High-temperature Packaging Applications Research Articles

Pressureless transient liquid phase sintering bonding in air using Ni and Sn–58Bi for high-temperature packaging applications

High heat-endurance bonding has become an important technology requisite for the demands of SiC die attachment or other high-temperature packaging applications. Transient liquid phase sintering (TLPS), which is a promising candidate among high heat-endurance bonding technologies, has been widely studied in recent years. Because the advantages of TLPS bonding are short bonding time, low bonding pressure, and low cost. In this study, in order to bond in air condition and low temperature, TLPS pastes using Ni, Sn–58Bi, and flux were fabricated with various weight ratios. Pressureless TLPS bonding processes were conducted in an oven at 220 °C for 60 min in air. The thermal behaviors of TLPS pastes (before bonding) and TLPS joints (after bonding) were analyzed by differential scanning calorimetry (DSC). The shear test was conducted for investigate about mechanical properties. The microstructures of cross-sectional and fracture surfaces were analyzed by field emission scanning electron microscopy (FESEM). Also, the atomic distribution of cross-sectional micrographs was analyzed by electron probe micron analyzer (EPMA) and electron dispersive spectrometry (EDS). After bonding, the residual eutectic Sn–Bi lamellar structure was observed only in Ni–90(Sn–58Bi). To verify the reliability of TLPS joints, the samples were stored in an oven at 200 °C for 100, 500, and 1000 h, and the shear test was conducted. The initial shear strengths of Ni–90(Sn–58Bi), Ni–80(Sn–58Bi), and Ni–70(Sn–58Bi) TLPS joints were 23.56, 17.23, and 5.47 MPa, respectively. After the high-temperature storage test, the decrease in shear strength was smallest in Ni–70(Sn–58Bi) and largest in Ni–90(Sn–58Bi). In conclusion, the optimum weight ratio of Ni and Sn–58Bi was Ni–80(Sn–58Bi) because of increased re-melting temperature (270 °C) and high bonding reliability compared to other conditions.

Electrical Performance of a 32-I/O HTCC Alumina Package for High-Temperature Microelectronics

A high-temperature cofired ceramic (HTCC) alumina material was previously electrically tested at temperatures up to 550°C and demonstrated improved dielectric performance at high temperatures compared with the 96% alumina substrate that we used before, suggesting its potential use for high-temperature packaging applications. This article introduces a prototype 32-input/output (I/O) HTCC alumina package with platinum conductor for 500°C low-power SiC-integrated circuits. The design and electrical performance of this package, including parasitic capacitance and parallel conductance of neighboring I/Os from 100 Hz to 1 MHz in a temperature range from room temperature to 550°C, are discussed in detail. The parasitic capacitance and parallel conductance of neighboring I/Os of this package in the entire frequency and temperature ranges measured do not exceed 1.5 pF and 0.05 μS, respectively. SiC-integrated circuits using this package and a compatible alumina circuit board have been successfully tested at 500°C for more than 3,736 h continuously, and at 700°C for more than 140 h. Some test examples of SiC-integrated circuits with this packaging system are presented.

Electrical Performance of a High Temperature 32-I/O HTCC Alumina Package

Abstract A high temperature co-fired ceramic (HTCC) alumina material was previously electrically tested at temperatures up to 550 °C, and demonstrated improved dielectric performance at high temperatures compared with the 96% alumina substrate that we used before, suggesting its potential use for high temperature packaging applications. This paper introduces a prototype 32-I/O (input/output) HTCC alumina package with platinum conductor for 500 °C low-power silicon carbide (SiC) integrated circuits. The design and electrical performance of this package including parasitic capacitance and parallel conductance of neighboring I/Os from 100 Hz to 1 MHz in a temperature range from room temperature to 550 °C are discussed in detail. The parasitic capacitance and parallel conductance of this package in the entire frequency and temperature ranges measured does not exceed 1.5 pF and 0.05 μS, respectively. SiC integrated circuits using this package and compatible printed circuit board have been successfully tested at 500 °C for over 3736 hours continuously, and at 700 °C for over 140 hours. Some test examples of SiC integrated circuits with this packaging system are presented. This package is the key to prolonged T ≥ 500 °C operational testing of the new generation of SiC high temperature integrated circuits and other devices currently under development at NASA Glenn Research Center.

Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - A Comparison Study with other Polycrystalline Alumina

A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thick-film metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500°C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

Transient liquid phase Ag-based solder technology for high-temperature packaging applications

Abstracts A lead-free Ag-based soldering technique through transient-liquid-phase (TLP) bonding is proposed in this study for high-temperature microelectronic packaging applications. The solder paste, which contained Ag and Sn powders with a no-clean flux, was used to join Cu substrates. The setup was bonded at 250 °C for 10 minutes. The study focuses on mechanical and microstructural characterizations of the joints. The shear strength measured at 250 °C shows good high temperature performance of the joint. The effects of Ag and Sn contents on mechanical, electrical and thermal properties of sintered bulk Ag–Sn samples were also investigated independently. The results demonstrate that the Ag–Sn TLP bonding is an effective interconnection method for harsh environment electronic packaging.

Microstructure and Sn Crystal Orientation Evolution in Sn-3.5Ag Lead-Free Solders in High-Temperature Packaging Applications

Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high-temperature packaging applications is of significant interest in power electronics for the next-generation electric grid. Large-area (2.5 mm × 2.5 mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5°C and 200°C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction in the scanning electron microscope. Comparisons were made between the observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution observed due to thermal cycling suggested a continuous recrystallization mechanism. Recrystallization behavior was correlated with dislocation slip activities.

Update on migration research and regulatory initiatives.

The Food and Drug Administration's (FDA) current research programme on migration from food packaging materials focuses on high-temperature packaging applications. Results from two studies conducted by Arthur D. Little, Inc., under contract to the FDA, are presented as well as highlights of the FDA's research programme on migration from microwave heat susceptor packaging. Some regulatory policy issues affecting the FDA's future regulation of food packaging materials are also examined.