Fine Pitch Cu Pillar with Bond on Lead (BOL) Assembly Challenges for Low Cost and High Performance Flip Chip Package

Islam, Nokibul; Pandey, Vinayak; Kim, KyungOe

doi:10.1109/ectc.2017.216

Cited by 8 publications

(1 citation statement)

References 5 publications

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“…Packaging technology has been developing towards high performance, low power consumption and high packaging density, such as POP, 2.5D packaging by interposer and 3D packaging [2][3][4]. The diameters of solder joints have been reduced from hundreds of microns to tens of microns [4,5]. There are many problems when using Sn alloys for interconnection, such as the short circuit caused by the overflow of melted Sn in the bonding process and the growth of Sn whisker [6,7], and the open circuit caused by Kirkendall voids [8].…”

Section: Introductionmentioning

confidence: 99%

Patterning Ag nanoparticles by selective wetting for fine size Cu-Ag-Cu bonding

Liang¹,

Li²,

Li³

et al. 2020

Nanotechnology

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Metal nanoparticles (NPs) are promising bonding materials to replace Sn alloys in fine size Cu-Cu bonding. However, the method of rapidly patterning NPs on solder joints with sizes less than 30 µm is one of the main barriers that impede the practical applications of NPs in Cu-Cu bonding, especially in mass production. In this paper, a novel method of patterning Ag NPs on Cu pads by selective wetting was introduced. Cu pads with diameters down to 5 µm were coated with Ag NPs successfully. When sizes of Cu pads were larger than 10 μm, high density could be achieved and the ratio of diameters to pitches of Cu pads could reach 2/3. Furthermore, the thickness and the coverage of the Ag NPs layer could be raised by repeating coating. In the bonding test, the shear strength increased significantly with the increase of the bonding temperature and the bonding time. It could reach 22.92 MPa after sintering for 5 min at 250 °C under a bonding pressure of 20 MPa in N2. With the aforementioned advantages, patterning NPs by selective wetting will be one of the potential methods for applying NPs to Cu pads in Cu-NPs-Cu bonding.

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