge, North American Solar Challenge, Tech-nical Innovation Award, World Solar Challenge, Global Green Challenge). The latest example is the “SolarWorld Gran Turismo,” which has circled the world as the first completely self-sufficient solar car. With its tour of four continents and 29,710 km in 414 days (from Oct. 26, 2011, to Dec. 15, 2012), the student-built solar car even made it into the Guinness Book of World Records.

The new PowerCore SunCruiser is now going to partici-pate in the World Solar Challenge 2013. The competition is regarded as the most demanding solar vehicle race in the world. The race track is on public roads over about 3,000 kilometers across Australia from Darwin in the north to Adelaide on the south coast. Debuting at this year’s World Solar Challenge will be a new competitive class initiated by the Bochum team: the Cruiser Class, exclusively for cars with four wheels and at least two persons that are suitable for daily use. The PowerCore SunCruiser is of course included. The three-seater from Bochum has seven doors (two driver and passenger doors each, a trunk lid and two service doors for maintenance) and has all the components that a vehicle needs to be street legal in Germany – from blinkers and windshield wipers to lights.

Module production for the PowerCore SunCruiser

LPKF Laser & Electronics AG has counted the Bochum University of Applied Sciences among its customers since September 2011. Thus students in the fields of Electrical Engineering and Computer Science in the Central Elec-tronics Laboratory are already working with a ProtoMat S63 circuit board plotter from LPKF. At the beginning of December 2012, Bochum University of Applied Sciences’ Solar Car team asked the LPKF Rapid PCB Prototyping Sales Management about professional accessory items for manufacturing the PowerCore SunCruiser. LPKF sup-ports the non-commercial project and supplies many tools at no charge, such as sintered plates for the vacu-um table.

Whether motor controller, battery management, light, telemetry, array or display module: the students in the Solar Car Project design circuits for all electronic compo-nents of the solar vehicle. Then the planned layouts have to be transferred from strip conductors to circuit boards. This is done in a negative process: the engineers in train-ing mill insulating areas from the circuit boards coated over the entire surface with the LPKF circuit board plot-ter. The conductive material is removed. The insulating channels replicate the contour of the strip conductors and soldering surfaces.

Depending on the insulation distance or surface, the suitable milling heads are chosen automatically by the LPKF ProtoMat. Thus circuit board prototypes for check-ing new circuits or testing or optimizing standard circuits are created for all modules of the PowerCore SunCruiser. Each individual module passes through test phases in which possible errors are analyzed and eliminated and other optimizations are worked out.

Before acquisition of the circuit board plotter, circuit boards were produced in the Central Electronics Labora-tory through an etching process, requiring a noticeably longer preparation and processing time. Jan Hintz, Elec-trics Team Leader of the Bochum University of Applied Sciences Solar Car Project, says: “Due to the new produc-tion process, it is possible for us to produce prototype circuit boards in a highly precise and environmentally friendly fashion and without chemicals. That sold us on it.” The prototype circuit boards thus have a key role here in making the electrical system of the solar vehicle fail-safe.

Solar Car Project of the Bochum University of Applied Sciences

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Building circuit boards: more quickly, more simply, more precisely

The LPKF ProtoMat S63 is the all-rounder for in-house rapid PCB prototyping and is suitable for nearly all appli-cations – from milling or drilling of one- and two-layer circuit boards, HF or microwave substrates all the way to multilayers with up to eight layers. The circuit board plotter mills the circuit board structure from a base mate-rial that is coated over the entire surface. In the process, the high rotary speed of the milling spindle (60,000 rpm) above all allows very fine structures up to 100 µm – a basic precondition for modern electrical systems such as those in solar cars. The circuit boards produced are therefore more compact and light, and that is important for the high energy efficiency required of the vehicles.

Along with the high precision, the fast milling spindle also facilitates reduced processing times. Another advantage is the fact that the automatic change of up to 15 milling and drilling tools during the production process takes place automatically, without an operator. One of the development goals was disburdening the operator of control and adjustment tasks – and that has been suc-cessful due to an assistant-supported mode in the control software.

Moreover, the Solar Car team is impressed by the fact that the components can be placed by hand on the milled circuit boards and are easy and error-free to solder. “The students benefit above all from the fact that new ideas can be implemented or tested with the LPKF circuit board plotter in just a few hours. That saves us a lot of time for development,” explains Jan Hintz. “As an example, we needed a simulation for the switches and sensing devices of the instrument panel. In the morning we had the idea for a circuit board, by midday it was ready and we could actually use it by the evening.” In many cases, the proto-type can be directly taken over into vehicle operation as a functional component.

In this way, the LPKF circuit board plotter in the Bochum University of Applied Sciences Solar Car Project contri-butes to substantially reducing the production times of circuit board prototypes and thus the entire product development process.

The circuit boards created as prototypes often can also

be used in the vehicle.

Press contact:

LPKF Laser & Electronics AG

Marketing/Communications,

Malte Borges malte.borges@lpkf.com Osteriede 7 Tel. +49 (0) 5131 7095-327, 30827 Garbsen Fax +49 (0) 5131 7095-90 Germany

LPKF Laser & Electronics AG produces machines and laser

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