Manufacturers of power electronics still rely on soldering. Standard power electronics modules are typically assembled by soldering with lead-free SnAg solder and wire-bonded with thick aluminum wire. In these techniques, the simple handling, low material costs and flexible integration into various processes offer an advantage. But what is enough for many standard applications is reaching its limits in modern technologies. This is because the demands made by new applications such as electromobility or renewable energies have risen enormously. Even a perfect solder joint may no longer meet the requirements. The materials used must support higher power densities and switching frequencies, and at the same time, the demands on the reliability of high-performance electronic modules are growing. Automobile manufacturers, for example, require the supplier industry to make products with a service life of at least 15 years or 250,000 km. Sintering with silver offers a solution. It also can overcome higher operation temperature restriction. A solid material until 961 °C, Ag has a significantly higher melting point than tin-based, lead-free solders. Incorporating filler technologies, sinter supports higher thermal operating temperatures of more than 250 °C, as they remain thermomechanically stable and show almost no signs of aging. This is what makes high operating temperatures possible in modern power electronics. The silver particles of the sinter paste densify by means of diffusion processes. When heated above 230 °C and together with applied pressure of between 5 MPa and 30 MPa the density increases. The pressure ensures that porous areas in the compound layer are reduced, which is particularly important for large-area semiconductors. After sintering, no cleaning is necessary, unlike in soldering processes.
The next step: Sintering is the key to future power electronics
In modern power electronics applications, requirements are becoming more demanding. Soldered connections are reaching their limits. Sintering is increasingly becoming indispensable. Dennis Ang, sintering expert at Heraeus, knows what challenges the new technology introduces and what users must consider when making the transition.