Sintering bonding using metal nanoparticles is considered a promising die-attach technique for high-temperature operating power devices, such as SiC. However, the thermal stress produced by the difference in coefficient of thermal expansion (CTE) between the chip and substrate, often affects the reliability of this technique. To address this limitation, we analyzed a sintering bonding using Ni nanoparticles and Al microparticles composite paste. The results revealed that the Al microparticles significantly reduced the voids and cracks in the bonding layer formed by Ni nanoparticles paste. Three chips with different sizes were bonded to Cu substrates, and the bonding strength was measured. The result revealed that the bonding strengths in the samples were higher than those of the samples bonded using conventional metal nanoparticles. In addition, the fracture observation after the shear test revealed that the Al particles suffered plastic deformation. Furthermore, the high-temperature storage test at 250°C confirmed the long-term bonding reliability.
In order to obtain ideal low Dk/Df film for 5G application, we have developed novel isotropic low Dk/Df film. Our newly modified PPE was soluble to organic solvents and crosslinked after curing. By formulating this new polymer and other components such as sillica filler, we have developed novel isotropic thermosetting film with low Dk/Df, high Tg, low CTE, low water absorption, high peel strength and HAST, which was supposed to be suitable film as substrate and interlayer insulating film for 5G packaging application.
Syndiotactic Polystyrene (SPS) has excellent electrical properties. So it has been strongly expected SPS to apply for Copper Clad Laminate (CCL) for high frequency use. We conducted to fabricate the CCLs using SPS films and electrolysis copper foils by using vacuum lamination process and considered the anchoring effects from mechanical properties of SPS film, copper foil's surface morphologies and XPS analysis. In addition, we examined total line losses for micro-striplines. It was defined that the sufficient anchoring effect resulted from softening of SPS film over Tg and the peel strength depended on the fine nodule shape and the existent of silicon atoms on the copper foil matte surfaces. And it was observed that the correlation between the losses and the size of nodules on them. We specified the suitable electrolysis copper foil for CCLs using SPS films for the high frequency use, which showed both sufficient bond strength and low electrical loss.
We propose silicon (Si)-photonics-embedded interposers as a novel packaging platform to achieve co-packaged optics. An interposer is an organic substrate that has Si-photonics transceiver dies buried in it and polymer optical waveguides connecting the embedded Si chips and optical connectors. We also developed a Si-photonics-device-embedding process and investigated the properties and operations of embedded Si-photonics devices as a feasibility study. The embedded arrayed waveguide grating and reflective optical filter showed a wavelength shift on the order of 0.1 nm with our embedding process. The shifts seem to be due to the difference in ambient temperature during the measurements and induced strain. Though this embedding process is presumed to affect the spectrum for Si-photonics devices, the difference is small enough to be controlled. Embedded Si-photonics transmitter- and receiver-integrated circuits successfully demonstrated 25-Gb/s operations. The proposed Si-photonics-embedded interposer is a promising candidate for a co-packaged optics platform to eliminate the interconnect bandwidth bottleneck for high-performance computing systems.
Non-destructive two- and three-dimensional neutron imaging was conducted for evaluation of small internal structure in the power module with double-sided cupper heat spreaders under thermal fatigue cycles. Although two-dimensional radiography could not visualize small internal structures, three-dimensional laminography was capable of the visualization. As an application, the commercially available power module was measured by neutron laminography before and after thermal fatigue. It was non-destructively found that the power module was free of degradation at least in the size of 100 µm for 1,000 cycles under this fatigue condition.