High Speed Surface Modification in Fine-Pitch Package Substrate Manufacturing Process with High Density 60 Hz Nonequilib
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High Speed Surface Modification in Fine-Pitch Package Substrate Manufacturing Process with High Density 60 Hz Nonequilibrium Atmospheric Pressure Plasma Yoshiyuki Iwata1,2, Hajime Sakamoto1, Keigo Takeda2 and Masaru Hori2 1 R&D Operation, IBIDEN Co., Ltd., Gifu-Pref., Japan 2 Department of Electrical Engineering and Computer Science, Nagoya University, Aichi-Pref., Japan ABSTRACT This study examined surface modification of solder resist and dry film resist using 60 Hz nonequilibrium atmospheric pressure plasma with O2/N2 mixing gas. Results show that the plasma discharge condition at O2/N2 mixing ratio of 0.1% was the best for surface modification for both materials, and the surfaces were modified sufficiently at 0.45 m/min package substrate transportation speed. From the plasma diagnostics by Vacuum Ultraviolet Absorption Spectroscopy (VUVAS) and Optical Emission Spectroscopy (OES), it was found that the behaviors of the oxygen radical density and NO-γ emission intensity correlate strongly with surface modification. The extremely high oxygen radical density around 4.7 × 1013 cm-3 was obtained at O2/N2 mixing ratio of 0.1%. The electron density was 2.5 × 1015 cm-3 that is two digits more than that of the conventional atmospheric pressure plasma such as Dielectric Barrier Discharge (DBD). The solder resist surface with the plasma treatment was analyzed by X-ray Photoelectron Spectroscopy (XPS), and it was clarified that material surface was modified by hydrophilic group generation owing polymer chain oxidation with oxygen radical. INTRODUCTION Fine patterning of the fine-pitch package substrate is accelerated with down-sizing of high-density electronics products such as a personal computer, LSI package, LSI devise, etc. [1] The requirement of Line / Space will be less than 10 um / 10 um in 2014 [1]. The manufacturing process of the patterning has to be developed in order to sustain the sufficient process yield for the requirement [2]. Substrate patterning is processed by photolithography using photosensitive dry film resist. After the photo exposure and developing the dry film resist, copper plating is processed. If the Line / Space is fine, the plating into the fine space is difficult because the plating solution does not enter into the fine space. Therefore, the surface modification of the dry film resist is necessary for plating the fine space by improving the surface wet-ability. With the surface modification, plating solution easily enters into the fine space, and the fine pattering can be processed successfully. Photosensitive solder resist is used as the cover layer of the substrate. C4 bump is formed after opening the solder resist. For the fine pitch requirement of C4 bump, solder resist opening has to be smaller. The under bump metal plating is processed after opening the solder resist. Therefore, the surface modification of solder resist is necessary for plating the under bump metal at small opening area by improving the surface wet-ability. These surface modifications are extremely important for fine-pitc
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