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This paper compares thermal performance of glass and silicon interposers for mobile applications, using computational modeling. It is well known that while silicon is a good thermal conductor, glass is a poor conductor, potentially making it unsuitable for packaging applications. This study proposes to address this short coming of glass by comparing and contrasting with silicon. In this study, for more accurate thermal analysis, effective thermal conductivity of glass interposer substrates is measured by infrared microscopy. Subsequently, equivalent thermal conductivity of TPV (Through Package Via) is calculated through numerical analyses. For comparison of thermal performance of glass and silicon interposers, 2.5D interposer structures with logic and memory chips are considered. The comparison shows that by incorporating thermal vias, junction temperature for the glass interposer decreases by about 60%, while junction temperature for silicon interposer decreases 45%, making both acceptable. However, the glass interposer provides significantly better thermal isolation between logic and memory chips. Glass and silicon interposer structures placed in enclosures, representative of mobile applications, provide comparable performance in the presence of thermal vias. IntroductionThe 2.5D and 3D interposer technologies offer promising approaches for future microelectronic packaging, addressing miniaturization, cost and performance. These interposers connect multiple functional dies with a fine pitch microbumps and high density through-via interconnect technologies. In 2.5D technology, interposer, an intermediate substrate to which components are attached prior to PCB, is used to provide dense interconnections between multiple dies. Such a technology provides increased performance at reduced power consumption and yet enables thermal dissipation by enabling side-by-side, die to die interconnections, thereby improving the overall system performance.Silicon interposer technology is being developed to replace organic substrates whose performance is limited due to warpage, wiring density, number of I/Os, and acceptable cost. However, it faces a number of challenges, such as limited wafer size leading to high fabrication cost. Glass interposer has the potential to be the best packaging material except for its poor thermal conductivity. If this problem is addressed, It can replace organic substrates and silicon interposers due to a number of its advantages, including ultrahigh resistivity, low electrical loss, low dielectric constant, availability in thin and large sizes, and lower cost. This paper addresses the main problem with glass-its low thermal conductivity which can result in poor thermal dissipation. One

Purpose -The functionality of personal mobile electronics continues to increase, in turn driving the demand for higher logic-to-memory bandwidth. However, the number of inputs/outputs supported by the current packaging technology is limited by the smallest achievable electrical line spacing, and the associated noise performance. Also, a growing trend in mobile systems is for the memory chips to be stacked to address the growing demand for memory bandwidth, which in turn gives rise to heat removal challenges. The glass interposer substrate is a promising packaging technology to address these emerging demands, because of its many advantages over the traditional organic substrate technology. However, glass has a fundamental limitation, namely low thermal conductivity (~1 W/m K). The purpose of this paper is to quantify the thermal performance of glass interposer-based electronic packages by solving a multi-scale heat transfer problem for an interposer structure. Also, this paper studies the possible improvement in thermal performance by integrating a fluidic heat spreader or vapor chamber within the interposer. Design/methodology/approach -This paper illustrates the multi-scale modeling approach applied for different components of the interposer, including Through Package Vias (TPVs) and copper traces. For geometrically intricate and repeating structures, such as interconnects and TPVs, the unit cell effective thermal conductivity approach was used. For non-repeating patterns, such as copper traces in redistribution layer, CAD drawing-based thermal resistance network analysis was used. At the end, the thermal performance of vapor chamber integrated within a glass interposer was estimated by using an enhanced effective thermal conductivity, calculated from the published thermal resistance data, in conjunction with the analytical expression for thermal resistance for a given geometry of the vapor chamber. Findings -The limitations arising from the low thermal conductivity of glass can be addressed by using copper structures and vapor chamber technology. Originality/value -A few reports can be found on thermal performance of glass interposers. However thermal characteristics of glass interposer with advanced cooling technology have not been reported.