SKiN technology is a flexible foil used in place of wire bonds and, in combination with sinter technology, can help double inverter power density, leading to a 35% reduction in inverter volume. This high power density requires space-saving and uncomplicated means of connecting the power components with the driver unit. The driver terminals thus use spring contacts affixed to the surface of the flexible foil. SEMIKRON looks back on ten years of experience with spring-contact technology, with more than 500 million SEMIKRON spring contacts in field applications today.
Spring contacts are solder-free and affordable electrical connection technology. Module to PCB connection does not require sophisticated equipment – instead, the PCB is simply screwed onto the module, creating the electrical connections. A further benefit is that the connection can be easily undone at any time, resulting in service-friendly systems. Unlike solder joints featuring through-hole or press-fit technology, spring contacts are rather flexible as regards their positioning, facilitating PCB layout considerably. This delivers optimum, dynamic performance and removes the need for additional internal connections which might impair module reliability. The power terminals are not connected to the DC link using standard screw connections but are joined in a state-of-the-art laser welding process. This enables space-saving and reliable integration into the liquid-cooled inverter system. Thermal paste is responsible for around 30% of the overall thermal resistance in an electronic system, which is why it is a key factor in the electric and thermal dimensioning of a power electronics system. With SKiN technology, the thermal paste layer between the DCB and heat sink is replaced by a silver sinter layer, improving thermal conductivity between chip and heat sink by 35%.
The key fields of application for SKiN technology in the future will be compact systems in the automotive and wind power sectors where liquid-cooled systems are used. The resultant compact, lightweight inverters will give our customers an important competitive edge. For instance, thanks to SKiN technology a 3 MW wind power converter can now fit in a single switch cabinet for the first time ever.