A package substrate whose core is a sheet of glass instead of glass-fiber-reinforced resin. Because glass is flat and dimensionally stable, it is being developed to form fine wiring and dense through-vias even in large packages.
Japanese name: ガラスコア基板
Glass core substrate appears in 1 practice question across 1 topic, including Advanced packaging (3D and chiplets).
High-performance processor packages mostly use build-up substrates, in which resin dielectric layers and copper wiring are stacked on both sides of a core made of resin-impregnated glass fiber. As substrates grow to carry several chips and HBM stacks for AI, warpage with temperature and shrinkage or expansion during processing become problems, and alignment gets harder as wiring becomes finer. A glass core substrate replaces that core with a thin glass panel, using glass's very flat surface, stiffness and dimensional stability under heat to combine fine wiring with large substrate sizes.
The coefficient of thermal expansion of glass can be chosen by adjusting its composition, which makes it easier to manage warpage and stress caused by expansion mismatch with the chips on top and the board below. The two faces are connected by through-glass vias (TGVs), holes made by laser or similar methods and filled with copper, which aim to be finer and denser than the drilled holes in organic cores. Glass is also generally a low-loss dielectric, which suits high-speed signaling.
Glass is brittle and can chip or crack during handling and processing. Around copper-filled TGVs in particular, each temperature change creates stress from the expansion mismatch between copper and glass, which can start microcracks. Stress from the wiring layers built on both faces can also cause cracking. Adhesion of copper and resin to glass, uniform via filling, the low thermal conductivity of glass and the limited long-term reliability data are further challenges.
In September 2023 Intel announced glass substrates for next-generation advanced packaging and said it aimed to bring them to market in the second half of the 2020s. It cited better flatness and thermal and mechanical stability than organic substrates, allowing much higher interconnect density in the substrate. Other substrate and glass makers are also developing the technology, and countering brittleness and achieving yield in volume production are key to practical use.
Answer: B. The thermal expansion coefficients of copper and glass differ greatly, so stress builds around the TGVs with each temperature change
A glass core substrate replaces the organic core of a package substrate with a glass panel; because it is flat and dimensionally stable, it is expected to allow fine wiring even on large substrates. Glass is brittle, however, and around copper-filled TGVs each rise and fall in temperature repeatedly applies stress from the expansion mismatch between copper and glass, which can start microcracks. Stress-relieving structures and materials, strengthened glass and long-term reliability verification are challenges for practical use.
A glass core substrate uses glass as the core of the package substrate, with wiring layers built above and below it to connect the chips to the printed circuit board. A glass interposer uses glass instead of a silicon interposer as an intermediate layer that connects chips to each other at high density. Their roles differ, but both use TGVs to connect the two faces.
It is flat and dimensionally stable and resists warpage, so fine wiring and dense through-vias are easier to form even on large substrates. Its thermal expansion can be tuned by composition, and its low dielectric loss suits high-speed signals.
Glass cracks easily. Stress from expansion mismatch concentrates around copper-filled TGVs and can start cracks, and glass can chip during processing and handling, so stress management, adhesion and long-term reliability must be addressed.
A glass core substrate replaces the organic core of a package substrate with a glass panel; because it is flat and dimensionally stable, it is expected to allow fine wiring even on large substrates.
In a glass core substrate, what is the main reason cracks t…As an Amazon Associate I earn from qualifying purchases.
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