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Epoxy type encapsulation does not suffice in High Pressure High Temperature (HPHT) environment and hence is not suitable for harsh environment applications. In this work, alternative encapsulation methods exploring the use of thickened lid/base and a novel dome shaped cavity design would be discussed. Results show that such methods are viable and are possible alternatives for similar harsh environment applications.

As deep earth oil exploration transits into deeper earth, it faces challenges in producing reliable microelectronics devices and sensors that will not degrade under a higher temperature and pressure environment. Numerous physical issues limit the manufacturing of this type of reliable microelectronics devices, especially those related to packaging materials and assembly of the microelectronics devices. One of the key requirements in reliability will be a continuous operating time of more than 500 h at 300°C. It is reported that the mechanical performance of a high temperature Au-Ge eutectic alloy is able to fulfill the minimum interconnection properties specified by the oil and gas exploration industry. However, the impact of thermal aging to Au-Ge eutectic alloy electrical property is not clear. The electrical resistivity of thermally aged Au-Ge eutectic alloys has been evaluated in this study. It is observed that the electrical resistivity decreases with thermal aging time until saturation. This effect is mainly contributed by the grain growth of Au, which results in a reduction in grain boundaries, thus causing a decrease in electrical resistivity. It has been determined that Au-Ge eutectic alloy is a suitable interconnection material in term of its electrical property to be used for high temperature electronics packaging.

The concept of Multichip module (MCM) packaging is popularized for evaluating prototypes of novel devices and materials in extreme environmental conditions. The packaging for these types of electronics must be mechanically well-built and the metallization must be low in thermal conductivity in order to prevent the heat transfer from the external environment to the protected device. Strong bonding between metal and ceramic has been an issue of concern for many years due to delamination tendencies at the interfaces. This paper evaluates the adhesion characteristics of sputtered Copper (Cu) thin films to alumina (Al 2 O 3 ) substrates. The relationship between the surface roughness of the Al 2 O 3 substrate with appropriate surface treatment and the adhesion with Cu thin film is established experimentally. An adhesion layer with lower thermal conductivity and smaller coefficient of thermal expansion (CTE) mismatch such as Titanium (Ti) or Chromium (Cr) was also inserted in between to investigate the adhesion improvement of the metal-substrate. We have seen that Ti is essentially used as an adhesion layer between the bonding of Cu and Al 2 O 3 for electronic applications. With higher adhesion strength, and smaller CTE mismatch with Cu and Al 2 O 3 , insertion of Ti adhesion layer with optimum substrate surface roughness could lead to a more reliable packaging solution.

High temperature electronics for the exploration and monitoring of down-hole activities in geothermal wells and other oil and gas industry applications must operate reliably at a minimum temperature of 300°C for as long as 500 hours continuously. This study investigates if ceramic to ceramic bonding, using glass frit as the intermediate layer, is able to tolerate a high temperature environment of 300°C for 500 hours. Since glasses have the potential to join to ceramic due to chemical compatibility between the two materials, the use of glass frit for ceramic to ceramic bonding is considered a simple and yet robust method that is often used for hermetic sealing of microelectronic packages. The materials used in this study were alumina substrate and bismuth-based glass frit paste 4115DS-1Ha from Asahi Glass Company (AGC). The study includes an initial characterisation of the glass frit and evaluation of the shear strength of the bonding. The average hot shear strength (shear test performed at 250°C) for samples after thermal aging at 300°C for 500 hours was found to be 28.72 MPa. This value is approximately 3.6 times above the minimally required shear strength of 7.9 MPa according to the MIL-STD-883G specification. Further aging till 1000 hours showed only a 30% drop in shear strength to 19.72 MPa. Based on this study, the use of glass frit as a joining layer for ceramic to ceramic bonding for use in a high temperature environment was concluded to be qualified, at least from the perspective of shear strength retention.