An Assessment of Thermoset Injection Molding for Thin-Walled Conformal Encapsulation of Board-Level Electronic Packages

Abstract

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.

Reliability Study of Electronic Components on Board-Level Packages Encapsulated by Thermoset Injection Molding

“…A printed circuit board (PCB) of size 55 mm × 55 mm × 1.55 mm was used. To avoid the bending of the PCB during the overmolding process, as noticed in [1], boards made of a material with a high glass transition temperature (170 • C) were procured. A thermo-mechanical analysis (TMA) was carried out on a sample to confirm the transition temperature.…”

“…An assessment of thermoset injection molding for the encapsulation of PCBs with surface-mounted electronic components was presented in a previous work [1]. During that assessment, mold trials were package to protect itself from external harmful media and withstand or overcome adverse environmental conditions, is brought in by means of a board-level encapsulation.…”

“…An assessment of thermoset injection molding for the encapsulation of PCBs with surface-mounted electronic components was presented in a previous work [1]. During that assessment, mold trials were 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).…”

“…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].…”