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|Development of Low Dk and Df Polyimides for 5G Application|
|Keywords: Low Dk and Df, Polyimide, Photosensitive|
|The next generation of broadband telecommunication 5G is being paid much attention in order to meet the requirements for boosting signal transmission rate and managing a huge data flood and various development works relating to 5G including data processing, electronics package, materials, and so on have been reported recently. With regards to electrical performance of insulation materials, low Dk (dielectric constant) and Df (dielectric loss) are highly preferred for 5G application. From this view point, polytetrafluoroethylene (PTFE) or benzocyclobutene (BCB) look promising and being tried to use in electronics packages. However, these materials don’t have enough adhesion or mechanical properties to ensure the reliability. On the other hand, polyimides (PIs) have been widely used for electronics packages owing to excellent adhesion and mechanical/thermal performances. Especially, photosensitive PIs also have an advantage of easier assembly processing and that’s why photosensitive PIs are now being adopted for dielectrics use of re-distribution layers in wafer level packages (WLPs). However, in terms of expanding the versatility of photosensitive PIs to 5G application, further improvement of Dk and Df is strongly required with keeping the other performances good. Based on this background, we have newly developed non photosensitive and photosensitive polyimide having excellent electrical/mechanical properties. At first we have re-designed the polymer backbone to obtain low Dk and Df. As a result, our new non photosensitive PI achieved 2.9 of DK at 20 GHz and 0.003 of Df at 20 GHz. In the next step, we selected the photo package of new PI carefully to maintain both low Dk/Df and high resolution. After that, we modified the photo initiator content, crosslinker content, and so on to have both high lithographic performance and high electrical performance. As a result, new photosentive PI cured at 375 degC showed 3.0 of DK at 20 GHz and 0.005 of Df at 20 GHz. In addition, this material cured at 200 degC also showed 3.0 of DK at 20 GHz and 0.009 of Df at 20 GHz. We also confirmed high mechanical properties of new PI and elongation of this PI cured at 200 degC was approximately 100 %. From lithographic aspects, new PI achieved < 20 μm via opening with 10 μm thickness. Details will be discussed in the presentation.|
Hitachi Chemical DuPont MicroSytems,Ltd