- Category:
Materials Contributing to Thermal Management in Advanced Semiconductor Packaging (2)
Following Part 5
on thermally conductive materials such as thermal interface materials and epoxy molding compounds, this article highlights additional materials that help improve thermal management in advanced semiconductor packages.
Heat Dissipation Paths in 3D Packages 
Materials That Enhance Thermal Management
Capillary Underfill (CUF)
CUF is a resin used to fill the gaps between chips, interposers, and package substrates. It mechanically reinforces solder bumps and micro-bumps, preventing stress concentration caused by external shock, vibration, or substrate warpage. CUF also mitigates thermal stress arising from differences in the CTEs*1 between dissimilar materials such as chips and substrates—helping suppress fatigue and crack formation at the joints during thermal cycling.
Resonac offers a diverse lineup of CUF materials with varying modulus, CTE, and Tg*2, enabling us to recommend the optimal grade for each customer’s package structure and application requirements. We are also developing high–thermal–conductivity CUF grades that contribute to improved thermal management in advanced packages.
Appearance of CUF Product
Die Attach Film (DAF)
DAF is an adhesive film that serves two primary functions:
1)Wafer/die support during the dicing*3 process in front-end semiconductor manufacturing
2)Adhesion between chips, between chips and interposers, or between chips and substrates in advanced packages
Dicing methods include blade dicing using rotating diamond blades and laser dicing. For chips used in advanced semiconductor packages—where ultra-fine-pitch dicing and thin-wafer processing are required—laser dicing is preferred due to its high process yield. Because DAF is located directly beneath the chip or between stacked chips, high thermal conductivity is especially critical in advanced packages with significant heat generation.
Resonac provides DAF materials with a wide range of thicknesses, moduli, and thermal expansion properties, allowing us to propose the optimal grade based on each customer's dicing method and package type. Our DAF grades for advanced packages support laser dicing—including stealth dicing—and we are currently developing new products that achieve high thermal conductivity to contribute to efficient heat dissipation.
Appearance of DAF Product
Summary & Next Topic
In this article, we introduced Resonac's materials that contribute to thermal management in semiconductor packages. The application of these materials can significantly enhance package reliability. In alignment with the industry’s technology roadmap, we will continue to develop materials with even higher thermal conductivity and lower thermal resistance. Our next installment will focus on “Materials that Improve Warpage Control in Advanced Semiconductor Packages.”
Resonac Technology Roadmap for Thermal-Management-Related Materials 
*1CTE: Coefficients of Thermal Expansion *2Tg: Glass Transition Temperature *3Dicing: The process of cutting semiconductor wafers into individual dies
Published: March 25, 2026
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