We investigated the formulations of acrylates which were applicable to UV-C LED lamps. The mixtures of acrylate monomers and photoinitiators were placed on silicon wafer or sandwiched between a silicon plate and a CaF 2 plate to obtain sample films. The films were irradiated by UV-C LED lamps which emit 265, 285, and 300 nm-lights. The effect of initiators, irradiation wavelength, and atmosphere on the conversion of the acryl unit was investigated using FT-IR spectroscopy. We found that the photoinitiator O-benzoyl 2,3-butanedione monooxime was the most effective photoinitiator for 265-nm light. The effect of atmosphere in the system was clearly observed.
Flip chip bonding process of the chip touch down at 40 o C and suppressing the material trapping at the joint area with the wafer level NCF (Non conductive film), which is pre applied underfilling film adhesive, has been investigated. The test vehicle wafer has 25 μm diameter and 50 μm height bumps which are 10 μm height Cu pillar and 40 μm height Sn-Ag solder cap. The bump pitch was 200 μm. The 55 μm thickness 50 wt% filler loaded NCF was laminated on the wafer and then the surface was planarized with the bump solder layer exposing by the bit cutting technique. Such prepared chip was bonded as the top chip to the bottom chip which has the 25 μm diameter pad of 3 μm Cu bottom, 2 μm Ni middle and 0.1 μm Au top. To insert the sticking step in the bonding process, which melts and flows down the NCF underneath the top chip to the bottom chip partially, the chips were held well the aligned position during the successive processes. The gang bonding possibility was also proved with the four chips together bonding. PCT (pressure cooker test, 121 o C and 100%Rh for 168 hours) was performed to the gang bonded samples. By shortening the joint formation step time form 25 to 5 seconds Cu diffusion into the solder bulk area was suppressed and the durable joint to the PCT was formed. It was confirmed by the cross sectional observations.
We investigated the formulations of epoxy resins which were used with deep-UV LED lamps. The mixtures of epoxy monomers and photoacid generators (PAGs) were placed on a silicon wafer to form films. The films were irradiated by deep-UV lamps which emit 265, 285 or 300-nm light. The effects of the PAGs, irradiation wavelengths, and film thicknesses on the reactivity were investigated by FT-IR spectroscopy and a photo-DSC study. We found that a sulfonium salt having a thiophenyl moiety was the most effective PAG. We also found that less than 100-m thick films were effectively cured by irradiation from the deep-UV LEDs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.