Survey of High-Temperature Polymeric Encapsulants for Power Electronics Packaging

Abstract

Semiconductor encapsulation is crucial to electronic packaging because it provides protection against mechanical stress, electrical breakdown, chemical erosions, α radiations, and so on. Conventional encapsulants are only applicable below 150°C. However, with increasing demand for high-density and high-temperature packaging, encapsulants that are functional at or above 250°C are required. In this paper, five types of encapsulants, including conformal coatings, underfills, molding compounds, potting compounds, and glob tops, are surveyed. First, recommended properties and selection criteria of each type of encapsulant are listed. Second, standard test methods for several crucial properties, including glass-transition temperature (T g ), coefficient of thermal expansion (CTE), dielectric strength, and so on are reviewed. Afterward, commercial products with highoperation temperature are surveyed. However, the results of the survey reveal a lack of high-temperature encapsulants. Therefore, this paper reviews recent progress in achieving encapsulants with both high-temperature capability and satisfactory properties. Material compositions other than epoxy, such as polyimide (PI), bismaleimide (BMI), and cyanate ester (CE), are potential encapsulants for high-temperature (250°C) operation, although their CTE needs to be tailored to limit internal stress. Fillers are reported to be efficient in reducing the CTE. In addition, fillers may also have a beneficial impact on the thermal stability of silicone-based encapsulants, whose high-temperature capability is limited by their thermal instability. IndexTerms-Encapsulant, high-temperature, plastic integrated circuit packaging, power electronic packaging, semiconductor device packaging.

THz-TDS for IC packaging material changes detection under real-world conditions

“…Epoxy, silicone, and polyurethane are common encapsulant materials that are used in different working conditions with different working temperature. 13 Encapsulants based on polyurethane can be utilized for sample working temperatures below 165 • C. They are capable of providing satisfactory chemical and mechanical stability and stiffness for IC packaging up to their working temperature. Epoxy is a frequently employed thermalsetting encapsulant material that can withstand temperatures up to C. This makes them highly desirable for high-performance and harshenvironment applications, which typically involve hash working temperatures.…”

Integrated motor drives: state of the art and future trends

“…The module undergoes high thermal and thermo-mechanical stresses at high temperatures leading to critical failures in the system [135,136]. Degradation of polymeric materials used in the module packaging as well as the creation of intermetallic compounds, which may weaken the joints also occur at high temperatures [124,137,138]. Categories of interest in power module packaging areinterconnects, die attachment, substrate choice and encapsulation [139].…”

Integrated motor drives: state of the art and future trends

“…The module undergoes high thermal and thermo-mechanical stresses at high temperatures leading to critical failures in the system [135,136]. Degradation of polymeric materials used in the module packaging as well as the creation of intermetallic compounds, which may weaken the joints also occur at high temperatures [124,137,138]. Categories of interest in power module packaging are -interconnects, die attachment, substrate choice and encapsulation [139].…”