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|Photosensitive Polyimide having low loss tangent for RF application|
|Keywords: polyimide, dielectric constant, dielectric loss|
|Toward an establishment of the high-speed large-capacity communication, practical use of the communication in the 5G technical format to use the higher frequency for is pushed forward1). In addition, frequency more than 60GHz is used in the millimeter wave radar which is effective for the collision avoidance of the car2). In order to decrease its size, a fan-out type wafer level package (FO-WLP) attracts attention about the package of the semiconductor. The materials that permittivity, dielectric loss are small are necessary for rewiring of this inside to use the FO-WLP with high frequency3). Polytetrafluoroethylene and a liquid crystal polymer are known as a low dielectric constant, low dielectric loss materials, but these have difficulty in those poor adhesiveness, poor fine pattern formation. Photo BCB was applied for re-distribution layer of FO-WLP4). However, the BCB has poor mechanical properties and narrow process window. We became the low dielectric constant, and low dielectric loss examined molecular structure of the polyimide toward becoming it and found that permittivity 2.6 at 20GHz, materials design to dielectric loss 0.002 were possible. Furthermore, in consideration of mechanical characteristics such as the ductility, adhesiveness for copper, I added examination about minute workability. An electric nature largely turned worse when I gave photosensitivity, but I designed the exposure groups, and it was permittivity 2.8, dielectric loss 0.005 while having photosensitivity, and break ductility 100%, the burning temperature developed the thing that 250 degrees Celsius was as follows until now, too. As well as varnish, a B stage sheet is available for becoming it, and these materials are applicable to re-wiring material of FO-WLP, insulation material of Interposer.|
|Masao Tomikawa, Research Fellow