Study of glass interposers for co-packaging electronic and photonic chips
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Date
2025
Authors
Gupta, Parnika
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Publisher
University College Cork
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Abstract
In recent years, glass interposers have received significant attention within the microelectronics industry. This interest is primarily driven by their potential for scaling to panel-level packaging, which can reduce the cost of advanced packages. This ability to scale, coupled with excellent thermal dissipation, high optical quality, and superior electrical performance, makes glass interposers especially advantageous for photonic package integration, representing an exciting opportunity in the industry. This thesis presents a comprehensive thermal and electrical analysis of glass interposers for 2.5D electronic-photonic packages. It explores various thermal management strategies aimed at enabling the co-packaging of electronic and photonic chips within glass interposer-based packages. Additionally, the thesis investigates the electrical losses associated with different elements, including transmission lines, through-glass vias (TGVs), microvias, and ball grid array (BGA) structures.
Firstly, the efficacy of thermal Through-Glass Vias (TGVs) in dissipating heat from a laser chip bonded to a glass interposer is demonstrated by achieving a temperature reduction of approximately 120°C. This significant cooling effect is evident due to the laser chip’s high heat flux density. This cooling efficiency can be further enhanced by optimizing the copper filling within the TGVs. Secondly, reference thermal chips are introduced as cost-effective and widely available heat sources for evaluating heat dissipation through glass interposers. These reference chips are utilized to assess the impact of TGV pitch variation on the thermal performance of the glass interposer. The influence of design parameters of TGVs, microvias, and BGAs on the electrical losses through glass interposers is also examined.
Furthermore, the author further discusses the thermal stabilization of photonic packages, which can be achieved through a novel structure called Substrate Integrated Micro-TEC (SimTEC). This structure features TGVs partially filled with copper and thermoelectric materials, with interconnects on the top and bottom of the glass interposer acting as the hot and cold sides of the SimTEC device. The impact of TGV design variations on the cooling capability of SimTEC is analyzed through simulations. Besides TGVs and SimTEC as thermal management strategies, which facilitate heat dissipation through the glass interposer, heat removal from the topside of electronic chips bonded to the glass interposer is demonstrated using copper clips. These clips spread heat away from the electronic chip, emphasizing the importance of a heat dissipation pathway to establish contact between the copper clip and the heat sink. Finally, design rules are formulated which are aimed at enabling effective thermal management and electrical transmission in glass interposers.
Further investigation is needed to determine the optimal method for integrating package-level cooling solutions, such as heat sinks and micro-TECs, with system-level cooling solutions. Research aimed at facilitating seamless interaction between these cooling solutions with minimal thermal resistance is encouraged. The author also recommends conducting reliability analyses of glass interposers from both thermo-mechanical and photonic perspectives.
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Keywords
Glass interposer , Through Glass Vias , Photonic packaging
Citation
Gupta, P. 2025. Study of glass interposers for co-packaging electronic and photonic chips. PhD Thesis, University College Cork.