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Die-attach properties of mechanical pressure-assisted sintered copper (pressure-sintered Cu) on some metallization layers in N2 atmosphere for high-power devices were investigated. The shear strength of pressure-sintered Cu on Ag plating increased as the bonding temperatures and bonding pressures increased. On the bonding conditions (2 MPa, 300 °C, 3 min and 60 min), the shear strength of pressure-sintered Cu on Ni and Ag plating increased with increasing bonding time, whereas that of pressure-sintered Cu on Au plating decreased. The decrease of shear strength on the Au plating was seemingly attributed to the marked interdiffusion of the interface between sintered Cu and Au plating.

The mechanical behavior of Al 2 O 3 -DCB and Si 3 N 4 -AMB power modules comprising copper sintered SiC-and Si-dice in liquid to liquid thermal shock cycles (LL-TSC) from −40°C to +200 °C is presented. SiC-MOSFET dice from two different vendors and Si-test chips were sintered with and without pressure under H 2- and N 2 -atmosphere onto the substrate. Shear values of pressure-assisted samples sintered at 12 MPa exceed 120 MPa. Dice sintered pressureless under H2 reached shear values of 60 MPa. Scanning acoustic and electron microscopy have been used to analyze the failure mechanisms caused by the LL-TSC. While pressureless sintered Cu-interfaces withstand 1000 cycles, pressure-assisted sintered Cu-interfaces survive 2000 cycles.

This paper describes the properties of GaAs PIN power diodes and demonstrates their utilization in a 650V 10kW LLC converter for fast charging of electric vehicles. The module comprises two SiC MOSFET half-bridges equipped with Rohm S4101 MOSFETs and the GaAs rectifier module packaged in an EconoPACK2 housing. The SiC half-brides and the GaAs rectifier are assembled on 0.38 mm thick zirconia-toughened alumina (ZTA) substrate with a bending strength of 700 MPa and a thermal conductivity of 27 W/mK. The SiC and GaAs semiconductors are silver-sintered onto a 0.3 mm measuring copper thick film layer on the top and bottom side of the substrate. The substrate is pressure sintered by a novel low temperature copper paste to the three mm thick copper base plate. The bow of the base plate with copper sintered substrates measures 200 μm and is comparable to the bow of soldered substrates. The thermal resistance of the GaAs module is calculated to 0.73 K/W. First electrical measurement at an output power of 0.5 kW reveal the extremely fast switching characteristic of the diode, which were validated by double pulse measurements.

this paper describes thermal stabilities (573 K for 8 h) of pressureless-sintered Copper (Cu) on four kinds of top metallization layers (Ni, Cu, Ag, and Au) by experiments. Evolutions of sintering process of Cu nanoparticles and diffusion coefficients of interfaces between a bulk Cu layer and metallization layers were also evaluated by molecular dynamics (MD) simulations. After aging at 573 K for 8 h in terms of bonding samples, the shear strengths of sintered Cu on Ni and Cu layer increased, whereas those of sintered Cu on Ag and Au layer decreased. It was confirmed that interdiffusion occurred in the interfaces between sintered Cu layer and Ag layer or Au layer by energy dispersive X-ray spectroscopy (EDX), which increased the porosities of sintered Cu near the interfaces. The increases of interfacial porosities on sintered Cu/Ag and sintered Cu/Au decreased the shear strengths. In contrast, the porosities near the interface between sintered Cu layer and Ni layer or Cu layer hardly changed after aging. MD simulations revealed that Kirkendall voids were promoted by higher interdiffusion coefficients and higher ratio of intrinsic diffusion coefficients between a bulk Cu layer and metallization layers, which consequently increased the porosities of sintered Cu near the interfaces. The interdiffusion coefficients, which seem to have a correlation with the shear strengths of sintered Cu, can be used as an index value to find metallization layers that are suitable for the sintered Cu layer by calculations of MD simulations.

this paper describes the sintering properties and bonding properties of copper (Cu) die-bonding sinter paste for power devices operating at high temperatures. The Cu paste can be sintered pressure less in 100% H2 or under pressure in 100% N2 atmospheres. The as-sintered density, thermal conductivity and resistivity of pressure less-sintered Cu (in 100% H2, 300 °C, 1 h) is found to be 7S%, 180 Wm^-1K^-1 and 4.3 $\mu\Omega\cdot cm$, respectively. The pressurelesssintered Cu has higher 0.2% proof stress than the pressure-sintered Ag (sintered density =87%, in air, 300 °C 10 MPa, 10min) as a comparison material in a three-point bending test. The die-shear strength of appropriate pressurelesssintered Cu on four different metal adherends (Cu, Ni, Ag and Au) was 30 MPa or higher. The die-shear strength of pressure- sintered Cu in 100% N2 was 36 MPa or higher. A thermal cycle tolerance of 1000 cycles or greater was shown in a power device test package which was bonded using the pressurelesssintered Cu and encapsulated with an epoxy molding compound. The Cu sinter paste can be used as a reliable die-bonding material for power modules operating at high temperatures.

The Compressed Baryonic Matter Experiment (CBM) investigates highly compressed nuclear matter, utilizing a Silicon Tracking System comprising 896 silicon sensors modules packed in eight layers with an overall area of four sqm. Each module consists of one sensor, 16 Read-Out Chips and 16 double-layer micro flex-cables, which are connected to the top and bottom side of the sensor. The cables are up to 50 cm long. They carry 128 signal traces on two layers at a pitch of 100 μm and a line-width of 25 μm. The layers are separated by a meshed core to reduce the cable capacity to 0.44 pF/cm. The cables are bonded onto one sensor by a pick and place flip-chip machine. The interconnection is realized by gold stud-bumps on the silicon and SAC solder bumps on the cable. The status of the sensor module and cable production process are presented.

Low-temperature low-pressure silver sintering is a die attachment process for highly reliable power modules. The quality of the sintered interconnection strongly depends on the properties of substrate metal, the die metallization and the sinter paste. This paper investigates the properties of chips sintered at 10 MPa and 250 °C on recently proposed gold layers, which are electrochemically deposited on nickel, palladium and silver layers in a mixed displacement and autocatalytic reaction. This specific deposition process leads to ENIG, EPIG ENEPIG and ISIG finishes comprising a gold layer of high purity, which was proven utilizing X-ray Photoelectron Spectroscopy (XPS) and FIB-SEM sections. Shear tests demonstrated the high quality of the sintered interconnection. Shear values at room temperature exceeded 80 N/mm2. After storing the substrate for two hours at 200 °C or for one hour at 350 °C prior to the sintering process shear values over 80 N/mm2 were measured. Gold layers deposited by this new process are very suitable for silver sintering processes and tolerant to various sinter pastes from different manufactures. Shear values derived from a paste of a different vendor exceeded 180 N/mm2, resulting in copper torn out of the DCB.

We present optical measurements of an optimized LED module consisting of 98 blue light emitting LED chips silver-sintered onto an aluminum nitride ceramic substrate within an area of 211 mm2. The module is cooled by a high performance microstructured water cooler. Using this cooler a maximum optical power density of 111.6 W/cm2 at a forward current of 3003 mA and 1255.6 W electrical input power could be achieved. Placing sintered glass discs doped with yellow phosphor in different concentrations in front of the module, white light with correlated color temperatures between 3600 K and 4200 K was produced.

Current research studies deal with the investigation of the thermal and optical properties of four LED modules on different substrate materials. The LED modules consist of arrays of 98 blue emitting LEDs with an emission wavelength of 457 nm within an area of 2.11 cm 2 . The modules are based on aluminum oxide or aluminum nitride substrates and the LED chips are attached by using a soldering or a pressureless silver sintering process. The modules are mounted on a high performance microstructured heat exchanger. By using the water driven cooler a maximum optical power density of 106.2 W/cm 2 at a forward current of 2100 mA and 837.5 W electrical input power is achieved. A saturation of the optical power density over the input current due to thermal degradation is not observed.

We present an improved cooling for a high power density UV LED module for a wavelength of 395 nm. The module consists of 98 LED chips soldered on a thick film printed alumina substrate on an area of 2.11 cm2. We investigated cooling by a commercial water cooler as well as by a surface micro cooler developed by our own. Further we describe a technology to replace alumina by aluminum as substrate material. A module consisting of 25 UV LEDs was optically characterized without and with liquid encapsulation. Finally we conducted numerical studies to develop an easily producible, sufficiently powerful, and robust water cooler. Based on the results we present a water cooler design with cooling channels embedded in the aluminum substrate of an LED module, removing the interface between LED substrate and heat sink.