Sinter Bonding – Maximum Reliability for High-Performance Applications
Power electronics is one of the fastest-growing market segments, driven by e-mobility and renewable energy. A central challenge is increasing power density, efficiency, and lifespan while simultaneously reducing production costs. Wide-bandgap semiconductor materials such as SiC and GaN offer new possibilities with high switching frequencies and low switching losses, but they also require more reliable interconnection technologies.
Traditional die-attach methods, such as soft soldering, quickly reach their limits: creep deformation reduces reliability, and temperatures above 250 °C become unmanageable. The solution is sintering using silver- or copper-based interconnection layers. This technology offers excellent thermal stability as well as outstanding electrical and thermal conductivity, enabling better cooling and lower heat losses.
TRESKY die-bonding systems process silver sinter pastes using both high-pressure and low-pressure methods—similarly simple to solder pastes. Die transfer films can also be used. Over the years, numerous processes for different sinter material combinations have been successfully developed on our platforms.
For low-pressure or pressureless sinter pastes, a two-step process is often used. First, the paste is applied to the substrate using a dispensing or screen-printing method.
The T-5500 die bonder then picks up the die—either from a waffle or gel pack or directly from the wafer—and places it precisely into the sinter paste bed with a defined, low force. During this step, the bonding tool is briefly heated to a programmed temperature of around 200 °C to attach the die to the substrate.
In the second step—which can take significantly longer—the assembly is cured in an oven. The microscopic metal particles fuse together in a controlled diffusion process, forming a strong, durable bond.
If cycle time is not critical, the entire process can also be carried out directly in the T-5500. In addition to the heated bonding tool, a temperature-controlled substrate holder with programmable profiles is available—ensuring maximum process stability and consistent quality.
The alternative method works under high pressure and is typically executed in a single step with shorter cycle times. It uses high-pressure sinter pastes, where the entire process takes place within the die bonder. Higher pressures of 10 MPa or more are applied at typical temperatures of 230 °C for several minutes. The T-5500 die bonder can deliver programmable forces of up to 1000 N, providing the required pressure for chip sizes up to approximately 7 × 7 mm². Higher temperatures of up to 400 °C are also possible for various sinter pastes, using programmable temperature profiles for both the bonding tool and the substrate holder.
A more recent technology uses die transfer films instead of sinter pastes. These can be handled by our die bonders similarly to flux-dipping of dies. The die is first placed onto a die transfer film preform of the correct size. The film is then lifted from its carrier together with the die, before being positioned on the substrate—again with programmable force and temperature to fix it in place.
There are additional applications for sintered surfaces on the top of the semiconductor chip, not just on the bottom. Semiconductors operating at higher temperatures are preferably contacted with copper wires, as conventional aluminum wires exhibit significantly lower reliability at the desired operating temperatures. The main drawback of copper wires, however, is their greater hardness compared to aluminum, which subjects the chip surface to much higher mechanical stress during wire bonding, reducing reliability.
A newly developed and attractive solution is a mechanical bonding buffer layer made of copper with an applied silver sinter layer. This layer is applied to the die by the die bonder and simultaneously sintered to the substrate in the same process.
