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...

Thermoset materials offer a multitude of advantageous properties in terms of shrinkage and warpage as well as mechanical, thermal and chemical stability compared to thermoplastic materials. Thanks to these properties, thermosets are commonly used to encapsulate electronic components on a 2nd-level packaging prior to assembly by reflow soldering on printed circuits boards or other substrates. Based on the characteristics of thermosets to develop a distinct skin effect due to segregation during the molding process, the surface properties of injection molded thermoset components resemble optical characteristics. Within this study, molding parameters for thermoset components are analyzed in order to optimize the surface quality of injection molded thermoset components. Perspectively, in combination with a reflective coating by e.g., physical vapor deposition, such elements with micro-integrated reflective optical features can be used as optoelectronic components, which can be processed at medium-ranged temperatures up to 230 °C. The obtained results indicate the general feasibility since Ra values of 60 nm and below can be achieved. The main influencing parameters on surface quality were identified as the composition of filler materials and tool temperature.

Todays continuous improvement and advancement in the injection molding process for plastics allow for increasing reliability of the process parameter control, whereas the fluctuations of the material properties still present a great challenge. To compensate for these fluctuations, a nozzle capillary rheometer is developed with the aim to determine the viscosity inline during the injection process in series production applications. An essential part of this work is the signal processing and the definition of a suitable integration boundary to ensure a reliable signal evaluation. In addition, based on mathematical modeling and established correction factors, it is possible to determine the effective viscosity accurately without the need to replace the capillary channel according to the Bagley correction.