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Due to many advantages, such as cost-effective production, design freedom, and weight reduction, plastics have replaced metals and ceramics in many fields. However, engineering plastics are good thermal insulators. This characteristic, although beneficial in certain applications, poses many challenges in many heat-generating applications. This can lead to hot spots or even to an increase in the device temperature. Along with the increasing demand for plastics in areas of the lighting technology or in the automotive field due to the free shaping potential, the requirements are becoming more challenging. Driven by the trend of miniaturization, applications with high heat generation often have to operate in the tightest of spaces. Since not always sufficient space for complex cooling systems is given, the housing or the substrate should assume the task of thermal management. In regard to this fact, the use of thermally conductive thermoplastics seems to be very appealing. Quality loss, poorer reliability, loss of performance, and even failure can occur in case of insufficient heat dissipation. In order to improve the properties of these polymers, highly heat-conducting fillers are added in order to improve the thermal conductivity of the compound. Another technology trend that has been prevalent for years is the use of simulations. Due to shorter product life cycles and therefore shorter development times, simulation has become an indispensable part of the chain of product development. Timeconsuming and costly test series make the simulation more and more important as a tool for material and product design. In this context, this paper presents a novel approach for reliability investigation and lifetime estimation, based on simulation. Therefore, a simulative method based on coupling the results from the process simulation (injection molding simulation) to finite element analysis was developed and explained. This coupled method makes it possible to take into account the manufacturing process and its engendered filler orientation. The obtained findings are compared to conventional thermal steady-state analysis and used in order to better predict the lifetime of LEDs mounted on thermoplastic substrates, the so-called molded interconnect devices. It is demonstrated that it is necessary to consider the filler orientation, especially in the case of 3D substrates.

An ever-growing market demand for board (second) level packages (e.g., embedded systems, system-on-a-chip, etc.) poses newer challenges for its manufacturing industry in terms of competitive pricing, higher reliability, and overall dimensions. Such packages are encapsulated for various reasons including thermal management, protection from environmental conditions and dust particles, and enhancing the mechanical stability. In the due course of reducing overall sizes and material saving, an encapsulation as thin as possible imposes its own significance. Such a thin-walled conformal encapsulation serves as an added advantage by reducing the thermo-mechanical stresses occurring due to thermal-cyclic loading, compared to block-sized or thicker encapsulations. This paper assesses the encapsulation process of a board-level package by means of thermoset injection molding. Various aspects reviewed in this paper include the conception of a demonstrator, investigation of the flow simulation of the injection molding process, execution of molding trials with different encapsulation thicknesses, and characterization of the packages. The process shows a high dependence on the substrate properties, injection molding process parameters, device mounting tolerances, and device geometry tolerances. Nevertheless, the thermoset injection molding process is suitable for the encapsulation of board-level packages limiting itself only with respect to the thickness of the encapsulation material, which depends on other external aforementioned factors.

A drastically growing requirement of electronic packages with an increasing level of complexity poses newer challenges for the competitive manufacturing industry. Coupled with harsher operating conditions, these challenges affirm the need for encapsulated board-level (2nd level) packages. To reduce thermo-mechanical loads induced on the electronic components during operating cycles, a conformal type of encapsulation is gaining preference over conventional glob-tops or resin casting types. The availability of technology, the ease of automation, and the uncomplicated storage of raw material intensifies the implementation of thermoset injection molding for the encapsulation process of board-level packages. Reliability case studies of such encapsulated electronic components as a part of board-level packages become, thereupon, necessary. This paper presents the reliability study of exemplary electronic components, surface-mounted on printed circuit boards (PCBs), encapsulated by the means of thermoset injection molding, and subjected to cyclic thermal loading. The characteristic lifetime of the electronic components is statistically calculated after assessing the probability plots and presented consequently. A few points of conclusion are summarized, and the future scope is discussed at the end. carried out as a part of a chalked out design of experiments (DoE) with PCBs of different transition temperatures (125 • C and 170 • C) and different encapsulation thicknesses (0.25 to 1 mm) to evaluate the implementation of thermoset injection molding as an alternative to other dominant methods for the purpose of the encapsulation of board-level packages. An example of such an encapsulated package is shown in Figure 1. The definition of levels of packaging (here, 2nd level package) is taken from [2] and was also summarized in [1]. As mentioned already in [1], extensive literature is not available on this particular topic (encapsulation of 2nd level packages with the help if thermoset injection molding). Extensive research is, however, available in the field of 1st level packaging with encapsulations manufactured by transfer molding [3,4] and as a part of the Cornell injection molding program (CIMP), especially report 16 [5]. Further literature is also available relating to wafer-level encapsulations [6][7][8][9]. An approach for the reliability analysis can be derived according to a standard operating procedure used for microsystem technology in the automotive sector, as also used in [10]. This procedure is explained in the Sections 2.4 and 2.5. Useful tips and relevant information about board-level reliability of different components (without 2nd level encapsulation) are available in different sources [11][12][13][14][15][16][17][18][19]. These sources lay out the best practices used for defining and testing board-level reliability, involving the reliability analysis of commonly used components like ball grid arrays (BGAs) [13,16], quad-flat no-leads packages (QFN) [11,15], and thin small outline packages [17]. The effect of...