Inkjet-printed gold nanoparticulate patterns for surface finish in electronic package |
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Authors: | Seonhee Jang Hyejin Cho Seongkoo Kang Sungil Oh Donghoon Kim |
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Institution: | (1) School of Advanced Materials Engineering, Kookmin University, Jeongneung-dong, Seongbuk-gu, Seoul, 136-702, Republic of Korea;(2) MK Electron Co., Ltd, 316-2 Geumeoh-ri, Pogok-eup, Cheoin-gu, Yongin-si, Kyeonggi-do, 449-812, Republic of Korea; |
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Abstract: | Gold (Au) pads for surface finish in electronic package were developed by the inkjet printing method. The Au ink for printing
was prepared by Au nanoparticles (NPs) coated with capping molecules of dodecylamine (C12H25NH2). The microstructures of the inkjet-printed Au films were characterized after sintering in various gas flows. The film sintered
in air showed that bonding between NPs was not enough for further grain growth due to the incomplete decomposition of the
capping layer. The film sintered under nitrogen (N2) had NPs existing on the surface and the bottom which did not participate in sintering. When the film was sintered under
N2-bubbled through formic acid (FA/N2), a large portion of the pores were observed to make a holey pancake-like structure of the film. The microstructures of the
inkjet-printed Au film became denser with grain growth when Au NPs were sintered under mixed gas flows of FA/N2 and N2. The resistivity of film was 4.79 μΩ cm, about twice the bulk value. Organic analysis showed that about 0.43% of residual
organics was left in the film. Therefore, this Au film was chosen for solder ball shear test because the microstructure was
denser compared to the films sintered under other gasses such as N2 or FA/N2 and less organic residue was found from organic analyses. Even though the film sintered under N2 showed the best electrical property (4.35 μΩ cm), it was not adopted in the shear test because NPs remaining on the bottom
of the film could lead to the poor adhesion between the film and substrate and show low shear strength. The shear force was
8.04 newton (N) on average and the strength was 64 MPa. This shear strength is good enough to substitute the inkjet-printed
Au nanoparticulate film for electroplating in electronic package. |
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